Which Lactate is Most Important for Prediction of Survival on VA ECMO?

Abstract

Poor prognostic significance of elevated serum lactate in patients who are started on ECMO support is widely known. Typically, serial lactate measurements are obtained. our primary objective was to study the predictive utility of lactate measured at different points of time. We performed a retrospective chart review with collection of clinical and laboratory data. Lactic acid was collected before initiating ECMO support and then on day 1, 3, 5, and 10 while on ECMO. Outcomes were defined as survival to weaning and survival to discharge.Comparison of these lactate levels to identify which one is superior in predicting outcomes was performed using the Hanley and McNeil method as implemented in the MedCalc software. Out of total of 238 patients who received VA ECMO, 129 (54.2%) survived ECMO and 98 (41.2%) were discharged alive. Patient successfully weaned from ECMO had a significantly lower lactic acid level pre-ECMO (P=0.001), at day 1 (P<0.001), day 3 (P<0.001) and day 5 (P=0.001), compared with those who were not successfully weaned. Also, patients who were discharged alive had significantly lower lactic acid pre-ECMO (P=0.007), at day 1 (P<0.001), day 3 (P=0.001) and day 5 (P=0.001), compared with those who died in-hospital. We have investigated the association of magnitude in reduction of lactic acid from pre-ECMO to day 1 and pre-ECMO to day 3 on study outcomes. There was no association between the magnitude of reduction of lactate from pre-ECMO to day 1 on successful ECMO weaning (P=0.121) and discharge alive (P=0.127). Similarly, there was no association between the magnitude of reduction of lactate from pre-ECMO to day 3 (P=0.418) on successful ECMO weaning and discharge alive (P=0.671). Day 3 lactic acid was superior to pre-ECMO lactic acid (P=0.007), lactic acid reduction from pre-ECMO to day 1 (P=0.0125), and from pre-ECMO to day 3 (P=0.0313). The reduction of lactic acid from pre-ECMO to day 1, and pre-ECMO to day 3 was not superior to any absolute value at either pre-ECMO, days 1 or 3. With regards to discharge alive, lactic acid at ECMO day 3 is superior to pre-ECMO lactic acid (P=0.0385), lactic acid reduction from pre-ECMO to day 1 (P=0.0177) and from pre-ECMO to day 3 (P=0.0361). The absolute level of lactic acid while on ECMO support is more important for prognosis that a pre-ECMO level or the magnitude of decline from pre-ECMO to on-ECMO level.