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Critical level of oxygen delivery in anesthetized man
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References
1983
Year
Oxygen ExtractionCardiac AnaesthesiaFifty-eight PatientsModerate DoseCardiovascular DiseaseMedicinePatient SafetyAnesthesia PracticePulmonary PhysiologyOxygen TherapyTissue OxygenationCritical LevelAnesthesiaPerioperative MedicineAnesthetic AdministrationCardiologyAnesthetic PharmacologyAnesthesiology
The study examined how oxygen consumption relates to oxygen delivery. The study measured 99 hemodynamic variables in 58 anesthetized patients after sternotomy and before cardiopulmonary bypass. A critical oxygen delivery of 330 ml/min/m² (8.2 ml/min/kg) was identified; below this threshold VO₂ fell linearly with DO₂, while above it VO₂ plateaued, indicating tissue oxygen deprivation when DO₂ is insufficient.
Fifty-eight patients studied were anesthetized with diazepam, pancuronium, and a moderate dose of fentanyl; 99 sets of multiple hemodynamic variables were measured after sternotomy and before cardiopulmonary bypass. The relationship between oxygen consumption (VO2) and oxygen delivery (DO2) was studied. The critical value of DO2 was identified to be 330 ml/min X M2 or 8.2 ml/min X kg by an analysis of the regression lines. When DO2 was less than 330 ml/min X M2, the value of VO2 decreased in proportion to a decrease in DO2 and VO2 was expressed as: VO2 = 0.36 X DO2 - 11.20 (n = 30, r = 0.77, p less than 10(-6). At DO2 greater than 330 ml/min X M2, VO2 values plateaued at 109 +/- 16 (SD): n = 69; r = -0.02, p greater than 0.05; while mixed venous oxygen tension (PVO2) decreased in proportion to the decrease in DO2, suggesting compensatory increase of oxygen extraction. A decrease of VO2 at DO2 less than 330 ml/min X M2 suggests tissue oxygen deprivation occurred.