Document Detail

Critical oxygen delivery in conscious humans is less than 7.3 ml O2 x kg(-1) x min(-1).
MedLine Citation:
PMID:  10691227     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: The "critical" level of oxygen delivery (DO2) is the value below which DO2 fails to satisfy the metabolic need for oxygen. No prospective data in healthy, conscious humans define this value. The authors reduced DO2 in healthy volunteers in an attempt to determine the critical DO2. METHODS: With Institutional Review Board approval and informed consent, the authors studied eight healthy, conscious volunteers, aged 19-25 yr. Hemodynamic measurements were obtained at steady state before and after profound acute isovolemic hemodilution with 5% albumin and autologous plasma, and again at the reduced hemoglobin concentration after additional reduction of DO2 by an infusion of a beta-adrenergic antagonist, esmolol. RESULTS: Reduction of hemoglobin from 12.5+/-0.8 g/dl to 4.8+/-0.2 g/dl (mean +/- SD) increased heart rate, stroke volume index, and cardiac index, and reduced DO2 (14.0+/-2.9 to 9.9+/-20 ml O2 x kg(-1) x min(-1); all P<0.001). Oxygen consumption (VO2; 3.0+/-0.5 to 3.4+/-0.6 ml O2 x kg(-1) x min(-1); P<0.05) and plasma lactate concentration (0.50+/-0.10 to 0.62+/-0.16 mM; P<0.05; n = 7) increased slightly. Esmolol decreased heart rate, stroke volume index, and cardiac index, and further decreased DO2 (to 7.3+/-1.4 ml O2 x kg(-1) x min(-1); all P<0.01 vs. before esmolol). VO2 (3.2+/-0.6 ml O2 x kg(-1) x min(-1); P>0.05) and plasma lactate (0.66+/-0.14 mM; P>0.05) did not change further. No value of plasma lactate exceeded the normal range. CONCLUSIONS: A decrease in DO2 to 7.3+/-1.4 ml O2 x kg(-1) min(-1) in resting, healthy, conscious humans does not produce evidence of inadequate systemic oxygenation. The critical DO2 in healthy, resting, conscious humans appears to be less than this value.
J A Lieberman; R B Weiskopf; S D Kelley; J Feiner; M Noorani; J Leung; P Toy; M Viele
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Anesthesiology     Volume:  92     ISSN:  0003-3022     ISO Abbreviation:  Anesthesiology     Publication Date:  2000 Feb 
Date Detail:
Created Date:  2000-03-06     Completed Date:  2000-03-06     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  1300217     Medline TA:  Anesthesiology     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  407-13     Citation Subset:  AIM; IM    
Department of Anesthesia, The Cardiovascular Research Institute, University of California, San Francisco 94143-0648, USA.
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MeSH Terms
Adrenergic beta-Antagonists / pharmacology
Cardiac Output / drug effects
Hemodynamics / physiology
Hemoglobins / metabolism
Lactic Acid / blood
Oxygen / administration & dosage*,  blood
Oxygen Consumption / physiology*
Propanolamines / pharmacology
Grant Support
Reg. No./Substance:
0/Adrenergic beta-Antagonists; 0/Hemoglobins; 0/Propanolamines; 50-21-5/Lactic Acid; 7782-44-7/Oxygen; 84057-94-3/esmolol

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