Effects of meperidine or saline on thermal, mechanical and electrical nociceptive thresholds in cats.
OBJECTIVE
To measure cutaneous electrical nociceptive thresholds in relation to known thermal and mechanical stimulation for nociceptive threshold detection in cats.


METHODS
Prospective, blinded, randomized cross-over study with 1-week washout interval.


METHODS
Eight adult cats [bodyweight 5.1 +/- 1.8 kg (mean + SD)].


METHODS
Mechanical nociceptive thresholds were tested using a step-wise manual inflation of a modified blood pressure bladder attached to the cat's thoracic limb. Thermal nociceptive thresholds were measured by increasing the temperature of a probe placed on the thorax. The electrical nociceptive threshold was tested using an escalating current from a constant current generator passed between electrodes placed on the thoracic region. A positive response (threshold) was recorded when cats displayed any or all of the following behaviors: leg shake, head turn, avoidance, or vocalization. Four baseline readings were performed before intramuscular injection of meperidine (5 mg kg(-1)) or an equal volume of saline. Threshold recordings with each modality were made at 15, 30, 45, 60, 90, and 120 minutes post-injection. Data were analyzed using ANOVA and paired t-tests (significance at p < 0.05).


RESULTS
There were no significant changes in thermal, mechanical, or electrical thresholds after saline. Thermal thresholds increased at 15-60 minutes (p < 0.01) and mechanical threshold increased at 30 and 45 minutes after meperidine (p < 0.05). Maximum thermal threshold was +4.1 +/- 0.3 degrees C above baseline at 15 minutes while maximum mechanical threshold was 296 +/- 265 mmHg above baseline at 30 minutes after meperidine. Electrical thresholds following meperidine were not significantly different than baseline (p > 0.05). Thermal and electrical thresholds after meperidine were significantly higher than saline at 30 and 45 minutes (p < 0.05), and at 120 minutes (p < 0.05), respectively. Mechanical thresholds were significantly higher than saline treatment at 30 minutes (p <or= 0.05).


CONCLUSIONS
Electrical stimulation did not detect meperidine analgesia whereas both thermal and mechanical thresholds changed after meperidine administration in cats.
Millette
Valerie M
VM
Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Steagall
Paulo V M
PV
Duke-Novakovski
Tanya
T
Livingston
Alex J
AJ
D000818:Animals; D002415:Cats; D004558:Electric Stimulation / Q000009:adverse effects*; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects*; D008297:Male; D008614:Meperidine / Q000494:pharmacology*; D010146:Pain / Q000188:drug therapy / Q000662:veterinary*; D011312:Pressure / Q000009:adverse effects*
D008614:Meperidine