Increased arterial lactate upon hospital admission is independently associated with 30-day in-hospital mortality among non-intensive care unit (ICU) patients with acute respiratory failure related to COVID-19, researchers reported in Therapeutic Advances in Respiratory Disease.

High lactate levels are a stress response that has been found to predict stress in patients critically ill with sepsis. Researchers therefore investigated whether arterial lactate levels upon hospital admission in patients with COVID-19-related acute respiratory failure were predictive of negative outcomes.

The observational study enrolled patients from 2 centers in Italy who had a diagnosis of COVID-19 confirmed by real time-polymerase chain reaction testing as well as pneumonia as detected by chest X-ray, computed tomography, or lung ultrasonography. Data from arterial blood gas (ABG) analysis, including pH, lactate, pO2, pCO2, and FiO2, were obtained, and lactate of at least 2.0 mmol/L was considered increased. The outcome was in-hospital mortality at 30 days.

A total of 206 patients were included. Their median age was 71 (interquartile range [IQR], 57-81) years and 34% were female.

[H]yperlactatemia at admission was independently associated with in-hospital death at 30 days. Moreover, increased lactate levels were associated with the severity of respiratory failure.

Upon admission, 14.6% of participants had lactate levels of at least 2.0 mmol/L. Age and the ratio of arterial oxygen partial pressure to fractional inspired oxygen (pO2/FiO2) were independently associated with increased lactate levels.

A total of 57 patients (27.7%) had in-hospital mortality at 30 days. Death occurred in 22.3% of patients with normal lactate at admission and in 56.7% of those with increased lactate at admission. The median lactate level was 1.0 (IQR, 0.8-1.3) mmol/L among survivors at 30 days and 1.3 (IQR, 1.0-2.1) mmol/L in participants who died during their hospital stay (P <.001).

Lactate levels of at least 2 mmol/L and at least 4 mmol/L upon admission were independently associated with in-hospital mortality at 30 days in multivariate analysis (2 mmol/L: hazard ratio [HR], 2.53; 95% CI, 1.29-4.95; P =.0066; 4 mmol/L: HR, 8.10; 95% CI, 1.88-34.87; P =.0050). This association also occurred for pO2/FiO2 <100, chronic obstructive pulmonary disease, and age. An increase in lactate levels at 24 hours was not associated with death (HR, 1.37; 95% CI, 0.42-4.49; P =.6045).

The area under the curve for lactate levels upon admission for predicting 30-day in-hospital death was 0.69 (95% CI, 0.61-0.77).

The association between lactate levels of at least 2 mmol/L and at least 4 mmol/L upon admission and 30-day in-hospital mortality was confirmed in patients with a pO2/FiO2 ratio of 300 mmHg or less and in those with pCO2 of 45 mmHg or less upon admission.

Study limitations include the retrospective design and low proportion of patients with a second assessment at 24 hours. Also, cutoff values for lactate levels of 2 and 4 mmol/L were based on previous studies and guidelines in patients with sepsis.

“In our study of non-ICU patients, hyperlactatemia at admission was independently associated with in-hospital death at 30 days. Moreover, increased lactate levels were associated with the severity of respiratory failure as defined according to different

respiratory indexes,” said the study authors.

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