[Myocardial cells action potential and contractive function in hemorrhagic shock in rabbits]

Anesthetized rabbits were subjected to a moderate degree of hemorrhagic shock. Lowering their mean arterial pressure to 5.3 KPa for 3 h, we measured the mean arterial pressure (MBP), left ventricular systolic pressure (LVSP), left ventricular maximum velocities of contraction (dp/dtmax), and myocardial electrical activity. The results of this study demonstrated that LVSP declined in parallel with MBP; that dp/dtmax dropped acutely on the instant of hemorrhagic shock; dp/dtmax went up by 48% on 15 min after shock; then dp/dtmax fell gradually, and by 3 h after shock the dp/dtmax values dropped to 20% of the baseline values; that intracellular sodium and potassium contents increased significantly in the hemorrhagic shocked rabbits; that myocardial resting potential (RP) and action potential amplitude (APH) diminished; and that action potential duration(APD), action potential repolarized 50% duration (APD 50), and repolarized 90% duration (APD 90) were markedly prolonged in the hemorrhagic shock, compared with control. The results suggested that in hemorrhagic shock myocardial cells fast sodium channel was closed while slow sodium and slow calcium channels, were opened; thus sodium and calcium infused and potassium exuded.