Methohexitone anaesthesia for microlaryngoscopy: circulatory modulation with metoprolol and dihydralazine.
Anaesthesia for microlaryngoscopy was induced and maintained with fentanyl 3 micrograms kg-1 and methohexitone (initial bolus of 1-1.5 mg kg-1 plus subsequent infusion of 4 mg kg-1 h-1). Suxamethonium was used to induce neuromuscular blockade. Twenty minutes before induction of anaesthesia, previously normotensive patients (n = 35), and patients with hypertension well controlled by beta-receptor antagonists (n = 16) were pretreated with metoprolol (M) 0.2 mg kg-1 i.v. and dihydralazine (DH) 0.2 mg kg-1 i.v., dihydralazine 0.2 mg kg-1 i.v. alone, or saline. Arterial pressure (AP) and heart rate (HR) were monitored: any arrhythmia and ST60-T changes were noted. After the methohexitone infusion was stopped, the times for emergence and full recovery were short (median 2 min 15 s and 5 min later, respectively). Pretreatment with M + DH abolished increases in AP and HR during endoscopy. Arrhythmias were observed in fewer pretreated patients than in controls (P less than 0.05). ST60-T changes in the ECG indicating myocardial ischaemia were found in two of 19 M + DH and in six of 21 saline-pretreated patients. One of these six patients developed a myocardial infarction. Pretreatment with dihydralazine alone attenuated the pressor response to microlaryngoscopy, but was associated with consistently high HR and an incidence of arrhythmias as well as ST60-T changes similar to that found after saline.
D000368:Aged; D000771:Anesthesia, Intravenous; D001145:Arrhythmias, Cardiac / Q000517:prevention & control; D001794:Blood Pressure / Q000187:drug effects; D004078:Dihydralazine / Q000627:therapeutic use*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006830:Hydralazine / Q000031:analogs & derivatives*; D007431:Intraoperative Complications / Q000517:prevention & control; D007828:Laryngoscopy; D008297:Male; D008723:Methohexital; D008790:Metoprolol / Q000627:therapeutic use*; D008875:Middle Aged; D011292:Premedication
D006830:Hydralazine; D008723:Methohexital; D008790:Metoprolol; D004078:Dihydralazine