Incidence of post-thyroidectomy hypocalcaemia in Kenyatta National Hospital

Abstract

Background: Thyroidectomy is a major and frequent operation in Kenyatta National Hospital with hypocalcaemia as a common and serious complication resulting in significant morbidity. Objective: To determine the incidence of post-thyroidectomy hypocalcaemia in Kenyatta National Hospital. Study design: Prospective descriptive cohort study. Setting: Surgical Outpatient Clinic, Surgical wards, Theatre and Renal Unit - Biochemistry laboratory. Patients and methods: Twenty-five (25) patients aged 17 to 74 years scheduled to undergo elective thyroidectomy were enrolled into the study from April to October, 2014. Blood for serum calcium and albumin levels was collected pre-operatively; within 48 hours and 2 weeks post-operatively, and submitted to the Renal Unit biochemistry laboratory. Data was collected using a structured questionnaire. Main outcome measure: Thecalculated ionized calcium levels pre-operatively and post-operatively within 48 hours and at 2 weeks. Data analysis:Data was entered into a secured access database. Differences in the patients who developed post-thyroidectomy hypocalcaemia were calculated using the χ2 test for categorical variables and the Mann–Whitney U test for continuous variables using SPSS version 18. Regression was used to determine the Odds Ratio of developing hypocalcaemia. Data was presented in tables, graphs and charts. Results:The overall incidence of post-thyroidectomy hypocalcaemia using calculated ionized calcium levels was 68%. In patients with pre-operative hypocalcaemia, 80% developed post-operative hypocalcaemia versus 60% in patients with pre-operativenormocalcaemia.Patients who underwent bilateral surgery had a higher incidence (80%) of post-operative hypocalcaemia versus 50% for those who had unilateral surgery. All the patients who underwent unilateral surgery developed mild hypocalcaemia while those who underwent bilateral surgery developed mild and severe hypocalcaemia at 75% and 25% respectively. The patients had a median age of 39 years. An increase in age did not increase risk of developing hypocalcaemia. Male patients were 84% less likely (odds ratio/OR 0.156) to get post-thyroidectomy hypocalcaemia but the P value of 0.09 was not significant. All the patients in the study were asymptomatic. Conclusion:Post-operative hypocalcaemia is common in patients undergoing thyroid surgery in our set-up. Patients who underwent bilateral surgery and those with pre-operative hypocalcaemia had a higher incidence of post-operative hypocalcaemia.An increase in age did not increase risk while female patients were more likely to develop post-thyroidectomy hypocalcaemia