Limiting Emergence Phenomena After General Anesthesia With Combined LMA and ETT Airway Management Technique

Overview

Emergence from general anesthesia with a laryngeal mask airway compared with an endotracheal tube has been shown to favorable with respect to limiting emergence phenomena such as coughing, straining, restlessness, and sympathetic stimulation leading to hypertension and tachycardia. Many anesthesiologists would prefer the use of an ETT to an LMA in cases in which higher ventilation pressures may be required, in those patients who are perceived to be high risk for reflux and pulmonary aspiration of gastric contents, as well as during cases that allow the anesthesiologist to have little accessibility the airway. The aim of this study is to investigate an airway management technique that would allow for the benefits of the ETT in terms of a secure airway for the duration of the surgical procedure as well the potential for less emergence phenomena seen when emerging with an LMA.

Emergence from general anesthesia is a critical period of anesthetic management (1. Popat, 2012). The noxious stimuli of an endotracheal tube as well as the excitement stage of anesthesia, commonly seen prior to return of consciousness while emerging from general anesthesia, both lead to emergence phenomena of coughing, straining, and restlessness in addition to physiologic derangements (2. Atkinson, 1987). Physiologically, emergence from anesthesia is associated with rising sympathetic tone (as evidenced by elevated catecholamine levels and the resultant hemodynamic changes of increasing heart rate and blood pressure), intracranial pressure, and intraocular pressure. Airway tone and reflexes are also problematic as they may be depressed by the lingering pharmacologic effects of anesthetics and analgesics leading to decreased airway obstruction or aspiration events. Airway reflexes may also be exaggerated while traversing the excitement stage; this can lead to undesirable consequences of coughing, breath-holding, bucking or in extreme cases laryngospasm. A smooth emergence is preferable for all patients but is required for those patients who would not tolerate the above physiologic changes (e.g. severe aortic stenosis or coronary artery disease, both of which would poorly tolerate tachycardia) or those would be at risk in terms of the procedure that was performed (cerebral aneurysm clipping, carotid endarterectomy, thyroidectomy: procedures in which stress fresh surgical wounds with hypertension and straining would be undesirable). Several airway management (3. Koga 1998, 4. Perello-Cerda 2015) and pharmacologic strategies (5. Minogue 20014, 6. Nho 2009, 7. Guler 2005) have been employed to provide a smooth emergence from general anesthesia. One of the most efficacious strategies is the use of supraglottic airway devices rather than endotracheal tubes. Despite evidence supporting the safety and efficacy of ventilation of SGAs during laparoscopic procedures (8. Natalini 2003, 9. Belena 2012, 10. Carron 2012, 11. Bernardini 2009), many anesthesiologists would prefer the use of an ETT to an SGA in cases in which higher ventilation pressures may be required (obesity, steep Trendeleberg position, pneumoperitoneum). In addition to the cases requiring high ventilation pressures, ETTs are preferred to SGAs in those patients who are perceived to be high risk for reflux and pulmonary aspiration of gastric contents (non-fasted, intestinal obstruction, gastroparesis, parturients), as well as during cases that allow the anesthesiologist to have little accessibility the airway (neurosurgical, ENT, etc). The Bailey maneuver (managing the airway with an ETT throughout the case and then exchanging for an LMA while deeply anesthetized (12. Nair 1995), has also been shown to provide less stimulating emergence. Unfortunately, the Bailey maneuver is relatively contraindicated in cases in which there is the perception that reintubation would be difficult, as the risks of exchanging a functioning airway device for one that has not been tested outweighs the potential benefits of a smooth emergence. The airway management technique under investigation involves initially placing an LMA after induction of anesthesia. Once adequate ventilation has been accomplished using the LMA, the patient will be endotracheally intubated using a fiberoptic bronchoscope and the in situ LMA as a conduit (13. Timmermann 2011). General anesthesia will be maintained with sevoflurane and narcotics at the discretion of the primary anesthesiologist. The patient will be ventilated via the endotracheal tube during the duration of the surgical procedure and then the trachea will be extubated while the patient is at a deep plane of anesthesia after release of the pneumoperitoneum and return to supine positioning. This technique is a potential method for reducing the stress of emergence in patients who would benefit from the use of an endotracheal tube intraoperatively.