Direct effects of propofol on myocardial and vascular tissue from mature and immature rats

Objective: To determine the effect of age on the direct myocardial and vascular effects of propofol in rats. Design: Randomized, prospective with repeated measures. Setting: University research laboratory. Participants: Myocardial and aortic tissue from 12 immature (4-week-old) and 12 mature (16-week-old) male Sprague-Dawley rats. Interventions: Change in force of contraction was measured in isolated myocardial strips or in isolated descending thoracic aorta rings during exposure to propofol or intralipid. Measurements and Main Results: Propofol produced a dose-dependent decrease in vascular tone (p < 0.05). This effect was similar for intralipid. Propofol was more potent in the younger animals (EC50, 5.3 mug/mL [confidence interval, 2.5 to 11.1] for 4-week-old and 26.6 mug/mL [confidence interval, 6.8 to 103.7] for 16-week-old rats; p < 0.05). In contrast, propofol produced a dose-dependent decrease in contractility (p = 0.001), whereas intralipid produced no decrease in contractility. Conclusions: Although propofol does produce a dose-dependent decrease in contractility, this effect is similar at different ages. Propofol produces more direct vascular relaxation in the immature tissue. Propofol's direct cardiovascular effect and its indirect cardiovascular effects should be considered in the young and old, especially when cardiovascular reserve is limited. Copyright (C) 2001 by W.B. Saunders Company.