title: Blood Transfusions May Have Limited Effect on Muscle Oxygenation After Total Knee Arthroplasty.
abstract: BACKGROUND
  Traditionally, blood transfusions in the perioperative setting are used to maintain adequate delivery of nutrients and oxygen to organs. However, the effect of blood administration on tissue oxygenation in the perioperative setting remains poorly understood.
  
  
  OBJECTIVE
  The aim of this study was to determine changes in muscle tissue oxygenation saturation (SmO2) in response to perioperative blood transfusions.
  
  
  METHODS
  Patients undergoing total knee arthroplasty were enrolled. SmO2, continuous hemoglobin (SpHb), stroke volume (SV), cardiac index, and standard hemodynamic parameters including heart rate (HR), mean arterial blood pressure (MAP), and arterial oxygen saturation (SO2) were recorded. To assess fluid responsiveness, a passive leg raise (PLR) test was performed before the transfusions were started.
  
  
  RESULTS
  Twenty-eight patients were included in the analysis. Mean (±SD) SmO2 before transfusion was 63.18 ± 10.04%, SpHb was 9.27 ± 1.16 g/dl, and cardiac index was 2.62 ± 0.75 L/min/m(2). A significant increase during the course of blood transfusion was found for SmO2 (+3.44 ± 5.81% [95% confidence interval (CI) 1.04 to 5.84], p = 0.007), SpHb (0.74 ± 0.92 g/dl [95% CI 0.35 to 1.12], p < 0.001), and cardiac index (0.38 ± 0.51 L/min/m2 [95% CI 0.15 to 0.60], p = 0.002), respectively. However, the correlation between SmO2 and SpHb over the course of the transfusion was negligible (ρ = 0.25 [95% CI -0.03 to 0.48]). A similar lack of correlation was found when analyzing data of those patients who showed a positive leg raise test before the start of the transfusion (ρ = 0.37 [95% CI -0.11 to 0.84]).
  
  
  CONCLUSIONS
  We detected a statistically significant increase in SmO2 during the course of a single unit blood transfusion compared to baseline. However, there was no evidence of a correlation between longitudinal SmO2 and SpHb measurements.
authors.affiliation: Department of Anesthesiology, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Stavros G
authors.initials: SG
authors.lastname: Memtsoudis
authors.affiliation: Department of Anesthesiology, State Hospital of Salzburg, Salzburg, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Danninger
authors.affiliation: Department of Anesthesiology, State Hospital of Salzburg, Salzburg, Austria.
authors.forename: Ottokar
authors.initials: O
authors.lastname: Stundner
authors.affiliation: Department of Anesthesiology, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Yoo
authors.affiliation: Department of Orthopedics, Hospital for Special Surgery, New York, NY USA.
authors.forename: Federico P
authors.initials: FP
authors.lastname: Girardi
authors.affiliation: Department of Orthopedics, Hospital for Special Surgery, New York, NY USA.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Boettner
authors.affiliation: College of Medicine, SUNY Downstate Medical Center, New York, NY USA.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Kao
authors.affiliation: Healthcare Research Institute, Hospital for Special Surgery, New York, NY USA.
authors.forename: Kara G
authors.initials: KG
authors.lastname: Fields
authors.affiliation: Department of Anesthesiology, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 USA.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Urban
authors.affiliation: Department of Anesthesiology, UMass Memorial Medical Center, Worcester, MA USA.
authors.forename: Stephen O
authors.initials: SO
authors.lastname: Heard
authors.affiliation: Department of Anesthesiology, UMass Memorial Medical Center, Worcester, MA USA.
authors.forename: J Matthias
authors.initials: JM
authors.lastname: Walz
keywords: blood transfusion; muscle tissue oxygenation; near-infrared spectroscopy; total knee arthroplasty