Thoracic epidural analgesia and the cardiovascular system

Thoracic epidural anesthesia (TEA) with local anesthetics influences various aspects of the cardiac functions. It reduces the sympathetic tone, and it blocks the cardiac accelerator fibers. There is an overall decrease in the incidence of dysrhythmias, but not atrial fibrillation. TEA preserves left ventricular function and wall motion in patients undergoing cardiac surgery. Myocardial oxygen consumption is reduced with TEA while coronary perfusion pressure is maintained, thus protecting the heart from ischemic insults. The changes in clinical markers are not significant; however, Brain Natriuretic Peptide was reported to be reduced. Hypotension after TEA is partly the result of some cardiodepressant action and mostly due to arterial and venous vasodilatation. The inhibitory effect on the vasoconstrictor sympathetic outflow appears to be responsible for functional hypovolemia, but there are no changes in intravascular volume or in hemoglobin concentration. If the sympathetic block is limited to a few segments, there is a compensatory vasoconstriction in the unblocked areas. Otherwise, vasopressors remain the preferred treatment for hypotension over intravenous fluids when the block is extended to more than 6 to 8 dermatomes. TEA has been shown to increase the survival following hemorrhagic shock, but the block has to be initiated beforehand and should cover the thoracolumbar area.