Key result
Rapid injection of propofol (0.5 min) caused a significantly greater maximal reduction in mean arterial blood pressure than slow injection (2 min) in sheep (35.7% vs 23.7%; P=0.02).
Why the study?
Does rapid injection of propofol cause more profound cardiovascular effects compared to slow injection in sheep?
RCT (n=7)
random order
Does rapid injection of propofol cause more profound cardiovascular effects compared to slow injection in sheep?
Rapid injection of propofol produces significantly higher peak arterial concentrations and greater reductions in arterial blood pressure compared to slow injection.
Answers are grounded in this paper and cite their sources.
May favor slower propofol injection to limit hypotension in sheep; leaves open translation to human anesthesia.
The influence of the bolus injection rate of propofol on its cardiovascular effects has not been extensively studied.We therefore examined the influence of the injection rate of IV bolus doses of propofol on its acute cardiovascular effects and peak blood concentrations in seven chronically instrumented sheep. Each received IV propofol (200 mg) over 2 min (slow injection) and 0.5 min (rapid injection) on separate occasions in random order. The rapid injection was associated with more profound decreases in mean arterial blood pressure than slow injection (35.7% vs 23.7% maximal reductions from baseline, respectively; P = 0.02). There were no significant differences between the injection rates for peak reductions in myocardial contractility, increases in heart rate, or degree of respiratory depression. Concurrently, the rapid injections were associated with significantly higher arterial (26.9 vs 11.9 mg/L) propofol concentrations in a manner consistent with indicator dilution principles. There were no differences in the peak coronary sinus concentrations between the injection rates. We conclude that the rapid injection of propofol in the context of the induction of anesthesia produced significantly higher peak arterial propofol concentrations and suggest that it is these higher concentrations that produced relatively greater reductions in arterial blood pressure from rapid injections. Implications: Propofol is injected into a vein to initiate anesthesia. It can cause a rapid decrease in blood pressure, which may be dangerous to the patient. We examined the effect of rapid and slow injection rates of propofol in sheep and found that rapid injection caused a greater decrease in blood pressure. This was because rapid injection caused higher concentrations of propofol in the blood immediately after the injection. We believe that if the same processes occur in humans, there may be little advantage in injecting propofol rapidly. (Anesth Analg 1998;86:1109-15)
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Zheng et al. (1998) conducted an RCT in Anesthesia induction (n=7). Rapid injection of propofol vs. Slow injection of propofol (200 mg over 2 min) was evaluated on Maximal reduction from baseline in mean arterial blood pressure (p=0.02). Rapid injection of propofol (0.5 min) caused a significantly greater maximal reduction in mean arterial blood pressure than slow injection (2 min) in sheep (35.7% vs 23.7%; P=0.02).
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