TY - JOUR
T1 - Carbon dioxide depresses the F wave by a central, not peripheral, mechanism during isoflurane anesthesia
AU - Dominguez, Carmen
AU - Carstens, Earl
AU - Antognini, Joseph F.
PY - 2005/2
Y1 - 2005/2
N2 - Carbon dioxide (CO2) has anesthetic properties and has been reported to depress the F wave of the evoked electromyogram; the F wave is thought to reflect motoneuron excitability. Anesthetics such as isoflurane also depress the F wave. Because CO2 can depress muscle contractile function, as well as spinal cord neurons, it is unclear whether CO2 depresses the F wave via a central or peripheral mechanism. We anesthetized rabbits with isoflurane (1.4%) and prepared for hindlimb bypass (with a membrane oxygenator) whereby the partial pressures of CO2 in the hindlimb muscle and torso could be independently adjusted. The F wave was recorded from the hindlimb plantar muscles when the CO2 was normal to the hindlimb and torso, and when it was increased (to ≈90 mm Hg) in the hindlimb, the torso, or both. Increasing the CO2 to just the hindlimb had no significant effect on the F-wave amplitude, but increasing the CO2 to the torso depressed the F wave to 52% ± 32% of control; adding CO 2 to the hindlimb during torso hypercarbia did not result in any additional depression of the F wave. CO2 depressed the F wave via a central, not peripheral, mechanism, although the precise mechanism is unknown.
AB - Carbon dioxide (CO2) has anesthetic properties and has been reported to depress the F wave of the evoked electromyogram; the F wave is thought to reflect motoneuron excitability. Anesthetics such as isoflurane also depress the F wave. Because CO2 can depress muscle contractile function, as well as spinal cord neurons, it is unclear whether CO2 depresses the F wave via a central or peripheral mechanism. We anesthetized rabbits with isoflurane (1.4%) and prepared for hindlimb bypass (with a membrane oxygenator) whereby the partial pressures of CO2 in the hindlimb muscle and torso could be independently adjusted. The F wave was recorded from the hindlimb plantar muscles when the CO2 was normal to the hindlimb and torso, and when it was increased (to ≈90 mm Hg) in the hindlimb, the torso, or both. Increasing the CO2 to just the hindlimb had no significant effect on the F-wave amplitude, but increasing the CO2 to the torso depressed the F wave to 52% ± 32% of control; adding CO 2 to the hindlimb during torso hypercarbia did not result in any additional depression of the F wave. CO2 depressed the F wave via a central, not peripheral, mechanism, although the precise mechanism is unknown.
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U2 - 10.1213/01.ANE.0000141677.16224.AD
DO - 10.1213/01.ANE.0000141677.16224.AD
M3 - Article
C2 - 15673865
AN - SCOPUS:12844275933
VL - 100
SP - 398
EP - 403
JO - Anesthesia and Analgesia
JF - Anesthesia and Analgesia
SN - 0003-2999
IS - 2
ER -