Early lactate area scores and serial blood lactate levels as prognostic markers for patients with septic shock: a systematic review

Septic shock is the main cause of morbidity and mortality in patients and second leading cause of mortality among subjects in noncoronary intensive care units. Based on the literature, elevated serum lactate levels are associated with poor outcomes in patients with septic shock, which may occur due to various reasons, such as tissue hypoxia and anaerobic metabolism. This systematic review was conducted to collect data on the lactate area and area under the curve (AUC) of serial lactate levels for the determination of the predictive values of these factors to diagnose septic shock. For this purpose, the articles published up to 2019 were searched in four databases, including Google Scholar, PubMed, Scopus, and Medline. This study was carried out based on the seven stages recommended in the Cochrane Handbook. All articles were searched using several keywords, including 'Lactate Area Score' and 'Serial Lactate Levels' in combination with 'Septic Shock'. There were a total of 14 studies mainly focused on the assessment of the lactate area and serial lactate levels in patients with septic shock. The inclusion criteria were a clear explanation of the predictive role of repeated lactate measurements in patients with septic shock, sample size larger than 50, examination on human samples, and publication in English. All case-control, prospective, and retrospective studies on human subjects assessing the predictive value of repeated lactate measurements in the diagnosis of patients with septic shock at high risk of mortality were entered in the present review. The lactate area is a new concept introduced as the sum of the AUC of serial lactate levels. This factor can determine the severity and duration of hyperlactatemia. Based on the obtained results, there was an association between the lactate area score and 28-day mortality of patients with septic shock; therefore, early lactate area score can be considered a prognostic marker for the prediction of mortality rate in these patients. There are few studies on the evaluation of the lactate area score and no more information about the prognostic ability of the lactate area score. This was the main limitation of the present study. Moreover, the lactate area is introduced as the sum of the AUC of serial lactate levels and cannot reflect the trend of serial lactate. The trend may be supported by lactate clearance but not lactate area.