Despite identification of prognostic markers of cardiogenic shock (CS), few markers demonstrate suitability as therapeutic targets that can be used to guide therapeutic decisions. Lactate clearance is a potential treatment target, but its role in guiding CS management has not been defined. In this systematic review and meta-analysis, we compared lactate clearance in CS survivors versus non-survivors.
METHODS AND RESULTS
In December 2020 we performed a systematic search of studies evaluating survival and blood lactate levels in patients with CS. We reviewed the mean difference in lactate clearance at 8-, 12-, and 24-hours between survivors and non-survivors. The results were pooled and a meta-analysis was performed using a random effects model comparing the mean difference in lactate clearance between survivors and non-survivors. We screened 3,150 titles and abstracts and reviewed the full text of 123 studies. Eleven studies were selected for inclusion with a total of 1,585 patients. The time-to-mortality rates included ICU mortality (N = 1), in-hospital mortality (N = 4), and 30-day mortality (N = 6). The median sample size was 87 (interquartile range [IQR] 43-139) and the median mean patient age was 56.2 years (IQR 54-57.5). Lactate levels were evaluated at 8 hours in 7 studies and at 24 hours in 9 studies. In studies that monitored lactate levels at 8 hours, the median percentage lactate clearance was 21.9% (IQR 14.6-42.1%) and 0.6% (IQR -3.7-14.6%) in survivors and non-survivors, respectively. When pooled, the mean difference in percentage lactate clearance at 8-hours was 17.3% (95% CI 11.6-23.1%; P < 0.001). Similarly, the mean percentage lactate clearance at 24-hours ranged between 50-80% (median 60.7%, IQR 58.1-76.3%) in survivors, and between, nh69.7-70% (median 40.3%, IQR 30.2-55.8%) in non-survivors. When pooled, the mean difference in 24-hour lactate clearance between survivors and non-survivors was 27.9% (95% CI 14.1-41.7%; P < 0.001). There was no statistically significant evidence of heterogeneity between studies that reported 8-hour lactate levels (I2 = 0%); however, significant statistical heterogeneity was noted between studies reporting 24-hour lactate levels (I2 = 78%).
Lactate clearance in patients with CS is a useful prognosticator of mortality. The absence of a relative reduction in lactate within the first 8 hours of treatment is associated with an increased risk of death. Prospective studies with management protocols designed to target lactate clearance are needed to verify this assumption.
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