To investigate the diagnostic value of arterial lactate monitoring in predicting the prognosis of hospital acquired pneumoni (HAP) for 30 days.

The clinical data of 71 consecutive patients diagnosed as HAP admitted in Xinqiao Hospital, Army Military Medical University from January 2016 to December 2017 were analyzed, retrospectively. The arterial lactate data were collected for consecutive 5 days after diagnosis as HAP, while the pneumonia severity index (PSI) score was taken as the first 24 hours’ physiological parameters after diagnosis. According to the prognosis of survival within 30 days after diagnosis as HAP, the patients were divided into survival group (32 cases) and death group (39 cases). The change trend of arterial lactate, lactate clearance and lactate clearance rate were analyzed by repeated metric analysis. The effect of arterial lactate, lactate clearance and lactate clearance rate on the 30 days prognosis of HAP were compared by ROC curve. The difference in the mortality rates were compared according to the lactate peak within 5 days, which were divided into < 2.0 mmol/L, ≥ 2.0 mmol/L and ≥ 4.0 mmol/L groups; the correlation between lactate peak and PSI score was calculated by double variable linear correlation analysis.

In survival group, as time going on the lactate decreased, lactate clearance and lactate clearance rate increased; in death group, as time going on the lactate increased, lactate clearance and lactate clearance rate decreased. ROC curve showed that lactate could be used to evaluate the prognosis, but not the lactate clearance and lactate clearance rate. The areas under lactate ROC curve of the first day, second day, third day, fourth day, fifith day, the lactate peak within 5 days were 0.67, 0.71, 0.77, 0.71, 0.70 and 0.74, respectively. The mortality rates of the peak value of lactate within 5 days, cases in < 2.0 mmol/L group, ≥ 2.0 mmol/L group and ≥ 4.0 mmol/L group were 20.00%, 64.29% and 78.95%, respectively, with significant difference (χ² = 13.27, P = 0.00). There was a close correlation between the lactate peak and the PSI score (r = 0.41, P = 0.00).

The changes of arterial lactate were different for different prognosis of HAP patients. The value of arterial lactate was higher than that of lactate clearance and lactate clearance rate for evaluating HAP prognosis. The higher the arterial lactate, the greater risk of death. Arterial lactate peak was closely related to PSI score.