[Cardiac energetics in hypothermia].

In isolated hearts of rats pumping a fluid against hydrostatic pressure, the effect of cooling to 27 degrees C on the mechanical efficiency (ME) and oxygen consumption (MVO2) of the heart, was studied. The ME was presented by the ratio of the heart work to the total energy expense. The latter was estimated by MVO2 measured by the polarographic method. At 27 degrees C, the ME was increased while the MVO2 of the arrested heart was decreased. MVO2 of the working heart in hypothermia was less than control by the same valve as the MVO2 of the heart arrested in hypothermia was less than MVO2 of the arrested control heart. The increase of the heart ME in hypothermia seems to be due, mainly, to reduced "rest metabolism" of the heart.