Local anesthetic administration for awake direct laryngoscopy. Are glossopharyngeal nerve blocks superior?

BACKGROUND

Glossopharyngeal nerve (GPN) blocks may provide reliable analgesia for awake direct laryngoscopy, although this has not been evaluated prospectively. This study was designed to determine if GPN blocks provide a superior route of local anesthetic administration for awake direct laryngoscopy as measured by hemodynamic, gag, and subjective pain responses.

METHODS

A prospective, randomized, single-blinded, crossover design was used. All participants (n = 11) were anesthesiologists. Three routes of local anesthetic administration were evaluated: 2 min of 2% viscous lidocaine swish and gargle (S&G); S&G combined with 10% lidocaine spray (S&G/spray); and S&G combined with 1% lidocaine bilateral GPN blocks (S&G/block; anterior tonsillar pillar method). Five minutes after the local anesthetic was administered, laryngoscopy was performed and sustained for 20 s. Noninvasive hemodynamic measurements and serum lidocaine concentrations were determined. Visual analogue scale scores and a poststudy questionnaire were used to assess participants' ability to tolerate local anesthetic administration and laryngoscopy and their choice for use in clinical practice.

RESULTS

No significant hemodynamic changes were observed, although there was a modest increase (< 15%) in heart rate in the S&G/block group in the first minute after laryngoscopy. Serum lidocaine concentrations were higher (P < 0.05) in the S&G/block group at 5 and 10 min (0.5 +/- 0.1 and 1.0 +/- 0.2 microgram/ml) compared with the S&G group. Participants' visual analogue scale scores, which assessed their ability to tolerate laryngoscopy, showed that S&G (5.4 +/- 0.9) resulted in more discomfort (P < 0.05) than either S&G/spray (3.5 +/- 0.9) or S&G/block (3.3 +/- 0.7). The laryngoscopist's visual analogue scale scores, which assessed the ease of visualization, revealed a trend (P < 0.08) toward less coughing and gagging with S&G/spray (1.8 +/- 0.9) compared with S&G (4.0 +/- 1.3) and S&G/block (3.7 +/- 1.1). Oropharyngeal discomfort lasting 24 h or more was reported by 91% of participants after S&G/block, whereas no participant reported oropharyngeal discomfort after S&G or S&G/spray. Significantly more participants (73%) indicated their preference for using S&G/spray in future clinical practice compared with S&G (P < 0.01) and S&G/block (P < 0.05).

CONCLUSIONS

Glossopharyngeal nerve blocks do not provide a superior route of local anesthetic administration for awake direct laryngoscopy. Two minutes of 2% viscous lidocaine S&G followed by 10% lidocaine spray was the anesthetic route preferred by participants and laryngoscopists.