Cardiovascular effects of enflurane and asphyxia during long-term beta 1-adrenoceptor blockade.
The haemodynamic effects of enflurane (1.7% and 3.4% expiratory concentrations) were investigated in sheep (n = 6) pretreated with an infusion of metoprolol (0.2 mg X kg-1 X h-1 for 5 days) and in control animals (n = 6). Chloralose was used as basal anaesthetic. A 90 s apnoea period was included in the experiment to evaluate further the possible side-effects of long-term metoprolol treatment in combination with enflurane anaesthesia. MAC 1.0 for enflurane in the sheep was found at 1.45% end-tidal concentration by separate measurements. Before enflurane administration, the only significant differences between the two groups of animals were a lower systemic vascular resistance and a higher stroke volume during metoprolol treatment. Enflurane abolished these discrepancies in a dose-dependent fashion and similar cardiovascular depression was observed in both groups of animals at 3.4% expiratory concentration of enflurane. Metoprolol did not significantly affect the hypertensive response to apnoea during chloralose anaesthesia alone. At enflurane 1.7% expiratory concentration the apnoea response was small and only the metoprolol-treated animals showed a significant increase in left ventricular end-diastolic pressure. We conclude that 5 days of pretreatment with metoprolol in the sheep model does not significantly impair cardiovascular performance during enflurane anaesthesia.
Henriksson
B A
BA
Biber
B
B
Häggendal
J
J
Lundberg
D
D
Pontén
J
J
Rosén
K G
KG
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000633:toxicity*; D000768:Anesthesia, General; D000818:Animals; D001237:Asphyxia / Q000150:complications*; D002318:Cardiovascular Diseases / Q000209:etiology*; D004347:Drug Interactions; D004737:Enflurane / Q000008:administration & dosage / Q000633:toxicity*; D005260:Female; D008790:Metoprolol / Q000008:administration & dosage / Q000633:toxicity; D011247:Pregnancy; D012756:Sheep; D013514:Surgical Procedures, Operative
D000319:Adrenergic beta-Antagonists; D004737:Enflurane; D008790:Metoprolol