Hypomagnesemia in postoperative spine fusion patients.

Study Design: This was a retrospective review of 49 consecutive patient charts and a prospective study of 44 consecutive patients who underwent spinal fusion.

Objective: To determine the incidence and clinical significance of hypomagnesemia after spinal fusion.

Summary Of Background Data: Hypomagnesemia may be seen in 61% of patients in postoperative intensive care and may be associated with increased mortality. However, symptomatic hypomagnesemia is rare.

Methods: A retrospective review of the charts of 49 consecutive patients who underwent spine fusion was completed to determine postoperative magnesium levels. Twenty-seven patients with postoperative hypomagnesemia received routine magnesium replacement regardless of symptoms. Forty-four patients who underwent spine fusion were studied prospectively for postoperative hypomagnesemia. Prospectively studied observational patients who developed hypomagnesemia were treated only when clinical signs or symptoms of magnesium deficiency occurred.

Results: Postoperative hypomagnesemia occurred in 28 of 49 retrospectively studied patients who underwent spine fusion (57%) and 38 of 44 prospectively studied patients who underwent spine fusion (86%). Symptoms associated with hypomagnesemia developed in three of 44 prospectively studied and two of 49 retrospectively studied patients who underwent spine fusion (7% and 4%, respectively). The combined incidence for symptomatic hypomagnesemia was five of 93 patients. (5.4%). The majority of patients from the prospective study with postoperative hypomagnesemia were asymptomatic, and their magnesium levels returned to normal within 4 days, with or without treatment.

Conclusions: This study confirmed a high incidence of hypomagnesemia in patients who underwent spine fusion, although only 5.4% developed clinical signs or symptoms of magnesium deficiency. The cause of hypomagnesemia remains speculative.