Increase in renal magnesium overflow following aortotomy-induced hemorrhage in pigs

Hemorrhage causes an increase in plasma Mg++ levels. This article identifies some of the tissues contributing to the hemorrhage induced increase in plasma Mg++. Anesthetized, splenectomized pigs were subjected to a 5 mm aortotomy. Blood samples from the abdominal aorta, inferior vena cava, pulmonary artery, hepatic portal vein, and renal vein were sampled for Mg++ changes caused by this uncontrolled hemorrhage. Aortotomy produced a rapid drop in arterial pressure and cardiac output, both of which remained depressed for the following 120 minutes (P less than 0.05). By 120 minutes, 6 of the 8 pigs survived, but three of the six survivors showed signs of cardiovascular decompensation. A significant increase in arterial plasma Mg++ was indicated by a paired t-test (P less than 0.05). Analysis of the venous samples also revealed a significant increase during the post-aortotomy period. Renal venous and hepatic portal venous plasmas both showed increases greater than that in the arterial plasma. The renal and splanchnic tissues, then, were partly responsible for the increase in the arterial Mg++ which follows hemorrhage.