Pre-operative tonometry is predictive for mortality and morbidity in high-risk surgical patients

Abstract

Objective: To determine whether a) pre-operative measurement of gastric intramucosal pHi is predictive for mortality and morbidity in high-risk surgical patients and b) peri-operative improvement of global oxygen delivery (DO₂) with fluids and dopexamine leads to increased gastric pHi and c) either improved global perfusion or improved splanchnic perfusion is related to the prevention of multiple organ failure (MOF).

Design: Retrospective analysis of a double-blind, placebo-controlled, randomised study.

Setting: General intensive care units from 14 hospitals.

Patients: Two hundred eighty-six high-risk surgical patients.

Interventions: Swan-Ganz and tonometer catheter placement; patients were stabilised pre-operatively using fluids, blood and/or oxygen to preset goals before receiving placebo or two doses of dopexamine (0.5 or 2.0 µg·kg·min) peri-operatively.

Measurements and results: Haemodynamic assessment (including DO₂ and oxygen consumption (VO₂)) was performed together with measurement of gastric mucosal pHi pre-operatively and directly, 2, 6, 12, 24 and 36 h post-operatively. Retrospectively, patients were divided pre-operatively into two sub-groups based on the optimal cut-off value for mortality of the first pHi measurement after induction of anaesthesia as calculated by a receiver operator characteristic (ROC) curve analysis – low pHi group (<7.35) and normal pHi (≥7.35). Mortality in the low pHi, was higher than in the normal pHi, group (16.8 vs 2.3%; p=0.0001). In the normal pHi group dopexamine, which was given prior to the first pHi measurement, had no effect on pHi, while DO₂ increased significantly. In this group MOF score and number of patients with MOF remained similar for the treatment sub-groups. In the low pHi group gastric pHi increased significantly during dopexamine infusion (p=0.008), despite the lack of an increase in DO₂ and VO₂. In this group the MOF score and the number of patients developing MOF decreased significantly with the use of dopexamine (p=0.04). In both groups bicarbonate levels remained similar for the treatment sub-groups.

Conclusions: In high-risk surgical patients pre-operative measurement of pHi was predictive for mortality. The peri-operative response of pHi to dopexamine seemed to be dependent on pre-operative gastric pHi.