Clinical review: influence of vasoactive and other therapies on intestinal and hepatic circulations in patients with septic shock

Norepinephrine combined with phenylephrine versus norepinephrine in patients with septic shock: a retrospective cohort study

BACKGROUND

Phenylephrine (PE) and norepinephrine (NE) may be used to maintain adequate blood pressure and tissue perfusion in patients with septic shock, but the effect of NE combined with PE (NE-PE) on mortality remains unclear. We hypothesized that NE-PE would not inferior to NE alone for all-cause hospital mortality in patients with septic shock.

METHODS

This single-center, retrospective cohort study included adult patients with septic shock. According to the infusion type, patients were divided into the NE-PE or NE group. Multivariate logistic regression, propensity score matching and doubly robust estimation were used to analyze the differences between groups. The primary outcome was the all-cause hospital mortality rate after NE-PE or NE infusion.

RESULTS

Among 1, 747 included patients, 1, 055 received NE and 692 received NE-PE. For the primary outcome, the hospital mortality rate was higher in patients who received NE-PE than in those who received NE (49.7% vs. 34.5%, p < 0.001), and NE-PE was independently associated with higher hospital mortality (odds ratio = 1.76, 95% confidence interval = 1.36-2.28, p < 0.001). Regarding secondary outcomes, patients in the NE-PE group had longer lengths of stay in ICU and hospitals. Patients in the NE-PE group also received mechanical ventilation for longer durations.

CONCLUSIONS

NE combined with PE was inferior to NE alone in patients with septic shock, and it was associated with a higher hospital mortality rate.

Non-occlusive mesenteric ischemia in critically ill patients

BACKGROUND

Non-occlusive mesenteric ischemia (NOMI) is a life-threatening acute condition that has an overall in-hospital mortality rate of up to 75%. Critically ill patients are often admitted to intensive care units (ICUs) due to shock, and these patients are frequently at risk of developing NOMI. The objective of this study was to determine the clinical features of critically ill patients with NOMI and evaluate the risk factors for in-hospital mortality among these patients.

METHODS

We reviewed the electronic medical records of 7,346 patients who underwent abdominal contrast-enhanced computed tomography during their ICU stay at Samsung Medical Center (Seoul, Korea) between January 1, 2010 and December 31, 2019. After reviewing each patient's computed tomography (CT) scans, 60 patients were diagnosed with NOMI and included in this analysis. The patients were divided into survivor (n = 23) and non-survivor (n = 37) groups according to the in-hospital mortality.

RESULTS

The overall sequential organ failure assessment (SOFA) score for the included patients upon admission to the ICU was 8.6 ± 3.1, and medical ICU admissions were most common (66.7%) among the patients. The SOFA score upon admission to the ICU was higher for the non-survivors than for the survivors (9.4 vs. 7.4; p = 0.017). Non-survivors were more often observed in the medical ICU admissions (39.1% vs. 83.8%) than in the surgical ICU admissions (47.8% vs. 10.8%) or the cardiac ICU admissions (13.0% vs. 5.4%). Laboratory test results, abdominal CT findings, and the use of vasopressors and inotropes did not differ between the two groups. In a multivariable analysis, SOFA scores >8 upon admission to the ICU (odds ratio [OR] 4.51; 95% 1.12-18.13; p = 0.034), patients admitted to the ICU with medical problems (OR 7.99; 95% 1.73-36.94; p = 0.008), and abdominal pain (OR 4.26; 95% 1.05-17.35; p = 0.043) were significant prognostic predictors for in-hospital mortality.

CONCLUSIONS

The SOFA score >8 upon admission to the ICU, admission to the ICU for medical problems, and abdominal pain at diagnosis are associated with increased mortality among patients with NOMI.

Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function

Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.

Preoperative Evaluation and Anesthetic Management of Patients With Liver Cirrhosis Undergoing Cardiac Surgery

Preoperative evaluation and anesthetic management of patients with liver cirrhosis undergoing cardiac surgery remain a clinical challenge because of its high risk for perioperative complications. This narrative review article summarizes the pathophysiology and anesthetic implication of liver cirrhosis on each organ system. It will help physicians to evaluate surgical candidates, to optimize intraoperative management, and to anticipate complications in liver cirrhosis patients undergoing cardiac surgery. Morbidity typically results from bleeding, sepsis, multisystem organ failure, or hepatic insufficiency. These complications occur as a result of the presence of coagulopathy, poor nutritional status, immune dysfunction, cirrhotic cardiomyopathy, and renal and pulmonary dysfunction that occur with liver cirrhosis. Therefore, liver cirrhosis should not be seen as a single disease, but one that manifests with multiorgan dysfunction. Cardiac surgery in patients with liver cirrhosis increases the risk of perioperative complications, and it presents a particular challenge to the anesthesiologist in that nearly every aspect of normally functioning physiology may be jeopardized in a unique way. Accurately classifying the extent of liver disease, preoperative optimization, and surgical risk communication with the patient are crucial. In addition, all teams involved in the surgery should communicate openly and coordinate in order to ensure optimal care. To reduce perioperative complications, consider using off-pump cardiopulmonary bypass techniques and optimal perfusion modalities to mimic current physiologic conditions.

Personalizing blood pressure management in septic shock

This review examines the available evidence for targeting a specific mean arterial pressure (MAP) in sepsis resuscitation. The clinical data suggest that targeting an MAP of 65-70 mmHg in patients with septic shock who do not have chronic hypertension is a reasonable first approximation. Whereas in patients with chronic hypertension, targeting a higher MAP of 80-85 mmHg minimizes renal injury, but it comes with increased risk of arrhythmias. Importantly, MAP alone should not be used as a surrogate of organ perfusion pressure, especially under conditions in which intracranial, intra-abdominal or tissue pressures may be elevated. Organ-specific perfusion pressure targets include 50-70 mmHg for the brain based on trauma brain injury as a surrogate for sepsis, 65 mmHg for renal perfusion and >50 mmHg for hepato-splanchnic flow. Even at the same MAP, organs and regions within organs may have different perfusion pressure and pressure-flow relationships. Thus, once this initial MAP target is achieved, MAP should be titrated up or down based on the measures of organ function and tissue perfusion.

Shock Management for Cardio-surgical ICU Patients - The Golden Hours

Postoperative shock following cardiac surgery is a serious condition with a high morbidity and mortality. There are four types of shock: cardiogenic, hypovolemic, obstructive and distributive and these can occur alone or in combination. Early identification of the underlying diseases and understanding of the mechanisms at play are key for successful management of shock. Prompt resuscitation measures are necessary to reverse the shock state and avoid permanent organ dysfunction or death. In this review, the authors focus on the management during the first 6 hours of shock (the 'golden hours'). They discuss how to optimise preload, vascular tone, contractility, heart rate and oxygen delivery. The review incorporates the findings of recent trials on early goal-directed therapy and includes practical recommendations in areas in which the evidence is scare or controversial. While the review focuses on cardio-surgical patients, the suggested treatment algorithms might be usefully expanded to other critically ill patients with shock arising from other causes.

Activation of α2 adrenoceptor attenuates lipopolysaccharide-induced hepatic injury

Sepsis induces hepatic injury but whether alpha-2 adrenoceptor (α2-AR) modulates the severity of sepsis-induced liver damage remains unclear. The present study used lipopolysaccharide (LPS) to induce hepatic injury and applied α2-AR agonist dexmedetomidine (DEX) and/or antagonist yohimbine to investigate the contribution of α2-AR in LPS-induced liver injury. Our results showed that LPS resulted in histological and functional abnormality of liver tissue (ALT and AST transaminases, lactate), higher mortality, an increase in proinflammatory cytokines (IL-1β, IL-6 & TNF-α), as well as a change in oxidative stress (MDA, SOD). Activation of α2-AR by dexmedetomidine (DEX) attenuated LPS-induced deleterious effects on the liver and block of α2-AR by yohimbine aggravated LPS-induced liver damage. Our data suggest that α2-AR plays an important role in sepsis-induced liver damage and activation of α2-AR with DEX could be a novel therapeutic avenue to protect the liver against sepsis-induced injury.

Thoracic epidural anesthesia: Effects on splanchnic circulation and implications in Anesthesia and Intensive care

AIM: To evaluate the currently available evidence on thoracic epidural anesthesia effects on splanchnic macro and microcirculation, in physiologic and pathologic conditions.

METHODS: A PubMed search was conducted using the MeSH database. Anesthesia, Epidural was always the first MeSH heading and was combined by boolean operator AND with the following headings: Circulation, Splanchnic; Intestines; Pancreas and Pancreatitis; Liver Function Tests. EMBASE, Cochrane library, ClinicalTrials.gov and clinicaltrialsregister.eu were also searched using the same terms.

RESULTS: Twenty-seven relevant studies and four ongoing trials were found. The data regarding the effects of epidural anesthesia on splanchnic perfusion are conflicting. The studies focusing on regional macro-hemodynamics in healthy animals and humans undergoing elective surgery, demonstrated no influence or worsening of regional perfusion in patients receiving thoracic epidural anesthesia (TEA). On the other hand most of the studies focusing on micro-hemodynamics, especially in pathologic low flow conditions, suggested that TEA could foster microcirculation.

CONCLUSION: The available studies in this field are heterogeneous and the results conflicting, thus it is difficult to draw decisive conclusions. However there is increasing evidence deriving from animal studies, that thoracic epidural blockade could have an important role in modifying tissue microperfusion and protecting microcirculatory weak units from ischemic damage, regardless of the effects on macro-hemodynamics.

[Perioperative protection of the gastrointestinal tract]

The gastrointestinal tract is a complex organ system. Dysfunctions of this organ system may evoke a variety of consequences for the entire organism and influence the inflammatory response in particular. In perioperative medicine, nutrition, prokinetics, peridural anesthesia, catecholamines and volume therapy can be applied in order to improve the gastrointestinal functional or at least to avoid further aggravation. Early enteral nutrition is especially important in the reduction of postsurgical ileus and infectious complications. Also, prokinetics and thoracic peridural anesthesia favorably affect postsurgical ileus. Norepinephrine, if necessary in combination with dobutamine, seems to have fewer negative effects on splanchnic perfusion than epinephrine. The data on volume therapy remain controversial but fluid balance has to be calculated very carefully also considering enteral loss of fluids. Thus, in order to treat and avoid gastrointestinal problems after surgery and to prevent negative effects for the complete organism, multimodal concepts with regard to detail are required.

Vasopressin for treatment of vasodilatory shock: an ESICM systematic review and meta-analysis

OBJECTIVE

To examine the benefits and risks of vasopressin or its analog terlipressin for patients with vasodilatory shock.

DATA SOURCE

We searched the CENTRAL, MEDLINE, EMBASE, and LILACS databases (up to March 2011) as well as reference lists of articles and proceedings of major meetings; we also contacted trial authors. We considered randomized and quasirandomized trials of vasopressin or terlipressin versus placebo or supportive treatment in adult and pediatric patients with vasodilatory shock. The primary outcome for this review was short-term all-cause mortality.

STUDY SELECTION

We identified 10 randomized trials (1,134 patients). Six studies were considered for the main analysis on mortality in adults.

DATA EXTRACTION AND SYNTHESIS

The crude short-term mortality was 206 of 512 (40.2%) in vasopressin/terlipressin-treated patients and 198 of 461 (42.9%) in controls [six trials, risk ratio (RR) = 0.91; 95% confidence interval (CI) 0.79-1.05; P = 0.21; I(2) = 0%]. There were 49 of 463 (10.6%) patients with serious adverse events in the vasopressin/terlipressin arm and 51 of 431 (11.8%) in the control arm (four trials, RR = 0.90; 95% CI 0.49-1.67; P = 0.75; I(2) = 26%). Metaregression analysis showed negative correlation between vasopressin dose and norepinephrine dose (P = 0.03).

CONCLUSIONS

Overall, use of vasopressin or terlipressin did not produce any survival benefit in the short term in patients with vasodilatory shock. Physicians may value the sparing effects of vasopressin/terlipressin on norepinephrine requirement given its apparent safe profile.

Circulating microparticles from septic shock patients exert differential tissue expression of enzymes related to inflammation and oxidative stress

OBJECTIVE

Septic shock is characterized by hypotension and multiple organ failure after infection of microorganisms. Septic shock patients display high levels of circulating microparticles. These are small vesicles released from the plasma membrane of activated or apoptotic cells. Here, we have investigated the effects of in vivo injection of microparticles from nonseptic or septic subjects on protein expression in mouse tissues.

DESIGN

Prospective, controlled experiments.

SETTING

Animal basic science laboratory.

SUBJECTS

Male Swiss mice were randomly assigned to one of two groups: 11 animals injected with microparticles isolated from healthy subjects and 15 animals injected with microparticles isolated from septic patients.

INTERVENTIONS

Microparticles were extracted from whole blood of septic and nonseptic subjects and were intravenously injected in mice. After 24 hrs, mice were killed and heart, lungs, liver, and kidneys were isolated for Western blot assays. Organs were also used for direct measurements of nitric oxide and superoxide anion production by electron paramagnetic resonance.

MEASUREMENTS AND MAIN RESULTS

In heart and lungs, microparticles from septic shock patients increased the expression of endothelial and inducible nitric oxide synthases, cyclooxygenase-2, and nuclear factor-κB. However, extracellular superoxide dismutase was only increased in the heart. These effects were associated either with a greater oxidative or nitrative stress in heart and lungs, without affecting nitric oxide production. The liver exhibited an increase in oxidative stress linked to decreased endothelial nitric oxide synthase and manganese superoxide dismutase expression. However, cyclooxygenase-2 expression and IκBα phosphorylation were decreased. Septic microparticles did not change superoxide anion and nitric oxide productions in kidneys.

CONCLUSIONS

Results suggest that microparticles from septic shock patients exert pleiotropic and differential effects depending on target tissues with regard to the expression of proinflammatory proteins related with nitrative and oxidative stresses. Thus, microparticles might participate in organ dysfunction observed in septic shock patients.

The impact of resuscitated fecal peritonitis on the expression of the hepatic bile salt transporters in a porcine model

Sepsis is often associated with cholestatic liver dysfunction caused by changes in the expression profile of hepatic bile salt transporters. However, in rodent endotoxin models, the role of ischemic hepatitis caused by liver hypoperfusion cannot be delineated. We hypothesized that hepatocytes change their expression pattern of bile salt transporters during early severe sepsis despite adequate resuscitation. Fifteen anesthetized and instrumented pigs were randomized to either fecal peritonitis (n = 8) or control (n = 7). Resuscitation was performed by hydroxyethyl starch and norepinephrine infusion. Hemodynamic parameters and markers of cholestatic and ischemic hepatic dysfunction were recorded. At baseline and after 21 h, messenger RNA (mRNA) and protein expression of bile salt transporters was determined by quantitative real-time polymerase chain reaction and immunohistochemistry, respectively, on in vivo liver biopsies. All resuscitated septic pigs developed a normotensive hyperdynamic circulation with increased portal flow. After 21 h of peritonitis, no signs of biochemical or histological cholestasis were present. Na-taurocholate cotransporting polypeptide and bile salt export pump mRNA were downregulated by 83% (P = 0.001) and 67% (P = 0.001), respectively, in comparison with controls, whereas multidrug resistance-associated protein 4 (MRP4) mRNA was upregulated by 85% (P = 0.02). Bile salt export pump and MRP2 staining were downregulated in septic pigs. During early porcine fluid-resuscitated sepsis, hepatic basolateral influx (Na-taurocholate cotransporting polypeptide) and canalicular efflux (bile salt export pump) of bile salts were downregulated without hemodynamic signs of hepatic hypoperfusion or biochemical signs of cholestasis. In parallel, the basolateral escape transport (MRP4) was markedly upregulated, possibly as an early adaptive response to counteract hepatocellular accumulation of toxic bile acids.

Interpretation of blood pressure signal: physiological bases, clinical relevance, and objectives during shock states

Achievement of a mean blood pressure (MBP) target is one of the hemodynamic goals to ensure an adequate blood perfusion pressure in critically ill patients. Arterial catheter allows for a continuous and precise monitoring of arterial pressure signal. In addition to giving a precise MBP monitoring, analysis of the blood pressure wave provides information that may help the clinician to interpret hemodynamic status. The interpretation of BP wave requires the understanding of simple principles. In this review, we first discuss the physiological mechanism responsible for arterial pressure generation. We then emphasize the interpretation of the static indexes and the dynamic indexes generated by heart-lung interactions derived from arterial pressure wave. Finally, we focus on MBP value as a therapeutic target in critically ill patients. We discuss the recommended target MBP value by reviewing available data from experimental and clinical studies.

Preventing cardiac arrest during hemorrhagic shock with vasopressin

The optimal strategy of stabilizing hemodynamic function in uncontrolled traumatic hemorrhagic shock states is unclear. Although fluid replacement is established in controlled hemorrhagic shock, its use in uncontrolled hemorrhagic shock is controversial, because it may worsen bleeding. In the refractory phase of severe hemorrhagic shock, arginine vasopressin has been shown to be beneficial in selected cases due to an increase in arterial blood pressure, shift of blood away from a subdiaphragmatic bleeding site toward the heart and brain, and decrease in fluid-resuscitation requirements. Especially in patients with severe traumatic brain injury, rapid stabilization of cardiocirculatory function is essential to ensure adequate brain perfusion, thus, to prevent neurologic damage and to improve outcome. In addition, despite wide distribution of highly developed and professional emergency medical systems in western industrialized countries, survival chances of patients with uncontrolled traumatic hemorrhagic shock in the preclinical setting are still poor.

Bench-to-bedside review: Beta-adrenergic modulation in sepsis

Sepsis, despite recent therapeutic progress, still carries unacceptably high mortality rates. The adrenergic system, a key modulator of organ function and cardiovascular homeostasis, could be an interesting new therapeutic target for septic shock. β-Adrenergic regulation of the immune function in sepsis is complex and is time dependent. However, β₂ activation as well as β₁ blockade seems to downregulate proinflammatory response by modulating the cytokine production profile. β₁ blockade improves cardiovascular homeostasis in septic animals, by lowering myocardial oxygen consumption without altering organ perfusion, and perhaps by restoring normal cardiovascular variability. β-Blockers could also be of interest in the systemic catabolic response to sepsis, as they oppose epinephrine which is known to promote hyperglycemia, lipid and protein catabolism. The role of β-blockers in coagulation is less clear cut. They could have a favorable role in the septic pro-coagulant state, as β₁ blockade may reduce platelet aggregation and normalize the depressed fibrinolytic status induced by adre-nergic stimulation. Therefore, β₁ blockade as well as β₂ activation improves sepsis-induced immune, cardiovascular and coagulation dysfunctions. β₂ blocking, however, seems beneficial in the metabolic field. Enough evidence has been accumulated in the literature to propose β- adrenergic modulation, β₁ blockade and β₂ activation in particular, as new promising therapeutic targets for septic dyshomeostasis, modulating favorably immune, cardiovascular, metabolic and coagulation systems.

Poisoning-related bowel infarction: characteristics and outcomes

BACKGROUND

Bowel infarction (BI) is a rare complication of poisoning. We aimed to describe the characteristics of BI in poisoned patients compared to nonpoisoned patients.

METHODS

A retrospective review over a 4-year period of patients hospitalized in an intensive care unit who were diagnosed with BI; Mann-Whitney and Fischer's exact tests were used for comparisons.

RESULTS

Seventeen patients with BI [11 F/6 M, 66-year olds (55-72), median (25-75% percentiles)], including five out of around 1,800 poisoned patients, were identified (toxicants: nicardipine + venlafaxine, amlodipine, propranolol + hydroxyzine, dextropropoxyphene + clomipramine, and turpentine). Clinical presentation and severity were comparable between both groups. However, poisoned patients were significantly younger (p = 0.03) with less cardiovascular disease (p = 0.04) and fewer risk factors (p = 0.008). Delayed BI occurred 48 h (36-60) after the start of vasopressor administration [15.5 mg/h (4.5-30.0) norepinephrine and 6.0 mg/h (4.9-6.3) epinephrine]. Typical poisoning-related injury was jejunal ischemia without ileal localization. The predominant mechanism was nonocclusive mesenteric ischemia. Mortality was lower in poisoned patients (20 vs. 90%, p = 0.009).

CONCLUSION

Physicians should be aware that, despite patient age and the lack of cardiovascular risk factors, BI may rarely complicate severe poisonings requiring elevated doses of vasopressors and may present in a delayed fashion.

Comparison of the effects of aging and IL-6 on the hepatic inflammatory response in two models of systemic injury: scald injury versus i.p. LPS administration

Regardless of age, a marked elevation in circulating IL-6 levels correlates with increased mortality after injury or an inflammatory challenge. We previously reported that aged IL-6 knockout mice given LPS have improved survival and reduced inflammatory response than LPS-treated aged wild type (WT) mice. Herein, we analyzed the effects of aging and IL-6 on the hepatic inflammatory response in two models of systemic injury: dorsal scald (burn) injury versus intraperitoneal LPS administration. At 24 h after burn injury, circulating alanine aminotransferase and hepatic neutrophil accumulation were comparable regardless of age or IL-6 deficiency. However, at this same time point, these indicators of liver damage, in addition to hepatic levels of KC, a neutrophil chemoattractant, were increased in aged WT mice given LPS relative to young WT mice given LPS. The hepatic injury was drastically reduced in aged IL-6 knockout mice given LPS as compared with LPS-exposed aged WT mice. Our results suggest that the nature of the insult will determine the degree of remote injury in aged animals. In addition, the role of IL-6 as a contributing factor of tissue injury may be insult specific.

Developing alternative strategies for the treatment of traumatic haemorrhagic shock

PURPOSE OF REVIEW

The optimal strategy of stabilizing haemodynamic function in uncontrolled traumatic haemorrhagic shock states is unclear. Although fluid replacement is established in controlled haemorrhagic shock, its use in uncontrolled haemorrhagic shock is controversial, because it may worsen bleeding.

RECENT FINDINGS

In the refractory phase of severe haemorrhagic shock, arginine vasopressin has been shown to be beneficial in selected cases due to an increase in arterial blood pressure, shift of blood away from a subdiaphragmatic bleeding site towards the heart and brain, and decrease in fluid resuscitation requirements. Especially in patients with severe traumatic brain injury, rapid stabilization of cardiocirculatory function is essential to ensure adequate brain perfusion and thus to prevent neurological damage and to improve outcome. In addition, despite wide distribution of highly developed and professional emergency medical systems in western industrialized countries, survival chances of patients with uncontrolled traumatic haemorrhagic shock in the prehospital setting are still poor.

SUMMARY

A multicenter, randomized, controlled, international clinical trial is being initiated to assess the effects of arginine vasopressin (10 IU) vs. saline placebo in prehospital traumatic haemorrhagic shock patients, not responding to standard shock treatment, being managed by helicopter emergency medical services [vasopressin in traumatic haemorrhagic shock (VITRIS.at) study].

Gastrointestinal perfusion in septic shock

Septic shock is characterised by vasodilation, myocardial depression and impaired microcirculatory blood flow, resulting in redistribution of regional blood flow. Animal and human studies have shown that gastrointestinal mucosal blood flow is impaired in septic shock. This is consistent with abnormalities found in many other microcirculatory vascular beds. Gastrointestinal mucosal microcirculatory perfusion deficits have been associated with gut injury and a decrease in gut barrier function, possibly causing augmentation of systemic inflammation and distant organ dysfunction. A range of techniques have been developed and used to quantify these gastrointestinal perfusion abnormalities. The following techniques have been used to study gastrointestinal perfusion in humans: tonometry, laser Doppler flowmetry, reflectance spectrophotometry, near-infrared spectroscopy, orthogonal polarisation spectral imaging, indocyanine green clearance, hepatic vein catheterisation and measurements of plasma D-lactate. Although these methods share the ability to predict outcome in septic shock patients, it is important to emphasise that the measurement results are not interchangeable. Different techniques measure different elements of gastrointestinal perfusion. Gastric tonometry is currently the most widely used technique because of its non-invasiveness and ease of use. Despite all the recent advances, the usefulness of gastrointestinal perfusion parameters in clinical decision-making is still limited. Treatment strategies specifically aimed at improving gastrointestinal perfuision have failed to actually correct mucosal perfusion abnormalities and hence not shown to improve important clinical endpoints. Current and future treatment strategies for septic shock should be tested for their effects on gastrointestinal perfusion; to further clarify its exact role in patient management, and to prevent therapies detrimental to gastrointestinal perfusion being implemented.

Glucose metabolism and catecholamines

Until now, catecholamines were the drugs of choice to treat hypotension during shock states. Catecholamines, however, also have marked metabolic effects, particularly on glucose metabolism, and the degree of this metabolic response is directly related to the beta2-adrenoceptor activity of the individual compound used. Under physiologic conditions, infusing catecholamine is associated with enhanced rates of aerobic glycolysis (resulting in adenosine triphosphate production), glucose release (both from glycogenolysis and gluconeogenesis), and inhibition of insulin-mediated glycogenesis. Consequently, hyperglycemia and hyperlactatemia are the hallmarks of this metabolic response. Under pathophysiologic conditions, the metabolic effects of catecholamines are less predictable because of changes in receptor affinity and density and in drug kinetics and the metabolic capacity of the major gluconeogenic organs, both resulting from the disease per se and the ongoing treatment. It is also well-established that shock states are characterized by a hypermetabolic condition with insulin resistance and increased oxygen demands, which coincide with both compromised tissue microcirculatory perfusion and mitochondrial dysfunction. This, in turn, causes impaired glucose utilization and may lead to inadequate glucose supply and, ultimately, metabolic failure. Based on the landmark studies on intensive insulin use, a crucial role is currently attributed to glucose homeostasis. This article reviews the effects of the various catecholamines on glucose utilization, both under physiologic conditions, as well as during shock states. Because, to date (to our knowledge), no patient data are available, results from relevant animal experiments are discussed. In addition, potential strategies are outlined to influence the catecholamine-induced effects on glucose homeostasis.

Catecholamines and vasopressin during critical illness

This article summarizes the effects of catecholamines and vasopressin on the cardiovascular system, focusing on their metabolic and immunologic properties. Particular attention is dedicated to the septic shock condition.

Dopexamine and norepinephrine versus epinephrine on gastric perfusion in patients with septic shock: a randomized study [NCT00134212]

Introduction

Microcirculatory blood flow, and notably gut perfusion, is important in the development of multiple organ failure in septic shock. We compared the effects of dopexamine and norepinephrine (noradrenaline) with those of epinephrine (adrenaline) on gastric mucosal blood flow (GMBF) in patients with septic shock. The effects of these drugs on oxidative stress were also assessed.

Methods

This was a prospective randomized study performed in a surgical intensive care unit among adults fulfilling usual criteria for septic shock. Systemic and pulmonary hemodynamics, GMBF (laser-Doppler) and malondialdehyde were assessed just before catecholamine infusion (T₀), as soon as mean arterial pressure (MAP) reached 70 to 80 mmHg (T₁), and 2 hours (T₂) and 6 hours (T₃) after T₁. Drugs were titrated from 0.2 μg kg^-1 min^-1 with 0.2 μg kg^-1 min^-1 increments every 3 minutes for epinephrine and norepinephrine, and from 0.5 μg kg^-1 min^-1 with 0.5 μg kg^-1 min^-1 increments every 3 minutes for dopexamine.

Results

Twenty-two patients were included (10 receiving epinephrine, 12 receiving dopexamine–norepinephrine). There was no significant difference between groups on MAP at T₀, T₁, T₂, and T₃. Heart rate and cardiac output increased significantly more with epinephrine than with dopexamine–norepinephrine, whereas. GMBF increased significantly more with dopexamine–norepinephrine than with epinephrine between T₁ and T₃ (median values 106, 137, 133, and 165 versus 76, 91, 90, and 125 units of relative flux at T₀, T₁, T₂ and T₃, respectively). Malondialdehyde similarly increased in both groups between T₁ and T₃.

Conclusion

In septic shock, at doses that induced the same effect on MAP, dopexamine–norepinephrine enhanced GMBF more than epinephrine did. No difference was observed on oxidative stress.

Catecholamines and vasopressin during critical illness

In critical care medicine, catecholamines are most widely used to reverse circulatory dysfunction and thus to restore tissue perfusion. However, catecholamines not only influence systemic and regional hemodynamics, but also exert a variety of significant metabolic, endocrine, and immunologic effects. Arginine vasopressin is a vasomodulatory hormone with potency to restore vascular tone in vasodilatory hypotension. Although the evidence supporting the use of low doses of vasopressin or its analogs in vasodilatory shock is increasing, lack of data regarding mortality and morbidity prevent their implementation in critical care protocols.

Blood flow, not hypoxia, determines intramucosal PCO2

Monitoring tissue hypoxia in critically ill patients is a challenging task. Tissue PCO2 has long been proposed as a marker of tissue hypoxia, although there is considerable controversy on whether the rise in CO2 with hypoxia is caused by anaerobic metabolism and excess CO2 production or by the accumulation of aerobically produced CO2 in the setting of blood flow stagnation. The prevention of increases in intestinal PCO2 in aggressively resuscitated septic animals supports the notion that tissue CO2 accumulation is a function of decreases in blood flow, not of tissue hypoxia.

[Main determinants of liver microcirculation during systemic inflammation]

More than 50% of all patients on intensive care units acquire a systemic inflammation such as systemic inflammatory response syndrome (SIRS) or sepsis. The development of hepatic microcirculatory failure with consecutive organ damage might occur during the course of the systemic inflammation. The liver microcirculation is regulated by a complex network of cellular components and specific mediators. The perfusion in liver sinusoids is regulated by the tonus of the contractile Ito cells. Nitric oxide (NO) and carbon monoxide (CO) influence each other and cause the Ito cells to dilate while endothelin results in a contraction of the Ito cells. On-going studies are investigating the role of angiotensin II, catecholamines and prostaglandins for the regulation of the hepatic microcirculatory system during systemic inflammation. Some investigations aim to determine the impact of sedatives and analgesics on the hepatic microcirculation in sepsis and SIRS. Therefore, a decisive recommendation about the choice and dosage of sedatives and analgesics for these patients is not possible. Nevertheless, ketamine, midazolam and fentanyl with their potential anti-inflammatory properties seem to be suitable for patients with systemic inflammation.