Alterations in plasma magnesium concentrations during liver transplantation.

Plasma magnesium concentrations were monitored during orthotopic liver transplantation. Magnesium supplementation was not given, although intraoperative calcium, potassium, and sodium bicarbonate were given as required. We found that there were significant falls in magnesium concentration to below our laboratory lower limit of normal, occurring chiefly during the anhepatic phase of surgery. Two patients with hypomagnesemia but normal potassium and calcium ion concentrations developed ventricular extrasystoles. Magnesium is a smooth muscle relaxant, dilating coronary arteries and peripheral vessels. It also exerts an antiarrhythmic effect and may have a permissive effect on the actions of catecholamines. Magnesium supplementation may be indicated during orthotopic liver transplantation because of the potentially beneficial effects and to avoid possible deleterious effects of hypomagnesemia. However, magnesium levels need to be monitored to avoid the unwanted side effects of hypermagnesemia.