One of the most used methods to evaluate patients with a high risk not responding to clinical treatment is the measurement of blood levels of lactic acid (LA). The objective of this study was to compare the sensitivity and specificity of an LA test for capillary and venous blood with LA test for arterial blood in a population of patients with tissue hypoperfusion and to evaluate the time needed for each test.

The following factors were evaluated: the performance of venous and capillary LA in relation to arterial LA, and the time needed to elicit each method from patient admission to mortality according to initial LA.

Seventy-nine patients with a median age of 58 years were admitted. The area under the curve for capillary LA was 82% (95% confidence interval [CI], 73-91). The best cutoff point was 2.35, with a sensitivity of 81% (95% CI, 65-90) and a specificity of 70% (95% CI, 53-83). The average time from patient admission until arterial, venous, and capillary LA values were obtained was 112, 117, and 77 minutes, respectively. The patients who died within 3, 30, and 60 days showed an average arterial LA of 5.9, 1.9, and 2.2, respectively.

The utilization of capillary and venous LA is an effective method of evaluation and risk stratification for patients with different degrees of tissue hypoperfusion. The time needed to elicit capillary LA proved much faster with respect to arterial and venous LA.