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October 16-20, 2010 San Diego, CA Home Abstract Archive Search Abstracts 2010 Session Grid 2010 Meeting Website Policy Statements ASA Website Feedback 
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A-576
2003 |
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| Evaluation of a Device To Speed Emergence from Inhaled Anesthetic | ||||||||||||||||||||
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Derek Sakata, M.D., Joseph Orr, Ph.D., Dwayne Westenskow, Ph.D. Anesthesiology, University of Utah, Salt Lake City, Utah. |
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Introduction. Emergence from inhaled anesthesia is more rapid with hyperventilation to remove volatile agent from the lungs and elevated cerebral blood flow to remove anesthetic agent from the brain. Hypercapnia can elevate cerebral blood flow and speed emergence. Hyperventilation, and resulting hypocapnia, leads to decreased cerebral blood flow and decreased clearance of anesthetic from the brain. We tested a simple device, which rapidly removes inhaled anesthetics from the breathing circuit and also maintains slight hypercapnia during hyperventilation. The device employs an anesthetic absorber filled with activated charcoal placed in the airway to rapidly absorb anesthetic agent and a partial rebreathing volume placed between the Y-piece and the endo-tracheal tube to maintain elevated end tidal CO2 during hyperventilation. Rebreathing allows hyperventilation while preventing hypocapnia, the absorber scrubs anesthetic vapors to prevent inhalation of anesthetic from the rebreathed volume. Methods We compared emergence times from isoflurane anesthesia with and without the rebreathing device in 5 pigs. Prior to emergence, each animal was anesthetized at approximately 2 MAC for at least 6 hours. During emergence, inspired and end-tidal isoflurane concentration, end tidal CO2, bispectral index (BIS™), and blood pressure were recorded along with time to return of spontaneous breathing, purposeful movement of multiple limbs, and end tidal isoflurane less than 0.5 MAC. The protocol included four emergence time measurements in each animal including a comparison between hyperventilation and rebreathing and a comparison between normal ventilation and rebreathing. The order of testing was randomized to minimize the influence of prior tests on subsequent test results. Results The table below shows the average times after the vaporizer was turned off until each of the events were observed. Average time to spontaneous breathing was 6.1 minutes less using the rebreathing device when compared to normal ventilation and 7.0 minutes less when compared to hyperventilation. Spontaneous breathing was not observed prior to purposeful movement in any animal when hyperventilation was used. Time to purposeful movement was 6.9 minutes less when using rebreathing than when normal ventilation was used and 4.0 minutes less when compared to hyperventilation. The time to reach end-tidal agent concentration less than 0.5 MAC was 7.4 minutes less using the rebreathing device compared to normal ventilation and 1.5 minutes less when compared to hyperventilation. Discussion To achieve rapid emergence from volatile anesthetic there is a trade-off between hyperventilation for rapid removal of volatile anesthetic from the lungs, and hypoventilation to maintain elevated blood flow to the brain through normocapnia or slight hypercapnia. A rebreathing device appears to allow the clinician to simultaneously achieve both goals during the reversal process. Anesthesiology 2003; 99: A576 |
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