A new method to evaluate cardiovascular response in anesthetized rats. Hypertension after variable intensity, brief electrical stimuli.
To establish and standardize a nociceptive response in anesthetized rats, the hypertensive responses to defined electrical and mechanical stimuli were studied. Rats (n = 7) were given etomidate, 3.8 mg/kg/hr intravenously (i.v.) 2 hr following carotid artery and jugular vein cannulation. At 15 min after beginning the infusion, four types of noxious stimuli were administered sequentially at 1-min intervals (14 stimuli total): Type 1: Square electrical waves, 125 cps, 1.6 msec, 2-sec train duration, varying current from 0.4 to 12 mA (11 stimuli); Type 2: A single 10-mA electrical stimulus, 5-sec train duration; Type 3: Tail clamping; and, Type 4: Skin incision. After each stimulus, maximum change in systolic blood pressure (delta SBP) was measured. delta SBP after the most intense stimuli was as follows: Type 1 (12 mA, 2 sec), 32.1 +/- 2.14 mmHg; Type 2 (10 mA 5 sec), 42.9 +/- 2.4 mmHg; Type 3 (tail-clamping), 34.3 +/- 3.3 mmHg; Type 4 (skin incision), 14.2 +/- 2.8 mmHg. For the multiple Type-2 stimuli, a relationship between current and delta SBP was present. The authors believe that characterized graded electrical stimulation will allow a more quantitative evaluation of the hypertensive response to noxious stimuli in etomidate anesthetized rats, as compared to observing a single response to a single stimulus. The characterization of the electrical stimulation by amplitude, frequency, and wave form makes research work on nociception under anesthesia easily reproducible.
Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center, Dallas.
F G
FG
Zavisca
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Y
David
Y J
YJ
Kao
L H
LH
Cronau
T H
TH
Stanley
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T
David
D000758:Anesthesia; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004558:Electric Stimulation; D005045:Etomidate / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D005045:Etomidate