# Is There an Effect of Initial and 24-Hour Blood Gas Lactate and Methemoglobin Levels on Predicting Mortality of Patients in the Intensive Care Unit?

## TL;DR

This study finds that initial and 24-hour lactate levels are linked to ICU patient mortality, while methemoglobin levels are not.

## Contribution

The study demonstrates lactate clearance as a novel predictor of mortality in ICU patients, contrasting with methemoglobin's lack of prognostic value.

## Key findings

- Lactate levels significantly decreased from admission to 24 hours (p = 0.004).
- Lactate clearance was significantly lower in deceased patients compared to survivors (p = 0.037).
- Methemoglobin levels showed no significant association with mortality (p > 0.05).

## Abstract

In intensive care units (ICUs), serum lactate and methemoglobin (metHb) levels are considered significant biomarkers for predicting mortality in critically ill patients. This study investigates the relationship between lactate and metHb levels in blood gas analyses at admission and 24 h later, as well as their association with mortality in ICU patients. The study was conducted retrospectively between March and December 2022 at Adıyaman Training and Research Hospital, evaluating 114 patients, with statistical analyses performed on the collected data. The results indicated a statistically significant decrease in lactate levels between admission and 24 h after (p = 0.004). However, no significant change was found in metHb levels (p > 0.05). Lactate clearance was significantly lower in deceased patients compared to survivors (p = 0.037), whereas metHb clearance showed no statistically significant association with mortality. Lactate is highlighted as a key indicator of tissue hypoxia and plays a critical role in managing critically ill patients. Elevated lactate levels are associated with impaired oxygenation and worse prognoses. The literature consistently supports the association between high lactate levels and increased mortality in conditions such as sepsis and hemorrhagic shock. Similarly, this study confirms the prognostic value of lactate, particularly in the early phases of ICU admission. In contrast, metHb levels were not found to significantly impact mortality. Although some studies suggest a potential role of metHb as a biomarker for oxidative stress in inflammatory diseases, this relationship was not supported by the current findings. In conclusion, serum lactate levels serve as a crucial tool for mortality prediction and patient management in ICUs, while metHb levels have limited prognostic value. These findings suggest that greater emphasis should be placed on lactate monitoring in the management of critically ill patients.