Audit of changes in serum urea and electrolytes following peri-operative intravenous fluid therapy

One thousand and eleven patients discharged from the postoperative recovery ward with intravenous infusions were reviewed in order to audit the extent of assessment of serum urea and electrolytes (U&Es) and the change in serum U&Es over the perioperative period. 69.7% had preoperative U&Es estimation, 42.5% had both a pre- and postoperative estimation and in 5%, only a postoperative estimate was undertaken. 12.2% of patients whose U&Es were measured had an abnormal preoperative serum potassium compared to 17.2% postoperatively (NS). Compared to a preoperative incidence of 13%, more patients (27.3%) had an abnormal postoperative serum sodium (p < 0.0001). There was a tendency towards postoperative hyponatraemia: 10.0% in the preoperative period compared to a postoperative 25.3% (p < 0.0001). More tests were performed in the elderly (83.9% in age > 65 years versus 69% in age 17-64-p < 0.0001) who were more likely to have electrolyte disturbances preoperative hypokalaemia (p < 0.05), postoperative hyperkalaemia (p < 0.05), postoperative hyponatraemia (p < 0.03) and raised serum urea, both pre- and postoperatively (p < 0.0001 and p < 0.0005 respectively). Patients undergoing intraabdominal procedures did not have significantly different peri-operative electrolyte abnormalities. Fewer tests were performed in emergency patients, who were hypokalaemic in the postoperative period compared to elective patients (p < 0.01). There was a higher incidence of preoperative hyponatraemia and raised serum urea in the emergency group (p < 0.001 and p < 0.0002 respectively). Neurosurgical emergencies often had a degree of preoperative hypokalaemia which persisted after surgery (p < 0.0001). Results indicate an increased risk of serum electrolyte abnormalities following peri-operative intravenous fluid therapy. However in the majority of patients, the magnitude of the change is not significant clinically.