GRADUAL OR ABRUPT NITROUS-OXIDE ADMINISTRATION IN A CANINE MODEL OF CRITICAL CORONARY STENOSIS INDUCES REGIONAL MYOCARDIAL DYSFUNCTION THAT IS WORSENED BY HALOTHANE

  • 1 September 1988
    • journal article
    • research article
    • Vol. 67  (9) , 814-822
Abstract
The existence of a dose-response relation between nitrous oxide concentration and regional dysfunction in compromised myocardium, and whether or not halothane-induced myocardial depression alleviated this regional dysfunction was examined. Nitrous oxide was administered to eight dogs with experimentally induced left anterior descending coronary artery (LAD) critical stenosis during fentanyl (100 .mu.g/kg bolus plus 1.5 .mu.g .cntdot. kg-1 .cntdot. min-1) anesthesia. Two modes of nitrous oxide administration were employed: gradual (in steps of 20% inspired, i.e., 0%, 20%, 40%, and 60% inspired) and abrupt (0-60% inspired). Regional myocardial function was assessed by sonomicrometry. Regional dysfunction in the compromised myocardium, in the form of postsystolic shortening (PSS), increased above baseline levels during 40% (4.2 .+-. 2.3% to 12.1 .+-. 3.9%, P < 0.05) and 60% (4.2 .+-. 2.3% to 12.5 .+-. 3.6%, P < 0.05) inspired nitrous oxide (gradual administration) and also durng abrupt 60% nitrous oxide administration (6.4 .+-. 2.6% of 9.9 .+-. 3.2%, P < 0.05). After abrupt 60% inspired nitrous oxide administration, halothane (0.7% inspired) was introduced and caused decreases in mean arterial pressure (106.1 .+-. 4.5 mm Hg to 76.2 .+-. 5.5 mm Hg, P < 0.05) and peak LV dP/dt (1700 .+-. 150 mm Hg/sec to 1100 .+-. 100 mm Hg/sec, P < 0.05). Halothane caused a marked increase in PSS (9.9 .+-. 3.2% to 30.8 .+-. 12.6%, P < 0.05). Thus nitrous oxide administration caused regional dysfunction in myocardium supplied by a critically narrowed LAD whether administered gradually or abruptly and at concentrations as low as 40% inspired. The addition of halothane to decrease myocardial oxygen demand resulted in marked worsening, rather than alleviation, of regional myocardial dysfunction.