Background:
Hyponatraemia is the most common reason for readmission after transsphenoidal pituitary surgery (TSS). Risk factors for delayed post-operative hyponatraemia (DPH) remain unclear. We hypothesised that routine measurement of Day 7 post-operative sodium (D7Na) would facilitate outpatient fluid restriction (FR) for DPH and reduce the readmission rate.
Aims:
To evaluate the impact of D7Na measurement on the incidence and severity of DPH in patients who had TSS at St Vincent’s and St Vincent’s Private Hospitals, Sydney. We also aimed to identify pre-operative and early post-operative risk factors for DPH.
Methods:
Retrospective audit of all TSS between March 2016 and August 2017 (n=71). Measurement of D7Na commenced in March 2017 (n=36).
Results:
Median age was 48 (20-67) years; 51% were female. Fifty-eight (82%) had a pituitary adenoma. DPH occurred in 12 cases (17%): 6 severe, 3 moderate and 3 mild. Eight patients (11%) required readmission. There was no difference in age, gender, body mass index, previous TSS, pre-operative sodium, lesion size, presence of cavernous sinus invasion, surgical pathology or incidence of preceding DI between the 8 patients who required readmission and the 63 who did not. Day 4 post-operative sodium (D4Na) was lower in those who required readmission (140 [139-140] vs 142 [140-143] mmol/L; p=0.008). Results were similar when patients with any severity DPH were compared with those who maintained normal sodium. D4Na ≤140 mmol/L was 88% sensitive and 71% specific for readmission with DPH.
Measurement of D7Na increased detection of DPH (22% vs 11%) but FR at that stage did not impact readmission rate. Readmitted patients already had significant symptoms by D7 or had worsening DPH despite FR.
Conclusion:
Routine measurement of D7Na results in increased detection of milder DPH but does not reduce readmission. FR when D4Na ≤140 mmol/L may reduce readmission for DPH and warrants further investigation.