Glottic views using a Miller size 0 blade are superior to those from a Macintosh size 0 blade in neonates: a randomized trial

Abstract

Introduction: Both the Miller and Macintosh blades are commonly used during laryngoscopy in infants and children, although the glottic views have not been compared in neonates. This study compared the glottic views with the Miller and Macintosh size 0 blades in neonates when the blades were placed above and below the epiglottis.

Material and methods: Forty anaesthetized and paralyzed neonates undergoing elective surgery were enrolled and randomized to either the Miller or Macintosh size 0 blade. Two glottic views were obtained in random order in each neonate and were photographed using the same blade: lifting the epiglottis first then the tongue base or vice versa. The percentage of glottic opening (POGO) scores were evaluated with each view. The POGO scores and cardiorespiratory variables were then analysed.

Results: The POGO scores using the Miller blade to lift both the epiglottis and the tongue base were similar, whereas the scores using the Macintosh blade to lift the epiglottis were greater than those to lift the tongue base. The POGO scores using the Miller blade in both positions were significantly greater than those using the Macintosh blade in the corresponding positions (P = 0.0001). The heart rate using the Miller blade was greater than that using the Macintosh blade (P = 0.0001).

Conclusions: In neonates, the glottic views using the Miller size 0 blade to lift both the epiglottis and the tongue base were deemed to be excellent and superior to those using the Macintosh blade in both positions.

Keywords: glottic view.; laryngoscope; laryngoscopy; neonate.

FIGURE 1

A) After optimizing the view of the glottis, the camera was positioned next to the laryngoscope handle of the Miller size 0 laryngoscope blade and focused on the vocal cords. B) After optimizing the view of the glottis, the camera was positioned next to the laryngoscope handle of the Macintosh size 0 laryngoscope blade and focused on the vocal cords

FIGURE 2

The POGO scores with the Miller and Macintosh size 0 blades lifting the epiglottis or the tongue base. Summary data are means and 95% confidence intervals. ^βThe POGO scores lifting the epiglottis with the Macintosh blade were less than those with the Miller blade (unpaired t-test, P = 0.0001). *The POGO scores lifting the tongue base with the Macintosh blade were less than with the Miller blade (unpaired t-test, P = 0.0001). ^∂The POGO scores with the Macintosh blade lifting the tongue base were less than those lifting the epiglottis (paired t-test, P = 0.027)

FIGURE 3

The heart rate with the Miller and Macintosh size 0 blades preand postlaryngoscopy. Summary data are means and 95% confidence intervals. * The heart rates with the Miller blade postlaryngoscopy were greater than prelaryngoscopy (paired t-test, P = 0.001). ^βThe heart rates prelaryngoscopy with the Macintosh blade were less than those with the Miller blade (unpaired t-test, P = 0.0001). ^∂The heart rates with the Macintosh blade postlaryngoscopy were less than those with the Miller blade postlaryngoscopy (paired t-test, P = 0.0001)

FIGURE 4

The mean arterial pressure (MAP) with the Miller and Macintosh size 0 blades lifting the epiglottis or the tongue base. Summary data are means and 95% confidence intervals. *The MAP with the Miller blade postlaryngoscopy was greater than those prelaryngoscopy (paired t-test, P = 0.0001). ^∂The MAP postlaryngoscopy with the Macintosh blade was less than that with the Miller blade (unpaired t-test, P = 0.003)

FIGURE 5

SpO₂ with the Miller and Macintosh size 0 blades lifting the epiglottis or the tongue base. Summary data are means and 95% confidence intervals. Numerals depict the number of neonates at each saturation value. *The SpO₂ with the Miller blade postlaryngoscopy was statistically, but not clinically, less than that prelaryngoscopy (paired t-test, P = 0.015). ^βSpO₂ with the Macintosh blade postlaryngoscopy was statistically, but not clinically, less than prelaryngoscopy (paired t-test, P = 0.03)