Isobaric spinal anesthesia for paraplegic patients

It has long been understood that patients with spinal cord injury (SCI) above T6-7 may develop autonomic hyperreflexia (AH) and pose an anesthetic challenge. To date, there is no consensus regarding anesthesia management of these patients among anesthesiologists. Many anesthetic techniques have been proposed and used with varying success, but none of them is uniformly successful. Topical anesthetics may not block the stretch receptors and AH might still be initiated. A deep anesthesia with potent volatile agents is often necessary to prevent or treat AH. Thus, the incidence of hypotension is no different than that associated with neuraxial anesthesia. Failures with potent vasodilators such as sodium nitroprusside also have been reported. Currently, the block of the afferent pathways by neuraxial anesthesia is considered to be the most effective means of preventing AH. However, because the level of neuraxial anesthesia is difficult to detect in SCI patients, excessive high level block and subsequent severe hypotension may occur. When an isobaric solution is used, due to the lack of baricity/patient position interaction, migration of the local anesthetic is usually insignificant, so the level of anesthesia is easier to control and predict. In the past fifteen years (1982-1997), we have used isobaric spinal anesthesia (ISA) in thirteen patients with SCI for various surgical procedures. Although four of these patients had previous history of AH, there was not a single incidence of AH during the perioperative period. Our favorable experiences lead us to believe that ISA is a useful anesthetic technique for SCI patients undergoing surgery.