Respiratory Reflex Responses of the Larynx Differ between Sevoflurane and Propofol in Pediatric Patients

Abstract

Laryngeal and respiratory reflex responses in children aged 2-6 yr were different between sevoflurane and propofol independent of the levels of hypnosis examined in this study.

The effect of intravenous lidocaine on laryngeal and respiratory reflex responses in anaesthetised children*

“…A clinical model using laryngeal stimulation originally developed in adults [11] and adapted to the paediatric setting was applied as we have done in previous studies [10,14]. This model permits detailed analysis of reflex responses under consistent and safe examination conditions.…”

“…However, it is a commonly used premedicant and represents current standard practice in children in many institutions. Second, the results should not be extrapolated when using other anaesthetic drugs such as propofol because laryngeal and respiratory reflex responses have been demonstrated to be different when propofol is administered compared with sevoflurane [10]. Third, no control group was included in this study; however, the stability of the model over a specific time frame has been previously examined in a separate group of children anaesthetised with sevoflurane and exposed to three repeated laryngeal stimulations [19] in a similar manner to those in the present study.…”

“…Reducing the incidence of these reflexes will potentially improve the safety of anaesthesia, and administration of lidocaine in this context has been advocated for many years, even though its exact impact remains unclear [13]. Although sevoflurane is widely used in children, not least because of its ability to obtund pharyngeal and laryngeal reflexes [28], laryngospasm occurs frequently [10,19] and adjuvant medication to reduce its incidence is warranted. The results of our study suggest that the incidence of laryngospasm is decreased after the intravenous administration of lidocaine; however, the timing of administration, for example, before extubation, must be carefully planned to obtain optimum effects because it is short-acting.…”

“…For the remainder of the study period, the vaporiser settings were adjusted to maintain an end-tidal sevoflurane concentration of 2.5%. The experimental design has been described previously [10]. End-tidal sevoflurane concentration was continuously measured from a sampling line located 1 cm down the LMA shaft using a calibrated side stream gas monitor (Avance S ⁄ 5; Datex Ohmeda, Helsinki, Finland).…”

“…The laryngeal and respiratory reflex responses elicited by laryngeal stimulation were classified into the following categories, which have been adapted from previous descriptions [10,11]: (i) laryngospasm, defined as complete closure of the glottis (at the level of the vocal and ⁄ or false cords) on video images lasting more than 10 s; (ii) central apnoea, defined as apnoea without complete closure of the glottis lasting more than 10 s; (iii) cough reflex, defined as a forceful expiration following inspiration; (iv) expiration reflex, defined as a forceful expiration without a preceding inspiration; and (v) spasmodic panting, defined as rapid shallow breathing (respiratory frequency greater than 60 breaths.min ) lasting more than 10 s. The time interval between stimulation of the laryngeal mucosa and re-establishment of a stable breathing pattern was measured to evaluate the duration of laryngeal and respiratory reflex responses [12]. All events that occurred within 3 min following laryngeal stimulation were evaluated.…”