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.
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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References
Manara AR, Smith DC, Nixon C. Sedation during spinal anaesthesia: a case for the routine administration of oxygen. Br J Anaesth 1989; 63: 343–5.
Smith DC, Crul JF. Oxygen desaturation following sedation for regional analgesia. Br J Anaesth 1989; 62: 206–9.
Caplan RA, Ward JR, Posner K, Cheney FW. Unexpected cardiac arrest during spinal anesthesia: a closed claims analysis of predisposing factors. Anesthesiology 1988; 68: 5–11.
Gauthier RA, Dyck B, Chung F, Romanelli J, Chapman KR. Respiratory interaction after spinal anesthesia and sedation with midazolam. Anesthesiology 1992; 77: 909–14.
Guilleminault C. Benzodiazepines, breathing, and sleep. Am J Med 1990; 88: 25S-28S.
Sullivan CE, Issa FG, Benhon-Jones M, Eves L. Reversal of obstructive sleep apnoea by continuous positive airway pressure applied through the nares. Lancet 1981; 1: 862–5.
Condos R, Norman RG, Krishnasamy I, Peduzzi N, Goldring RM, Rapoport DM. Flow limitation as a noninvasive assessment of residual upper-airway resistance during continuous positive airway pressure therapy of obstructive sleep apnea. Am J Respir Crit Care Med 1994; 150: 475–80.
Mihic DN, Abram SE. Optimal regional anaesthesia for abdominal hysterectomy: combined subarachnoid and epidural block compared with other regional techniques. Eur J Anaesthesiol 1993; 10: 297–301.
Chambers WA, Edstrom HH, Scott DB. Effect of baricity on spinal anaesthesia with bupivacaine. Br J Anaesth 1981; 53: 279–82.
Sinclair CJ, Scott DB, Edstrom HH. Effect of the Trendelenberg position on spinal anaesthesia with hyperbaric bupivacaine. Br J Anaesth 1982; 54: 497–500.
Isono S, Remmers JE. Anatomy and physiology of the upper airway obstruction.In: Principles and Practice of Sleep Medicine, 2nd ed. Philadelphia: WB Saunders Company, 1994; 642–56.
Burger CD, Stanson AW, Sheedy PF II, Daniels BK, Shepard JW Jr. Fast-computed tomography evaluation of age-related changes in upper airway structure and function in normal men. Am Rev Respir Dis 1992; 145: 846–52.
Nishino T, Shirahata M, Yonezawa T, Honda Y. Comparison of changes in the hypoglossal and the phrenic nerve activity in response to increasing depth of anesthesia in cats. Anesthesiology 1984; 60: 19–24.
Bonara M, St. John WM, Bledsoe TA. Differential elavation by protiptyline and depression by diazepam of upper airway respiratory motor activity. Am Rev Respir Dis 1985; 131: 41–5.
Leiter JC, Knuth SL, Krol RC, Bartlett D Jr. The effect of diazepam on genioglossal muscle activity in normal human subjects. Am Rev Respir Dis 1985; 132: 216–9.
Dolly FR, Block AJ. Effect of flurazepam on sleepdisordered breathing and nocturnal oxygen desaturation in asymptomatic subjects. Am J Med 1982; 73: 239–43.
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Nozaki-Taguchi, N., Isono, S., Nishino, T. et al. Upper airway obstruction during midazolam sedation: modification by nasal CPAP. Can J Anaesth 42, 685–690 (1995). https://doi.org/10.1007/BF03012665
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DOI: https://doi.org/10.1007/BF03012665