Propofol Atracurium

Leslie K., Sessler D. I., Bjorksten A. R., and Moayeri A. (1995) Mild hypothermia alters propofol pharmacokinetics and increases the duration of action of atracurium. Anesth. Analg. 80, 1007-1014. 

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). 

Avoid imnecessary stimulation, which may induce rigidity and spasms. The primary treatment for spasms and rigidity is sedation with a benzodiazepine, such as midazolam or diazepam. Additional sedation may be provided with propofol or a phenothiazine, usually chlorpromazine. In severe disease prolonged spasms and respiratory dys-fimction will necessitate tracheal intubation and mechanical ventilation will be required. If the patient has been intubated and sedation alone is inadequate to control spasms, a neuromuscular blocking drug, e.g., intermittent doses of pancuronium or a continuous infusion of atracurium, will be required. 

A 7-year-old boy with trisomy 21 (Down syndrome) had explosive coughing, 30 seconds after fentanyl 50 pg (2 pg/kg) had been injected and flushed through an intravenous cannula. The cough was unproductive and persisted in spasmodic bursts for a further 2-3 minutes until anesthesia was induced with propofol 60 mg and atracurium 15 mg intravenously. The coughing immediately ceased. A petechial rash in the conjuncti-vae and periorbital regions was subsequently noted and disappeared by the end of the first postoperative day. 

Endotracheal intubation is less traumatic when it is facilitated by a muscle relaxant. Vocal cord hematoma after intubation occurred in six of 36 patients when only fenta-nyl plus propofol was used, compared with one of 37 when atracurium was added (9). 

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). 

Fentanyl, ketamine, midazolam, > propofol, thiopental Depolarizing succinylcholine Nondepolarizing atracurium, mivacurium, tubocurarine... 

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. 

Bradycardia and asystole occurred in another patient given propofol, fentanyl and atracurium. The authors of one report suggest that atropine or glycopyrrolate pretreatment should attenuate or prevent such reactions."... 

For reports of bradycardia occurring with atracurium or suxamethonium used with propofol and fentanyl, see Anaesthetics, general + Neuromuscular blockers , p.lOl. 

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