POSTOPERATIVE TRACHEAL EXTUBATION

Although there is some information concerning the significance of postextubation respiratory problems, a better understanding of the scope of ventilation and oxygenation difficulties after general endotracheal anesthesia is needed. Clinicians have all experienced 'near misses' and have witnessed profound but usually short-lived hypoxemia when extubating patients. Postextubation difficulties resulting in hypoxic brain injury are a common cause of malpractice law suits. The etiologies of immediate and delayed airway obstruction were reviewed. A host of factors including the effects of residual anesthetics, pain or the lack of it, obligatory posthyperventilation hypoventilation, renarcotization, sleep, and respiratory acidosis can impair ventilation and oxygenation after tracheal extubation. While patients undergoing neck surgery usually experience no major airway difficulties postoperatively, a heightened awareness of the potential for serious respiratory morbidity in this patient population appears warranted. Further study and documentation of postextubation ventilatory problems in patients recuperating from neck surgery could further define the extent of such problems. The impact of anesthetics on breathing is well known. Gaps in our knowledge persist, however. More studies, such as those by Pavlin et al. (73) on airway function are needed. For example, there is very little clinical information with regard to the impact of anesthesia on hypoxic drive postoperatively and, in particular, whether this reflex indeed protects patients after extubation. The effects of weaning from ventilatory support and tracheal extubation in patients with intracranial pathology is also poorly described. The timing and impact of interventions in patients after neurosurgery, and possible therapies to modify undesirable effects deserves attention. Objective and simple clinical predictors of the return of adequate ventilatory functions are lacking. For example, how well does the presence of a sustained tetanic response to peripheral nerve stimulation at the ulnar nerve predict adequate airway function and ventilation after anesthesia? Further study is also required to define the importance of extubation techniques in a host of specific patient populations, such as those with bronchospastic disease or patients prone to laryngospasm such as children. What level of anesthesia is adequately 'deep' and what is the nature of the second or 'light' stage of anesthesia in modern day practice? Even in the healthy patient, immediate postextubation problems, such as laryngospasm, aspiration or bucking can be severe. Pulmonary edema following brief, but significant, airway obstruction is a clinical occurrence that should be preventable. Many more patients need to be studied in order to answer some of the most basic questions pertaining to tracheal extubation. Areas of research initiated by Mehta (176), Patel et al. (186), and Pounder et al. (187) merit further attention. Finally, extubation of the difficult airway represents an area where improved guidelines, approaches, and reported experiences can enhance training and hopefully improve outcome in this high-risk patient population.