Predictability of Central Venous to Arterial CO2 Difference (AVCO2) in Children With Cardiac Surgery to Poor Outcomes
Conditions: Congenital Heart Disease, Perioperative/Postoperative Complications, Lactate Blood Increase
Sponsor: Prince of Songkla University

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Research Protocol (Full Proposal) 
1 
Human Research Ethics Committee (HREC) 
2 
Faculty of Medicine, Prince of Songkla University 
3 
-------------------------------------------------------------------------------------------------------- 
4 
1. Title of the study in Thai and English 
5 
Thai: การศึกษาความแม่นย าของค่าผลต่างของคาร์บอนไดออกไซด์ในหลอดเลือดด าใหญ่และหลอดเลือดแดงและค่า
6 
การอักเสบต่อการท านายผลการรักษาหลังผ่าตัดหัวใจ 
7 
English: Predictability of central venous to arterial CO2 difference (AVCO2) and inflammatory markers in 
8 
children with cardiac surgery to poor outcomes  
9 
 
10 
2. Principal Investigator 
11 
 
Name: Pharsai Prasertsan M.D. 
12 
  
Position: Clinical instructor  
13 
 
Affiliation: Division of Critical care medicine, Department of Pediatrics  
14 
 
Telephone Number: 074-451250-1  
Mobile Phone Number: 083-6876319 
15 
 
E-mail: pharsai_16@yahoo.com 
16 
 
Responsibility in the project: drafting protocol, data analysis and manuscript writing  
17 
 
18 
3. Sub-investigators and advisors 
19 
3.1 Name: Pornnicha Chaiwiriyawong, M.D.  
20 
 
Position: Resident  
21 
 
Affiliation: Department of Pediatrics  
22 
 
Telephone Number: 074-451250-1  
Mobile Phone Number: 083-6876319 
23 
 
E-mail: mymelo_123@hotmail.com 
24 
 
Responsibility in the project: data collection and data analysis   
25 
3.2 Name: Jirayut Jarutach, M.D. 
26 
  
Position: Clinical instructor  
27 
 
Affiliation: Division of Pediatrics cardiology, Department of Pediatrics  
28 
 
Telephone Number: 074-451250-1  
Mobile Phone Number: 081-397-0385 
29 
 
E-mail: JirayuthpedC@gmail.com 
30 
 
Responsibility in the project: data collection and review manuscript 
31 
3.3 Name: Pongsanae Duangpakdee, M.D. 
32 
  
Position: Clinical instructor  
33 
 
Affiliation: Division of Cardiovascular and thoracic surgeon, Department of Surgery 
34 
 
Telephone Number: 074-451404  Mobile Phone Number: 081-5438022 
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E-mail: pongsanae.d@psu.ac.th 
1 
 
 
Responsibility in the project: data collection and review manuscript 
2 
3.4 Name: Polathep Vichitkunakorn, M.D., Ph.D. 
3 
  Position: Clinical instructor  
4 
 
Affiliation: Department of Family and Preventive Medicine 
5 
 
Telephone Number: 074-451330  Mobile Phone Number: 087-4948125 
6 
 
E-mail: polathep.v@psu.ac.th 
7 
 
Responsibility in the project: methodology, data analysis, and review manuscript 
8 
3.5 Name: Smonrapat Surasombatpattana, Ph.D. 
9 
  Position: Clinical instructor  
10 
 
Affiliation: Division of immunology and virology, Department of Pathology 
11 
 
Telephone Number: 074-451551  Mobile Phone Number: 095-9572903 
12 
 
E-mail: pornapat19@gmail.com 
13 
 
Responsibility in the project: blood sample analysis for inflammatory markers  
14 
3.6 Name: Kanokpan Ruangnapa, M.D.  
15 
  Position: Clinical instructor  
16 
 
Affiliation: Division of Pediatric respiratory, Department of Pediatrics 
17 
 
Telephone Number: 074-451551  Mobile Phone Number: 081-3275677 
18 
 
E-mail: kanoknokpan@gmail.com 
19 
 
Responsibility in the project: recruit participant, review manuscript  
20 
3.7 Name: Kantara Saelim  
21 
  Position: Clinical instructor  
22 
 
Affiliation: Division of Pediatric Critical Care Medicine, Department of Pediatrics 
23 
 
Telephone Number: 074-451551  Mobile Phone Number: 065-2154864 
24 
 
E-mail: pigun113@gmail.com 
25 
 
Responsibility in the project: recruit participant, review manuscript 
26 
  
27 
4. Student support 
28 
Check   in (  ) that apply 
29 
(  ) Not associated  
30 
() Undergrad./post grad. Pornnicha Chaiwiriyawong, M.D. 
31 
5. Keywords: AVCO2, inflammatory markers, post cardiac surgery, cardiopulmonary bypass  
32 
6. Background and rationale  
33 
Cardiopulmonary bypass (CPB) is a potent stimulus causing systemic inflammatory response in children 
34 
with cardiac disease who undergone open heart surgery. Mechanisms of inflammatory generator during CPB 
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include blood contact with CPB circuit, ischemia-reperfusion injury, heparin-protamine interactions, and surgical 
1 
trauma. These mechanisms aggravate the activation of complement cascade, release of endotoxin, and altered 
2 
cytokine production which led to low cardiac output syndrome (LCOS)1  
3 
The LCOS refers to declining cardiac function in the face of an elevated demand of cardiac output which 
4 
may lead to multiorgan failure and death. Incidence of the LCOS is approximately 25% of children after cardiac 
5 
surgery1 and commonly occurs 6-18 hours following admission to intensive care unit2. Currently, there is no 
6 
consensus for diagnostic criteria of the LCOS and accurate detection of early cardiac output (CO) insufficiency 
7 
is a challenging task especially in post-operative children. Measurement CO by using thermodilution method 
8 
via Swan-Ganz catheterization or transesophageal echocardiography are not applicable in pediatrics setting 
9 
meanwhile transthoracic echocardiography immediately after post-cardiac operation is limited due to surgical 
10 
wound and tissue swelling. In Songklanagarind Hospital, clinicians practically use parameters such as serum 
11 
lactate, central venous oxygen saturations (ScvO2), and arteriovenous oxygen difference (AVO2) as bedside 
12 
surrogates of CO. However, these parameters can be influenced by multiple factors unrelated to LCOS3. 
13 
Hyperlactatemia in cardiac surgery could be elevated due to post-operative stress response, use of beta-
14 
adrenergic agonist, hyperglycemia, or reduce lactate clearance due to transaminitis while normal values of 
15 
ScvO2 can be found despite microcirculatory dysfunction and localized tissue hypoxia4.  
16 
Central venous to arterial CO2 partial pressure difference (AVCO2) measures the circulatory clearance of 
17 
tissue CO2 and has been proven to be correlated with CO in critically ill adult patients5. Widening of AVCO2 
18 
represents an imbalance between CO2 clearance by CO and tissue CO2 production. With limited data available, 
19 
it remains unknown whether AVCO2 is a useful adjunctive marker for assessment CO adequacy in pediatric 
20 
patients after cardiac surgery with CPB. 
21 
Additionally, increase cytokine production both pro- (interleukin (IL)-6, IL-8, and tumor necrotic factor 
22 
(TNF)-α) and anti-inflammatory cytokines (IL-4, IL-10) caused by CPB-induced inflammatory activation can 
23 
alter multiorgan function and vascular permeability. The relationship between level of these cytokines and 
24 
clinical outcomes also remains uncertainty in children population. 
25 
We aimed to evaluate the association between AVCO2 and inflammatory markers at 4 different time points 
26 
post operatively with LCOS-related poor outcome and calculate predictability of these markers to facilitate 
27 
earlier recognition and management LCOS in children undergone cardiac surgery with CPB.  
28 
 
29 
7. Objective(s) of the study 
30 
 
Main or Primary objective: To compare accuracy of prediction of LCOS-related poor outcome between 
31 
AVCO2 and traditional bedside surrogates (lactate, ScvO2 and AVO2) in children with cardiac disease who 
32 
undergone CPB. 
33 
 
Secondary objectives:  
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7.1 To evaluate association between AVCO2 in children with cardiac disease who undergone CPB and other 
1 
morbidities: 28-ventilator free day, 28-ICU free day, acute kidney injury, and deaths from any cause during 
2 
hospitalization. 
3 
7.2 To evaluate association between level of pro- and anti-inflammatory cytokine in children who undergone 
4 
CPB and LCOS-related poor outcome. 
5 
 
6 
8. Conceptual framework 
7 
 
8 
9. Literature review  
9 
AVCO2 difference  
10 
 
A retrospective study done by Rhodes LA, et al3 evaluated correlation of AVCO2 with other cardiac output 
11 
surrogates (lactate, ScvO2 and AVO2) and its capacity to predict poor outcomes associated with LCOS in 139 
12 
infants who undergone CPB. There were only 24.5% of poor outcome in this study. The results showed moderate 
13 
correlation between AVCO2 difference with AVO2 (R2 = 0.53; p< 0.01), and ScvO2 (R2 = -0.43; p < 0.01), but not 
14 
lactate. Unadjusted ROC analysis demonstrated that AVCO2 had lower AUC than ScvO2, but higher AUC than 
15 
serum lactate (AUC of AVCO2 0.69 vs ScvO2 0.74 vs lactate 0.64). After multivariable logistic regression analysis, 
16 
admission AVCO2 remained significantly associated with poor outcome (OR, 1.3; 95% CI, 1.1-1.45), including 
17 
independent association with mortality (OR, 1.2; 95% CI, 1.07-1.31). Limitation of this study include missing data 
18 
of blood gas analysis and lack of simultaneous hemodynamic variables and concurrent echocardiogram. The 
19 
population in this study also limited only to infant age less than 90 days. Another retrospective cohort study done 
20 
in 54 Pakistan’s children also showed moderate correlation between AVCO2 and ScvO2 (R2 = 0.34), but the 
21 
participants were still limited in complete repair of congenital heart defect. As accuracy of ScvO2 depends on 
22 
intracardiac structure, the correlation between AVCO2 and ScvO2 in incomplete repair is unknown6.  
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A retrospective study done by Arkamatsu T, et al7 evaluated the association of AVCO2 with morbidities in 114 
1 
pediatrics patients who undergone CPB. The result reported poor correlation of AVCO2 with other parameters 
2 
(lactate, ScvO2). Additionally, comparing patients who had high (VACO2 > 6 mmHg) and low gap (VACO2 < 6 
3 
mmHg) of VACO2, there was no difference of intubation time nor length of ICU stay. However, the outcome in this 
4 
study did not directly relate to LCOS.  
5 
 
 
6 
 
There were 2 prospective and 4 retrospective studies done in adult who undergone CPB4, 8-12. Some reported 
7 
the significant association between AVCO2 and poor outcome4, 9-11 but some did not8, 12. However, poor outcome 
8 
was defined differently in each study which might not be referred to LCOS-related complications. 
9 
 
Inflammatory cytokines 
10 
 
Unlike the AVCO2 studies, most studies on inflammatory cytokine in pediatric cardiopulmonary bypass surgery 
11 
were prospective analysis. Allan CK, et al13 assessed the relationship between level of inflammatory cytokines (IL-
12 
6, IL-8, IL-10, TNF α, IL-1β, and CPR) and clinical outcome at different time points (pre CPB, post CPB at 0, 6 
13 
12, and 24 hours) in 93 pediatric patients. The result demonstrated that level of postoperative IL-6 and IL-8 at 0 
14 
and 24 hours correlated significantly with length of ICU stay and postoperative blood product administration. 
15 
However, this study did not report outcome related with LCOS. Another study measured inflammatory mediators 
16 
(IL-6, IL-8, IL-10, and TNF α) and cardiac markers (N-terminal pro-B-type natriuretic peptide and troponin I) in 46 
17 
cardiac pediatrics patients14. Multivariate logistic regression identified pre-operative N-terminal pro-B-type natriuretic 
18 
peptide ≥ 470 fmol/ml and post-operative IL-8 at 4 hour ≥ 128 pg/ml were significantly related with LCOS events. 
19 
The most recent study published in 202115 evaluated inflammatory mediators in 31 patients with congenital 
20 
heart disease.  It showed higher preoperative IL- 10 and 24- hour postoperative IL- 8 level were associated 
21 
significantly with LCOS. 
22 
Research methodology 
23 
9.1. 
Study design: prospective diagnostic study  
24 
9.2. 
Setting of the study/Trial site: 8-bed pediatric intensive care unit, Songklanagarind Hospital, Hat Yai, 
25 
Songkhla 
26 
9.3. 
Target population: Children with cardiac disease in Songklanagarind hospital who undergone open 
27 
cardiac surgery with cardiopulmonary bypass (age < 18 years old) 
28 
9.4. 
Study population  
29 
9.4.1. Inclusion criteria:  
30 
- Children aged 0-18 years old with either congenital or acquired cardiac disease  
31 
- Undergone cardiopulmonary bypass for cardiac surgery  
32 
- Be admitted in PICU for post-operative care 
33 
9.4.2. Exclusion criteria 
34 
- Preterm infant (GA < 37 weeks) or weight less than 2 kg  
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- Patient who weaned off cardiopulmoanry bypass and required extracorporeal membrane 
1 
oxygenator (ECMO) before leaving the operating room 
2 
- Patient who required emergency cardiac operation within 24 hour after hospitalization  
3 
- Patient who had significant residual left side outflow tract obstruction (e.g., coarctation of 
4 
aorta, interrupted aortic arch) which defined by difference of SBP between upper and lower 
5 
extremities more than 10 mmHg 
6 
- Patient who had already participated in another research project  
7 
- Patient who does not have both arterial line and central line catheter back from operating room  
8 
- Parents or legal guardian refuse to inform consent.  
9 
9.4.3. Withdrawal criteria:  
10 
- Parents or legal guardian request to withdraw from research  
11 
9.4.4. Termination criteria: none  
12 
9.5. 
Sample size calculation 
13 
For the 1st objective, we apply diagnostic study as follows:  
14 
 
15 
Where: Sensitivity (p)   
 
 
 
= 0.85 
16 
 
 
Precision (d); not more than 10% of p 
 
= 0.09 
17 
 
 
Alpha   
 
 
 
 
= 0.05 
18 
We applied the sensitivity of lactate > 3 mmol/L for major morbidity, which defined as at least one of 
19 
complications (i.e., neurological, pulmonary, gastroenteric, and need for extracorporeal membranes oxygenation or 
20 
ventricular-assist device, or sepsis)16. 
21 
Estimated patient (n0) is 61 cases. Based on 48% of incidence of LCOS-related outcome last year in our 
22 
study setting, the required total sample size including non-disease and disease participants will be 128 (=61/0.48).  
23 
Regarding with our sample size calculation for two objectives and an estimate of 20% of unusable data 
24 
from a sample of 128 participants has been considered. The final sample size is 154 participants for sensitivity of 
25 
0.85. However, we will collect blood sample for inflammatory markers in 32 patients for preliminary analysis.  
26 
 
27 
9.6. 
Variables of the study 
28 
9.6.1. Dependent variable: poor outcomes indirectly represented from low cardio output syndrome  
29 
- LCOS-related poor outcome is modified from the study of Drennan SE, et al and Carmona, et al14, 15 
30 
which consisting of at least two of the following criteria within 48 hour post operatively:  
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a. Clinical findings suggestive of LCOS: prolonged capillary refill > 3 s, systolic blood pressure < 5th 
1 
percentile for age and gender, persistently elevate of LA pressure above 10 mmHg for at least 6 hr 
2 
, low urine output (< 1mL/kg/hr) for at least 6 hour despite diuretic use 
3 
b. Laboratory findings suggestive of LCOS: persistently elevated lactate (>2 mmol/L), metabolic 
4 
acidosis with an increase in the base deficit (>4 mmol/L) for at least 6 hr consecutively.  
5 
c. Vasoactive-inotropic score (VIS) ≥ 20 
6 
d. Any unplanned surgical reinterventions, cardiac arrest, or utilization of extracorporeal membrane 
7 
oxygenator (ECMO) within 48 hours 
8 
e. Left ventricular fraction less than 50% by echocardiography  
9 
The LCOS-related outcome will include both anatomical LCOS and physiological LCOS that caused by 
10 
CPB 
11 
- Vasoactive-Inotropic Score (VIS) based on Belleti A, et al17 which is summation of dopamine dose 
12 
(mcg/kg/min) + dobutamine dose (mcg/kg/min) + 100 x epinephrine dose (mcg/kg/min) + 10 x milrinone 
13 
dose (mcg/kg/min) + 100 x norepinephrine dose (mcg/kg/min) + 10000 x vasopressin dose (U/kg/min) 
14 
+ 50 x levosimendan dose (mcg/kg/min) + 20 x methylene blue dose (mg/kg/h) + 10 x phehylephrine 
15 
dose (mcg/kg/min) + 10 x terlipressin dose (mcg/min) + 0.25 x angiotensin II dose (ng/kg/min) 
16 
- Acute kidney injury (AKI) based on KDIGO guideline 201218 defined AKI as any of following: increased 
17 
in SCr by ≥ 0.3 mg/dL within 48 hours, or increased in SCr to ≥ 1.5 times baseline, which is known 
18 
or presumed to have occurred within the prior 7 days, or urine volume < 0.5 mL/kg/h for 6 hours  
19 
- 28 ventilator free day (VFDs) and 28 ICU free day (IFDs): the number of days those patients were alive 
20 
and free from invasive ventilator or ICU stay within 28 days by counting the day of first operative night 
21 
as the first day. VFDs and IFDs will be counted as zero in non-survivor patients.  
22 
9.6.2. Independent variables: AVCO2, ScvO2, lactate, inflammatory markers at 0, 6, 12, and 24 hour after 
23 
operation with additional inflammatory markers at pre-operative stage 
24 
9.6.3. Potential confounder variables: age, gender, risk stratification for cardiac surgery (RACHS score), 
25 
nutritional status, duration of bypass time or aortic clamp time 
26 
9.6.4. Methods to minimize bias during study: we will blind the result of inflammatory markers to attendant 
27 
physician by sending blood sample to research lab which will not be reported in HIS system. Blood 
28 
sample collection and processing time will be fixed to ensure laboratory quality of the specimen and 
29 
its interpretation. 
30 
 
31 
9.7. 
Study procedure(s)/stage(s) 
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1 
1. Researcher will introduce research project verbally to cardiac pediatrics patient or their legal guardians 
2 
at cardiac outpatient clinic when he/she are scheduled to have cardiopulmonary bypass surgery at 
3 
Songklanagarind Hospital. Researcher will later request patient or legal guardians to sign the inform 
4 
consent when he/she is admitted in hospital 24 hours in advance.  
5 
2. If patient has already been admitted in hospital for any reason and have schedule for surgery, 
6 
researcher will inform patient or legal guardians 48 hours in advance. 
7 
3. Preoperative blood sample 1.5 mL will be collected for inflammatory markers level at the same time 
8 
when patient has intravenous access preparing for NPO or other preoperative blood sample. 
9 
4. Patient goes on open heart cardiac surgery and will be admitted directly to pediatric intensive care 
10 
unit (PICU) for postoperative care. 
11 
5. Blood sample for blood gas 0.3 mL for each central line catheter and arterial line catheter and 
12 
inflammatory markers 1.5 mL drawn from arterial line will be collected at 0, 6, 12, and 24 hours after 
13 
PICU arrival. Arterial and venous blood gas are accepted if samples are collected within 5 minutes of 
14 
each other. We allow time gap for collecting blood +/- 1 hr from schedule due to unpredictable ICU 
15 
occupy.  
16 
6. Attending physician provides standard care for post cardiac operation. The decision of treatment by 
17 
attending physician will not be involved by researchers. Inflammatory markers results will be reported 
18 
after patient is discharged from hospital to minimize influence of result to physician’s decision on 
19 
treatment. 
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7. Cardiologist will perform echocardiography to evaluate left ventricular function and anatomical defect 
1 
that could mimic signs of LCOS within 48 hours postoperatively.  
2 
8. Researcher prospectively collects postoperative variables including hemodynamic variables and 
3 
therapeutic interventions and patient’s outcome.  
4 
9. The primary study endpoint is poor outcome related to LCOS. The secondary endpoints are 28-day 
5 
ventilator free day, ICU free day, deaths and correlation of AVCO2 with other cardiac output surrogates 
6 
(AVO2, ScvO2 and arterial blood lactate). 
7 
10. If either central line or arterial line catheter are displaced before 24-hour, remaining data will be 
8 
recorded as missing data. 
9 
Describe procedures/process of the study. Show how research methodology in the study is different from 
10 
the routine practice? 
11 
Processes which are routine practice 
Processes which are research 
1. Pre- operative lab sampling; CBC, 
Coagulogram, electrolyte, group match for 
blood component  
1.  Adding inflammatory markers to pre-
operative lab 
2. Serial ABG sampling q 2-6 hr depend on 
severity of patient 
3. Serial VBG sampling q 24 hr  
2. Extra 2 blood sampling for VBG ( 0. 3 mL 
each) 
3. Mandatory blood sampling q 6 hr x 5 times 
for inflammatory markers (1.5 mL each) 
 
12 
9.8. 
Study instrument(s) and outcome measurement(s) 
13 
- Blood sample for blood gas analysis 0.3 mL will be draw from arterial line and central venous catheter 
14 
each with different time less than 5 minutes. The arterial and venous gas will be analyzed by ABL800 
15 
Basic (Radiometer, Copenhegen, Denmark) which located in PICU  
16 
- Blood sample for inflammatory markers 1. 5 mL will be collected into 3 mL vacutainers without 
17 
anticoagulant. Collected blood will be kept on room temperature and sent to division of immunology and 
18 
virology within 3 hours after collecting. Samples will be centrifuged at 500 x g for 15 minutes at 4˚C. 
19 
Supernatant will be transferred to a clean polypropylene tube. Separated serum will be aliquot into 
20 
cryogenic vial and stored at -80˚C until analysis.  
21 
- Serum cytokines (TNFα, IL-1β, IL-6, IL-8, IL-10) will be quantified in serum using multiplex immunoassays 
22 
(Bio-Plex Pro Humam Screening Panel 5plex XPLEX, Bio-Rad, California, USA). The plate will be read 
23 
on Bio-Plex®200 array reader (Bio-Rad, California, USA) and analyzed using Bio-Plex Manager™ 
24 
software. Sample will be run in duplicated and cytokine level will be quantified via comparison to standard 
25 
curve. 
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9.9. 
Data collection methodology 
1 
- Data record form consists of 5 parts: patient’s profile, characteristic of cardiac disease, intra- and post-
2 
operative intervention, laboratory values at 4 different time points, and PICU outcome. Researcher will 
3 
collect data via electronic medical records, nursing record form, and blood gas record sheet of each 
4 
participant.  
5 
9.10. Data management 
6 
- All of data will be collected in record form before putting in Epidata program. Study codes will be used on data 
7 
collection and data document instead of hospital number of patients. 
8 
9.11. Statistical analysis  
9 
Descriptive part:  
10 
- For continuous data (i.e., AVCO2, ScvO2, lactate, inflammatory markers, and others), we will use mean 
11 
(±SD) in normal distribution and median (±IQR) in non-normal distribution. We will use percentages for 
12 
categorical data (i.e., LCOS-related poor outcome).  
13 
Analytic part:  
14 
- Two means of the continuous outcomes will be compared using t-test or Mann Whitney U test. Two or 
15 
more proportions of the categorical outcomes will be compared using Chi-square or Fisher-exact test.  
16 
- We will apply the pairwise correlation analysis among independent variables: AVCO2, lactate, ScvO2, 
17 
inflammatory markers with time lagged factor. 
18 
- For primary objective, we will calculate and compare the accuracy of prediction of LCOS-related poor 
19 
outcome between AVCO2 and traditional bedside surrogates, using diagnostic test indices (i.e., sensitivity, 
20 
specificity, predictive values).  
21 
- According to secondary objectives, Cox proportional hazard model will be conducted to examine the 
22 
association between LCOS-related outcomes and other variables. Potential confounders (i.e., age, gender, 
23 
RACHS score, nutritional status, duration of bypass time or aortic clamp time) were included in the initial 
24 
model. Then, backward stepwise refinement was performed. Statistical significance was considered when 
25 
the p-value is less than 0.05. 
26 
- Area under the Receiver Operating Characteristic (ROC) to evaluate predictability of AVCO2 compare with 
27 
other parameters. 
28 
- Sensitivity analysis in patient who has physiological LCOS-related outcome. 
29 
- Subgroup analysis between children who undergone univentricular repair and biventricular repair  
30 
 
31 
10. Ethical consideration 
32 
10.1. 
Possible risks/effects in the study, including preventive and alleviation measures 
33 
- According to protocol of this study, the patients might be at risk of infection from collecting blood from 
34 
arterial line and central venous catheter. However, expertise ICU nurses practically perform blood 
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collection in sterile technique. If patient develops catheter-related blood stream infection, empirical 
1 
antibiotics will be given immediately. 
2 
- Patient will be at risk of anemia. According to Ethics committee guideline, amount of blood drawn from 
3 
patient will not be over the maximum volume for patient’s body weight and patient’s Hb must be more 
4 
than 10 g/dL at the time of blood drawing. Packed red cell will be given if patient’s Hb is less than 10 
5 
g/dL in standard care 
6 
10.2. Describe the process/ system for assuring confidentiality and the privacy of the research 
7 
participants/communities 
8 
Study codes will be used on data collection and data document instead of hospital number. Subject 
9 
information will be stored securely in the computer and only researcher can access through data. 
10 
10.3. Benefits of the study for participants and the community/country including how findings of the 
11 
study use for strengthening community. 
12 
Since there are limitation of using traditional bedside surrogates (serum lactate, ScvO2 and AVO2) to 
13 
predict LCOS in children who undergone CPB, this new bedside surrogate (AVCO2) might be another 
14 
bedside tool to detect post-operative LCOS earlier in order to improve outcome.  
15 
10.4. Informed consent process: Process/method of invitation the participants to participate in the 
16 
research, such as personal contact, referral from other(s), brochure, and announcement, etc.  
17 
- Researcher will introduce research project verbally to cardiac pediatrics patient or their legal 
18 
guardians at cardiac outpatient clinic when he/she are scheduled to have cardiopulmonary bypass 
19 
surgery at Songklanagarind Hospital and give consent form to legal guardians to sign. Researcher 
20 
will later request collect the inform consent when he/she is admitted in hospital 24 hours in 
21 
advance.  
22 
- If patient has already been admitted in hospital for any reason and have schedule for surgery, 
23 
researcher will inform patient or legal guardians 48 hours in advance. 
24 
10.5. Procedure specifying for research participant withdrawal from the study 
25 
- Blood sample taking will be ceases immediately after participant/legal guardians withdrawn from 
26 
the study  
27 
- Data collected from a withdrawn patient will be used in the study analysis. Data after patient 
28 
withdraw will be inserted as missing data. 
29 
10.6. Clearly indicate person(s) responsible for payment for treatment of complications and adverse 
30 
effects 
31 
There is no any intervention or therapeutic trial in this study.  
32 
10.7. Compensation for research participant 
33 
 Yes, please provide detail:  
 
 
 
 
 
 
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 No, please provide reasons: patient does not have to spend extra time or any effort during the 
1 
research, so there is no compensation will be provided in this study 
2 
10.8. Does the study involve biological specimen collection? If yes, also explain how the investigator 
3 
manages the leftover specimen. 
4 
The study will collect additional total 8.1 mL of blood for inflammatory mediators (1.5 mL each x 5 
5 
times for inflammatory markers and extra blood sampling 0.3 mL x 2 times for VBG analysis during 
6 
study period). After complete analysis, leftover specimen will be discarded immediately.  
7 
10.9. Research project with special ethical consideration (if applicable) 
8 
11. Limitation(s) and barrier(s) of the study (If applicable) and plans for mitigation 
9 
- The time of blood sampling might be inaccurate as schedule. The protocol allows the time gap 1 hour from 
10 
schedule to be more flexible for ICU nurse. 
11 
 
12 
12. Time schedule of the study 
13 
Duration of the study: From August 2021 to April 2023 Total time: 21 months  
14 
Activity 
Jun-Dec 2021 
Jan-Dec 2022 
Jan-Sep 2023 
1. Proposal submission for 
EC 
Jun-Aug 2021  
2. Data collection 
                              Aug 2021 – Apr 2023 
3. Data analysis 
                                                                             Jan-Apr 2023  
4. Manuscript writing 
                                                                              Apr-Jun 2023  
5. Presentation to faculty 
                                                                                     Sep 2023   
 
15 
13. Budget detail of the study 
16 
 
 Funded by: Research fund, Faculty of Medicine, Prince of Songkla University 
17 
 
Budget amount:  
 
18 
 
 Expecting funded from:  
 
19 
 
Budget amount:  
 
20 
 
 Private fund 
21 
 
Budget amount:  
 
22 
 
23 
Cost category 
Cost 
Payment for laboratory technician who centrifuge blood sample as 
protocol 20 baht/1 blood sample  
3,200 baht  

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= 20 baht x 5 times x 20 participants  
 
Equipment 
Multiplex immunoassays (Bio-Plex Pro Humam Screening Panel 5plex 
XPLEX, Bio-Rad, Californias, USA)  
= 87,205 x 2 plate 
174, 410 baht 
Grand total 
177,610 baht  
 
1 
14. Expected outcomes of the study 
2 
Publication in international journal (Scopus, pubmed) and oral/poster presentation in international conference. 
3 
15. References 
4 
1. Shekerdemian L. Perioperative manipulation of the circulation in children with congenital heart disease. Heart. 
5 
2009;95(15):1286-96. 
6 
2. Wernovsky G, Wypij D, Jonas RA, et al. Postoperative course and hemodynamic profile after the arterial switch 
7 
operation in neonates and infants. A comparison of low-flow cardiopulmonary bypass and circulatory arrest. 
8 
Circulation. 1995;92(8):2226-35. 
9 
3. Rhodes LA, Erwin WC, Borasino S, et al. Central venous to arterial CO2 difference after cardiac surgery in infants 
10 
and neonates. Pediatr Crit Care Med. 2017;18(3):228-33. 
11 
4. Moussa MD, Durand A, Leroy G, et al. Central venous-to-arterial PCO2 difference, arteriovenous oxygen content 
12 
and outcome after adult cardiac surgery with cardiopulmonary bypass: A prospective observational study. Eur J 
13 
Anesthesiol. 2019;36(4):279-89. 
14 
5. Lamia B, Monnet X, Teboul JL. Meaning of arterio-venous PCO2 difference in circulatory shock. Minerva Anestesiol. 
15 
2006;72(6):597-604. 
16 
6. Furqan M, Hashmat F, Amanullah M, Khan M, Durani HK, Haque A. Venoarterial PCO2 difference: a marker of 
17 
postoperative cardiac output in children with congenital heart disease. J Coll Physicians Surg Pak.2009;19:640-3.  
18 
7. Akamatsu T, Inata Y, Tachibana K, et al. Elevated central venous to arterial CO2 difference is not associated with 
19 
poor clinical outcomes after cardiac surgery with cardiopulmonary bypass in children. Pediatr Crit Care Med. 
20 
2017;18(9):859-62. 
21 
8. Guinot PG, Badoux L, Bernard E, et al. Central venous-to-arterial carbon dioxide partial pressure difference in patients 
22 
undergoing cardiac surgery is not related to postoperative outcomes. J Cardiothor Vasc Anesth. 2017;31(4):1190-6. 
23 
9. Habicher M, von Heymann C, Spies CD, et al. Central venous-arterial pCO2 difference identifies microcirculatory 
24 
hypoperfusion in cardiac surgical patients with normal central venous oxygen saturation: a retrospective analysis. J 
25 
Cardiothor Vasc Anesth. 2015;29(3):646-55. 
26 

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10. Chen T, Pan T, Luo X, et al. High central venous-to-arterial CO2 difference is associated with poor outcomes in 
1 
patients after cardiac surgery: a propensity score analysis. Shock. 2019;52(6):583-9. 
2 
11. Zante B, Reichenspurner H, Kubik M, et al. Increased admission central venous-arterial CO(2) difference predicts 
3 
ICU-mortality in adult cardiac surgery patients. Heart Lung. 2019;48(5):421-7. 
4 
12. Huette P, Beyls C, Mallat J, et al. Central venous-to-arterial CO(2) difference is a poor tool to predict adverse 
5 
outcomes after cardiac surgery: a retrospective study. Can J Anesth. 2021;68(4):467-76. 
6 
13. Allan CK, Newburger JW, McGrath E, et al. The relationship between inflammatory activation and clinical outcome 
7 
after infant cardiopulmonary bypass. Anesth Analg. 2010;111(5):1244-51. 
8 
14. Carmona F, Manso PH, Vicente WV, et al. Risk stratification in neonates and infants submitted to cardiac surgery 
9 
with cardiopulmonary bypass: a multimarker approach combining inflammatory mediators, N-terminal pro-B-type 
10 
natriuretic peptide and troponin I. Cytokine. 2008;42(3):317-24. 
11 
15. Drennan SE, Burge KY, Szyld EG, et al. Clinical and laboratory predictors for the development of low cardiac output 
12 
syndrome in infants undergoing cardiopulmonary bypass: a pilot study. J Clin Med. 2021;10(4). 
13 
16. Ranucci M, Isgro G, Carlucci C, Torre TD, Enginoli S, Frigiola A, et al. Central venous oxygen saturation and blood 
14 
lactate levels during cardiopulmonary bypass are associated with outcome after pediatric surgery.  Crit Care. 
15 
2010;14:R149.  
16 
17. Belletti A, Lerose CC, Zangrillo A, et al. Vasoactive-inotropic score: evolution, clinical utility, and pitfalls. J 
17 
Cardiovascthor Vasc Anesth. 2020. 
18 
18. Kellum JA, Lameire N. Diagnosis, evaluation, and management of acute kidney injury: a KDIGO summary (Part 1). 
19 
Crit Care. 2013;17(1):204. 
20 
 
21 
We, the principal investigator and co-investigators listed and signed below, certify that we will adhere strictly to the 
22 
information provided in the research protocol. We hereby certify that we will start our study only after the certification 
23 
of approval by Human Research Ethics Committee, Faculty of Medicine, Prince of Songkla University. 
24 
 
25 
 
26 
 
( 
) 
Date……………………… 
 
(Pharsai Prasertsan M.D.) 
Date 5 Nov 2023 
Adviser 
Principal Investigator 
 
 
 
(Pornnicha Chaiwiriyawong, M.D.) 

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Date…5 Nov 2023 
Sub-investigator 
 
                (Jirayut Jarutach, M.D.) 
    Date5 Nov 2023 
Sub-investigator 
 
 
(Pongsanae Duangpakdee, M.D.) 
Date5 Nov 2023 
Sub-investigator 
 
 
(Polathep Vichitkunakorn, M.D., Ph.D.) 
Date…5 Nov 2023 
Sub-investigator 
 
 
(Smonrapat Surasombatpattana, Ph.D.) 
Date5 Nov 2023 
Sub-investigator 
 
 
           (Kanokpan Ruangnapa, M.D.)  
Date…5 Nov 2023 
Sub-investigator 
 
                   
 
              (Kantara Saelim, M.D.)  
Date…5 Nov 2023 
Sub-investigator 
 
 

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Signature of authorized person/institution 
 
 
 
( 
) 
Date……………………… 
Head of Department /Unit 
 
1 
 
2 
 
3