Hemodynamic effects of atracurium and cisatracurium and the use of diphenhydramine and cimetidine.

BACKGROUND AND OBJECTIVES Since atracurium can cause hypotension in humans, the hemodynamic effects of atracurium and cisatracurium as well as the hemodynamic protection of diphenhydramine and cimetidine were investigated in rats. METHODS 1) Wistar rats were anesthetized with sodium pentobarbital and prepared according to Brown et al. to evaluate different doses of atracurium and cisatracurium in the reduction of T4/T1 equal or greater than 95%. 2) Assessment of the hemodynamic changes caused by the intravenous administration of atracurium and cisatracurium by monitoring the blood pressure in the carotid artery and the electrocardiogram of rats. 3) Observation of the hemodynamic protection of prior treatment with the intravenous administration of diphenhydramine (2 mg.kg(-1)) and/or cimetidine (4 mg.kg(-1)). STATISTICAL ANALYSIS Student t test and ANOVA. RESULTS Doses of 1 mg.kg(-1) and 0.25 mg.kg(-1) of atracurium and cisatracurium respectively did not change the mean arterial pressure (MAP). Doses of 4 mg.kg(-1) of atracurium and cisatracurium decreased MAP to 62.8 +/- 4.5% and 82.5 +/- 2.3% respectively when compared to control levels. When the rats were pre-treated with diphenhydramine and cimetidine, diastolic pressure was reduced to 95.4% +/- 2.5%. With cimetidine, diastolic pressure was reduced to 82.7 +/- 8.4% when compared to the control group. The effects on systolic and diastolic blood pressure were reflected in the levels of MAP. CONCLUSIONS The isolated administration of diphenhydramine and cimetidine did not prevent the reduction in mean arterial pressure induced by atracurium. However, the association of both drugs was able to prevent the hemodynamic effects of atracurium. The doses of cisatracurium used in this study did not cause a reduction in blood pressure significant enough to justify the use of the preventive measures used in the atracurium groups.