Effects of Upper Airway Anaesthesia on the Hyperdynamic Response to Tracheal Intubation

Abstract

Tracheal intubation is associated with a hyperdynamic response characterized by hypertension and tachycardia. Several drugs have been used to attenuate this response; however, anaesthetizing the superior laryngeal nerves of this purpose has not been formally studied. This study was designed to determine the effects of bilateral superior laryngeal nerve block and those of nebulized lidocaine on the hyperdynamic response to tracheal intubation. Forty-six patients were randomized, in a prospective, placebo-controlled, single blind trial, to receive bilateral superior laryngeal nerve block (SLN), nebulized lidocaine (NBL), or no intervention (CON). Blinding was achieved by placing a band-aid on the neck bilaterally all patients. A standard anaesthesia protocol was followed in all patients. Measurements of mean arterial pressure (MAP, systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were obtained pre-induction, at induction, and every minute for 10 minutes after tracheal intubation. Opioids and surgical stimuli were withheld during the study period. Tracheal intubation resulted in comparable increases in MAP, SBP, DBP, and HR among all patient groups. The maxium increases in these parameters were observed at 1-2 minutes following intubation. Although other haemodynamic variables returned to baseline, all patients continued to be tachycardiac 10 minutes after airway instrumentation. This study demonstrated that upper airway anaesthesia with either bilateral SLN block or nebulized lidocaine was ineffective by itself in attenuating the hyperdynamic response to tracheal intubation.