Determinants of Severe Hypocalcemia After Parathyroidectomy in Patients with End-Stage Kidney Disease and Renal Hyperparathyroidism: A Retrospective Cohort Study

<b>Background</b>: Parathyroidectomy (PTX) is generally curative in renal hyperparathyroidism (RHPT) that is refractory to medical treatment in end-stage kidney disease (ESKD) patients. Severe hypocalcemia is a common complication of PTX and results in increased monitoring, interventions, lengths of stay, and costs of care. This study aimed to find the determinants and cutoff values of the biochemical determinants, if any, for severe post-operative hypocalcemia after PTX in adult patients with ESKD. <b>Methods</b>: Severe post-operative hypocalcemia was defined as a lowest adjusted serum calcium level < 2 mmol/L during a hospitalization stay following PTX. Receiver operating curves (ROCs) with area under the curve (AUC) values for pre-operative intact parathyroid hormone (iPTH) and pre-operative alkaline phosphatase (ALP) levels against hypocalcemia were used to determine cutoffs. Generalized linear models using Poisson regression with robust error variance were used to estimate the relative risk of severe post-operative hypocalcemia. <b>Results</b>: In total, 75 patients (38 women, 50.7%) with a mean age of 53.8 ± 11.4 years were enrolled; 43 (57%) patients developed severe hypocalcemia post-PTX and had higher pre-operative serum iPTH and ALP levels, as well as a significantly longer hospitalization post-operation (10.5 vs. 4.3 days, <i>p</i> =< 0.001). A pre-operative iPTH level of >166 pmol/L had an AUC-ROC of 0.73 and 72% sensitivity and 73% specificity, respectively, in predicting severe post-operative hypocalcemia with a relative risk of 2.00 [95% CI 1.27-3.33, <i>p</i> = 0.003]. <b>Conclusions</b>: A pre-operative iPTH level > 166 pmol/L is a strong risk predictor for post-operative severe hypocalcemia. Pre-emptive interventions in this high-risk group could potentially result in a reduced length of stay and lower acuity of care.