Abstract
BackgroundHeart rate variability (HRV) provides information about autonomic nervous system (ANS) activity and is therefore a possible tool with which to assess anaesthetic depth. The aim of the present study was to evaluate the effects of isoflurane, remifentanil and dexmedetomidine on HRV before and after nociceptive stimulation at different anaesthetic depths.Seven healthy domestic short-hair cats were used, and each cat was anaesthetized three times – group I with isoflurane alone, group IR with isoflurane and a constant rate infusion (CRI) of remifentanil (18 μg/kg/h), and group ID with isoflurane and a CRI of dexmedetomidine (3 μg/kg/h). Minimum alveolar concentration (MAC) values were determined via electrical supramaximal nociceptive stimulation for each treatment group. Nociceptive stimulation was repeated at 3 different MAC multiples (0.75, 1.0 and 1.5 MAC), and electrocardiographic recordings were performed for 3 min before and after stimulation. Only the 1 min epochs were used for further statistical analysis. Electrocardiographic data were exported for offline HRV analysis.ResultsThe mean isoflurane MAC ± standard deviation (SD) was 1.83 ± 0.22 vol% in group I, 1.65 ± 0.13 vol% in group IR and 0.82 ± 0.20 vol% in group ID. Nociception was indicated by several HRV parameters, however, with high variability between treatments. The best correlation with MAC was found for the SD of heart rate (STD HR) in group I (rs = − 0.76, p = 0.0001, r2 = 0.46). STD HR was also able to distinguish 0.75 MAC from 1.5 MAC and 1.0 MAC from 1.5 MAC in group I, as well as 0.75 MAC from 1.5 MAC in group ID.ConclusionsThe choice of anaesthetic protocol influences the HRV parameters in cats. Frequency domain parameters respond to nociception at lower MAC levels. The STD HR has the potential to provide additional information for the assessment of anaesthetic depth in isoflurane-anaesthetized cats. The utility of HRV analysis for the assessment of anaesthetic depth in cats is still questionable.
Highlights
Heart rate variability (HRV) provides information about autonomic nervous system (ANS) activity and is a possible tool with which to assess anaesthetic depth
Time domain parameters such as STD heart rate (HR), the root mean square of successive RR interval differences (RMSSD) and the percentage of successive RR intervals that differ by more than 50 ms provide information about beat-tobeat HRV, whereas frequency domain parameters such as high frequency (HF), low frequency (LF) and very low frequency (VLF) are able to show the power distributions of different frequency ranges as they are derived from spectral analysis [3]
One cat was excluded from group ID due to the development of ongoing 2nd degree atrioventricular blocks after the administration of dexmedetomidine
Summary
Heart rate variability (HRV) provides information about autonomic nervous system (ANS) activity and is a possible tool with which to assess anaesthetic depth. The aim of the present study was to evaluate the effects of isoflurane, remifentanil and dexmedetomidine on HRV before and after nociceptive stimulation at different anaesthetic depths. Measurement of heart rate variability (HRV) provides information in terms of evaluation of the autonomic nervous system (ANS) and the balance of sympathetic and parasympathetic activity [1, 2]. HRV can be analysed by time and frequency domain parameters Time domain parameters such as STD HR, the root mean square of successive RR interval differences (RMSSD) and the percentage of successive RR intervals that differ by more than 50 ms (pNN50) provide information about beat-tobeat HRV, whereas frequency domain parameters such as high frequency (HF), low frequency (LF) and very low frequency (VLF) are able to show the power distributions of different frequency ranges as they are derived from spectral analysis [3]. The LF/HF ratio is important for the interpretation of the sympathovagal balance
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