Early postoperative plasma calcium concentration as a predictor of the need for calcium supplement after parathyroidectomy

A Practical Mathematic Method to Predict and Manage Hypocalcemia After Parathyroidectomy and Thyroidectomy

OBJECTIVE

Prediction and early intervention for hypocalcemia following parathyroidectomy and total thyroidectomy can decrease hospital cost and prevent severe hypocalcemia-related complications. This study aims to predict the severity of hypocalcemia after parathyroidectomy or thyroidectomy and to stratify patients into groups with different levels of risk for developing severe hypocalcemia, so that higher risk patients may be monitored more closely and receive earlier interventions.

METHODS

This was a retrospective cohort study of 100 patients with primary hyperparathyroidism who underwent parathyroidectomy as the primary treatment modality at a tertiary care hospital. Clinical information, including demographic information, perioperative PTH and calcium levels, vitamin D levels, weight of the pathologic glands removed, gland pathology, and re-admission rates, were retrieved. Statistical analysis was performed to analyze the association between collected variables and percentage of calcium drop following parathyroidectomy with statistical significant set at P-values <0.05.

RESULTS

Age, sex, and vitamin D level provided very minimal information to quantify risks of postoperative hypocalcemia. The percentage of decrease from preoperative PTH level to the lowest PTH level after the removal of the abnormal gland(s) is the most significant predicting factor for the severity of postoperative hypocalcemia. There is a mathematic regressional correlation between them. A formula was generated to quantify this linear relationship between them, and the nadir calcium can be calculated as Canadir=Capreop*[1-0.35*(PTHpreop-PTHintraop)2PTHpreop2], where Ca_nadir = the lowest postoperative calcium level, and PTH_intraop = PTH level 15 minutes after removal of the abnormal gland, with the value of R² > 0.7. The formula has been tested primarily in our patient population with good reliability.

CONCLUSIONS

The highest preoperative, lowest postoperative, and change in PTH level can help us reliably calculate the trend of postoperative calcium level. Decision to pursue early interventions can be made based on the calculated result from the formula we obtained.

Primary hyperparathyroidism: Dynamic postoperative metabolic changes

OBJECTIVE

Little is known about the natural changes in parathyroid function after successful parathyroid surgery for primary hyperparathyroidism. The association of intact parathyroid hormone (iPTH) and calcium (Ca) with "temporary hypoparathyroidism" and "hungry bone syndrome" (HBS) was evaluated.

DESIGN

Potential risk factors for temporary hypoparathyroidism and HBS were evaluated by taking blood samples before surgery, intra-operatively, at postoperative day (POD) 1, at POD 5 to 7, in postoperative week (POW) 8 and in postoperative month (POM) 6.

PATIENTS

Of 425 patients, 43 (10.1%) had temporary hypoparathyroidism and 36 (8.5%) had HBS.

MEASUREMENTS

The discriminative ability of iPTH and Ca on POD 1 for temporary hypoparathyroidism and HBS.

RESULTS

Intact parathyroid hormone (IPTH) on POD 1 showed the highest discriminative ability for temporary hypoparathyroidism (C-index = 0.952), but not for HBS. IPTH was helpful in diagnosing HBS between POD 5 and 7 (C-index = 0.708). Extending the model by including Ca resulted in little improvement of the discriminative ability for temporary hypoparathyroidism (C-index = 0.964) and a decreased discriminative ability for HBS (C-index = 0.705). Normal parathyroid metabolism was documented in 139 (32.7%) patients on POD 1 and in 423 (99.5%) 6 months postoperatively, while 2 (0.5%) patients had persistent hyperparathyroidism, one diagnosed between POD 5 and 7 and another at POW 8. No patients suffered from permanent hypoparathyroidism.

CONCLUSIONS

The necessity for Ca and vitamin D3 substitution cannot be predicted with certainty before POD 5 to 7 without serial laboratory measurements. Based on the results, a routine 8-week course of Ca and vitamin D3 treatment seems reasonable and its necessity should be evaluated in a follow-up study.

Delayed Calcium Normalization After Presumed Curative Parathyroidectomy is Not Associated with the Development of Persistent or Recurrent Primary Hyperparathyroidism

BACKGROUND

Following parathyroidectomy for primary hyperparathyroidism (pHPT), serum calcium levels typically normalize relatively quickly. The purpose of this study was to identify potential factors associated with delayed normalization of calcium levels despite meeting intraoperative parathyroid hormone (IOPTH) criteria and to determine whether this phenomenon is associated with higher rates of persistent pHPT.

METHODS

This was a retrospective review of 554 patients who underwent parathyroidectomy for sporadic pHPT from January 2009 to July 2013. Patients who underwent presumed curative parathyroidectomy and had elevated POD0 calcium levels (>10.2 mg/dL) were matched 1:2 for age and gender to control patients with normal POD0 calcium levels.

RESULTS

Of the 554 patients, 52 (9 %) had an elevated POD0 Ca (median 10.7, range 10.3-12.2). Compared with the control group, these patients had higher preoperative calcium (12 vs. 11.1, p < 0.001) and PTH (144 vs. 110 pg/mL, p = 0.004) levels and lower 25OH vitamin D levels (26 vs. 31 pg/mL; p = 0.024). Calcium normalization occurred in 64, 90, and 96 % of patients by postoperative days (POD) 1, 14, and 30, respectively. There was no difference in rates of single-gland disease or cure rates between the groups.

CONCLUSIONS

After presumed curative parathyroidectomy, nearly 10 % of patients had transiently persistent hypercalcemia. Most of these patients had normal serum calcium levels within the first 2 weeks and did not have increased rates of persistent pHPT. Immediate postoperative calcium levels do not predict the presence of persistent pHPT, and these patients may not require more stringent follow-up.

Hungry bone syndrome: still a challenge in the post-operative management of primary hyperparathyroidism: a systematic review of the literature

Hungry bone syndrome (HBS) refers to the rapid, profound, and prolonged hypocalcaemia associated with hypophosphataemia and hypomagnesaemia, and is exacerbated by suppressed parathyroid hormone (PTH) levels, which follows parathyroidectomy in patients with severe primary hyperparathyroidism (PHPT) and preoperative high bone turnover. It is a relatively uncommon, but serious adverse effect of parathyroidectomy. We conducted a literature search of all available studies reporting a 'hungry bone syndrome' in patients who had a parathyroidectomy for PHPT, to identify patients at risk and address the pitfalls in their management. The severe hypocalcaemia is believed to be due to increased influx of calcium into bone, due to the sudden removal of the effect of high circulating levels of PTH on osteoclastic resorption, leading to a decrease in the activation frequency of new remodelling sites and to a decrease in remodelling space, although there is no good documentation for this. Various risk factors have been suggested for the development of HBS, including older age, weight/volume of the resected parathyroid glands, radiological evidence of bone disease and vitamin D deficiency. The syndrome is reported in 25-90% of patients with radiological evidence of hyperparathyroid bone disease vs only 0-6% of patients without skeletal involvement. There is insufficient data-based evidence on the best means to treat, minimise or prevent this severe complication of parathyroidectomy. Treatment is aimed at replenishing the severe calcium deficit by using high doses of calcium supplemented by high doses of active metabolites of vitamin D. Adequate correction of magnesium deficiency and normalisation of bone turnover are required for resolution of the hypocalcaemia which may last for a number of months after successful surgery. Preoperative treatment with bisphosphonates has been suggested to reduce post-operative hypocalcaemia, but there are to date no prospective studies addressing this issue.

Applicability of intraoperative parathyroid hormone assay during thyroidectomy

OBJECTIVE

To evaluate the applicability of intraoperative parathyroid hormone (quick PTH) assay to monitor parathyroid function and to identify clinically significant hypocalcemia compared with postoperative serum calcium monitoring.

SUMMARY BACKGROUND DATA

Close monitoring of serum calcium levels is a standard of care to identify post-thyroidectomy hypocalcemia due to parathyroid insufficiency.

METHODS

Quick PTH assay was performed before and after thyroidectomy for 100 patients at risk of postoperative hypocalcemia and 20 control patients who underwent unilateral lobectomy. Postoperative serum calcium levels were closely monitored.

RESULTS

Control patients had a normal but 38.9 +/- 5.9% (mean +/- SEM) decline in quick PTH after thyroidectomy. Eleven of 100 at-risk patients (11%) developed postoperative hypocalcemia. Hypocalcemic patients had significantly lower quick PTH values after thyroidectomy compared with that of normocalcemic patients. Serum calcium was significantly lower in hypocalcemic patients the morning after operation but not early after the operation (within 6 hours). A normal or less than 75% decline in quick PTH after thyroidectomy can accurately identify normocalcemic patients during surgery as compared to more than 24 hours by serum calcium monitoring.

CONCLUSIONS

The quick PTH assay can monitor parathyroid function during thyroidectomy and identify patients at risk of clinically significant hypocalcemia much earlier than serum calcium monitoring. It may facilitate early discharge and the use of parathyroid autotransplantation during thyroidectomy.

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

BACKGROUND

Prediction of the extent of calcium supplement will facilitate safe and efficient management of hypocalcemia in the early postoperative stage of total parathyroidectomy with autotransplantation (PTXa) in patients with renal osteodystrophy.

METHODS

The correlation between the extent of calcium deficiency, estimated by the amount of calcium supplement over 48 h after PTXa and using various parameters such as carboxy terminal parathyroid hormone (c-PTH), intact PTH (i-PTH), alkaline phosphatase (ALP), serum calcium, serum phosphorus, duration of hemodialysis, total weight of resected parathyroid glands and degree of subperiosteal resorption of the middle phalanx was examined in 49 patients who underwent PTX with subcutaneous autotransplantation. Bone mineral density (BMD) was also determined before, 3 months and 1 year after PTXa with dual energy X-ray absorptiometry (DEXA) in 13 patients.

RESULTS

There was a positive correlation between pre-operative i-PTH level (r=0.56, P<0.0005) or ALP level (r=0.50, P<0.0005) and the amount of calcium supplement over 48 h after PTXa in these patients. Furthermore, the degree of subperiosteal resorption, determined by Jensen's classification, was significantly correlated with the amount of calcium supplement after PTX (P<0.05). Bone mineral density 3 months after (P<0.0005) and 1 year after PTXa (P<0.001) significantly increased compared with BMD before PTXa in all patients examined.

CONCLUSION

These findings suggest that the pre-operative determination of i-PTH, ALP levels and degree of subperiosteal resorption allow the management of hypocalcemia safely and efficiently in renal osteodystrophy patients after PTXa.