Cardiovascular changes after the three stages of nasotracheal intubation.

BACKGROUND Nasotracheal intubation typically comprises three distinct stages: (i) nasopharyngeal intubation; (ii) direct laryngoscopy to identify the vocal cords; and (iii) the passage of the tracheal tube into the trachea. The aim of this study was to identify and compare the cardiovascular responses associated with each of these stages. METHODS Seventy-five ASA I or II patients, aged 16-65 yr, requiring nasotracheal intubation as part of their anaesthetic management, received a standardized general anaesthetic and were allocated randomly to receive either nasopharyngeal intubation or nasopharyngeal intubation plus direct laryngoscopy or full nasotracheal intubation. RESULTS There was a significant hypertensive response, compared with pre-induction levels, in all three groups. The maximum mean (SD) mean arterial pressure in the nasotracheal intubation group was 113 (17.1) mm Hg, which was significantly greater than that in the nasopharyngeal intubation (97 (13) mm Hg) (P<0.001) and in the nasopharyngeal intubation plus laryngoscopy (103 (10.3) mm Hg) (P=0.007) groups. There was no significant difference between the nasopharyngeal intubation and nasopharyngeal intubation plus laryngoscopy groups (P=0.206). A similar pattern was seen for both systolic and diastolic arterial pressure. Nasotracheal intubation caused a significant increase in maximum mean (SD) heart rate, compared with pre-induction values, whereas the other two groups caused significant falls. The heart rate in the nasotracheal intubation group (92 (16.5) beats min(-1)) was significantly greater than in the other two groups (74 (8.6) (P<0.001) and 76 (12) (P<0.001) beats min(-1) respectively). There was no significant difference in heart rates between the nasopharyngeal intubation and nasopharyngeal intubation plus laryngoscopy groups (P=0.420). CONCLUSIONS Nasopharyngeal intubation causes a significant pressor response. Stimulation of the larynx and trachea by the passage of the tracheal tube, but not direct laryngoscopy, causes a significant increase in this response.