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Canadian Journal of Anaesthesia

, Volume 42, Issue 8, pp 685–690 | Cite as

Upper airway obstruction during midazolam sedation: modification by nasal CPAP

  • Natsuko Nozaki-Taguchi
  • Shiroh Isono
  • Takashi Nishino
  • Takeshi Numai
  • Noboru Taguchi
Reports of Investigation

Abstract

We examined the depressant effect of midazolam on respiration in 21 healthy women undergoing lower abdominal surgery with spinal anaesthesia. Airway gas flow, airway pressure, and the sound of snoring were recorded together with arterial oxygen saturation (SpO2. After spinal anaesthesia was established, subjects were deeply sedated with pentazocine 15 mg followed by incremental doses of midazolam 1 mg iv up to 0.1 mg · kg−1. When SpO2 decreased to < 90% or snoring and/or apnoea was observed, continuous positive airway pressure applied through the nose (nasal CPAP) was increased until the respiratory deterioration was reversed. While one patient remained free of respiratory events, the other 20 patients were successfully treated with nasal CPAP restoring normal SpO2 (95.5 ± 1.7%) without snoring. Stepwise reduction of nasal CPAP determined the minimally effective CPAP to prevent snoring to be 5.1 ±2.1 cm H2O. Further reduction of nasal CPAP induced snoring in 15 patients and obstructive apnoea in five patients with the latter accompanied by a severe reduction of SpO2 (87.4 ± 6.1%). Patients with apnoea were older than those who snored (P < 0.05). We conclude that upper airway obstruction contributes considerably to decreases in SpO2 during midazolam sedation for spinal anaesthesia.

Key words

airway: obstruction anaesthetic techniques: spinal hypnotics: benzodiazepines ventilaton: obstruction, oxygenation, continuous positive airway pressure 

Résumé

Nous avons étudié les effets dépresseurs du midazolam sur la respiration chez 21 femmes bien portantes opérées pour une chirurgie abdominale basse sous anesthésie rachidienne. Le débit et la pression des voies aériennes, ainsi que le ronflement ont été enregistrés en même temps que la saturation en oxygène (SpO2). Une fois l’anesthésie rachidienne établie, les patientes ont reçu une sédation profonde avec de la pentazocine 15 mg suivie par des doses répétées de midazolam 1 mg iv pour une dose totale de 0,1 mg · kg−1. Lorsque la SpO2 diminuait sous 90% ou qu’un ronflement avec ou sans apnée était observé, une pression positive était appliquée progressivement sur les voies aériennes par le nez (CPAP nasal) jusqu’au retour de la respiration normale. Tandis qu’une patiente ne manifestait aucun symptôme respiratoires, les 20 autres patientes étaient traitées avec succès par le CPAP nasal avec le rétablissement d’une SpO2 normale (95,5 ± 1,7%). Une diminution en paliers du CPAP nasal a permis de déterminer le CPAP minimal requis pour prévenir le ronflement qui se situe à 5,1 ± 2,1 cm H2O. La diminution subséquente du CPAP a provoqué du ronflement chez 15 des patientes et une apnée de type obstructif chez cinq des patientes qui s’est accompagnée d’une chute importante de la SpO2 (87,4 ± 6,1%). Les patientes devenues apnéiques étaient plus âgées que celles qui ronflaient (P < 0,05). Nous concluons que l’obstruction des voies aériennes supérieures contribue considérablement aux baisses de SpO2 pendant la sédation au midazolam pendant l’anesthésie rachidienne.

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Copyright information

© Canadian Anesthesiologists 1995

Authors and Affiliations

  • Natsuko Nozaki-Taguchi
    • 1
  • Shiroh Isono
    • 2
  • Takashi Nishino
    • 2
  • Takeshi Numai
    • 1
  • Noboru Taguchi
    • 2
  1. 1.Department of AnaesthesiaFunabashi Municipal Medical CentreJapan
  2. 2.Department of AnaesthesiologySchool of Medicine, Chiba UniversityChibaJapan

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