The Effects of Spinal Cord Stimulation on the Spinal Nociceptive Process Evaluated by Cord Dorsum Potential in Cats / 대한마취과학회지

BACKGROUND: The pain-inhibitory effects of spinal cord stimulation (SCS) may be exerted at two alternative or complementary levels, segmentally or supraspinally. However the actual pathways, site of action, and synaptic relays are poorly understood. No data is available which concerns the changes in cord dorsum potential (CDP) associated with a single neuronal level, after SCS. METHODS: SCS was performed in normal and spinalized cats. At the lumbosacral enlargement, CDP and extracellular single cell activity in response to electrical stimulation of Asigma- or C-fiber of the dorsal root or sciatic nerve were recorded. RESULTS: The resulting CDP consisted of characteristic waves of Asigma- and C-fiber with a different time latency. CDP sno significant differences in the amplitude of Asigma- and C-fiber wave between the normal and spinalized cats. In both groups, CDP showed decrease in the amplitude of C-fiber wave. Single cell responses were either increased or decreased after SCS. The C- response changed more marKedly than the A-response in both the normal and spinalized cats. In the bicuculline administered cats, single cell responses increased after SCS, but no change was found in the amplitude of CDP. CONCLUSIONS: The above results might indicate that SCS suppresses C-fiber transmission of nociceptive electrical stimuli via a segmental inhibitory mechanism, and that SCS is more effective in blocKing the transmission of nociceptive electrical stimuli via the C-fiber than Asigma-fiber.

The Effects of Acid-Base Imbalance on the Cisatracurium-Induced Neuromuscular Blockade in the Cat / 대한마취과학회지

BACKGROUND: Cisatracurium is a nondepolarizing muscle relaxant. It less likely release histamine and has better cardiovascular stability. It presumably undergoes pH and temperature- dependent, nonenzymatic chemical process, Hofmann reaction. In vitro studies, Hofmann reaction was enhanced with increasing pH, but, in vivo the influence of acid-base imbalance is not well defined. METHODS: To evaluate the effects of acid-base imbalance on the neuromuscular blockade of cisatracurium in the cat, we induced acid-base imbalance and performed cumulative dose-response studies. RESULTS: ED50 of the cisatracurium was significantly reduced in all groups. Dose-response curves from all acid-base imbalance groups did not have significant differences in slopes. But, all showed shift-to-left when compared with control curve, showing decreased ED50. Duration of action was not affected. Recovery index was significantly changed in respiratory and metabolic alkalosis. CONCLUSIONS: It may be concluded that acid-base imbalance significantly augmented the potency of cisatracurium, but, changes of recovery index in this study may be resulted from systemic instability such as unstable hemodynamic state by the prolonged experiment.

The Changes in Cord Dorsum Potential after Spinal Cord Stimulation / 대한마취과학회지

BACKGROUND: Spinal cord stimulation(SCS) evolved as a direct clinical application of the famous gate-control theory, the idea of activating the central collaterals of large afferent fibers contained in the dorsal column. It is well known that the cord dorsum potential(CDP) evoked by stimulation of dorsal roots or peripheral nerves can be recorded from the cord surface in spinal animals. However, there have been no data about the changes in CDP after SCS. METHODS: Using ball-type electrode, CDP was recorded at the dorsal root entry zone of lumbosacral enlargement in anesthetized cats. The dorsal root was stimulated electrically to activate Adelta-fiber(single pulse of 0.2 ms duration and 1 mA intensity) and C-fiber(single pulse of 0.2 ms duration and 10 mA intensity). Potentials were averaged 10 times and measured before(control) and immediately after, and 10, 20, 30, 40, 50, 60 min after SCS for 20 min. RESULTS: CDP elicited by dorsal root stimulation consisted of the characteristic waves of Adelta-fiber and C-fiber with different time latency. CDP showed significant decrease in the amplitude of C-fiber wave immediately after SCS(75.0+/-8.8%), and 20 min(69.0+/-7.9%), 30 min(75.1+/-4.4%), 40 min(75.4+/-4.4%), 50 min(78.3+/-5.9%), but not 10 min and 60 min, after SCS. However there were no statistically significant decrease in the amplitude of Adelta-fiber wave after SCS. CONCLUSIONS: The above results indicates that SCS suppresses the transmission of nociceptive electrical stimuli via C-fiber, while SCS has little influence on the transmission of electrical nociceptive stimuli via Adelta-fiber.