A Processed Electroencephalogram-Based Brain Anesthetic Resistance Index Is Associated With Postoperative Delirium in Older Adults: A Dual Center Study.

BACKGROUND: Some older adults show exaggerated responses to drugs that act on the brain. The brain's response to anesthetic drugs is often measured clinically by processed electroencephalogram (EEG) indices. Thus, we developed a processed EEG-based measure of the brain's resistance to volatile anesthetics and hypothesized that low scores on it would be associated with postoperative delirium risk. METHODS: We defined the Duke Anesthesia Resistance Scale (DARS) as the average bispectral index (BIS) divided by the quantity (2.5 minus the average age-adjusted end-tidal minimum alveolar concentration [aaMAC] inhaled anesthetic fraction). The relationship between DARS and postoperative delirium was analyzed in 139 older surgical patients (age ≥65) from Duke University Medical Center (n = 69) and Mt Sinai Medical Center (n = 70). Delirium was assessed by geriatrician interview at Duke, and by research staff utilizing the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) instrument at Mt Sinai. We examined the relationship between DARS and delirium and used the Youden index to identify an optimal low DARS threshold (for delirium risk), and its associated 95% bootstrap confidence bounds. We used multivariable logistic regression to examine the relationship between low DARS and delirium risk. RESULTS: The relationship between DARS and delirium risk was nonlinear, with higher delirium risk at low DARS scores. A DARS threshold of 28.755 maximized the Youden index for the association between low DARS and delirium, with bootstrap 95% confidence bounds of 26.18 and 29.80. A low DARS (<28.755) was associated with increased delirium risk in multivariable models adjusting for site (odds ratio [OR] [95% confidence interval {CI}] = 4.30 [1.89-10.01]; P = .001), or site-plus-patient risk factors (OR [95% CI] = 3.79 [1.63-9.10]; P = .003). These associations with postoperative delirium risk remained significant when using the 95% bootstrap confidence bounds for the low DARS threshold (P < .05 for all). Further, a low DARS (<28.755) was associated with delirium risk after accounting for opioid, midazolam, propofol, phenylephrine, and ketamine dosage as well as site (OR [95% CI] = 4.21 [1.80-10.16]; P = .002). This association between low DARS and postoperative delirium risk after controlling for these other medications remained significant (P < .05) when using either the lower or the upper 95% bootstrap confidence bounds for the low DARS threshold. CONCLUSIONS: These results demonstrate that an intraoperative processed EEG-based measure of lower brain anesthetic resistance (ie, low DARS) is independently associated with increased postoperative delirium risk in older surgical patients.

Complex abdominal wall hernias: a new classification system and approach to management based on review of 133 consecutive patients.

BACKGROUND: Plastic surgeons are increasingly involved in the repair of complex ventral hernias. Although this typically involves recurrent incisional hernias, operative strategies can be applied to most abdominal wall defects, including chronic wounds with or without exposed mesh, enterocutaneous fistulas, or hernias associated with significant pannus formation. METHODS: This is a retrospective review of a single institution/single surgeon experience of complex ventral hernia repair performed over a 5-year period. Patients were classified into different hernia types based on their characteristics and underwent hernia repair according to the presented algorithm. RESULTS: A total of 133 patients underwent a complex ventral hernia repair between January 2005 and September 2009. The separation of components technique was used in the majority of cases. Permanent or biologic mesh was added in select patients. Adjunctive procedures were performed as indicated. The majority of short-term (less than 1 year) recurrences occurred in patients expected to have impaired wound healing due to comorbid conditions. In these patients, the recurrence rate was reduced when autologous repair was reinforced with mesh. CONCLUSION: Autologous tissue is the preferred method for reconstruction of complex ventral hernias. In certain instances, such as contamination, use of an acellular dermal matrix mesh is added as a temporizing measure. A subset of patients who will be prone to recurrence remains. Long-term follow-up is needed to confirm reliable and reproducible results.