Life-threatening tertiary hyperparathyroidism in the critically ill

Hypercalcemia in the Intensive Care Unit: A Review of Pathophysiology, Diagnosis, and Modern Therapy

Hypercalcemia may be seen in a variety of clinical settings and often requires intensive management when serum calcium levels are dramatically elevated. All of the many etiologies of mild hypercalcemia can lead to severe hypercalcemia. Knowledge of the physiologic mechanisms involved in maintaining normocalcemia and basic pathophysiology is essential for making a timely diagnosis and hence prompt institution of etiology-specific therapy. The development of new medications and critical reviews of traditional therapies have changed the treatment paradigm for severe hypercalcemia, calling for a more limited role for aggressive isotonic fluid administration and furosemide and an expanded role for calcitonin and the bisphosphonates. Experimental therapies such as denosumab show promise.

Multivariate analysis of clinical, demographic, and laboratory data for classification of disorders of calcium homeostasis

Parathyroid hormone (PTH) nomograms combine total calcium and intact PTH (iPTH) measurements to classify disorders of calcium homeostasis. Our objective was to determine if using a combination of laboratory, demographic, and clinical parameters improves the accuracy of classification of these disorders. Chart data were collected for 236 patients with physician-ordered iPTH and total calcium tests. Classification was done using 3 approaches: (1) PTH nomogram plotting total calcium and iPTH results against known cases; (2) review of all available chart data ("gold standard"); and (3) multivariate model (classification and regression tree [CART] or logistic regression) using 24 variables. The CART model was developed using the gold standard patient classification and validated using leave-one-out cross-validation. The CART model was significantly (P = .002) more accurate (80.6%) than the PTH nomogram (59.7%) and logistic regression (66.2%) at classifying calcium homeostasis disorders. The CART model used 6 of 24 variables (iPTH, calcium, creatinine, renal transplantation, percentage of females, and urea nitrogen) and had a misclassification error rate of 0.194 (27/139). Classification of disorders of calcium homeostasis based on the PTH nomogram can be improved by using the CART model developed in this study.

Late association of hyperparathyroidism in septic patients with multiple organ failure

BACKGROUND

Hypocalcemia after severe shock or sepsis stimulates release of parathyroid hormone (PTH), which abates with recovery. Sustained sepsis with multiple organ failure (MOF), however, may cause a resurgent release of PTH and life-threatening hypercalcemia.

METHODS

Thirty critically ill patients with prolonged sepsis developed combined hypercalcemia with elevated serum PTH levels. The primary insult was trauma in 12 patients, peritonitis in 14, and pancreatitis in 4. MOF involved the lungs in 30 patients, kidney in 16, gut in 30, brain in 13, and a coagulopathy in 10. There were 12 deaths; hospital stay averaged 81 days.

RESULTS

Hypercalcemia with increased serum levels of PTH occurred usually 3-4 weeks after the septic insult. Bradycardia, thought to be caused by the hypercalcemia, occurred in 19 patients, was attributed to a vasovagal reaction, and was treated with atropine. When asystole resulted, epinephrine and cardiopulmonary resuscitation were administered. Five patients required placement of an intravenous pacemaker. Bradycardia was acutely lethal in 4 patients; in a 5th patient, the decision was made for comfort care alone, and he died 9 days later. Bisphosphonate was given to 7 patients with this hypercalcemic-induced bradycardia and, prophylactically, to prevent bradycardia in 9 others. Hypercalcemia corrected in all patients; bradycardia abated in 7 patients.

CONCLUSION

Hyperparathyroidism may occur with MOF secondary to sepsis. The mechanism is unclear, but the resultant bradycardia can be life threatening. Treatment with bisphosphonate corrects the hypercalcemia and bradycardia. Both the hypercalcemia and the bradycardia normalize when the MOF resolves.

A review of primary hyperparathyroidism

Primary hyperparathyroidism is the inappropriate secretion of parathyroid hormone and is the most common cause of hypercalcemia. Most patients with primary hyperparathyroidism are asymptomatic, and the disease is more common in postmenopausal women than in older men. Primary hyperparathyroidism can be treated with medication and long-term monitoring; however, surgical removal of the affected parathyroid gland is the definitive treatment. Rarely occurring, parathyroid crisis must be treated promptly to prevent deleterious effects to the patient. The patient experiencing parathyroid crisis benefits from the infusion nurse's knowledge of drug and fluid therapies and expertise in peripheral access.