Nitrous oxide produces minimal hemodynamic changes in patients receiving a propofol-based anesthetic: an esophageal Doppler ultrasound study.
OBJECTIVE
Nitrous oxide (N(2)O) is a frequently used adjunct to propofol anesthesia. Although N(2)O reduces the requirement of propofol for induction and maintenance, the effects of both drugs on overall hemodynamics remain controversial. We tested the hypothesis that the addition of N(2)O to therapeutic doses of propofol alters hemodynamics and Doppler-derived variables evaluated with the esophageal Doppler monitor in a randomized, double-blinded, placebo-controlled design.


METHODS
Thirty ASA I-II patients (aged 30-66 yr) were randomly assigned to receive propofol with oxygen-enriched air (FIO(2) = 0.3; air group) or propofol with 70% N(2)O (N(2)O group). Following intubation, a computerized target-controlled infusion technique was used to administer propofol from 0 micro g x mL(-1) (baseline) to 5 micro g x mL(-1) in 1 micro g x mL(-1) increments.


RESULTS
Mean arterial pressure (MAP) decreased more in the N(2)O group than in the air group only at 5 micro g x mL(-1). Aortic blood flow (ABF) showed a similar dose-dependent decrease in both groups. Peak aortic flow acceleration, as a myocardial contractility index, decreased significantly and similarly in both groups in a dose-dependent manner whereas peak velocity of ABF, as another measure of myocardial contractility, remained unchanged. Heart rate-corrected left ventricular ejection time, as a measure of preload, remained constant in both groups at any target plasma concentration.


CONCLUSIONS
Propofol causes dose-dependent decreases in ABF and MAP; however, 70% N(2)O produces minimal hemodynamic and Doppler-derived variable changes under target-controlled propofol infusion at therapeutic concentrations.
Shiga
Toshiya
T
Department of Anesthesia, Chiba Hokusoh Hospital, Nippon Medical School, Chiba, Japan. Shigat@aol.com
Wajima
Zen'ichiro
Z
Inoue
Tetsuo
T
Ogawa
Ryo
R
D000328:Adult; D000368:Aged; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D001011:Aorta / Q000000981:diagnostic imaging / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide / Q000494:pharmacology*; D015742:Propofol / Q000494:pharmacology*; D018608:Ultrasonography, Doppler
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D009609:Nitrous Oxide; D015742:Propofol