SECTION XV. Complications
A Adverse Cognitive Impairment
1. Introduction
Impairments in cognitive functioning from disturbances in the brain’s physiology can easily occur in the surgical patient. Neurologic impairment can be devastating in the postanesthesia patient in terms of quality of life and activities of daily living. Cognitive functioning is a broad construct that includes a number of categories: attention span, concentration, judgment, memory, orientation, perception, psychomotor ability, reaction time, and social adaptability. The prevalence of adverse neurologic impairment in surgical patients often results from organic brain disorders; the most common incidences are confusion, delirium, awareness, and, infrequently, coma.
2. Postoperative cognitive dysfunction
a) Postoperative cognitive dysfunction (POCD) is characterized by persistent deterioration of cognitive performance after anesthesia and surgery.
b) POCD is often associated with cardiac and orthopedic surgery, but it can also accompany other surgical procedures. Cognitive dysfunction in both cardiac and noncardiac surgery has largely focused on older adults, who might have a greater vulnerability to neurologic deterioration as a consequence of the aging process.
3. Confusion
a) The term confusion is used to describe the general affect and behaviors of patients; however, it is not specific and appears to have a great deal in common with delirium.
b) Confusion (a form of transient cognitive dysfunction) after anesthesia relates to disorders of orientation and is usually a relatively short-lived transient cognitive dysfunction.
c) Confusion after anesthesia is a normal occurrence, and it is suggested that patients refrain from engaging in activities requiring rapid responses for at least 48 hours postanesthesia.
4. Postoperative delirium
a) Delirium (or acute mental confusion) is transient, often abrupt and fluctuating, typically reversible, and related to increased risk of postoperative adverse reactions (i.e., pulmonary edema, myocardial infarction, respiratory failure, pneumonia, and death), increased length of hospital stay, increased health care cost, and poor functional and cognitive recovery.
b) Key symptoms include anxiety, incoherent or disorganized thinking and perceiving, reduced ability to sustain and shift attention to new external stimuli, and agitated behavior. There is sensory misperception; a disordered stream of thought; and difficulty in shifting, focusing, and sustaining attention to both external and internal stimuli. Irrelevant stimuli can easily distract the delirious individual.
c) Common are perceptual disturbances that result in misinterpretations, illusions, and hallucinations. Disturbances of sleep-wakefulness and psychomotor activity are present.
d) Precipitants are related to physical illness (e.g. cardiovascular disease), infection, hormone disorders, or nutritional deficiencies. Most frequent precipitants are metabolic disturbances; fluid and electrolyte imbalances; drug and alcohol toxicity; and unfamiliar and excessive sensory-environmental stimuli.
e) Delirium may be life-threatening and is a medical emergency. Delirium occurs in about 20% of elderly surgical patients and is more common in patients undergoing orthopedic procedures (i.e., femoral fractures) with an incidence rate of 28% to 60% in this surgical population. Thirty-two percent of patients that had coronary artery bypass surgery reported postoperative delirium.
f) Early identification and prompt treatment of the causes of delirium prevent irreversible dementia and death, with interventions targeted at reversing physiologic disturbances and preventing sensory deprivation.
5. Awareness
a) Awareness, the unambiguous recall of events during general anesthesia, reveals incidences of 0.18% in the United States. The term recall, the ensuing retention of an event after it occurs, is a better description of the phenomena; however, episodes of awareness are strong predictors of dissatisfaction with anesthesia care.
b) For every 1000 adult patients that receive a general anesthetic, as many as 1 or 2 will express the occurrence of awareness or recall; this figure is higher in children. Inadequate depths of anesthesia may lead to awareness and recall; accounts of awareness rely on patient recollection.
c) While patient recollection of awareness or recall may be reported, most do not complain of recalling pain during the procedure. Instead, patients report “dreamlike” experiences and auditory remembrance during which they are not in distress.
d) Reports of intraoperative awareness should be addressed immediately and thoroughly evaluated to obtain information for quality assurance.
e) Management of awareness begins when patients are given an opportunity to discuss the causes of the event with the anesthesia provider to gain a clearer understanding of the circumstances surrounding the experience and follow-up consultation.
f) The awareness experience is certainly a distressing event and outside normal operative occurrences. These stressful events may lead to nightmares and sleep disturbances, intrusive memories and avoidance behavior, emotional numbing and forgetting, and other diagnostic criteria for posttraumatic stress disorder (PTSD).
g) The causes of intraoperative awareness are diverse and are listed in the following box.
Situations Associated with Higher Incidence of Awareness Under Anesthesia
• Acute trauma with hypovolemia
• ASA Physical Status 3, 4, and 5
• Cardiac surgery, including off-pump
• Impaired cardiovascular status
• Caesarean section under general anesthesia
• Severe end-stage lung disease
• Bronchoscopy, laryngoscopy, or both
• History of awareness
• Expected intraoperative hypotension requiring treatment
• Chronic use of benzodiazepines or opioids requiring treatment, or both
• Anticipated difficult intubation
• Heavy alcohol intake
h) Awake paralysis, one of the most feared causes, is possibly the most preventable. Awake paralysis is related to lapses in practitioner vigilance and can lead to out-of-sequence neuromuscular blockade administration and medication error.
i) Prevention of awareness is the best treatment for awareness. The American Association of Nurse Anesthetists (AANA) has an awareness policy that helps identify at-risk patients and measures to address and possibly avoid perioperative awareness. This anesthesia care plan to reduce the incidence and severity of awareness includes the fundamental practices listed in the following box.
Anesthesia Care Plan to Reduce the Incidence and Severity of Awareness
1. During preanesthesia evaluation, assess the risk of awareness. Incorporate the possibility of awareness as part of the informed consent for all high-risk scenarios.
2. Check all anesthesia equipment (anesthesia machine, vaporizer, infusion pumps) to ensure the ability to deliver adequate amounts of anesthetic agents.
3. Consider the use of brain function monitoring, particularly for high-risk scenarios, if available.
4. Consider premedication with amnestic agents.
5. Clearly label all drug syringes immediately when they are drawn up. Do not rely on recognition of syringe size to confirm its contents. Consider other methods of ensuring the correct drug given to avoid inadvertent paralysis of the awake patient.
6. Provide additional doses of hypnotic, or initiate volatile agent administration for repeated intubation attempts.
7. Use an end-tidal agent monitor, with the low alarm set for a sufficient volatile concentration to prevent awareness.
8. When using total intravenous anesthesia, ensure a patent intravenous line and periodically check the function of the syringe pump.
9. Avoid excessive muscle paralysis unless required for surgical indications. Routinely use a peripheral nerve stimulator to measure degree of paralysis.
10. Conduct postoperative assessment to determine if unintended awareness occurred. If appropriate, refer the patient to a healthcare professional for support and therapy.
j) While awareness and recall of some of the anesthesia experience is impossible to prevent in all patients, vigilance on the part of the anesthesia provider (i.e., close attention to monitoring modalities and to anesthetic levels) should decrease the incidence substantially.
B Eye Injury
1. Corneal abrasion
a) Corneal injury is an infrequent occurrence during anesthesia. The cornea is a tough transparent dome-shaped surface covering the eyes that serves as a barrier to infection and trauma in this highly exposed organ.
b) Corneal abrasions are superficial defects of the corneal epithelium. Application of a short-acting topical anesthetic prior to assessment will facilitate an examination.
c) Visual acuity is usually normal unless the abrasion includes the visual axis or if there is considerable edema. There may be miosis caused by ciliary spasm and blepharospasm (marked by an uncontrollable, forcible closure of the eyelids) of the affected eye as a result of photophobia.
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