Early effects of catecholamine therapy on mucosal integrity, intestinal blood flow, and oxygen metabolism in porcine endotoxin shock

Gut-derived immune cells and the gut-lung axis in ARDS

The gut serves as a vital immunological organ orchestrating immune responses and influencing distant mucosal sites, notably the respiratory mucosa. It is increasingly recognized as a central driver of critical illnesses, with intestinal hyperpermeability facilitating bacterial translocation, systemic inflammation, and organ damage. The "gut-lung" axis emerges as a pivotal pathway, where gut-derived injurious factors trigger acute lung injury (ALI) through the systemic circulation. Direct and indirect effects of gut microbiota significantly impact immune responses. Dysbiosis, particularly intestinal dysbiosis, termed as an imbalance of microbial species and a reduction in microbial diversity within certain bodily microbiomes, influences adaptive immune responses, including differentiating T regulatory cells (Tregs) and T helper 17 (Th17) cells, which are critical in various lung inflammatory conditions. Additionally, gut and bone marrow immune cells impact pulmonary immune activity, underscoring the complex gut-lung interplay. Moreover, lung microbiota alterations are implicated in diverse gut pathologies, affecting local and systemic immune landscapes. Notably, lung dysbiosis can reciprocally influence gut microbiota composition, indicating bidirectional gut-lung communication. In this review, we investigate the pathophysiology of ALI/acute respiratory distress syndrome (ARDS), elucidating the role of immune cells in the gut-lung axis based on recent experimental and clinical research. This exploration aims to enhance understanding of ALI/ARDS pathogenesis and to underscore the significance of gut-lung interactions in respiratory diseases.

Regulatory role of Piezo1 channel in endothelium-dependent hyperpolarization-mediated vasorelaxation of small resistance vessels and its anti-inflammatory action

AIMS

Although endothelial Piezo1 channel is known to induce NO-mediated vasorelaxation of conduit vessels, it remains largely unknown if it can induce endothelial-dependent hyperpolarization (EDH)-mediated vasorelaxation of resistance vessels. Therefore, the present study aims to investigate Piezo1/EDH-mediated vasorelaxation in health and its involvement in ulcerative colitis (UC) and sepsis, two intractable and deadly inflammatory diseases.

MAIN METHODS

The tension of the second-order branch of mouse mesenteric artery was measured via the Danish DMT600M microvascular measurement system. The changes in cytoplasmic calcium ([Ca2+]cyt) signaling in vascular endothelial cells were detected by fluorescent calcium assay, and the membrane potential changes were monitored by patch clamp. Experimental murine models of UC and sepsis were induced by dextran sulfate sodium (DSS) and lipopolysaccharides (LPS), respectively.

KEY FINDINGS

A selective activator of Piezo1 channel, Yoda1, dose-dependently induced vasorelaxation of the second-order branch of mouse mesenteric artery in an endothelium-dependent manner. The endothelial Piezo1 channel mediated the vasorelaxation through EDH mechanism by a functional coupling of Piezo1 and TRPV4 channels. Their function and coupling were verified by [Ca2+]cyt imaging and patch clamp study in single endothelial cells. Moreover, while ACh-induced vasorelaxation played a major role in health, it was significantly impaired in the pathogenesis of UC and sepsis; however, Piezo1/EDH-mediated vasorelaxation remained intact. Finally, Piezo1/EDH-mediated vasorelaxation recovered ACh-induced vasorelaxation impaired in UC and sepsis.

SIGNIFICANCE

Piezo1/TRPV4/EDH-mediated vasorelaxation rescues the impaired ACh-induced vasorelaxation to likely recover hemoperfusion to organs, leading to organ protection against UC and sepsis. Our study not only suggests that endothelial Piezo1, TRPV4 and KCa channels are the potential therapeutic targets, but also implies that Piezo1 activators may benefit to prevent/treat UC and sepsis.

Immediate Norepinephrine in Endotoxic Shock: Effects on Regional and Microcirculatory Flow

OBJECTIVES

To investigate the effects of immediate start of norepinephrine versus initial fluid loading followed by norepinephrine on macro hemodynamics, regional splanchnic and intestinal microcirculatory flows in endotoxic shock.

DESIGN

Animal experimental study.

SETTING

University translational research laboratory.

SUBJECTS

Fifteen Landrace pigs.

INTERVENTIONS

Shock was induced by escalating dose of lipopolysaccharide. Animals were allocated to immediate start of norepinephrine (i-NE) ( n = 6) versus mandatory 1-hour fluid loading (30 mL/kg) followed by norepinephrine (i-FL) ( n = 6). Once mean arterial pressure greater than or equal to 75 mm Hg was, respectively, achieved, successive mini-fluid boluses of 4 mL/kg of Ringer Lactate were given whenever: a) arterial lactate greater than 2.0 mmol/L or decrease less than 10% per 30 min and b) fluid responsiveness was judged to be positive. Three additional animals were used as controls (Sham) ( n = 3). Time × group interactions were evaluated by repeated-measures analysis of variance.

MEASUREMENTS AND MAIN RESULTS

Hypotension was significantly shorter in i-NE group (7.5 min [5.5-22.0 min] vs 49.3 min [29.5-60.0 min]; p < 0.001). Regional mesenteric and microcirculatory flows at jejunal mucosa and serosa were significantly higher in i-NE group at 4 and 6 hours after initiation of therapy ( p = 0.011, p = 0.032, and p = 0.017, respectively). Misdistribution of intestinal microcirculatory blood flow at the onset of shock was significantly reversed in i-NE group ( p < 0.001), which agreed with dynamic changes in mesenteric-lactate levels ( p = 0.01) and venous-to-arterial carbon dioxide differences ( p = 0.001). Animals allocated to i-NE showed significantly higher global end-diastolic volumes ( p = 0.015) and required significantly less resuscitation fluids ( p < 0.001) and lower doses of norepinephrine ( p = 0.001) at the end of the experiment. Pulmonary vascular permeability and extravascular lung water indexes were significantly lower in i-NE group ( p = 0.021 and p = 0.004, respectively).

CONCLUSIONS

In endotoxemic shock, immediate start of norepinephrine significantly improved regional splanchnic and intestinal microcirculatory flows when compared with mandatory fixed-dose fluid loading preceding norepinephrine. Immediate norepinephrine strategy was related with less resuscitation fluids and lower vasopressor doses at the end of the experiment.

Identification of Perioperative Procedural and Hemodynamic Risk Factors for Developing Colonic Ischemia after Ruptured Infrarenal Abdominal Aortic Aneurysm Surgery: A Single-Centre Retrospective Cohort Study

(1) Background: This retrospective study evaluated perioperative and intensive care unit (ICU) variables to predict colonic ischemia (CI) after infrarenal ruptured abdominal aortic aneurysm (RAAA) surgery. (2) Materials and Methods: We retrospectively analyzed the data of the patients treated for infrarenal RAAA from January 2011 to December 2020 in our hospital. (3) Results: A total of 135 (82% male) patients were admitted to ICU after treatment of infrarenal RAAA. The median age of all patients was 75 years (IQR 68-81 years). Of those, 24 (18%) patients developed CI, including 22 (92%) cases within the first three postoperative days. CI was found more often after open repair compared to endovascular treatment (22% vs. 5%, p = 0.021). Laboratory findings in the first seven PODs revealed statistically significant differences between CI and non-CI patients for serum lactate, minimum pH, serum bicarbonate, and platelet count. Norepinephrine (NE) was used in 92 (68%) patients during ICU stay. The highest daily dose of norepinephrine was administered to CI patients at POD1. Multivariable analysis revealed that NE > 64 µg/kg (RD 0.40, 95% CI: 0.25-0.55, p < 0.001), operating time ≥ 200 min (RD 0.18, 95% CI: 0.05-0.31, p = 0.042), and pH < 7.3 (RD 0.21, 95% CI: 0.07-0.35, p = 0.019), significantly predicted the development of CI. A total of 23 (17%) patients died during the hospital stay, including 8 (33%) patients from the CI group and 15 (7%) from the non-CI group (p = 0.032). (4) Conclusions: CI after RAAA is a sever complication occurring most frequently within the first 3 postoperative days. Our study identified many surrogate markers associated with colonic ischemia after aortic RAAA, including norepinephrine dose > 64 µg/kg, operating time ≥ 200 min, and PH < 7.3. Future studies are needed to support these results.

From a pressure-guided to a perfusion-centered resuscitation strategy in septic shock: Critical literature review and illustrative case

PURPOSE

To support a paradigm shift in the management of septic shock from pressure-guided to perfusion-centered, expected to improve outcome while reducing adverse effects from vasopressor therapy and aggressive fluid resuscitation.

MATERIAL AND METHODS

Critical review of the literature cited in support of vasopressor use to achieve a predefined mean arterial pressure (MAP) of 65 mmHg and review of pertinent clinical trials and studies enabling deeper understanding of the hemodynamic pathophysiology supportive of a perfusion-centered approach, accompanied by an illustrative case.

RESULTS

Review of the literature cited by the Surviving Sepsis Campaign revealed lack of controlled clinical trials supporting outcome benefits from vasopressors. Additional literature review revealed adverse effects associated with vasopressors and worsened outcome in some studies. Vasopressors increase MAP primarily by peripheral vasoconstriction and in occasions by a modest increase in cardiac output when using norepinephrine. Thus, achieving the recommended MAP of 65 mmHg using vasopressors should not be presumed indicative that organ perfusion has been restored. It may instead create a false sense of hemodynamic stability hampering shock resolution.

CONCLUSIONS

We propose focusing the hemodynamic management of septic shock on reversing organ hypoperfusion instead of attaining a predefined MAP target as the key strategy for improving outcome.

Increased Intraoperative Vasopressor Use as Part of an Enhanced Recovery After Surgery Pathway for Pancreatectomy Does Not Increase Risk of Pancreatic Fistula

Purpose: Enhanced recovery after surgery (ERAS) pathways are increasingly implemented. Goal directed fluid therapy (GDFT) is a core component of ERAS pathways that limit excessive volume administration and is associated with increased use of intraoperative vasopressors. Vasopressor effects on anastomotic healing and pancreatic fistula are inconclusive. We hypothesized that intraoperative vasopressor use in an ERAS GDFT algorithm would not increase risk of pancreatic fistulas. Methods: We reviewed all adult patients undergoing pancreatectomy at an academic institution from January 2013 to February 2016, before and after implementation of an ERAS pathway in July 2014. Retrospective chart review was performed. Log-binomial regression, weighted by stabilized inverse probability-of-treatment weights, estimated effect of ERAS and intraoperative vasopressors on fistula risk. Results: One hundred thirty two patients met inclusion criteria: 74 (56.1%) in the ERAS cohort. No significant differences in overall leak risk (risk ratio [RR] 0.89, 95% confidence interval [CI] 0.38-2.09) were observed between the ERAS and pre-ERAS cohorts. Similarly, vasopressor infusions, independent of ERAS pathway, did not significantly increase the risk of anastomotic leaks (RR 1.19, 95% CI 0.52-2.72). Conclusions: Increased use of vasopressor infusions as part of an ERAS pathway for pancreatic surgery is not associated with an increase in the risk of clinically significant pancreatic fistulas.

Effects of ATP-sensitive potassium channel blockers on vascular hyporeactivity, mesenteric blood flow, and survival in lipopolysaccharide-induced septic shock model

In this study, the possible therapeutic effects of various ATP-sensitive potassium channel (KATP) blockers (glibenclamide, repaglinide, 5-HD, HMR-1098) have been tested in experimental septic shock model. Rats were given lipopolysaccharide (1 mg·kg−1) to create experimental shock model and 4 h later, under 400 mg·kg−1 chloral hydrate anesthesia, parameters such as blood pressure, mesenteric blood flow, the response of mesenteric circulation to phenylephrine (vasoconstrictor stimulation), and organ and oxidative damage were analyzed. Also 75 mg·kg−1 lethal dose of lipopolysaccharide was given to mice and effects of KATP blockers on survival have been tested. Non-selective blocker glibenclamide with sulphonylurea structure and sarcolemmal KATP channel blocker HMR-1098, which have the similar chemical structure, have improved the pathological parameters such as decrease in mesenteric blood flow, vascular hyporeactivity, but could not prevent the decrease in blood pressure, and oxidative and organ damage that were observed in the shock model. Also, both blockers have decreased the mortality rate from 80% to 40%–50%. Similar (preventive) therapeutic effects were not observed with non-selective blocker repaglinide and mitochondrial KATP channel blocker 5-HD, which were non-sulphonylurea structure. As a result, only KATP channel blockers that have sulphonylurea structure can be a new therapeutic approach in septic shock.

Catecholamine use is associated with enterocyte damage in critically ill patients

Small bowel damage is frequent but underdiagnosed among critically ill patients with shock. High catecholamine doses may have a deleterious effect on mesenteric blood flow. Plasma intestinal fatty acid-binding protein (I-FABP) concentration is a marker of enterocyte damage, whereas plasma citrulline concentration is a marker of functional enterocyte mass. We hypothesized that high doses of catecholamines in critically ill patients may be associated with enterocyte damage. This study aimed to determine the link between catecholamine use and dose with enterocyte damage. This is a prospective observational study performed in a large regional university teaching hospital. Critically ill patients requiring epinephrine and/or norepinephrine at admission to a medical intensive care unit (ICU) were included, as well as controls not receiving catecholamines. We evaluated at admission plasma I-FABP and citrulline concentrations, abdominal perfusion pressure (APP), and variables relating to prognosis and treatment. Patients were categorized according to the quartiles of catecholamine dose at ICU admission. Sixty critically ill patients receiving catecholamines and 27 not receiving catecholamines were included. Plasma I-FABP was higher among patients receiving catecholamine than in controls. Among patients receiving catecholamines, a dose of 0.48 γ kg min or more at ICU admission was associated with a higher I-FABP concentration. A Sepsis-related Organ Failure Assessment score higher than 11 and plasma I-FABP more than 524 pg mL at ICU admission were independently associated with 28-day mortality (odds ratio, 4.0 [1.24-12.95] and odds ratio, 4.90 [1.44-16.6], respectively). Catecholamine use is associated with I-FABP elevation in critically ill patients. Critically ill patients receiving more than 0.48 γ kg min of epinephrine and/or norepinephrine at ICU admission have high I-FABP concentrations. This suggests that enterocyte damage reflects the severity of shock, and an adverse effect of catecholamines per se is possible.

Feeding the Postoperative Patient on Vasopressor Support: Feeding and Pressor Support

Initiating enteral nutrition in the postoperative patient can be challenging. Postoperative ileus and bowel edema, bowel anastomosis, and intra-abdominal pathology contribute to the reluctance and inability to achieve adequate nutrition in this patient population. The addition of vasopressors confounds the difficulties. Clinical data are sparse but suggest that most postoperative patients requiring vasopressor therapy can be safely initiated and advanced on enteral nutrition. Consideration of the vasopressor agent being utilized and its dose is imperative, as are individual patient characteristics. Temporal changes in the dosage should be closely monitored, as increasing doses may reflect worsening clinical status that can be due to intestinal ischemia. Well-designed prospective trials are clearly necessary to address this controversial topic.

Gut failure in critical care: old school versus new school

The concept of bacterial translocation and gut-origin sepsis as causes of systemic infectious complications and multiple organ deficiency syndrome in surgical and critically ill patients has been a recurring issue over the last decades attracting the scientific interest. Although gastrointestinal dysfunction seemingly arises frequently in intensive care unit patients, it is usually underdiagnosed or underestimated, because the pathophysiology involved is incompletely understood and its exact clinical relevance still remains controversial with an unknown yet probably adverse impact on the patients' outcome. The purpose of this review is to define gut-origin sepsis and related terms, to describe the mechanisms leading to gut-derived complications, and to illustrate the therapeutic options to prevent or limit these untoward processes.

Rhein inhibits lipopolysaccharide-induced intestinal injury during sepsis by blocking the toll-like receptor 4 nuclear factor-κB pathway

Sepsis is one of the leading causes of mortality in severe systemic inflammatory syndrome. The endotoxin-induced inflammatory response has been linked to the development of sepsis. Rhein is a lipophilic anthraquinone isolated from Rheum rhabarbarum (rhubarb), which has a protective effect on intestinal damage in vivo. However, the underlying mechanism responsible for the protective effects of rhein remains to be elucidated. In the present study, mice were exposed to 20 mg/kg lipopolysaccharide (LPS), prior to being treated with either 100 mg/kg rhein or 0.3 mg/kg toll‑like receptor 4 (TLR4) signaling inhibitor TAK‑242. In the rhein‑treated mice, the colon length (cm) was extended and colon injury was attenuated. In addition, treatment with rhein significantly decreased the expression levels of the LPS‑induced inflammatory cytokines interleukin (IL)‑1β, IL‑6, IL‑8, and tumor necrosis factor‑α, in both the plasma and colon tissue. However, mice treated with TAK‑242 exhibited increased expression levels of IL‑10, as determined by ELISA and western blot analysis. In addition, immunohistochemistry and western blot analyses demonstrated that treatment with rhein was able to reduce TLR4 expression and inhibit nuclear factor‑κB (NF‑κB) phosphorylation in colon tissue. Furthermore, LPS induction was blocked by TAK‑242. These results demonstrate that the observed rhein‑attenuated inflammatory response during sepsis may be achieved via the TLR4 NF‑κB signaling pathway. In conclusion, the results of the present study provide a novel insight into the protective effects of rhein on LPS‑induced intestinal inflammation, and demonstrate that rhein may act as a beneficial therapeutic agent in the treatment of sepsis-induced intestinal damage.

Blockade or deletion of transient receptor potential vanilloid 4 (TRPV4) is not protective in a murine model of sepsis

Sepsis is a systemic inflammatory response triggered by microbial infection that can cause cardiovascular collapse, insufficient tissue perfusion and multi-organ failure. The cation channel transient receptor potential vanilloid 4 (TRPV4) is expressed in vascular endothelium and causes vasodilatation, but excessive TRPV4 activation leads to profound hypotension and circulatory collapse - key features of sepsis pathogenesis. We hypothesised that loss of TRPV4 signaling would protect against cardiovascular dysfunction in a mouse model of sepsis (endotoxaemia). Multi-parameter monitoring of conscious systemic haemodynamics (by radiotelemetry probe), mesenteric microvascular blood flow (laser speckle contrast imaging) and blood biochemistry (iSTAT blood gas analysis) was carried out in wild type (WT) and TRPV4 knockout (KO) mice. Endotoxaemia was induced by a single intravenous injection of lipopolysaccharide (LPS; 12.5 mg/kg) and systemic haemodynamics monitored for 24 h. Blood flow recording was then conducted under terminal anaesthesia after which blood was obtained for haematological/biochemical analysis. No significant differences were observed in baseline haemodynamics or mesenteric blood flow. Naïve TRPV4 KO mice were significantly acidotic relative to WT counterparts. Following induction of sepsis, all mice became significantly hypotensive, though there was no significant difference in the degree of hypotension between TRPV4 WT and KO mice. TRPV4 KO mice exhibited a higher sepsis severity score. While septic WT mice became significantly hypernatraemic relative to the naïve state, this was not observed in septic KO mice. Mesenteric blood flow was inhibited by topical application of the TRPV4 agonist GSK1016790A in naïve WT mice, but enhanced 24 h following LPS injection. Contrary to the initial hypothesis, loss of TRPV4 signaling (either through gene deletion or pharmacological antagonism) did not attenuate sepsis-induced cardiovascular dysfunction: in fact, pathology appeared to be modestly exaggerated in mice lacking TRPV4. Local targeting of TRPV4 signalling may be more beneficial than global inhibition in sepsis treatment.

Quantification of microcirculatory blood flow: a sensitive and clinically relevant prognostic marker in murine models of sepsis

Sepsis and sepsis-associated multiorgan failure represent the major cause of mortality in intensive care units worldwide. Cardiovascular dysfunction, a key component of sepsis pathogenesis, has received much research interest, although research translatability remains severely limited. There is a critical need for more comprehensive preclinical sepsis models, with more clinically relevant end points, such as microvascular perfusion. The purpose of this study was to compare microcirculatory blood flow measurements, using a novel application of laser speckle contrast imaging technology, with more traditional hemodynamic end points, as part of a multiparameter monitoring system in preclinical models of sepsis. Our aim, in measuring mesenteric blood flow, was to increase the prognostic sensitivity of preclinical studies. In two commonly used sepsis models (cecal ligation and puncture, and lipopolysaccharide), we demonstrate that blood pressure and cardiac output are compromised postsepsis, but subsequently stabilize over the 24-h recording period. In contrast, mesenteric blood flow continuously declines in a time-dependent manner and in parallel with the development of metabolic acidosis and organ dysfunction. Importantly, these microcirculatory perturbations are reversed by fluid resuscitation, a mainstay intervention associated with improved outcome in patients. These data suggest that global hemodynamics are maintained at the expense of the microcirculation and are, therefore, not sufficiently predictive of outcome. We demonstrate that microcirculatory blood flow is a more sensitive biomarker of sepsis syndrome progression and believe that incorporation of this biomarker into preclinical models will facilitate sophisticated proof-of-concept studies for novel sepsis interventions, providing more robust data on which to base future clinical trials.

Techniques to assess tissue oxygenation in the clinical setting

The microcirculation plays an essential role in health and disease. Microvascular perfusion can be assessed directly using laser Doppler flowmetry and various imaging techniques or indirectly using regional capnometry and measurement of indicators of mismatch between oxygen delivery and oxygen consumption or indices of disturbed cellular oxygen utilization. Assessment of microvascular oxygen availability implies measurement of oxygen pressure or measurement of hemoglobin oxygen saturation. Microvascular function is assessed using other methods, including venous plethysmography. In this paper, I review current knowledge concerning assessment of the microcirculation with special emphasis on methods that could be used at the bedside.

Norepinephrine to increase blood pressure in endotoxaemic pigs is associated with improved hepatic mitochondrial respiration

Introduction

Low blood pressure, inadequate tissue oxygen delivery and mitochondrial dysfunction have all been implicated in the development of sepsis-induced organ failure. This study evaluated the effect on liver mitochondrial function of using norepinephrine to increase blood pressure in experimental sepsis.

Methods

Thirteen anaesthetized pigs received endotoxin (Escherichia coli lipopolysaccharide B0111:B4; 0.4 μg/kg per hour) and were subsequently randomly assigned to norepinephrine treatment or placebo for 10 hours. Norepinephrine dose was adjusted at 2-hour intervals to achieve 15 mmHg increases in mean arterial blood pressure up to 95 mmHg. Systemic (thermodilution) and hepatosplanchnic (ultrasound Doppler) blood flow were measured at each step. At the end of the experiment, hepatic mitochondrial oxygen consumption (high-resolution respirometry) and citrate synthase activity (spectrophotometry) were assessed.

Results

Mean arterial pressure (mmHg) increased only in norepinephrine-treated animals (from 73 [median; range 69 to 81] to 63 [60 to 68] in controls [P = 0.09] and from 83 [69 to 93] to 96 [86 to 108] in norepinephrine-treated animals [P = 0.019]). Cardiac index and systemic oxygen delivery (DO₂) increased in both groups, but significantly more in the norepinephrine group (P < 0.03 for both). Cardiac index (ml/min per·kg) increased from 99 (range: 72 to 112) to 117 (110 to 232) in controls (P = 0.002), and from 107 (84 to 132) to 161 (147 to 340) in norepinephrine-treated animals (P = 0.001). DO₂ (ml/min per·kg) increased from 13 (range: 11 to 15) to 16 (15 to 24) in controls (P = 0.028), and from 16 (12 to 19) to 29 (25 to 52) in norepinephrine-treated animals (P = 0.018). Systemic oxygen consumption (systemic VO₂) increased in both groups (P < 0.05), whereas hepatosplanchnic flows, DO₂ and VO₂ remained stable. The hepatic lactate extraction ratio decreased in both groups (P = 0.05). Liver mitochondria complex I-dependent and II-dependent respiratory control ratios were increased in the norepinephrine group (complex I: 3.5 [range: 2.1 to 5.7] in controls versus 5.8 [4.8 to 6.4] in norepinephrine-treated animals [P = 0.015]; complex II: 3.1 [2.3 to 3.8] in controls versus 3.7 [3.3 to 4.6] in norepinephrine-treated animals [P = 0.09]). No differences were observed in citrate synthase activity.

Conclusion

Norepinephrine treatment during endotoxaemia does not increase hepatosplanchnic flow, oxygen delivery or consumption, and does not improve the hepatic lactate extraction ratio. However, norepinephrine increases the liver mitochondria complex I-dependent and II-dependent respiratory control ratios. This effect was probably mediated by a direct effect of norepinephrine on liver cells.

NOREPINEPHRINE AND INTESTINAL MUCOSAL PERFUSION IN VASODILATORY SHOCK AFTER CARDIAC SURGERY

Patients with norepinephrine-dependent vasodilatory shock after cardiac surgery (n = 10) were compared with uncomplicated postcardiac surgery patients (n = 10) with respect to jejunal mucosal perfusion, gastric-arterial PCO2 gradient, and splanchnic oxygen demand/supply relationship. Furthermore, the effects of norepinephrine-induced variations in MAP on these variables were evaluated in vasodilatory shock. Norepinephrine infusion rate was randomly and sequentially titrated to target MAPs of 60, 75, and 90 mmHg (0.25 +/- 0.24, 0.37 +/- 0.21, and 0.55 +/- 0.39 microg/kg per minute, respectively). Data on jejunal mucosal perfusion, jejunal mucosal hematocrit, and red blood cell (RBC) velocity (laser Doppler flowmetry) as well as gastric-arterial PCO2 gradient (gastric tonometry) and splanchnic oxygen and lactate extraction (hepatic vein catheter) were obtained. Splanchnic oxygen extraction was 71 +/- 16% in the vasodilatory shock group and 41 +/- 9% in the control group (P < 0.001), whereas splanchnic lactate extraction did not differ between the two groups. Jejunal mucosal perfusion (61%; P < 0.001), RBC velocity (35%; P < 0.01), and gastric-arterial mucosal PCO2 gradient (150%; P < 0.001) were higher in the vasodilatory shock group compared with those of the control group. Jejunal mucosal perfusion, jejunal mucosal hematocrit, RBC velocity, gastric-arterial mucosal PCO2 gradient, splanchnic oxygen extraction, and splanchnic lactate extraction were not affected by increasing infusion rates of norepinephrine. In patients with norepinephrine-dependent vasodilatory shock after cardiac surgery, intestinal mucosal perfusion was higher, whereas splanchnic and gastric oxygen demand/supply relationships were impaired compared with postoperative controls, suggesting that intestinal mucosal perfusion is prioritized in vasodilatory shock. Increasing MAP from 60 to 90 mmHg with norepinephrine in clinical vasodilatory shock does not affect intestinal mucosal perfusion and gastric or global splanchnic oxygen demand/supply relationships.

Norepinephrine increases tolerance to acute anemia

OBJECTIVE

Extreme anemia threatens myocardial oxygen supply by 1) a decline of arterial oxygen content and 2) by a decline of mean aortic pressure (MAP) and thus coronary perfusion pressure. Standard treatment of low arterial oxygen content includes ventilation with pure oxygen and the transfusion of red blood cells. However, it is unknown whether the stabilization of MAP and coronary perfusion pressure with norepinephrine as the sole therapeutic modality may also increase tolerance to extreme anemia and thus improve outcome.

DESIGN

Prospective, randomized, controlled study.

SETTING

Experimental animal laboratory of a university hospital.

SUBJECTS

A total of 28 anesthetized, mechanically ventilated pigs.

INTERVENTIONS AND MEASUREMENTS

In the first protocol, 14 anesthetized pigs were hemodiluted by exchange of whole blood for 6% hydroxyethyl starch (200,000:0.5) until the individual critical hemoglobin concentration was reached. For the next 6 hrs, animals were either observed without any further intervention (control group) or their MAP was maintained by adapted infusion of norepinephrine (norepinephrine group). The main outcome variable of this protocol was the 6-hr mortality in both groups. In the second protocol, 14 anesthetized pigs received hemodilution until death. In seven animals, no intervention was performed during the hemodilution procedure, whereas in the other seven animals, MAP was maintained at >60 mm Hg by adapted infusion of norepinephrine. The main outcome variable of this protocol was the maximum exchangeable blood volume until death.

MAIN RESULTS

MAP stabilization with norepinephrine reduced the 6-hr mortality at the critical hemoglobin concentration from 100% to 14%. Maintaining MAP by adapted norepinephrine infusion during the hemodilution procedure allowed for the exchange of 125 (110/126) (median [quartile 1/quartile 3]) mL/kg blood (163% of blood volume) in the norepinephrine group, whereas only 76 (73/91) mL/kg blood (104% of blood volume) could be exchanged in the control group.

CONCLUSIONS

Application of norepinephrine can be judged a first-line intervention to bridge acute anemia via a stabilization of MAP and coronary perfusion pressure. However, due to the relevant side effects of norepinephrine, its sole long-term use during extreme anemia without concomitant transfusion of erythrocytes is not advised.

Perioperative Vasopressors Are Associated with an Increased Risk of Gastrointestinal Anastomotic Leakage

BACKGROUND

The purpose of this study was to investigate the effect of vasopressors on gastrointestinal (GI) anastomotic leaks. Vasopressors are commonly used in surgical patients admitted to the intensive care unit (ICU) and their effects on GI anastomotic integrity are unknown.

PATIENTS AND METHODS

Surgical patients admitted to the ICU in our tertiary university hospital following the creation of a GI anastomosis were studied by a retrospective chart analysis for anastomotic leaks and complications

RESULTS

A total of 223 patients with 259 GI anastomoses, mostly for cancer, were admitted to the ICU immediately after surgery. Twenty-two patients developed anastomotic leaks (9.9%). The two groups (leak versus no-leak) had similar demographics, surgery type and indication, type of anastomosis, co-morbidities, cancer, steroid use, blood transfusion, drains, and epidural catheters. Vasopressor use was associated with increased anastomotic leakage (p = 0.02, OR 3.25). Multiple vasopressors and prolonged exposure caused even higher leaking rates. This effect was independent of the medical status and operative morbidity (APACHE II, POSSUM). Blood pressure preceding vasopressor use was similar in both groups. Vasopressors might have been occasionally used to treat hypovolemia. Patients with leaks had higher reoperation rates (41% versus 1%, p < 0.0001) and mortality (21% versus 4%, p = 0.002).

CONCLUSIONS

Vasopressors appear to increase anastomotic leaks threefold, independent of clinical/surgical status or hypotension. Evidence-based guidelines are warranted for the optimal use of vasopressors in postoperative patients admitted to the ICU.

Effects of AM281, a cannabinoid antagonist, on circulatory deterioration and cytokine production in an endotoxin shock model: comparison with norepinephrine

PURPOSE

The purpose of this study was to examine the comparative effects of AM281, a cannabinoid antagonist, and norepinephrine (NE) on systemic hemodynamics, and renal and mesenteric artery blood flow in an endotoxin shock model.

METHODS

The study was designed to include two sets of experiments: (1) measurements of changes in systemic hemodynamics and organ artery blood flows (n = 20), and (2) measurements of biochemical variables (n = 20). For each set of experiments, male 7-week-old Wistar rats were randomly divided into four groups: group 1, controls (n = 5); group 2, receiving lipopolysaccharide (LPS: Escherichia coli endotoxin, 10.0 mg.kg(-1) intravenous bolus) (n = 5); group 3, receiving intravenous LPS and NE (continuous infusion at 0.2 microg.kg.min(-1)) (n = 5); group 4, receiving LPS and AM281 (0.1 mg.kg.min(-1)) (n = 5). Systemic hemodynamics, regional artery blood flow changes, and biochemical variables were assessed before treatment and 1 and 3 h after treatment.

RESULTS

Infusion of NE or AM281 prevented endotoxin-induced decreases in systemic arterial pressure, aortic blood flow, carotid artery blood flow, and renal artery blood flow. Both AM281 and NE inhibited endotoxin-induced increases in cytokine production, with significant differences observed among the three groups at 1 and 3 h after treatment. Endotoxin-induced decreases in mesenteric arterial blood flow were restored by AM281 but not by NE. AM281 improved arterial oxygenation and reduced lactate overproduction and body temperature elevation induced by endotoxin.

CONCLUSIONS

Although NE and AM281 both prevented endotoxin-induced deterioration of systemic hemodynamics, AM281 yielded better preservation of mesenteric blood flow and attenuation of cytokine production than NE.

Increasing cardiac output by epinephrine after cardiac surgery: effects on indocyanine green plasma disappearance rate and splanchnic microcirculation

OBJECTIVE

The effects of increasing cardiac output by epinephrine on indocyanine green plasma disappearance rate (ICG-PDR) and gastric mucosal PCO(2) (P(R)CO(2)) were studied as indicators of splanchnic microcirculation.

DESIGN

A prospective clinical study.

SETTING

Intensive care unit of a university hospital.

PARTICIPANTS

With ethics approval and written consent, 12 elective cardiac surgical patients (5 female, 7 male, 71 +/- 8 years) were studied.

INTERVENTIONS

Patients underwent pulmonary artery and left atrial catheterization for clinical indications. Measurements were made at intensive care unit admission and 1 hour after (increased) epinephrine treatment. Mean epinephrine dose was changed from 0.02 to 0.08 microg/kg/min.

RESULTS

Heart rate significantly increased from 97 +/- 11 to 106 +/- 12 beat/min. Central venous (10 +/- 3 v 10 +/- 4 mmHg) and left atrial (10 +/- 5 v 11 +/- 5 mmHg) pressures were unchanged. Cardiac index and stroke volume index significantly increased from 2.7 +/- 0.5 to 3.2 +/- 0.5 L/min/m(2) and from 28 +/- 6 to 31 +/- 5 mL/m(2), respectively. Although systemic O(2) delivery and O(2) consumption significantly increased, ICG-PDR did not change significantly (ie, from 18.0% +/- 5.6% to 19.5% +/- 6.4% per minute). P(R)CO(2) and PCO(2) gap (difference between regional and end-tidal PCO(2)) significantly increased from 5.4 +/- 1.0 to 5.9 +/- 1.1 kPa and 1.2 +/- 0.8 to 1.5 +/- 0.7 kPa, respectively.

CONCLUSION

Increasing cardiac output by epinephrine in patients after cardiac surgery was not associated with a change in flow-dependent liver function but a deterioration in gastric mucosal perfusion.

Effects of levosimendan in normodynamic endotoxaemia: a controlled experimental study

OBJECTIVES

Levosimendan is an inotropic and vasodilator drug that has proved to be useful in cardiogenic shock. Pretreatment with levosimendan in experimental hypodynamic septic shock in pigs has shown valuable effects in oxygen transport. Our goal was to assess the effects of levosimendan in a normodynamic model of endotoxaemia.

METHODS

Twelve sheep were anaesthetized and mechanically ventilated. After taking basal haemodynamic and oxygen transport measurements, sheep were assigned to two groups during 120 min: (1) endotoxin (5 microg/kg endotoxin); (2) levosimendan (5 microg/kg endotoxin plus levosimendan 200 microg/kg followed by 200 microg/kg/h). Both groups received hydration of 20 ml/kg/h of saline solution.

RESULTS

In the endotoxin group, cardiac output, intestinal blood flow and systemic and intestinal oxygen transports and consumptions (DO(2) and VO(2)) remained unchanged. In the levosimendan group, systemic and intestinal DO(2) were significantly higher than in the endotoxin group. Because stroke volume did not change (basal versus 120': 0.9+/-0.1 ml/kg versus 0.9+/-0.2 ml/kg, p=0.3749), the elevation in cardiac output by levosimendan (145+/-17 ml/min/kg versus 198+/-16 ml/min/kg, p=0.0096) was related to an increased heart rate (159+/-32 beats l/min versus 216+/-19 beats l/min, p=0.0037). Levosimendan precluded the development of gut intramucosal acidosis at 120' (endotoxin versus levosimendan, ileal intramucosal-arterial PCO(2) difference: 19+/-4 Torr versus 10+/-4 Torr, p=0.0025). However, levosimendan decreased mean arterial blood pressure (99+/-20 Torr versus 63+/-13 Torr, p=0.0235) and increased blood lactate levels (2.4+/-0.9 mmol/l versus 4.8+/-1.5 mmol/l, p=0.0479). All p-values are differences in specific points (paired or unpaired t-test with Bonferroni correction) after two-way repeated measures ANOVA. A p-value<0.05 was considered significant.

CONCLUSIONS

Levosimendan improved oxygen transport and prevented the development of intramucosal acidosis in this experimental model of endotoxaemia. However, systemic hypotension and lactic acidosis occurred. Additional studies are needed to show if different doses and timing of levosimendan administration in septic shock might improve gut perfusion without adverse effects.

Effects of epinephrine, norepinephrine, and phenylephrine on microcirculatory blood flow in the gastrointestinal tract in sepsis*

OBJECTIVE

The use of vasopressors for treatment of hypotension in sepsis may have adverse effects on microcirculatory blood flow in the gastrointestinal tract. The aim of this study was to measure the effects of three vasopressors, commonly used in clinical practice, on microcirculatory blood flow in multiple abdominal organs in sepsis.

DESIGN

Random order, cross-over design.

SETTING

University laboratory.

SUBJECTS

Eight sedated and mechanically ventilated pigs.

INTERVENTIONS

Pigs were exposed to fecal peritonitis-induced septic shock. Mesenteric artery flow was measured using ultrasound transit time flowmetry. Microcirculatory flow was measured in gastric, jejunal, and colon mucosa; jejunal muscularis; and pancreas, liver, and kidney using multiple-channel laser Doppler flowmetry. Each animal received a continuous intravenous infusion of epinephrine, norepinephrine, and phenylephrine in a dose increasing mean arterial pressure by 20%. The animals were allowed to recover for 60 mins after each drug before the next was started.

MEASUREMENTS AND MAIN RESULTS

During infusion of epinephrine (0.8 +/- 0.2 mug/kg/hr), mean arterial pressure increased from 66 +/- 5 to 83 +/- 5 mm Hg and cardiac index increased by 43 +/- 9%. Norepinephrine (0.7 +/- 0.3 mug/kg/hr) increased mean arterial pressure from 70 +/- 4 to 87 +/- 5 mm Hg and cardiac index by 41 +/- 8%. Both agents caused a significant reduction in superior mesenteric artery flow (11 +/- 4%, p < .05, and 26 +/- 6%, p < .01, respectively) and in microcirculatory blood flow in the jejunal mucosa (21 +/- 5%, p < .01, and 23 +/- 3%, p < .01, respectively) and in the pancreas (16 +/- 3%, p < .05, and 8 +/- 3%, not significant, respectively). Infusion of phenylephrine (3.1 +/- 1.0 mug/kg/min) increased mean arterial pressure from 69 +/- 5 to 85 +/- 6 mm Hg but had no effects on systemic, regional, or microcirculatory flow except for a 30% increase in jejunal muscularis flow (p < .01).

CONCLUSIONS

Administration of the vasopressors phenylephrine, epinephrine, and norepinephrine failed to increase microcirculatory blood flow in most abdominal organs despite increased perfusion pressure and-in the case of epinephrine and norepinephrine-increased systemic blood flow. In fact, norepinephrine and epinephrine appeared to divert blood flow away from the mesenteric circulation and decrease microcirculatory blood flow in the jejunal mucosa and pancreas. Phenylephrine, on the other hand, appeared to increase blood pressure without affecting quantitative blood flow or distribution of blood flow.

Vasopressors and intestinal mucosal perfusion after cardiac surgery: Norepinephrine vs. phenylephrine

OBJECTIVES

To evaluate the potential differential effects of norepinephrine, an alpha1-, beta1-, and beta2-receptor agonist, to the alpha1-agonist phenylephrine on jejunal mucosal perfusion, gastric-arterial PCO2 gradient, and the global splanchnic oxygen demand-supply relationship after cardiac surgery.

DESIGN

A randomized, prospective, interventional crossover study.

SETTING

A university cardiothoracic intensive care unit.

PATIENTS

Ten patients were studied during propofol sedation and mechanical ventilation after uncomplicated coronary artery bypass surgery.

INTERVENTIONS

Each patient received randomly and sequentially norepinephrine (0.052+/-0.009 microg/kg/min) and phenylephrine (0.50+/-0.22 microg/kg/min) to increase mean arterial blood pressure by 30%.

MEASUREMENTS AND MAIN RESULTS

Data on jejunal mucosal perfusion, jejunal mucosal hematocrit, and red blood cell velocity (laser Doppler flowmetry) as well as gastric-arterial Pco2 gradient (tonometry) and splanchnic oxygen extraction were obtained before (control) and during a 30-min drug infusion period after the target mean arterial blood pressure was reached. The procedure was sequentially repeated for the second vasopressor. Both drugs induced a 40-46% increase in systemic vascular resistance with no change in cardiac index. Neither jejunal mucosal perfusion, jejunal mucosal hematocrit, red blood cell velocity, nor gastric-arterial Pco2 gradient was affected by any of the vasopressors. Splanchnic oxygen extraction increased from 38.2% to 43.1% (p<.001) with norepinephrine and from 39.3% to 47.5% (p<.001) with phenylephrine. This increase was significantly more pronounced with phenylephrine compared with norepinephrine (p<.05). Mixed venous-hepatic vein oxygen saturation gradient increased with both drugs (p<.01), and the increase was more pronounced with phenylephrine (p<.05). Splanchnic lactate extraction was not significantly affected by any of the vasopressors.

CONCLUSIONS

Phenylephrine induced a more pronounced global alpha1-mediated splanchnic vasoconstriction compared with norepinephrine. Neither of the vasoconstrictors impaired perfusion of the gastrointestinal mucosa in postcardiac surgery patients. The lack of norepinephrine-induced, alpha1-mediated impairment of gastrointestinal perfusion is not explained by a beta2-mediated counteractive vasodilation but instead by possible mucosal autoregulatory escape.

Effect of increased cardiac output on hepatic and intestinal microcirculatory blood flow, oxygenation, and metabolism in hyperdynamic murine septic shock

OBJECTIVE

Septic shock-associated organ dysfunction is attributed to derangements of microcirculatory perfusion and/or impaired cellular oxygen utilization. The hepatosplanchnic organs are regarded to play a pivotal role in the pathophysiology of sepsis-related organ failure. In a murine model of septic shock, we tested the hypothesis whether achieving normotensive, hyperdynamic hemodynamics characterized by a sustained increase in cardiac output would allow maintenance of regional microvascular perfusion and oxygenation and, thus, hepatic metabolic capacity.

DESIGN

Prospective, controlled, randomized animal study.

SETTING

University animal research laboratory.

SUBJECTS

Male C57Bl/6 mice.

INTERVENTIONS

Fifteen hours after sham operation (n = 11) or cecal ligation and puncture (CLP) (n = 9), mice were anesthetized, mechanically ventilated, and instrumented (central venous and left ventricular pressure-conductance catheter, portal vein and superior mesenteric artery ultrasound flow probes). Animals received continuous intravenous hydroxyethylstarch and norepinephrine to achieve normotensive and hyperdynamic hemodynamics, and glucose was infused to maintain normoglycemia.

MEASUREMENTS AND MAIN RESULTS

Measurements were recorded 18, 21, and 24 hrs post-CLP. In CLP mice, titration of hemodynamic targets were affiliated superior mesenteric artery and portal vein flow. Using a combined laser-Doppler flowmetry and remission spectrophotometry probe, we found well-maintained gut and liver capillary perfusion as well as intestinal microcirculatory hemoglobin oxygen saturation, whereas hepatic microcirculatory hemoglobin oxygen saturation was even increased. At 24 hrs post-CLP, the rate of de novo gluconeogenesis as derived from hepatic C-glucose isotope enrichment after continuous intravenous 1,2,3,4,5,6-C6-glucose infusion (condensation biosynthesis modeling after gas chromatography-mass spectrometry isotope measurements) was similar in the two experimental groups.

CONCLUSIONS

During murine septic shock achieving normotensive hyperdynamic hemodynamics with fluid resuscitation and norepinephrine, exogenous glucose requirements together with the lack of norepinephrine-induced increase in the rate of gluconeogenesis mirror impaired metabolic capacity of the liver despite well-maintained hepatosplanchnic microvascular perfusion and oxygenation.

Assessment and treatment of perfusion abnormalities in the emergency patient

Many patients presented to the emergency veterinarian are suffering from global or local tissue hypoperfusion. Global or systemic hypoperfusion can occur secondary to a reduction in the effective circulating intravascular volume (hypovolemic shock) or reduced ability of the heart to pump blood around the body secondary to reduced cardiac function (cardiogenic shock),obstruction to blood flow (obstructive shock), or maldistribution of the circulating intravascular volume (distributive shock). Initial assessment involving physical examination supplemented by measurement of hemodynamic and metabolic parameters allows the clinician to recognize and treat patients with severe global hypoperfusion. Use of techniques like sublingual capnometry and measurement of central venous oxygen saturation may aid recognition and evaluation of early hypoperfusion. Treatment decisions are made based on an assessment of the severity of the hypoperfusion and its probable underlying cause. Early effective treatment of hypoperfusion is likely to lead to a better outcome for the patient.

Splanchnic Hypoperfusion-Directed Therapies in Trauma: A Prospective, Randomized Trial

Splanchnic hypoperfusion as reflected by gastric intramucosal acidosis has been recognized as an important determinant of outcome in shock. A comprehensive splanchnic hypoperfusion-ischemia reperfusion (IRP) protocol was evaluated against conventional shock management protocols in critical trauma patients. The study was a prospective randomized trial comparing three therapeutic approaches to hypoperfusion after severe trauma in 151 trauma patients admitted to the intensive care unit. Group 1 patients received hemodynamic support based on conventional indicators of hypoperfusion. In group 2, resuscitation was further guided by gastric tonometry-derived estimates of splanchnic hypoperfusion and included more invasive hemodynamic monitoring and additional administration of colloid or crystalloid solutions, or inotropic support. Group 3 patients additionally received therapies specifically aimed at optimizing splanchnic perfusion and minimizing oxidant-mediated damage from reperfusion. The three groups were similar based on age, Injury Severity Score, and Acute Physiology and Chronic Health Evaluation II Scores. There were no statistically significant differences in mortality rates, organ dysfunction, ventilator days, or length of stay between any of the interventions. Techniques of optimization of splanchnic perfusion and minimization of oxidant-mediated reperfusion injury evaluated in this study were not advantageous relative to standard resuscitation measures guided by conventional or tonometric measures of hypoperfusion in the therapy of occult and clinical shock in trauma patients.

Involvement of nitric oxide in gastric protection of epinephrine in endotoxin intoxication in rats

Reduction in blood pressure may cause gastric mucosal hypoxia and injury during endotoxin intoxication. Epinephrine is found to increase gastric mucosal perfusion while managing hypotension. Nitric oxide plays an important role in regulating gastric mucosal perfusion and maintaining gastric integrity. The aim of this study was to investigate the involvement of nitric oxide in the gastric protection of epinephrine by determining gastric mucosal lipid peroxidation, ulceration, and hemorrhage levels in endotoxin intoxication in rats. Epinephrine significantly increased gastric mucosal nitrite levels, decreased gastric mucosal lipid peroxidation levels, and ameliorated gastric ulceration and hemorrhage in endotoxin-treated rats. Furthermore, nitric oxide synthase inhibitors potently reversed the effects of epinephrine on gastric mucosa in endotoxin-treated rats. It was suggested that nitric oxide might be involved in the protective effect of epinephrine on gastric mucosal injury in endotoxin intoxication in rats.

Hypoxemic reperfusion after 120 mins of intestinal ischemia attenuates the histopathologic and inflammatory response *

OBJECTIVE

It has been suggested that reactive oxygen species play a pivotal role in the initial organ-tissue injury during reperfusion, eliciting inflammatory reaction and multiple organ failure. It was investigated if hypoxemic reperfusion attenuates tissue injury and inflammatory response.

DESIGN

Randomized animal study.

SETTING

Medical school laboratory.

SUBJECTS

Twenty-five male pigs weighing 25-28 kg.

INTERVENTIONS

Pigs were subjected to 120 mins of intestinal ischemia by clamping the superior mesenteric artery. Upon declamping, the animals were randomly assigned to receive either hypoxemic reperfusion (HR group, n = 9) reperfused with a Pao2 = 30-35 or normoxemic reperfusion (control group, n = 16) reperfused with a Pao2 = 100 mm Hg for 120 mins. Fluids without inotropes were given to combat circulatory shock during reperfusion.

MEASUREMENTS AND MAIN RESULTS

Portal blood and intestinal and lung biopsies were collected at baseline, end of ischemia, and end of reperfusion. Histopathologic changes were scored, and interleukin-1beta, qualitative Limulus amebocyte, lysate test, and Pao2/Fio2 were measured. Eight of 16 animals of the control group and seven of nine of the HR group survived (p = .22). At the end of reperfusion, the intestinal (p = .004) and lung (p = .028) pathologic scores were lower in the HR group compared with controls. The only significant difference in concentration of interleukin-1beta in the portal blood between the two animal groups occurred 120 mins after reperfusion (p = .006). The number of HR animals with a positive Limulus test was significantly smaller compared with controls at 60 (p = .041) and 120 (p = .07) mins of reperfusion. During the period of ischemia, the Pao2/Fio2 decreased similarly in the control and HR group, whereas after 120 mins of reperfusion the rate was significantly higher in the HR group.

CONCLUSIONS

Hypoxemic reperfusion represents an intervention that may attenuate the triggering of multifactorial cascade and organ tissue injury.

The evaluation and management of shock

Shock is an emergency that requires continuous bedside evaluation, resuscitation, and re-evaluation. The initial bedside examination allows the clinician to determine whether the patient exhibits a clinical picture that is consistent with hypovolemic, cardiogenic, or vasodilatory shock. The primary survey dictates urgent initial resuscitation that usually consists of intubation, ventilation, and volume support. Vasoactive therapy is started when the patient is well volume-resuscitated and consists of inotropic support for cardiogenic shock and pressor therapy for vasodilatory shock. The secondary survey is helpful in revealing the cause of shock and necessary to institute early definitive therapy. Early shock has a hemodynamic component, which is often easily reversed. Septic shock and prolonged shock from any cause has an inflammatory component, which is not easily reversed and leads to multiple-system organ failure (MSOF) and death. Success in treatment of shock depends on early recognition of shock and the rapid tempo of resuscitation of its hemodynamic component to prevent or minimize the inflammatory component.

Continuous Therapeutic Epinephrine but not Norepinephrine Prolongs Splanchnic IL-6 Production in Porcine Endotoxic Shock

Catecholamines play a central role in the treatment of sepsis-associated hypotension. However, these hormones have also been shown to modulate the lipopolysaccharide (LPS)-induced induction of cytokines such as tumor necrosis factor alpha, interleukin (IL)-10, and IL-6 in vitro and in human endotoxemia. We hypothesized that catecholamines applied therapeutically in septic shock also influence cytokine patterns. We studied the cytokine response in tissues of the splanchnic compartment in a porcine endotoxin shock model up to 4 h. Shock was induced by a short infusion of LPS, and animals were treated either with fluid resuscitation alone or in combination with continuous epinephrine or norepinephrine. Animals, receiving epinephrine therapy, showed a significantly prolonged upregulation of IL-6 mRNA expression at 4 h after LPS application in liver (P = 0.0014), spleen (P < 0.0001), and mesenteric lymph nodes (P = 0.0078) as compared with animals treated with norepinephrine or fluid resuscitation. Serum IL-6 increased over time in all groups. The total concentration of the cytokine (area under the curve) was significantly higher in the epinephrine group as compared with the norepinephrine and fluid resuscitation groups (P = 0.017). The peak of serum tumor necrosis factor alpha at 1 h after LPS application was already significantly reduced by epinephrine, which was only administered at a mean of less than 0.05 microg/kg/min at this time point (P < 0.01). None of the catecholamines had a significant effect on IL-10 serum levels when compared with animals receiving fluid resuscitation alone. Our data suggest that the therapeutic application of epinephrine but not of norepinephrine is associated with a profound effect on the IL-6 response of splanchnic reticuloendothelial tissues.

Myocardial ischemia in intestinal postischemic shock: the effect of hypoxemic reperfusion

OBJECTIVE

The circulatory shock following intestinal ischemia-reperfusion injury has been attributed to hypovolemia. The purpose of the current study is to clarify the pathophysiology of this type of shock and to test the hypothesis that hypoxemic compared with normoxemic reperfusion improves hemodynamics.

DESIGN

Randomized animal study.

SETTING

Medical school laboratory.

SUBJECTS

Twenty-one pigs.

INTERVENTIONS

Pigs were subjected to 120 mins of intestinal ischemia by clamping the superior mesenteric artery. Upon declamping, the animals were randomized into two groups: a group that received hypoxemic reperfusion (HR group, n = 8) with a PaO2 = 30-35 and a control group reperfused with PaO2 = 100 mm Hg (control group, n = 13).

MEASUREMENTS AND MAIN RESULTS

Measurements included mean arterial pressure, cardiac index, pulmonary artery occlusion pressure, and requirements for fluids and epinephrine. Biopsies from the terminal ileal mucosa were taken for malondialdehyde measurements at baseline, at 120 mins of ischemia, and at 30 and 60 mins of reperfusion. A piece of left ventricle was obtained after 120 mins of reperfusion for histologic studies. Five of 13 animals of the control group died in intractable shock; no animal of the HR group died (p =.11). The decrease in the mean arterial pressure during reperfusion was more pronounced in the control group (p <.008) despite the larger doses of epinephrine administered, compared with the HR group (p <.02). During reperfusion, both groups exhibited a decrease in cardiac index; this was more pronounced in the control group (p =.0007). Pulmonary artery occlusion pressure increased during reperfusion in both groups and was more pronounced in the control group (p =.04 at 60 mins). Although mixed venous blood oxygen saturation of the control animals was higher at 30 mins of reperfusion (p =.005), it declined after 60 mins and became lower than that of HR animals at the end of reperfusion (p <.02). The myocardial histopathologic injury score was higher in the control group (2.0 +/- 0.69 and 3.4 +/- 0.89 for the HR and control groups, respectively; p <.03). The concentrations of intestinal mucosa malondialdehyde were significantly higher in the control group at 60 mins of reperfusion (p <.03).

CONCLUSIONS

Acute myocardial ischemia and left heart failure significantly contribute to the circulatory shock that follows intestinal ischemia/reperfusion injury and are attenuated by hypoxemic reperfusion.

Effects of norepinephrine alone and norepinephrine plus dopamine on human intestinal mucosal perfusion

OBJECTIVES

To evaluate the effect of norepinephrine alone and norepinephrine combined with dopamine on jejunal mucosal perfusion, gastric-arterial pCO(2) gradient, and global splanchnic oxygen demand-supply relationship after cardiac surgery.

DESIGN

A prospective interventional study.

SETTING

A university cardiothoracic intensive care unit.

PATIENTS

Eighteen patients were studied during propofol sedation and mechanical ventilation after uncomplicated coronary artery bypass surgery.

INTERVENTIONS

After control measurements, each patient received norepinephrine (50+/-26 ng.kg.min) to increase mean arterial blood pressure by 30% followed by addition of low-dose dopamine (2.6+/-0.3 microg x kg x min). Postdrug control measurements were performed 120 min after discontinuation of the catecholamines.

MEASUREMENTS AND RESULTS

Norepinephrine induced a 32% increase in systemic vascular resistance with no change in cardiac index. Neither jejunal mucosal perfusion, assessed by laser Doppler flowmetry, nor gastric-arterial pCO(2) gradient (tonometry) was affected by norepinephrine. Splanchnic O(2)-extraction increased ( P<0.05) and this increase was positively correlated to the individual dose of norepinephrine ( r = 0.78, P<0.0001). Splanchnic lactate extraction was increased by norepinephrine ( P<0.05). None of the patients had splanchnic lactate production during norepinephrine infusion. The addition of dopamine increased cardiac index by 27% ( P<0.001) and decreased splanchnic O(2 )extraction. Dopamine increased jejunal mucosal perfusion by 32% ( P<0.001) while the gastric-arterial pCO(2) gradient remained unchanged.

CONCLUSIONS

Vasopressor therapy with norepinephrine after cardiac surgery did not jeopardize intestinal mucosal perfusion in spite of a dose-dependent increase of the global splanchnic oxygen demand-supply relationship. The addition of dopamine increased intestinal mucosal perfusion.

Effects of dopamine, norepinephrine, and epinephrine on the splanchnic circulation in septic shock: which is best?

OBJECTIVE

To assess the effects of different doses of dopamine, norepinephrine, and epinephrine on the splanchnic circulation in patients with septic shock.

DESIGN

Prospective, randomized, open-label study.

SETTING

A 31-bed, medicosurgical intensive care unit of a university hospital.

PATIENTS

Convenience sample of 20 patients with septic shock, separated into two groups according to whether (moderate shock group, n = 10) or not (severe shock, n = 10) dopamine alone was able maintain mean arterial pressure >65 mm Hg.

INTERVENTIONS

Dopamine was progressively withdrawn and replaced successively by norepinephrine and then epinephrine (the order of the two agents was randomly determined) to maintain mean arterial pressure constant (moderate shock) or to increase mean arterial pressure above 65 mm Hg (severe shock).

MEASUREMENTS AND MAIN RESULTS

Systemic circulation (pulmonary artery catheter) and splanchnic circulation (indocyanine green dilution and hepatic vein catheter) and gastric mucosal Pco(2) (gas tonometry) were measured during dopamine (moderate shock only), norepinephrine, and epinephrine administration (both groups). Data were analyzed with nonparametric tests and are presented as median [percentiles 25-75]. In moderate shock, cardiac index was similar to dopamine and norepinephrine (3.1 [2.7-3.8] vs. 2.9 [2.7-4.1] L/min.m2, p = nonsignificant) but greater with epinephrine (4.1 [3.5-4.4] p <.01 vs. dopamine and norepinephrine). Splanchnic blood flow was similar with the three agents (732 [413-1483] vs. 746 [470-1401] vs. 653 [476-1832] mL/min.m, p = nonsignificant). The gradient between mixed-venous and hepatic venous oxygen saturations was lower with dopamine than with norepinephrine and epinephrine, but the Pco(2) gap was similar with the three agents. In severe shock, cardiac index was higher, but splanchnic blood flow was lower, with epinephrine than with norepinephrine (4.6 [3.7-5.3] vs. 3.4 [3.0-4.1] L/min.m2, p <.01 and 860 [684-1334] vs. 977 [806-1802] mL/min.m2, p <.05, respectively). Epinephrine increased the mixed-venous and hepatic venous oxygen saturation gradient but did not alter Pco(2) gap.

CONCLUSIONS

Dopamine and norepinephrine have similar hemodynamic effects, but epinephrine can impair splanchnic circulation in severe septic shock.

Disruption of bladder epithelium barrier function after spinal cord injury

Neural-epithelial interactions are hypothesized to play an important role in bladder function. We determined whether spinal cord injury (SCI) altered several indicators of urinary bladder epithelium barrier function, including continuity of the surface umbrella cell layer, transepithelial resistance (TER), and urea and water permeability. Within 2 h of SCI, significant changes in uroepithelium were noted, including disruption of the surface umbrella cells and an approximately 50% decrease in TER. By 24 h, TER reached a minimum and was accompanied by significant increases in water and urea permeability. Regeneration of the surface uroepithelium was accomplished by 14 days after SCI and was accompanied by a return to normal TER and urea and water permeabilities. This early disruption of the uroepithelial permeability and accompanying changes in uroepithelial morphology were prevented by pretreatment with hexamethonium (a blocker of ganglion transmission), indicating involvement of sympathetic or parasympathetic input to the urinary bladder. In addition, prior treatment with capsaicin worsened the effect of SCI on uroepithelial permeability, suggesting that capsaicin-sensitive afferents may play a protective role in the process. These results demonstrate that SCI results in a significant disruption of the urinary bladder uroepithelium and that these changes may be mediated in part by an interaction with bladder nerves.

The role of the intestine in the pathophysiology and management of severe acute pancreatitis

BACKGROUND

The outcome of severe acute pancreatitis has scarcely improved in 10 years. Further impact will require new paradigms in pathophysiology and treatment. There is accumulating evidence to support the concept that the intestine has a key role in the pathophysiology of severe acute pancreatitis which goes beyond the notion of secondary pancreatic infection. Intestinal ischaemia and reperfusion and barrier failure are implicated in the development of multiple organ failure.

DISCUSSION

Conventional management of severe acute pancreatitis has tended to ignore the intestine. More recent attempts to rectify this problem have included 1) resuscitation aimed at restoring intestinal blood flow through the use of appropriate fluids and splanchnic-sparing vasoconstrictors or inotropes; 2) enteral nutrition to help maintain the integrity of the intestinal barrier; 3) selective gut decontamination and prophylactic antibiotics to reduce bacterial translocation and secondary infection. Novel therapies are being developed to limit intestinal injury, and these include antioxidants and anti-cytokine agents. This paper focuses on the role of the intestine in the pathogenesis of severe acute pancreatitis and reviews the implications for management.

Effect of increasing norepinephrine dosage on regional blood flow in a porcine model of endotoxin shock

OBJECTIVE

To evaluate the effect of a norepinephrine-induced differential increase in mean arterial pressure on splanchnic and renal perfusion in a porcine model of volume-resuscitated endotoxic shock.

DESIGN

Prospective, controlled, acute interventional study.

SETTING

Animal research laboratory.

SUBJECTS

Fourteen landrace pigs, seven treated with norepinephrine and seven used as endotoxemic controls.

INTERVENTIONS

In an acute endotoxic shock model, norepinephrine was used to reverse hypotension in seven fluid-resuscitated pigs, anesthetized with alpha-chloralose and equipped with flow probes around the portal vein and renal artery, renal and jejunal mucosal laser Doppler flowmetry, and jejunal tonometry. Mean arterial pressure was increased by 10 and then 20 mm Hg above the shock level with norepinephrine. Seven shocked, fluid-resuscitated only animals served as the comparison group.

MEASUREMENTS AND MAIN RESULTS

Measurements were performed before 2-hr endotoxin infusion and at the end of each increased level of mean arterial pressure. Raising mean arterial pressure with norepinephrine by 10 mm Hg significantly increased cardiac output, systemic oxygen extraction, and portal vein blood flow; stabilized metabolic acidosis; and tended to restore renal and jejunal mucosal flows to preshock levels. Increasing mean arterial pressure by 20 mm Hg further increased cardiac output and oxygen delivery but without improving portal vein, renal artery, and jejunal mucosal blood flows.

CONCLUSIONS

Norepinephrine, administered to increase mean arterial pressure by 10 mm Hg in an acute model of volume-resuscitated endotoxic shock, improved systemic and regional perfusion. The administration of norepinephrine to increase mean arterial pressure 20 mm Hg above shock did not increase renal and splanchnic blood flows, despite an enhanced cardiac output.

Impact of duodenal feeding on the oxygen balance of the splanchnic region during different phases of severe burn injury

Enteral nutrition is recommended in burned patients. Depending on the amount administered, enteral feeding causes an increase of intestinal oxygen-demand. Since intestinal perfusion is decreased after major burns the aim of this study was to evaluate, whether duodenal feeding might be a cofactor for the development of a splanchnic O(2)-imbalance. In 15 severely burned patients during duodenal feeding starting within 6 h after injury the assessment of the CO(2)-gap between arterial and gastric CO(2), as a parameter for the measurement of intestinal O(2)-balance was performed. Beginning prior to enteral nutrition CO(2)-gap measurements were carried out to show when the CO(2)-gap increased above 30 mmHg during the whole critical illness phase of the patients. When the CO(2)-gap increased above 30 mmHg enteral nutrition was reduced by 50% and the CO(2)-gap was measured 1 h later. In none of the patients the CO(2)-gap increased during increase of enteral nutrition. In seven patients, the CO(2)-gap increased between the 6th and 13th day above 30 mmHg and fell significantly 1 h after reduction of enteral nutrition. Contrary to the early postburn phase, enteral feeding might have adverse effects on the oxygen balance of the intestine in the later stages of the critical illness phase.

ARDS. Monitoring tissue perfusion

A clinically feasible method for assessing regional splanchnic perfusion is still lacking. Methods used for research purposes demonstrate that the effects of current therapies on splanchnic perfusion are not predictable in intensive care patients with and without ARDS. Tonometry, laser Doppler flowmetry, and spectrophotometry have been used to assess splanchnic perfusion. Combining the available methods in different parts of the gastrointestinal tract may help assess splanchnic perfusion more accurately in the near future.

Effects of dopexamine on acute necrotising pancreatitis in rats

OBJECTIVE

To examine the effects of dopexamine on pancreatic tissue oxygen tension (PtO2) and the extent of acinar injury in rats with acute necrotising pancreatitis

DESIGN

Laboratory study.

SETTING

Medical school, Turkey.

ANIMALS

68 Sprague Dawley rats.

MAIN OUTCOME MEASURES

Cardiorespiratory measurements, pancreatic PtO2, effects on activity of serum amylase and concentration trypsinogen activation peptide (TAP). and histological picture.

RESULTS

The four study groups (sham + saline, sham + dopexamine, acute pancreatitis and acute pancreatitis + dopexamine) were each divided into two; in 9 rats in each, pancreatic biochemistry was studied, and in the remaining 8 in each group serum biochemistry and histology were studied. The groups were comparable with regard to mean arterial pressure, heart rate, arterial blood gases, packed cell volume, and serum amylase activity. The use of dopexamine increased pancreatic PtO2 in the sham + dopexamine group without the important blood pressure changes. The induction of pancreatitis resulted in a significant reduction in pancreatic PtO2 in the pancreatitis groups. The use of dopexamine did not increase pancreatic PtO2. There were no significant differences in plasma TAP concentration and the extent of acinar cell injury in the animals in the pancreatitis groups.

CONCLUSION

Treatment with dopexamine does not improve the pancreatic microcirculation or reduce the extent of acinar cell injury in acute necrotising pancreatitis and is therefore unlikely to be of benefit in patients with pancreatitis.

Impact of early high caloric duodenal feeding on the oxygen balance of the splanchnic region after severe burn injury

Early enteral nutrition is recommended in burned patients. Depending on the amount administered, enteral feeding causes an increase of intestinal oxygen-demand. Although early moderate enteral nutrition has been shown to be beneficial, early high calorie enteral nutrition might lead to an imbalance of the O(2)-balance of the gut since intestinal perfusion is decreased after major burns. In 20 severely burned patients during the first 48 h of early high caloric duodenal feeding an assessment of the CO(2)-gap between the arterial and the gastric CO(2), as parameter for the intestinal O(2)-balance, was performed. Time points were prior to starting the enteral nutrition (BASE) subsequently every 30 min after increasing the amount of nutrition administered and from the 11th to the 48th h after beginning of nutrition in intervals of 6 h. In none of the patients was the CO(2)-gap increased during the rapid increase of enteral nutrition. On the contrary the CO(2)-gap decreased significantly. We conclude that high caloric duodenal feeding in the early hypodynamic postburn phase does not have adverse effects on the oxygen balance of the intestine.

Effects of epinephrine on intestinal oxygen supply and mucosal tissue oxygen tension in pigs

OBJECTIVE

To study the effects of increasing dosages of epinephrine given intravenously on intestinal oxygen supply and, in particular, mucosal tissue oxygen tension in an autoperfused, innervated jejunal segment.

DESIGN

Prospective, randomized experimental study.

SETTING

Animal research laboratory.

SUBJECTS

Domestic pigs.

INTERVENTIONS

Sixteen pigs were anesthetized, paralyzed, and normoventilated. A small segment of the jejunal mucosa was exposed by midline laparotomy and antimesenteric incision. Mucosal oxygen tension was measured by using Clark-type surface oxygen electrodes. Microvascular hemoglobin oxygen saturation and microvascular blood flow (perfusion units) were determined by tissue reflectance spectrophotometry and laser-Doppler velocimetry. Systemic hemodynamics, mesenteric-venous acid-base and blood gas variables, and systemic acid-base and blood gas variables were recorded. Measurements were performed after a resting period and at 20-min intervals during infusion of increasing dosages of epinephrine (n = 8; 0.01, 0.05, 0.1, 0.5, 1, and 2 microg x kg(-1) x min(-1)) or without treatment (n = 8). In addition, arterial and mesenteric-venous lactate concentrations were measured at baseline and at 60 and 120 mins.

MEASUREMENTS AND MAIN RESULTS

Epinephrine infusion led to significant tachycardia; an increase in cardiac output, systemic oxygen delivery, and oxygen consumption; and development of lactic acidosis. Epinephrine significantly increased jejunal microvascular blood flow (baseline, 267 +/- 39 perfusion units; maximum value, 443 +/- 35 perfusion units) and mucosal oxygen tension (baseline, 36 +/- 2.0 torr [4.79 +/- 0.27 kPa]; maximum value, 48 +/- 2.8 torr [6.39 +/- 0.37 kPa]) and increased hemoglobin oxygen saturation above baseline. Epinephrine increased mesenteric venous lactate concentration (baseline, 2.9 +/- 0.6 mmol x L(-1); maximum value, 5.5 +/- 0.2 mmol x L(-1)) without development of an arterial-mesenteric venous lactate concentration gradient.

CONCLUSIONS

Epinephrine increased jejunal microvascular blood flow and mucosal tissue oxygen supply at moderate to high dosages. Lactic acidosis that develops during infusion of increasing dosages of epinephrine is not related to development of gastrointestinal hypoxia.

Influence of epinephrine and norepinephrine on intestinal villous blood flow during endotoxemia

PURPOSE

The objective of this study was to determine the effects of epinephrine and norepinephrine on mucosal villous blood flow in a normotensive model of endotoxemia.

MATERIALS AND METHODS

Thirty-two anesthetized rats were laparotomized, and a jejunal portion was exteriorized and opened by an antimesenteric incision. The jejunal segment was fixed on a plexiglass stage with the mucosal surface upward. Microcirculatory parameters were assessed by intravital videomicroscopy. The animals were randomly assigned to receive one of four treatments: infusion of Escherichia coli lipopolysaccharides (LPS, 2 mg/kg/h) without catecholamine pretreatment (LPS group); or infusion of LPS with epinephrine pretreatment (0.2 microg/kg/min, start 30 minutes before LPS infusion) (E group), or infusion of LPS with norepinephrine pretreatment (0.2 microg/kg/min, start 30 minutes before LPS infusion) (NE group). The control group did not receive either catecholamines or LPS. Mean diameter of central arterioles (D(A)) and mean erythrocyte velocity within the arterioles (V(E)) were measured 30 minutes before and at 0, 60, and 120 minutes after induction of endotoxemia. Mucosal villous blood flow was calculated from D(A) and V(E).

RESULTS

LPS infusion alone and norepinephrine plus LPS infusion led to a significant vasoconstriction of central arterioles, which was associated with a similar decrease in mucosal villous blood flow. Epinephrine infusion alone led to a vasodilation and an increase in villous blood flow within the first 30 minutes. After induction of endotoxemia, D(A) returned to baseline values and villous blood flow was as low as in the LPS and the norepinephrine group after 120 minutes.

CONCLUSION

In this experimental rat model, the catecholamines epinephrine and norepinephrine in a dosage of 0.2 microg.kg(-1).min(-1) neither diminish nor improve mucosal villous blood flow during the early phase of endotoxemia.