title: Near infrared spectrophotometry reflects cerebral metabolism during hypothermic circulatory arrest in adults.
abstract: Near-infrared spectrophotometry (NIRS) is assumed to reflect cerebral oxygenation during hypothermic circulatory arrest (HCA). However, the rationale for the use of NIRS as a marker of cerebral metabolism remains to be elucidated. We examined whether cerebral oxygenation measured by NIRS correlated with cerebral metabolic function assessed by cerebral oxygen extraction ratio (OER) during HCA in adults. NIRS was continuously monitored in 14 patients undergoing thoracic aortic surgery using HCA (17.9 +/- 2.9 degrees C esophageal temperature at HCA onset). Jugular venous oxygen saturation and OER were also monitored. OER was significantly reduced from 37.3 +/- 7.2% at the onset of cardiopulmonary bypass to 13.6 +/- 6.2% at the onset of HCA (p < 0.0001). A linear decrease in oxygenated-hemoglobin (oxy-Hb) and increase in deoxygenated-hemoglobin (deoxy-Hb) were found during HCA, which returned to baseline levels after rewarming. The rate of decrease in oxy-Hb and increase in deoxy-Hb were -0.63 +/- 0.45 and 0.51 +/- 0.30 (10(-5) OD/cm per sec), respectively, both of which significantly correlated with OER at the onset of HCA (R2=0.739 and 0.633; p < 0.0001 and p = 0.0007, respectively). NIRS may serve as a reliable diagnostic modality for monitoring cerebral metabolism during aortic surgery using HCA.
authors.affiliation: Department of Cardiovascular Surgery, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kunihara
authors.forename: S
authors.initials: S
authors.lastname: Sasaki
authors.forename: N
authors.initials: N
authors.lastname: Shiiya
authors.forename: T
authors.initials: T
authors.lastname: Murashita
authors.forename: Y
authors.initials: Y
authors.lastname: Matsui
authors.forename: K
authors.initials: K
authors.lastname: Yasuda
mesh_terms: D000328:Adult; D000368:Aged; D001011:Aorta / Q000601:surgery; D002315:Cardiopulmonary Bypass; D002540:Cerebral Cortex / Q000098:blood supply / Q000378:metabolism*; D005260:Female; D006801:Humans; D007036:Hypothermia, Induced; D007601:Jugular Veins; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D010100:Oxygen / Q000097:blood; D010108:Oxyhemoglobins / Q000032:analysis; D019265:Spectroscopy, Near-Infrared
chemical_list: D010108:Oxyhemoglobins; D010100:Oxygen