Dissociation of mixed venous oxygen saturation and cardiac index during opioid induction.
OBJECTIVE
To evaluate the independent effects of opioid induction and paralysis on changes in mixed venous oxygen saturation (SvO2).


METHODS
Prospective, with each patient serving as his or her own control.


METHODS
Cardiac operating rooms of a major U.S. teaching hospital.


METHODS
15 elective patients for aortocoronary bypass graft surgery.


METHODS
Prior to induction with sufentanil 2 to 3 micrograms/kg (t1), after recovery from succinylcholine 1 to 1.5 mg/kg (t2), and after subsequent paralysis with vecuronium (t3), we recorded cardiac index (VO2), arterial oxygen saturation (SaO2), and SvO2, then calculated oxygen consumption (VO2) and arterial oxygen content (CaO2).


RESULTS
SvO2 increased from 75% at t1 to 82% at t2 (p = 0.03) and to 83% at t3 (p = 0.006). CI decreased from 3.1 L/min/m2 at t1 to 2.5 L/min/m2 at t2 (p = 0.023) and to 2.1 L/min/m2 at t3 (t1 vs. t3, p = 0.019; t2 vs. t3, p = NS). Calculated VO2 decreased from 2.88 ml O2/min/kg at t1 to 2.09 ml O2/min/kg at t2 (p = 0.03) and to 1.87 ml O2/min/kg at t3 (t1 vs. t3, p = 0.002; t2 vs. t3, p = 0.027). CaO2 remained unchanged.


CONCLUSIONS
Opioid anesthesia, not paralysis, increases SvO2. Most of the decrease in VO2 occurs from anesthesia, not paralysis. The direct relationship between CI and SvO2 no longer holds upon induction of anesthesia. Parallel changes in CI cannot be inferred based on SvO2 alone.
Colonna-Romano
P
P
Department of Anesthesiology, Hahnemann University, Philadelphia, PA 19102-1192.
Horrow
J C
JC
D000368:Aged; D000771:Anesthesia, Intravenous; D001158:Arteries; D002302:Cardiac Output / Q000187:drug effects / Q000502:physiology*; D001026:Coronary Artery Bypass; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D011446:Prospective Studies; D013390:Succinylcholine / Q000494:pharmacology; D017409:Sufentanil / Q000494:pharmacology; D014673:Vecuronium Bromide / Q000494:pharmacology; D014680:Veins
D006454:Hemoglobins; D014673:Vecuronium Bromide; D017409:Sufentanil; D013390:Succinylcholine; D010100:Oxygen