Continuous Monitoring of Cerebral Oxygen Saturation in Elderly Patients Undergoing Major Abdominal Surgery Minimizes Brain Exposure to Potential Hypoxia

Abstract

Elderly patients are more prone than younger patients to develop cerebral desaturation because of the reduced physiologic reserve that accompanies aging. To evaluate whether monitoring cerebral oxygen saturation (rSO(2)) minimizes intraoperative cerebral desaturation, we prospectively monitored rSO(2) in 122 elderly patients undergoing major abdominal surgery with general anesthesia. Patients were randomly allocated to an intervention group (the monitor was visible and rSO(2) was maintained at > or =75% of preinduction values; n = 56) or a control group (the monitor was blinded and anesthesia was managed routinely; n = 66). Cerebral desaturation (rSO(2) reduction <75% of baseline) was observed in 11 patients of the treatment group (20%) and 15 patients of the control group (23%) (P = 0.82). Mean (95% confidence intervals) values of mean rSO(2) were higher (66% [64%-68%]) and the area under the curve below 75% of baseline (AUCrSO2(2)< 75% of baseline) was lower (0.4 min% [0.1-0.8 min%]) in patients of the treatment group than in patients of the control group (61% [59%-63%] and 80 min% [2-144 min%], respectively; P = 0.002 and P = 0.017). When considering only patients developing intraoperative cerebral desaturation, a lower Mini Mental State Elimination (MMSE) score was observed at the seventh postoperative day in the control group (26 [25-30]) than in the treatment group (28 [26-30]) (P = 0.02), with a significant correlation between the AUCrSO(2) < 75% of baseline and postoperative decrease in MMSE score from preoperative values (r(2)= 0.25, P = 0.01). Patients of the control group with intraoperative cerebral desaturation also experienced a longer time to postanesthesia care unit (PACU) discharge (47 min [13-56 min]) and longer hospital stay (24 days [7-53] days) compared with patients of the treatment group (25 min [15-35 min] and 10 days [7-23 days], respectively; P = 0.01 and P = 0.007). Using rSO(2) monitoring to manage anesthesia in elderly patients undergoing major abdominal surgery reduces the potential exposure of the brain to hypoxia; this might be associated with decreased effects on cognitive function and shorter PACU and hospital stay.

Effect of age on brain oxygenation regulation during changes in position

“…Other studies show that patients with compromised baseline OHb are at higher risk to develop brain hypoxia during modest decrease in blood pressure associated with anesthesia (Paisansathan et al, in press). These results suggest that decreased baseline OHb may be related to postural or anesthesia related brain oxygen desaturation that occurs with aging, and this may produce neuronal dysfunction (Casati et al, 2005). Although age was not a significant indicator in the development of brain oxygen desaturation in this study, reduced brain hemoglobin reserve may be a risk factor.…”

“…blood pressure, there was no difference in the ability to regulate brain oxygenation in older subjects. Other studies conclude that regulation of brain oxygenation is significantly compromised when blood pressure is decreased during anesthesia in elderly patients or patients with low baseline OHb and HHb concentrations associated with cerebral pathology (Casati et al, 2005;Paisansathan et al, in press). Our data indicate that normal aging to 60 years does not alter brain oxygen regulation even though OHb and HHb are decreased.…”

“…Compromised brain hemodynamics due to aging or cerebral ischemia may inhibit brain oxygenation autoregulation during physiological and anesthetic challenges (Burton et al, 2004;Casati et al, 2005). In this setting, modest hypotension or hypocapnia can accentuate brain hypoxic changes (Enlund et al, 1989;Hampson et al, 1990;Torella and McCollum, 2004).…”

Extracranial contamination in the INVOS 5100C versus the FORE-SIGHT ELITE cerebral oximeter: a prospective observational crossover study in volunteers

“…As brain oxygen demand remains relatively stable under anesthesia, changes in SctO 2 typically represent reductions in cerebral oxygen supply, which are often due to reductions in blood pressure, carbon dioxide partial pressure, cardiac output, hemoglobin concentration, and/or arterial oxygen content. [5][6][7][8][9][10][11][12] The accuracy of SctO 2 measurements under a variety of clinical conditions is essential if appropriate assessment and management of brain oxygenation is to be possible. Nevertheless, previous studies suggest that extracranial contamination can influence the measurement of SctO 2 and result in measured values that do not entirely reflect the status of oxygenation in the brain.…”

Cerebral oxygen desaturation during one-lung ventilation: correlation with hemodynamic variables

“…1,2 Reduced perioperative cerebral saturation correlates with greater morbidity and mortality in patients undergoing open heart surgery 3 and major abdominal procedures 4 and also in patients following thoracic surgery. 5 Low cerebral saturation correlates with postoperative delirium and postoperative cognitive deficit.…”