Recovery of the swallowing reflex after propofol anesthesia

The swallowing reflex is depressed by anesthetics. During recovery from anesthesia the rapid return of laryngeal and upper airway reflexes is important to protect the lower airway from aspiration. This study measures the recovery of the swallowing reflex after propofol anesthesia. Fifteen patients undergoing a colonoscopy under general anesthesia were studied. No premedication was given. Anesthesia was induced with propofol 2 mg/kg followed by an infusion of 10 mg.kg-1.h-1. The swallowing reflex was measured every 3 min after the end of propofol infusion for 30 min. To initiate swallowing, 0.3 mL of distilled water was injected into the pharynx at two different speeds: a slow injection over 3 s, and a bolus injection. The swallowing reflex was determined by measuring the latency period (i.e., time from water injection to start of electromyographic (EMG) activity measured in the glossal muscles). Swallowing activity was determined by integration of the EMG (EMGi) of the glossal muscles during swallowing. The latency periods after slow and bolus injections were significantly increased for the first 12 min after the end of the propofol infusion and returned to control (preanesthetic values) at 24 min. The EMGi was significantly decreased over the first 12 min and returned to control at 21 min. Propofol depresses the swallowing reflex, but complete recovery is rapid. This study suggests that the oral intake could be allowed early after recovery from anesthesia when propofol is used as the sole anesthetic.