Pulmonary reactivity to methacholine during beta-adrenergic blockade: propranolol versus esmolol.
Pulmonary reactivity to methacholine after equipotent beta-blocking doses of propranolol and esmolol was compared in seven basenji-greyhound dogs during thiopental-fentanyl anesthesia. Equipotent doses of esmolol and propranolol were determined by both heart rate effects and by isoproterenol response curves. Propranolol (2 mg/kg) was administered intravenously as a bolus dose and esmolol (0.4-0.5 mg.kg-1.min-1) was administered by continuous infusion. Both esmolol and propranolol significantly decreased heart rate and mean arterial pressure (P less than 0.001). Baseline pulmonary resistance and dynamic compliance did not change after the administration of either propranolol or esmolol. However, propranolol significantly shifted the methacholine dose-response curve to the left so that methacholine (0.3 mg/ml) increased pulmonary resistance by 7.9 +/- 0.97 cmH2O.l-1.s-1 (mean +/- SEM of seven dogs) after pretreatment with propranolol but only 4.4 +/- 0.89 cmH2O.l-1.s-1 (P less than 0.05) without propranolol pretreatment (control). Esmolol, however, did not significantly shift the methacholine dose-response curve. Methacholine (0.3 mg/ml) increased resistance 4.0 +/- 0.89 cmH2O.l-1.s-1 during esmolol administration. This study shows that at equipotent beta 1-blocking doses, propranolol, but not esmolol, produces significant increases in pulmonary reactivity to methacholine.
Tobias
J D
JD
Department of Anesthesiology/Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland.
Sauder
R A
RA
Hirshman
C A
CA
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000768:Anesthesia, General; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005283:Fentanyl; D006339:Heart Rate / Q000187:drug effects*; D007545:Isoproterenol; D008168:Lung / Q000187:drug effects*; D016210:Methacholine Chloride; D008688:Methacholine Compounds / Q000494:pharmacology*; D011412:Propanolamines / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology*; D013874:Thiopental
D000319:Adrenergic beta-Antagonists; D008688:Methacholine Compounds; D011412:Propanolamines; D016210:Methacholine Chloride; D011433:Propranolol; D013874:Thiopental; D007545:Isoproterenol; C036604:esmolol; D005283:Fentanyl