Factors related to post-operative metabolic acidosis following major abdominal surgery

Metabolic acidosis is frequently observed in perioperative patients, especially those who undergo major surgery. The aim of this study was to evaluate the factors related to post-operative metabolic acidosis and to attempt to identify the clinical effect of metabolic acidosis following major abdominal surgery.

We included 172 patients admitted to a surgical intensive care unit (ICU) following major abdominal surgery. All cases were divided into either the acidosis or the normal group using immediate post-operative standard base excess (SBE). The following clinical data were retrospectively obtained from the chart and ICU database: basic clinical characteristics, operative data, type and volume of fluid infused during the operation, post-operative arterial blood gas analysis, lactate, and central venous oxygen saturation.

The predominant intraoperative fluid was either 0.9% saline or lactated Ringer's solution. The operation length, estimated blood loss, total fluid infused, total saline infused, lactate and corrected chloride were significantly higher in the acidosis group; however, central venous oxygen saturation was lower in the normal group. Among these factors, total infused saline and lactate level were independent factors related to metabolic acidosis. The comparison between the types of fluid revealed that the saline group had a significantly lower SBE, strong ion difference and higher corrected chloride. SBE was significantly correlated with lactate and total infused saline. ICU and hospital length of stay were significantly longer in the acidosis group.

Post-operative metabolic acidosis following major abdominal surgery was closely related to both hyperchloremic acidosis associated with large saline infusion and lactic acidosis caused by lactataemia.