Surgery and sepsis increase somatostatin-like immunoreactivity in the human plasma

We have previously shown in animals that somatostatin released from capsaicin-sensitive afferents in response to inflammation and tissue damage exerts systemic anti-nociceptive and anti-inflammatory actions. Since peptidergic sensory innervation of the airways and the joints are particularly dense, we aimed at investigating the alterations of plasma somatostatin-like immunoreactivity (SST-LI) in response to thoracic and orthopedic surgery, as well as sepsis. Thoracotomy, video-assisted thoracoscopy, hip and knee endoprosthesis were performed under general anesthesia. Blood was taken before, during and after the surgical procedures, as well as at admission and every consecutive morning from septic patients receiving exclusively total parenteral nutrition. SST-LI was determined from the plasma with specific and sensitive radioimmunoassay developed in our laboratory. Plasma SST-LI in healthy volunteers and preoperatively was 8-12fmol/ml. Both thoracotomy and thoracoscopy significantly increased SST-LI by 55-60% at the end of the procedures when the thoracic cavity and the skin were closed. Hip endoprosthesis implantation elevated SST-LI by 30% after skin incision, which increased further to 55% by the time the surgery was completed. In contrast, knee operations performed under tourniquet did not alter SST-LI in the systemic circulation. SST-LI was almost 3-fold higher in the plasma of septic patients than in healthy volunteers. This human study revealed that thoracic/hip surgery and sepsis elevate SST-LI in the systemic circulation, presumably by inducing its release from sensory fibres. It is concluded, that the endogenous protective mechanism mediated by neural somatostatin, which has been evidenced in animals, is likely to operate in patients.