Metabolic Acidosis in the Surgical Intensive Care Unit: Risk Factors, Clinical Correlates and Outcome. Findings from a High Dependency Heart and Vascular Surgical Center in Nigeria

Background: Metabolic acidosis (MA) is a common finding on the surgical ward, more so in the intensive care unit. Diseases affecting the major organ systems of the body and higher grades of surgery are common risk factors for MA. It is associated with poor treatment outcome. Aim: To determine the risk factors and clinical correlates of metabolic acidosis and assess its relationship with treatment outcome. Methodology: A retrospective study at the “Tristate Heart and vascular Center” in Ilishan-Remo South west Nigeria, on patients that had cardiac and vascular surgeries from January 2015 to December 2019. Three hundred and forty two participants took part in the study. The demographic, clinical and laboratory findings were entered. Statistical analysis was with Student’s t-test and Chi square. Results: Two hundred and six males and 136 females were studied. The incidences of metabolic acidosis prior to induction, on post-operative day one (POD1) and on POD28 were 20.7%, 39.8% and 14.1% respectively. Nine (2.6%) participants died during admission, of this, 6 (66.7%) had MA at presentation but all (100%) had MA on POD1. The Risk factors for MA were advanced age, comorbidities, open heart surgery, elevated systolic blood pressure and low eGFR. Metabolic acidosis was a risk factor for prolonged hospital stay, perioperative death and declining kidney function which was commoner among participants with preexisting kidney dysfunction. Conclusion: The incidence of metabolic acidosis was 20.7% at induction of anesthesia, rose to 39.8% on POD1 and by POD28, it has significantly reduced to 14.1%. While advancing age and comorbidities were risk factors for MA, the occurrence of MA increased the risk of declining kidney function, prolonged hospital stay and death.