It is our pleasure to respond to the letter regarding Augustine Guide Trademark (AG) intubation . Dr. Haridas makes several good points and raises additional questions for areas of further study.
He is correct in saying that we did not attempt to define a role for the AG in current practice. That was not the intent of our study, as detailed in our Methods section. Restated, our intent was to define the success rate in a controlled setting, namely, the operating room. We studied patients presenting for general anesthesia who needed oral endotracheal intubation after anesthesia induction and relaxation. Additionally, since this was a new device, we also recorded and reported the complication rate.
Dr. Haridas suggests that we should have directly compared the AG and laryngoscopy. However, we do not feel that this is warranted: they are fundamentally different techniques. Laryngoscopy involves direct visualization and manipulation of the head and neck; AG intubation is a blind technique where the neck is held neutral. Moreover, we in no way implied that AG intubation was faster than direct laryngoscopy, and, since we did not perform direct laryngoscopy on the 94 successful cases of AG intubation, we have no way of knowing whether all of those patients could have been intubated by direct laryngoscopy. So, even though direct laryngoscopy may be faster, assuming that intubation is more likely to be successful with a laryngoscope is not necessarily correct. Even so, a 94% success rate for a blind technique is very good; comparing the success rates of blind versus direct visualization techniques is probably unfair.
The 18% incidence of minor injuries (seven patients with small lacerations on the frenulum, or underside, of the tongue) should not be disturbing to most practitioners. These very minor injuries required no treatment or suturing. We included as injuries any swollen lip or minor bruising, and we made a special effort to rule out the presence of injuries during our postanesthetic visit. No recent literature addresses the incidence of injury during direct laryngoscopy for endotracheal intubation in anesthetized patients. Standard textbooks mention minor direct trauma to mucosa but do not provide an incidence. Donnelly et al.  described a 38% incidence of injuries, similar to those we saw as a result of direct laryngoscopy. Wylie  reported a 47% incidence of minor injury related to laryngoscopy, and Lewis and Swerdlow  noted a 63% incidence. These studies are somewhat dated, but they nonetheless accurately depicted the incidence of superficial trauma as direct laryngoscopy for endotracheal intubation was becoming widespread. With additional experience and expertise, we feel that the AG's rate of mucosal injury will decrease.
The difficult and failed cases were evenly distributed throughout our study; no learning curve distribution was seen.
Dr. Haridas's conclusions about the role of the AG in clinical practice are probably very true. The AG is very handy when neck mobility needs to be or is limited. Its use after direct laryngoscopy has failed needs to be further evaluated. In our limited experience , we have found the AG to be quite helpful; it may have a role in situations of difficult intubation, irrespective of oxygenation capability.
Dr. Haridas's point regarding the AG's "potential to be more traumatic to the upper airway than direct laryngoscopy" is merely an assumption and probably not correct. Again, he is comparing direct and blind techniques. It is true that a bigger piece of hardware is inserted into the oral cavity during AG intubation. However, if it is inserted carefully and gently and the AG is properly lubricated, the potential for injury should not be increased on this basis alone. To date, not one tooth has been damaged owing to AG intubation. The chances are minimal because the guide is inserted into the oral cavity perpendicular to the teeth, with no levering action against the teeth. The potential complications of blind techniques in general must be considered (e.g., creation of false passages) but can be minimized with a proper, gentle approach.
Dr. Haridas's point regarding close supervision of trainees and avoidance of excessive force is excellent. Of course, this is true of all airway management techniques and devices.
We thank Dr. Haridas for his interest in our article and for useful feedback after his own personal experiences with the AG. With further study, the role of the AG will be better defined. We continue to urge careful, correct use of this device by experienced, well trained practitioners. We also urge practitioners to avoid using the AG whenever a blind technique is contraindicated.
R. J. Carr, MD
K. G. Belani, MBBS, MS
Department of Anesthesiology, University of Minnesota, Minneapolis, MN 55455-0392
1. Carr RJ, Belani KG. Clinical assessment of the Augustine Guide Trademark for endotracheal intubation. Anesth Analg 1994;78:983-7.
2. Donnelly WA, Grossmann AA, Grem FA. Local sequelae of endotracheal anesthesia as observed by examination of 100 patients. Anesthesiology 1948;9:491-7.
3. Wylie WD. Hazards of intubation. Anaesthesia 1950;5:143-8.
4. Lewis RN, Swerdlow M. Hazards of endotracheal anaesthesia. Br J Anaesth 1964;36:504-15.
5. Carr RJ, Reyford H, Belani KG, et al. Evaluation of the Augustine Guide for difficult endotracheal intubation [abstract]. Anesthesiology 1994;81:A624.