Abstracts of Posters Presented at the International Anesthesia Research Society; 72nd Clinical and Scientific Congress; Orlando, FL; March 7-11, 1998: Cardiovascular Anesthesia
Introduction: Interest in xenon (XE) as an inhalational anesthetic has been rekindled recently as availability of scavenging systems may allow its cost-effective use. We tested the hypothesis that XE alters the effects of isoflurane (ISO) on systemic hemodynamics and myocardial contractility in vivo.
Methods: After Animal Care Committee approval, dogs (n=6) were chronically instrumented for measurement of aortic and LV pressure, +dP/dt, cardiac output (CO), and subendocardial segment length. Myocardial contractility was evaluated using preload recruitable stroke work slope (MW). Dogs were assigned to receive XE (30,50, and 65%; end-tidal concentrations) during 1.4 MAC ISO anesthesia or in combination with ISO to maintain a constant 1.4 MAC on separate days. MAC values were 1.28 and 71% for ISO and XE, respectively. Hemodynamics were recorded in the conscious state (C), after 30 min equilibration during ISO alone, and after 15 min equilibration at each dose of XE. Comparison between interventions was performed with ANOVA followed by Student's t-test with Duncan's correction for multiplicity (*P<0.05 versus ISO alone).
Results: ISO increased heart rate and decreased mean arterial and LV systolic pressures, +dP/dt, CO, systemic vascular resistance (SVR) and MW (Figure 1). Administration of XE to dogs anesthetized with 1.4 MAC ISO produced no hemodynamic effects. Administration of increasing concentrations of XE during reductions in ISO (constant MAC) increased mean arterial and LV systolic pressures, CO, +dP/dt, and MW. No changes in heart rate or SVR were observed when XE was gradually substituted for ISO.
Conclusion: The results indicate that XE is devoid of hemodynamic effects and does not alter myocardial contractility during ISO anesthesia. XE attenuated ISO-induced depression of myocardial contractility when substituted for this volatile agent to maintain constant MAC.