Is routine endotracheal intubation as safe as we think or wish?

EVERY year, millions (tens of millions?) of patients undergo laryngoscopy and tracheal intubation as part of their routine anesthetic care. Although this method was only rarely used in our practice before the 1960s, it is now almost as routine as placing a peripheral intravenous catheter. A great deal of attention is devoted to airway management in general (particularly the patient with a difficult airway), but we rarely give much thought to the consequence of intubation in patients with complete, normal (easy) airways. In this issue of ANESTHESIOLOGY, Tanaka et al. describe measurable changes in the larynx following routine endotracheal intubations. The changes consisted of increased airflow resistance that was attributed to intraoperative swelling of the laryngeal soft tissues in patients who were intubated. Such postoperative laryngeal changes were absent in the patients who received a laryngeal mask airway for anesthesia. It is tempting to dismiss the findings of this study as intuitively predictable or trivial. However, we believe that the findings represent the less severe end of the spectrum of airway injuries caused by tracheal intubation. The findings of Tanaka et al. confirm our long-held belief that even routine tracheal intubation produces changes in the airway. These changes may vary from those that are very mild (detectable only with elaborate methods, such as in Tanaka’s study) to the very serious. For example, Domino et al. analyzed the claims of airway injuries in the American Society of Anesthesiologists closed claims project. Of the 266 claims related to airway injury, 87 involved the larynx, with the most common lesions being vocal cord paralysis, granulomas, arytenoid dislocation, and hematomas. However, “80% of laryngeal injuries were associated with routine (nondifficult) tracheal intubation. . .,” and only 17 of these cases were associated with a difficult intubation. Airway injuries placed fourth (6%) behind three other major types of injuries: death (32%), spinal cord or peripheral nerve damage (16%), and brain damage (12%). Others have observed serious laryngeal injuries (e.g., vocal cord paralysis, arytenoid cartilage subluxation, laryngeal granulomas, and scars) following short-term intubation and anesthesia. Paulsen et al. compiled a list of several reports of arytenoid cartilage subluxation. In most of these reports, intubation was performed without apparent difficulty and the patients were intubated for a short period of time. These findings suggest that laryngeal damage was related to intubation and not to duration of surgery. Although there are some differences in opinion with regard to general risk factors, several factors were suggested for arytenoids subluxation, including laryngomalacia, renal insufficiency, acromegaly, chronic glucocorticoid intake, and rheumatoid arthritis. An important clinical sign of potential postoperative laryngeal injury is voice dysfunction, namely, hoarseness. The most common cause for postoperative hoarseness in patients undergoing procedures that do not involve the head and neck is swelling of the vocal cords. Recent evidence by Mencke et al. suggests that the quality of intubation contributes to laryngeal morbidity. Specifically, intubating conditions that are associated with various degrees of coughing, resistance to laryngoscope blade insertion (difficult laryngoscopy because of the patient being light/inadequately paralyzed), and limb movement are associated with a greater incidence of postoperative hoarseness and laryngeal injuries. Most of the laryngeal trauma occurred in patients who received no neuromuscular blockers to facilitate routine endotracheal intubations. Mencke et al. concluded that the use of neuromuscular blockers in the sequence of induction drugs is associated with better intubating conditions and less postoperative hoarseness and laryngeal injury. It seems that under suboptimal intubating conditions, even the mildest body movement may lead to mechanical trauma caused by the laryngoscope or endotracheal tube, resulting in laryngeal or tracheal injury. We find it very interesting that that by taking a simple measure, such as adding neuromuscular blockers at induction, the incidence of postoperative hoarseness dramatically dropped. Although Menke’s study focused on the role of intubating conditions in postoperative laryngeal morbidity, the incidence of hoarseness or laryngeal dysfunction following routine tracheal intubation is not clear. Previous research by Jones et al. found that 54 of 167 studied patients had hoarseness following short-term intubation. In five of these patients, hoarseness lasted for periods ranging between 9 and 99 days. Kark et al. reported hoarseness that lasted for more than 6 months in 3% of women undergoing mastectomies. The figures presented by Domino, Mencke, Jones, and Kark are This Editorial View accompanies the following article: Tanaka A, Isono S, Ishikawa T, Sato J, Nishino T: Laryngeal resistance before and after minor surgery: Endotracheal tube versus laryngeal mask airway. ANESTHESIOLOGY 2003; 99:252–8.