Sodium and water imbalances following sellar and suprasellar surgeries in Sri Lanka; a descriptive cross-sectional study
Authors: Wijewickrama Piyumi , Ambawatte Sathyajith , Sumanatilleke Manilka , Garusinghe Chaminda , Kamaladasa Kasun , Athukorala Tharaka , Somasundaram Noel 
Published: October 2022

Background
Water and sodium imbalances are common following sellar/suprasellar surgeries. The aim of the current study was to analyse the incidence, associations and management of sodium and water imbalances following sellar/ suprasellar surgeries in Sri Lanka.
Methods
A prospective cross-sectional study carried out in the National Hospital of Sri Lanka over 18 months from September 2019. All patients undergoing sellar/suprasellar surgeries fulfilling the inclusion criteria were followed up to 7 days after surgery, to collect clinical, biochemical and intake-output parameters.
Results
Out of 139 patients, 108 were trans-sphenoidal surgeries (TSS), 31 had craniotomies. Majority had non-functioning pituitary adenomas (NFPA) (n=81,58.2%) followed by craniopharyngioma (n=22,15.8%), acromegaly (n=20,14.3%), Cushing’s-disease (n=9,6.4%), suprasellar meningioma (n=6,4.3%) and prolactinoma (n=1,0.7%). Post-operative hyponatremia occurred in 18.5% TSS and 38.7% craniotomy patients, with syndrome-of-inappropriate-ADH-secretion (SIADH) being the commonest cause.
First surgery (p:0.004, Adjusted-OR:1.38(1.23-1.53)), craniotomy compared to TSS (p:0.001, Adjusted-OR:2.61(1.86-4.66)), tumour size>3cm (p:<0.001, Adjusted-OR:2.81(2.21-4.05), pre-operative dexamethasone (p:<0.001, Adjusted-OR:3.60(1.84-7.36)) and, craniopharyngioma (p:0.001, Adjusted-OR:3.69(1.71-6.9)) were identified as risk factors for post-operative SIADH. No patients with Cushing’s disease or acromegaly developed SIADH. Mainstay of management of SIADH was fluid restriction.
Post-operative polyuria was detected in 75 (53.9%) with 50 having cranial diabetes insipidus (CDI) and the rest having transient-polyuria due to other causes. Re-operation (p:<0.001, Adjusted-OR:3.02(1.81-5.89)), suprasellar location of the tumour (p:<0.001, Adjusted-OR:7.89(2.99-20.62)), craniotomy (p:0.004, Adjusted-OR 2.41:(1.36-4.55)), tumour size>2cm (p:0.018, Adjusted-OR:1.29(1.01-1,62)), craniopharyngioma (p:<0.001, Adjusted-OR:2.93(2.11-4.21)), and post-operative dexamethasone (p:0.008, Adjusted-OR:1.7(1.23-2.66)) were identified as risk factors for post-operative CDI. For patients who had transient polyuria, but not CDI, acromegaly was the only identified association (p:<0.001, Adjusted-OR 7.81 (4.12-13.99)). Only 4 patients went on to have permanent CDI. Mainstay of management of CDI was desmopressin as needed, along with fluid management.
Conclusion
Diagnosis and management of water and sodium imbalances following sellar/suprasellar surgeries is challenging, needing specialist endocrinology input. Post-operative hyponatremia, SIADH, transient polyuria and transient CDI are common. This is the first study carried out in Sri Lanka to analyse the patterns of sodium and water disorders following sellar/ suprasellar surgeries. These findings highlight that certain pre-operative characteristics could predict post-operative water and sodium imbalances and will be useful in early identification of high-risk patients.