Risk assessment for severe postoperative hypocalcaemia after neck exploration for primary hyperparathyroidism

Abstract

Background and Aims: A further development of the risk profile for severe postoperative hypocalcaemia after surgery for primary hyperparathyroidism (pHPT) was made with the aim of expanding the group of patients who can be discharged safely after 23 hours. Methods: Prospective study with 156 consecutive pHPT patients (158 operations) during 2001 and 2002. Risk factors for postoperative severe hypocalcaemia (ionised calcium < 1 mmol/L), were (1) preoperative concentration of parathyroid hormone (PTH) > 35 pmol/L (five times the upper reference value, reference range 1.1 to 6.9), (2) history of previous neck surgery, (3) biopsy/excision of > 2 parathyroid glands or (4) concomitant thyroid surgery. Results: The risk factors showed a sensitivity of 100% (9/9). In 110 of the operations (70%) no risk factors were identified. Postoperative calcium levels were significantly lower after 48 operations with risk factor(s) identified, as compared to the group without risk factors (p < 0.01). Seven of 17 patients (41%) with PTH > 35 pmol/L developed severe postoperative hypocalcaemia. Two of 31 patients (6%) with PTH < 35 pmol/L in the presence of other risk factor(s) developed severe postoperative hypocalcaemia. Conclusion: Patients with no risk factor can safely been discharged from hospital on the first postoperative day. Patients with preoperative concentration of PTH > 35 pmol/L (five times the upper reference value) should stay in hospital until nadir level of calcium is reached. Patients with concentration of parathyroid hormone less than 35 pmol/L in the presence of other risk factor(s) may have an early discharge from hospital (second postoperative day) combined with outpatient measurements of calcium levels.