Study design

Prospective experimental trial.

Animals

Forty-eight hybrid male goats weighing 27 ± 2 kg.

Methods

The goats were randomly assigned to six groups: L2.2, epidural lidocaine (2.2 mg kg^?1); L4.4, epidural lidocaine (4.4 mg kg^?1); EA; EA-L1.1, EA with epidural lidocaine (1.1 mg kg^?1); EA-L2.2, EA with epidural lidocaine (2.2 mg kg^?1); and EA-L4.4, EA with epidural lidocaine (4.4 mg kg^?1). EA was administered for 120 minutes. Epidural lidocaine was administered 25 minutes after EA started. Nociceptive thresholds of flank and thigh regions, abdominal muscle tone, mean arterial pressure (MAP), heart rate (HR), respiratory frequency (f_R) and rectal temperature were recorded at 30, 60, 90, 120, 150 and 180 minutes.

Results

Lidocaine dose-dependently increased nociceptive thresholds. There were no differences in nociceptive thresholds between L4.4 and EA from 30 to 120 minutes. The threshold in EA-L2.2 was lower than in EA-L4.4 from 30 to 120 minutes, but higher than in EA-L1.1 from 30 to 150 minutes or in L4.4 from 30 to 180 minutes. The abdominal muscle tone in EA-L2.2 was higher at 30 minutes, but lower at 90 and 120 minutes than at 0 minutes. There were no differences in muscle tone between L4.4 and L2.2 or EA-L4.4, and between any two of the three EA-lidocaine groups from 0 to 180 minutes. The f_R and HR decreased in L4.4 at 60 and 90 minutes compared with 0 minutes. No differences in f_R, HR, MAP and temperature among the groups occurred from 30 to 180 minutes.

Conclusions and clinical relevance

EA combined with 2.2 mg kg^?1 epidural lidocaine provides better antinociceptive effect than 4.4 mg kg^?1 epidural lidocaine alone in goats. EA provided antinociception and allowed a decrease in epidural lidocaine dose.