Point of care serum lactate levels as a prognostic marker of outcome in complex pediatric cardiac surgery patients: Can we utilize it?

A Near Real-Time Risk Analytics Algorithm Predicts Elevated Lactate Levels in Pediatric Cardiac Critical Care Patients

BACKGROUND

Postoperative pediatric congenital heart patients are predisposed to develop low-cardiac output syndrome. Serum lactate (lactic acid [LA]) is a well-defined marker of inadequate systemic oxygen delivery.

OBJECTIVES

We hypothesized that a near real-time risk index calculated by a noninvasive predictive analytics algorithm predicts elevated LA in pediatric patients admitted to a cardiac ICU (CICU).

DERIVATION COHORT

Ten tertiary CICUs in the United States and Pakistan.

VALIDATION COHORT

Retrospective observational study performed to validate a hyperlactatemia (HLA) index using T3 platform data (Etiometry, Boston, MA) from pediatric patients less than or equal to 12 years of age admitted to CICU (n = 3,496) from January 1, 2018, to December 31, 2020. Patients lacking required data for module or LA measurements were excluded.

PREDICTION MODEL

Physiologic algorithm used to calculate an HLA index that incorporates physiologic data from patients in a CICU. The algorithm uses Bayes' theorem to interpret newly acquired data in a near real-time manner given its own previous assessment of the physiologic state of the patient.

RESULTS

A total of 58,168 LA measurements were obtained from 3,496 patients included in a validation dataset. HLA was defined as LA level greater than 4 mmol/L. Using receiver operating characteristic analysis and a complete dataset, the HLA index predicted HLA with high sensitivity and specificity (area under the curve 0.95). As the index value increased, the likelihood of having higher LA increased (p < 0.01). In the validation dataset, the relative risk of having LA greater than 4 mmol/L when the HLA index is less than 1 is 0.07 (95% CI: 0.06-0.08), and the relative risk of having LA less than 4 mmol/L when the HLA index greater than 99 is 0.13 (95% CI, 0.12-0.14).

CONCLUSIONS

These results validate the capacity of the HLA index. This novel index can provide a noninvasive prediction of elevated LA. The HLA index showed strong positive association with elevated LA levels, potentially providing bedside clinicians with an early, noninvasive warning of impaired cardiac output and oxygen delivery. Prospective studies are required to analyze the effect of this index on clinical decision-making and outcomes in pediatric population.

The effect of oral triiodothyronine supplementation on lactate and pyruvate after paediatric cardiac surgery

OBJECTIVE

To determine if triiodothyronine alters lactate, glucose, and pyruvate metabolism, and if serum pyruvate concentration could serve as a predictor of low cardiac output syndrome in children after cardiopulmonary bypass procedures.

METHODS

This study was ancillary to the Oral Triiodothyronine for Infants and Children undergoing Cardiopulmonary bypass (OTICC) trial. Serum pyruvate was measured in the first 48 patients and lactate and glucose were measured in all 208 patients enrolled in the OTICC study on the induction of anaesthesia, 1 and 24 hours post-aortic cross-clamp removal. Patients were also defined as having low cardiac output syndrome according to the OTICC trial protocol.

RESULT

Amongst the designated patient population for pyruvate analysis, 22 received placebo, and 26 received triiodothyronine (T3). Lactate concentrations were nearly 20 times greater than pyruvate. Lactate and pyruvate levels were not significantly different between T3 and placebo group. Glucose levels were significantly higher in the placebo group mainly at 24-hour post-cross-clamp removal. Additionally, lactate and glucose levels peaked at 1-hour post-cross-clamp removal in low cardiac output syndrome and non-low cardiac output syndrome patients, but subsequently decreased at a slower rate in low cardiac output syndrome. Lactate and pyruvate concentrations correlated with glucose only prior to surgery.

CONCLUSION

Thyroid supplementation does not alter systemic lactate/pyruvate metabolism after cardiopulmonary bypass and reperfusion. Pyruvate levels are not useful for predicting low cardiac output syndrome. Increased blood glucose may be regarded as a response to hypermetabolic stress, seen mostly in patients with low cardiac output syndrome.

Hyperlactatemia and Patient Outcomes After Pediatric Cardiac Surgery

Elevated serum lactate level, or hyperlactatemia, is often associated with alterations in tissue perfusion, increased risk for complications in the postoperative period, and patient mortality. Measuring lactate levels is a relatively simple and noninvasive method of obtaining useful data about an impending clinical deterioration in a seemingly hemodynamically stable patient. This article evaluates the current practice of measuring lactate levels in pediatric patients after cardiac surgery and the association between these levels and patient outcomes. The article addresses periods of increased risk for decreased perfusion, the critical postoperative period, use of lactate measurements in conjunction with a risk scoring system for pre-and postoperative congenital heart disease patients, and the implications of elevated lactate levels in nursing practice.

Persistent Hyperlactatemia as the Predictor of Poor Outcome in Critically Ill Children: A Single-Center, Prospective, Observational Cohort Study

Objective  To study incidence of hyperlactatemia and its correlation with outcome in critically ill children. Design  Single-center, prospective cohort study. Setting  Eight-bedded PICU. Method  Serial serum lactate levels were measured in 140 critically ill children at 0, 12, 24, and 48 hours. Results  A total of 45% children had hyperlactatemia. Lactate levels were significantly ( p  = 0.000) higher in nonsurvivors at all intervals. Lactate levels decreased significantly ( p  = 0.000) in survivors while increased in nonsurvivors. Normalized lactate load was found to be an independent predictor of mortality ( p  = 0.023). Conclusion  Persistent hyperlactatemia serves as a possible predictor of poor outcome in critically ill children.

A profile of metabolic acidosis in patients with sepsis in an Intensive Care Unit setting

Context:

Metabolic acidosis is frequently found in patients with severe sepsis. An understanding of types of acidosis in sepsis and their evolution over the course of treatment may give us insight into the behavior of acid–base balance in these patients.

Aims:

To describe at Intensive Care Unit (ICU) admission and over the first 5 days the composition of metabolic acidosis in patients with sepsis and to evaluate and compare acidosis patterns in survivors and nonsurvivors.

Settings and Design:

A prospective study conducted at Amrita Institute of Medical Sciences, Kochi, Kerala, in the Department of Internal Medicine.

Subjects and Methods:

Seventy-five consecutive patients admitted in the medical ICU with sepsis and metabolic acidosis were assessed. Arterial blood gas and serum electrolytes were measured during the first five days of admission or until death, renal replacement or discharge supervened.

Statistical Analysis:

To test the statistical significance of the difference in mean values of different study variables at day 1 and last day between survivors and non survivors, Mann–Whitney U-test was applied. To test the statistical significance of the difference in mean changes in different study parameters from day 1 to last day, paired t-test was done in the survivor group and Mann–Whitney U-test in the non survivor group.

Results:

Regardless of survival status, on day 1 of admission, 37 had High Anion Gap metabolic acidosis (HAGMA), 21 had predominant lactic acidosis (LA), 8 had Normal anion gap metabolic acidosis (NAGMA), and 9 had both HAGMA and LA [Figure 1]. When we compared this to the last day, 25 had HAGMA, 3 had LA, 3 had both HAGMA and LA, and 22 patients had resolution of acidosis. Sixty–four patients survived for up to 5 days of admission. Fifteen of these patients underwent hemodialysis on the day of admission itself in view of HAGMA. The remaining 49 comprised of HAGMA (31), Lactic acidosis (12), and a combination (6) on day 1. On the last day in this group, 25 had HAGMA, 2 had LA, and 22 patients had resolution of acidosis. In survivors, over the observation period, changes seen were: mean pH: 7.25–7.34 (P < 0.001), mean serum bicarbonate: 13.9 mEq to 17.2 mEq (P < 0.001), and mean serum lactate: 3.18–1.9 (P = 0.002). The changes in serum albumin and pCO₂ were not significant. Eleven patients in the study population succumbed. Seven patients underwent hemodialysis on day 1 and the remaining four were followed up for more than 1 day. On day 1, 7 had lactic acidosis and 5 had HAGMA. Over the observation period, changes seen were mean pH: 7.15–7.14, mean serum lactate: 6.3–7.3 mEq.

Conclusions:

In patients with sepsis and septic shock, high anion gap metabolic acidosis is the dominant blood gas anomaly. Fall in lactate levels over the first 5 days of admission is a good prognostic marker of survival. Evolution of the blood gas profile over time suggests that a fall in lactate levels and a rise in bicarbonate levels correlate with a better outcome. The role of the anion gap as a prognostic marker holds promise and further studies are needed in this regard.