[Effect of noxious stimulation on regional distribution of propofol in canine spinal cord]

To observe the regional distribution of propofol in canine spinal cord under noxious stimulation.

Twelve healthy hybrid dogs (12-18 months old, weighing 10-12 kg) were randomly divided into control group (n=6) and stimulation group (n=6). All the dogs were anesthetized with a single bolus dose of propofol (7 mg/kg) in 15 seconds followed by propofol infusion at a constant rate of 70 mg/kg/h via the great saphenous vein of the right posterior limb. In the stimulation group, the tails of the dogs were clamped for 5 min after 45 min of propofol infusion. Blood samples were taken from the internal carotid artery and internal jugular vein at 50 min after propofol infusion to detect plasma propofol concentrations by high-pressure liquid chromatography (HPLC). The dogs were then immediately sacrificed by decapitation and the frontal horn, posterior horn, intermediate zone, frontal funiculus, posterior funiculus and lateral funiculus of the spinal cord were dissected for determination of propol content by HPLC.

The plasma concentrations of propofol in the internal carotid artery and internal jugular vein were 5.07-/+0.23 and 5.03-/+0.10 microg/ml in the stimulation group, respectively showing no significant differences from those in the control group (5.09-/+0.03 and 5.08-/+0.03 microg/ml, P>0.05). In the control group, the propofol concentration was 5.09-/+0.08 microg/g in the frontal horm, 5.10-/+0.08 microg/g in the posterior horn, 5.05-/+0.19 microg/g in the intermediate zone, 5.06-/+0.14 microg/g in the frontal funiculus, 5.06-/+0.15 microg/g in the posterior funiculus and 5.06-/+0.41 microg/g in the lateral funiculus, showing no significant differences (P>0.05). The propofol concentrations in the frontal horn (7.65-/+0.47 microg/g) and posterior funiculus (7.06-/+0.82 microg/g) in the stimulation group were significantly higher than those in the other spinal cord tissues (P<0.05) and those in the control group (P<0.05).

At 50 min after intravenous injection of propofol at a constant rate of 70 mg/kg/h, plasma propofol concentrations in the internal carotid artery and internal jugular vein reaches equilibrium with a balanced distribution in all the spinal cord regions. Propofol concentration can be higher in the frontal horn and posterior funiculus under noxious stimulation.