Differential alterations in microvascular perfusion in various organs during early and late sepsis

Clinical importance of "occult-bacterial translocation" in patients undergoing highly invasive gastrointestinal surgery: A review

In the clinical setting, mild bacteremia cannot be detected by conventional culture methods, only by a highly sensitive bacterial detection system. One of the major causes of mild bacteremia is bacterial translocation (BT) induced by a dysregulated intestinal microenvironment and increased intestinal epithelial permeability. This condition is called "occult-bacterial translocation (O-BT)"; however, the concept of O-BT is not yet fully recognized. In our previous studies, done using a highly sensitive bacterial detection system such as bacterium-specific ribosomal RNA-targeted reverse transcriptase quantitative polymerase chain reaction (RT-qPCR), O-BT was commonly observed in patients who underwent highly invasive surgery. We collected blood and mesenteric lymph node (MLN) samples from patients undergoing esophagectomy for esophageal cancer, before and after they were subjected to surgical stress. The detection rate of bacteria in these samples increased from approximately 20% before surgical stress to more than 50% after surgical stress. Moreover, positivity for bacteria in the blood or MLN samples was associated with the incidence of postoperative infectious complications (POICs). Using the RT-qPCR system, it is possible to detect the specific bacteria that cause O-BT immediately after surgery. This may allow us to select the exact antibiotic that targets possible pathogenic bacteria of POICs.

Decreased Tissue COX5B Expression and Mitochondrial Dysfunction during Sepsis-Induced Kidney Injury in Rats

Background. Sepsis is defined as a life-threatening organ dysfunction due to a dysregulated host response to infection. Sepsis is the dominant cause of acute kidney injury (AKI), accounting for nearly 50% of episodes of acute renal failure. Signaling cascades and pathways within the kidney are largely unknown and analysis of these molecular mechanisms may enhance knowledge on pathophysiology and possible therapeutic options. Material and Methods. 26 male Wistar rats were assigned to either a sham group (control, N = 6) or sepsis group (N = 20; cecal ligature and puncture model, 24 and 48 hours after CLP). Surviving rats (n = 12) were decapitated at 24 hours (early phase; n = 6) or 48 hours (late phase; n = 6) after CLP and kidneys removed for proteomic analysis. 2D-DIGE and DeCyder 2D software (t-test, P < 0.01) were used for analysis of significantly regulated protein spots. MALDI-TOF in combination with peptide mass fingerprinting (PMF) as well as Western Blot analysis was used for protein identification. Bioinformatic network analyses (STRING, GeneMania, and PCViz) were used to describe protein-protein interactions. Results. 12 spots were identified with significantly altered proteins (P < 0.01) in the three analyzed groups. Two spots could not be identified. Four different proteins were found significantly changed among the groups: major urinary protein (MUP5), cytochrome c oxidase subunit B (COX5b), myosin-6 (MYH6), and myosin-7 (MYH7). A significant correlation with the proteins was found for mitochondrial energy production and electron transport. Conclusions. COX5B could be a promising biomarker candidate since a significant association was found during experimental sepsis in the present study. For future research, COX5B should be evaluated as a biomarker in both human urine and serum to identify sepsis.

Pulse pressure variation shows a direct linear correlation with tidal volume in anesthetized healthy patients

Background

The settings of mechanical ventilation, like tidal volume (VT), occasionally need to be adjusted in the process of anesthesia for some special reasons. The aim of this study was therefore to assess the relationship between pulse pressure variations (PPVs) in different settings of VT in anesthetized healthy patients under mechanical ventilation.

Methods

Sixty nine ASA I-II patients scheduled for gastrointestinal surgery under general anesthesia were included in this prospective study. All the patients were ventilated at a VT of 6, 8 or 10 ml/kg (predicted body weight) with no positive end expiratory pressure (PEEP) in a random order after intubation. PPV, mean arterial blood pressure, and other hemodynamic and respiratory parameters were recorded in each VT setting respectively after Partial Pressure of End-Tidal Expiration Carbon Dioxide (PetCO₂) maintained between 30 mmHg and 40 mmHg by changing Respiratory Rate (RR) before incision.

Results

The values of PPV at different settings of VT showed a tight correlation between each other (6 vs. 8 ml/kg: r = 0.97, P < 0.0001; 6 vs.10 ml/kg: r = 0.95, P < 0.0001; 8 vs. 10 ml/kg: r = 0.98, P < 0.0001, respectively).

Conclusion

There is a direct linear correlation between PPVs at different tidal volumes in anesthetized ASA I-II patients. PPV in any of the 3 VT settings (6, 8 or 10 ml/kg) can deduce that in any other 2 settings. Further studies are needed to explore the effect of intraoperative confounders for this knowledge to be clinically applied.

Trial registration

NCT01950949, www.clinicaltrials.gov, July 26, 2013.

Combined Administration of Human Ghrelin and Human Growth Hormone Attenuates Organ Injury and Improves Survival in Aged Septic Rats

Sepsis is a major healthcare concern, especially in the elderly population. The use of an animal model closely resembling clinical conditions in this population may provide a better prediction in translating bench studies to the bedside. Ghrelin inhibits sympathetic nerve activity and inflammation in young septic animals; however, aged animals become hyporesponsive to ghrelin. In this study, we evaluated the efficacy of combined human ghrelin and growth hormone (GH) for sepsis treatment in the elderly utilizing a clinically relevant animal model of sepsis. Male Fischer 344 rats 22 to 24 months old were subjected to cecal ligation and puncture (CLP). Human ghrelin plus GH or vehicle (normal saline) was administered subcutaneously at 5 h after CLP. At 20 h after CLP, blood and tissue samples were collected for various analyses. Combined treatment attenuated serum levels of lactate, lactate dehydrogenase, creatinine, blood urea nitrogen, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in aged septic rats. The integrity of the microscopic structure in the lungs, liver and kidneys was well preserved after treatment. Expression of IL-6, TNF-α, macrophage inflammatory protein-2 and keratinocyte-derived chemokine as well as myeloperoxidase activity and caspase-3 activation were significantly reduced in the lungs and liver of treated rats. Moreover, treated rats showed an improvement in cardiovascular function and increased expression of ghrelin receptor and c-fos in the brainstem. Finally, the 10-d survival of aged septic rats was increased from 29% to 64% after combined treatment and was associated with less body weight loss. Our findings warrant the development of combined human ghrelin and GH for sepsis treatment in the geriatric population.

The comparison of stroke volume variation with central venous pressure in predicting fluid responsiveness in septic patients with acute circulatory failure

Purpose:

The present study was designed to investigate the efficacy of stroke volume variation (SVV) in predicting fluid responsiveness and compare it to traditional measures of volume status assessment like central venous pressure (CVP).

Methods:

Forty-five mechanically ventilated patients in sepsis with acute circulatory failure. Patients were not included when they had atrial fibrillation, other severe arrhythmias, permanent pacemaker, or needed mechanical cardiac support. Furthermore, excluded were patients with hypoxemia and a CVP >12. Patients received volume expansion in the form of 500 ml of 6% hydroxyethyl starch.

Results:

The volume expansion-induced increase in  cardiac index (CI) was >15% in 29 patients (labeled responders) and <15% in 16 patients (labeled nonresponders). Before volume expansion, SVV was higher in responders than in nonresponders. Receiver operating characteristic curves analysis showed that SVV was a more accurate indicator of fluid responsiveness than CVP. Before volume expansion, an SVV value of 13% allowed discrimination between responders and nonresponders with a sensitivity of 78% and a specificity of 89%. Volume expansion-induced changes in CI weakly and positively correlated with SVV before volume expansion. Volume expansion decreased SVV from 18.86 ± 4.35 to 7.57 ± 1.80 and volume expansion-induced changes in SVV moderately correlated with volume expansion-induced changes in CI.

Conclusions:

When predicting fluid responsiveness in mechanically ventilated patients in septic shock, SVV is more effective than CVP. Nevertheless, the overall correlation of baseline SVV with increases in CI remains poor. Trends in SVV, as reflected by decreases with volume replacement, seem to correlate much better with increases in CI.

Pulse Wave Transit Time Measurements of Cardiac Output in Septic Shock Patients: A Comparison of the Estimated Continuous Cardiac Output System with Transthoracic Echocardiography

Background

We determined reliability of cardiac output (CO) measured by pulse wave transit time cardiac output system (esCCO system; CO_esCCO) vs transthoracic echocardiography (CO_TTE) in mechanically ventilated patients in the early phase of septic shock. A secondary objective was to assess ability of esCCO to detect change in CO after fluid infusion.

Methods

Mechanically ventilated patients admitted to the ICU, aged >18 years, in sinus rhythm, in the early phase of septic shock were prospectively included. We performed fluid infusion of 500ml of crystalloid solution over 20 minutes and recorded CO by EsCCO and TTE immediately before (T0) and 5 minutes after (T1) fluid administration. Patients were divided into 2 groups (responders and non-responders) according to a threshold of 15% increase in CO_TTE in response to volume expansion.

Results

In total, 25 patients were included, average 64±15 years, 15 (60%) were men. Average SAPSII and SOFA scores were 55±21.3 and 13±2, respectively. ICU mortality was 36%. Mean cardiac output at T0 was 5.8±1.35 L/min by esCCO and 5.27±1.17 L/min by CO_TTE. At T1, respective values were 6.63 ± 1.57 L/min for esCCO and 6.10±1.29 L/min for CO_TTE. Overall, 12 patients were classified as responders, 13 as non-responders by the reference method. A threshold of 11% increase in CO_esCCO was found to discriminate responders from non-responders with a sensitivity of 83% (95% CI, 0.52-0.98) and a specificity of 77% (95% CI, 0.46-0.95).

Conclusion

We show strong correlation esCCO and echocardiography for measuring CO, and change in CO after fluid infusion in ICU patients.

Ghrelin maintains the cardiovascular stability in severe sepsis

BACKGROUND

Cardiovascular dysfunction, characterized by reduced cardiac contractility and depressed endothelium-dependent vascular relaxation, is common in severe sepsis. Although it is known that ghrelin produces beneficial effects following various adverse circulatory conditions, it remains unknown whether ghrelin increases cardiac contractility and improves vascular responsiveness to vasoactive agents in severe sepsis.

METHODS

Male adult rats were subjected to sepsis by cecal ligation and puncture (CLP). At 5 h after CLP, a bolus intravenous injection of 2 nmol ghrelin was followed by a continuous infusion of 12 nmol ghrelin via a primed mini-pump over 15 h. At 20 h after CLP (i.e., severe sepsis), the maximal rates of ventricular pressure increase (+dP/dt(max)) and decrease (-dP/dt(max)) were determined in vivo. In additional groups of animals, the thoracic aortae were isolated at 20 h after CLP. The aortae were cut into rings, and placed in organ chambers. Norepinephrine (NE) was used to induce vascular contraction. Dose responses for an endothelium-dependent vasodilator, acetylcholine (ACh), and an endothelium-independent vasodilator, nitroglycerine (NTG) were carried out.

RESULTS

+dP/dt(max) and -dP/dt(max) decreased significantly at 20 h after CLP. Treatment with ghrelin significantly increased +dP/dt(max) and -dP/dt(max) by 36% (P < 0.05) and 35% (P < 0.05), respectively. Moreover, NE-induced vascular contraction and endothelium-dependent (ACh-induced) vascular relaxation decreased significantly at 20 h after CLP. Administration of ghrelin, however, increased NE-induced vascular contraction and ACh-induced vascular relaxation. In contrast, no significant reduction in NTG-induced vascular relaxation was seen in rats with severe sepsis irrespective of ghrelin treatment.

CONCLUSIONS

Ghrelin may be further developed as a useful agent for maintaining cardiovascular stability in severe sepsis.

Downregulation of protein disulfide isomerase in sepsis and its role in tumor necrosis factor-alpha release

Introduction

Protein disulfide isomerase (PDI) is an important factor for the protein modification step in the post-translational event. PDI plays an essential role in cell survival under various stress conditions. It has been reported that PDI can serve as a negative regulator of nuclear factor-kappa-B (NF-κB) and that it can inhibit lipopolysaccharide (LPS)-induced proinflammatory cytokine production in macrophages. Thus, PDI may be an intracellular anti-inflammatory molecule. Although we have previously shown that Kupffer cell-derived proinflammatory cytokines cause liver injury in sepsis, the effect of sepsis on PDI expression as well as the effect of PDI inhibition on cytokine production have not been investigated. We therefore hypothesized that sepsis downregulates PDI expression and that the inhibition of PDI promotes proinflammatory cytokine production.

Method

Adult male rats were subjected to sepsis by cecal ligation and puncture (CLP) or endotoxemia (continuous infusion of 1 μg/kg body weight LPS by an osmotic pump) for 20 hours. Hepatic tissues were collected and PDI gene expression was determined. In additional experiments, cells from a macrophage-like cell line, RAW 264.7, were treated with 100 ng/mL LPS for 4 hours and protein expressions were measured. RAW 264.7 cells were also treated with bacitracin, a specific PDI inhibitor, for 24 hours, and tumor necrosis factor-alpha (TNF-α) gene and protein expression as well as its release in the cell supernatant were determined. To further confirm the beneficial effect of PDI in sepsis, RAW 264.7 cells were transfected with PDI short interfering RNA (siRNA) and PDI gene expression and TNF-α release were measured by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.

Results

PDI gene expression was significantly decreased by 28% and 69% at 20 hours after CLP or LPS infusion, respectively. LPS also decreased PDI protein expression by 33% in RAW 264.7 cells. Incubation of RAW 264.7 cells with bacitracin significantly increased TNF-α gene expression and TNF-α release as well as its cellular levels in a dose-dependent manner. Transfection of RAW 264.7 cells with PDI siRNA produced an average 36.8% inhibition of the PDI gene expression. This downregulation was correlated with a 3.19-fold increase in TNF-α release into the cell supernatant.

Conclusion

Taken together, these results suggest that downregulation of PDI by sepsis significantly increases proinflammatory cytokine production. Thus, prevention of PDI downregulation in sepsis may be a novel approach to attenuate hyperinflammation and to reduce tissue injury under such conditions.

Hepatic platelet and leukocyte adherence during endotoxemia

INTRODUCTION

Liver microcirculation disturbances are a cause of hepatic failure in sepsis. Increased leukocyte-endothelial interaction, platelet adherence and impaired microperfusion cause hepatocellular damage. The time course and reciprocal influences of ongoing microcirculatory events during endotoxemia have not been clarified.

METHODS

Male Wistar rats (232 +/- 17 g) underwent cecal ligation and puncture (CLP). Intravital microscopy (IVM) was performed 0, 1, 3, 5, 10 and 20 hours after CLP. Mean erythrocyte velocity, leukocyte and platelet rolling in postsinusoidal venules and sticking of leukocytes and platelets in postsinusoidal venules and hepatic sinusoids were determined. Heart rate (HR), mean arterial pressure (MAP) and portal venous blood flow (PBF) were measured. Blood count and investigation of hepatic enzyme release was performed after each IVM time point.

RESULTS

Hepatic platelet-endothelial adherence in liver sinusoids and postsinusoidal venules occurred one hour after the induction of endotoxemia. Leukocyte-endothelial interaction started three to five hours after CLP. A decrease of hepatic microperfusion could be observed at three hours in sinusoids and ten hours in postsinusoidal venules after CLP, although PBF was reduced one hour after CLP. HR remained stable and MAP decreased ten hours after CLP. Hepatic enzymes in blood were significantly elevated ten hours after CLP.

CONCLUSION

Hepatic platelet-endothelial interaction is an early event during endotoxemia. Leukocyte adherence occurs later, which underlines the probable involvement of platelets in leukocyte recruitment. Although PBF is reduced immediately after CLP, the later onset of hepatic microperfusion decrease makes the existence of autoregulatory liver mechanisms likely.

Simvastatin improves sepsis-induced mortality and acute kidney injury via renal vascular effects

Acute kidney injury (AKI) occurs in about half of patients in septic shock and the mortality of AKI with sepsis is extremely high. An effective therapeutic intervention is urgently required. Statins are 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors that also have pleiotropic actions. They have been reported to increase the survival of septic or infectious patients. But the effect of simvastatin, a widely used statin, on sepsis-induced AKI is unknown. The effects of simvastatin and tumor necrosis factor (TNF)-alpha neutralizing antibody were studied in a clinically relevant model of sepsis-induced AKI using cecal ligation and puncture (CLP) in elderly mice. Simvastatin significantly improved CLP-induced mortality and AKI. Simvastatin attenuated CLP-induced tubular damage and reversed CLP-induced reduction of intrarenal microvascular perfusion and renal tubular hypoxia at 24 h. Simvastatin also restored towards normal CLP-induced renal vascular protein leak and serum TNF-alpha. Neither delayed simvastatin therapy nor TNF-alpha neutralizing antibody improved CLP-induced AKI. Simvastatin improved sepsis-induced AKI by direct effects on the renal vasculature, reversal of tubular hypoxia, and had a systemic anti-inflammatory effect.

Renal blood flow in sepsis

Introduction

To assess changes in renal blood flow (RBF) in human and experimental sepsis, and to identify determinants of RBF.

Method

Using specific search terms we systematically interrogated two electronic reference libraries to identify experimental and human studies of sepsis and septic acute renal failure in which RBF was measured. In the retrieved studies, we assessed the influence of various factors on RBF during sepsis using statistical methods.

Results

We found no human studies in which RBF was measured with suitably accurate direct methods. Where it was measured in humans with sepsis, however, RBF was increased compared with normal. Of the 159 animal studies identified, 99 reported decreased RBF and 60 reported unchanged or increased RBF. The size of animal, technique of measurement, duration of measurement, method of induction of sepsis, and fluid administration had no effect on RBF. In contrast, on univariate analysis, state of consciousness of animals (P = 0.005), recovery after surgery (P < 0.001), haemodynamic pattern (hypodynamic or hyperdynamic state; P < 0.001) and cardiac output (P < 0.001) influenced RBF. However, multivariate analysis showed that only cardiac output remained an independent determinant of RBF (P < 0.001).

Conclusion

The impact of sepsis on RBF in humans is unknown. In experimental sepsis, RBF was reported to be decreased in two-thirds of studies (62 %) and unchanged or increased in one-third (38%). On univariate analysis, several factors not directly related to sepsis appear to influence RBF. However, multivariate analysis suggests that cardiac output has a dominant effect on RBF during sepsis, such that, in the presence of a decreased cardiac output, RBF is typically decreased, whereas in the presence of a preserved or increased cardiac output RBF is typically maintained or increased.

A1 adenosine receptor knockout mice exhibit increased mortality, renal dysfunction, and hepatic injury in murine septic peritonitis

Sepsis is a leading cause of multiorgan dysfunction and death in hospitalized patients. Dysregulated inflammatory processes and apoptosis contribute to the pathogenesis of sepsis-induced organ dysfunction and death. A(1) adenosine receptor (A(1)AR) activation reduces inflammation and apoptosis after ischemia-reperfusion injury. Therefore, we questioned whether A(1)AR-mediated reduction of inflammation and apoptosis could improve mortality and organ dysfunction in a murine model of sepsis. A(1)AR knockout mice (A(1) knockout) and their wild-type (A(1) wild-type) littermate controls were subjected to cecal ligation and double puncture (CLP) with a 20-gauge needle. A(1) knockout mice or A(1) wild-type mice treated with 1,3-dipropyl-8-cyclopentylxanthine (a selective A(1)AR antagonist) had a significantly higher mortality rate compared with A(1) wild-type mice following CLP. Mice lacking endogenous A(1)ARs demonstrated significant elevations in plasma creatinine, alanine aminotransferase, aspartate aminotransferase, keratinocyte-derived chemokine, and tumor necrosis factor-alpha 24 h after induction of sepsis compared with wild-type mice. The renal corticomedullary junction from A(1) knockout mice also exhibited increased myeloperoxidase activity, intercellular adhesion molecule-1 protein, and mRNA encoding proinflammatory cytokines compared with renal samples from A(1) wild-type littermate controls. No difference in renal tubular apoptosis was detected between A(1) knockout and A(1) wild-type mice. We conclude that endogenous A(1)AR activation confers a protective effect in mice from septic peritonitis primarily by attenuating the hyperacute inflammatory response in sepsis.

Upregulation of cardiovascular ghrelin receptor occurs in the hyperdynamic phase of sepsis

Ghrelin, a newly identified endogenous ligand for growth hormone secretagogue receptor 1a (GHSR-1a, i.e., ghrelin receptor), was recently demonstrated to be a potent vasoactive peptide. Although sepsis is characterized by an early, hyperdynamic phase, it remains unknown whether ghrelin or GHSR-1a plays a role in the cardiovascular response to sepsis. To determine this, polymicrobial sepsis was induced by cecal ligation and puncture in male adult rats. At 5 h (i.e., early sepsis) or 20 h (i.e., late sepsis) after cecal ligation and puncture, blood and tissue samples were collected. Ghrelin levels and ghrelin and GHSR-1a mRNA expression were assessed by RIA and RT-PCR, respectively. In addition, GHSR-1a protein levels in aorta, heart, and small intestine were determined by Western blotting. The vascular response to ghrelin was determined by using an isolated gut preparation. A primary rat aortic smooth muscle cell culture was used to determine the effects of LPS on GHSR-1a expression. The results indicate that although ghrelin levels decreased at early and late sepsis, its receptor was markedly elevated in early sepsis. Moreover, ghrelin-induced relaxation in resistance blood vessels of the isolated small intestine increased significantly during early sepsis but was not altered in late sepsis. Furthermore, GHSR-1a expression in smooth muscle cells was significantly increased at mRNA and protein levels with stimulation by LPS at 10 ng/ml. These results demonstrate that GHSR-1a expression is upregulated and vascular sensitivity to ghrelin stimulation is increased in the hyperdynamic phase of sepsis.

Gut mucosal damage during endotoxic shock is due to mechanisms other than gut ischemia

Whether the gut alterations seen during sepsis are caused by microcirculatory hypoxia or disturbances in cellular metabolic pathways associated with mitochondrial respiration remains controversial. We hypothesized that hypoperfusion or hypoxia and local production of nitric oxide might play an important role in the development of gut mucosal injury during endotoxic shock and investigated their roles by using differing levels of fluid resuscitation and occlusion of the superior mesenteric artery (SMA). Anesthetized New Zealand rabbits were allocated to group I (sham, n = 8); group II [low-dose endotoxin (LPS, Escherichia coli-055:B5, 150 microg/kg)/fluid resuscitation (12 ml x kg(-1) x h(-1)); n = 8]; group III [high-dose LPS (1 mg/kg)/fluid resuscitation (12 ml x kg(-1) x h(-1)); n = 8]; group IV [high-dose LPS (1 mg/kg)/hypovolemia (4 ml x kg-1 x h(-1) fluids); n = 8]; and group V [SMA ligation/fluid resuscitation (12 ml x kg(-1) x h(-1)); n = 4]. Luminal gut lactate concentrations and PCO2 gap increased in groups IV and V (P < 0.05), reflecting alterations in gut perfusion. Interestingly, significant histological alterations were observed in all LPS groups but not in group V. Blood and luminal gut nitrate/nitrite concentrations increased only in group IV. The mechanism of gut injury in endotoxic shock seems unrelated to hypoxia and release of nitric oxide. Gut dysfunction may occur as a result of so-called "cytopathic hypoxia."

Prepro-endothelin-1 mRNA and its mature peptide in human appendix

Because the precise immunopathological events occurring in appendicitis are not completely understood, possible local production of endothelin-1 (ET-1) in human appendix was investigated. We used immunohistochemistry and in situ hybridization to detect the presence, distribution, and phenotype of ET-1-positive cells and prepro-ET-1 (pp-ET-1) mRNA-expressing cells. ET-1-positive stromal cells and pp-ET-1 mRNA-expressing cells were detected with different distributions and relative frequencies in normal control appendix, histologically normal appendix, and inflamed appendix. Six of 20 histologically normal appendixes from patients with a clinical diagnosis of acute appendicitis had many ET-1-positive stromal cells and high pp-ET-1 mRNA expression, similar to inflamed appendix. Forty percent of the pp-ET-1 mRNA-expressing cells were neutrophils, and the other positive cells were mast cells and macrophages. We suggest that local production of ET-1 by neutrophils and other inflammatory cells could be a molecular sign of focal inflammation in histologically normal appendixes and that ET-1 could be implicated, with other cytokines, in the pathogenesis of appendicitis by inducing appendiceal ischemia through vasoconstriction.

The effects of anisodamine and dobutamine on gut mucosal blood flow during gut ischemia/reperfusion

AIM: To determine if anisodamine is able to augment mucosal perfusion during gut I/R ischemia-reperfusion.

METHODS: A jejunal sac was formed in Sprague Dawley rat. A Laser Doppler probe and a tonometer were inserted into the sac which was filled with saline. The superior mesenteric artery was occluded (SMAO) for 60 minutes followed by 90 minutes of reperfusion. At the end of 60 minutes of SMAO, either 0.2 mg/kg of anisodmine or dobutamine was injected into the jejunal sac. Laser Doppler mucosal blood flow and regional PCO₂ (PrCO₂) measurements were made.

RESULTS: Mucosal blood flow was significantly increased at 30, 60 and 90 minutes of reperfusion (R₃₀, R₆₀, R₉₀) when intraluminal anisodamine or dobutamine was present compared to intraluminal saline only (44 ± 3.3% or 48 ± 4.1% vs 37 ± 2.6% at R₃₀, 57 ± 5.0% or 56 ± 4.7% vs 45 ± 2.7% at R₆₀, 64 ± 3.3% or 56 ± 4.2% vs 48 ± 3.4% at R₉₀, respectively P < 0.05). Blood flow changes were also reflected by lowering of jejunal PrCO₂ measurements after intraluminal anisodamine or dobutamine compared with that of the saline controls (41 ± 3.1 mmHg or 44 ± 3.0 mmHg vs 49 ± 3.7 mmHg at R₃₀, 38 ± 3.7 mmHg or 40 ± 2.1 mmHg vs 47 ± 3.8 mmHg at R₆₀, 34 ± 2.1 mmHg or 39 ± 3.0 mmHg vs 46 ± 3.4 mmHg at R₉₀, respectively, P < 0.05). Most interesting finding was that there were significantly higher mucosal blood flow and lower jejunal PrCO₂ in anisodamine group than those in dobutamine group at 90 minutes of reperfusion (64 ± 3.3% vs 56 ± 4.2% for blood flow or 34 ± 2.1 mmHg vs 39 ± 3.0 mmHg for PrCO₂, respectively, P < 0.05), suggesting that anisodamine had a more lasting effect on mucosal perfusion than dobutamine.

CONCLUSION: Intraluminal anisodamine and dobutamine can augment mucosal blood flow during gut I/R and alleviate mucosal acidosis. The results provided benificial effects on the treatment of splanchnic hypoperfusion following traumatic or burn shock.

The small intestine is an important source of adrenomedullin release during polymicrobial sepsis

Adrenomedullin (AM), a potent vasodilatory peptide, has recently been reported to be involved in the altered cardiovascular responses under various pathophysiological conditions. Although the increase in plasma AM levels is associated with upregulation of AM gene expression in various tissues, it remains unknown whether the gut is an important source of AM release under such conditions. To determine this, adult male rats were subjected to sepsis by cecal ligation and puncture (CLP) followed by fluid resuscitation. Systemic and portal blood samples were collected simultaneously at 10 and 20 h after CLP or sham operation. A portion of the jejunum was also harvested. Plasma and tissue levels of AM were then determined by RIA. The localization of AM in the intestinal tissue was examined using immunohistochemistry. In an additional group of normal rats, synthetic rat AM (8.5 microg/kg body wt) was infused for 15 min at a constant rate via the portal vein (which produces a similar level of AM as observed during sepsis). Cardiac output, stroke volume, total peripheral resistance, and microvascular blood flow in various organs were determined before and 30 min after AM administration. The results indicate that AM levels in portal blood were significantly higher than in systemic blood at 10 and 20 h after CLP. Intestinal AM was also markedly elevated. Immunohistochemical visualization shows that AM immunostainings were localized in the mucosa, submucosa, and intestinal nerve fibers, and they were increased at 10-20 h post-CLP. Because AM-immunopositive nerve fibers increase in the gut during sepsis, a nerve pathway may be involved in the regulation of vascular reactivity by this peptide. Moreover, intraportal administration of AM increased cardiac output, stroke volume, and microvascular blood flow in the liver, kidney, small intestine, and spleen. In contrast, total peripheral resistance was significantly reduced. Thus the gut plays an important role in increasing the levels of circulating AM during the progression of sepsis. Gut-derived AM appears to be a major factor in initiating the hyperdynamic response after the onset of sepsis.

The small intestine plays an important role in upregulating CGRP during sepsis

Although studies have indicated that calcitonin gene-related peptide (CGRP), a potent vasodilatory peptide, is upregulated after endotoxic shock, it remains controversial whether this peptide increases during sepsis and, if so, whether the gut is a significant source of CGRP under such conditions. To study this, polymicrobial sepsis was induced by cecal ligation and puncture (CLP) followed by fluid resuscitation. Plasma levels of CGRP were measured at 2, 5, and 10 h after CLP (i.e., early, hyperdynamic sepsis) and at 20 h after CLP (late, hypodynamic sepsis). The results indicate that plasma CGRP did not increase at 2--5 h but increased by 177% at 10 h after CLP (P < 0.05). At 20 h after the onset of sepsis, however, the elevated plasma CGRP returned to the sham level. To determine the source of the increased plasma CGRP, the liver, spleen, small intestine, lungs, and heart were harvested, and tissue CGRP was assayed at 10 h after CLP in additional animals. Only the small intestine showed a significant increase in tissue levels of CGRP (by 129%, P < 0.05). Determination of portal vs. systemic levels of CGRP indicates that portal CGRP was 65.7 +/- 22.7% higher than the systemic level at 10 h after CLP, whereas portal CGRP in sham-operated rats was only 4.9 +/- 2.1% higher. Immunohistochemistry examination revealed that CGRP-positive stainings increased in the intestinal tissue but not in the liver at 10 h after the onset of sepsis. The distribution of CGRP stainings was associated with intestinal nerve fibers. These results, taken together, demonstrate that upregulation of CGRP occurs transiently during the progression of sepsis (at the late phase of the hyperdynamic sepsis), and the gut appears to be a major source of such an increase in circulating levels of this peptide.

Gut-derived norepinephrine plays a critical role in producing hepatocellular dysfunction during early sepsis

Although plasma norepinephrine (NE) increases and hepatocellular function is depressed during early sepsis, it is unknown whether gut is a significant source of NE and, if so, whether gut-derived NE helps produce hepatocellular dysfunction. We subjected rats to sepsis by cecal ligation and puncture (CLP), and 2 h later (i.e., early sepsis) portal and systemic blood samples were collected and plasma levels of NE were assayed. Other rats were enterectomized before CLP. Hepatocellular function was assessed with an in vivo indocyanine green (ICG) clearance technique, systemic levels of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 were determined, and the effect of NE on hepatic ICG clearance capacity was assessed in an isolated, perfused liver preparation. Portal levels of NE were significantly higher than systemic levels at 2 h after CLP. Prior enterectomy reduced NE levels in septic animals. Thus gut appears to be the major source of NE release during sepsis. Enterectomy before sepsis also attenuated hepatocellular dysfunction and downregulated TNF-alpha, IL-1beta, and IL-6. Perfusion of the isolated livers with 20 nM NE (similar to that observed in sepsis) significantly reduced ICG clearance capacity. These results suggest that gut-derived NE plays a significant role in hepatocellular dysfunction and upregulating inflammatory cytokines. Modulation of NE release and/or hepatic responsiveness to NE should provide a novel approach for maintaining hepatocellular function in sepsis.