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OBJECTIVE: Circulating endotoxin impairs the sympathetic regulation of the cardiovascular system in animals. We studied the changes in the autonomic control of the heart and circulation during septic shock in humans. DESIGN: 12 patients (age 43.0 +/- 6, 17-83 years) were investigated during septic shock (mean duration: 3.5 +/- 0.5 days) and during recovery, fluctuations in R-R interval, invasive arterial pressure (AP) and peripheral arteriolar circulation (PC, photoplethysmography) were evaluated by spectral analysis as a validated noninvasive measure of sympathovagal tone. Apache II score was adopted as the disease severity index. Low frequency components (0.03-0.15 Hz) of the frequency spectra were expressed as relative to the overall variability (LFnu) for each cardiovascular variable. RESULTS: LFnu were low or absent during shock but, in the 10 patients who recovered, increased by the time of discharge (post-shock). R-R LFnu increased from 17 +/- 6 to 47 +/- 9 (p < 0.03), AP LFnu from 6 +/- 3 to 35 +/- 4 (p < 0.02) and PC LFnu from 18 +/- 3 to 66 +/- 4 (p < 0.001). Apache II fell from 23.1 +/- 1, at admission, to 14.8 +/- 1.8 at discharge (p < 0.005). Two patients died showing no LFnu increase. CONCLUSION: Reduced LF components of the variability of cardiovascular signals are characteristic of septic shock, confirming the presence of abnormal autonomic control. Restored sympathetic (LF) modulation seems to be associated with a favourable prognosis.


Journal article


Intensive Care Med

Publication Date





112 - 119


APACHE, Adolescent, Adult, Aged, Aged, 80 and over, Analysis of Variance, Autonomic Nervous System, Blood Circulation, Blood Vessels, Combined Modality Therapy, Electrocardiography, Female, Heart, Humans, Linear Models, Male, Middle Aged, Photoplethysmography, Shock, Septic, Signal Processing, Computer-Assisted