Airway rescue in acute upper airway obstruction using a ProSeal Laryngeal mask airway and an Aintree catheter: a review of the ProSeal Laryngeal mask airway in the management of the difficult airway.

We report the successful use of a ProSeal Laryngeal mask airway (PLMA) to rescue the airway when emergency tracheal intubation and ventilation of the lungs were impossible after haemorrhage into the neck following carotid endarterectomy, despite evacuation of the clot. The airway was re-established after placement of a PLMA. Fibreoptic examination of the airway revealed severe supraglottic swelling compromising airway patency. An Aintree catheter was placed in the trachea under fibreoptic guidance and a tracheal tube railroaded over this. The use of the PLMA in seven cases of difficult airway management and 11 cases of airway rescue is reviewed. Use of the PLMA was associated with high levels of success, often rescuing the airway when other techniques had failed. No complications of use of the PLMA were reported in these cases. The PLMA appears to be a useful device to assist in management of the difficult airway and for airway rescue. Potential advantages over the classic laryngeal mask airway include improved airway seal and reduced risk of aspiration. The gum elastic bougie-guided insertion technique is recommended when the PLMA is used for airway rescue.

Effect of propofol anaesthesia on the event-related potential mismatch negativity and the auditory-evoked potential N1.

BACKGROUND: Studies on the effects of anaesthesia on event-related potentials and long latency auditory-evoked potentials (AEP) are sparse. Both provide information on cortical processing and may have potential as monitors of awareness. We studied the effect of propofol on the event-related potential mismatch negativity (MMN) and the long-latency AEP NI. METHODS: Twenty-one patients received 1 microgram ml-1 stepped increases in the target concentration of propofol using Diprifusor until a maximum of 6 micrograms ml-1 was achieved or the patient had lost consciousness. Neurophysiological responses (MMN and N1) and the patients' level of consciousness were recorded before the administration of propofol and at a target effector site concentration of propofol of 1, 2, 3, 4, and 6 micrograms ml-1. Grand average evoked potentials were computed at baseline, before the administration of propofol (A); at the highest propofol concentration at which each patient was responsive (B); and at the concentration of propofol at which the patient became unconscious (C). RESULTS: Patients lost consciousness at different target concentrations of propofol, all being unresponsive by 4 micrograms ml-1. The response to the deviant stimuli used to elicit duration-shift MMN was significantly more negative than to the standard stimuli at A (mean difference 2.58 microV, P = 0.0011) but this difference was virtually abolished at point B, before the patients lost consciousness (mean difference 0.63 microV, P = ns). The amplitude of N1 evoked by standard stimuli was negative compared with electrical baseline at both point A (mean amplitude -3.81 microV, P < 0.001) and at point B (mean amplitude -2.2 microV, P = 0.002), but was no longer significantly different to baseline at point C (mean amplitude 0.51 microV, P = ns). The change in the mean amplitude of N1 from last awake (point B) to first unconscious (point C) was also significant (mean difference in amplitude 1.69 microV, P = 0.02). CONCLUSIONS: MMN is unlikely to be a clinically useful tool to detect awareness in surgical patients. In contrast, the loss of N1 may identify the transition from consciousness to unconsciousness and deserves further study.

The impact of percutaneous tracheostomy on intensive care unit practice and training.

We studied the impact of introducing percutaneous tracheostomy to our intensive care unit on the incidence and timing of tracheostomy and on the implications for surgical training. The proportion of patients receiving intensive care who underwent tracheostomy doubled from a median of 8.5% to 16.8% (p < 0.01) following the introduction of the percutaneous technique with the procedure being undertaken significantly earlier during the intensive care stay. The opportunity for surgical trainees to gain experience in open surgical tracheostomy has been virtually lost. The increase in tracheostomy rate may reflect a previous under-utilisation caused by the logistic problems of transferring a critically ill patient to theatre, or alternatively a relaxation of the indications for tracheostomy caused by a perceived benefit for the patient. An increased workload may also have contributed to the rise. Surgical trainees should be encouraged to learn percutaneous techniques and training opportunities in open surgical techniques should be maximised.