States of Awareness During General Anesthesia

STATES OF AWARENESS DURING GENERAL ANESTHESIA JACOBUS W. MOSTERT, M.D.* Surgical anesthesia is a continuum of change in perceptual reactance toward its goal offacilitating surgical operations. Ideally it aho provides freedomfrom pain and anguish. Since 1959 much concern has been aroused by reports of surgical patients being able to recall events occurring during general anesthesia. One major problem is that there are no characteristic physiological parameters to indicate that the patient is aware of what is going on. Contrary to traditional concepts, anesthesia seems to be a personal experience , and from time to time the anesthetist discovers to his dismay that he can play no legitimate part in its direct measurement. History Ever since Horace Wells failed to produce adequate anesthesia with nitrous oxide in 1844, patients have from time to time complained of being incompletely anesthetized [I]. By present-day standards all the anesthetics ofthe first decades following William T. G. Morton's successful use ofether at Massachusetts General Hospital during October 1846 were insufficient. Accounts of the time indicate that it was customary to inquire, immediately after commencement of surgery, whether the patient was feeling any pain. Conversation among surgeon, anesthetist, and patient was the rule just as it still is when local and regional nerve blocks are utilized. For certain heart operations an eminent American anesthesiologist has advocated retention of the patient's awareness of his surroundings [2], and some Europeans expect it, as is clear from the title of the Belgian journal L'anesthésie vigile et subvigile. But until 1942 the basic precepts of anesthesiology remained unchallenged, principally the concept oí effective drug concentrations as consistent biologic properties of all anesthetics [3, p. 318], having as its corollary the postulate that, at equipotent alveolar concentration of each anesthetic, the brain, at saturation, contains the same number of molecules per unit volume. Inhalation»Department of Anesthesiology, University of Chicago. 68 I Jacobus W. Mostert · Awareness during Anesthesia m i m¦ OJ "*» A, 'Il Amputation of the leg, from Johann von Gersdorff 's Feldtbuch der Wundartzney, 1517 anesthetics were thought of as totally inert substances taken up and excreted from the body only by the lungs and therefore subject to entirely comprehensive pharmacodynamic computations. What, No Curare? For several centuries it had been known that curare was a mixture of a number of poisonous plants the constant element ofwhich was known as Strychnos toxifera [4]. Sir Walter Raleigh already noted the paralyzing effects it had as arrow poison in 1595, but it was in 1942 in Montreal that the risk ofconsciousness during apparent general anesthesia was created by the introduction of curare [4]. Henceforth ideal surgical conditions could be established by the simple expedient ofan intravenous injection. Simultaneous employment of light levels of general anesthesia significantly attenuated toxicity, and depression of vital centers could be kept to a minimum. Patients soon became candidates for surgical procedures which they would not have survived with the older forms of anesthesia , and great advances in surgery took place as a direct result. There was a price to pay, and this became the subject of national public debate when Beecher and Todd [5, p. 60] published statistical evidence that curare resembled strychnine with respect to its inherent toxicity. They showed that following its introduction into anesthesia, utilization of curare seemed to be the direct cause of death in about one patient out of each 370. In other words, no matter how skillfully it was used, it was lethal especially in patients labeled as good risk, that is, good physical status, usually undergoing minor surgery. Today modern techniques have rendered the use of curare safer, but the possibility of awareness is probably inherent in its use, since every anesthetist encounters it from time to time. The first reference in the literature to awareness as a problem in medicine appeared in 1950 [6]. In it the author correctly describes his case as one of insufficient anesthesia , since only oxygen was used for an hour. The second case report only appeared nine years later [7] but was soon followed by hundreds from all over the world, as well as editorials which emphasized that we owe it to our patients to keep them unconscious...