title: Peripheral circulation evaluation with near-infrared spectroscopy in skeletal muscle during cardiopulmonary bypass.
abstract: BACKGROUND
  We designed a non-invasive, observational, real-time study, using near-infrared spectroscopy (NIRS) to assess the in vivo effects of cardiopulmonary bypass (CPB) on patients' skeletal muscle as well as the effects of hemodilution and hypothermia on tissue oxygen delivery during CPB.
  
  
  METHODS
  The study included 20 consecutive adult patients undergoing open-heart surgery with CPB. Evaluation parameters for peripheral circulation were measured using the NIRO-200NX and recorded every 30 seconds. To assess how hemodilution influences peripheral circulation parameters, we compared data between a group of patients with hematocrit (Hct) values >22% (high Hct group) and those with Hct values ⩽22% (low Hct group).
  
  
  RESULTS
  Changes in the concentration of oxygenated hemoglobin (ΔO2Hb, μmol/L), which flows into the skeletal muscle, was an important factor for deciding the tissue oxygenation index (TOI%), showing the tissue oxygen saturation. The low Hct group showed a significant increase in the normalized tissue hemoglobin index (nTHI), showing the percentage change in the amount of initial hemoglobin and TOI compared to the high Hct group. Changes in the concentration of oxygenated hemoglobin (ΔO2Hb, μmol/L) and deoxygenated hemoglobin (ΔHHb, μmol/L) were significantly less in the low Hct group than in the high Hct group, thus, showing good peripheral circulation despite the low hematocrit levels.
  
  
  CONCLUSIONS
  Our study indicated the presence of a compensatory mechanism in which increased blood flow of the microcirculation is in compensation for the lack of oxyhemoglobin delivery caused by hemodilution.
authors.affiliation: Department of Clinical Engineering, Juntendo University Hospital, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Mukaida
authors.affiliation: Department of Cardiovascular Surgery, Juntendo University, Faculty of Medicine, Tokyo, Japan saty-m@juntendo.ac.jp.
authors.forename: S
authors.initials: S
authors.lastname: Matsushita
authors.affiliation: Department of Clinical Engineering, Juntendo University Hospital, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Inotani
authors.affiliation: Department of Clinical Engineering, Juntendo University Hospital, Tokyo, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Futaki
authors.affiliation: Department of Clinical Engineering, Juntendo University Hospital, Tokyo, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Takano
authors.affiliation: Department of Clinical Engineering, Juntendo University Hospital, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Department of Cardiovascular Surgery, Juntendo University, Faculty of Medicine, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Morita
authors.affiliation: Department of Clinical Laboratory Medicine, Juntendo University, Faculty of Medicine, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Miida
authors.affiliation: Department of Cardiovascular Surgery, Juntendo University, Faculty of Medicine, Tokyo, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Amano
mesh_terms: D000328:Adult; D000368:Aged; D002315:Cardiopulmonary Bypass / Q000379:methods*; D006400:Hematocrit; D006438:Hemodilution / Q000379:methods*; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008833:Microcirculation / Q000502:physiology*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D010101:Oxygen Consumption; D019265:Spectroscopy, Near-Infrared
chemical_list: D006454:Hemoglobins
keywords: adult cardiac surgery; hemodilution; microcirculation; near-infrared spectroscopy; oxyhemoglobin delivery