Intravenous maintenance fluid tonicity and hyponatremia after major surgery- a cohort study

Abstract Background Intravenous maintenance fluid (IMF) tonicity and composition influence plasma electrolyte balance. Objective To determine if hypotonic IMF therapy contributes to post-surgical hyponatremia. Setting Single-center tertiary institution. Participants Adults who underwent major surgery and received peri-surgical IMF, with exclusive administration of hypotonic pre-mixed 0.33% saline, 5% dextrose and potassium chloride (DK0.33%S), or isotonic 0.9% saline with or without 5% dextrose (NS/DNS). Outcomes and measures We examined post-surgical hyponatremia, hypokalemia and acute kidney injury (AKI), associated with use of either IMF. Results We studied 659 patients, of whom 161 patients (24%) developed post-surgical hyponatremia. DK0.33%S (versus NS/DNS) IMF was administered in 52% of patients who developed hyponatremia, compared to 38% of patients with stable natremia (p = 0.001). More patients with hyponatremia underwent gastrointestinal-hepatobiliary or abdominal (GI/HBS/Abd) surgery versus other surgical-sites (p = 0.001). Hypokalemia developed in 1% versus 10% of patients who received DK0.33%S and NS/DNS IMF respectively (p Conclusions Administration of DK0.33%S IMF, compared with NS/DNS, is associated with post-surgical hyponatremia in adults after major surgery, but with less hypokalemia. The higher rate of AKI observed with NS/DNS IMF requires further evaluation.