Heme oxygenase-dependent carbon monoxide production is a hepatic adaptive response to sepsis.

The hemodynamic effects of sepsis have been attributed in part to increased nitric oxide (NO) production and activation of guanylate cyclase, resulting in increased cGMP and relaxation of vascular smooth muscle. Heme oxygenase-1 (HO-1), a heat shock protein, has been shown to increase intracellular cGMP levels by formation of carbon monoxide (CO). We hypothesized that HO may be an important mediator of the hepatic response to infection. Male Swiss Webster mice underwent standard cecal ligation and puncture (CLP, 18 gauge 2X) or sham operation, and received either normal saline (NS) or Zn protoporphyrin IX (ZN PP IX), a competitive HO inhibitor (n = 6-8/group). Hepatic tissue samples were collected at 3, 6, 12, and 24 hr from separate mice. Serum was collected at 3 and 24 hr. A semiquantitative reverse transcriptase polymerase chain reaction method was used to measure HO-1 mRNA levels. Hepatic cGMP levels were measured by ELISA. Groups were repeated (n = 10/group) to assess mortality. Serum was collected at 3 and 24 hr to measure serum aspartate aminotransferase (AST) levels. HO-1 mRNA expression increased significantly by 3 hr after CLP and with HO inhibition alone (P < 0.05 vs sham + NS). HO-1 mRNA remained elevated through 24 hr. CLP animals with HO inhibition showed a significant reduction of hepatic cGMP following CLP compared with CLP + saline at 24 hr (P < 0.05). Mortality was significantly increased in the CLP + ZN PP group at 24 hr (P < 0.05 CLP NS vs CLP ZN PP). CLP caused a marked increase in AST activity, which was increased further with HO inhibition. HO-1 mRNA expression was induced by CLP. AST levels following CLP were markedly increased with HO inhibition. HO-1 function appeared to contribute to elevation of hepatic cGMP during peritonitis and may be an important hepatic adaptive response to infection.

Heparan preserves intestinal perfusion after hemorrhage and resuscitation.

BACKGROUND: Multiple system organ failure (MOF) remains a major source of morbidity and mortality in trauma patients. Despite restoration of central hemodynamics, intestinal hypoperfusion can persist. Mucosal ischemia and barrier breakdown are factors in the genesis of MOF. Heparan sulfate is a gycosaminoglycan similar to heparin, but with minimal anticoagulant properties. As an adjunct to resuscitation, it improves immunologic function and restores mucosal oxygenation and function. We hypothesized that resuscitation with heparan following hemorrhage wound prevents intestinal hypoperfusion. MATERIALS AND METHODS: In vivo videomicroscopy was used to study small intestine microcirculation in rats. Animals were hemorrhaged to 50% of baseline mean arterial pressure (MAP) and maintained there. Resuscitation was initiated when the return of 10% shed blood was required to keep MAP at 50%. Animals received either heparan (7 mg/kg/1 ml saline) or saline (1 ml) followed by the remaining shed blood and an equal volume of saline. MAP, cardiac output (CO), A1 arteriole diameters, and flow were determined. RESULTS: Resuscitation of the saline control group resulted in normal MAP with elevation of CO to 25-40% above baseline. The heparan group had return of MAP but only a moderate increase in CO (7-15%). Saline resuscitation led to progressive deterioration in A1 diameters and flow. The addition of heparan prevented delayed A1 constriction and significantly improved perfusion. CONCLUSIONS: Heparan prior to resuscitation improved intestinal perfusion, despite a relative reduction in CO. Improvement in nutrient blood flow may protect the mucosal barrier, reducing the incidence of MOF, and suggests that heparan may be useful in resuscitation of trauma patients.

Fluid resuscitation attenuates early cytokine mRNA expression after peritonitis.

OBJECTIVE: To study the hypothesis that fluid resuscitation alters cytokine gene expression after experimental murine peritonitis. MATERIALS AND METHODS: Mice underwent cecal ligation and puncture (CLP) to induce peritonitis and were randomized to receive variable amounts of normal saline (0, 0.25, 1.0 ml. subcutaneously) and serum (0 or 0.1 mL) after operation. Hepatic and small intestinal (ileal) tissue were harvested at 3 or 6 hours after CLP, and total tissue RNA was extracted. Reverse transcriptase polymerase chain reaction was used to provide relative quantitation of tumor necrosis factor-alpha and interleukin (IL)-1 beta messenger RNA (mRNA) compared with beta-actin. RESULTS: CLP without resuscitation resulted in significant increases in hepatic tumor necrosis factor-alpha mRNA (1190% at 6 hours compared with normal animals), and IL-1 beta mRNA (1475%), and intestinal IL-1 beta mRNA (1243%). Volume administration attenuated cytokine expression at both 3 and 6 hours, and saline seemed to have more potent effects than serum. The volume of resuscitation correlated with survival at 18 hours. Survival in the saline (1 mL) + serum group was 90% at 18 hours compared with 20 to 40% in the groups with little or no resuscitation. Overall, there were no survivors at 30 hours. CONCLUSIONS: Fluid resuscitation (amount, composition, timing) should be an important consideration in the utilization of experimental infection models. Furthermore, optimization of the patient's intravascular volume status during sepsis may have important effects on immune responses, in addition to improving hemodynamic variables.