Calcium supplement necessary to correct hypocalcemia after total parathyroidectomy for renal osteodystrophy

[Evolution of the incidence and results at 12 months of parathyroidectomy: 40 years of experience in a dialysis center with two successive surgical departments]

INTRODUCTION

Secondary hyperparathyroidism remains the main complication of mineral and bone metabolism in patients with chronic kidney disease. In case of resistance to medical treatment (native and active vitamin D, calcium and calcimimetics), surgical parathyroidectomy is indicated. The aim of this retrospective study is to show the evolution of the incidence and results of surgical parathyroidectomy in our center between 1980 and 2020 as patient characteristics, diagnostic and therapeutic strategies have changed.

PATIENTS AND METHODS

We collected data from dialysis patients who had a first surgical parathyroidectomy between 2000 and 2020 (period 2) in the same surgical department and compared them with historical data between 1980 and 1999 (period 1) operated in one other center.

RESULTS

In period 1, 53 surgical parathyroidectomy were performed (2.78/year, 0 to 5, 8.5/1000 patients-year) vs.56 surgical parathyroidectomy in period 2 (2.8/year, 0 to 9, 8/1000 patients-year). The patients of the 2 periods were comparable except for the higher dialysis vintage in period 1 (149±170 vs.89±94 months; P=0.02). In comparison with dialysis patients not requiring surgical parathyroidectomy during the same period, patients who had surgical parathyroidectomy were younger, had higher dialysis vintage and lower diabetes prevalence, but more frequently carriers of glomerulopathy or polycystosis. Systematically performed in period 2, cervical ultrasound identified at least one visible gland in 78.6% of cases while the scintigraphy, performed only in 66% of cases, found at least one gland in 81% of cases. Twelve months after surgery, PTH > 300 pg/mL (marker of secondary hyperparathyroidism recurrence or surgery failure) was present in 30% of patients in period 1 vs. 5.3% in period 2. Hypoparathyroidism was also more frequently observed in period 2 (35.7 vs. 18.8%). Surgical complications were also higher in period 1.

CONCLUSION

Despite therapeutic and strategic advances, severe secondary hyperparathyroidism is still as common as ever. It is favored by excessively high PTH targets, by suboptimal prevention before dialysis and poor tolerance of calcimimetics. The surgical parathyroidectomy is effective and safe in the hands of a specialized team with an ultrasound and scintigraphic preoperative assessment.

Hungry bone syndrome after parathyroidectomy in end-stage renal disease patients: review of an alkaline phosphatase-based treatment protocol

AIM

Hyperparathyroidism in chronic kidney disease-mineral and bone disorder is associated with significant morbidity and mortality. Parathyroidectomy is widely carried out as treatment despite complications such as hypocalcaemia post-surgery. Our centre has been using an ALP-based protocol to replace calcium postoperatively to prevent hypocalcaemia. We aim to describe and audit our calcium replacement protocol post-parathyroidectomy METHODS: We, retrospectively, analyse 167 end-stage kidney disease patients who had parathyroidectomy with auto-implantation in Singapore General Hospital between January 2008 and December 2013. Their calcium replacement postoperatively was initiated upon patient arrival back in ward on the same day of surgery based on their pre-op ALP prior to occurrence of hypocalcaemia. Patient demographics, surgical and laboratory parameters were reviewed from medical records. Changes in calcium postoperatively were reported to look for incidence of calcium derangement.

RESULTS

Mean calcium levels between pre-operation day and post-operation day 7 ranged from 2.31 to 2.70 mmol/L. Decline in serum calcium was common in all patients prior to starting calcium replacement. Eighteen patients (10.9%) experienced hypocalcaemia immediately post-operation prior to commencement of IV calcium replacement. Patients with immediate post-operation hypocalcaemia had lower pre-operation calcium but higher pre-operation alkaline phosphatase (ALP) and pre-operation intact parathyroid hormone. Hypercalcaemia is common likely from aggressive IV calcium replacement using the protocol. The average length of stay for patients prior to calcium stabilization and discharge was 9 days.

CONCLUSION

Implementation of an ALP-based prophylactic calcium replacement protocol with daily serum calcium monitoring can ameliorate severe hypocalcaemia post-parathyroidectomy.

Risk Factors for Elevated Preoperative Alkaline Phosphatase in Patients with Refractory Secondary Hyperparathyroidism

Elevated preoperative levels of alkaline phosphatase (ALP) in patients with refractory secondary hyperparathyroidism are correlated with postoperative hypocalcemia and mortality. The aim of this study was to identify the predictors of preoperative ALP in patients with secondary hyperparathyroidism. From April 2012 to December 2015, 220 patients with refractory secondary hyperparathyroidism undergoing total parathyroidectomy without autotransplantation were reviewed. A total of 164 patients presented with elevated preoperative ALP. Univariate analysis showed that patients with elevated ALP were significantly younger. The elevated ALP group had significantly higher levels of preoperative parathyroid hormone (PTH), lower preoperative serum calcium, higher preoperative phosphorus, lower postoperative hypocalcemia, and a longer hospital stay. Logistic regression analysis showed that elevated preoperative PTH was a significant independent risk factor for elevated preoperative ALP (P = 0.000), and its value of 1624 pg/mL was the optimal cutoff point. Factors predictive of elevated preoperative ALP in patients with secondary hyperparathyroidism include preoperative PTH. Earlier surgery, aggressive calcium supplementation, and more careful or aggressive postoperative care for high-risk patients are needed.

Serum parathyroid hormone and alkaline phosphatase as predictors of calcium requirements after total parathyroidectomy for hypocalcemia in secondary hyperparathyroidism

BACKGROUND

To prevent hypocalcemia, this study examined the efficiency of a calcium supplement formula guided by predicted calcium requirement in patients with renal failure after parathyroidectomy with autotransplantation.

METHODS

In the first phase, a protocol was followed whereby intravenous calcium gluconate was repeatedly titrated based on serum calcium levels in 22 patients with parathyroidectomy with autotransplantation. In the second phase, the first equation protocol was applied in 74 patients with parathyroidectomy with autotransplantation and revised.

RESULTS

There is a significant correlation between the postoperative amount of calcium requirement and preoperative serum alkaline phosphatase level (r = 0.442; P < .001) and parathyroid hormone level (PTH; r = 0.889; P < .001). For prediction of insufficient calcium supplement, the cutoff point of PTH and alkaline phosphatase level values were calculated by receiver operating characteristic (ROC) curve analysis and modified equations were developed by regression analysis.

CONCLUSION

The preoperative PTH and alkaline phosphatase levels can predict postoperative calcium requirements, such that equations of calcium supplement allow the management of hypocalcemia efficiently in patients on dialysis after parathyroidectomy with autotransplantation.

Postoperative hungry bone syndrome in patients with secondary hyperparathyroidism of renal origin

BACKGROUND

Hungry bone syndrome (HBS) is a postoperative condition of severe hypocalcemia that can be seen in patients who have undergone parathyroidectomy (PTX) for secondary hyperparathyroidism (2HPT) of renal origin. This study examines HBS in patients after PTX for 2HPT.

METHODS

Prospectively collected data was retrospectively reviewed in patients who underwent PTX for 2HPT of renal origin at a single institution. HBS was defined as the need for additional days of hospitalization or readmission for intravenous calcium supplementation due to clinical symptoms of hypocalcemia, including tingling, muscle spasms, and bone pain and/or immediate postoperative low serum calcium ≤7.5 mg/dl.

RESULTS

Of 79 patients who underwent PTX for 2HPT, 27.8% (n = 22) experienced HBS. Young age (≤45 years, p = 0.02) was the only preoperative variable that predicted HBS. Most patients developed HBS within 18 h after surgery and required a prolonged hospital stay (19/22) compared to those requiring hospital readmission within the first 7 days (3/22). Initial postoperative serum calcium levels within 18 h of surgery were significantly lower in those patients who developed HBS (7.1 vs. 8.3 mg/dl, p = 0.001), and those patients also had a greater absolute decrease in serum calcium (2.8 vs. 3.5 mg/dl, p = 0.04).

CONCLUSION

HBS develops in a significant proportion of patients generally within the first 18 h after subtotal PTX for 2HPT. The only identifiable preoperative risk factor for HBS was young age. Additionally, low initial calcium levels and greater absolute decrease in serum calcium may help identify those patients that will develop HBS requiring judicious calcium supplementation.

Alkaline phosphatase predicts calcium requirements after total parathyroidectomy in patients receiving dialysis

BACKGROUND

: It can be difficult to achieve a stable serum calcium level after parathyroidectomy for renal hyperparathyroidism. This study examined the impact of a calcium replacement protocol guided by predicted need in reducing hospital stay.

METHODS

: This two-phase observational study included patients receiving dialysis who underwent parathyroidectomy. In the initial phase, a standard protocol was followed whereby oral calcium was gradually titrated upwards based on serum calcium levels. The protocol was revised in the second phase such that patients were 'loaded' with the predicted elemental calcium requirement immediately after surgery.

RESULTS

: Forty-four patients were treated according to the standard protocol and 34 using the new protocol. There was a strong correlation between postoperative elemental calcium requirement and admission serum alkaline phosphatase level (ALP) (r(s) = 0.711, P < 0.001). Postoperative hospital stay was reduced from a median (range) of 5 (3-12) to 3 (2-7) days after introduction of the revised protocol as a result of better calcium balance (P < 0.001). Multivariable analysis confirmed that use of the revised protocol was the main predictor of length of stay.

CONCLUSION

: ALP can predict postoperative calcium requirements and streamline hospital stay by guiding replacement therapy.