Hypomagnesemia predicts postoperative biochemical hypocalcemia after thyroidectomy

Abstract

BackgroundTo investigate the role of magnesium in biochemical and symptomatic hypocalcemia, a retrospective study was conducted.MethodsLess-than-total thyroidectomy patients were excluded from the final analysis. Identified the risk factors of biochemical and symptomatic hypocalcemia, and investigated the correlation by logistic regression and correlation test respectively.ResultsA total of 304 patients were included in the final analysis. General incidence of hypomagnesemia was 23.36%. Logistic regression showed that gender (female) (OR = 2.238, p = 0.015) and postoperative hypomagnesemia (OR = 2.010, p = 0.017) were independent risk factors for biochemical hypocalcemia. Both Pearson and partial correlation tests indicated there was indeed significant relation between calcium and magnesium. However, relative decreasing of iPTH (>70%) (6.691, p < 0.001) and hypocalcemia (2.222, p = 0.046) were identified as risk factors of symptomatic hypocalcemia. The difference remained significant even in normoparathyroidism patients.ConclusionsPostoperative hypomagnesemia was independent risk factor of biochemical hypocalcemia. Relative decline of iPTH was predominating in predicting symptomatic hypocalcemia.

Perioperative magnesium levels in total thyroidectomy and relationship to hypocalcemia

“…In a previous paper, we reported hypomagnesemia (<0.7 mmol/L) to be a relatively common (12.9%) occurrence after thyroidectomy, and to be a strong predictor of post‐thyroidectomy hypocalcemia . Other authors have reported similar findings . In our previous paper, we examined the association between magnesium levels taken on the first postoperative day and incidence of biochemical and symptomatic hypocalcemia during the course of the 2‐night postoperative stay .…”

“…hypocalcemia, as it was not an independent predictor when included with postoperative PTH levels in multivariate analysis; however, it was a significant predictor on univariate analysis. 16 Another potential issue with Wang's study, as well as some other studies, 13 was that only patients with abnormal calcium levels on POD1, or who became symptomatic, underwent further calcium measurements. Thus, it is possible many cases of biochemical hypocalcemia may have been missed, given that in many cases calcium levels may not drop below normal until POD2 or later.…”

“…In our previous publication, we examined association between POD1 magnesium levels and incidence of hypocalcemia over the course of a 2‐night hospital stay . Luo and Wang also used POD1 magnesium measurements . Other authors measured magnesium levels at numerous time points, but the time points of the index magnesium level used for predicting hypocalcemia is not clear .…”

“…1 Luo and Wang also used POD1 magnesium measurements. 13,16 Other authors measured magnesium levels at numerous time points, but the time points of the index magnesium level used for predicting hypocalcemia is not clear. 5,17 Hammerstad examined magnesium levels at 48 hours postoperatively and reported significantly lower levels among patients developing permanent hypomagnesemia.…”

“…1 Other authors have reported similar findings. 2,5,[13][14][15] In our previous paper, we examined the association between magnesium levels taken on the first postoperative day and incidence of biochemical and symptomatic hypocalcemia during the course of the 2-night postoperative stay. 1 Less is known, however, regarding the trend of magnesium levels after thyroidectomy, and the correlation of same with trends in calcium levels.…”