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ABSTRACT & COMMENTARY
Synopsis: Investigators report a high success rate with the laryngeal mask airway in patients who fail standard endotracheal intubation.
Source: Martin SE, et al. Use of the laryngeal mask in air transport when intubation fails. J Trauma Inj Infect Crit Care 1999;47:352-357.
In a study by martin and colleagues at the Memorial Health University Medical Center in Savannah, Georgia, patients who could not be intubated by the flight team during aeromedical transport were instrumented with the laryngeal mask airway (LMA). Over a 22-month period, conventional endotracheal intubation failed in 25 patients, with 17 of the 25 meeting study inclusion criteria. Causes of airway instability included motor vehicle crash (14), fall (1), pedestrian struck (1), and stroke (1).
The LMA was correctly inserted with one attempt in 16 of 17 patients. In the remaining patient, insertion of the LMA was not successful after two attempts. In the 16 patients who were successfully instrumented with the LMA, correct placement was obtained in less than 10 seconds. Oxygenation and ventilation were measured with a continuous O2 saturation monitor and end-tidal CO2 (ETCO2) monitor while in the helicopter and by arterial blood gas on arrival in the ED. All patients achieved O2 saturation of 97-100% and ETCO2 of 24-35 mmHg. On arrival, all patients were satisfactorily oxygenated (pO2 range, 65-628) and all but one patient were successfully ventilated (pCO2 range, 29-52). In summary, the investigators report a high success rate with the LMA in patients who fail standard endotracheal intubation. They recommend it as an important tool for airway management in the prehospital setting.
Comment by Jeffrey W. Runge, MD, FACEP
Currently, there is no worthy substitute for properly performed endotracheal intubation in patients who require control and management of an unstable airway. Outside of the setting of cardiac arrest, this procedure should be carried out using rapid sequence techniques that facilitate intubation and provide neuroprotection. Unfortunately, the majority of EMS professionals in this country work in locales where it is difficult to maintain skills in this vital and relatively complicated technique. It is extremely important that EMS medical directors provide their prehospital crews with a variety of "tricks in their bags" to take care of those who require airway management.
The LMA has been successfully used by anesthesiologists in the operating room for years. It is popular with many pediatric anesthesiologists for short cases that would have otherwise required brief mask anesthesia. Any questions about adequacy of ventilation and oxygenation have long been answered, but the possibility of aspiration of gastric contents with the LMA is still under discussion. There are proponents and detractors who express very strong opinions about chances of gastric aspiration with the LMA vs. bag valve masks, but data are lacking. Much of the information on the device comes from the anesthesia literature, which is quite different than the prehospital setting where patients often have full stomachs.
With the understanding that any procedure or instrument has complications, good judgment must prevail when seeking to protect a patient’s airway, ensuring tissue perfusion with oxygenated blood and ventilation to alleviate the sequelae of hypercapnia. Recognizing that the bag valve mask is no simple procedure, especially if not used frequently, the LMA certainly should be considered as an alternative step to endotracheal intubation for patients who cannot be intubated following neuromuscular blockade. It should also be considered for those EMS services where intubation cannot be taught or where skills cannot be maintained. The goal of EMS is to deliver the patient to the hospital in the best shape possible. Clearly, the LMA has distinct advantages over the bag valve mask in selected patients, and should be available when endotracheal intubation is not possible in patients who require airway management. (Dr. Runge is Assistant Chairman and Clinical Research Director, Department of Emergency Medicine, Carolinas Medical Center, Charlotte, NC.)
a. risk of hypoxia.
b. risk of gastric content aspiration.
c. risk of hypercapnia.
d. risk of esophageal placement.