Propofol Vecuronium

A 77-year-old man is admitted to the hospital for a coronary artery bypass. He has been treated with a (3-blocker (Tenormin 100 mg per day), which he took every morning. He is induced with propofol 1 mg/kg, fentanyl 5 jjig/kg and vecuronium 8 mg for muscle relaxation. After 3 minutes a decreasing heart rate becomes a worry for the anesthesiologist. The heart rate continues to fall until it reaches 38 BPM. At this point the patient s blood pressure is 80/60 and the anesthesiologist gives atropine 0.4 mg and ephedrine 10 mg. This treatment results in a stable patient. What effects were most likely produced by the anesthesia procedure Could this have been avoided ... 

Answer This feature of bradycardia is typical of patients who take (3-blockers, which should be continued so they result ultimately in better anesthetic management. The drugs given could have been modified (i.e., etomidate instead of propofol, which does not raise or may cause a slower heart rate). The potent opioids in the fentanyl family all cause vagal transmitted bradycardia. The muscle relaxant vecuronium (norcuron) has no effect on heart rate and could have been replaced by pancuronium, which has a vagolytic effect and will counter bradycardia in the usual induction bolus doses. 

In 113 patients undergoing general anesthesia, intravenous midazolam 15 mg slowed recovery of the twitch height after vecuronium and atracurium compared with diazepam. The recovery index was not altered (162). However, in another study in 20 patients, midazolam 0.3 mg/kg did not affect the duration of blockade, recovery time, intensity of fasciculations, or adequacy of relaxation for tracheal intubation produced by suxamethonium 1 mg/kg, nor the duration of blockade and adequacy of relaxation for tracheal intubation produced by pancuronium 0.025 mg/kg in incremental doses until 99% depression of muscle-twitch tension was obtained (161). Furthermore, in 60 patients undergoing maintenance anesthesia randomly assigned to one of six regimens (etomidate, fentanyl, midazolam, propofol, thiopental plus nitrous oxide, or isoflurane plus nitrous oxide), midazolam did not alter rocuronium dosage requirements (165). 

Intravenous anesthetic agents have much less influence on the neuromuscular blocking effects of relaxants and most have no clinically significant effect. However, ketamine (SEDA-14, 113) has been reported to significantly potentiate atracurium (137), and also D-tubocurarine but not pancuronium (138) in man. Animal studies suggest that all relaxants will be potentiated by ketamine in a dose-dependent manner (139,140). It has been suggested that had Johnston et al. (138) used a higher dose of ketamine (than 75 mg/m ), they would have seen potentiation of pancuronium. The main effect of ketamine appears to be a reduction in the sensitivity of the postjunctional membrane to acetylchohne, possibly by ion-channel blockade. Propofol has been reported to potentiate vecuronium-induced and atracurium-induced blocks (141). 

The inhalational anaesthetics increase the effects of the neuromuscular blockers to differing extents, but nitrous oxide appears not to interact significantly. Ketamine has been reported to potentiate the effects of atracurium. Propofol does not appear to interact with mivacurium or vecuronium. Xenon is reported not to interact with mivacurium or rocuronium, and has less effect than sevoflurane on vecuronium neuromuscular blockade. Bradycardia has been seen in patients given vecuronium with eto-midate or thiopental. Propofol can cause serious bradycardia if it is given with suxamethonium (succinylcholine) without adequate antimuscarinic premedication, and asystole has been seen when fentanyl, propofol and suxamethonium were given sequentially. 

The original formulation of propofol in Cremophor was found to increase the blockade due to vecuronium, but the more recent formulation in soybean oil and egg phosphatide has been found in an extensive study not to interact with vecuronium." Propofol also appears not to interact with mivacurium. ... 

McCardiy GJ, Mirakhur RK, Pandit SK. Lack of interaction between propofol and vecuronium, (1992) 75, 536-8. 

A 44-year-old woman was given ondansetron, vecuronium, and propofol at induction for elective surgery and immediately became hypotensive (60/30 mmHg) [35 ]. There were no accompanying skin or systemic symptoms, and the episode resolved completely after treatment with intravenous adrenaline, promethazine, hydrocortisone, and fluids. Subsequent skin prick tests with ondansetron, vecuronium, and propofol were negative, but intradermal testing with ondansetron 0.02 mg/ml produced a positive wheal reaction. 

Noninterfering alfentanil, aprotinin, atropine, bupivacaine, chlorpromazine, dalteparin, dexamethasone, diazepam, dopamine, droperidol, etomidate, fentanyl, furosemide, gallamine, haloperidol, midazolam, morphine, neostigmine, nitroglycerin, nitroprusside, oxytocin, pancuronium, pentobarbital, phenylephrine, phenytoin, pipecuronium, piperacillin, promethazine, propofol, ranitidine, succinylcholine, sufentanil, terbutaline, thiopental, vecuronium, verapamil... 

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