Intraoperative Parathyroid Hormone Assay in Patients with Graves’ Disease for Prediction of Postoperative Tetany

Risk factors for postoperative hypocalcemia following total thyroidectomy: a retrospective study

BACKGROUND

and Objectives: Hypocalcemia is a commonly reported complication after thyroid surgery. Many possible risk factors have been identified. The purpose of this study is to analyze various risk factors possibly associated with development of postoperative hypocalcemia after thyroid surgery by dividing the sample population into postoperative hypocalcemia and normal calcium groups.

DESIGN

Retrospective.

SETTING

Multiple centers in the Makkah region of Saudi Arabia.

PATIENTS AND METHODS

Risk factors for postoperative hypocalcemia that were obtained for analysis include patient factors, perioperative blood parameters factors, disease-related factors, and surgical factors. Postoperative hypocalcemia was defined as a reduction of the total calcium level to <8.0 mg/dL. Hypocalcemic and normocalcemic patients were compared by multivariate logistic regression.

MAIN OUTCOME MEASURES

Distinguish independent risk factors for postoperative hypocalcemia after thyroidectomy.

SAMPLE SIZE

215 patients.

RESULTS

The incidence of hypocalcemia was 52.1% (112 of 215 patients). According to multivariate analysis, statistically significant risk factors for predicting postoperative hypocalcemia included postoperative parathyroid hormone level <10 pg/dL, inadvertent parathyroid gland resection, and neck dissection surgeries.

CONCLUSION

The causes of postoperative hypocalcemia are multi-factorial. Because many of these factors are modifiable, they should be identified postoperatively to distinguish high-risk groups and implement early preventive measures.

LIMITATIONS

Retrospective with a relatively small size. We encourage additional prospective studies with a larger sample size in multiple regions of the country, which might reveal further significant results.

Definition and diagnosis of postsurgical hypoparathyroidism after thyroid surgery: meta-analysis

Background

Postsurgical hypoparathyroidism (PH) is the most frequent complication after thyroid surgery. The aim of this systematic review and meta-analysis is to summarize a unifying definition of PH and to elucidate the best possible approach for early detection of PH.

Methods

A systematic review of the literature according to the PICO framework using Embase, PUBMED and the Cochrane library was carried out on 1 December 2021 followed by analysis for risk of bias, data extraction and meta-analysis. All studies addressing the definition of postoperative hypoparathyroidism and/or diagnostic approaches for early detection and diagnosis were included. Case reports, commentaries, non-English articles, book chapters and pilot studies and reviews were excluded.

Results

From 13 704 articles, 188 articles were eligible for inclusion and further analysis. These articles provided heterogeneous definitions of PH. Meta-analysis revealed that postoperative measurements of parathormone (PTH) levels have a higher sensitivity and specificity than intraoperative PTH measurements to predict PH after thyroid surgery. None of the timeframes analysed after surgery within the first postoperative day (POD1) was superior to predict the onset of PH. PTH levels of less than 15 pg/ml and less than 10 pg/ml are both reliable threshold levels to predict the postoperative onset of PH. A relative reduction of mean(s.d.) PTH levels from pre- to postoperative values of 73 (standard deviation 11) per cent may also be predictive for the development of PH. The estimation of calcium levels on POD1 are recommended.

Conclusion

PH is best defined as an undetectable or inappropriately low postoperative PTH level in the context of hypocalcaemia with or without hypocalcaemic symptoms. PTH levels should be measured after surgery within 24 h. Both threshold levels below 10 and 15 pg/ml or relative loss of PTH before/after thyroid surgery are reliable to predict the onset of PH.

Hypocalcemia after Total Thyroidectomy in Graves Disease

CONTEXT

Total thyroidectomy has been shown to provide a cost-effective and efficient method of permanently treating Graves disease; however, hypocalcemia can be a common complication.

OBJECTIVE

To evaluate the risk of hypocalcemia after total thyroidectomy in patients with vs without Graves disease.

DESIGN

The 2016 American College of Surgeons National Surgical Quality Improvement Program participant use data files for procedure-targeted thyroidectomy and from 5871 patients were merged. This study included any patient who underwent total thyroidectomy.

MAIN OUTCOME MEASURES

Whether symptomatic hypocalcemia developed anytime within 30 days after the thyroidectomy. A clinically severe hypocalcemic event was also evaluated as a secondary outcome measure.

RESULTS

Of the 2143 patients who underwent total thyroidectomy, 222 patients experienced hypocalcemia after surgery, 124 of whom had symptomatic hypocalcemia postoperatively. Among patients with hypocalcemia, 16.3% had Graves disease, whereas only 9.4% of patients without Graves disease experienced significant hypocalcemia. Multivariable logistic regression analysis revealed that women (odds ratio = 1.79; 95% confidence interval = 1.16-2.76; p = 0.009) and patients who underwent parathyroid autotransplantation (odds ratio = 1.91; 95% confidence interval = 1.30-2.81; p = 0.001) were at greater risk of development of hypocalcemia. Older patients were less likely to experience hypocalcemia postoperatively (odds ratio = 0.586; 95% confidence interval = 0.44-0.79; p = 0.0001).

CONCLUSION

Patients with Graves disease are about twice as likely to experience hypocalcemia or clinically severe hypocalcemia postoperatively than are patients without the disease.

Role of oral calcium supplementation alone or with vitamin D in preventing post-thyroidectomy hypocalcaemia: A meta-analysis

BACKGROUND

Thyroidectomy is the main intervention for thyroid malignancies and some benign thyroid diseases. Its most common complication is hypocalcaemia, which requires oral or intravenous calcium therapy. The aim of this meta-analysis was to assess the efficacy of routine calcium supplementation with or without vitamin D in preventing hypocalcaemia post-thyroidectomy.

METHODS

Systematic searches of the PubMed, EMBASE, and Cochrane Library databases were performed. The qualities of the included articles were assessed using the Cochrane risk of bias tool. The studies' qualities of outcomes and strengths of evidence were evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) tool. Data analysis was performed using Review Manager 5.3, and odds ratio (ORs) with their 95% confidence intervals (CIs) were computed for dichotomous data.

RESULTS

Ten randomized controlled trials (RCTs) were included. The combined study recruited 1620 patients (343 men and 1277 women) who underwent total thyroidectomy alone or with neck dissection. Calcium supplementation decreased the risk of transient postoperative hypocalcaemia (OR 0.48 [95% CI, 0.31-0.74]; P < .001) but did not decrease the demand for intravenous supplementation or the rate of permanent hypocalcaemia compared to no treatment. Calcium and vitamin D supplementation significantly reduced the rate of transient hypocalcaemia and the demand for intravenous supplementation compared to either no treatment (OR 0.21 [95% CI, 0.11-0.40]; P < .001 and OR 0.26 [95% CI, 0.10-0.69]; P = .007, respectively) or calcium alone (OR 0.39 [95% CI, 0.18-0.84]; P = .02 and OR 0.18 [95% CI, 0.07-0.47]; P < .001, respectively), but did not decrease the rate of permanent hypocalcaemia. GRADE-based confidence was moderate.

CONCLUSION

Postoperative calcium supplementation is effective for preventing post-thyroidectomy hypocalcaemia. Calcium plus vitamin D was more effective than calcium alone in preventing postoperative hypocalcaemia and decreasing the demand for intravenous calcium supplementation. Further, well-designed RCTs with larger sample sizes are required to validate our findings.

Predictors of postoperative hypocalcemia occurring after a total thyroidectomy: results of prospective multicenter study

BACKGROUND

Thyroid surgeries are among the most common operations performed in the world. Hypocalcemia following total thyroidectomy is a common complication that is sometimes difficult to correct. The aim of this study is to determine the risk factors for hypocalcemia following total thyroidectomy and their clinical value.

METHODS

From January 2015 through to April 2017, 400 patients were included in this prospective multicenter study. All patients underwent total thyroidectomy due to various thyroid diseases. The following risk factors were analyzed: pre-operative and post-operative biochemical blood parameters, clinical effects and factors related to surgery, the patient, and the disease.

RESULTS

Post-operative hypocalcemia developed in 257 patients (64.2%). Of them, 197 patients (76.7%) were diagnosed with asymptomatic hypocalcemia. Clinical symptoms were present in 60 of the 257 patients with hypocalcemia (23.3%). The statistically significant predictors of hypocalcemia were decreased calcium and ionized calcium pre-operatively (p < 0.001), parathyroid hormone on day one following surgery (p < 0.001), thyrotoxicosis <10 years before surgery (odds ratio 1.65, 95% CI 1.01-2.70, p = 0.046), the number of parathyroid glands found during surgery (odds ratio 0.52, 95% CI 0.38-0.70, p < 0.001), ligation of the trunk of the left inferior thyroid artery (odds ratio 2.04, 95% CI 1.27-3.29, p = 0.003), ligation of the trunk of the right inferior thyroid artery (odds ratio 2.37, 95% CI 1.47-3.81, p < 0.001), and the number of transplanted parathyroid glands (odds ratio 1.87, 95% CI 1.12-2.97, p = 0.015). In the multivariate analysis, age (odds ratio 1.05, 95% CI 1.01-1.09, p = 0.029) and gender (odds ratio 5.94, 95% CI 1.13-31.26, p = 0.035) were statistically significant predictors.

CONCLUSIONS

This study demonstrates that there is a number of different patient (gender, age, and duration of thyrotoxicosis <10 years before surgery) and surgical (number of parathyroid glands found during surgery, decreased calcium and ionized calcium before surgery, parathyroid hormone on day one following surgery, and ligation of the trunk of the left and right inferior thyroid artery) risk factors predictive of hypocalcemia following total thyroidectomy. Optimization of the surgical technique could possibly prevent the occurrence of hypocalcemia after total thyroidectomy in some cases; in other cases, identification of known risk factors post-operatively could permit early detection and effective treatment of these patients.

Factors predicting hypocalcemia after total thyroidectomy - A retrospective cohort analysis

BACKGROUND

Hypocalcemia after total thyroidectomy is the most frequent complication resulting in prolongation of hospitalisation. Therefore we aimed to analyse clinical risk factors predictive for hypocalcemia and its long term persistence after total thyroidectomy.

METHODS

Retrospective analysis of patients undergoing total thyroidectomy from 2005 until 2013. Outcome measures were initial postoperative hypocalcemia defined as serum calcium below 2.0 mmol/l after total thyroidectomy within 48 h and persistent hypocalcemia defined as serum calcium below 2.0 mmol/l above six months and/or the need for additional calcium and vitamin D supplementation.

RESULTS

Initial postoperative hypocalcemia was present in 160 of 702 patients (22.8%) with 91 patients (13%) developing symptoms. 48 patients (6.8%) had a persistent hypocalcemia above six months. Patients with an initial symptomatic postoperative hypocalcemia showed significantly more often a persistent hypocalcemia compared to asymptomatic patients with biochemical hypocalcemia (38 patients (41.8%) vs. 10 patients (14.5%), p < 0,001). In the binary logistic regression analysis, female gender (OR 2.4; CI95% 1.5-3.8), prolonged surgery time >189 min (OR 1.8; CI95% 1.2-2.6) and parathyroid reimplantation (OR 2.4; CI95% 1.2-4.7) were associated with initial hypocalcemia while only initial symptomatic hypocalcaemia was shown to be independently associated with persistent hypocalcemia (OR 40.9; CI95% 18.5-90.4).

CONCLUSION

Prolonged surgery time seems to correlate with initial postoperative hypocalcemia independently of the underlying disease and surgical expertise but does not affect the persistence of hypocalcemia. Initial symptomatic postoperative hypocalcemia after total thyroidectomy is associated with a high rate of persistent hypocalcemia.

Incidence and predictors of post-thyroidectomy hypocalcaemia in a tertiary endocrine surgical unit

BACKGROUND

Post-thyroidectomy hypocalcaemia is a common complication with significant short and long term morbidity. The aim of this study was to determine the incidence and predictors of post-thyroidectomy hypocalcaemia (as defined by a corrected calcium <2.1 mmol/l) in a tertiary endocrine surgical unit.

METHODS

A total of 238 consecutive patients who underwent completion or bilateral thyroid surgery between 2008 and 2011 were included in this retrospective study. Clinical and biochemical data were obtained from electronic and hard copy medical records.

RESULTS

The incidence of post-thyroidectomy hypocalcaemia on first postoperative day (POD1) was 29.0%. There was variation in the incidence of hypocalcaemia depending on the timing of measurement on the first postoperative day. At six months following surgery, 5.5% of patients were on calcium and/or vitamin D supplementation. Factors associated with post-thyroidectomy hypocalcaemia were lower preoperative corrected calcium (p=0.005) and parathyroid gland (PTG) auto-transplant (p=0.001). Other clinical factors such as central lymph node dissection, inadvertent PTG excision, ethnicity, preoperative diagnosis and Lugol's iodine were not associated with post-thyroidectomy hypocalcaemia.

CONCLUSION

The incidence of post-thyroidectomy hypocalcaemia was underestimated by 6% when only POD1 measurements were considered. The timing of measurement on POD1 has an impact on the incidence of post-thyroidectomy hypocalcaemia. Auto-transplantation and lower preoperative calcium were associated with post-thyroidectomy hypocalcaemia.

Systematic review and meta-analysis of predictors of post-thyroidectomy hypocalcaemia

BACKGROUND

Hypocalcaemia is common after thyroidectomy. Accurate prediction and appropriate management may help reduce morbidity and hospital stay. The aim of this study was to perform a systematic literature review and meta-analysis of predictors of post-thyroidectomy hypocalcaemia.

METHODS

A systematic search of PubMed, EMBASE and the Cochrane Library databases was undertaken, and the quality of manuscripts assessed using a modified Newcastle-Ottawa Scale.

RESULTS

Some 115 observational studies were included. The median (i.q.r.) incidence of transient and permanent hypocalcaemia was 27 (19-38) and 1 (0-3) per cent respectively. Independent predictors of transient hypocalcaemia included levels of preoperative calcium, perioperative parathyroid hormone (PTH), preoperative 25-hydroxyvitamin D and postoperative magnesium. Clinical predictors included surgery for recurrent goitre and reoperation for bleeding. A calcium level lower than 1·88 mmol/l at 24 h after surgery, identification of fewer than two parathyroid glands (PTGs) at surgery, reoperation for bleeding, Graves' disease and heavier thyroid specimens were identified as independent predictors of permanent hypocalcaemia in multivariable analysis. Factors associated with transient hypocalcaemia in meta-analyses were inadvertent PTG excision (odds ratio (OR) 1·90, 95 per cent confidence interval 1·31 to 2·74), PTG autotransplantation (OR 2·03, 1·44 to 2·86), Graves' disease (OR 1·75, 1·34 to 2·28) and female sex (OR 2·28, 1·53 to 3·40).

CONCLUSION

Perioperative PTH, preoperative vitamin D and postoperative changes in calcium are biochemical predictors of post-thyroidectomy hypocalcaemia. Clinical predictors include female sex, Graves' disease, need for parathyroid autotransplantation and inadvertent excision of PTGs.

To supplement or not to supplement: a cost-utility analysis of calcium and vitamin D repletion in patients after thyroidectomy

BACKGROUND

Postoperative hypocalcemia is the most common complication after thyroidectomy; prevention and treatment remain areas of ongoing debate. The purpose of this study was to determine the incremental cost utility of routine versus selective calcium and vitamin D supplementation after total or completion thyroidectomy.

METHODS

A cost-utility analysis using a Markov decision model was performed for a hypothetical cohort of adult patients after thyroidectomy. Routine or selective supplementation of oral calcium carbonate, vitamin D (calcitriol), and intravenous calcium gluconate, when required, was used. Selective supplementation was determined by serum intact parathyroid hormone levels. The incremental cost utility, measured in U.S. dollars per quality-adjusted life-year (QALY), was calculated.

RESULTS

In the base-case analysis, the cost of routine supplementation was $102 versus $164 for selective supplementation. Patients in the routine arm gained 0.002 QALYs compared to patients in the selective arm (0.95936 QALYs vs. 0.95725 QALYs). At the population level, this translates into a savings of $29,365/QALY (95% confidence interval, -$66,650 to -$1,772) for routine supplementation. Sensitivity analyses demonstrated that the model was most sensitive to the utility of the hypocalcemic state, postoperative rates of hypocalcemia, and cost of serum parathyroid hormone testing.

CONCLUSIONS

Routine oral calcium and calcitriol supplementation in patients after thyroidectomy seems to be less expensive and results in higher patient utility than selective supplementation. Surgeons who have very low rates of hypocalcemia in their patients may benefit less from routine supplementation.

Evidence for the role of perioperative PTH measurement after total thyroidectomy as a predictor of hypocalcemia

BACKGROUND

Total thyroidectomy is now accepted worldwide as the standard surgical procedure for the management of benign bilateral nodular thyroid disease. Hypocalcemia is the most common complication of that procedure and a variety of strategies for diagnosing and managing post-thyroidectomy hypocalcemia have been advocated. Increasingly, the use of intact parathyroid hormone (PTH) has been utilized to try to predict those patients at risk of developing post-thyroidectomy hypocalcemia.

METHODS

A Medline search of English language literature was performed and we reviewed the evidence in relation to the following three issues: the accuracy of PTH in predicting hypocalcemia, the optimal timing for measuring PTH, and the routine use of oral calcium supplements.

RESULTS

Post-thyroidectomy PTH levels accurately predict hypocalcemia but lack 100% accuracy. Progressive and severe hypocalcemia is unlikely in the setting of a normal PTH level and hence PTH can be cautiously used to facilitate discharge within 24 h for many patients. In addition, PTH levels can be used to implement early treatment with calcium and/or vitamin D supplements to reduce the incidence and severity of hypocalcemia. A single PTH measurement taken any time from 10 min to several hours postoperative will provide equally accurate results for predicting post-thyroidectomy hypocalcemia. Routine use of oral calcium supplements may reduce the incidence and severity of post-thyroidectomy hypocalcemia.

CONCLUSION

Postoperative PTH can be used to stratify the risk of patients developing hypocalcemia after thyroidectomy. In addition, the routine use of oral calcium supplements can lead to decreased incidence and severity of post-thyroidectomy hypocalcemia. Protocols based on PTH and the routine use of oral calcium supplements can lead to improved patient outcomes after thyroidectomy.

The impact of thyroidectomy on parathyroid glands: a biochemical and clinical profile

INTRODUCTION

An evaluation of PTH levels during thyroid surgery may reflect the functional status of the parathyroids and be useful in identifying patients at risk for hypocalcemia. This study aims to monitor the parathyroid function during total thyroidectomy through intra-operative serial samples for calcium and PTH.

MATERIALS AND METHODS

Forty-seven patients undergoing total thyroidectomy for different diseases were selected for the study. Patients underwent serum PTH and calcium sampling at the induction of anesthesia (T0) and after the first (T1) and the second (T2) lobectomy. Serum calcium was also drafted 24 h after the operation.

RESULTS

Mean PTH at T0, T1, and T2 was, respectively: 32.1 pg/ml, 19.6 pg/ml, and 11.5 pg/ml. PTH was significantly higher at T0 when compared to T1 (p<0.0001). It was also significantly higher at T1 than at T2 (p<0.0001). At T1 PTH levels were below the normal range in 20/47 cases (42.5%) and at T2 in 31/47 cases (66%). Twenty-four h after surgery, 8 patients (17%) demonstrated a biochemical hypocalcemia. A PTH value at T0 in the upper (>70 pg/ml) or in the lower (<20 pg/ml) limits of the normal range was statistically related to post-operative hypocalcemia (p=0.017).

DISCUSSION

The study seems to confirm that serum PTH during thyroidectomy does not represent a sensitive tool in precociously identifying hypocalcemic patients. Nevertheless, before surgery, a PTH concentration at the higher or lower normal limit may help to identify patients "at risk" of developing hypocalcemia.

Parathyroid hormone levels 4 hours after surgery do not accurately predict post-thyroidectomy hypocalcemia

BACKGROUND

We evaluated the reliability of intact parathyroid hormone (iPTH) levels 4 hours after thyroidectomy (4h-iPTH) as a predictor of hypocalcemia in a large series of patients.

METHODS

A prospective experimental design involving 523 consecutive patients between September 1, 2004, and June 30, 2005, was employed. The specificity, sensitivity, and overall accuracy of 4h-iPTH in predicting post-thyroidectomy hypocalcemia and symptoms were determined.

RESULTS

A total of 199 patients developed hypocalcemia (serum calcium concentrations <8.0 mg/dl). Five patients still were receiving vitamin D/oral calcium at 6 months after the operation. Seventy-three patients experienced mild symptoms. The 4h-iPTH levels were reduced in hypocalcemic patients (28.8 +/- 15.3 vs 11.2 +/- 11.6 pg/ml) (P < .001). The 4h-iPTH levels were within the normal range (10 to 65 pg/ml) in 360 patients (290 normocalcemic) and subnormal in 163 patients (129 hypocalcemic, of whom 62 were symptomatic). The accuracy of 4h-iPTH levels <10 pg/ml in predicting post-thyroidectomy hypocalcemia and symptoms was 80.1% and 78.6%, respectively. False-negative results were observed in 70 hypocalcemic patients (13.4%), 11 of whom were symptomatic (2.1%).

CONCLUSIONS

Subnormal 4h-iPTH levels alone did not accurately predict clinically relevant postoperative hypocalcemia. The optimal cut-off level and its integration with preoperative and postoperative serum calcium concentrations should be reconsidered.