Changes in plasma concentrations of vasoactive neuropeptides in patients with sepsis and septic shock

The aim of this work was to study the hypothesis that the release of vasoactive neuropeptides may be related to the hemodynamic changes and severity of disease in human sepsis and septic shock. Twenty-two patients diagnosed with sepsis and treated in medical wards with standard supportive therapy and twenty patients admitted to a medical intensive care unit because of septic shock were studied Twenty healthy volunteers in a similar age range were enrolled as control group. Blood samples were taken at onset and every 12 hours on the following day after hospital admission to measure plasma concentrations of calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and substance P (SP). Clinical and biochemical variables were measured simultaneously. The Acute Physiology and Chronic Health Evaluation (APACHE) II score was calculated on admission. From the day of admission, septic shock patients had significantly higher plasma CGRP-like immunoreactivity levels than patients with sepsis, as well as both groups of patients compared to control subjects. Plasma NPY-like immunoreactivity levels in patients with either sepsis or septic shock was significantly increased, and plasma SP-like immunoreactivity levels significantly reduced compared to those in controls. Plasma CGRP levels at study entry correlated with the APACHE II score (r = 0.71, p < 0.01), as well as with the cardiac index (r = 0.61, p < 0.05) and systemic vascular resistance index (r = -0.62, p < 0.05). Our data suggest that both CGRP and NPY, but not SP, are increasedly released into the circulation during the development of human sepsis and septic shock. In patients with sepsis the vasoconstriction mediated by the release of NPY appears to counterbalance the vasodilatory effect of CGRP. In septic shock patients, however, the release of NPY might be inadequately low to overcome the widespread CGRP-induced vasodilation.