A reply

Abstract

We thank Drs Palfreyman and Wakeling for their interest in our study. First of all we would like to point out that the design of the LITA tube is not our own, we were merely finding out if its supposed function, namely ‘laryngotracheal instillation of topical anaesthesia’, actually has a clinical role to play in neuro-anaesthesia. It would seem that they agree with our conclusion, namely that the tube is of doubtful efficacy in obtunding the response to extubation. They also make the sweeping statement that this tube breaks a fundamental principle of safe anaesthesia, and seem to be advocating laryngeal masks for neuro-anaesthesia. The use of topical local anaesthetic is commonplace in ENT and other surgery where obtunding the hypertensive response intubation or extubation is required or to prevent laryngospasm; the simple principle of keeping patients nil by mouth for a short period after surgery is all that is required, since the effect is very short lived. Many trials using similar techniques have been undertaken with no such sequelae [1, 2]. The statement that topical anaesthesia presents a risk to such patients is therefore unsubstantiated, indeed we found no evidence of aspiration in the LITA group which was stated clearly in our results. We acknowledge the fact that numerous other ways of obtunding the extubation response and preventing coughing exist; however, we would not advocate extubating neurosurgical patients deep unless absolutely necessary (e.g. an unclipped aneurysm), since it is vital that the neurosurgeons are able to assess their patients as early as possible following surgery. Most of the references in the letter regarding the use of laryngeal masks in neurosurgery relate to short neurosurgical procedures and we feel that in prolonged neurosurgery, where access to the airway is so severely restricted, the suggestion that laryngeal masks can be used is potentially dangerous. The suggested masking effect of β blockers on pulse and blood pressure changes is, we still feel, a real one and we draw Drs Palfreyman and Wakeling's attention once more to the fact that our peak heart rate at extubation is the same as that of Shajar et al.'s baseline value in non-β-blocked patients [3]. We acknowledge that our coughing score is unvalidated and perhaps a simple record of coughing being present or not would have been easier to undertake. However, as clinicians, we feel that mild coughing is still preferable to severe coughing so made some effort to record these differences. Propofol is acknowledged to have relaxing effects on the larynx at induction [4] and has been shown to cause less coughing even when compared to halothane [5]. When evaluating our study next to that of Diachun et al., who used 4% lidocaine [2], it is important to note that we did not exclude smokers (since we wanted to study a ‘real’ population) and yet 25% of our patients in the saline group had no coughing at extubation compared to only 7% in Diachun et al.'s study. With hindsight, however, we do regret not having used a more concentrated solution of lidocaine.