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Anesth Analg 2006;103:1453-1458
© 2006 International Anesthesia Research Society
doi: 10.1213/01.ane.0000247732.33602.f5

ANESTHETIC PHARMACOLOGY

Isoflurane and Propofol Have Similar Effects on Spinal Neuronal Windup at Concentrations that Block Movement

Kevin P. Ng, MD, and Joseph F. Antognini, MD

From the Department of Anesthesiology and Pain Medicine, University of California, Davis, California.

BACKGROUND: We investigated the actions of isoflurane and propofol on neuronal windup in the spinal cord of intact rats. We hypothesized that propofol would depress windup more than isoflurane.

METHODS: In a cross-over design, rats received 0.8 and 1.2 minimum alveolar concentration (MAC) isoflurane and 0.8 and 1.2 ED50 (effective dose50%) of propofol, as recordings were made from single units in the lumbar cord (n = 13). Electrical stimuli were applied (20 stimuli at 0.1, 1, and 3 Hz). Neuronal responses were analyzed for those occurring in the C-fiber range (100–400 ms after each stimulus), combined C-fiber and afterdischarge range (100–1000 ms) and the 100–333 ms range for the 3 Hz stimuli. Absolute windup was also calculated (the sum of action potentials for 20 stimuli – 20 x response to the first stimulus).

RESULTS: At 1 Hz, total action potentials (mean, standard error) summed across the 20 stimuli (100–1000 ms range) were 571 ± 106 and 742 ± 214 for isoflurane (at 0.8 and 1.2 MAC) and 586 ± 148 and 641 ± 143 for propofol (at 0.8 and 1.2 ED50), respectively (P = NS); corresponding values for the 0.1 Hz stimuli were 345 ± 104, 370 ± 108, 430 ± 86, and 403 ± 106 (P = NS), and for the 3 Hz stimuli (100–333 ms range) were 266 ± 66, 333 ± 76, 343 ± 85, and 252 ± 72 (P = NS). Absolute windup in the 100–1000 ms range was greater for 1.2 MAC isoflurane at 1 Hz (445 ± 82, P < 0.01), when compared with absolute windup at 0.8 MAC isoflurane and 0.8 and 1.2 ED50 propofol (232 ± 31, 88 ± 65, and 210 ± 41, respectively).

CONCLUSIONS: These data suggest that isoflurane and propofol have similar effects on neuronal windup in the spinal cord, although there was enhanced absolute windup at 1.2 MAC isoflurane for the 1 Hz stimulus.






Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press
Copyright © 2006 by the International Anesthesia Research Society.