Introduction: Mesenteric ischemia (MI) is a significant cause of morbidity and mortality in the critically ill patient. The purpose of this study was to determine the reliability of metabolic acidosis in predicting outcomes in critically ill surgical patients. Methods: We retrospectively reviewed consecutive ICU admissions from January 2010 thru June 2012 with a discharge diagnosis of MI who underwent laparotomy. Data collected included age (dichotomized at age 60 years), gender, ICU, ventilator and hospital length of stay (LOS), APACHE II, SOFA, surgical resection, BMI, discharge disposition and mortality. Markers of acidosis were dichotomized at the median admission bicarbonate (BICARB) 22 mmol/l and at 2 and 4 mmol/l for serum lactate (LAC). Analysis was performed on admission and pre-operative serum LAC and BICARB levels. Results: 55 patients met the criteria for review, 11 patients did not have surgery and were excluded, leaving 44 subjects for analysis. Patient characteristics were: female 55%, age 71 ± 14 years, ICU LOS 7 ± 6 days, 91% required mechanical ventilation (3.7 ± 6 days), BMI 27 ± 7, median APACHE II 25 and median SOFA was 6 on day of surgery. 79% of patients had at least one LAC, 59% had ≥two and 82% had at least one BICARB measured. Only 57% of patients had pre-op acidosis. 68% of patients had small bowel involvement, 48% had large bowel and 23% had both. Age as a continuous variable was a significant (P=0.02, OR 0.8) risk factor for surgical resection. Younger patients had surgical resection more frequently than older patients (89% vs 13%, P<0.01). Overall mortality was 34%; there were no differences in gender, age, BMI, or severity of illness between the survivors and non-survivors. Lactate and BICARB had low a PPV (< 43%) for surgical resection and mortality. Conclusions: Mesenteric ischemia has a high mortality and is more common in patients over age 60 years. Measurement of LAC was frequent in patients with MI; however, pre-operative acidosis was not predictive of mortality or need for surgical resection. The utility of serial measurements of LAC and BICARB pre-operatively in patients with MI should be re-evaluated.