Variability in post-operative fluid and electrolyte prescription

A four-week retrospective survey of intravenous fluid and electrolyte prescriptions on post-operative surgical patients revealed wide variability in fluid and electrolyte prescription by medical staff. Median volume of intravenous fluid prescribed was 3000 ml (range 1667-5000). Total sodium prescribed varied from 0 to 770, median 242 mmol/day), with potassium infrequently added (range 0-81, median 0 mmol/day). Patients undergoing emergency surgery were prescribed more sodium than those undergoing routine procedures (p = 0.0403); 0.9% saline was the most common fluid prescribed overall. There was poor correlation between serum electrolyte values and the amounts of electrolytes prescribed. Intravenous fluid prescription should take into account the post-operative stress response which reduces sodium requirements (unless there are other concomitant losses) and increases urinary potassium losses. A suitable post-operative 'maintenance' fluid is 4% dextrose/0.18% saline with 1-2 g potassium chloride, particularly if serum electrolyte levels are not known. Other fluid losses should be replaced with equivalent fluids.