AUTONOMIC CONTROL OF THE HEART AND PERIPHERAL VESSELS IN HUMAN SEPTICSHOCK

Objective: Circulating endotoxin impairs the sympathetic regulation of the cardiovascular system in animals. We studied the changes in the a utonomic control of the heart and circulation during septic shock in h umans. Design: 12 patients (age 43.0 +/- 6, 17-83 years) were investig ated 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) wer e evaluated by spectral analysis as a validated nonivasive measure of sympathovagal tone. Apache II score was adopted as the disease severit y index. Low frequency components (0.03 - 0.15 Hz) of the frequency sp ectra 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 fr om 18 +/- 3 to 66 +/- 4 (p < 0.001). Apache II fell from 23.1 +/- 1, a t admission, to 14.8 +/- 1.8 at discharge (p < 0.005). Two patients di ed showing no LFnu increase. Conclusion: Reduced LF components of the variability of cardiovascular signals are characteristic of septic sho ck, confirming the presence of abnormal autonomic control. Restored sy mpathetic (LF) modulation seems to be associated with a favourable pro gnosis.