Spinal cord injury immediately decreases anesthetic requirements in rats

Abstract

Study design: Pharmacologically blocking the spinal cord produces sedative effects and reduces anesthesia requirements in patients and animals. Whether spinal cord injury also reduces anesthesia requirements remains unclear. Methods: We retrospectively analyzed data from urethane-anesthetized rats 15 to assess anesthesia requirements immediately after complete thoracic transection of the spinal cord. The depth of anesthesia was monitored up to 12 h after spinal transection by the reflexes to noxious stimuli and by electrophysiological recordings from the infragranular layers of the primary somatosensory cortex. Whenever animals displayed electrophysiological and/or behavioral signs of activation, we delivered an additional dose of anesthesia. Anesthetic requirements in animals receiving spinal transection (n11) were compared with control animals receiving sham lesion (n9). Results: The cumulative dose necessary to maintain a stable level of anesthesia was significantly lower in transected animals compared with control animals. By about 7 h after spinal cord injury, on average the cumulative dose of urethane was only 1.13 ± 0.14 of the original dose, compared with 1.64 ± 0.19 of the original dose in control animals. Conclusions: Spinal transection immediately decreased anesthetic requirements in rats. To establish whether these results are relevant for patients with spinal cord injury will require further investigation. © 2011 International Spinal Cord Society All rights reserved.