Blood pressure and arterial lactate level are early indicators of short-term survival in human septic shock

Abstract

Objective: To identify early prognostic markers of septic shock among catheterization-derived hemodynamic and metabolic data.

Design: Prospective cohort study.

Setting: A medical intensive care unit in a university hospital.

Patients: Thirty-two consecutive patients with septic shock, separated into two groups according to short-term (10-day) evolution: 18 acute survivors and 14 fatalities.

Measurements: Usual hemodynamic and metabolic variables were measured at the onset of shock, i.e., when the catheter was inserted (T0), and 24 h later (T24). The values collected for each group at T0 and T24 and their 24-h changes were compared.

Results: On admission, no difference was found between acute survivors and eventual fatalities. After 24 h, fatalities presented with significantly lower mean arterial pressure (p <0.01), left ventricular stroke work index (p <0.05) and higher lactate levels (p <0.01) than acute survivors. Moreover, the 24-h changes of lactate and blood pressure were also of prognostic value (p <0.05). Oxygen delivery and oxygen consumption did not differ statistically between the two groups. At T24, a mean arterial pressure of less than 85 mmHg and a lactate level equal to or greater than 3.5 mmol/l were independently associated with poor survival (37.5% and 30.7%, respectively). Day 10 survival was only 12.5% when both criteria were present at T24.

Conclusions: Changes in mean arterial pressure and arterial blood lactate within the first 24 h of treatment are strong prognostic indicators of short-term survival in patients with septic shock. After 24 h of treatment, maintenance of a mean blood pressure equal to or greater than 85 mmHg correlates with survival at day 10. Data suggest that early reductions in both cardiac function and vascular tone play a determining role in the hypotension observed in fatalities. Persistence of hyperlactatemia in hypotensive patients bodes particularly ill. Blood pressure and lactate level are simple bedside parameters that can enable the clinician to identify patients with a high risk of mortality.