Impairment of endothelium-dependent dilation response after resuscitation from hemorrhagic shock involved postreceptor mechanisms

Hemorrhage-induced hepatic injury and hypoperfusion can be prevented by direct peritoneal resuscitation

BACKGROUND

Crystalloid fluid resuscitation after hemorrhagic shock (HS) that restores/maintains central hemodynamics often culminates in multi-system organ failure and death due to persistent/progressive splanchnic hypoperfusion and end-organ damage. Adjunctive direct peritoneal resuscitation (DPR) using peritoneal dialysis solution reverses HS-induced splanchnic hypoperfusion and improves survival. We examined HS-mediated hepatic perfusion (galactose clearance), tissue injury (histopathology), and dysfunction (liver enzymes).

METHODS

Anesthetized rats were randomly assigned (n = 8/group): (1) sham (no HS); (2) HS (40% mean arterial pressure for 60 min) plus conventional i.v. fluid resuscitation (CR; shed blood + 2 volumes saline); (3) HS + CR + 30 mL intraperitoneal (IP) DPR; or (4) HS + CR + 30 mL IP saline. Hemodynamics and hepatic blood flow were measured for 2 h after CR completion. In duplicate animals, liver and splanchnic tissues were harvested for histopathology (blinded, graded), hepatocellular function (liver enzymes), and tissue edema (wet-dry ratio).

RESULTS

Group 2 decreased liver blood flow, caused liver injuries (focal to submassive necrosis, zones 2 and 3) and tissue edema, and elevated liver enzymes (alanine aminotransferase (ALT), 149 +/- 28 microg/mL and aspartate aminotransferase (AST), 234 +/- 24 microg/mL; p < 0.05) compared to group 1 (73 +/- 9 and 119 +/- 10 microg/mL, respectively). Minimal/no injuries were observed in group 3; enzymes were normalized (ALT 89 +/- 9 microg/mL and AST 150 +/- 17 microg/mL), and tissue edema was similar to sham.

CONCLUSIONS

CR from HS restored and maintained central hemodynamics but did not restore or maintain liver perfusion and was associated with significant hepatocellular injury and dysfunction. DPR added to conventional resuscitation (blood and crystalloid) restored and maintained liver perfusion, prevented hepatocellular injury and edema, and preserved liver function.

Mechanisms of direct peritoneal resuscitation-mediated splanchnic hyperperfusion following hemorrhagic shock

Conventional resuscitation (CR) from hemorrhagic shock causes a persistent and progressive splanchnic vasoconstriction and hypoperfusion despite hemodynamic restoration with intravenous fluid therapy. Adjunctive direct peritoneal resuscitation (DPR) with a clinical peritoneal dialysis solution instilled into the peritoneal cavity has been shown to restore splanchnic tissue perfusion, down-regulate the gut-derived exaggerated systemic inflammatory response, promote early fluid mobilization, and improve overall outcome. This study was conducted to define the molecular mechanisms of DPR-induced gut hyperperfusion after hemorrhagic shock. Male rats were bled to 50% baseline mean arterial pressure and resuscitated with the shed blood plus two volumes of saline (CR). In vivo videomicroscopy and Doppler velocimetry were used to assess terminal ileal microvascular diameters and blood flow. Direct peritoneal resuscitation animals received CR and topical application of a clinical glucose-based peritoneal dialysis solution (Delflex). Inhibitors, glibenclamide (K(+)ATP channels), N-monomethyl-L-arginine (L-NMMA) (nitric oxide synthase), 8-cyclopentyl-1,3-diprophylxanthine (DPCPX) (A1 adenosine receptor), tetrabutylammonium (K(+)Ca2+ channels), and mefenamic acid (cyclooxygenase) were topically applied (individually or in combination) with DPR according to protocol; BQ-123 (endothelin A receptor antagonist) and BQ-788 (endothelin B receptor antagonist) were used topically with CR to define the mechanism of post-CR vasoconstriction and hypoperfusion. Conventional resuscitation caused a persistent progressive intestinal vasoconstriction and hypoperfusion that can be abolished with endothelin antagonists. In contrast, adjunctive DPR caused an instantaneous sustained vasodilation and hyperperfusion. Glibenclamide or L-NMMA partially attenuated DPR-induced vasodilation, whereas the addition of DPCPX to the two inhibitors eliminated the dilation. Cyclooxygenase and K(+)Ca2+channels were not active in DPR-mediated microvascular effects. In conclusion, DPR improves splanchnic tissue perfusion by endothelium-dependent mechanisms mediated by activations of glibenclamide-sensitive K(+) channels (KATP), adenosine A1 receptor subtype activation, and nitric oxide release. Direct peritoneal resuscitation preserves endothelial dilatory functions, thereby overriding any endothelium-derived constrictor response triggered by hemorrhagic shock and CR.

Clinical peritoneal dialysis solutions modulate white blood cell-intestinal vascular endothelium interaction

BACKGROUND

Hemorrhagic shock (HS) with conventional resuscitation (CR) (HSCR) primes neutrophils and modulates leukocyte (WBC)-endothelium interaction as part of an exaggerated systemic inflammatory response. We hypothesize that topical application of clinical peritoneal dialysis solutions (PD) modulates such interaction.

METHODS

Intestinal intravital microscopy was used to measure WBC rolling in terminal ileum post capillary venules (V2 and V3) in sham-operated animals, and in animals that underwent fixed pressure hemorrhage (50% mean arterial pressure for 60 minutes), followed by conventional resuscitation with the return of the shed blood and 2 vol of saline. Number of rolling WBCs per thirty seconds in selected V2 and V3, bathed in either Kreb's solution or a 2.5% clinical peritoneal dialysis solution (PD) was quantified. Diameters were measured for the in-flow arterioles (A1), and out-flow venules (V1), for calculation of local blood flow with optical Doppler velocimetry.

RESULTS

The PD solution significantly (P < .05, n = 11) attenuated WBC-endothelium interaction in sham-operated animals while no significant difference was elicited in HSCR (P > .05, n = 9 Kreb's, n = 7 PD). In addition, the PD solution produced an instantaneous dilation at all levels of the intestinal arterioles in both sham and HSCR. While intestinal venular blood outflow was increased by the PD solution, venular diameters changed very little.

CONCLUSION

Superfusion of the gut with glucose-based peritoneal dialysis solutions decreases the concentration of rolling leukocytes along the venular vascular endothelium by a vasodilation-mediated increase in arteriolar inflow and venous outflow mechanism. Hemorrhagic shock and conventional resuscitation enhance the concentration of rolling leukocytes presumably by mechanisms related to upregulation of the adhesion molecules and the low-flow state. Hemorrhage and resuscitation-enhanced leukocytes rolling was not reversed by adjunctive DPR despite the associated marked increase in arterial inflow and venous outflow. The status of the endothelium and the level of leukocyte priming in low-flow states are stronger predictors of leukocyte-endothelium interaction than rheology factors.

Direct energy delivery improves tissue perfusion after resuscitated shock

BACKGROUND

Conventional resuscitation (CR) from hemorrhagic shock (HS) does not restore intestinal blood flow. Indicators of anaerobic metabolism suggest that cellular energy production also is compromised. We hypothesize that the direct intravenous delivery of lipid-encapsulated high-energy phosphates to cells improves intestinal perfusion during HS and resuscitation (RES).

METHODS

MAP (MAP) was monitored in male rats (200 g), terminal ileum microvessel diameters were measured by in vivo videomicroscopy, and blood flow (Doppler velocimetry) was calculated. Cellular energy delivery was accomplished by intravenous infusion during RES of fusogenic unilamellar lipid vesicles that contain adenosine triphosphate (ATP; VitaSol). Our protocol was HS to 50% baseline MAP for 60 minutes, 30 minutes of RES, and continued microscopy observation for 120 minutes. Experimental groups (n=8 each) were HS+CR (group I); HS+CR+ VitaSol (group II); HS+CR+Vehicle, Vehicle is the phospholipid vesicles without magnesium ATP, (group III); HS+ VitaSol (group IV); sham-operated control+VitaSol (group V); and a time-matched sham-operated control (group VI). The survival outcome and total tissue water from wet weight/dry weight ratio as a function of adjunct VitaSol resuscitation were evaluated in separate intact animal experiments.

RESULTS

HS caused a selective vasoconstriction of the intestinal inflow arterioles (100 microm), which was not seen in the smaller intestinal premucosal arterioles (7-15 microm). CR, which restored baseline hemodynamics, resulted in an initial restoration of intestinal microvascular diameters at all arteriolar levels. However, this was followed by a progressive vasoconstriction and hypoperfusion in premucosal vessels at 120 minutes after RES (-20.48% +/- 2.95% from baseline diameters). In contrast, VitaSol with CR caused enhanced premucosal dilation (+34.27% +/- 4.62%) and augmented flow (+20.50% +/- 10.70%) above prehemorrhage baseline. Vesicles alone had no effect, and VitaSol alone caused only a modest dilation. CR of moderate HS (40% of baseline MAP for 60 minutes, n=10) caused 20% mortality, whereas adjunct VitaSol resuscitation had a 100% survival and less tissue water content.

CONCLUSIONS

Our data confirms that CR causes progressive intestinal hypoperfusion. Cellular resuscitation with direct intravenous energy delivery improves intestinal perfusion after CR and results in improved survival and less tissue edema.