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Does propranolol alter the vascular response to phenylephrine before or during halothane anaesthesia in patients with
Insights
Preoperative propranolol did not increase blood pressure responses to phenylephrine in patients undergoing coronary artery bypass surgery. The incidence of postoperative hypertension was similar between patients on propranolol and those not on cardiovascular medications.
Area of Science:
- Cardiovascular Anesthesiology
- Pharmacology
- Cardiac Surgery
Background:
- Preoperative beta-blockade with propranolol may contribute to postoperative hypertension after coronary artery bypass surgery (CABG) by allowing unopposed alpha-adrenergic stimulation.
- This unopposed stimulation could lead to an exaggerated hemodynamic response to alpha-adrenergic agonists like phenylephrine (PHE).
Purpose of the Study:
- To investigate the cardiovascular response to phenylephrine infusion in patients undergoing elective CABG.
- To compare the hemodynamic effects of PHE in patients on chronic propranolol therapy versus those not taking cardiovascular medications.
Main Methods:
- Cardiovascular response to phenylephrine (PHE) infusion at escalating doses (30, 40, 50 µg/min) was measured.
- Measurements were taken before and during halothane anesthesia, prior to surgical stimulation in elective CABG patients.
- Patients were stratified into two groups: those on chronic propranolol therapy and those not taking any cardiovascular medications.
Main Results:
- Chronic propranolol therapy did not significantly alter the hemodynamic response to phenylephrine.
- This finding held true both before and during halothane anesthesia.
- The incidence of postoperative hypertension requiring vasodilator therapy was comparable between the propranolol and non-medicated groups.
Conclusions:
- Preoperative propranolol therapy does not appear to potentiate the hypertensive response to phenylephrine in patients undergoing CABG.
- The use of propranolol does not increase the risk of postoperative hypertension in this surgical context.
Abstract:
Preoperative beta-adrenergic blockade with propranolol, by allowing unopposed alpha-adrenergic stimulation in response to stress, has been suggested as a factor contributing to hypertension following coronary artery bypass surgery (CABG). Thus, one might expect to find an exaggerated haemodynamic response to phenylephrine (PHE), an alpha 1 agonist. To study this, the cardiovascular response to PHE infusion at 30, 40, and 50 microgram.min-1 prior to and during halothane anaesthesia was measured before surgical stimulation during elective CABG in patients taking chronic propranolol therapy and compared with that of patients not taking any cardiovascular medications. Chronic propranolol therapy did not alter the haemodynamic response to PHE, before or during halothane anaesthesia, and the incidence of postoperative hypertension requiring vasodilator therapy was the same for both groups.