Tracheal Intubation Without Use of Muscle Relaxants: Comparison of Remifentanil and Alfentanil

My objective is to analyze the efficiency of remifentanil-propofol and alfentanil-propofol combinations for laryngoscopic endotracheal intubation in the absence of muscle relaxants. This analysis reviews the work by Imani et al. (1). Muscle relaxants are frequently used to facilitate endotracheal intubation during anesthesia induction. However, the administration of short-acting depolarizing muscle relaxants is closely related to postoperative myalgias, malignant hyperthermia, hyperkalemia, and increased intracranial or intraocular pressure. Using non-depolarizing muscle relaxants may produce prolonged neuromuscular blockade, potentiate histamine release, increase the side effects from anticholinesterases used for reversing the agents, and lead to an inability to quickly reverse the blockade in the event of an unexpected difficult intubation. When using muscle relaxants is undesirable or contraindicated, it is important to administer other, proper induction agents to provide good intubating conditions (1, 2). Studies have investigated the use of propofol alone and propofol combined with other drugs (usually fentanyl, alfentanil, or remifentanil) for intubation without using a neuromuscular blockade; the findings have shown that intubation with all of these methods were successful (1-3). In another study, a dose of 2.5 mg/kg of propofol was applied without the use of a neuromuscular blockade, but only 20% of the patients had sufficient intubation scores (4). To decrease the necessary propofol dosage, eliminate unintented effects and to increase the potential of propofol’s effectiveness, propofol is often used together with opioids for intubation without a neuromuscular blockade. It has been reported that intubation scores were insufficient in the 17% of patients who were given fentanyl (1, 5). Alfentanil combined with propofol for intubation without a neuromuscular blockade may cause muscle rigidity and, especially at high doses, may lead to cardiovascular depression. Additionally, prolonging the effect of alfentanil after short-term operations is also undesirable (5, 6). Remifentanil is a phenyl-piperidine derivative that was first introduced into clinical practice in 1996. Remifentanil is 20 to 30 times more potent than alfentanil and its elimination half life is 3.8-8.3 minutes. Compared to alfentanil, remifentanil’s effect reduces much more quickly after intubation; this is an important advantage Copyright c 2012 Kowsar M. P. Co. All rights reserved.