Development of a simple method for differential delivery of volatile anaesthetics to the spinal cord of the rabbit

Emulsified volatile anaesthetics can be easily injected into the circulation and eliminated from blood to lungs. Taking advantage of this unique pharmacokinetics, we aimed to develop a less trauma model for preferential delivery of volatile anaesthetics to the spinal cord with an intact CNS and circulatory system in the rabbit. Sixteen New Zealand White rabbits were randomly assigned to the isoflurane and sevoflurane group. A catheter for delivering emulsified isoflurane (8mg/kg/h) or sevoflurane (12mg/kg/h) to the spinal cord was placed into the descending aorta in all rabbits. The concentration and partial pressure of isoflurane and sevoflurane in the jugular and femoral vein were measured. Our results showed that the partial pressure of isoflurane was 3.91±1.11 mmHg in the jugular vein and 12.61±1.60 mmHg (1.0MAC) in the femoral vein. The partial pressure of sevoflurane was 3.89±1.00 mmHg in the jugular vein and 19.92±1.84mmHg (1.0MAC) in the femoral vein. There was significant difference regarding the partial pressure of isoflurane and sevoflurane between jugular and femoral veins in two groups (both P <0.001). In conclusion, a simple method has been successfully developed to selectively deliver isoflurane and sevoflurane to the spinal cord in the rabbit. Before acting on the brain, 69% isoflurane and 81% sevoflurane were removed from body via lungs. This method can be used to investigate the pharmacological properties of volatile anesthetics.