title: High oxygen partial pressure decreases anemia-induced heart rate increase equivalent to transfusion.
abstract: BACKGROUND
  Anemia is associated with morbidity and mortality and frequently leads to transfusion of erythrocytes. The authors sought to directly compare the effect of high inspired oxygen fraction versus transfusion of erythrocytes on the anemia-induced increased heart rate (HR) in humans undergoing experimental acute isovolemic anemia.
  
  
  METHODS
  The authors combined HR data from healthy subjects undergoing experimental isovolemic anemia in seven studies performed by the group. HR changes associated with breathing 100% oxygen by nonrebreathing facemask versus transfusion of erythrocytes at their nadir hemoglobin concentration of 5 g/dl were examined. Data were analyzed using a mixed-effects model.
  
  
  RESULTS
  HR had an inverse linear relationship to hemoglobin concentration with a mean increase of 3.9 beats per min per gram of hemoglobin (beats/min/g hemoglobin) decrease (95% CI, 3.7-4.1 beats/min/g hemoglobin), P < 0.0001. Return of autologous erythrocytes significantly decreased HR by 5.3 beats/min/g hemoglobin (95% CI, 3.8-6.8 beats/min/g hemoglobin) increase, P < 0.0001. HR at nadir hemoglobin of 5.6 g/dl (95% CI, 5.5-5.7 g/dl) when breathing air (91.4 beats/min; 95% CI, 87.6-95.2 beats/min) was reduced by breathing 100% oxygen (83.0 beats/min; 95% CI, 79.0-87.0 beats/min), P < 0.0001. The HR at hemoglobin 5.6 g/dl when breathing oxygen was equivalent to the HR at hemoglobin 8.9 g/dl when breathing air.
  
  
  CONCLUSIONS
  High arterial oxygen partial pressure reverses the heart rate response to anemia, probably because of its usability rather than its effect on total oxygen content. The benefit of high arterial oxygen partial pressure has significant potential clinical implications for the acute treatment of anemia and results of transfusion trials.
authors.affiliation: Department of Anesthesia and Perioperative Care, University of California, San Francisco, California 94143-0648, USA. feinerj@anesthesia.ucsf.edu
authors.forename: John R
authors.initials: JR
authors.lastname: Feiner
authors.forename: Heather E
authors.initials: HE
authors.lastname: Finlay-Morreale
authors.forename: Pearl
authors.initials: P
authors.lastname: Toy
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Lieberman
authors.forename: Maurene K
authors.initials: MK
authors.lastname: Viele
authors.forename: Harriet W
authors.initials: HW
authors.lastname: Hopf
authors.forename: Richard B
authors.initials: RB
authors.lastname: Weiskopf
mesh_terms: D000328:Adult; D000740:Anemia / Q000503:physiopathology* / Q000628:therapy*; D001803:Blood Transfusion; D017707:Erythrocyte Transfusion; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006438:Hemodilution; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D010102:Oxygen Inhalation Therapy; D012044:Regression Analysis
chemical_list: D006454:Hemoglobins