Background and objectives: One of the greatest challenges found by the intensivists in their daily activities is tissue hipoperfusion control. Blood lactate is generally accepted as a marker of tissular hypoxia and several studies have demonstrated good correlation between blood lactate and prognosis during shock and resuscitation. The aim of this study was to evaluate the clinical utility of arterial blood lactate as a marker of morbidity and mortality in critically ill patients in the post-operative period of high risk non-cardiac surgeries.
Methods: Prospective and observational cohort study realized in an ICU of a tertiary hospital during a four month period. Demographic data of the patients submitted to high risk surgeries were collected, besides arterial lactate measures and number and type of complications in the post-operative period. To the statistic analysis was considered as significant a p < 0.05. The predictive ability of the indexes to differentiate survivors from non-survivors was tested using ROC curves. Lenght of ICU stay estimation where calculated by Kaplan Meier method.
Results: Were included 202 patients. 50.2% were female and their mean age was 66.5 ± 13.6 years. APACHE II score was 17.4 ± 3.0 and the median of MODS score was 4 (2-6). Median lenght of surgeries was 4h (3-6h). 70.7% of the surgeries were elective ones. ICU and hospital mortality were 15.6% and 33.7%, respectively. The best lactate value to discriminate mortality was 3.2 mmol/L, with sensitivity of 62.5%, specificity of 78.8% and an area under the curve of 0.7. 62.5% of patients with lactate > 3.2 did not survive versus 21.2% of survivors (OR = 2.95 IC95% 1.98- 4.38, p < 0.0001). ICU lenght of stay was greater when > 3.2 mmol/L (log rank 0.007) lactate.
Conclusions: High risk patients submitted to non cardiac surgeries and admitted to the ICU with hiperlactatemia, defined as an arterial lactate > 3.2 mmol/L, are prone to a longer ICU lenght of stay and to die.