Prevalence and prognostic importance of hypomagnesemia and hypocalcemia inhorses that have colic surgery

Objective-To determine the prevalence of hypomagnesemia and hypocalcemia in horses with surgical colic. Animals-35 horses with surgically managed colic. Procedure-Serum concentrations of total magnesium (tMg(2+)) and calcium (tC a(2+)), as well as ionized magnesium (iMg(2+)) and calcium (iCa(2+)) were a nalyzed before surgery and 1, 3, 5, and 7 days following surgery. A lead-II ECG and pertinent clinical data were also obtained at each time. Results-Preoperative serum tMg(2+) and iMg(2+) concentrations were below th e reference range in 6 (17%) and 19 (54%) horses, respectively. Serum conce ntrations of tCa(2+) and iCa(2+) were less than the reference range in 20 ( 57%) and 30 (86%) horses before surgery. Horses with strangulating lesions of the gastrointestinal tract had significantly lower preoperative serum co ncentrations of iMg(2+) and iCa(2+), as well as a higher heart rate than ho rses with nonstrangulating lesions. Horses that developed postoperative ile us had significantly lower serum concentrations of iMg(2+) after surgery. S erum concentrations of magnesium and calcium (total and ionized) correlated significantly with the PR, QRS, QT, and corrected QT (QTc) intervals. Hors es that were euthanatized at the time of surgery (n = 7) had significantly lower preoperative serum concentrations of iMg(2+), compared with horses th at survived. Neither serum magnesium nor calcium concentrations were predic tors of hospitalization time or survival. Conclusions and Clinical Relevance-Hypomagnesemia and hypocalcemia were com mon during the perioperative period, particularly in horses with strangulat ing intestinal lesions and ileus. Serum concentrations of tMg(2+) and tCa(2 +) were less sensitive than iMg(2+) and iCa(2+) in detecting horses with hy pomagnesemia and hypocalcemia.