Fluid Responsiveness After CArdiac Surgery Study

Study Overview
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Brief Summary
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Study Design: Prospective observational study Study Location: Liverpool Hospital Intensive Care Unit, South Western Sydney Local Health District, Sydney, Australia. Target study size: 100 patients Ethics: Approved by the local Human Research and Ethics Council (HREC) at Liverpool Hospital (LPOOL) as a Low Negligible Risk (LNR) project [HREC/LNR/14/LPOOL/295, HREC/LNR/15/LPOOL47, HREC/LNR/14/LPOOL/150] Participants: Post cardiac surgical patients admitted to the Intensive Care Unit between March-October 2016 Aims: to determine the descriptive and predictive value of variables (outlined below) related to oxygen delivery/consumption in regards to the effects of intravascular volume expansion to assess correlations between central and peripheral variables (outlined below) relevant to oxygen delivery/consumption to assess correlations between a set of variables (outline below) and patient centred outcomes in ICU and in hospital Main variables collected: Tissue oxygen saturation by peripheral Near-Infrared Spectroscopy (NIRS) Common carotid arterial Doppler Arterial/mixed venous/central venous blood gas analyses Haemodynamic parameters Organ support measures Data collection time points: ICU admission (within 30 minutes) Before administration of a fluid bolus After administration of a fluid bolus 6 hours after ICU admission Morning of first postoperative day (12-24 hours) Outcome measures: the response to intravascular volume expansion ICU mortality, morbidity and length of stay and hospital mortality and length of stay Data analysis: Clinical data are collected bedside using an electronic case record form Descriptive statistics Paired and unpaired comparative Correlative and predictive statistics

Detailed Description
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This prospective observational study program has a set of objectives within three major domains that will be analysed separately and synergistically: Peripheral near infra-red spectroscopy (NIRS) Aims: to describe the effects of non-sanguineous intravascular volume expansion on systemic oxygen delivery to describe how changes in systemic oxygen delivery impact on peripheral oxygen kinetics as measured by tissue oxygen saturation (StO2) in the thenar and forearm regions at rest and using a vascular occlusion test to determine the clinical applicability of using thenar and forearm NIRS to guide haemodynamic optimisation following cardiac surgery to assess the relation between systemic and peripheral oxygen kinetics vs. onset of organ dysfunction and need for extended stay in ICU following cardiac surgery Hypotheses: Peripheral oxygen kinetics using NIRS offer more specific guidance for haemodynamic optimisation post cardiac surgery compared to using systemic variables only Impaired peripheral oxygen kinetics as assessed using NIRS can be used to identify patients at risk for developing organ dysfunction or needing extended period of ICU support an earlier stage compared to traditional systemic variables Main measurements: peripheral near infrared spectroscopy (NIRS) measuring tissue oxygen saturation (StO2) at the thenar eminence and forearm during a 3 minute vascular occlusion test at 50mmHg above systolic pressure, following the establishment of a baseline (an StO2 average over 3 minutes with less than 5% variability) StO2 measurements are repeated at 30 minutes intervals during the first 6 hours following admission to ICU. vascular occlusion tests are repeated before and after volume expansion. Cardiac output and common carotid Doppler sonography Aims: to apply computerised algorithms to derive advanced haemodynamic information (mean systemic filling pressure, heart efficiency, vascular compliance) in patients requiring fluid boluses following cardiac surgery to correlate changes in cardiac output, cardiac power and estimates of fluid responsiveness using the pulmonary artery catheter with the variables mean systemic filling pressure and heart efficiency to characterise indices of fluid responsiveness by measuring volume efficiency to determine the impact of changes in vascular resistance state on the assessment of changes in volume state in the post-operative cardiac surgery period to assess the relation between fluid responsiveness, fluid management and clinical outcomes in ICU following cardiac surgery to evaluate the potential for carotid Doppler blood flow measurements as a surrogate parameter for cardiac output, including incorporation into computerised algorithms Hypotheses: the derived measures of mean systemic filling pressure and heart efficiency are superior to identify fluid responsiveness compared to cardiac output measurements alone in patients following cardiac surgery carotid Doppler blood flow measurements can be used as a surrogate parameter for cardiac output and in particular for changes in cardiac output when fluid responsiveness is investigated Main measurements: Pulmonary arterial thermodilution studies (for cardiac output, stroke volume, cardiac index) by at least triplicate injections within a ± 10% range Computerised algorithms are used to derive an analogue mean systemic filling pressure, heart efficiency, volume efficiency based on cardiac output, central venous pressure and mean arterial pressure Common carotid Doppler sonography to measure vessel diameter, cross sectional area and time average mean velocity to generate blood flow as well as respirophasic peak flow velocity variation Oxygen and carbon dioxide gradients Aims: to assess any insufficiency of oxygen delivery to match the oxygen consumption, resulting in anaerobic metabolism, by determining i) arteriovenous concentration gradients for lactate, ii) the venoarterial carbon dioxide tension gradient [P(v-a)CO2] and the arteriovenous oxygen content gradient ([C(a-v)O2] to assess whether central venous blood gas analyses can substitute pulmonary arterial (mixed venous) blood gas analyses in the [P(v-a)CO2] and [C(a-v)O2] gradients and ratio to assess whether arteriovenous O2 and CO2 gradients are more specific and contemporaneous measures of anaerobic metabolism compared to serum lactate Hypotheses: Changes in [C(a-v)O2] and [P(v-a)CO2] gradients can be used as prognostic markers with persistently abnormal values correlating with the presence and degree of organ failure Changes in [C(a-v)O2] and [P(v-a)CO2] gradients can be used as targets during haemodynamic optimisation Cumulative measurements of [C(a-v)O2] and [P(v-a)CO2] gradients to generate an area under the curve value can be used to assess and target the presence of an oxygen debt Main measurements 1) Central venous, pulmonary arterial (mixed venous) and arterial blood gas analyses (pO2, pCO2, bicarbonate and lactate concentrations) A fluid bolus will be administered as 250ml or 500ml of fluid (crystalloid or colloid) at 1500ml/hour. Measurements will be conducted immediately before fluid administration and 10 minutes post fluid cessation. The following risk scores will be calculated: Sequential Organ Failure Assessment (SOFA), Acute Physiology and Chronic Health Evaluation (APACHE II and III), Simplified Acute Physiology Score (SAPS2), Australian New Zealand Risk of Death (ANZROD), Euroscore 2. Routine biochemical tests will be recorded including electrolytes, renal function tests, liver function tests.

Official Title
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Fluid Responsiveness After Cardiac Surgery (FRACAS) Study

Conditions
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Critically Ill, Hypovolemia

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Admitted following elective cardiac surgery Adult (>18 years of age) Pulmonary artery, central venous and arterial catheters inserted Exclusion Criteria: Emergency Patients (surgery immediately or within 12 hours of admission to hospital) Children (< 18 years of age) Patients admitted to ICU with ongoing extracorporeal circulatory support Patients re-admitted to ICU within same index hospital admission

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Fluid bolus responsiveness | Fluid responsiveness will be determined by any increase in cardiac output (continuous outcome) or by a 10-15% increase in cardiac output (dichotomous outcome) following bolus volume expansion | Approximately 30 minutes | 
| Volume management responsiveness | Responders will be defined as patients with an improvement (change towards normal physiological values) following cumulative volume expansion in any variable(s) used to assess oxygen delivery/consumption balance | Approximately 6 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Morbidity | Use and extent of measures to support organ function such as mechanical ventilation, mechanical and pharmacological cardiovascular interventions, renal replacement therapy whilst admitted to ICU as well as length of admission to ICU. | At ICU discharge, an average of 4 days | 
| Mortality | Vital status censored at discharge from ICU and hospital | Up to 3 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Fluid responsiveness, Near-infrared spectroscopy, Thoracic surgery, Hypovolemia, veno-arterial carbon dioxide gradient, arterio-venous oxygen gradient, hypercarbia, Carotid artery, ultrasonography, Doppler