The Effects Of Spinal Cord Transection And Lidocaine Epidural Anesthesia On Propofol Requirement In Rats

Objective To investigate the effects of spinal cord transaction on sedation of propofol in rats and probe into its possible mechanism.Methods Forty-five healthy adult female Sprague-Dawley (SD) rats were selected. Forty-five female Sprague-Dawley (SD) rats were randomly assigned to three groups: group A (n=15) transection group; group B (n=15) sham operation group and group C (n=15) control group. The rats in group A received spinal cord transection, of which 5 were excluded and 10 were included. The spinal cord of the rats in group B was exposed only, but not injured, of which 2 were excluded, and 13 were included in this experiment. The rats in group C did not receive any operation, and 15 were included. After intravenous infusion of propofol, the dosage of propofol required to ablate the eyelid reflex was compared between three groups.Results The dose of propofol required to ablate the eyelid reflex were significantly decreased with sham operation group and control group versus transaction group from (11.2±1.1 mg/kg) and (10.8±1.1mg/kg) to (6.3±0.9 mg/kg) (P < 0.0001), the onset time was from (494±46 s) and (465±51 s) to (324±52 s) (P < 0.01). No significant difference was found in the dose of propofol required and time between sham operation group and control group (P >0.05).Conclusion Spinal cord transection can reduce propofol requirement to ablate the eyelid reflex in rats. Most speculated mechanism for sedation during Spinal cord transection is the indirect central effect of spinal deafferentation Objective To investigate the effects of epidural lidocaine block on sedation of propofol in rats and probe into its possible mechanism.Methods Thirty Sprague-Dawley (SD) rats were included in this study. After intrathecal catheter placement individually, twenty-four rats were randomly assigned to one of three groups: HL group (n=8), LL group (n=8), Normal saline group (n=8); the other eight rats were assigned into Control group (n=8). The rat in three groups respectively received 80μl of 2% lidocaine, 40μl of 2% lidocaine, or 60μl of normal saline intrathecal, intravenous infusion of propofol started at 10 minutes after intrathecal injection; Control group only received intravenous infusion of propofol. The propofol requirements to ablate the eyelid reflex were determined and compared. The level of sensory block was assessed with pinch stimulation and compared spinal anesthesia level in HL group and LL group.Results The dose of propofol required to ablate the eyelid reflex in HL group (7.1±0.8) mg/kg and LL group (8.2±1.0) mg/kg were significantly decreased comparing with intrathecally administered normal saline group (10.3±1.1) mg/kg (P < 0.01). No significant difference was found in the dose of propofol required between the normal saline group and control group(10.4±1.1)mg/kg. The dose of propofol required to ablate the eyelid reflex were significantly decreased with LL group versus HL group (P < 0.05). Spinal anesthesia level of rats in HL group and LL group were (0.8±0.7) cm and (2.4±0.8) cm below xiphoid process, respectively.Conclusion Epidural lidocaine block can reduce propofol requirement to ablate the eyelid reflex in rats. The level of block segments was correlated with the level of sedation.