Jaw-thrust is a noxious stimulus that might induce sympathetic responses. The purpose of this study, was to evaluate the effects of jaw-thrust on sympathetic responses.

We investigated seventy three patients. Patients who received general anesthesia were randomly divided into a control group (maintenance of combined airway maneuver with head tilt, open mouth by mouthpiece, and chin-lift, n = 30) and jaw-thrust group (maintenance of head tilt, open mouth and jaw-thrust, n = 30). In the jaw-thrust group, four minutes of endoscopy-guided force to the mandible to get the best laryngeal view were applied. For the control group, the combined airway maneuver was maintained during the same period. Arterial blood pressure (AP) and heart rate (HR) were recorded at predetermined time points (1 min before anesthesia induction, 2 min after fiberoptic bronchoscopy placement, and thereafter 1 min-interval during each airway maneuver) during jaw-thrust and chin-lift maneuver. The force amplitude applied for best laryngeal view during jaw-thrust was also measured.

Peak systolic and diastolic AP increased 39.0 ± 17.6 and 39.9 ± 22.8 mmHg from the baseline (P < 0.001) in the jaw-thrust group. HR was also 32.5 ± 19.4 beats/min from the baseline (P < 0.001) in the jaw-thrust group. These remained high at all time points, compared with the control group (P < 0.01). The force magnitude applied for jaw-thrust was not correlated to the AP and HR changes (P > 0.05).

Performing the jaw-thrust maneuver induces significant sympathetic responses, irrespective of the force magnitude.