Intraoperative and Anesthesia Awareness

Excerpt

"The knife is searching for disease, the pulleys are dragging back dislocated limbs, nature herself is working out the primal curse which doomed the tenderest of her creatures to the sharpest of her trials, but the fierce extremity of suffering has been steeped in the waters of forgetfulness, and the deepest furrow in the knotted brow of agony has been smoothed forever."

Dr. Oliver Wendell Holmes, Sr., uttered those words almost 200 years ago, in November of 1846, commenting in a lecture to students at Massachusetts Medical College on the first public demonstration of ether just a month before. The historical event has since become known as "Ether Day." Indeed, when Dr William Morton, a dentist, successfully anesthetized Mr. Gilbert Abbot with ether to resect a tuberculous submandibular lesion in the amphitheater of Massachusetts General Hospital, many shared this belief. Corresponding with Dr. Morton shortly after that, Dr. Holmes is believed to have coined the term "anesthesia," stating:

"Everybody wants to have a hand in a great discovery. All I will do is give a hint or two as to names—or the name—to be applied to the state produced and the agent. The state should, I think, be called "Anaesthesia." This signifies insensibility—more particularly...to objects of touch."

The medical community assumed then that humanity's unavoidable suffering through surgical intervention—the "primal curse" of humankind—was relegated to the dustbin of medical history. And yet, in the third decade of the 21st century, intraoperative awareness continues to threaten patients with horror and agony on the operating table, even as expectations for painless surgery have become commonplace and as practitioners of anesthesia continue to minimize both its frequency and relevance.

This review addresses incidence, risk factors, anesthetic depth monitoring, prevention strategies, and perioperative, team-based management of unintended intraoperative awareness. The topic concludes with a brief review of the long-term effects of accidental awareness during general anesthesia (AAGA) on patients and practitioners.

Intraoperative awareness is characterized by the coincidence of intraoperative consciousness and explicit, episodic postoperative recall of events during a planned anesthetic. Patient experiences may range from isolated auditory recall to the catastrophic experience of painful surgical stimulation combined with the sensation of suffocation and paralysis in the setting of neuromuscular blockade (NMB). While the broader phenomenon of intraoperative awareness may occur in any setting where a patient expects a depressed level of consciousness, including in regional anesthesia, procedural, or intravenous (IV) sedation, most attention—both from patients and practitioners- is focused on AAGA. Estimates of the incidence of AAGA range from 1:1000 to 1:20,000, with a wide range of variation dependent upon variables in anesthetic technique, patient population, and surgical context/procedure. Notably, published incidence rates are highly dependent on the investigational approach, with rates derived from directed postoperative questioning far exceeding those in studies of self-reported awareness.