Comment on the Need to Fill a Gap in the Assessment of Neurological Status Before Elective Surgery.

Abstract

In the recent April issue of Annals of Surgery, Alam and Ma1 contend that brain health is overlooked by current modalities of perioperative assessment, and we fully agree with their perspective. On the other hand, protocols and guidelines focusing on modifiable risk factors for cardiac, pulmonary, renal, and metabolic-related complications have clearly shown that prehabilitation strategies combined with enhanced recovery pathways decrease complication rates, 30-day mortality, and length of hospital stay.2 Frailty, rather than chronological age, is increasingly recognized as a predictor of adverse postoperative events. Interestingly, a large cohort study conducted across 9 noncardiac specialties showed a >10% 180-day mortality for frail patients following even low-stress procedures in low-intensity specialties.3 Frailty in the elderly population is strongly associated with the risk of delirium, institutionalization, and mortality. Surgical stress and systemic inflammation lead to neuroinflammation, worsen preoperative neurologic status, and increase neurological complication rates in vulnerable individuals who lack physiological reserve and often present with multisystemic functional deterioration. Delirium is a form of acute brain injury occurring in up to 80% of mechanically ventilated patients and 50% of nonventilated patients. It remains the most common postoperative adverse event, with a pooled risk ratio of 2.13 (95% confidence interval 1.23–3.67),4 but it can also be a marker of preclinical dementia and may contribute to delayed neurocognitive recovery, functional decline, and institutionalization. Since drugs are the most common reversible cause of postoperative delirium, use of electroencephalography monitoring as a guide to anesthetic titration to reduce the rate of perioperative cognitive disorders may prove a useful adjunct in this category of patients, but it is still under investigation.5 In addition, oxidative injury to the brain may occur during general anesthesia, indicating that supraphysiological oxygen administration can be a "double-edged sword."6 In our opinion, priority should be given to recognition of overt or subclinical neurological disorders before the patient undergoes general anesthesia and surgery. Evaluation of the preoperative neurocognitive function is a critical and often neglected component of the preoperative assessment of elderly and frail patients. For example, in patients with impairment of the blood–brain barrier secondary to stroke or of vascular leukoencephalopathy, cephalosporins, and macrolids may cause delirium by binding competitively to the GABA-A receptors and lowering the seizure threshold. Thiamin deficiency may go unrecognized in individuals with dehydratation and nutritional impairment, and represents a risk factor for the development of Wernicke encephalopathy after glucose infusion in the postoperative period. Normal pressure hydrocephalus is often misdiagnosed but has emerged as a treatable movement disorder and represents a cause of delirium or cognitive decline in elderly adults who undergo cardiac surgery.7 Elderly patients should be counseled and monitored regarding pharmacological therapy in preparation for elective surgical procedures since several drugs may have a significant impact on neurocognitive outcomes. Multiple prescriptions and nonprescription medications, including complementary/herbal products, have the potential for drug-to-drug interaction and perioperative adverse events. Although electronic health records have the potential to detect errors and interactions, a very important step at the time of office visit is having patients to bring in all medications they use at home to prevent adverse outcomes due to improper drug dosage, withdrawal, or interactions. Benzodiazepins, analgesic, anticholinergic, antidopaminergic, and serotoninergic drugs are mainly involved in the pathogenesis of postoperative delirium. Adjusting the dosage schedule of all necessary medications is critical. For example, tapering levodopa may cause akinetic attacks with hyperpyrexia and diaphoresis resembling the clinical picture of neuroleptic malignant syndrome.8 Alternative drug formulations or routes for neurotropic drug administration should be considered especially after foregut surgical procedures that may transiently impair swallowing or bowel absorption. Perioperative assessment remains the foundation for a safe surgical practice. The proactive care of older patients undergoing surgery model has integrated the comprehensive geriatric assessment providing a robust evidence-based methodology to identify the elderly population at risk and to optimize the recovery pathway and follow-up after hospital discharge.9 A randomized clinical trial showed that preoperative comprehensive geriatric assessment and optimization according to the proactive care of older patients undergoing surgery model result in fewer nonsurgical complications and reduce the length of hospital stay by 40% compared to standard care.10 Indeed, the adoption of a multidisciplinary neurological, geriatric, anesthesiological, and surgical care pathway could fill the existing gap in perioperative care. Obese patients with obstructive sleep apnea syndrome need special attention because of the higher risk of prolonged mechanical ventilation and associated neurocognitive impairment. Titration of anesthetic drugs, use of minimally invasive surgical techniques, and optimal pre-emptive, and postoperative pain control by means of multimodal opioid-sparing analgesia and regional/neuraxial techniques may further reduce the incidence, duration, and sequelae of delirium.11 In some circumstances, electroencephalography may prove useful to differentiate delirium from recurrent paroxysmal electrical dysfunction causing seizure disorders. Despite lack of high-quality data, antiepileptic drugs have received considerable attention for treatment of agitation and aggression in the postoperative setting. Recent studies also suggest that dexmedetomidine, an alpha-2-receptor agonist used for sedation in mechanically ventilated adults, may reduce time to extubation and appears to be associated with less neurocognitive dysfunction at least 1 week after cardiac surgery compared to placebo or alternate sedation.12 Last but not least, patients discharged from intensive care units to the general ward have better neurological outcomes and less subclinical delirium using the “ABCDE bundle” (awakening and breathing coordination, delirium monitoring and exercise/early mobility”). Moving patients “from bed to wheelchair” may decrease the duration of delirium and the length of mechanical ventilation.13 In conclusion, proper triage and optimization of perioperative care are achievable goals that can reduce the risk and the duration of postoperative cognitive disorders. It is likely that screening and appropriate interventions for anxiety, depression, and other reversible neurological conditions can strengthen patients’ ability to withstand surgical stress and help reducing the short- and long-term consequences of delirium.