Myocardial depressant effect of nitrous oxide after valve surgery.
We have studied the cardiovascular effects of 50% nitrous oxide after cardiopulmonary bypass in 14 patients undergoing valve surgery. All patients received morphine as the principal anaesthetic. Nitrous oxide administration for 5 min caused a decrease in mean arterial pressure from 82 +/- 10 to 71 +/- 12.7 mmHg (P < 0.001), cardiac index (2.8 +/- 0.5 to 2.4 +/- 0.5 litres min-1 m-2, P < 0.01), heart rate (104 +/- 17 to 99 +/- 18 beats min-1, P < 0.05), left ventricular stroke work index (29.4 +/- 8.1 to 22 +/- 8.7 gm-m beat-1 mm-1, P < 0.001), stroke volume (45.3 +/- 11.6 to 40 +/- 12.8 ml beat-1, P < 0.05) and an increase in pulmonary vascular resistance from 106.4 +/- 53.9 to 143.9 +/- 81.0 dynes s cm-5 (P < 0.01) and right atrial pressure (1.42 +/- 2.09 to 1.71 +/- 2.21 mmHg, P < 0.05). There was no change in systemic vascular resistance. When nitrous oxide was discontinued all the parameters started to recover within 3 min. Mean arterial pressure returned to control value in 5 min, but cardiac index and pulmonary vascular resistance returned to control value in 10 min. Our results suggest a direct myocardial depression and that the use of nitrous oxide is not recommended immediately after valve surgery and cardiopulmonary bypass.
Tempe
D
D
Department of Anaesthesia and Cardiac Surgery, G.B. Pant Hospital, New Delhi, India.
Mohan
J C
JC
Cooper
A
A
Tomar
A S
AS
Khanna
S K
SK
Satsangi
D K
DK
Sinha
S K
SK
Bajwa
R
R
Lall
N G
NG
D000328:Adult; D001021:Aortic Valve / Q000601:surgery*; D016280:Atrial Function, Right / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D002315:Cardiopulmonary Bypass; D005260:Female; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008943:Mitral Valve / Q000601:surgery*; D009020:Morphine / Q000008:administration & dosage; D009609:Nitrous Oxide / Q000009:adverse effects*; D011651:Pulmonary Artery / Q000502:physiology; D011669:Pulmonary Wedge Pressure / Q000187:drug effects; D013318:Stroke Volume / Q000187:drug effects; D013997:Time Factors; D014655:Vascular Resistance / Q000187:drug effects; D016277:Ventricular Function, Left / Q000187:drug effects; D016278:Ventricular Function, Right / Q000187:drug effects
D009020:Morphine; D009609:Nitrous Oxide