title: Near-infrared spectroscopy assessed cerebral oxygenation during open abdominal aortic aneurysm repair: relation to end-tidal CO2 tension.
abstract: During open abdominal aortic aneurism (AAA) repair cerebral blood flow is challenged. Clamping of the aorta may lead to unintended hyperventilation as metabolism is reduced by perfusion of a smaller part of the body and reperfusion of the aorta releases vasodilatory substances including CO2. We intend to adjust ventilation according end-tidal CO2 tension (EtCO2) and here evaluated to what extent that strategy maintains frontal lobe oxygenation (ScO2) as determined by near infrared spectroscopy. For 44 patients [5 women, aged 70 (48-83) years] ScO2, mean arterial pressure (MAP), EtCO2, and ventilation were obtained retrospectively from the anesthetic charts. By clamping the aorta, ScO2 and EtCO2 were kept stable by reducing ventilation (median, -0.8 l min(-1); interquartile range, -1.1 to -0.4; P < 0.001). During reperfusion of the aorta a reduction in MAP by 8 mmHg (-15 to -1; P < 0.001) did not prevent an increase in ScO2 by 2 % (-1 to 4; P < 0.001) as EtCO2 increased 0.5 kPa (0.1-1.0; P < 0.001) despite an increase in ventilation by 1.8 l min(-1) (0.9-2.7; P < 0.001). Changes in ScO2 related to those in EtCO2 (r = 0.41; P = 0.0001) and cerebral deoxygenation (-15 %) was noted in three patients while cerebral hyperoxygenation (+15 %) manifests in one patient. Thus changes in ScO2 were kept within acceptable limits (±15 %) in 91 % of the patients. For the majority of the patients undergoing AAA repair ScO2 was kept within reasonable limits by reducing ventilation by approximately 1 l min(-1) upon clamping of the aorta and increasing ventilation by approximately 2 l min(-1) when the lower body is reperfused.
authors.affiliation: Department of Anesthesia 2043, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen Ø, Denmark. hs770@hotmail.com.
authors.forename: H
authors.identifier: http://orcid.org/0000-0003-0819-106X
authors.initials: H
authors.lastname: Sørensen
authors.affiliation: Department of Anesthesia 2043, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen Ø, Denmark.
authors.forename: H B
authors.initials: HB
authors.lastname: Nielsen
authors.affiliation: Department of Anesthesia 2043, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen Ø, Denmark.
authors.forename: N H
authors.initials: NH
authors.lastname: Secher
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000777:Anesthetics; D001011:Aorta / Q000502:physiology; D017544:Aortic Aneurysm, Abdominal / Q000601:surgery*; D062186:Arterial Pressure; D001794:Blood Pressure; D001921:Brain / Q000378:metabolism; D002245:Carbon Dioxide / Q000737:chemistry*; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000737:chemistry*; D010101:Oxygen Consumption / Q000502:physiology; D010477:Perfusion; D012189:Retrospective Studies; D019265:Spectroscopy, Near-Infrared; D014691:Ventilation
chemical_list: D000777:Anesthetics; D002245:Carbon Dioxide; D010100:Oxygen
keywords: Carbon dioxide; Cerebral oximetry; Near infrared spectroscopy; Vascular surgery; Ventilation