Henning Andreas Haga1, Andreas Lervik2, Janicke Nordgreen2. 1. Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Norway. Electronic address: andreas.haga@nmbu.no. 2. Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Norway.
Abstract
OBJECTIVE: To investigate motor and cardiovascular responses to dexmedetomidine or fentanyl in isoflurane-anaesthetized pigs. STUDY DESIGN: Experimental, balanced, block randomized, two-group design. ANIMALS: A group of 16 crossbred pigs, 55 ± 8 days (mean ± standard deviation) old. METHODS: Deltoid electromyography (EMG) was recorded during isoflurane anaesthesia. Electrical stimulation using 5, 10, 20 and 40 mA of the distal right thoracic limb elicited a nociceptive withdrawal reflex (NWR), quantified by the area under the curve (AUC) for the simulation intensity versus EMG amplitude response curve. Latency to movement evoked by clamping a claw for maximum 60 seconds was noted. Arterial blood pressure and pulse rate were recorded. Data were sampled at baseline and during dexmedetomidine 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 μg kg-1 hour-1 or fentanyl 5, 10, 20, 40, 80 and 160 μg kg-1 hour-1 infusions. The influence of infusion rate on NWR AUC and spontaneous EMG was analysed using a mixed model, with p < 5%. RESULTS: NWR AUC increased at fentanyl 5 μg kg-1 hour-1 but decreased at fentanyl 40, 80 and 160 μg kg-1 hour-1 and dexmedetomidine 4.0 and 8.0 μg kg-1 hour-1. All pigs at fentanyl 80 μg kg-1 hour-1, and three pigs at dexmedetomidine 8.0 μg kg-1 hour-1 had mechanical latencies greater than 60 seconds. Spontaneous EMG activity increased accompanied by visually evident 'shivering' at fentanyl 5, 10 and 20 μg kg-1 hour-1 but decreased at dexmedetomidine 2, 4 and 8 μg kg-1 hour-1. Clinically relevant effects of increasing infusion rates on blood pressure or pulse rate were not observed. CONCLUSION AND CLINICAL RELEVANCE: If anaesthetic plane or antinociception is evaluated in pigs, response to claw clamping and NWR will not necessarily give uniform results when comparing drugs. If only one method is used, results should be interpreted cautiously.
OBJECTIVE: To investigate motor and cardiovascular responses to dexmedetomidine or fentanyl in isoflurane-anaesthetized pigs. STUDY DESIGN: Experimental, balanced, block randomized, two-group design. ANIMALS: A group of 16 crossbred pigs, 55 ± 8 days (mean ± standard deviation) old. METHODS: Deltoid electromyography (EMG) was recorded during isoflurane anaesthesia. Electrical stimulation using 5, 10, 20 and 40 mA of the distal right thoracic limb elicited a nociceptive withdrawal reflex (NWR), quantified by the area under the curve (AUC) for the simulation intensity versus EMG amplitude response curve. Latency to movement evoked by clamping a claw for maximum 60 seconds was noted. Arterial blood pressure and pulse rate were recorded. Data were sampled at baseline and during dexmedetomidine 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 μg kg-1 hour-1 or fentanyl 5, 10, 20, 40, 80 and 160 μg kg-1 hour-1 infusions. The influence of infusion rate on NWR AUC and spontaneous EMG was analysed using a mixed model, with p < 5%. RESULTS: NWR AUC increased at fentanyl 5 μg kg-1 hour-1 but decreased at fentanyl 40, 80 and 160 μg kg-1 hour-1 and dexmedetomidine 4.0 and 8.0 μg kg-1 hour-1. All pigs at fentanyl 80 μg kg-1 hour-1, and three pigs at dexmedetomidine 8.0 μg kg-1 hour-1 had mechanical latencies greater than 60 seconds. Spontaneous EMG activity increased accompanied by visually evident 'shivering' at fentanyl 5, 10 and 20 μg kg-1 hour-1 but decreased at dexmedetomidine 2, 4 and 8 μg kg-1 hour-1. Clinically relevant effects of increasing infusion rates on blood pressure or pulse rate were not observed. CONCLUSION AND CLINICAL RELEVANCE: If anaesthetic plane or antinociception is evaluated in pigs, response to claw clamping and NWR will not necessarily give uniform results when comparing drugs. If only one method is used, results should be interpreted cautiously.
Authors: Carly Baehr; Christine Robinson; Andrew Kassick; Rajwana Jahan; Valeria Gradinati; Saadyah E Averick; Scott P Runyon; Marco Pravetoni Journal: ACS Omega Date: 2022-05-04