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| ORIGINAL ARTICLE |
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| Year : 2022 | Volume
: 10
| Issue : 2 | Page : 63-67 |
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Serum lactate clearance as a predictor of outcome in infants' postcardiac surgery
Hasmukh Patel1, Nirav Parikh2, KS Ramkiran1, Prakash Sadhwani1, Ramesh Patel1, Pratik Shah1
1 Department of Cardiac Anesthesia, U.N. Mehta Institute of Cardiology and Research Center, Ahmadabad, Gujarat, India
2 Department of Cardiac Anesthesia, U. N. Mehta Institute of Cardiology and Research Centre, Civil Hospital Campus, Asarva, Ahmadabad, Gujarat, India
| Date of Submission | 11-Mar-2022 |
| Date of Decision | 17-Mar-2022 |
| Date of Acceptance | 23-Mar-2022 |
| Date of Web Publication | 12-Aug-2022 |
Correspondence Address:
Dr. Nirav Parikh
Department of Cardiac Anesthesia, U.N. Mehta Institute of Cardiology and Research Center, Ahmadabad, Gujarat
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/heartindia.heartindia_18_22
Background and Aims: Prediction of postoperative outcomes by conventional hemodynamic parameters and risk scoring systems immediately after pediatric cardiac surgery has not been found to be reliable. Trends in serum lactate value over time or serum lactate clearance were found to give better estimate. The present study aimed to find out the effect of serum lactate clearance on mortality after pediatric cardiac surgery.
Methods: Out of the 150 pediatric cardiac surgical procedures performed during the study period, 131 patients meeting inclusion criteria were enrolled in the present study. The study population was observed for lactate levels immediately postoperatively (T0) and then every 4 h for the first 24 h (T1-T6) and lactate clearance was calculated. Patient's outcomes in view of mortality, duration of mechanical ventilation, and length of intensive care unit (ICU) stay were observed.
Results: In our study, mortality was 9.23%. Median inter quartile range with Hodges-Lehmann median difference (95% confidence interval) lactate values were higher among nonsurvivors and statistically significant at T0 = (6.14 [3.43,7.34] vs. 2.50 [1.87,3.59]; 2.53 [1.02, 4.33], P ≤ 0.0001), T1 = (3.10 [2.81, 5.16] vs. 2.30 [1.73, 3.61];0.95 [0.13, 1.73], P = 0.032), T2 = (3.49 [3.03, 5.40] vs. 2.39 [1.66, 3.38];1.32 [0.48, 2.27], P = 0.004), T3 = (3.82 [2.99, 5.54] vs. 2.20 [1.58, 3.45]; 1.46 [0.50, 2.45], P = 0.003), T4 = (4.86 [3.35, 5.44] vs. 2.09 [1.42, 3.47]; 2.02 [1.09, 3.13], P ≤ 0.0001), T5 = (4.36 [3.80, 6.27] vs. 2 [1.32, 3.26]; 2.29 [1.41, 3.25], P ≤ 0.0001), and T6 = (4.12 [3.69, 5.83] vs. 1.82 [1.31, 3.15]; 2.34 [1.15, 3.21], P ≤ 0.0001). Nonsurvivors were having decreasing trend of lactate clearance which was statistically nonsignificant. Mechanical ventilation was prolonged in nonsurvivors compared to survivor (135 [202] h vs. 30 [77] h; P = 0.002); however, there was no significant difference in ICU stay (P = 0.764).
Conclusion: Poor lactate clearance and high lactate level were associated with high mortality. Serial lactate levels and decreasing trend of lactate clearance in the early postoperative period is a good predictor of postoperative outcome in pediatric cardiac surgery.
Keywords: Cardiac surgery, infants, serum lactate clearance
How to cite this article:
Patel H, Parikh N, Ramkiran K S, Sadhwani P, Patel R, Shah P. Serum lactate clearance as a predictor of outcome in infants' postcardiac surgery. Heart India 2022;10:63-7 |
How to cite this URL:
Patel H, Parikh N, Ramkiran K S, Sadhwani P, Patel R, Shah P. Serum lactate clearance as a predictor of outcome in infants' postcardiac surgery. Heart India [serial online] 2022 [cited 2023 Jun 2];10:63-7. Available from: https://www.heartindia.net/text.asp?2022/10/2/63/353733 |
| Introduction | |  |
Prediction of outcome immediately after complex cardiac surgery is difficult, as both measurement of conventional hemodynamic parameters and risk scoring systems have shown to be inadequate. Consequently, attention has focused on the use of biochemical parameters, notably serum lactate concentrations, which might reflect critical oxygen supply dependency. Arterial lactate level is reflection of the balance between lactate production and clearance.
During cardiopulmonary bypass (CPB) surgery and the critical postoperative period, patients are at risk for decreased perfusion. The resulting elevated serum lactate levels, or hyperlactatemia, may be associated with an increased risk for complications in the postoperative period. Rather than a single value, a trend in lactate values giving lactate clearance is a useful predictor of postoperative outcomes.
Although there are studies in adult patients showing lactate clearance is better for predicting mortality,[1],[2],[3] its association with postoperative outcomes has been poorly investigated in pediatric patients undergoing cardiac surgery.
The purpose of our study was to determine the clinical utility of lactate clearance as early as 4 h in the postoperative period as a predictor of mortality. We hypothesized that lactate clearance in the early postoperative period is a predictor of mortality in children undergoing elective cardiac surgery.
The primary objective was to predict mortality in pediatric cardiac surgery patients based on serum lactate clearance. The secondary objective was to observe the duration of mechanical ventilation and intensive care unit (ICU) stay.
| Methods | | |
A prospective observational study was performed on 131 infants, who underwent elective cardiac surgery on CPB from December 2019 to February 2020 at U N Mehta Institute of Cardiology and Research Center (UNMICRC) [Figure 1]. Informed consent was obtained from parents of infants. The study protocol was approved by the UNMICRC ethics committee (UNMICRC/C. ANESTHE/2019/37).
Infants with congenital heart disease and undergoing elective cardiac surgery with CPB were included in our study. The preoperative diagnosis was done by either 2D echo alone or along with computed tomography scan.
Infants with body weight <2 kg, off-pump cardiac surgery, preoperative hemodynamic instability, preoperative requirement of inotropic support, preoperative renal or liver dysfunction, systemic infection, bleeding disorder, and (extracorporeal membrane oxygenation [ECMO]) support after surgery were excluded from our study.
After surgery, all patients were transferred to the pediatric cardiothoracic recovery room (PCTRR), where all patients remained mechanically ventilated on PCV VG (Pressure Controlled Ventilation-Volume Gauranteed) mode. Patients were sedated with fentanyl infusion of 2 mcg/kg/min. Intravenous inotropic supports such as adrenaline, noradrenaline, milrinone, or vasopressin were used according to the patient's hemodynamic parameters.
Lactate levels were obtained at T0 (after shifting to PCTRR), T1 (4 h after T0), T2 (8 h after T0), T3 (12 h after T0), T4 (16 h after T0), T5 (20 h after T0), and T6 (24 h after T0). Lactate clearance was defined by ([lactate [initial] – lactate [final]]/lactate [initial] × 100%). Lactate clearance was calculated at T0-T1, T0-T2, T0-T3, T0-T4, T0-T5, and T0-T6. The duration of mechanical ventilation was defined as number of h (hours) from PCTRR admission to extubation. The duration of ICU stay was defined as number of hours between PCTRR admission and discharge. Those patients who got discharged from ICU were defined as survivors and those who could not define as nonsurvivors.
Based on the previous study,[4] we decided to take 200 sample sizes. However, during the study period (December 2019-February 2020), there was COVID-19 pandemic, so less number of surgeries were performed. We were able to collect only 150 number of patients' data. Out of that 19 surgeries were off CPB. Hence, these patients were excluded from the study, and we studied 131 patients using Raosoft Software with 95% confidence interval (CI) to achieve 80% power allowing for 5% Type I (alpha) error. The data were analyzed using software version 20 (MedCalc Software ltd, Ostend, Belgium). Chi-square test was used for qualitative data. Mann–Whitney U-test was performed on our nonparametric data based on two independent comparison groups. P < 0.05 was considered as statistically significant. Quantitative data were represented as median with interquartile range, whereas qualitative data was represented as number with percentage. Median difference with 95% CI was calculated with the help of Hodges-Lehmann test.
| Results | | |
The flow of patients during the study period was as per [Figure 1]. Out of 131 patients, 12 could not survive (mortality 9.23%). Patients' demographic and clinical characteristics are presented in [Table 1]. Types of surgeries are mentioned in [Table 2].
Serial blood lactate levels at 4 h interval in first 24 h postoperatively compared in [Table 3]. Hodges-Lehmann median difference (95% CI) lactate value were higher in nonsurvivors at all time points compared to survivors. T0 = (2.53 [1.02, 4.33], P ≤ 0.0001), T1 = (0.95 [0.13, 1.73], P = 0.032), T2 = (1.32 [0.48, 2.27], P = 0.004), T3 = (1.46 [0.50, 2.45], P = 0.003), T4 = (2.02 [1.09, 3.13), P ≤ 0.0001), T5 = (2.29 [1.41, 3.25], P ≤ 0.0001), and T6 = (2.34 [1.15, 3.21], P ≤ 0.0001).
Lactate clearance in the first postoperative day is compared in [Table 4]. Trend of lactate clearance was higher in survivor group compared to nonsurvivors group [Figure 2]. Duration of ICU stay and mechanical ventilation hours are compared in [Table 1].
| Discussion | | |
In our study, infants with poor lactate clearance trends were associated with higher mortality as well as prolonged mechanical ventilation and ICU stay. Increasing lactate levels were treated by optimizing cardiac output and systemic oxygen delivery in cardiac ICU. Despite these interventions, higher lactate level and decreasing trend of lactate clearance can predict the poor outcome in pediatric cardiac surgeries.
Hyperlactatemia is used as a predictor of morbidity, mortality, and prolonged ICU stay in sepsis, trauma patients, and patients underwent liver transplantation. Other than anaerobic metabolism by tissue hypoperfusion, hyperglycemia, exogenous beta-adrenergic agonists, dialysis with lactate-containing fluids. and insulin resistance by stress hormones and cytokines are the cause of hyperlactatemia.[5] These make limitations in interpretation of single lactate measurement. The hyperlactatemia was also proved to independent early predictor of morbidity, mortality in cardiac surgical patients.
Recently, serial lactate level has proved to more reliable prognostic index in pediatric cardiac surgery patients and poor outcome with high sensitivity and specificity.[4] Serial blood lactate measurement may be an accurate predictor of mortality or requirement of ECMO support for patients undergoing complex neonatal cardiac surgery.[6] Increased lactate levels are directly associated with increased duration of mechanical ventilation, postoperative ICU stay, and mortality in adult cardiac surgery patients.[7] An increase in lactate allows excellent insight between high-and low-risk groups for poor outcome in infants after cardiac surgery using CPB.[8]
A peak blood lactate level of 4.8 mmol/l or higher during early postoperative hours is associated with an increased risk of postoperative morbidity and mortality.[9] In our study, trend of lactate clearance over 1st 24 h in postoperative period is an indicator for discrimination between good and poor outcomes. The duration of mechanical ventilation was significantly prolonged in nonsurvivors (P = 0.002), whereas ICU stay was prolonged but statistically not significant in nonsurvivors (P = 0.764).
Patients with decreasing trend of lactate clearance in the initial postoperative period are required to prolong mechanical ventilation as well as prolong ICU stay. Low lactate clearance warrants early interventions to prevent morbidity and mortality.
Limitation of the study
Except two patients of Pulmonary Artery (PA) band with atrial septectomy, all patients in nonsurvivor group were of cyanotic heart disease. This may be contributing factor for preoperative low Spo2 (P = 0.023) and higher hemoglobin (P = 0.048) in nonsurvivor group. Complex congenital heart surgeries have prolonged CPB time compared to simple congenital heart surgeries. There was prolonged CPB time in nonsurvivor group that may be an additional factor related to higher mortality.
Future direction of the study
Change in the treatment protocol based on the recognition of decreasing trend of lactate clearance will improve outcome in infants postcardiac surgery. Although ours is a small-size study, large and multicentric studies are required to support the results. In future, we would like to study lactate clearance trend in particular cardiac surgery to avoid bias of difference in clinical characteristics between groups such as SPo2, hemoglobin, and CPB time.
| Conclusion | | |
Decreasing trend of lactate clearance and high lactate level was associated with high mortality. We found that trend of lactate clearance in the early postoperative period is a good predictor of postoperative outcome in pediatric cardiac surgery.
Ethical approval
The study involves human participants; the study has been approved by the appropriate Institutional Ethics Committee from UNMICRC, Ahmedabad(UNMICRC/C. ANESTHE/2019/37) and has been performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki. This article does not contain study performed on animals by any of the authors.
Authors' contributions
Dr. Hasmukh Patel - Design, Aquisition, Dr. Nirav Parikh- Analysis, Interpretation, Drafting Dr. K.S.Ramkiran- Aquisition,Analysis, Drafting Dr. Prakash Sadhwani,- Conceptualization, Design, Interpretation; Dr.Ramesh Patel - Design , Analysis; Mr. Pratik Shah- Data Analysis
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| References | | |
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]
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