Research in Medicine

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Yamin H, Heravi A. The Hemodynamic Effects of Drugs on Myocardial Oxygen Use. Research in Medicine 1981; 7 (1) :76-79
URL: http://pejouhesh.sbmu.ac.ir/article-1-2787-en.html

The circulatory responses to high equinalgesic doses of morphine are compared with those of pethidin. The decrease in mean arterial blood pressure in case of morphine was 28p.c., with a paralleled and identical de­crease in total peripheral resistance and no negative inotropic effects. 
Pethidine decreased blood pressure 54p.c., as a result of peripheral vasodilation of 46p.c. and a sharp drop in dp/dt Max of 59p.c., indi­cating myocardial depression (dp/dt max/Ip is 14p.c. and the fall in cardiac output is 33p.c.). This drop in both cases is offset by the increase in heart rate. (morphine 27p.c.; pethidin IOlp.c.). The coronary blood flow sufficiently met the myocardial energy de­mand, which did not change with the altered haernodynamics. 
Both morphine and pethidin produce coro­nary vasodilation, indicated by increased coronary blood flow and coronary venous ox­ygen saturation. 
The mechanism for the change in vasodilation is still under discussion. It seems that in case of morphine this is due to Histamin release.