Base excess and lactate as prognostic indicators for patients admitted to intensive care

Abstract

Objective: To examine whether values of arterial base excess or lactate taken on admission to a general intensive care unit indicate prognosis, and whether this can be used as a screening tool for future intensive care admissions. Design: Observational study. Setting: University teaching hospital general adult intensive care unit. Patients: 148 consecutive patients admitted to the intensive care unit. Interventions: Arterial blood samples were obtained on admission to the intensive care unit and 24 h following admission. Measurements and results: Arterial base excess and lactate concentrations were measured from the blood samples. Both base excess and arterial lactate samples on admission have good prognostic abilities (area under the curve on receiver operator characteristic analysis of 0.73, 0.78, respectively). The value of base excess on admission with the best predictive ability was a base excess more negative than -4 mmol/l, and the corresponding value for lactate was greater than 1.5 mmol/l. The combination of these two markers on admission to the intensive care unit led to a sensitivity of 80.3% and a specificity of 58.7% for mortality. The achievement of this combination was associated with an increased mortality (50.6% vs. 15%, p < 0.0001), older age (70 vs. 61.5 years, p < 0.05), a greater requirement for inotropic support (30.9% vs. 4.5%, p < 0.0001) and higher organ failure scores both on admission and for the subsequent 24 h. Conclusions: Both base excess and lactate, or the combination of the two, can be used to predict outcome in patients admitted to the intensive care unit. These variables could be utilized to identify patients who have a high risk for mortality and thus who should be admitted to the intensive care unit.