Hypomagnesemia and Hypocalcemia after Thyroidectomy: Prospective Study

Abstract

Hypomagnesemia after total thyroidectomy has not been studied extensively. Our anecdotal experience suggests that it may be important in some patients after thyroid excision. The hypomagnesemic hypocalcemic syndrome has been described in other disease states in which a state of functional hypoparathyroidism exists. This study was designed to determine the incidence of hypomagnesemia after total thyroidectomy and relate it to hypocalcemia and symptoms during the postoperative period. A prospective study of all patients undergoing total thyroidectomy between September 1994 and July 1996 was performed. Patient data, thyroid function, retrosternal extension, initial versus reoperative surgery, operative details, parathyroid resection, and pathology were recorded. Calcium, magnesium, electrolytes, blood count, liver function tests, and albumin were measured prior to surgery and twice daily during the postoperative period. Fifty patients underwent total thyroidectomy: 68% were hypocalcemic, 72% were hypomagnesemic, and 36% were symptomatic during the postoperative period. Hypomagnesemia and gender were associated with hypocalcemia. Volume of fluid and neck dissection were associated with low magnesium levels. Hypomagnesemia and parathyroid resection were risk factors for symptoms after thyroidectomy. No patients developed permanent hypoparathyroidism. Transient hypocalcemia and hypomagnesemia occur frequently after total thyroidectomy. The etiology of this phenomenon is probably multifactorial. Patients are more likely to be symptomatic when both cations are low, and attempting to correct only hypocalcemia may prolong symptoms. It is important to monitor both calcium and magnesium levels after total thyroidectomy and to correct deficiencies to facilitate prompt resolution of symptoms.

Influence of magnesium sulphate infusion before total thyroidectomy on transient hypocalcemia — a randomised study

“…In our study, the rate of the patients with laboratory transient hypocalcemia (27%) and those with clinically transient hypocalcemia (23%) was in the interval of 6.2-68%, which was simi-lar to that reported in the literature. 2,3,14,[22][23][24][25][26] In the study by Wilson et al, in which the definitions of laboratory and clinical hypocalcemia are similar to the definitions in our study, 68% of patients were diagnosed with laboratory transient hypocalcemia and 36% of patients had symptoms of hypocalcemia. 3 They defined hypomagnesemia as serum concentration of magnesium lower than 0.7 mmol/L and the same definition was used in our study.…”

“…2,3,14,[22][23][24][25][26] In the study by Wilson et al, in which the definitions of laboratory and clinical hypocalcemia are similar to the definitions in our study, 68% of patients were diagnosed with laboratory transient hypocalcemia and 36% of patients had symptoms of hypocalcemia. 3 They defined hypomagnesemia as serum concentration of magnesium lower than 0.7 mmol/L and the same definition was used in our study. They reported that the incidence of postoperative hypomagnesemia was considerably higher (72%) than that in our patients who did not receive infusion of magnesium sulphate (2/24 patients, i.e 8%).…”

“…It is established that hypomagnesemia may well contribute to postoperative tetany after total thyroidectomy, especially with concomitant hypocalcemia. 3 Possibly, the cause of hipomagnesemia in the study by Wilson et al 3 is the volume of fluids that were given. The volume of fluids correlated with hypomagnesemia (p=0.027).…”

“…Namely, the patients with severe hypomagnesemia were given on average of 4.93 liters during the 24-hour perioperative period, compared to 4.69 liters in mild hypomagnesemia and 3.64 liters in normomagnesemia patients. 3 Our patients during the 24-hour perioperative period were given only 1.5 to 2.5 liters of fluids. There was no statistical difference of the given volume of fluids in the group of our patients who received intraoperative infusion of magnesium sulphate in comparison to the control group.…”

Evolution of blood magnesium and phosphorus ion levels following thyroidectomy and correlation with total calcium values

“…Plasma calcium correction without concurrent normalization of magnesium may prolong the clinical manifestations. 7,10 Temporary hypoparathyroidism leads to a reduction in renal reabsorption of magnesium, and expansion of the extracellular volume increases magnesium excretion. 10 According to Wilson et al, 10 10.0% of patients who undergo total thyroidectomy develop hypomagnesemia and hypocalcemia.…”