Atrial Activity and Systemic Blood Pressure during Anesthesia in Man

Atrial contribution to ventricular performance was evaluated during halothane anesthesia in man by a method whereby atrioventricular dissociation is readily induced. Three conditions are outlined that facilitate production of this arrhythmia in man: general anesthesia with a halothane-oxygen mixture by use of an average inspired halothane concentration of 0.5 per cent; controlled ventilation following muscle paralysis with d-tubocurare; and an exogenous stimulus, most easily provided by the onset of surgery. The last factor is probably mediated via direct sympathetic stimuli to the heart.The change from sinoatrial to atrioventricular nodal rhythm was associated with a fall in arterial pressure and a rise in central venous pressure; the heart rate remained unaltered. The changes in the systemic and central venous pressures were attributed to failure of atrial systole to contribute to ventricular filling during diastole.It is suggested that tricuspid regurgitation may occur during nodal rhythm, since synchronous atrioventricular contraction is required for adequate closure of the atrioventricular valve. Further studies of this problem in anesthetized man with this particular pharmacologic tool are indicated.