Power spectral analysis of heart rate variability during helium pneumoperitoneum: The mechanism of increased cardiac sympathetic activity and its clinical significance

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Abstract
Carbon dioxide pneumoperitoneum (PP) is known to induce increased cardiac sympathetic expression. The role of the insufflated gas involved in this mechanism should be elucidated in an attempt to eliminate its possible serious consequences. Twenty-five patients undergoing elective laparoscopic cholecystectomy were prospectively analyzed for cardiac autonomic nervous activity by spectral heart rate variability. In 15 patients, helium was used as CO2 substitution for abdominal insufflation (study group). Four frequency bands of interest were obtained from the power spectrum of R-R intervals, as well as the ratio between the low and high frequency (LF/HF), using the fast Fourier transformation algorithm to characterize the synergy of both autonomic branches during PP. Significantly increased values of the power spectrum related to the LF and VLF bands (from 130 to 377 msec2/Hz and from 145 to 516 msec2/Hz, respectively) were inspected during CO2 PP, as well as increased LF/LH ratio (2.1). Using helium as CO2 substitution has eliminated the significant changes in the power spectrum that reflect increased cardiac sympathetic activity. The elimination of sympathetic predominance by helium PP indicates the central role of CO2 in establishing this phenomena. Considering this information and its other known advantages, helium should be considered for use during prolonged laparoscopic procedures for high-risk patients.