Desflurane, sevoflurane, and isoflurane affect left atrial active and passive mechanical properties and impair left atrial-left ventricular coupling in vivo - Analysis using pressure-volume relations

Background The effects of volatile anesthetics on left atrial function in v ivo have not been described. The authors tested the hypothesis that desflur ane, sevoflurane, and isoflurane alter left atrial mechanics evaluated with invasively derived pressure-volume relations. Methods: Barbiturate-anesthetized dogs (n = 24) were Instrumented for measu rement of aortic, left atrial, and left ventricular pressures (micromanomet ers) and left atrial volume (orthogonal sonomicrometers). Left atrial contr actility and chamber stiffness were assessed with end-systolic and end-rese rvoir pressure-volume relations, respectively, obtained from differentially loaded diagrams. Relaxation was determined from the slope of left atrial p ressure decline after contraction. Stroke work and reservoir function were assessed by A and V loop areas, respectively. Left atrial-left ventricular coupling was determined by the ratio of left atrial contractility and left ventricular elastance. Dog, received 0.6, 0.9, and 1.2 minimum alveolar con centration desflurane, sevoflurane, or isoflurane in a random manner, and l eft atrial function was determined after 20-min equilibration at each dose. Results: Desflurane, sevoflurane, and isoflurane decreased heart rate, mean arterial pressure, and maximal rate of increase of left ventricular pressu re and increased left atrial end-diastolic, end-systolic, and maximum volum es. All three anesthetics caused dose-related reductions in left atrial con tractility, relaxation, chamber stiffness, and stroke work. Administration of 0.6 and 0.9 minimum alveolar concentration desflurane, sevoflurane, and isoflurane increased V loop area. All three anesthetics decreased the ratio of stroke work to total left atrial pressure-volume diagram area, increase d the ratio of conduit to reservoir volume, and reduced left atrial contrac tility-left ventricular elastance to equivalent degrees. Conclusions. The results indicate that desflurane, sevoflurane, and isoflur ane depress left atrial contractility, delay relaxation, reduce chamber sti ffness, preserve reservoir and conduit function, and impair left atrial-lef t ventricular coupling in vivo.