Exogenous plasma magnesium increases during hypothermia in dogs

¹ Department of Anesthesiology, The Albany Medical College of Union University, Albany, New York

It has been reported and our observations have confirmed that during immersion hypothermia in nonhibernators the plasma magnesium level will exhibit an increase linear to the fall in core temperature. In the present study the parenteral administration of magnesium sulphate during immersion hypothermia produced increases in plasma magnesium levels, which were associated, however, with a decreased tolerance to exposure, a higher rate of ventricular fibrillation and a higher lethal temperature. It is likely that the plasma magnesium level increase, even though linear to the fall in core temperature, is not the factor which influences tolerance to exposure. The factor would rather be the ability of the organism to unload magnesium from its stores, of which ability plasma magnesium levels would be a mere reflection.