# Thrombocytopenia and platelet transfusions in ICU patients: an international inception cohort study
## (PLOT-ICU)

Carl Thomas Anthon, Frédéric Pène, Anders Perner, Elie Azoulay, Kathryn

Puxty, Andry van de Louw, Andreas Barratt-Due, Sanjay Chawla, Pedro

Castro, Pedro Póvoa, et al.

<figure><img src="image_1.png" /></figure>

► To cite this version:

Carl Thomas Anthon, Frédéric Pène, Anders Perner, Elie Azoulay, Kathryn Puxty, et al. Thrombocytopenia and platelet transfusions in ICU patients: an international inception cohort study (PLOT-ICU). Intensive Care Medicine, 2023, 49 (11), 10.1007/s00134-023-07225-2. http://onlinelibrary.wiley.com/doi/abs/10.1007/s00134-023-07225-2

HAL Id: hal-04840088

https://hal.science/hal-04840088v1

Submitted on 16 Dec 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_2.png" /></figure>
<figure><img src="image_3.png" /></figure>

# Thrombocytopenia and platelet transfusions in ICU patients: an international inception cohort study (PLOT-ICU)

Carl Thomas Anthon¹ ID, Frédéric Pène² ID, Anders Perner¹,³,⁴ ID, Elie Azoulay⁴ ID, Kathryn Puxty⁵ ID, Andry Van De Louw⁶, Andreas Barratt-Due⁷ ID, Sanjay Chawla⁸,⁹ ID, Pedro Castro¹⁰ ID, Pedro Póvoa¹¹,¹²,¹³ ID, Luis Coelho¹¹,¹² ID, Victoria Metaxa¹⁴ ID, Matthias Kochanek¹⁵ ID, Tobias Liebregts¹⁶, Thomas Kander¹⁷,¹⁸ ID, Johanna Hästbacka¹⁹,²⁰ ID, Jo Bønding Andreasen²¹ ID, Edwige Péju² ID, Lene Bjerregaard Nielsen²² ID, Christine Lodberg Hvas²³, Etienne Dufranc²⁴ ID, Emmanuel Canet²⁵ ID, Linda Lundqvist¹⁷, Christopher John Wright²⁶, Julien Schmidt²⁷ ID, Fabrice Uhel²⁸,²⁹ ID, Hafid Ait-Oufella³⁰ ID, Mette Krag³,³¹ ID, Elisabet Cos Badia³², Cándido Díaz-Lagares³³,³⁴ ID, Sophie Menat³⁵, Guillaume Voiriot³⁶ ID, Niels Erikstrup Clausen³⁷ ID, Kristian Lorentzen³⁸, Reidar Kvåle³⁹,⁴⁰ ID, Thomas Hildebrandt⁴¹ ID, Aleksander Rygh Holten⁴²,⁴³ ID, Kristian Strand⁴⁴ ID, Asterios Tzalavras¹⁶ ID, Morten Heiberg Bestle³,⁴⁵ ID, Pål Klepstad⁴⁶,⁴⁷ ID, Sara Fernandez⁴⁸ ID, Damien Vimpere⁴⁹, Carolina Paulino¹²,⁵⁰ ID, Carina Graça⁵¹ ID, Catherina Lueck⁵² ID, Christian Svendsen Juhl⁵³ ID, Carolina Costa⁵⁴, Per Martin Bådstøløkken⁵⁵, Teresa Miranda¹¹, Lia Susana Aires Lêdo⁵⁶ ID, Joao Carlos Sousa Torres⁵⁷ ID, Anders Granholm¹ ID, Morten Hylander Møller¹,³ ID and Lene Russell¹,³,⁴,⁵,⁸* ID on behalf of the PLOT-ICU Collaborators and the Nine-I Study Group

© 2023 The Author(s)

## Abstract

**Purpose:** Thrombocytopenia (platelet count < 150 x 10⁹/L) is common in intensive care unit (ICU) patients and is likely associated with worse outcomes. In this study we present international contemporary data on thrombocytopenia in ICU patients.

**Methods:** We conducted a prospective cohort study in adult ICU patients in 52 ICUs across 10 countries. We assessed frequencies of thrombocytopenia, use of platelet transfusions and clinical outcomes including mortality. We evaluated pre-selected potential risk factors for the development of thrombocytopenia during ICU stay and associations between thrombocytopenia at ICU admission and 90-day mortality using pre-specified logistic regression analyses.

**Results:** We analysed 1166 ICU patients; the median age was 63 years and 39.5% were female. Overall, 43.2% (95% confidence interval (CI) 40.4–46.1) had thrombocytopenia; 23.4% (20–26) had thrombocytopenia at ICU admission,

<footnote>*Correspondence: lene.russell@mail.dk</footnote>

<footnote n="58">⁵⁸ Department of Intensive Care, Copenhagen University Hospital - Gentofte, Hellerup, Denmark
Full author information is available at the end of the article</footnote>
and 19.8% (17.6–22.2) developed thrombocytopenia during their ICU stay. Non-AIDS-, non-cancer-related immune deficiency, liver failure, male sex, septic shock, and bleeding at ICU admission were associated with the development of thrombocytopenia during ICU stay. Among patients with thrombocytopenia, 22.6% received platelet transfusion(s), and 64.3% of in-ICU transfusions were prophylactic. Patients with thrombocytopenia had higher occurrences of bleeding and death, fewer days alive without the use of life-support, and fewer days alive and out of hospital. Thrombocytopenia at ICU admission was associated with 90-day mortality (adjusted odds ratio 1.7; 95% CI 1.19–2.42).

**Conclusion:** Thrombocytopenia occurred in 43% of critically ill patients and was associated with worse outcomes including increased mortality. Platelet transfusions were given to 23% of patients with thrombocytopenia and most were prophylactic.

**Keywords:** Thrombocytopenia, Platelet transfusion, Critical illness, Intensive care unit, Bleeding, Thrombosis

## Introduction

Thrombocytopenia, usually defined as a platelet count < 150 × 10⁹/L, occurs frequently in intensive care unit (ICU) patients [1, 2]. It is often multifactorial with causes including conditions and interventions resulting in reduced platelet production or increased platelet consumption, destruction, or sequestration, and haemodilution [3]. The prevalence and cumulative incidence have been reported in ranges from 8% to 77% and 8% to 56%, respectively, depending on case mix and definitions [4, 5]. Observational studies suggest that thrombocytopenia may impact ICU patients' short- and long-term outcomes, including increased bleeding, transfusion requirements, use of life-support, length of ICU- and hospital stay, and mortality [4, 5]. However, uncertainty exists as many studies have been single-centred with low external validity [1, 2, 6–9].

Thrombocytopenia may prompt ICU physicians to delay or withhold invasive procedures, reduce thrombosis prophylaxis and consider platelet transfusions [10]. Prophylactic platelet transfusions are frequently used in thrombocytopenic ICU patients to reduce the risk of bleeding [11, 12], but evidence from randomised trials in ICU settings is sparse [13, 14], limited to a recent study evaluating platelet transfusion before central venous catheter (CVC) placement [15].

We conducted an international, prospective, inception cohort study to provide contemporary epidemiological data describing the frequency of thrombocytopenia in ICU patients, its risk factors, current platelet transfusion practice, and clinical outcomes including mortality. We hypothesised that thrombocytopenia would be frequent and associated with worse outcomes and that specific risk factors for thrombocytopenia exist.

## Methods

### Study design and setting

This was an international, prospective, inception cohort study conducted and analysed in compliance with a

## Take-home message

In this study, two in five acutely admitted adult ICU patients had thrombocytopenia; half of those had thrombocytopenia at ICU admission, which was associated with increased mortality. Platelet transfusions were frequently used in patients with severe and very severe thrombocytopenia, and most transfusions were prophylactic.

published protocol and statistical analysis plan with minor modifications (electronic supplementary material (ESM) 1) [16]. The manuscript was prepared according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement [17] (ESM 2).

The study was performed in 52 ICUs across 10 countries in Europe and North America (ESM 3 and 4) and overseen by a steering committee (ESM 5). Study ICUs were invited to participate through the research network Caring for critically ill immunocompromised patients: Multinational Network (Nine-I).

The study was approved by the Danish Centre for Regional Development (R-21012287) and registered at the Capital Region's Centre for Data Compliance (P-2021-262). We obtained all necessary approvals in the other participating countries and collected informed consent from patients and/or surrogates if required.

Inception periods of 14 consecutive days were conveniently chosen by participating ICUs from May 2021 to July 2022. Included patients were followed for a maximum of 90 days.

## Population

During inception periods, all consecutive adults (≥ 18 years) who were acutely admitted to the ICU were screened for inclusion. Patients transferred from other ICUs were considered eligible if they otherwise met the inclusion criteria. We excluded patients with elective open-heart surgery during current hospitalisation and those who had previously been enrolled or declined informed consent.
**Data collection and management**

We developed an electronic case report form (eCRF) using the Research Electronic Data Capture (REDCap) tool hosted by the Capital Region of Denmark [18, 19]. The eCRF was pre-tested at the coordinating site and local investigators had access to a training version before study initiation.

For each study ICU, we collected data on type of hospital and ICU, number of ICU beds and presence of local guidelines for platelet transfusions (ESM 6).

Patient data were collected from medical records as described in the protocol [16]. Baseline data collected at ICU admission included demographics, comorbidities, selected treatments, Simplified Mortality Score for the Intensive Care Unit (SMS-ICU, an illness severity score ranging from 0 to 42 points with higher scores indicating higher predicted 90-day mortality) (ESM 7) [20, 21], platelet count, and presence of bleeding (ESM 8).

Daily data were collected during ICU stay and resumed upon readmission or transfer to another study ICU for a maximum of 90 days. We collected data on the use of life-support [vasopressor/inotropes, mechanical ventilation, renal replacement therapy, extracorporeal membrane oxygenation (ECMO)], selected treatments, platelet counts, bleeding events, thrombotic events, and transfusions (ESM 9). For platelet transfusions used within ICU departments, we collected data on indications for transfusion (pre-procedural: covering invasive procedures or surgery; prophylactic: reducing the risk of bleeding; therapeutic: treating bleeding) and platelet count before transfusion (ESM 1 and 9). On day 90, we assessed the vital status and number of days in the hospital (ESM 10).

**Definitions and classifications**

**Thrombocytopenia**

We defined thrombocytopenia as a platelet count < 150 × 10⁹/L and classified thrombocytopenia into three categories: 'baseline thrombocytopenia' defined as patients with thrombocytopenia at ICU admission, 'ICU thrombocytopenia' defined as patients with thrombocytopenia during ICU stay without thrombocytopenia at ICU admission and 'any thrombocytopenia' defined as patients who had thrombocytopenia at ICU admission and/or during ICU stay. Severity of thrombocytopenia was classified as mild (100–149 × 10⁹/L), moderate (50–99 × 10⁹/L), severe (20–49 × 10⁹/L), and very severe (<20 × 10⁹/L), based on the platelet count at ICU admission and the nadir platelet count during ICU stay and overall, for baseline-, ICU-, and any thrombocytopenia, respectively [16].

**Bleeding**

We defined and graded bleeding according to a modified World Health Organization (WHO) classification

[22–25]. Grade 1 and 2 covers bleedings that do not require red blood cell (RBC) transfusion. Grade 3 covers bleedings requiring up to two RBC transfusions and central nervous system bleedings without symptoms. Grade 4 covers bleedings requiring either (1) more than two RBC transfusions, (2) intubation and mechanical ventilation or (3) surgical intervention, and bleedings from critical sites with symptoms and fatal bleedings (ESM 11) [16].

**Outcomes**

The primary outcome was the number of patients with any thrombocytopenia. Secondary outcomes were numbers of patients with mild, moderate, severe, and very severe thrombocytopenia; 90-day mortality; days alive without use of life-support; days alive and out of hospital; numbers of patients with at least one bleeding event, at least one thrombotic event, and at least one platelet transfusion during ICU stay; number of platelet transfusions and volumes transfused per patient; and number of transfusions for each indication (ESM 12) [16].

**Process variables**

Process variables included daily platelet count before ICU platelet transfusions for each indication and number of RBC transfusions (ESM 1 and 12).

**Statistical methods**

**Sample size**

As we planned to include patients regardless of illness severity and expected length of ICU stay, we made a conservative assumption, that the frequency of any thrombocytopenia would be 20% [4, 5]. We aimed to enroll a minimum of 1,000 patients to determine the frequency with a 95% confidence interval (CI) of 18–23% [16].

**Descriptive data**

Analyses were performed using R (version 4.2.0) following the statistical analysis plan with minor modifications (ESM 1) [16]. Categorical variables were reported as numbers and percentages and continuous variables as medians with interquartile ranges (IQRs). Primary and secondary outcomes were reported descriptively with 95% CIs calculated using the Clopper–Pearson method for categorical variables and non-parametric percentile-based bootstrapping with 100,000 samples for continuous variables. Results were stratified on the three categories of thrombocytopenia, and for the secondary outcomes, also on the severity of thrombocytopenia [16].

**Regression analyses**

We used pre-specified logistic regression models [16] to assess a set of potential baseline risk factors for ICU
thrombocytopenia (<150 × 10⁹/L and <50 × 10⁹/L) selected a priori based on literature review [4, 5], clinical knowledge, and the expected number of events. We assessed sex, haematological malignancy, immune deficiency, acute or chronic liver failure, SMS-ICU, bleeding and septic shock in unadjusted models and in a model adjusted for all selected risk factors [16]. We modified the planned definition of 'immune deficiency' to, 'non-acquired immune deficiency syndrome (AIDS)-, non-cancer-related immune deficiency' to avoid any unintended overlap with cancer patients (ESM 1). Patients with baseline thrombocytopenia <150 × 10⁹/L were excluded from these analyses.

We assessed associations between baseline thrombocytopenia (<150 × 10⁹/L and <50 × 10⁹/L) and 90-day mortality in pre-specified logistic regression models adjusted for potential confounders including sex, country, haematological malignancy, SMS-ICU, and septic shock selected based on literature review [4, 5], clinical knowledge and expected number of events.

We used Nagelkerke's R² [26] and calibration plots [27] to assess model fits (ESM 24). We conducted additional sensitivity analyses including complete case analyses and Cox proportional hazards regressions to assess the impact of missing platelet counts and time-to-event and competing risks, respectively (details in ESM 25 and 27).

## Missing data

We handled missing platelet count data, as planned, using logical imputation, and assumed that missing baseline platelet counts were equal to the first platelet count in ICU (ESM 13). Twenty-eight patients were transferred directly from a study ICU to a non-study ICU where daily variables (clinical events, biochemistry, etc.) could not be obtained. We assumed that no events occurred during days spent in non-study ICUs. Following these logical imputations, we performed complete case analysis due to limited remaining missing data (<5% of patients) [16].

## Results

We included 1168 ICU patients from 52 ICUs across 43 centres in 10 countries. Two patients withdrew consent and were excluded (ESM 14). Most study ICUs were mixed ICUs (76.9%) in university hospitals (94.2%). Few (15.4%) had ICU-specific guidelines for platelet transfusions (ESM 15).

## Baseline characteristics

Patients with thrombocytopenia were more often males, admitted from hospital wards, and were more severely ill than those without thrombocytopenia (Table 1 and ESM 16). More patients with thrombocytopenia had haematological malignancy, non-AIDS-, non-cancer-related

immune deficiencies, acute and chronic liver failure, septic shock, and bleeding at baseline and more received treatment with haematopoietic stem cell transplantation, chemotherapy and platelet transfusions compared to those without thrombocytopenia.

Common characteristics in patients with baseline thrombocytopenia, were admission from hospital wards, haematological malignancy, and treatment with haematopoietic stem cell transplantation, chemotherapy, and platelet transfusions prior to ICU admission while surgery before ICU admission and admission from emergency settings, operating or recovery rooms were more common in patients with ICU thrombocytopenia.

## Primary outcome

The frequency of any thrombocytopenia was 43.2% (95% CI 40.4–46.1); 23.4% (21–26) had baseline thrombocytopenia, and an additional 19.8% (17.6–22.2) developed ICU thrombocytopenia.

## Secondary outcomes

ICU thrombocytopenia occurred on median (IQR) day 2 (1–3) with few occurrences after day 5 (10.8%) from ICU admission (ESM 17) and most patients with baseline thrombocytopenia also had thrombocytopenia during ICU stay (95.6%). Among patients with any thrombocytopenia, 42.5% (95% CI 38.1–46.9) had mild-, 31% (26.9–35.2) moderate-, 12.9% (10.1–16.1) severe- and 13.7% (10.8–17) very severe thrombocytopenia (ESM 18) with nadir platelet counts occurring on median (interquartile range, IQR) 3 (1–4) days from ICU admission. Nadir platelet counts for patients with baseline- and ICU thrombocytopenia occurred on median (IQR) days 2 (0–4) and 4 (2–5) from ICU admission, respectively (day 0 representing baseline). The trajectories of thrombocytopenia from baseline through ICU stay are presented in Fig. 1 and ESM 19.

The overall 90-day mortality was 25.9% (95% CI 23.4–28.5) (ESM 20) and differed between patients with- and without thrombocytopenia at 34.6% and 19.3%, respectively. The highest mortality was observed in patients with severe- and very severe thrombocytopenia (Table 2).

Overall, the median number of days alive without use of life-support was 87 (IQR 0–90) and days alive and out of hospital was 63 (0–79). Patients with thrombocytopenia had fewer days alive without use of life-support and fewer days alive out of hospital than those without thrombocytopenia (Table 2). More patients with thrombocytopenia received vasopressors (73% vs 45.8%), invasive mechanical ventilation (63.3% vs 44.6%), RRT (25% vs 5.3%) and ECMO (2.8% vs 0.6%) compared with those without thrombocytopenia (ESM 21).
<table><caption>Table 1 Baseline characteristics</caption><thead><tr><th rowspan="2"></th><th rowspan="2">All<br>(n = 1166)</th><th colspan="4">Thrombocytopenia</th></tr><tr><th>None<br>(n = 662)</th><th>Any<sup>a</sup><br>(n = 504)</th><th>Baseline<sup>b</sup><br>(n = 273)</th><th>ICU<sup>c</sup><br>(n = 231)</th></tr></thead><tbody><tr><td>Age (years)</td><td>63 (49–73)</td><td>64 (47–74)</td><td>63 (51–72)</td><td>61 (50–70)</td><td>65 (53–74)</td></tr><tr><td>Female sex</td><td>461 (39.5%)</td><td>291 (44%)</td><td>170 (33.7%)</td><td>90 (33%)</td><td>80 (34.6%)</td></tr><tr><td><strong>Comorbidities</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Pulmonary disease</td><td>217 (18.6%)</td><td>153 (23.1%)</td><td>64 (12.7%)</td><td>34 (12.5%)</td><td>30 (13%)</td></tr><tr><td>IHD or HF</td><td>208 (17.8%)</td><td>126 (19%)</td><td>82 (16.3%)</td><td>44 (16.1%)</td><td>38 (16.5%)</td></tr><tr><td>Chronic renal failure</td><td>100 (8.6%)</td><td>46 (6.9%)</td><td>54 (10.7%)</td><td>29 (10.6%)</td><td>25 (10.8%)</td></tr><tr><td>Chronic liver failure</td><td>62 (5.3%)</td><td>12 (1.8%)</td><td>50 (9.9%)</td><td>38 (13.9%)</td><td>12 (5.2%)</td></tr><tr><td>Solid tumour cancer</td><td>162 (13.9%)</td><td>89 (13.4%)</td><td>73 (14.5%)</td><td>45 (16.5%)</td><td>28 (12.1%)</td></tr><tr><td>Metastatic cancer</td><td>76 (6.5%)</td><td>39 (5.9%)</td><td>37 (7.3%)</td><td>27 (9.9%)</td><td>10 (4.3%)</td></tr><tr><td>Haematological malignancy</td><td>92 (7.9%)</td><td>17 (2.6%)</td><td>75 (14.9%)</td><td>66 (24.2%)</td><td>9 (3.9%)</td></tr><tr><td>Non-AIDS-, non-cancer-related immune deficiency<sup>d</sup></td><td>61 (5.2%)</td><td>19 (2.9%)</td><td>42 (8.3%)</td><td>23 (8.4%)</td><td>19 (8.2%)</td></tr><tr><td>Coagulation disorder</td><td>7 (0.6%)</td><td>4 (0.6%)</td><td>3 (0.6%)</td><td>1 (0.4%)</td><td>2 (0.9%)</td></tr><tr><td>Previous thrombo-embolism</td><td>150 (12.9%)</td><td>89 (13.4%)</td><td>61 (12.1%)</td><td>35 (12.8%)</td><td>26 (11.3%)</td></tr><tr><td><strong>Admitted from</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>ED</td><td>571 (49%)</td><td>360 (54.4%)</td><td>211 (41.9%)</td><td>93 (34.1%)</td><td>118 (51.1%)</td></tr><tr><td>Ward</td><td>340 (29.2%)</td><td>170 (25.7%)</td><td>170 (33.7%)</td><td>120 (44%)</td><td>50 (21.6%)</td></tr><tr><td>OR</td><td>172 (14.8%)</td><td>95 (14.4%)</td><td>77 (15.3%)</td><td>32 (11.7%)</td><td>45 (19.5%)</td></tr><tr><td>ICU</td><td>83 (7.1%)</td><td>37 (5.6%)</td><td>46 (9.1%)</td><td>28 (10.3%)</td><td>18 (7.8%)</td></tr><tr><td><strong>Surgery</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Elective surgery</td><td>102 (8.7%)</td><td>57 (8.6%)</td><td>45 (8.9%)</td><td>21 (7.7%)</td><td>24 (10.4%)</td></tr><tr><td>Acute surgery</td><td>219 (18.8%)</td><td>115 (17.4%)</td><td>104 (20.6%)</td><td>47 (17.2%)</td><td>57 (24.7%)</td></tr><tr><td><strong>Illness severity</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>SMS-ICU predicted 90-day mortality (%)<sup>e</sup></td><td>22.8 (14.7–40.1)</td><td>20.5 (13.1–33.8)</td><td>30.8 (16.5–43.4)</td><td>30.8 (16.5–46.7)</td><td>28 (17.4–43.4)</td></tr><tr><td><strong>Primary reason for ICU admission</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Neurological</td><td>175 (15%)</td><td>108 (16.3%)</td><td>67 (13.3%)</td><td>33 (12.1%)</td><td>34 (14.7%)</td></tr><tr><td>Respiratory</td><td>406 (34.8%)</td><td>277 (41.8%)</td><td>129 (25.6%)</td><td>76 (27.8%)</td><td>53 (22.9%)</td></tr><tr><td>Circulatory</td><td>278 (23.8%)</td><td>125 (18.9%)</td><td>153 (30.4%)</td><td>78 (28.6%)</td><td>75 (32.5%)</td></tr><tr><td>Renal</td><td>35 (3%)</td><td>13 (2%)</td><td>22 (4.4%)</td><td>13 (4.8%)</td><td>9 (3.9%)</td></tr><tr><td>Liver</td><td>13 (1.1%)</td><td>1 (0.2%)</td><td>12 (2.4%)</td><td>8 (2.9%)</td><td>4 (1.7%)</td></tr><tr><td>Metabolic</td><td>55 (4.7%)</td><td>32 (4.8%)</td><td>23 (4.6%)</td><td>13 (4.8%)</td><td>10 (4.3%)</td></tr><tr><td>Multiple trauma</td><td>29 (2.5%)</td><td>12 (1.8%)</td><td>17 (3.4%)</td><td>4 (1.5%)</td><td>13 (5.6%)</td></tr><tr><td>TBI</td><td>13 (1.1%)</td><td>8 (1.2%)</td><td>5 (1%)</td><td>3 (1.1%)</td><td>2 (0.9%)</td></tr><tr><td>Burn</td><td>3 (0.3%)</td><td>2 (0.3%)</td><td>1 (0.2%)</td><td>1 (0.4%)</td><td>0 (0%)</td></tr><tr><td>Haemorrhage</td><td>48 (4.1%)</td><td>12 (1.8%)</td><td>36 (7.1%)</td><td>19 (7%)</td><td>17 (7.4%)</td></tr><tr><td>Other</td><td>111 (9.5%)</td><td>72 (10.9%)</td><td>39 (7.7%)</td><td>25 (9.2%)</td><td>14 (6.1%)</td></tr><tr><td><strong>Acute conditions</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Sepsis</td><td>161 (13.8%)</td><td>88 (13.3%)</td><td>73 (14.5%)</td><td>52 (19%)</td><td>21 (9.1%)</td></tr><tr><td>Septic shock</td><td>174 (14.9%)</td><td>58 (8.8%)</td><td>116 (23%)</td><td>62 (22.7%)</td><td>54 (23.4%)</td></tr><tr><td>Acute liver failure</td><td>42 (3.6%)</td><td>8 (1.2%)</td><td>34 (6.7%)</td><td>18 (6.6%)</td><td>16 (6.9%)</td></tr><tr><td>COVID-19</td><td>140 (12%)</td><td>82 (12.4%)</td><td>58 (11.5%)</td><td>40 (14.7%)</td><td>18 (7.8%)</td></tr><tr><td><strong>Treatments</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>HSCT<sup>f</sup></td><td>28 (2.4%)</td><td>0 (0%)</td><td>28 (5.6%)</td><td>27 (9.9%)</td><td>1 (0.4%)</td></tr><tr><td>Chemotherapy<sup>g</sup></td><td>86 (7.4%)</td><td>27 (4.1%)</td><td>59 (11.7%)</td><td>51 (18.7%)</td><td>8 (3.5%)</td></tr><tr><td>Anticoagulating treatment<sup>h</sup></td><td>399 (34.2%)</td><td>232 (35%)</td><td>167 (33.1%)</td><td>95 (34.8%)</td><td>72 (31.2%)</td></tr><tr><td>Platelet inhibitors<sup>i</sup></td><td>198 (17%)</td><td>132 (19.9%)</td><td>66 (13.1%)</td><td>31 (11.4%)</td><td>35 (15.2%)</td></tr><tr><td><strong>Biochemistry</strong></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Platelet count<sup>j</sup></td><td>222 (150.5–300)</td><td>278 (225–341.2)</td><td>146 (93–198)</td><td>97 (50–125)</td><td>204 (175.2–258.8)</td></tr></tbody></table>
<table><caption>Table 1 (continued)</caption><thead><tr><th rowspan="2"></th><th rowspan="2">All<br>(n=1166)</th><th colspan="4">Thrombocytopenia</th></tr><tr><th>None<br>(n=662)</th><th>Any<sup>a</sup><br>(n=504)</th><th>Baseline<sup>b</sup><br>(n=273)</th><th>ICU<sup>c</sup><br>(n=231)</th></tr></thead><tbody><tr><td colspan="6"><strong>Bleeding and transfusions 24 h before ICU admission</strong></td></tr><tr><td>Bleeding</td><td>162 (13.9%)</td><td>66 (10%)</td><td>96 (19%)</td><td>50 (18.3%)</td><td>46 (19.9%)</td></tr><tr><td>Platelet transfusion</td><td>59 (5.1%)</td><td>9 (1.4%)</td><td>50 (9.9%)</td><td>35 (12.8%)</td><td>15 (6.5%)</td></tr></tbody></table>

Continuous variables are presented as medians (IQR) and categorical variables as numbers and percentages. Definitions of baseline variables are available in ESM 7 and 8. Additional baseline characteristics are provided in ESM 16

ICU intensive care unit; IHD ischaemic heart disease; HF heart failure; ED emergency department; OR operating room or recovery room; TBI traumatic brain injury; COVID-19 coronavirus disease 2019; HSCT haematopoietic stem cell transplantation; AIDS acquired immune deficiency syndrome; SMS-ICU Simplified Mortality Score for the Intensive Care Unit

a Patients with a platelet count < 150 × 10⁹/L at ICU admission and/or during ICU stay

b Patients with a platelet count < 150 × 10⁹/L at ICU admission

c Patients with a platelet count < 150 × 10⁹/L during ICU stay without thrombocytopenia at ICU admission

d Non-AIDS-, non-cancer-related immune deficiencies including solid organ transplant or conditions requiring long-term (> 30 days) or high-dose (> 1 mg/kg/day) steroids, or any immunosuppressive drug for more than 30 days

e Predicted 90-day mortality based on SMS-ICU (an illness severity score ranging from 0–42 with corresponding predicted 90-day mortality of 3.3–91.0% [20, 21]). The corresponding median (IQR) raw scores were 16.0 (12.0–22.0), 15.0 (11.0–20.0), 19.0 (13.0–23.0), 19.0 (13.0–24.0) and 18.0 (13.5–23.0) in all patients, patients without-, patients with-, patients with baseline- and patients with ICU thrombocytopenia, respectively. Details on SMS-ICU are provided in ESM 7

f HSCT (allogenic or autologous) within one year before ICU admission

g Chemotherapy treatment within six weeks before ICU admission

h Including treatment with anticoagulating drugs in any prophylaxis and therapeutic dose within 48 h before ICU admission

i Treatment with platelet inhibitors within 48 h before ICU admission

j Baseline platelet counts were unavailable for 195 (16.7%) patients

In total, 16% of patients bled in ICU (95% CI 14–18.3) (ESM 20). Among patients without thrombocytopenia, 7.3% bled in ICU, most of whom (81.2%) had bleeding of grade 1 or 2. In contrast, 27.6% of patients with thrombocytopenia bled in ICU, of whom 57.6% had bleeding of grade 3 or 4. Proportionally more patients with severe- and very severe thrombocytopenia had grade 3 or 4 bleeding compared to patients with no- or less severe thrombocytopenia (Table 2). Thrombotic events occurred in 5.8% (95% CI 4.6–7.3) of all patients (Table 2 and ESM 20).

Platelet transfusions were almost exclusively used in patients with thrombocytopenia, of whom 22.6% (95% CI 19–26.5%) were transfused (Table 2 and ESM 20). Patients transfused with platelets received median (IQR) 3 (1–5) platelet transfusions. Most platelet transfusions (90.9%) took place within ICU departments (in-ICU) and fewer in operating theatres (9.1%) (EMS 22). The number of in-ICU transfusions increased with higher severity of thrombocytopenia (Fig. 2) and most in-ICU transfusions were prophylactic (64.3%) followed by therapeutic- (27.6%) and pre-procedural transfusions (8.1%) with median platelet counts before transfusion of 15 × 10⁹/L (IQR 9–26), 40 × 10⁹/L (23–76) and 31 × 10⁹/L (20–54), respectively. Platelet counts before transfusion

for specific procedures are presented in ESM 23. More patients with thrombocytopenia received RBC transfusion than patients without thrombocytopenia (Table 2 and ESM 20).

## Risk factors for ICU thrombocytopenia

In unadjusted and adjusted analyses, male sex, non-AIDS-, non-cancer-related immune deficiency, acute or chronic liver failure, higher illness severity [20, 21], bleeding, and septic shock at baseline were associated with ICU thrombocytopenia < 150 × 10⁹/L. Meaningful interpretation of risk factors for ICU thrombocytopenia < 50 × 10⁹/L were hampered by few events (n=26) (Table 3). Results were largely consistent in sensitivity analyses (ESM 25).

## Baseline thrombocytopenia and mortality

When adjusting for country, sex, haematological malignancy, SMS-ICU and septic shock, baseline thrombocytopenia < 150 × 10⁹/L was associated with increased 90-day mortality (OR 1.7, 95% CI 1.19–2.42), while some uncertainty remained about the effect of baseline thrombocytopenia < 50 × 10⁹/L (1.79, 95% CI 0.89–3.61) (ESM 26). Sensitivity analyses yielded largely consistent results (ESM 27).
<figure><img src="image_4.png" /><figcaption>**Fig. 1** The trajectories of thrombocytopenia. Trajectories of thrombocytopenia in all patients (A) and exclusively in those who had thrombocytopenia (B). The severity of baseline- and ICU thrombocytopenia was based on the platelet count at baseline and the nadir platelet during ICU stay, respectively. The flows are coloured according to the baseline severity. Patients whose thrombocytopenia remained unchanged (i.e., unchanged severity) from baseline throughout their ICU stay are represented by flows moving between identical colours. Patients whose thrombocytopenia got better or worse (i.e., decreased or increased severity) during their ICU stay compared to their starting point at baseline are represented by flows moving between different colours. Only 22 patients had less severe thrombocytopenia during their ICU stay compared to their starting point at baseline (represented by flows moving from "warmer" to "colder" colour tones)</figcaption></figure>

Discussion

In this international prospective cohort study of acutely
admitted adult ICU patients, we found that 43% had
thrombocytopenia; 23% at ICU admission and 20%
developed it during ICU stay. Patients with throm-
bocytopenia had worse outcomes, including 90-day
mortality, and several conditions increased the risk
of developing thrombocytopenia during ICU stay.
Twenty-three percent of patients with thrombocyto-
penia received platelet transfusion and most in-ICU
transfusions were prophylactic.

The observed frequency of thrombocytopenia was
similar to findings in smaller cohort studies in general
mixed ICU populations [2, 28], and in a larger cohort of
ICU patients receiving thromboprophylaxis [29]. How-
ever, variation exists, which is likely due to differences in
case mix, illness severity, follow-up time and definitions
of thrombocytopenia [1, 9, 30, 31].

We found that male sex, non-AIDS-, non-cancer-
related immune deficiency, acute or chronic liver fail-
ure, higher illness severity, bleeding, and septic shock
at baseline increased the risk of developing ICU throm-
bocytopenia. This aligns well with previously published
data [29, 30, 32], although one study using a different
definition of thrombocytopenia (<100 x 10⁹/L) found

female sex to be associated with the development of
ICU thrombocytopenia [30]. Comparing risk factors
across studies is challenging as case mix, definitions of
thrombocytopenia and analytic methods differ [29, 30,
32].

Consistent with previous studies [4, 5, 29, 30], we
observed that patients with thrombocytopenia had
worse outcomes, including higher rates of bleeding,
transfusion and mortality, fewer days alive without
use of life-support and days alive and out of hospital.
Associations between thrombocytopenia and bleeding,
transfusion, and mortality followed a "dose-response"
pattern with worse outcomes accompanying more
severe thrombocytopenia. Patients with severe- and
very severe thrombocytopenia had markedly higher
mortality but were also more likely to experience grade
3 or 4 bleeding and to receive transfusions compared
with patients with no- or less severe thrombocytope-
nia. In this heterogeneous ICU population, it remains
unclear whether the observed excess mortality is
directly related to thrombocytopenia and its conse-
quences, such as bleeding and transfusions, or whether
thrombocytopenia merely represents a marker of ill-
ness severity or the pathophysiology of the underly-
ing disease. Importantly, identified risk factors and
<table><caption>Table 2 Secondary clinical outcomes</caption><thead><tr><th></th><th colspan="7">Thrombocytopenia</th></tr><tr><th></th><th>None<br>(n = 662)</th><th>Any<sup>a</sup><br>(n = 504)</th><th>Mild<br>(n = 214)</th><th>Moderate<br>(n = 156)</th><th>Severe<br>(n = 65)</th><th>Very severe<br>(n = 69)</th><th>Baseline<sup>b</sup><br>(n = 273)</th><th>ICU<sup>c</sup><br>(n = 231)</th></tr></thead><tbody><tr><td><strong>Outcomes</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>90-day mortality<sup>d</sup></td><td>127 (19.3%)</td><td>174 (34.6%)</td><td>56 (26.3%)</td><td>49 (31.4%)</td><td>33 (50.8%)</td><td>36 (52.2%)</td><td>102 (37.4%)</td><td>72 (31.3%)</td></tr><tr><td>Days alive without life-support<sup>e</sup></td><td>88 (79.5-90)</td><td>82 (0-88)</td><td>86 (0-89)</td><td>83 (0-88)</td><td>0 (0-87)</td><td>0 (0-85)</td><td>81 (0-89)</td><td>83 (0-88)</td></tr><tr><td>Days alive and out of hospital<sup>f</sup></td><td>71 (20-81)</td><td>44 (0-75)</td><td>63 (0-78)</td><td>47 (0-73)</td><td>0 (0-60)</td><td>0 (0-31)</td><td>30 (0-74)</td><td>50.5 (0-75)</td></tr><tr><td>Any bleeding in the ICU<sup>g</sup></td><td>48 (7.3%)</td><td>139 (27.6%)</td><td>39 (18.2%)</td><td>44 (28.2%)</td><td>24 (36.9%)</td><td>32 (46.4%)</td><td>75 (27.5%)</td><td>64 (27.7%)</td></tr><tr><td><strong>Worst bleeding in the ICU<sup>h</sup></strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Grade 1</td><td>5 (0.8%)</td><td>10 (2%)</td><td>2 (0.9%)</td><td>2 (1.3%)</td><td>3 (4.6%)</td><td>3 (4.3%)</td><td>3 (1.1%)</td><td>7 (3%)</td></tr><tr><td>Grade 2</td><td>34 (5.1%)</td><td>49 (9.7%)</td><td>15 (7%)</td><td>17 (10.9%)</td><td>6 (9.2%)</td><td>11 (15.9%)</td><td>29 (10.6%)</td><td>20 (8.7%)</td></tr><tr><td>Grade 3</td><td>5 (0.8%)</td><td>37 (7.3%)</td><td>11 (5.1%)</td><td>11 (7.1%)</td><td>6 (9.2%)</td><td>9 (13%)</td><td>20 (7.3%)</td><td>17 (7.4%)</td></tr><tr><td>Grade 4</td><td>4 (0.6%)</td><td>43 (8.5%)</td><td>11 (5.1%)</td><td>14 (9%)</td><td>9 (13.8%)</td><td>9 (13%)</td><td>23 (8.4%)</td><td>20 (8.7%)</td></tr><tr><td>New thrombosis in the ICU</td><td>30 (4.5%)</td><td>38 (7.5%)</td><td>15 (7%)</td><td>16 (10.3%)</td><td>4 (6.2%)</td><td>3 (4.3%)</td><td>19 (7%)</td><td>19 (8.2%)</td></tr><tr><td><strong>Platelet transfusions</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Transfused with platelets<sup>i</sup></td><td>6 (0.9%)</td><td>114 (22.6%)</td><td>8 (3.7%)</td><td>19 (12.2%)</td><td>29 (44.6%)</td><td>58 (84.1%)</td><td>80 (29.3%)</td><td>34 (14.7%)</td></tr><tr><td>Number of platelet transfusions per patient<sup>j</sup></td><td>0 (0-0)</td><td>0 (0-0)</td><td>0 (0-0)</td><td>0 (0-0)</td><td>0 (0-2)</td><td>4 (1-7)</td><td>0 (0-1)</td><td>0 (0-0)</td></tr><tr><td>Total volume (mL) of platelets transfusions per patient<sup>k</sup></td><td>0 (0-0)</td><td>0 (0-0)</td><td>0 (0-0)</td><td>0 (0-0)</td><td>0 (0-326.2)</td><td>900 (283-1520)</td><td>0 (0-283)</td><td>0 (0-0)</td></tr><tr><td><strong>Indications for in-ICU transfusions<sup>l</sup></strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Prophylaxis</td><td>1 (0.2%)</td><td>73 (14.5%)</td><td>2 (0.9%)</td><td>4 (2.6%)</td><td>16 (24.6%)</td><td>51 (73.9%)</td><td>61 (22.3%)</td><td>12 (5.2%)</td></tr><tr><td>Pre-procedural</td><td>1 (0.2%)</td><td>29 (5.8%)</td><td>1 (0.5%)</td><td>2 (1.3%)</td><td>10 (15.4%)</td><td>16 (23.2%)</td><td>21 (7.7%)</td><td>8 (3.5%)</td></tr><tr><td>Therapeutic</td><td>1 (0.2%)</td><td>39 (7.7%)</td><td>2 (0.9%)</td><td>9 (5.8%)</td><td>12 (18.5%)</td><td>16 (23.2%)</td><td>22 (8.1%)</td><td>17 (7.4%)</td></tr><tr><td><strong>RBC transfusions</strong></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Transfused with RBCs</td><td>90 (13.6%)</td><td>217 (43.1%)</td><td>61 (28.5%)</td><td>69 (44.2%)</td><td>41 (63.1%)</td><td>46 (66.7%)</td><td>116 (42.5%)</td><td>101 (43.7%)</td></tr><tr><td>Number of RBC transfusions per patient</td><td>0 (0-0)</td><td>0 (0-3)</td><td>0 (0-1)</td><td>0 (0-3)</td><td>1 (0-4)</td><td>2 (0-6)</td><td>0 (0-2)</td><td>0 (0-3)</td></tr></tbody></table>

Continuous variables are presented as medians with IQRs and categorical variables as numbers and percentages. The severity of thrombocytopenia was based on the overall nadir platelet count; mild (100-149 × 10⁹/L), moderate (50-99 × 10⁹/L), severe (20-49 × 10⁹/L), and very severe (< 20 × 10⁹/L). We have presented 95% confidence intervals for the estimates in ESM 20

ICU intensive care unit; RBC red blood cell; WHO World Health Organization

<footnote>a Patients with a platelet count < 150 × 10⁹/L at ICU admission and/or during the ICU stay and within the specified severity subclasses according to the overall nadir platelet count</footnote>

<footnote>b Patients with a platelet count < 150 × 10⁹/L at ICU admission</footnote>

<footnote>c Patients with a platelet count < 150 × 10⁹/L during ICU stay without thrombocytopenia at ICU admission</footnote>

<footnote>d Four patients (0.3%) had missing 90-day mortality data</footnote>

<footnote>e Dead patients were assigned zero days alive without life-support. Four patients (0.3%) had missing data for this outcome</footnote>

<footnote>f Dead patients were assigned zero days alive and out of hospital. Four patients (0.3%) had missing data for this outcome</footnote>

<footnote>g Number of patients with at least one WHO bleeding in the ICU. We did not register bleedings occurring during surgery only while admitted to the ICU. Overall, 29 patients with no registered bleeding in the ICU were transfused with 2 or more packed red blood cells during surgery: 11 patients without thrombocytopenia and 18 patients with any thrombocytopenia (6 patients with mild-, 8 patients with moderate-, 3 patients with severe-, 1 patient with very severe thrombocytopenia, respectively). Of those, 8 patients with baseline thrombocytopenia and 10 with ICU thrombocytopenia, respectively</footnote>

<footnote>h Number of patients with at least one WHO bleeding in the ICU graded into 1 to 4 according to the worst graded bleeding episode</footnote>

<footnote>i Number of patients receiving at least one platelet transfusion</footnote>

<footnote>j Total number of transfusions per patient</footnote>

<footnote>k Total volume of platelet transfusions per patient. Two patients (0.2%) had missing data</footnote>

<footnote>l Number of patients that received at least one platelet transfusion that took place in ICU departments for each of the indications. Transfusions administered in operating theatres were excluded as we did not collect data on indications for platelet transfusions administered "outside" the ICU. In total 29 patients received 57 platelet transfusions during surgery: 3 patients without thrombocytopenia received 4 transfusions and 26 patients with thrombocytopenia received 53 transfusions (5 patients with mild thrombocytopenia received 14 transfusions, 7 patients with moderate thrombocytopenia received 12 transfusions, 6 patients with severe thrombocytopenia received 14 transfusions, and 8 patients with very severe thrombocytopenia received 13 transfusions). Of those, 11 patients with baseline thrombocytopenia received 17 transfusions and 15 patients with ICU thrombocytopenia received 36 transfusions</footnote>
<table><caption>Table 3 Baseline risk factors for ICU thrombocytopenia</caption><thead><tr><th rowspan="2"></th><th colspan="2">ICU thrombocytopenia &lt; 150 x 10<sup>9</sup>/L<sup>a</sup><br>OR (95% CI)</th><th colspan="2">ICU thrombocytopenia &lt; 50 x 10<sup>9</sup>/L<sup>b</sup><br>OR (95% CI)</th></tr><tr><th>Unadjusted</th><th>Adjusted<sup>c</sup></th><th>Unadjusted</th><th>Adjusted<sup>c</sup></th></tr></thead><tbody><tr><td>Male sex</td><td>1.48 (1.08-2.02)</td><td>1.45 (1.04-2.02)</td><td>0.82 (0.38-1.80)</td><td>0.80 (0.35-1.84)</td></tr><tr><td>SMS-ICU<sup>d</sup></td><td>1.07 (1.05-1.10)</td><td>1.06 (1.03-1.09)</td><td>1.10 (1.04-1.17)</td><td>1.06 (0.98-1.13)</td></tr><tr><td>Bleeding<sup>e</sup></td><td>2.25 (1.49-3.39)</td><td>2.27 (1.46-3.52)</td><td>0.91 (0.27-3.07)</td><td>1.12 (0.31-4.03)</td></tr><tr><td>Haematological malignancy</td><td>1.54 (0.68-3.50)</td><td>1.18 (0.49-2.85)</td><td>2.93 (0.65-13.10)</td><td>3.81 (0.73-19.79)</td></tr><tr><td>Non-AIDS-, non-cancer-related immune<br>deficiency<sup>f</sup></td><td>3.03 (1.58-5.84)</td><td>4.08 (2.05-8.15)</td><td>6.02 (2.14-16.95)</td><td>7.48 (2.36-23.70)</td></tr><tr><td>Liver failure</td><td>4.60 (2.44-8.70)</td><td>4.03 (2.06-7.88)</td><td>2.77 (0.80-9.62)</td><td>2.51 (0.66-9.59)</td></tr><tr><td>Septic shock</td><td>3.18 (2.12-4.77)</td><td>2.47 (1.58-3.85)</td><td>9.15 (4.12-20.36)</td><td>6.90 (2.82-16.89)</td></tr></tbody></table>

Baseline risk factors for ICU thrombocytopenia in patients without baseline thrombocytopenia (n = 893). Few patients (n = 26) developed severe thrombocytopenia (&lt; 50 x 10⁹/L) during ICU stay

ICU intensive care unit; CI confidence interval; OR odds ratio; WHO World Health Organization; SMS-ICU Simplified Mortality Score for the Intensive Care Unit; AIDS acquired immune deficiency syndrome

a Patients with a platelet count &lt; 150 x 10⁹/L during ICU stay without thrombocytopenia at ICU admission

b Patients with a platelet count &lt; 50 x 10⁹/L during ICU stay without thrombocytopenia at ICU admission

c Adjusted for the following baseline variables: male sex, SMS-ICU, bleeding, haematological malignancy, non-AIDS-, non-cancer-related immune deficiency, liver failure (acute or chronic) and septic shock

d OR for a one-point increase in SMS-ICU; an illness severity score ranging from 0-42 points with higher scores indicating higher predicted 90-day mortality

e Any WHO bleeding at baseline

f Non-AIDS-, non-cancer-related immune deficiencies including solid organ transplant or conditions requiring long-term (&gt; 30 days) or high-dose (&gt; 1 mg/kg/day) steroids, or any immunosuppressive drug for more than 30 days

association with mortality do not represent causal relationships.

Most in-ICU platelet transfusions were prophylactic (64%) with a median platelet count before transfusion of 15 x 10⁹/L. Lower proportions of prophylactic platelet transfusions (40-45%) with higher median platelet counts before transfusion have been reported, which likely reflects differences in case mix and changes in practice over time [11, 12]. The European Society of Intensive Care Medicine (ESICM) recommends against prophylactic platelet transfusion unless the platelet count falls below 10 x 10⁹/L, but the recommendation is only conditional due to very low certainty of evidence and randomised trials evaluating this strategy in general ICU patients are warranted [13].

In our cohort, prophylactic pre-procedural platelet transfusions constituted 8% of in-ICU platelet transfusions and currently, ESICM makes no recommendations regarding this strategy for patients with platelet counts between 10-50 x 10⁹/L [13]. A recent non-inferiority trial enrolling patients in haematology wards and ICUs with platelet counts between 10-50 x 10⁹/L showed that withholding versus providing a single prophylactic platelet transfusion before CVC placement was not non-inferior and resulted in more CVC-related bleedings [15]. Interestingly, the occurrence of bleeding was lower in ICU patients compared with haematology ward

patients, which might support a no-transfusion strategy with intensive monitoring in ICU patients [15].

This study has some strengths. It was prospective and conducted, analysed and reported in compliance with a published protocol [16]. Further, contrary to many previous studies [1, 2, 6-9], we included a large, unselected, multinational ICU population. This study also provides data on the use of in-ICU platelet transfusions across several countries, which complements previous national studies [11, 12, 33].

Our study also has some limitations. First, 17% of the patients did not have a baseline platelet count and although we handled this as planned, by using the first available platelet count in the ICU measured on median (IQR) day 1 (1-1), some misclassification cannot be ruled out. Second, 7% of patients were transferred directly from other ICUs, with a median stay of 3 days before inclusion. This could underestimate event rates and overestimate baseline thrombocytopenia at the expense of ICU thrombocytopenia. Third, patients with haematological malignancies constituted 8% of the population and 15% of the cases with thrombocytopenia; frequencies of thrombocytopenia may be lower in ICU populations with lower proportions of patients with haematological malignancies. Fourth, 2% of patients were transferred to a non-study ICU without available daily variables; these were analysed under the assumption that no events occurred during
<figure><img src="image_5.png" /><figcaption>**Fig. 2** In-ICU platelet transfusions and indications. Number of in-ICU platelet transfusions used in patients with- and without thrombocytopenia. Patients with severe- and very severe thrombocytopenia received 93% of all in-ICU platelet transfusions and in patients with very severe thrombocytopenia, 76% of in-ICU transfusions were prophylactic. We did not collect data on indications for 57 platelet transfusions used during surgery, thus these are excluded (see ESM 22 for details)</figcaption></figure>

days spent in the non-study ICU. Fourth, descriptions of platelet counts before platelet transfusions were added post hoc and assumptions made during computation may have affected results. Fifth, we used pre-specified logistic regression analyses to assess risk factors for ICU thrombocytopenia and associations between baseline thrombocytopenia and 90-day mortality. Although post hoc sensitivity analyses including Cox proportional hazard models accounting for time-to-event and competing risks produced similar results, our regression analyses should be interpreted carefully considering the limited number of included variables and risk of residual confounding (e.g., the effects of baseline thrombocytopenia on 90-day mortality may vary according to the underlying cause, which was not assessed in this study). Lastly, meaningful interpretation of risk factor analyses for ICU thrombocytopenia < 50 × 10⁹/L was hampered by few events and the analysis of baseline thrombocytopenia < 50 × 10⁹/L and 90-day mortality was likely underpowered.

## Conclusions

In this international, prospective cohort study, 43% of adult acutely admitted ICU patients had thrombocytopenia. Patients with thrombocytopenia had worse outcomes including increased 90-day mortality. Baseline risk factors for the development of thrombocytopenia during ICU stay included male sex, non-AIDS-, non-cancer related immune deficiency, liver failure, higher illness

severity, bleeding, and septic shock. Platelet transfusions were given to 23% of patients with thrombocytopenia and most were prophylactic.

## Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1007/s00134-023-07225-2.

## Author details

¹ Department of Intensive Care, Copenhagen University Hospital - Rigshospitalet, Copenhagen, Denmark. ² Médecine Intensive and Réanimation, Hôpital Cochin, Assistance Publique-Hôpitaux de Paris, Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Cité, Paris, France. ³ Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark. ⁴ Médecine Intensive and Réanimation, Hôpital Saint-Louis, Assistance Publique-Hôpitaux de Paris, Université Paris Cité, Paris, France. ⁵ Department of Intensive Care, Glasgow Royal Infirmary, Glasgow, UK. ⁶ Division of Pulmonary and Critical Care, Penn State University College of Medicine, Hershey, PA, USA. ⁷ Department of Anaesthesia and Intensive Care Medicine, Division of Emergencies and Critical Care, Oslo University Hospital, Rikshospitalet, Oslo, Norway. ⁸ Critical Care Medicine Service, Department of Anesthesiology and Critical Care Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA. ⁹ Department of Anesthesiology, Weill Cornell Medical College, New York, NY, USA. ¹⁰ Medical Intensive Care Unit, Hospital Clinic of Barcelona, IDIBAPS, University of Barcelona, Barcelona, Spain. ¹¹ Department of Intensive Care, Sao Francisco Xavier Hospital, CHLO, Lisbon, Portugal. ¹² Nova Medical School, CHRC, New University of Lisbon, Lisbon, Portugal. ¹³ Center for Clinical Epidemiology and Research Unit of Clinical Epidemiology, Odense University Hospital, Odense, Denmark. ¹⁴ Department of Critical Care, King's College Hospital NHS Foundation Trust, London, UK. ¹⁵ Department I of Internal Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany. ¹⁶ Department of Hematology and Stem Cell Transplantation, University Hospital Essen, University of Duisburg-Essen, Essen, Germany. ¹⁷ Department of Intensive and Perioperative Care, Skåne University Hospital, Lund, Sweden. ¹⁸ Department of Clinical Sciences, Lund University, Lund, Sweden. ¹⁹ Department of Perioperative and Intensive Care Medicine, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.

²⁰ Department of Anaesthesiology and Intensive Care, Tampere University Hospital and Tampere University, Tampere, Finland. ²¹ Department of Anaesthesia and Intensive Care, Aalborg University Hospital, Aalborg, Denmark.

²² Department of Anaesthesiology and Intensive Care, Odense University Hospital, Odense, Denmark. ²³ Department of Anaesthesiology and Intensive Care, Aarhus University Hospital, Aarhus, Denmark. ²⁴ Service de Médecine Intensive Réanimation, Hôpitaux Universitaires Henri-Mondor, Assistance Publique-Hôpitaux de Paris, Paris, France. ²⁵ Médecine Intensive Réanimation, CHU de Nantes, Université de Nantes, Nantes, France. ²⁶ Critical Care Unit, Elizabeth University Hospital, Glasgow, Queen, UK. ²⁷ Service de Réanimation Médico-Chirurgicale, Hôpital Avicenne, Assistance Publique-Hôpitaux de Paris, Paris, France. ²⁸ Médecine Intensive Réanimation, Hôpital Louis Mourier, Assistance Publique-Hôpitaux de Paris, DMU ESPRIT, Paris, France. ²⁹ Institut Necker-Enfants Malades, Université Paris Cité, INSERMUMR-S1151, CNRSUMR-S8253, Paris, France. ³⁰ Service de Médecine Intensive-Réanimation, Hôpital Saint-Antoine, Assistance Publique-Hôpitaux de Paris, Sorbonne Université, Paris, France. ³¹ Department of Intensive Care, Holbaek Hospital, Holbaek, Denmark. ³² Department of Intensive Care, Hospital General Granollers, Barcelona, Spain. ³³ Intensive Care Department, Vall d'Hebron Hospital Universitari, Barcelona, Spain. ³⁴ SODIR Research Group, Vall d'Hebron Institut de Recerca (VHIR), Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain. ³⁵ Service de Médecine Intensive-Réanimation, Hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Sorbonne Université, Paris, France. ³⁶ Service de Médecine Intensive Réanimation, Hôpital Tenon, Assistance Publique-Hôpitaux de Paris, Sorbonne Université, Centre de Recherche Saint-Antoine UMR_S938 INSERM, Paris, France. ³⁷ Department of Anaesthesia and Intensive Care, Copenhagen University Hospital - Bispebjerg and Frederiksberg, Copenhagen, Denmark. ³⁸ Department of Intensive Care, Copenhagen University Hospital - Herlev and Gentofte, Herlev, Denmark. ³⁹ Department of Anaesthesia and Intensive Care, Haukeland University Hospital, Bergen, Norway. ⁴⁰ Faculty of Medicine, University of Bergen, Bergen, Norway. ⁴¹ Department of Intensive Care, Zealand University Hospital - Roskilde, Roskilde, Denmark.
⁴² Department of Acute Medicine, Oslo University Hospital, Oslo, Norway.

⁴³ Institute of Clinical Medicine, University of Oslo, Oslo, Norway. ⁴⁴ Department of Intensive Care, Stavanger University Hospital, Stavanger, Norway.

⁴⁵ Department of Anaesthesiology and Intensive Care, Copenhagen University Hospital - North Zealand, Hilleroed, Denmark. ⁴⁶ Department of Intensive Care Medicine, St. Olav's University Hospital, Trondheim, Norway. ⁴⁷ Department Circulation and Medical Imaging, Norwegian University of Technology and Science, Trondheim, Norway. ⁴⁸ Medical Intensive Care Unit, Hospital Clinic of Barcelona, University of Barcelona, Barcelona, Spain. ⁴⁹ Médecine Intensive and Réanimation, Hôpital Necker, Assistance Publique-Hôpitaux de Paris, Université Paris Cité, Paris, France. ⁵⁰ Department of Intensive Care, Hospital da Luz Lisboa, Lisbon, Portugal. ⁵¹ Department of Intensive Care, Hospital Central do Funchal, Funchal, Portugal. ⁵² Department of Hematology, Hemostasis, Oncology and Stem Cell Transplantation, Hannover Medical School, Hannover, Germany. ⁵³ Department of Anaesthesiology, Copenhagen University Hospital - Amager and Hvidovre, Hvidovre, Denmark. ⁵⁴ Intensive Care Unit, Hospital Professor Doutor Fernando Fonseca, EPE, Amadora, Portugal. ⁵⁵ Department of Intensive Care B203, Akershus University Hospital, Lorenskog, Norway.

⁵⁶ Department of Intensive Care Medicine-Unit 2, Hospital Egas Moniz-CHLO, EPE, Lisbon, Portugal. ⁵⁷ Department of Intensive Care Medicine-Unit 1, Hospital Egas Moniz-CHLO, EPE, Lisbon, Portugal. ⁵⁸ Department of Intensive Care, Copenhagen University Hospital - Gentofte, Hellerup, Denmark. ⁵⁹ Médecine Intensive & Réanimation, Hôpital Cochin, Assistance Publique - Hôpitaux de Paris, Université Paris Cité, Paris, France. ⁶⁰ Interdisciplinary Intensive Care Unit, Department for Respiratory Diseases and German Centre of Lung Research (DZL), Hannover Medical School, Hannover, Germany.

## Acknowledgements

This study was performed on behalf of the "Caring for critically ill immuno-compromised patients: Multinational Network (Nine-I)" study group. PLOT-ICU Collaborators: Ahmed Khalil, Ahmed Yehia, Haney Salem, Hesham Farahat, Manu Sudevan, Melissa Biggart, Nirmeen Fatima, Mohammed Elkhonezy, Department of Critical Care, King's College Hospital NHS Foundation Trust, London, UK; Anne-Marie Bunzel, Rine M. Siegumfeldt, Stine R. Vestergaard; Department of Anesthesia and Intensive Care, Aalborg University Hospital, Aalborg University, Aalborg, Denmark; Juliette Pelle, Minh-Pierre Lê, Clara Vigneron, Morgane Bertrix, Paul Cirera, Driss Laghlam, Swann Bredin, Nathalie Marin, Médecine Intensive & Réanimation, Hôpital Cochin, Assistance Publique-Hôpitaux de Paris, Université Paris Cité, Paris, France; Maria Toppenberg, Department of Anaesthesiology and Intensive Care, Aarhus University Hospital, Aarhus, Denmark; Bruce Benelli, Service de Médecine Intensive Réanimation, Hôpitaux Universitaires Henri-Mondor, Assistance Publique-Hôpitaux de Paris, Paris, France. Amélie Seguin, Charlotte Garret, Florian Guillotin, Gauthier Blonz, Jean-Baptiste Lascarrou, Jérémie Lemarie, Luc Desmedt, Maîté Agbakou, Mathieu Carpentier, Maëlle Martin, Naïla Benkalfate, Olivier Zambon, Paul Decamps, Pauline L. Wilquin, Soraya Benguerif, Médecine Intensive Réanimation, CHU de Nantes, Université de Nantes, Nantes, France; John Gardner, Critical Care Unit, Queen Elizabeth University Hospital, Glasgow, UK; Natalie Remor, Sheila Carr, Gloria Yang, Critical Care Medicine Service, Department of Anesthesiology & Critical Care Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA; Coralie Gernez, Ingrid Thiry, Médecine Intensive Réanimation, Hôpital Louis Mourier, Assistance Publique-Hôpitaux de Paris, DMU ESPRIT, Paris, France; Louai Missri, Service de Médecine Intensive-Réanimation, Hôpital Saint-Antoine, Assistance Publique-Hôpitaux de Paris, Sorbonne Université, Paris, France; Moritz K. G. Denneborg Department of Intensive Care, Holbaek Hospital, Holbaek, Denmark; Katherine Brown, Department of Intensive Care, Glasgow Royal Infirmary, Glasgow, UK; Vanessa Casares, Intensive Care Department, Vall d'Hebron Hospital Universitari, Barcelona, Spain; Mirka Sivula, Elina Lappi, Leena Pettilä, Jonna Heinonen, Minttu Saario, Department of Perioperative and Intensive Care Medicine, University of Helsinki and Helsinki University Hospital, Helsinki, Finland; Manal K. Mecheri, Alezandre Elabbadi, Cyrielle Desnos; Antoine Lafarge, Olfa Mghirbi, Médecine Intensive & Réanimation, Hôpital Saint-Louis, Assistance Publique-Hôpitaux de Paris, Université Paris Cité, Paris, France; Brit Å. Sjøbø, Department of Anaesthesiology and Intensive Care, Haukeland University Hospital, Bergen, Norway; Cecilie Christoffersen, Department of Anaesthesia and Intensive Care Medicine, Division of Emergencies and Critical Care, Rikshospitalet, Oslo University Hospital, Oslo, Norway; Frederik H. Bestle, Department of Anaesthesiology and Intensive Care, Copenhagen University Hospital-North Zealand, Hilleroed,

Denmark; Claudia Lemos, Department of Intensive Care, Hospital Central do Funchal, Funchal, Portugal; Cristiana V. Gonçalves, Nuno M. B. Jacinto, Monica P. Anselmo, Intensive Care Unit, Hospital Professor Doutor Fernando Fonseca, EPE, Amadora, Portugal; Marius M. Hoeper, Interdisciplinary Intensive Care Unit, Department for Respiratory Diseases and German Centre of Lung Research (DZL), Hannover Medical School, Hannover, Germany; Marja Hoff, Department of Intensive Care B203, Akershus University Hospital, Akershus, Norway; Pedro M. Simões Freire, Department of Intensive Care Medicine, Unit 2, Hospital Egaz Moniz-CHLO, EPE, Lisbon, Portugal.

## Author contributions

CTA, FP, AP, EA, KP, AVDL, ABD, SC, PC, PP, LC, VM, MK, TL, TK, JH, MHM and LR conceptualised the study. All authors contributed to the acquisition of the data. CTA and AG performed the statistical analyses. CTA drafted the manuscript with input from the steering committee and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript for publication.

## Funding

Open access funding provided by Royal Library, Copenhagen University Library. This study was funded by the Research Council of Rigshospitalet, the Ehrenreich's Foundation, and the Dagmar Marshalls Foundation. The Memorial Sloan Kettering Cancer Center part of the study was supported by the Core Grant, Grant/Award Number: P30CA008748; Department of Anaesthesiology & Critical Care Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, United States of America. None of the funders had any influence on the design, conduct or reporting of the study.

## Data availability

The data that support the findings of this study can be made available from the corresponding author (LR) upon request.

## Declarations

### Conflicts of interest

The Department of Intensive Care at Rigshospitalet (CTA, AG, MHM, AP, LR) has received funding for other projects from the Novo Nordisk Foundation, Sygeforsikringen 'danmark', and Pfizer and has conducted contract research for AM-Pharma. FP has received honoraria for consulting and lectures from Gilead and an institutional grant from Alexion Pharma. AP has received honoraria from Novartis for participation in an advisory board. EA has received research grants from MSD Avenir and Alexion and honoraria for lectures from Alexion, Sanofi and Pfizer. AVDL has received honoraria from Sanofi for participation in an advisory board. PC has received consulting fees from Sanofi, Gilead, Alexion and Janssen and honoraria for lectures from Merck Sharp & Dohme, Gilead, Alexion and Pfizer. PP has received consulting fees from Sanofi and Gilead and honoraria from Merck Sharp & Dohme, Gilead, Mundipharma and Pfizer for academic and educational work. JH has received consulting fees from Paion and honoraria for lectures from the Finnish Medical Association, Laboratory Medicine and Duodecim. EC received fees for lectures and conference talks and had travel and accommodation expenses related to attending scientific meetings covered by Gilead, Shionogi B.V. and Sanofi-Genzyme. ARH has received honoraria from Pfizer for lectures. MHB has received consulting fees from AM-pharma and Inotrem. Full disclosure forms from all authors are available on the publisher's website.

### Open Access

This article is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, which permits any non-commercial use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc/4.0/.
**Publisher's Note**

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Received: 19 June 2023 Accepted: 5 September 2023

Published: 9 October 2023

**References**

1. Strauss R, Wehler M, Mehler K et al (2002) Thrombocytopenia in patients in the medical intensive care unit: bleeding prevalence, transfusion requirements, and outcome. Crit Care Med 30:1765-1771. https://doi.org/10.1097/00003246-200208000-00015

2. Crowther MA, Cook DJ, Meade MO et al (2005) Thrombocytopenia in medical-surgical critically ill patients: prevalence, incidence, and risk factors. J Crit Care 20:348-353. https://doi.org/10.1016/j.jcrc.2005.09.008

3. Greinacher A, Selleng S (2016) How i evaluate and treat thrombocytopenia in the intensive care unit patient. Blood 128:3032-3042. https://doi.org/10.1182/blood-2016-09-693655

4. Hui P, Cook DJ, Lim W et al (2011) The frequency and clinical significance of thrombocytopenia complicating critical illness: a systematic review. Chest 139:271-278. https://doi.org/10.1378/CHEST.10-2243

5. Jonsson AB, Rygård SL, Hildebrandt T et al (2021) Thrombocytopenia in intensive care unit patients: a scoping review. Acta Anaesthesiol Scand 65:2-14. https://doi.org/10.1111/AAS.13699

6. Venkata C, Kashyap R, Christopher Farmer J, Afessa B (2013) Thrombocytopenia in adult patients with sepsis: incidence, risk factors, and its association with clinical outcome. J Intensive Care 1:1-10. https://doi.org/10.1186/2052-0492-1-9

7. Hanes SD, Quarles DA, Boucher B (1997) Incidence and risk factors of thrombocytopenia in critically ill trauma patients. Ann Pharmacother 3:285-289. https://doi.org/10.3760/cma.j.issn.0366-6999.2010.08.004

8. Stephan F, Hollande J, Richard O et al (1999) Thrombocytopenia in a surgical ICU. Chest 115:1363-1370. https://doi.org/10.1378/chest.115.5.1363

9. Sharma B, Sharma M, Majumder M et al (2007) Thrombocytopenia in septic shock patients—a prospective observational study of incidence, risk factors and correlation with clinical outcome. Anaesth Intensive Care 35:874-880. https://doi.org/10.1177/0310057x0703500604

10. Greinacher A, Selleng K (2010) Thrombocytopenia in the intensive care unit patient. Hematology 2010:135-143. https://doi.org/10.1182/ASHEDUCATION-2010.1.135

11. Arnold DM, Crowther MA, Cook RJ et al (2006) Utilization of platelet transfusions in the intensive care unit: indications, transfusion triggers, and platelet count responses. Transfusion 46:1286-1291. https://doi.org/10.1111/j.1537-2995.2006.00892.X

12. Rao MP, Boralessa H, Morgan C et al (2002) Blood component use in critically ill patients. Anaesthesia 57:530-534. https://doi.org/10.1046/J.1365-2044.2002.02514.X

13. Vlaar AP, Oczkowski S, de Bruin S et al (2020) (2020) Transfusion strategies in non-bleeding critically ill adults: a clinical practice guideline from the European Society of Intensive Care Medicine. Intensive Care Med 46(46):673-696. https://doi.org/10.1007/S00134-019-05884-8

14. Anthon CT, Granholm A, Sivapalan P et al (2022) Prophylactic platelet transfusions versus no prophylaxis in hospitalized patients with thrombocytopenia: a systematic review with meta-analysis. Transfusion. https://doi.org/10.1111/TRF.17064

15. van Baarle FLF, van de Weerdt EK, van der Velden WJFM et al (2023) Platelet transfusion before CVC placement in patients with thrombocytopenia. N Engl J Med 388:1956-1965. https://doi.org/10.1056/NEJMOA2214322

16. Anthon CT, Pène F, Perner A et al (2022) Platelet transfusions and thrombocytopenia in intensive care units: protocol for an international

inception cohort study (PLOT-ICU). Acta Anaesthesiol Scand. https://doi.org/10.1111/AAS.14124

17. von Elm E, Altman DG, Egger M et al (2007) Strengthening the reporting of observational studies in epidemiology (STROBE) statement: guidelines for reporting observational studies. BMJ 335:806-808. https://doi.org/10.1136/BMJ.39335.541782.AD

18. Harris PA, Taylor R, Thielke R et al (2009) Research electronic data capture (REDCap)—a metadata-driven methodology and workflow process for providing translational research informatics support. J Biomed Inf 42:377-381. https://doi.org/10.1016/J.JBI.2008.08.010

19. Harris PA, Taylor R, Minor BL et al (2019) The REDCap consortium: building an international community of software platform partners. J Biomed Inf. https://doi.org/10.1016/J.JBI.2019.103208

20. Granholm A, Perner A, Krag M et al (2018) Development and internal validation of the simplified mortality score for the intensive care unit (SMS-ICU). Acta Anaesthesiol Scand 62:336-346. https://doi.org/10.1111/aas.13048

21. Granholm A, Perner A, Krag M et al (2019) External validation of the simplified mortality score for the intensive care unit (SMS-ICU). Acta Anaesthesiol Scand 63:1216-1224. https://doi.org/10.1111/aas.13422

22. Stanworth SJ, Estcourt LJ, Powter G et al (2013) A no-prophylaxis platelet transfusion strategy for hematologic cancers. N Engl J Med 368:1771-1780. https://doi.org/10.1056/NEJMoa1212772

23. Wandt H, Schaefer-Eckart K, Wendelin K et al (2012) Therapeutic platelet transfusion versus routine prophylactic transfusion in patients with haematological malignancies: an open-label, multicentre, randomised study. Lancet 380:1309-1316. https://doi.org/10.1016/S0140-6736(12)60689-8

24. Heddle NM, Cook RJ, Tinmouth A et al (2009) A randomized controlled trial comparing standard- and low dose strategies for transfusion of platelets (SToP) to patients with thrombocytopenia. Blood 113:1564-1573. https://doi.org/10.1182/blood-2008-09-178236

25. Slichter SJ, Kaufman RM, Assmann SF et al (2010) Dose of prophylactic platelet transfusions and prevention of hemorrhage. N Engl J Med 362:600-613. https://doi.org/10.1056/NEJMoa0904084

26. Nagelkerke NJD (1991) A note on a general definition of the coefficient of determination. Biometrika 78:691. https://doi.org/10.2307/2337038

27. Labarère J, Bertrand R, Fine MJ (2014) How to derive and validate clinical prediction models for use in intensive care medicine. Intensive Care Med 40:513-527. https://doi.org/10.1007/S00134-014-3227-6/TABLES/4

28. Vanderschueren S, De Weerdt A, Malbrain M et al (2000) Thrombocytopenia and prognosis in intensive care. Crit Care Med 28:1871-1876. https://doi.org/10.1097/00003246-200006000-00031

29. Williamson DR, Albert M, Heels-Ans dell D et al (2013) Thrombocytopenia in critically ill patients receiving thromboprophylaxis: frequency, risk factors, and outcomes. Chest 144:1207-1215. https://doi.org/10.1378/chest.13-0121

30. Williamson DR, Lesur O, Tétrault JP et al (2013) Thrombocytopenia in the critically ill: prevalence, incidence, risk factors, and clinical outcomes. Can J Anesth 60:641-651. https://doi.org/10.1007/s12630-013-9933-7

31. Lillemäe K, Luostarinen T, Reinikainen M et al (2022) Early thrombocytopenia is associated with an increased risk of mortality in patients with traumatic brain injury treated in the intensive care unit: a Finnish Intensive Care Consortium study. Acta Neurochir (Wien) 164:2731-2740. https://doi.org/10.1007/s00701-022-05277-9

32. Aissaoui Y, Benkabbou A, Alilou M et al (2007) Thrombocytopenia in a surgical intensive care unit: incidence, risk factors and effect on outcome. Presse Med 36:43-49. https://doi.org/10.1016/J.LPM.2006.05.001

33. Stanworth SJ, Walsh TS, Prescott RJ et al (2013) Thrombocytopenia and platelet transfusion in UK critical care: a multicenter observational study. Transfusion 53:1050-1058. https://doi.org/10.1111/j.1537-2995.2012.03866.x