Our data suggest that a short corticotropin test has a good prognostic value and could be helpful in identifying patients with septic shock at high risk for death.

Plasma vasopressin levels are almost always increased at the initial phase of septic shock and decrease afterward. Relative vasopressin deficiency is seen in approximately one-third of late septic shock patients.

The autonomic cardiovascular control was investigated in 10 patients with septic shock, 10 patients with sepsis syndrome, and six tilted healthy subjects. Overall variability, high- and low-frequency components (AUC, HF, and LF, beats/min(2)/Hz or mm Hg(2)/Hz) from heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressures spectra were obtained from 5-min recordings. LF(HR)/HF(HR) and the square root of LF(SBP)/LF(HR) (alpha) were used as indices of sympathovagal interaction and baroreflex control of the heart, respectively. Compared with tilted control subjects and patients with sepsis syndrome, septic shock is characterized by reduction in: (1) HR variability, i.e., decreased AUC(HR) (p = 0.007), LF(HR) (p = 0.002), and LF(HR)/HF(HR) (p = 0.0002); (2) DBP variability, i.e., decreased AUC(DBP) (p = 0.003) and LF(DBP) (p = 0.001), (3) alpha (p = 0.003). In septic shock, LF(HR)/HF(HR), alpha, and LF(DBP) correlated with mean blood pressure (r = 0.67, p = 0.04, r = 0.64, p = 0.03, and r = 0.88, p = 0.0008, respectively), and with plasma norepinephrine levels (r = -0.65, p = 0.03, r = -0.79, p = 0.006, and r = -0.69, p = 0.03, respectively). In conclusion, onset of septic shock is characterized by high concentrations of circulating catecholamines but impaired sympathetic modulation on heart and vessels, suggesting that central autonomic regulatory impairment contributes to circulatory failure.