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Spinal conduction block by intrathecal ketamine in dogs
1Department of Anesthesiology and Critical Care Medicine, Gifu University School of Medicine, Gifu City, Japan. iida@cc.gifu-u.ac.jp
Anesthesia and Analgesia
|July 1, 1997
Summary
Intrathecal ketamine provides pain relief by blocking nerve signals in the spinal cord. This study in dogs shows intrathecal ketamine, unlike I.V. administration, significantly impacts spinal evoked potentials, suggesting axonal conduction block contributes to its analgesic effects.
Area of Science:
- Neuroscience
- Pharmacology
- Anesthesiology
Background:
- Ketamine is used for anesthesia and spinal pain relief.
- The exact mechanisms of intrathecal ketamine analgesia require further elucidation.
Purpose of the Study:
- To investigate the mechanisms of intrathecal (I.T.) ketamine analgesia.
- To compare the effects of intravenous (I.V.) and I.T. ketamine on intraspinal evoked potentials (ISEPs).
Main Methods:
- 28 pentobarbital-anesthetized dogs were used.
- Bipolar extradural electrodes recorded descending ISEPs (Waves I and II) at cervical and lumbar spinal cord regions.
- Effects of I.V. and I.T. ketamine on ISEP amplitude and latency were analyzed.
Main Results:
- I.V. ketamine (2 and 10 mg/kg) did not affect Wave I. High-dose I.V. ketamine decreased Wave II amplitude.
- I.T. ketamine (1 and 5 mg/kg) caused dose-dependent decreases in Wave I and II amplitudes.
- I.T. ketamine also dose-dependently prolonged Wave I and II latencies.
Conclusions:
- I.T. ketamine's effects on ISEPs suggest axonal conduction block.
- Axonal conduction block may be a key mechanism underlying I.T. ketamine's analgesic properties.