Postoperative on-line monitoring with intraperitoneal microdialysis (IPM) detects early visceral ischemia and correlates to the current intraperitoneal cytokine response

Background

Visceral ischemia and macrophage activation are early signs in the development of shock and multiorgan failure. Activated macrophages produce proinflammatory cytokines (like TNF-α) that generate an inflammatory reaction. If the inhibition of this reaction (mainly by IL-10) is not strong enough, cascade systems will be activated; shock and multiorgan failure will be the result. The aim of this study was to investigate the reliability and safety of intraperitoneal microdialysis and to find out whether early visceral ischemia can be detected.

Methods

Nineteen patients were operated, 14 elective patients and five patients as emergencies. These 19 patients were followed during 45 postoperative hours with IPM. A CMA 65 catheter was placed intraperitoneally before closure of the abdomen. Analysis was performed every second hour of glucose, pyruvate, lactate and glycerol, the ratio between lactate and pyruvate was calculated as a factor of peritoneal ischemia. Samples of peritoneal fluid were collected from an 18 Fr peritoneal drainage every sixth hour and TNF-α and IL-10 were analysed.

Sixteen of the patients had a normal postoperative course during the study, the lactate/pyruvate ratio started at the level of 20 immediately postoperatively, decreasing to 15 and, after 27 hours there was a short peak to 22, rapidly decreasing to a steady state around 12. This pattern was also seen regarding peritoneal TNF-α, it decreased immediately postoperatively and had a short peak after 27 hours. Peritoneal lactate/pyruvate ratio and peritoneal TNF-α correlated (Spearman nonparametric test 0.303, P = 0.001).

Three of the patients had abnormalities in the microdialysis results.

• Patient 1 was operated due to rectal cancer. After 24 hours, his lactate/pyruvate ratio started to increase and he developed low saturation. He was treated with oxygen and the lactate/pyruvate ratio was normalized. Peritoneal TNF-α and IL-10 had high and short peaks during this time.

• Patient 2 was operated due to esophageal cancer. After 23 hours, his lactate/pyruvate ratio increased and he developed abdominal pain despite epidural anesthesia. Peritoneal TNF-α and IL-10 increased to a second peak after 80 hours.

• Patient 3 was operated due to an acute perforated gastric ulcer. Postoperatively there was a high lactate/pyruvate ratio, which increased to 60 after 15 hours; clinically the patient was in shock with decreasing blood pressure and oliguria. He developed acute renal failure and died 42 hours postoperatively. His peritoneal TNF immediately postoperatively was increased 30 times related to the patients with normal postoperative course. During the last 15 hours, his peritoneal TNF increased, while his IL-10 decreased.

Conclusions

A normal postoperative course results in decreasing the lactate/pyruvate ratio, peritoneal TNF-α and IL-10. In our study we present three patients with abnormalities in IPM; these patients also had clinical and peritoneal cytokine abnormalities that support the theory that visceral ischemia is a preceeding factor in shock and multiorgan failure. IPM seems to be a safe method for the patient and we have not seen any complication due to the catheters in these 19 patients nor in the 65 patients we have studied with postoperative IPM. We believe IPM can act as an early marker of visceral ischemia even in clinical practice, but further studies to confirm this are mandatory. Our aim is to continue this investigation in ICU patients at risk of developing septicemia and multiorgan failure.