Background: Spinal anesthesia reduces arterial blood pressure mainly because of vasodilation secondary to blocking preganglionic fibers in the sympathetic nervous system. It is hypothesized, however, that spinal anesthesia may also be a direct cause of some degree of myocardial depression. These factors may be studied by means of transthoracic echocardiography to detect changes in left ventricular function following start of spinal anesthesia.
Material and methods: Left ventricular function was assessed in ASA 1 patients before spinal anesthesia, by means of measurements of left ventricular systolic and diastolic volumes, ejection fraction, the Doppler transmitral (E and A) and tissue (E', A', and Sm) inflow velocities, and the left ventricular outflow tract velocity. The measurements were repeated after the start of spinal anesthesia.
Results: Fifty-five patients (58% men; mean [SD] age, 46.9 [15.7] years) were studied. The spinal block caused a significant reduction in systolic and diastolic arterial blood pressures (P < .0009). Diastolic function also decreased (the E wave from 69.52 [11.24] to 61.59 [10.82] cm x s(-1) and the A wave from 50.18 [10.69] to 43.67 [13.75] cm x s(-1); P < .0001). Also reduced was the left ventricular outflow tract velocity, from 18.77 (4.89) to 15.64 (4.75) cm x s(-1) (P < .00001). There were no significant changes in systolic and diastolic volumes or ejection fraction. There was no correlation between the level of spinal block and the magnitude of changes.
Conclusions: Left ventricular function was compromised after spinal anesthesia without significant changes in left ventricular volumes. We can infer that the reduction in arterial blood pressure after a spinal block might be due to some degree of direct ventricular depression.