This study was performed to evaluate Fourier-transformed electroencephalographic (EEG) variables, mean arterial blood pressure (MAP) and pulse rate as nociceptive indicators in isoflurane-anaesthetized horses.
Five standardbred and three Norwegian cold-blooded trotter stallions undergoing castration, aged 24 years, mass 378538 kg were included.
All horses received intravenous (IV) detomidine (10 g kg1 IV) and butorphanol (0.01 mg kg1 IV). Additional detomidine (4 g kg1 IV) was administered in the induction area.
Anaesthesia was induced with ketamine (2.5 mg kg1 IV) and diazepam (40 g kg1 IV), and maintained for 30 minutes with isoflurane (end-tidal concentration of 1.4%) vaporized in oxygen.
The electroencephalogram, MAP and pulse rate were recorded for 15 minutes, beginning 5 minutes before skin incision. Differences between the mean values of recordings taken before, and during surgery were calculated and tested for significant differences using a two-sided Student`s t-test.
Results: A significant rise in MAP and a fall in pulse rate were found. No significant change was found in any EEG variable.
Thus, of the variables evaluated, MAP seems to be the most sensitive and reliable indicator of nociception in isoflurane-anaesthetized horses.
Source: Haga, Henning A & Dolvik, Nils I (2005): Electroencephalographic and cardiovascular variables as nociceptive indicators in isoflurane-anaesthetized horses. In: Veterinary Anaesthesia and Analgesia 32 (3), 128-135.
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