Local lactate and histamine changes in small bowel circulation measured by microdialysis in pig hemorrhagic shock

Hemorrhagic shock results in inadequate tissue oxygenation. Plasma lactate (L) can characterize the degree of systemic oxygen debt (OD), but gives no information on local changes. The aim of this study was to characterize different degrees of hemorrhagic shock by microdialysis measurement of L and histamine (H) in small bowel circulation. Thirty-eight pigs were randomized to five groups of increasing OD (< 50 --> 120 ml/kg). The OD was accrued by hemorrhage over 60 min and was followed by retransfusion and observation for 3 days. In parallel to plasma probes, subserosa(ss)-, submucosa(sm)-, and intraluminal(il)-L- and H-probes were obtained by small bowel microdialysis every 30 min for 210 min. Ss- and sm-L increased during hemorrhage from 1.2 +/- 0.06 and 1.18 +/- 0.06 to 2.57 +/- 0.15 and 2.96 +/- 0.27 mmol/L. Highest mean L > 3.5mmol/L resulted 90 and 120 min after induction of hemorrhage. Although ss- and sm- levels hardly differed, il-L was significantly decreased with 0.27 +/- 0.02 mmol/L at 0 min and highest mean il-L at 120 min: 2.45 +/- 0.51 mmol/L. Sm-L was significantly increased after 60, 90, 120, and 150 min of highest hemorrhage severity (OD > 100 mL/kg). In parallel, systemic L increased significantly during hemorrhage and correlated well with the severity of shock. Although systemic H increased significantly during hemorrhage (from 1.3 +/- 0.31 to 15.2 +/- 0.67 ng/mL), H-dialysates showed no effect either over time nor with the degree of hemorrhage. In conclusion, microdialysis allows evaluation of local L changes in small bowel circulation in pig hemorrhagic shock. Sm-L levels appear to correlate with the degree of shock. Local H changes were not observed during hemorrhagic shock in this study.