Biomedical subjects

B J Leone

Publications and source records attributed to B J Leone.

39 records · Page 3Linked to original sources

PubMed1988

Gradual or abrupt nitrous oxide administration in a canine model of critical coronary stenosis induces regional myocardial dysfunction that is worsened by halothane.

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 micrograms/kg bolus plus 1.5 micrograms.kg-1.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 less than 0.05) and 60% (4.2 +/- 2.3% to 12.5 +/- 3.6%, P less than 0.05) inspired nitrous oxide (gradual administration) and also during abrupt 60% nitrous oxide administration (6.4 +/- 2.6% to 9.9 +/- 3.2%, P less than 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 less than 0.05) and peak LV dP/dt (1700 +/- 150 mm Hg/sec to 1100 +/- 100 mm Hg/sec, P less than 0.05). Halothane caused a marked increase in PSS (9.9 +/- 3.2% to 30.8 +/- 12.6%, P less than 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Calcium reverses global and regional myocardial dysfunction caused by the combination of verapamil and halothane.

In order to evaluate the effects of the combination of halothane and verapamil on left ventricular function and coronary blood flow (CBF), six sheep were anaesthetized with halothane (1.2% inspired) and given increasing cumulative doses of intravenous verapamil. Regional myocardial function was assessed by sonomicrometry in the areas supplied by the left anterior descending coronary artery (LAD) and the left circumflex coronary artery (LC). Changes in global haemodynamics, atrioventricular conduction, LV relaxation and systolic shortening after 0.32 mg X kg-1 intravenous verapamil indicated impaired left ventricular function. Significant myocardial dysfunction (post-systolic shortening) occurred in the LAD territory, accompanied by a 64% decrease (42 +/- 6 to 15 +/- 3, P less than 0.01) in coronary perfusion pressure (CPP). Coronary blood flow in the LC segment decreased 83% (102 +/- 15 to 17 +/- 13, P less than 0.01) as coronary reserve was exhausted with the decrease in CPP. Calcium chloride reversed the impairment of global and regional myocardial function observed with verapamil, improved the impaired left ventricular relaxation, but did not significantly alter atrioventricular conduction. Thus the combination halothane-verapamil can cause significant left ventricular depression and myocardial dysfunction, possibly by inducing subendocardial ischaemia or by direct pharmacologic effect. Calcium chloride reverses this regional myocardial dysfunction as well as the deleterious global haemodynamic changes caused by halothane-verapamil; however, the changes in atrioventricular conduction are not corrected by calcium.

Animals↗

PubMed1987

Beta-blockade reverses regional dysfunction in ischemic myocardium.

To determine the protective effect of oxprenolol-induced beta-blockade on the compromised myocardium (critical constriction of the left anterior descending coronary artery) against the adverse effect of high concentrations of halothane, halothane dose-response curves were obtained in six dogs in each of three phases: preconstriction (control), critical constriction, and critical constriction with the addition of 0.3 mg/kg intravenous oxprenolol. The extent of depression of ventricular function was essentially the same in the three phases. However, at high halothane concentrations (2.0% inspired), the depression of systolic shortening in the compromised segment was significantly minimized after oxprenolol so that shortening was 10.2% +/- 1.8 instead of 6.5% +/- 1.4 (P less than 0.05); moreover the large increase in postsystolic shortening observed during critical constriction was abolished after oxprenolol. This suggests a protective effect of oxprenolol on regional myocardial function in the presence of critical constriction, possibly by an effect on myocardial metabolism or endocardial blood flow.

Adrenergic beta-Antagonists↗