Tracheal intubation without the use of muscle relaxants: A technique using propofol and varying doses of alfentanil

We have noted that tracheal intubation can be accomplished in many patients after induction of anesthesia with propofol and alfentanil without the simultaneous use of muscle relaxants. This study was designed to evaluate airway and intubating conditions after administration of propofol and alfentanil in 75 ASA physical status I or II outpatients with Mallampati class I airways undergoing various surgical procedures. The patients were randomly assigned to one of five groups for induction of anesthesia. All patients received midazolam 1 mg IV before induction of anesthesia. Group I patients (n = 15) received d-tubocurarine 3 mg, thiamylal 4 mg/kg, and succinylcholine 1 mg/kg IV. Groups II-V patients (n = 15 each) received alfentanil 30, 40, 50, or 60 μg/kg followed by propofol 2 mg/kg IV. No muscle relaxants were given to patients in groups II-V. Airway management was performed by one of the authors who was blinded as to the dose of alfentanil administered. After loss of consciousness, patients' lungs were ventilated via face mask, and the ease of ventilation was recorded. Jaw mobility was also assessed. Ninety seconds after administration of the propofol or thiamylal, laryngoscopy was performed and exposure of the glottis and position of the vocal cords were noted. Intubation of the trachea was performed and patient response was noted. Heart rate and arterial blood pressure were also recorded before induction of anesthesia, after induction, and then again after intubation of the trachea. The lungs of all patients were easily ventilated via mask, and the jaw was judged to be relaxed in all patients. In group II (30 μg/kg alfentanil), 5 of 15 patients' tracheas could not be intubated because of poor exposure of the cords or the presence of closed vocal cords. In all other groups, vocal cord position was significantly more often favorable for tracheal intubation compared with the 30 μg/kg allentanil group. In patients given alfentanil, the incidence of persistent coughing or movement after intubation of the trachea was most frequent with the 30-μg/kg dose of alfentanil. All patients receiving alfentanil had significant decreases in heart rate and arterial blood pressure after induction of anesthesia compared with preinduction values. However, there were no differences between the alfentanil groups. Patients who received thiamylal and succinylcholine had significant increases in heart rate after induction of anesthesia compared with preinduction values. Mean arterial pressure increased significantly after laryngoscopy and intubation of the trachea compared with postinduction values in patients receiving thiamylal and succinylcholine. We conclude that in premedicated outpatients with favorable airway anatomy receiving alfentanil (>30 μg/kg) and propofol for induction, ventilation via mask, jaw mobility, exposure of the vocal cords, position of the cords during laryngoscopy, and patient response to intubation of the trachea differs little from that achieved with thiamylal and succinylcholine.