Abstract SNACC-21

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Cerebral autoregulation in adults undergoing sevoflurane anesthesia: a prospective cohort study of two age groups

1Goettel N, 2Patet C, 3Czosnyka M, 1Strebel S, 1Steiner L
1University Hospital Basel, Basel, BS, Switzerland; 2Lausanne University Hospital, Lausanne, VD, Switzerland; 3University of Cambridge, Cambridge, , United kingdom

BACKGROUND: Autoregulation of blood flow is a key feature of the human cerebral vasculature to assure adequate oxygenation and metabolism of the brain under changing physiological conditions. Impaired cerebral blood flow (CBF) autoregulation is associated with various pathological and pharmacological states, and may be a trigger for poor neurological outcome such as silent ischemia and/or postoperative cognitive decline, which is more common in elderly patients. Little is known about the effect of inhalational anesthetic agents and advanced age on CBF autoregulation.
METHODS: We conducted a prospective observational multicenter study to determine the effect of sevoflurane anesthesia on individual CBF autoregulation in two age groups. All patients underwent standardized sevoflurane anesthesia for a major surgical intervention. Recorded by transcranial Doppler ultrasonography, cerebral hemodynamic data were computed to provide an individual CBF autoregulation curve for each patient. CBF autoregulation indices, thresholds, and ranges were compared in young and elderly patient groups.
RESULTS: One hundred thirty-three patients (49 patients (37%) aged 18-40 years and 84 patients (63%) aged ≥65 years) were included in the study. Intraoperative minimum alveolar concentrations of sevoflurane were 0.94 ± 0.09 in young and 0.81 ± 0.12 in older subjects. Overall, the index of CBF autoregulation was significantly higher in older patients (0.5 vs 0.41, P = 0.011), indicating a decreased autoregulatory capacity in the elderly. Effective cerebral autoregulation was found only in a very narrow blood pressure range of 13.8 ± 9.8 mm Hg in younger and 10.2 ± 8.6 mm Hg in older patients. The lower threshold of autoregulation was 66 ± 12 mm Hg and 73 ± 14 mm Hg in younger and older patients, respectively.
CONCLUSION: Our data shows that the autoregulatory plateau is significantly shortened in both younger and older patients under sevoflurane anesthesia with approximately 1 MAC. It remains unclear whether this reduction of the human brain’s capacity to autoregulate CBF has an impact on the vulnerability for intraoperative cerebral ischemic events.

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