SummaryWe studied the effect of intravenous lidocaine on laryngeal and respiratory reflex responses in children anaesthetised with sevoflurane. We tested the hypothesis that the incidence of laryngospasm evoked by laryngeal stimulation is temporarily diminished after the administration of lidocaine. Forty children, aged between 25 and 84 months, were anaesthetised with sevoflurane and breathed spontaneously through a laryngeal mask airway. Respiratory reflex responses were elicited by spraying distilled water onto the laryngeal mucosa at three time intervals: (i) before lidocaine was administered (baseline); (ii) at 2 min and (iii) at 10 min following the intravenous administration of a bolus of lidocaine 2 mg.kg )1 . A blinded reviewer assessed the evoked responses. The incidence of laryngospasm was reduced from 38% at baseline to 15% 2 min after lidocaine administration (p < 0.02) and 18% 10 min after lidocaine administration (p = 0.10). We conclude that intravenous lidocaine significantly reduced the incidence of laryngospasm but that the effect was short-lived. Protecting the lungs from aspiration is vitally important and is largely regulated by laryngeal and respiratory reflexes such as coughing, laryngospasm, expiration reflex, spasmodic panting and apnoea. However, exaggerated upper airway reflexes, particularly laryngospasm, have the potential to cause harm [1]. An increased incidence of laryngospasm and apnoea is observed in children compared with adults and complications resulting from hypoxaemia are more common and more severe in children [2][3][4]. Lidocaine has been demonstrated to reduce the incidence of laryngospasm in anaesthetised children [5,6]; however, its effectiveness has been questioned [7,8]. Uncertainty regarding its usefulness is partly explained by the fact that most clinical studies were underpowered to assess the relatively rare event of laryngospasm. Often more common adverse effects, such as stridor and the occurrence of hypoxaemia from whatever cause, were included in analyses assessing its incidence. Furthermore, studies examining the action of intravenous lidocaine on cough suppression during tracheal intubation revealed that the effect may only last a few minutes [9]. The potentially transient nature of this effect might make evaluation in the clinical setting difficult.
Summary
Head and neck movements affect both the length of the trachea and the position of tracheal tubes. This is of relevance when using cuffed tubes because changes in the position of the tube tip may not be equal to changes in the position of the cuff. The aim of the study was to assess the impact of head and neck movement on the position of the tube tip and the cuff of newly designed, oral preformed tracheal tubes in children. The tracheas of 128 children aged 1–8 years were intubated with preformed oral tubes. The distances ‘carina‐to‐tracheal tube tip’ and ‘vocal cords‐to‐tube tip’ were measured endoscopically. These measurements were performed with the head and neck in a functional neutral position (110°), during neck flexion (80°) and neck extension (130°). Tracheal length was dependent on head and neck position: neck extension elongated the trachea (p < 0.0001), and neck flexion shortened the trachea (p < 0.0001). Neck flexion moved the tube inward and resulted in endobronchial displacement in two patients. Neck extension moved the tube outwards. While no cuff was positioned between the vocal cords, cuff movement to the cricoid area occurred frequently. Complex interactions during head and neck movement along with the fixed insertion depth of preformed tubes often cause inadvertent malpositioning of the tube tip and cuff. Further changes to tube and cuff lengths might improve the safety of oral preformed tubes in children.
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