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Physiologic and anesthetic alterations on spinal-sciatic evoked responses in swine
L H Short1, R E Peterson, P D Mongan
1Department of Surgery, Brooke Army Medical Center, Fort Sam Houston, TX 78234-6200.
Anesthesia and Analgesia
|February 1, 1993
Summary
Spinal-sciatic evoked responses (ScER) are affected by temperature and hypotension, but not CO2 levels. Potent inhaled anesthetics significantly decrease ScER amplitude and increase latency, disappearing at 1.0 MAC.
Area of Science:
- Neuroscience
- Anesthesiology
- Spinal Surgery
Background:
- Spinal-sciatic evoked responses (ScER) are crucial for monitoring spinal cord integrity during surgery.
- Understanding physiological variable effects on ScER is vital for accurate intraoperative monitoring.
Purpose of the Study:
- To investigate the impact of hypercarbia, hypocarbia, induced hypotension, and hypothermia on ScER.
- To evaluate the effects of nitrous oxide and potent inhaled anesthetics on ScER.
Main Methods:
- Ten swine underwent induced hypercarbia, hypocarbia, hypotension, and hypothermia while monitoring ScER.
- Twenty-one swine received nitrous oxide followed by incremental doses of potent inhaled anesthetics, with ScER monitored.
Main Results:
- Hypothermia increased ScER latency (r = -0.78), while hypotension decreased amplitude (up to 50% at 30 mm Hg). CO2 variations had no significant effect.
- Nitrous oxide significantly reduced ScER amplitude (43-61%). Potent inhaled anesthetics caused dose-dependent decreases in amplitude and increases in latency, abolishing ScER at 1.0 MAC.
Conclusions:
- Hypothermia and hypotension significantly alter ScER, requiring careful management during spinal surgery.
- Inhaled anesthetics markedly impair ScER, necessitating consideration during intraoperative monitoring interpretation.