Quantitative assessment of nociceptive processes in conscious dogs by use of the nociceptive withdrawal reflex

• DOI: 10.2460/ajvr.67.5.882
• Publication Date: 2006-05-01T16:31:51Z
• Authors: Alessandra Bergadano; Ole K. Andersen; Lars Arendt-Nielsen; Urs Schatzmann; Claudia Spadavecchia
• Keywords: Male; Pain Threshold; 0403 veterinary science; Dogs; Consciousness; Reflex; Animals; Pain; 04 agricultural and veterinary sciences; Pain Measurement

Abstract Objective—To investigate the feasibility of evoking the nociceptive withdrawal reflex (NWR) from foreand hind limbs in conscious dogs, score stimulusassociated behavioral responses, and assess the canine NWR response to suprathreshold stimulations. Animals—8 adult Beagles. Procedure—Surface electromyograms evoked by transcutaneous electrical stimulation of ulnaris and digital plantar nerves were recorded from the deltoideus, cleidobrachialis, biceps femoris, and tibialis cranialis muscles. Train-of-five pulses (stimulustrain) were used; reflex threshold (It train) was determined, and recruitment curves were obtained at 1.2, 1.5, and 2 × It train. Additionally, a single pulse (stimulussingle) was given at 1, 1.2, 1.5, 2, and 3 × It train. Latency and amplitude of NWRs were analyzed. Severity of behavioral reactions was subjectively scored. Results—Fore- and hind limb It train values (median; 25% to 75% interquartile range) were 2.5 mA (2.0 to 3.6 mA) and 2.1 mA (1.7 to 2.9 mA), respectively. At It train, NWR latencies in the deltoideus, cleidobrachialis, biceps femoris, and cranial tibialis muscles were not significantly different (19.6 milliseconds [17.1 to 20.5 milliseconds], 19.5 milliseconds [18.1 to 20.7 milliseconds], 20.5 milliseconds [14.7 to 26.4 milliseconds], and 24.4 milliseconds [17.1 to 40.5 milliseconds], respectively). Latencies obtained with stimulustrain and stimulussingle were similar. With increasing stimulation intensities, NWR amplitude increased and correlated positively with behavioral scores. Conclusions and Clinical Relevance—In dogs, the NWR can be evoked from limbs and correlates with behavioral reactions. Results suggest that NWR evaluation may enable quantification of nociceptive system excitability and efficacy of analgesics in individual dogs.