ISOFLURANE VERSUS SODIUM-NITROPRUSSIDE FOR THE CONTROL OF PROXIMAL HYPERTENSION DURING THORACIC AORTIC CROSS-CLAMPING - EFFECTS ON SPINAL-CORD ISCHEMIA

Objective: This study was designed to compare the effects of isofluran e and nitroprusside on spinal cord ischemia when they are used to cont rol proximal hypertension during thoracic aortic cross-cramping (TACC) . Design: Prospective, randomized, blinded experimental study. Setting : Laboratory and animal research facility. Participants: Adult mongrel dogs. Interventions: Two groups of eight dogs had TACC for 45 minutes . Proximal aortic, distal aortic, and cerebrospinal fluid (CSF) pressu res were monitored. Spinal cord perfusion pressure was calculated as t he distal mean pressure minus the CSF pressure. Group 1 received nitro prusside and group 2 received isoflurane to control proximal hypertens ion during cross-clamping. The dogs were neurologically evaluated 24 a nd 48 hours later by an observer blinded as to the study group. Spinal cord segments were obtained for histopathologic examination. Measurem ents and Main Results: Distal perfusion pressure and spinal cord perfu sion pressure were significantly higher in the isoflurane group (p <.0 05). At 24 hours, seven of eight dogs in group 1 had severe neurologic injury tie, paraplegia), with the eighth having mild neurologic injur y. This is in contrast to group 2, where 6 of 8 dogs had either minima l or no injury, one had mild injury, and one had severe injury. Simila r results were observed at 48 hours (p <.005). Conclusions: Isoflurane , when used to control proximal hypertension during TACC, produces a h igher spinal cord perfusion pressure and is associated with a lower in cidence of neurologic injury than nitroprusside in this canine model. (C) 1995 by WB. Saunders Company