The disposable Ambu aScope vs. a conventional flexible videoscope for awake intubation -- a randomised study.

BACKGROUND: A new disposable flexible videoscope, the Ambu® aScope, has several potential advantages compared with reusable devices, but it is a prerequisite for its widespread use that it functions sufficiently well in the management of patients in whom difficulty with airway management is anticipated and awake intubation is indicated. METHODS: In a pilot study, 20 patients with normal airways were intubated with the aScope. Subsequently, 40 patients with predicted difficult tracheal intubation were randomly assigned to be intubated awake with either the aScope or the reusable Olympus BF videobronchoscope. RESULTS: All patients were successfully intubated awake. The median total intubation time, including the administration of local anaesthesia, was 278 vs. 234 s in the aScope and Olympus groups, respectively (P = 0.03). In two cases in the aScope group, the image became blurred immediately after the first injection of lidocaine via the injection channel, and the time that it took to replace the scopes was included in the intubation times. CONCLUSION: Both the disposable aScope and the reusable Olympus videoscope allowed safe awake intubation in our elective patients with severely difficult, but uncompromised, airways. The occasional need to employ a spare scope because of malfunctioning would make the disposable aScope less suitable in patients with acutely compromised airways.

Laryngeal morbidity after tracheal intubation: the Endoflex(®) tube compared to conventional endotracheal intubation with stylet.

BACKGROUND: Tracheal intubation may cause vocal fold damage. The trial was designed to assess laryngeal morbidity comparing the Endoflex(®) tube with a conventional endotracheal tube with stylet. We hypothesised that laryngeal morbidity within the first 24 h after extubation would be lower with the Endoflex tube than with the conventional endotracheal tube with stylet because of less rigidity. METHODS: This randomised trial included 130 elective surgical patients scheduled for general anaesthesia with endotracheal intubation. Pre- and post-operative assessment of hoarseness, vocal fold pathology, and voice analysis using the Multidimensional Voice Program was performed. Induction of anaesthesia was standardised. After complete neuromuscular paralysis, intubation was done with an Endoflex tube or a conventional endotracheal tube with stylet. RESULTS: Post-operative hoarseness was found in 45% with the Endoflex tube and 55% with the endotracheal tube with stylet at 24 h after extubation (P = 0.44). Post-operative vocal fold injury was present in 23% in the Endoflex tube group and in 36% in the endotracheal tube with stylet group (P = 0.13). The increase in shimmer, the voice analysis variable reflecting vocal fold oedema, was 0.5% in the Endoflex tube group and 2.5% in the endotracheal tube with stylet group (P = 0.02). CONCLUSION: No significant difference was found in the incidence of hoarseness or vocal fold injury using the Endoflex tube. However, the statistically significant lower increase in the shimmer values in that group implies that the Endoflex may be associated with less laryngeal morbidity.

Acceleromyography of the orbicularis oculi muscle I: significance of the electrode position.

BACKGROUND: This study aimed to establish the best position of the stimulating electrodes for facial nerve stimulation during acceleromyographic monitoring from the orbital part of the orbicularis oculi muscle. METHODS: In 59 anaesthetised patients, an acceleration transducer was positioned over the middle of the eyebrow. In 47 patients, supramaximal train-of-four (TOF) stimulation was established for four electrode pairs with different positions along the facial nerve and behind the ear. The electrode pair with the lowest, the intermediate, and the highest supramaximal stimulating current based on first response (T1) in TOF was found in each patient. A possible response from direct muscle stimulation was evaluated during complete vecuronium block. In 12 patients, supramaximal stimulation was established using a stimulation sequence different from the one used in the first part of the study. RESULTS: The best positions for the stimulating electrodes were either with both electrodes just lateral to the eye, or with one electrode lateral to the eye and one in front of the ear. In most patients, supramaximal stimulation was obtained at these positions at 20-60 mA. However, in 10-21% of the patients, supramaximal stimulation could not be obtained. During complete block, 1-4 responses with a twitch height of 3-11% were recorded in 80% of the patients. CONCLUSION: The best placements of the stimulation electrodes are either just lateral to the eye or along the zygomatic arch. However, supramaximal stimulation may often not be obtainable, and activation of other facial muscles may be a confounding factor that may impede correct evaluation of the degree of neuromuscular block.

Acceleromyography of the orbicularis oculi muscle II: comparing the orbicularis oculi and adductor pollicis muscles.

BACKGROUND: The orbicularis oculi (OO) muscle has been recommended for neuromuscular monitoring when the adductor pollicis (AP) muscle is not available. We investigated whether neuromuscular block could be measured reliably from the orbital part of the OO muscle by the use of acceleromyography. METHODS: During propofol, fentanyl, and alfentanil anaesthesia two TOF-Guards (Organon Teknika NV, Boxtel, the Netherlands) with acceleration transducers placed on the distal phalanx of the thumb and over the middle of the eyebrow, respectively, were used to measure neuromuscular block simultaneously in 23 patients during vecuronium-induced and neostigmine-antagonized neuromuscular block. For both muscles, the simultaneously recorded first response (T1) in the train-of-four (TOF) and TOF-ratio were measured both during onset and recovery of the block. Furthermore, both the AP muscle T1 and TOF-ratio responses were plotted against 10% intervals of the OO muscle responses during onset and recovery, respectively. RESULTS: The orbicularis oculi muscle had a shorter latency and a faster recovery to TOF-ratio 0.80 compared with the AP muscle. During onset and recovery, pronounced variations of the AP muscle T1 and TOF-ratio responses were observed when compared with the OO muscle. CONCLUSION: A significant clinical disagreement exists between the degree of paralysis measured at the OO and the AP muscles. It is impossible to obtain a reasonable estimate of the degree of block at the AP muscle when the block is measured from the OO muscle with acceleromyography. If used, there is substantial risk of overlooking a residual block, and adequate recovery of the block should be confirmed by a final AP muscle measurement.