Hemodynamic, metabolic, and ultrastructural consequences of hyperosmolal mannitol after myocardial anoxia

Recovery from anoxia has been evaluated in the isovolumic nonrecirculating paced perfused rat heart. Seventy studies were performed consisting of 1) 15 min of aerobic perfusion (AP), 2) AP + 15 min of anoxic perfusion, 3) AP + 15 min of anoxic perfusion + 15 min of reoxygenation. Krebs-Ringer-bicarbonate + 5 mM glucose (KRB) was compared with KRB + mannitol (osmolality, +60 mOsm). Mannitol decreased myocardial water content. It improved recovery of hemodynamic function after reoxygenation. With KRB alone left ventricular systolic peak pressure (LVSp) decreased by 32 percent and maximum dP/dt by 50 percent. With mannitol added LVSp decreased 18 percent and dP/dt 21 percent (p less than 0.01). No effect on energy metabolism was demonstrated. KRB and mannitol did not differentially affect total coronary flow, lactate, and glucose extraction, tissue glycogen, creatine phosphate, or adenine nucleotide concentrations. No significant difference in capillary filling was demonstrated by microfil injection. Mannitol appears to improve LV function by direct myocardial osmotic action unrelated to enhanced energy production.