What anesthetic techniques are applicable to patients with cardiac transplants?
General anesthesia, spinal anesthesia, epidural anesthesia, regional blockade (axillary, wrist, ankle, and Bier blocks), and local infiltration have all been used successfully in this population. The choice of agents for general anesthesia is not crucial. Multiple small doses titrated to effect frequently works out best. Induction agents, benzodiazepines, opioids, and potent inhalation agents are usually well tolerated. All the usual caveats apply in the presence of renal or hepatic dysfunction. Early (if not immediate) postoperative extuba-tion is preferable, because prolonged intubation increases the risk of pulmonary infection.
Plasma levels of various anesthetic agents which depend on P450 metabolism may be increased or decreased by immunosuppressive and anticonvulsant medications, and can themselves alter immunosuppressant blood levels. Increased blood levels of immunosuppressants result in undesirable side-effects (e.g., nephrotoxicity of cyclosporine and tacrolimus). Administered agents which compete for P450 metabolism (e.g., furosemide) can decrease cyclosporine elimination and increase blood levels. Agents which increase cyclosporine metabolism (e.g., barbitu-rates) can lower blood levels.
It is believed that neuromuscular blockade is augmented by cyclosporine, and can be antagonized by anticonvulsants (e.g., phenytoin) often given to patients on immunosuppres-sants with seizures. However, this should not pose a problem if close monitoring of neuromuscular blockade is used.
Regardless of technique, volume depletion and acute vasodilation (e.g., as may occur with spinal anesthesia) will be poorly tolerated because the transplanted heart initially depends on the Frank-Starling mechanism to maintain cardiac output. Sudden vasodilation will not result in a reflex tachycardia. One certainly can perform a spinal anes-thetic in the post-transplantation patient, but one must be prepared to augment preload and prevent sudden decreases in systemic vascular resistance. It is often said that an epidural technique with a level brought up gradu-ally results in better hemodynamic stability.