RESUMO
The induction agents produce various effects to cardiovascular system. Among these, thio- pental, propofol, and etomidate produce reduction in cardiac output and peripheral vascular resistance. As a result severe systemic arterial hypotension is evoked. This phenomenon results from combined effects of CNS, cardiovascular and peripheral vascular systems. The purpose of this study was to obeserve direct effects of thiopental, propofol, etomidate in isolated rat aorta and pulmonary artery. Isometric tension was recorded in rat aortic and pulmonary artery ring preparation contracted by norepinephrine(1.8x10-6) . Thereafter thiopental, etomidate, propofol was added to organ bath. And the contractile or relaxing response was observed. Thiopental relaxed aortic ring by 3.6+/-1.3%(low dose), 3.9+/-1.4%(high dose), etomidate relaxed aortic ring by 2.0+/-0.7%(low dose), 5.4+/-2.8% (high dose), respectively. It was statistically insignificant. However, propofol relaxed aortic ring by 12.7+/-3.8%(low dose), 14.7+/-2.7%(high dose), respectively(p <0.05). Thiopental relaxed pulmonary artery ring by 4.8+/-1.1%(low dose), 5.1+/-2.3%(high dose), etomidate relaxed pulmonary artery ring by 4.8+/-1.1%(low dose), 5.1+/-2.3%(high dose), respectively. It was statistically insignificant. However, propofol relaxed pulmonary artery ring by 8.4+/-2.4%(low dose), 10.4+/-3.6(high dose), respectively( p<0.05). The results suggest that hypotension after propofol administration was due to direct vascular smooth muscle relaxation.