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Correspondence  |   June 2008
Regarding Fiberoptic Intubation and Laryngeal Morbidity
Author Notes
  • University of Texas Health Science Center, Houston, Texas.
Article Information
Correspondence
Correspondence   |   June 2008
Regarding Fiberoptic Intubation and Laryngeal Morbidity
Anesthesiology 6 2008, Vol.108, 1150-1151. doi:10.1097/ALN.0b013e318173eb67
Anesthesiology 6 2008, Vol.108, 1150-1151. doi:10.1097/ALN.0b013e318173eb67
To the Editor:—
I read with interest the article “Fiberoptic Intubation and Laryngeal Morbidity” by Heidegger et al.  1 The authors’ purpose was to demonstrate that the frequency of vocal cord sequelae (VCS) after fiberoptic tracheal intubation without neuromuscular blockade (NMB) was less than 25% when compared to VCS with NMB. I believe their study fell short of the model for evidence-based medicine.
The study group and the control group were managed so differently that comparison of the frequency of VCS in either group cannot be reasonably compared. Along with objective assessment of the patients, the patients were asked to subjectively assess hoarseness and discomfort with introduction of potential bias. Using subjective assessment tools dependent on the patient’s own feelings, one must consider and attempt to eliminate distracting factors that could significantly impact the objectivity of the assessment.
To truly control for fiberoptic technique and NMB, the two groups could have easily been standardized by the following:
  1. Using transtracheal local anesthetics in both the study and control patients.

  2. Using identical induction agents. Anesthetic induction in the two groups was achieved with different agents, the study group receiving etomidate and the control group receiving propofol. Side effect profiles of these two agents clearly differ and could result in distraction of symptoms, especially in the study group.

  3. Selection of identical endotracheal tubes (ETTs). The authors used a smaller ETT for the study group (6.0 mm ID) and a larger ETT for the control group (7.0 mm ID for females and 8.0 mm ID for males). The control group received a polyvinyl chloride ETT, and the study group received a silicone ETT. Using an identical tube such as a 6.0-mm-ID silicone tube in both groups would seem like a logical choice. In addition, both the study and control groups could have been intubated nasally to establish a more reliable control.

Another concern is the selection of patients undergoing surgery to eye, ear, and salivary glands, which could affect subjective discomfort associated with VCS.
Finally, the assessment of the vocal cords was performed by an ear, nose, and throat surgeon blinded to patient group assignment. It is difficult to believe that an experienced ear, nose, and throat surgeon could not recognize that a patient underwent recent nasal intubation. Even with the best of conditions, minor traumatic injury is often noted along the path of a nasotracheal intubation.
The authors did design the study to compare with the trial of Mencke et al.  ,2 which used a silicone ETT for fiberoptic cases and polyvinyl chloride for direct laryngoscopy cases, and acknowledge that future study is needed to assess silicone tubes and VCS in oral direct laryngoscopy ETT placement. With respect to anesthetic agents and ETT assignment, the authors state that the goal was to compare two established techniques and not to solely compare NMB versus  no NMB. However, this is in contrast to the stated goal of the study and even to the title of the article itself.
University of Texas Health Science Center, Houston, Texas.
References
Heidegger T, Starzyk L, Villiger CR, Schumacher S, Studer R, Peter B, Nuebling M, Gerig HJ, Schnider TW: Fiberoptic intubation and laryngeal morbidity: A randomized controlled trial. Anesthesiology 2007; 107:585–90Heidegger, T Starzyk, L Villiger, CR Schumacher, S Studer, R Peter, B Nuebling, M Gerig, HJ Schnider, TW
Mencke T, Echternach M, Klienschmidt S, Lux P, Barth V, Plinkert PK, Fuch-Buder T: Laryngeal morbidity and quality of tracheal intubation: A randomized controlled trial. Anesthesiology 2003; 98:1049–56Mencke, T Echternach, M Klienschmidt, S Lux, P Barth, V Plinkert, PK Fuch-Buder, T