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Histamine release during morphine and fentanyl anesthesia
Abstract:
High doses of morphine produced peripheral vasodilation and frequently significant hypotension. These effects are thought to be due, in part, to the release of histamine. One putative advantage of high-dose fentanyl anesthesia is its relatively small effect on peripheral vascular resistance. In a randomized study, the authors examined the possibility that the hemodynamic differences between morphine and fentanyl might be attributable to histamine release. Fifteen patients were studied prior to coronary artery bypass surgery. Subjects received in infusion of morphine (1 mg . kg-1, iv at 100 micrograms . kg-1 . min-1 [n = 8]) or fentanyl (50 micrograms . kg-1 at 5 micrograms . kg-1 . min-1 [n = 7]). Patients in the morphine group had an average 750 per cent peak increase in plasma histamine accompanied by a significant decrease in mean arterial pressure (-27 mmHg- and systemic vascular resistance (-520 dyne . s . cm-5). The greatest decrease in systemic vascular resistance occurred in those patients with the highest levels of plasma histamine (r = -0.81). Patients in the fentanyl group had no change in plasma histamine and no decrease in arterial pressure or systemic vascular resistance. Cardiac output and heart rate were comparable between the two groups. Differences in the release of histamine account for most, if not all, of the different effects of morphine and fentanyl on the peripheral vasculature.
Insights
Morphine causes significant hypotension and vasodilation due to histamine release, unlike fentanyl. This study demonstrates histamine
Area of Science:
- Anesthesiology
- Pharmacology
- Cardiovascular Physiology
Background:
- High-dose morphine can cause peripheral vasodilation and hypotension, potentially linked to histamine release.
- Fentanyl, another anesthetic, has a minimal impact on peripheral vascular resistance, suggesting different mechanisms of action.
Purpose of the Study:
- To investigate whether histamine release accounts for the hemodynamic differences observed between high-dose morphine and fentanyl.
- To compare the effects of morphine and fentanyl on plasma histamine levels and cardiovascular parameters.
Main Methods:
- A randomized study involving 15 patients undergoing coronary artery bypass surgery.
- Patients received either morphine (1 mg/kg) or fentanyl (50 mcg/kg) infusions.
- Plasma histamine levels, mean arterial pressure, and systemic vascular resistance were measured.
Main Results:
- The morphine group exhibited a 750% increase in plasma histamine, accompanied by a significant decrease in mean arterial pressure (-27 mmHg) and systemic vascular resistance (-520 dyne·s·cm⁻⁵).
- A strong negative correlation (r = -0.81) was found between plasma histamine levels and systemic vascular resistance in the morphine group.
- The fentanyl group showed no significant changes in plasma histamine, arterial pressure, or systemic vascular resistance.
Conclusions:
- Histamine release is a primary factor explaining the differing effects of morphine and fentanyl on the peripheral vasculature.
- Fentanyl offers a hemodynamic advantage over morphine in the context of anesthesia due to minimal histamine release.