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Kidney Week

Abstract: TH-PO151

Predictors of Post-Parathyroidectomy Hypocalcemia in ESRD Patients with Resistant Renal Hyperparathyroidism

Session Information

Category: Bone and Mineral Metabolism

  • 502 Bone and Mineral Metabolism: Clinical

Authors

  • Chen, Fangxia, Tan Tock Seng Hospital, Singapore, Singapore
  • Looi, Wan Limm, Tan Tock Seng Hospital, Singapore, Singapore
  • Tan, Zi Kheng, Tan Tock Seng Hospital, Singapore, Singapore
  • Yeo, See Cheng, Tan Tock Seng Hospital, Singapore, Singapore
  • Bairy, Manohar, Tan Tock Seng Hospital, Singapore, Singapore
Background

Post-operative hypocalcemia following parathyroidectomy (PTX) for resistant renal hyperparathyroidism(rRHPT) is a major complication that is preventable yet highly prevalent despite protocolized perioperative management . We aimed to determine the predictors of post operative hypocalcemia in our centre from patient characteristics and routine biochemical parameters in order to aid our review of the current centre protocol.

Methods

75 ESKD patients who underwent parathyroidectomy for rRHPT between May 2016 and October 2022 were enrolled in the study. We collected patients’ demographic data, serum levels of albumin, calcium, phosphate, intact parathyroid hormone (iPTH), alkaline phosphatase (ALP), doses of phosphate binders (calcium based and non-calcium based), vitamin D and cinacalcet before and for up to seven days after parathyroidectomy.ROC curves with AUC for iPTH and ALP levels against hypocalcemia were used to determine cutoffs. Multivariable logistic regression model was used to determine the odds ratio and as the incidence rate of the outcome was high, generalized linear models using Poisson regression with robust error variance were used to estimate relative risk.

Results

37 men and 38 women with mean age of 53.8 ± 11.4 years at the time of surgery were enrolled. The median serum iPTH and ALP levels were 169.8 pmol/L (IQR 113.7, 266.7) and 272U/L (IQR 169, 463) respectively. The mean dialysis vintage was 73.4 months. 43(57%) patients developed severe hypocalcaemia (< 2mmol/L). Patients with severe hypocalcaemia had higher median pre-operative serum iPTH and ALP levels (216pmol/L vs.129.75pmol/L, 380U/L vs. 220.5U/L respectively) and significantly longer mean post operative hospitalization (10.5 vs 4.3 days). Preoperative iPTH level was the only significant predictor of hypocalcemia. iPTH level of >166 pmol/L had 72% sensitivity and 73% specificity for predicting post-operative hypocalcaemia with a relative risk of 2.00 [95% CI 1.27-3.33], p=0.003.

Conclusion

Pre-operative iPTH levels >166 pmol/L can predict post PTX hypocalcemia in ESRD patients. A clinical protocol utilising this iPTH level for risk stratification to determine frequency of calcium level monitoring and calcium and vitamin D supplementation in the peri operative period may help reduce the risk of hypocalcemia.