Effects of ketamine on the balance of ions Ca2+, Mg2+, Cu2+ and Zn2+ in the ischemia-reperfusion affected spinal cord tissues in rabbits.

To test the effects of ketamine on metal ion balance in the spinal cord tissues after ischemic reperfusion (I/R), 24 white adult Japanese rabbits were randomly assigned to sham operation group, I/R group or ketamine-treated I/R group. Spinal cord injuries in I/R group and ketamine-treated I/R group were induced by aortic occlusions. Rabbits in ketamine-treated I/R group were intravenously infused 10 mg/kg ketamine twice: once at 10 min before aortic clamping and once at the onset of reperfusion. Post-operative neurological functions and concentrations of ions Ca2+, Mg2+, Cu2+ and Zn2+ in the spinal cord were assessed. Compared with the sham operation group, rabbits in the I/R group showed significantly worsened neurological functions as scored with the modified Tarlov criteria and altered concentrations of ions Ca2+, Mg2+, Cu2+ and Zn2+. These unfavorable changes were significantly reversed in the ketamine-treated I/R group, suggesting that the potent protective effects of ketamine against the I/R-induced spinal cord injuries may be due to its ability to maintain ion balance in the I/R affected tissues.

Protective effect of ketamine on ischemic spinal cord injury in rabbits.

We tested our hypothesis that a commonly used anesthetic, ketamine, may offer benefits to protect animals from spinal cord injury, using the ischemia/reperfusion (I/R) injury rabbit model in a randomized controlled study. We used 24 white adult Japanese rabbits from the animal facility at the Medical College of Wuhan University. The rabbits were randomly assigned to one of three groups, eight rabbits per group: group I, sham-operation group; group II, I/R group; group III, I/R with ketamine treatment group. Spinal cord ischemia was induced by infrarenal aortic cross-clamp for 45 min in group II and group III, and ketamine was intravenously infused at 10 mg/kg in 15 mL 0.9% sodium chloride at a speed of 1.5 mL/min to animals in group III, once at 10 min before aortic clamping and once at the onset of reperfusion. Postoperative neurological function, electromyography of rear limbs, histopathology, malondialdehyde (MDA) levels, and superoxide dismutase (SOD) activity in the spinal cord were assessed in all animals. Compared with the control group I, group II showed significant I/R injury-induced changes in neurological function scores, histopathology, and electromyography (p < 0.01). However, group III with ketamine treatment significantly reversed the changes in all these parameters (p < 0.01). At the same time, the I/R-induced increase in MDA content observed in group II was also significantly reduced in group III (p < 0.01), and the I/R-induced decreases in SOD activity were also significantly prevented in group III (p < 0.01). After ketamine treatment, all parameters examined in group III were not significantly different from those obtained in group I. Ketamine showed potent protective effects against spinal cord I/R injury in the rabbit model and protected loss of antioxidant activity in spinal cord tissues.

Effect of repetitive ischemic preconditioning on spinal cord ischemia in a rabbit model.

A completely randomized controlled study based on a rabbit model was designed to study the effect of repetitive ischemic preconditioning (IPC) on a spinal cord ischemic reperfusion injury. Twenty four white adult Japanese rabbits were randomly assigned to one of the 3 groups (n = 8 per group): Group I: sham-operation group, Group II: ischemic reperfusion group, and, Group III: IPC group. Spinal cord ischemia was induced by infra-renal aortic cross-clamp for 45 min in Group II. Before 45 min ischemia, the rabbits in Group III underwent four cycles of IPC (5 min of ischemia followed by 5 min of reperfusion). Post-operative neurological function, electromyography (EMG) of rear limbs, and spinal cord histopathological changes were measured. The concentrations of calcium, magnesium, copper, and zinc in spinal cord were measured in the 7th day. The neurological function and histopathological changes in Group II were significantly different from those in Group I or Group III (P < 0.05 or 0.01). There was a more significant change of EMG in Group II than that in Group III (P < 0.05). The concentrations of calcium and copper in Group II were significantly higher (P < 0.05 or 0.01), but magnesium and zinc were significantly lower (P < 0.05) than those in Group I. Calcium and copper in Group II were significantly higher (P < 0.05), but zinc was significantly lower (P < 0.01) than those in Group III. In conclusion, repetitive IPC can protect rabbit spinal cord from ischemic reperfusion injury in a timely manner, which is associated with corrections of imbalance of calcium, magnesium, copper, and zinc in the ischemic region.