Artikel
Investigation of the relationship between stimulation current in continuous intraoperative neuromonitoring (CIONM) during thyroid surgery and autonomous nervous system activity
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Veröffentlicht: | 26. April 2013 |
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Gliederung
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Intrduction: Continuous intraoperative neuromonitoring (CIONM) via vagus nerve stimulation (VNS) during thyroid surgery has been shown to influence the autonomous nervous system (ANS). Since no hemodynamic changes or significant changes in cytokine release have been shown, the technology is considered clinically safe. However, stimulation parameters during CIONM have not been standardized and widely vary in practical application. Our aim was to examine whether a relationship exists between stimulation current and ANS activity.
Material and methods: Data from our clinical CIONM study (n=22) were retrospectively analyzed. Heart rate variability analysis (HRVA) in the spectral domain was used to quantify cardiac ANS activity. ANS activity was compared for stimulation currents between 1 and 5 mA. An in-vivo experiment on the porcine model was conducted in order to evaluate changes in ANS activity and heart rate using stimulation currents between 1 and 20 mA at stimulation rate of 2 to 30 pulses per second.
Results: With increased stimulation current, an increase in parasympathetic acticity was observed during clinical CIONM between low and high stimulation current (LF/HF ratio 0.35 vs. 0.5, p<0.05). Experimental data showed that upon increasing the stimulation current above 10 mA, overall ANS activity increased while a sympathetic predominance occured. At higher stimulation rates (>10pps), a significant increase in heart rate and further increase in ANS activity was observed.
Conclusion: The influence of CIONM on ANS activity increases with higher stimulation currents. Our experimental data indicate that at currents above 10 mA and higher stimulation rates, a systemic stress reaction of the organism ensues which might have implications on the safety of vagus stimulation.