[Hemodynamics and myocardial contractility in experimental tourniquet-shock]

A reproducible tourniquet-shock has been produced in hind limbs of dogs by unilateral and bilateral extremity ischemia. The following parameters have been measured for analysing the function of the cardiovascular system: mean aortic pressure, heart rate, cardiac output, intraventricular pressure and left ventricular pressure. From these data the stroke volume, stroke work, total peripheral resistance and the parameters of heart contractility dp/dtmax, dp/dtmax:IP and t-dp/dtmax were derived. During the ischemic period all circulatory parameters did not change in comparison to the controls. A tourniquet-shock developed upon recirculation of the ischemically stressed extremity which was more pronounced after bilateral than after unilateral hind leg ischemia. After release of the tourniquet all animals with unilateral tourniquet survived an observation period of 5 hours duration, whereas 6 out of 8 dogs with bilateral tourniquet died of heart failure. Upon release of the tourniquet, the cardiac output raised up to 140% of the normal value: the abruptly decreasing aortic pressure was fully compensated by a tachycardia from 100 to 190 (beats/minute). The parameters dp/dtmax:IP and t-dp/dtmax indicated a distinct increase of the left ventricular contractility in the early tourniquet-syndrom. Already after 30 minutes an increasing circulatory depression developed indicative of the decrease in aortic pressure, and enddiastolic pressure. At the same time an increase of heart rate and total peripheral resistance occurred. The parameters of left ventricular contractility did not change markedly during the course of shock except for the final stage.