Electrocardiographic indicators of excitability in horses for predicting recovery quality after general anaesthesia.

Abstract Objective To determine whether preoperative electrocardiographic measurements linked to sympathetic nervous activity could be used to predict recovery quality after general anaesthesia in horses. Study design Prospective, clinical study. Animals Eighteen adult client-owned horses. Methods The electrocardiogram (ECG) was recorded presurgery in horses under three standard conditions: stabled unattended; with a groom whilst being led along a standard course; alone in the induction box. After surgery, each animal's recovery quality was scored by eight experienced anaesthetists or technicians using Donaldson's scoring system (2000). The digitized ECG recordings were analyzed for T-wave morphology, mean heart rate (HR), HR variability (HRV) and HRV derivatives including mean R-R interval, standard deviation of normal intervals (SDNN) and the root mean square of successive intervals (RMSSD), low (LF) and high frequency (HF) activity and the LF/HF ratio in both fast Fourier transformed and autoregressive spectra. Correlations between ECG variables and recovery score were examined using Spearman's rank correlation. Results There was no significant correlation between preanaesthetic ECG measurements and recovery quality. Conclusions Predictions of recovery quality after general anaesthesia in horses cannot be based on preanaesthetic ECG variables. Clinical relevance Measures other than those based on the ECG should be investigated as predictors of recovery quality.