Dopexamine attenuates endotoxin-induced microcirculatory changes in rat mesentery: role of beta2 adrenoceptors

The Effect of β2-Adrenoceptor Agonists on Leucocyte-Endothelial Adhesion in a Rodent Model of Laparotomy and Endotoxemia

Background: The β₂-adrenoceptor agonist dopexamine may possess anti-inflammatory actions which could reduce organ injury during endotoxemia and laparotomy. Related effects on leucocyte-endothelial adhesion remain unclear.

Methods: Thirty anesthetized Wistar rats underwent laparotomy followed by induction of endotoxemia with lipopolysaccharide and peptidoglycan (n = 24) or sham (n = 6). Animals received dopexamine at 0.5 or 1 μg kg⁻¹ min⁻¹ (D0.5 and D1), salbutamol at 0.1 μg kg⁻¹ min⁻¹, or saline vehicle (Sham and Control) for 5 h. Intravital microscopy was performed in the ileum of the small intestine to assess leucocyteendothelial adhesion, arteriolar diameter, and functional capillary density. Global hemodynamics and biochemical indices of renal and hepatic function were also measured.

Results: Endotoxemia was associated with an increase in adherent leucocytes in post-capillary venules, intestinal arteriolar vasoconstriction as well-reduced arterial pressure and relative cardiac index, but functional capillary density in the muscularis was not significantly altered. Dopexamine and salbutamol administration were associated with reduced leucocyte-endothelial adhesion in post-capillary venules compared to control animals. Arteriolar diameter, arterial pressure and relative cardiac index all remained similar between treated animals and controls. Functional capillary density was similar for all groups. Control group creatinine was significantly increased compared to sham and higher dose dopexamine.

Conclusions: In a rodent model of laparotomy and endotoxemia, β₂-agonists were associated with reduced leucocyte-endothelial adhesion in post-capillary venules. This effect may explain some of the anti-inflammatory actions of these agents.

Increased β2-adrenergic vasorelaxation at the early phase of endotoxemic shock in rats

BACKGROUND AND PURPOSE

The early management of the cardiovascular dysfunction of septic shock is critical as it is associated with a poor outcome. Although the use of catecholamines is a common therapy in this syndrome, no data are available on the involvement of β-adrenoceptor (β-AR) subtypes and only few studies report an alteration of β-adrenergic-induced vasodilation in septic shock. The purpose of the study was to evaluate vascular β1, β2 and β3-AR expression and function in an endotoxemic rat model.

EXPERIMENTAL APPROACH

Endotoxemia was induced in rats by intravenous injection of lipopolysaccharide (LPS). β1, β2 and β3-AR mRNA expression was evaluated by RT-PCR in aorta and vascular β1, β2 and β3-AR responses were determined on conducting (aorta) and/or resistance (mesenteric and renal) arteries by constructing relaxation curves in response to different β-AR agonists.

RESULTS

The maximal effect of isoproterenol decreased by 31 to 61% in the three vascular beds of LPS-treated rats compared to controls. In aortas from LPS-treated rats, β1 and β3-AR mRNA expression was decreased and associated to a reduced β1 and β3-induced vasodilation. Conversely, albeit β2-AR mRNA was unchanged, the maximal β2-AR-induced vasodilation increased by 49% in aortas from LPS-treated rats compared to controls. This increase was not affected by endothelium removal but was abolished in the presence of a β2-AR antagonist or an adenylate cyclase inhibitor.

CONCLUSIONS

In endotoxemia, β2-AR vasodilation was increased by a potential recruitment of β2-AR located on smooth muscle cells. This study suggests that vascular β2-AR should be a putative new therapeutic target in septic shock.

Dopexamine can attenuate the inflammatory response and protect against organ injury in the absence of significant effects on hemodynamics or regional microvascular flow

Introduction

The effects of dopexamine, a β2-agonist, on perioperative and sepsis-related hemodynamic, microvascular, immune, and organ dysfunction are controversial and poorly understood. We investigated these effects in a rodent model of laparotomy and endotoxemia.

Methods

In two experiments, 80 male Wistar rats underwent laparotomy. In 64 rats, this was followed by administration of endotoxin; the remainder (16) underwent sham endotoxemia. Endotoxemic animals received either dopexamine at 0.5, 1, or 2 μg/kg/min or 0.9% saline vehicle (controls) as resuscitation fluid. The effects of dopexamine on global hemodynamics, mesenteric regional microvascular flow, renal and hepatic function and immune activation were evaluated.

Results

Endotoxin administration was associated with a systemic inflammatory response (increased plasma levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-10, as well as cell-adhesion molecules CD11a and CD11b), and increased pulmonary myeloperoxidase (MPO) activity (indicating pulmonary leukocyte infiltration), whereas biochemical changes demonstrated lactic acidosis with significant renal and hepatic injury. Dopexamine administration was associated with less-severe lactic acidosis (pooled dopexamine versus controls, (lactate, 2.2 mM ± 0.2 mM versus 4.0 mM ± 0.5 mM; P < 0.001) and reductions in the systemic inflammatory response (pooled dopexamine versus control, 4 hour (TNF-α): 324 pg/ml ± 93 pg/ml versus 97 pg/ml ± 14 pg/ml, p < 0.01), pulmonary myeloperoxidase (MPO) activity, and hepatic and renal injury (pooled dopexamine versus control (ALT): 81 IU/L ± 4 IU/L versus 138 IU/L ± 25 IU/L; P < 0.05; (creatinine): 49.4 μM ± 3.9 μM versus 76.2 μM ± 9.8 μM; P < 0.005). However, in this study, clinically relevant doses of dopexamine were not associated with clinically significant changes in MAP, CI, or gut regional microvascular flow.

Conclusions

In this model, dopexamine can attenuate the systemic inflammatory response, reduce tissue leukocyte infiltration, and protect against organ injury at doses that do not alter global hemodynamics or regional microvascular flow. These findings suggest that immunomodulatory effects of catecholamines may be clinically significant when used in critically ill surgical patients and are independent of their hemodynamic actions.

Use of inotropes and vasopressor agents in critically ill patients

Inotropes and vasopressors are biologically and clinically important compounds that originate from different pharmacological groups and act at some of the most fundamental receptor and signal transduction systems in the body. More than 20 such agents are in common clinical use, yet few reviews of their pharmacology exist outside of physiology and pharmacology textbooks. Despite widespread use in critically ill patients, understanding of the clinical effects of these drugs in pathological states is poor. The purpose of this article is to describe the pharmacology and clinical applications of inotropic and vasopressor agents in critically ill patients.

Modulation of 11β-hydroxysteroid dehydrogenase 1 by β2-adrenoceptor in the ischaemia-reperfused rat kidney

BACKGROUND

11β-Hydroxysteroid dehydrogenase Type 1 (11βHSD-1) amplifies intracellular levels of active glucocorticoids which possess protective effects against organ ischaemia and reperfusion (I/R). However, the mechanisms by which 11βHSD-1 is modified after a renal I/R challenge remain unclear. This study investigated the effect of β(2)-adrenoceptor (β(2)-AR) activation and the subsequent signalling pathways on renal 11βHSD-1 gene expression following renal I/R.

METHODS

Renal I/R was induced using 25 min of bilateral renal artery occlusion in 4-week-old Wistar rats followed by an intraperitoneal injection of various doses of adeno-β(2)-AR gene. Following renal I/R, kidneys, plasma and urine were collected to assay 11βHSD messenger RNA (mRNA) levels, β(2)-AR signalling cascades and renal function.

RESULTS

On the second day after the renal I/R challenge, there was a reduction in renal 11βHSD-1 mRNA levels associated with a decrease in stimulatory G protein α (Gsα) and adenylate cyclase-1 (ACY-1) in the kidney. The addition of the adeno-β(2)-AR gene resulted in greater increases in 11βHSD-1 mRNA and β(2)-AR-Gsα-ACY-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) activity in the kidney but had no effect on 11βHSD-2 mRNA or protein kinase C levels in the kidney.

CONCLUSIONS

Over-expression of β(2)-AR resulting from the gene delivery improved renal function and 11βHSD-1 production following renal I/R, which were actions exerted through the cAMP-PKA pathway. The stimulatory effect of functional β(2)-AR activation on renal 11βHSD-1 expression may offer a means of protection from renal I/R injury.

Prevention, diagnosis, therapy and follow-up care of sepsis: 1st revision of S-2k guidelines of the German Sepsis Society (Deutsche Sepsis-Gesellschaft e.V. (DSG)) and the German Interdisciplinary Association of Intensive Care and Emergency Medicine (Deutsche Interdisziplinäre Vereinigung für Intensiv- und Notfallmedizin (DIVI))

Practice guidelines are systematically developed statements and recommendations that assist the physicians and patients in making decisions about appropriate health care measures for specific clinical circumstances taking into account specific national health care structures. The 1^st revision of the S-2k guideline of the German Sepsis Society in collaboration with 17 German medical scientific societies and one self-help group provides state-of-the-art information (results of controlled clinical trials and expert knowledge) on the effective and appropriate medical care (prevention, diagnosis, therapy and follow-up care) of critically ill patients with severe sepsis or septic shock. The guideline had been developed according to the “German Instrument for Methodological Guideline Appraisal” of the Association of the Scientific Medical Societies (AWMF). In view of the inevitable advancements in scientific knowledge and technical expertise, revisions, updates and amendments must be periodically initiated. The guideline recommendations may not be applied under all circumstances. It rests with the clinician to decide whether a certain recommendation should be adopted or not, taking into consideration the unique set of clinical facts presented in connection with each individual patient as well as the available resources.

Is dopexamine superior to dopamine in the treatment of multiple trauma patients--a prospective, double-blind, randomised study

BACKGROUND

The goal of this prospective, randomised, double-blind clinical trial study was to assess the effects of dopexamine hydrochloride on organ failure, inflammatory mediators and splanchnic oxygenation in blunt multiple trauma patients at high risk of multiple organ dysfunction syndrome (MODS).

METHODS

We performed a prospective randomised controlled trial on 30 consecutive blunt multiple trauma patients with ISS>or=16, age 18-60 years and initial blood pressure >or=120 mmHg initially admitted to our level I trauma centre. Patients were randomised to treatment with dopamine (n=15) or dopexamine (n=15) for 48 h after admission. Outcome in terms of mortality, MODS, splanchnic perfusion, complications, duration of stay was statistically analysed.

RESULTS

Dopexamine treatment was associated with impaired organ function and an increased duration of ventilation and ICU stay compared with patients who received dopamine treatment. The acute inflammatory response was increased in the Dopexamine group while a decreased pHi and MEGX formation and increased serum lactate levels were measured.

CONCLUSIONS

The indication to use dopexamine hydrochloride appears questionable. In the absence of an antiinflammatory effect, dopexamine demonstrated a disadvantageous ICU course in regards to the organ function and the duration of treatment. In addition, a decreased pHi and MEGX formation suggested a deterioration of splanchnic oxygenation.

Effects of terbutaline on circulatory failure and organ dysfunction induced by peritonitis in rats

OBJECTIVE

The pathogenesis of multiple organ dysfunction syndrome (MODS) in septic shock is mainly caused by maldistribution of tissue perfusion and the amplification of inflammatory responses, which may be modulated by beta(2)-adrenoceptor agonists. We evaluated and compared effects of terbutaline on MODS in a cecal ligation and puncture (CLP) model of sepsis.

DESIGN AND SETTING

Prospective controlled animal study in a university laboratory.

METHODS

Male adult Wistar rats received CLP or sham operation followed by the administration of saline or terbutaline (0.3 mg/kg i.v. at 3 and 9 h after CLP).

MEASUREMENTS AND RESULTS

At 0, 9 and 18 h after CLP, the changes of hemodynamics, organ function indexes, as well as the plasma interleukin-1beta (IL-1beta) and nitrite/nitrate levels were examined. At 18 h after CLP, animals were killed and their lungs, livers and kidneys were immediately excised to analyze superoxide anion (O(2) (-)) levels and inducible nitric oxide synthase (iNOS) expression. These organs were also evaluated by pathological study. Terbutaline significantly (1) prevented delayed hypotension and reduced hepatic and renal dysfunction, (2) diminished plasma IL-1beta and nitrite/nitrate, lung iNOS expression, tissue O(2) (-) level and the infiltration of neutrophils in the lung and the liver, and (3) improved the 18-h survival rate.

CONCLUSIONS

Terbutaline may be developed as an alternative treatment for severe sepsis-induced MODS. The protective effect of terbutaline seems to be through inhibition of proinflammatory mediators and attenuation of oxidant production.

[Diagnosis and therapy of sepsis]

A recent survey conducted by the publicly funded Competence Network Sepsis (Sep- Net) reveals that severe sepsis and/or septic shock occurs in 75,000 inhabitants (110 out of 100,000) and sepsis in 79,000 inhabitants (116 out of 100,000) in Germany annually. This illness is responsible for approx. 60,000 deaths and ranges as the third most frequent cause of death after acute myocardial infarction. Direct costs for the intensive care of patients with severe sepsis alone amount to approx. 1.77 billion euros, which means that about 30% of the budget in intensive care is used to treat severe sepsis. However, until now German guidelines for the diagnosis and therapy of severe sepsis did not exist. Therefore, the German Sepsis Society initiated the development of guidelines which are based on international recommendations by the International Sepsis Forum (ISF) and the Surviving Sepsis Campaign (SSC) and take into account the structure and organisation of the German health care system. Priority was given to the following guideline topics: a) diagnosis, b) prevention, c) causative therapy, d) supportive therapy, e) adjunctive therapy. The guidelines development process was carefully planned and strictly adhered to according to the requirements of the Working Group of Scientific Medical Societies (AWMF).

Review article: bacterial translocation in the critically ill--evidence and methods of prevention

BACKGROUND

Delayed sepsis, systemic inflammatory response syndrome (SIRS) and multiorgan failure remain major causes of morbidity and mortality on intensive care units. One factor thought to be important in the aetiology of SIRS is failure of the intestinal barrier resulting in bacterial translocation and subsequent sepsis.

AIM

This review summarizes the current knowledge about bacterial translocation and methods to prevent it.

METHODS

Relevant studies during 1966-2006 were identified from a literature search. Factors, which detrimentally affect intestinal barrier function, are discussed, as are methods that may attenuate bacterial translocation in the critically ill patient.

RESULTS

Methodological problems in confirming bacterial translocation have restricted investigations to patients undergoing laparotomy. There are only limited data available relating to specific interventions that might preserve intestinal barrier function or limit bacterial translocation in the intensive care setting. These can be categorized broadly into pre-epithelial, epithelial and post-epithelial interventions.

CONCLUSIONS

A better understanding of factors that influence translocation could result in the implementation of interventions which contribute to improved patient outcomes. Glutamine supplementation, targeted nutritional intervention, maintaining splanchnic flow, the judicious use of antibiotics and directed selective gut decontamination regimens hold some promise of limiting bacterial translocation. Further research is required.

Synthetic inotropes inhibit the expression of adhesion molecules and augment the expression of L-selectin in polymorphonuclear neutrophils

OBJECTIVES

To elucidate differential functional and phenotypic changes in response to clinically relevant synthetic inotropes plus the generation of oxidative free radicals by polymorphonuclear neutrophils (PMN), and changes in the expression of L-selectin and Mac-1 on the surface of PMN were examined in the presence of dobutamine and dopexamine in pharmacological concentrations.

DESIGN

Prospective, in vitro study.

SETTING

Research laboratory.

SUBJECTS

Human PMN obtained from healthy donors.

INTERVENTIONS

PMN were pretreated with dobutamine 147.99 nM or 147,990 nM, or dopexamine 100 nM or 100,000 nM, followed by stimulation with FMLP. Stimulated neutrophils were incubated with antibiodies against CD11b or CD62l and assessed by flow cytometry. Additional probes were assessed by flow cytometry for the generation of oxidative free radicals.

MEASUREMENTS AND MAIN RESULTS

Low concentrations of both synthetic inotropes significantly inhibit the suppression of CD62l expression following stimulation with N-formyl-l-methionyl-l-leucyl-l-phenylalanine; high concentrations antagonize this effect. High concentrations of both synthetic inotropes suppresses the expression of CD11b. Neither dobutamine nor dopexamine modified the generation of oxidative free radicals.

CONCLUSIONS

While the upregulation of Mac-1 expression is inhibited in a dose-dependent manner, the expression of L-selectin is enhanced at low concentrations of dobutamine and dopexamine and partly counter-regulated at high concentrations. It seems that synthetic inotropes can modulate the immunomodulatory ability by inhibition of PMN rolling and modification of PMN adherence and diapedese.

[Diagnosis and therapy of sepsis. Guidelines of the German Sepsis Society Inc. and the German Interdisciplinary Society for Intensive and Emergency Medicine]

A recent survey conducted by the publicly funded Competence Network Sepsis (SepNet) reveals that severe sepsis and/or septic shock occurs in 75,000 inhabitants (110 out of 100,000) and sepsis in 79,000 inhabitants (116 out of 100,000) in Germany annually. This illness is responsible for approximately 60,000 deaths and ranges as the third most frequent cause of death after acute myocardial infarction. Direct costs for the intensive care of patients with severe sepsis alone amount to approximately 1.77 billion euros, which means that about 30% of the budget in intensive care is used to treat severe sepsis. However, until now German guidelines for the diagnosis and therapy of severe sepsis did not exist. Therefore, the German Sepsis Society initiated the development of guidelines which are based on international recommendations by the International Sepsis Forum (ISF) and the Surviving Sepsis Campaign (SSC) and take into account the structure and organization of the German health care system. Priority was given to the following guideline topics: a) diagnosis, b) prevention, c) causative therapy, d) supportive therapy, e) adjunctive therapy. The guidelines development process was carefully planned and strictly adhered to the requirements of the Working Group of Scientific Medical Societies (AWMF).

Effects of dopexamine on the intestinal microvascular blood flow and leukocyte activation in a sepsis model in rats

INTRODUCTION

The administration of dopexamine may constitute a therapeutical option to improve hepatosplanchnic perfusion in sepsis. In order to verify this hypothesis, we administered dopexamine in an experimental sepsis model in rats.

METHODS

This prospective, randomized, controlled laboratory study was conducted in 42 Wistar rats. The animals were divided into 3 groups. Group 1 (CON group) served as control group. The Animals of groups 2 (LPS Group) and 3 received an endotoxin infusion (20 mg/kgfor 15 min). In addition, in group 3 (DPX group) dopexamine was administered 0.5 microg/kg/minover 4 hours. One half of the animals of each group underwent studies of intestinal microvascular blood flow (IMBF) using laser Doppler fluxmetry. In the other half an intravital microscopic evaluation of the leukocyte endothelium cell interaction in the intestinal microcirculation was performed. Functional capillary denstity (FCD) in the intestinal mucosaand the circular as well as the longitudinal muscle layer was estimated.

RESULTS

One hour after endotoxin challenge IMBF decreased significantly in the untreated LPS group to 51% compared to baseline (p<0.05). In DPX treated endotoxin animals we found significantly higher values at the level of CON group. The after endotoxin challenge impaired FCD was improved by dopexamine in the longitudinal (DPX + 33% vs. LPS; p <0.05) and in the circular muscle layer (DPX + 48% vs. LPS; p < 0.05) as a result of dopexamine administration. The administration of dopexamine reduced the count of firmly adherent leukocytes when compared to the untreated LPS group (-31%, p<0.05). TNF-alpha plasma levels were reduced by dopexamine infusion (LPS group 3637 +/- 553 pg/mL; DPXgroup 1933 +/- 201 pg/mL) one hour after endotoxin challenge.

CONCLUSIONS

The administration of dopexamine improved IMBF and FCD as parameters of intestinal microcirculation and reduced leukocyte activation as a parameter of inflammation in experimental sepsis.

Hydroxymethylglutaryl co-enzyme A reductase inhibition attenuates endotoxin-mediated inflammatory responses

Background

The aim of this study was to investigate whether inhibition of hydroxymethylglutaryl co-enzyme A reductase attenuates leucocyte–endothelial cell interactions and alters expression of endothelial constitutive nitric oxide synthase (ecNOS) and inducible nitric oxide synthase (iNOS) following exposure to endotoxin.

Methods

Male Sprague–Dawley rats were randomized into control, lipopolysaccharide (LPS) and pravastatin + LPS groups (seven per group). Pravastatin sodium was gavaged at 0·4 mg per kg per day for 5 days, after which LPS 15 mg/kg was administered via the jugular vein. Intravital microscopy was used to determine leucocyte–endothelial cell interactions.

Results

Following the administration of LPS there was a significant reduction in leucocyte rolling velocity at 10 min (mean(s.e.m.) 69(3) versus 102(6) per cent of baseline value; P = 0·041), an increase in the number of adherent leucocytes at 10 min (4·5(0·5) versus 2·8(0·3) per 100 µm; P = 0·044) and an increase in the number of leucocytes undergoing transendothelial migration at 30 min (4·2(0·4) versus 1·7(0·4) per field; P = 0·008) compared with controls. Pretreatment with pravastatin significantly attenuated LPS-induced leucocyte–endothelial cell interactions (rolling velocity 89(6) per cent at 10 min, P = 0·038; adherent leucocytes 3·0(0·5) per 100 µm at 10 min, P = 0·038; migrating leucocytes 1·9(0·5) per field at 30 min, P = 0·001). This endothelial protection was associated with maintenance of ecNOS and reduced iNOS expression within mesenteric tissues.

Conclusion

These data show that pravastatin produces anti-inflammatory effects in response to injurious stimuli by attenuation of leucocyte–endothelial cell interactions.

[Beta 2-adrenoceptor function in the kidney]

The majority of beta(2)-adrenoceptor (beta(2)-AR) agonists is eliminated via the kidneys as an unchanged substance. It is likely that such agents will exert pharmacological effects during their passage through the nephron. However, these pharmacological effects have, to our knowledge, not been taken into consideration when using these compounds in clinical practice because the role of beta(2)-AR in the regulation of renal function remains unclear. Renal beta(2)-ARs are predominantly localized to the proximal tubular epithelia and the membranes of smooth muscle cells from renal arteries. From this morphologic evidence, it is proposed that beta(2)-AR activation may regulate glomerular function and thereby sodium and water balance in the nephron segments. Actually, beta(2)-AR agonists given acutely cause a marked decrease in glomerular filtration rate. On the other hand, beta(2)-AR agonists inhibit the renal production of inflammatory cytokines such as TNF-alpha. Furthermore, the administration of beta(2)-AR agonists is found to attenuate apoptosis associated with shigatoxin in the hemolytic uremic syndrome (HUS). Increased understanding of the pharmacological basis of beta(2)-AR function in the kidney provides important new information relevant to the clinical use of beta(2)-AR agonists in airway diseases and potential applications of these drugs in renal inflammation and injury associated with sepsis or HUS.

Dopexamine and cellular immune functions during systemic inflammation

An immune-neuroendocrine interaction that is mediated via beta2-adrenergic receptors has been demonstrated previously. Dopexamine is a substance with strong beta2-adrenergic effects and is used in the treatment of critically ill patients. We therefore investigated the effect of dopexamine infusion on survival and cellular immune functions during systemic inflammation. Sepsis (CLP) was induced in male NMRI mice that received either 0.9% saline, dopexamine (0.05 mg/kg/hour ip, DPX), the selective beta2-adrenergic antagonist ICI 118.551 (0.5 mg/kg ip every 12 hours, ICI) or a combination of both drugs. 48 hours after onset of sepsis, survival rate, splenocyte apoptosis, splenocyte proliferation, splenocyte IL-2, IL-6 and IFN-gamma release, and leukocyte distribution were monitored. Dopexamine increased splenocyte apoptosis and normalized the distribution of circulating lymphocytes but did not affect sepsis-induced mortality. ICI 118.551 induced a dramatic increase of mortality paralleled by a decreased splenocyte proliferation and the strongest increase in splenocyte apoptosis. Co-administration of dopexamine abolished the ICI 118.551-induced alterations but this effect seemed to be mediated via a pathway other than adrenergic beta2-receptors. We conclude that dopexamine modulates cellular immune functions during systemic inflammation and that different receptor systems are involved in the mediation of this process. Furthermore, the immunomodulatory effect of beta2-adrenergic blockade was demonstrated.

Effect of adding dopexamine to intraoperative volume expansion in patients undergoing major elective abdominal surgery † †This article is accompanied by the Editorial

BACKGROUND

The contribution of low-dose dopexamine to outcome, when given to increase cardiac output in patients already treated with fluids during major abdominal surgery, is not yet known.

METHOD

We carried out a randomized double-blind placebo-controlled trial. All 100 patients studied were given fluid infusions during surgery guided by stroke volume measurements made with an oesophageal Doppler probe. Patients were randomized to receive dopexamine at the rate of 0.25 microg kg(-1) min(-1) or saline 0.9% (control) for the first 24 h after the start of surgery. The primary outcome measure was the incidence of postoperative morbidity.

RESULTS

There were no statistically significant differences between groups in the incidence of postoperative complications, the length of hospital stay, the incidence of morbidity and the use of critical care facilities. The patients randomized to receive dopexamine had significantly more pre-existing disease than the control patients. Mortality in both groups was significantly less than predicted by the POSSUM (Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity) risk prediction score.

CONCLUSION

We could not demonstrate an advantage to using low-dose dopexamine in high-risk patients during major abdominal surgery.

Dopexamine, dobutamine, and dopamine increase splanchnic blood flow: what is the evidence?

Inadequate splanchnic perfusion in the critically ill compromises the gut barrier leading to bacterial translocation, which is postulated to cause multiorgan dysfunction and failure. Inotropic agents such as dopexamine, dobutamine, and dopamine may have a role in increasing splanchnic perfusion, thereby protecting this area from further injury. This article examines the evidence for using these agents in patients with sepsis, postoperative trauma, and in those undergoing cardiac surgery and mechanical ventilation to increase gut perfusion and prevent multiple organ failure. Systemic effects of these agents differ from regional effects and must be considered when selecting therapy.

Soluble L-selectin attenuates tumor necrosis factor-alpha-mediated leukocyte adherence and vascular permeability: a protective role for elevated soluble L-selectin in sepsis

OBJECTIVE

We have previously demonstrated that leukocyte delivery to remote sites is decreased in sepsis and that increased concentrations of soluble L-selectin are, in part, responsible for this finding. Given that leukocytes have been implicated in the pathogenesis of vascular leakage, we hypothesized that the elevated soluble L-selectin concentrations in sepsis may translate into decreased inflammation-mediated leukocyte-endothelial cell interactions and vascular leakage at these sites.

DESIGN

Prospective, controlled animal study.

SETTING

Surgical research laboratory in a university hospital.

SUBJECTS

Swiss white male mice weighing 25-35 g.

INTERVENTIONS

Mice were randomized to one of three study groups: intracremaster tumor necrosis factor-alpha with subsequent intravenous bicarbonate buffered solution; intracremaster tumor necrosis factor-alpha with intravenous soluble L-selectin (10 microg/mL); and intracremaster bicarbonate buffered solution with intravenous bicarbonate buffered solution. The cremaster muscle was prepared for both light and fluorescence intravital microscopy 2 hrs after intracremaster injection, and fluorescein isothiocyanate-labeled albumin was injected intravenously. Leukocyte-endothelial interactions (rolling flux, rolling velocity, and adherence) were counted off-line. Postcapillary venule leakage was determined by the permeability index (perivenular/intravenular fluorescence) after intravenous injection of fluorescent albumin.

MEASUREMENTS AND MAIN RESULTS

Soluble L-selectin significantly attenuated tumor necrosis factor-alpha-mediated increases in leukocyte adherence and vascular leakage. Leukocyte rolling velocity was restored to baseline with soluble L-selectin; however, rolling flux was not altered. Blood pressure, shear rate, and leukocyte counts did not differ between groups.

CONCLUSIONS

Soluble L-selectin decreases local inflammation-mediated leukocyte adherence and vascular leakage in vivo. The increased concentrations of soluble L-selectin in sepsis may represent a protective mechanism by which the host attempts to diminish the deleterious systemic effects of activated leukocytes during sepsis.

Dopexamine but not dopamine increases gastric mucosal oxygenation during mechanical ventilation in dogs

OBJECTIVE

To compare the effects of dopamine and dopexamine on gastric mucosal oxygenation during mechanical ventilation without and with positive end-expiratory airway pressure (PEEP) and after compensation of the PEEP-induced hemodynamic suppression.

DESIGN

Randomized controlled animal study.

SETTING

University research department of experimental anesthesiology.

SUBJECTS

Ten anesthetized dogs with chronically implanted ultrasound flow probes around the pulmonary artery for continuous measurement of cardiac output.

INTERVENTIONS

On different days, the dogs randomly received dopamine (2.5 and 5.0 microg x kg(-1) x min(-1), n = 10), dopexamine (0.5 and 1.0 microg x kg(-1) x min(-1)) without (n = 8) or with pretreatment with a selective beta2-adrenoceptor antagonist (ICI 118,551, n = 7), or saline (control, n = 7). To simulate common clinical situations, these interventions were performed during different ventilation modes: during mechanical ventilation without and with high levels of PEEP, and after compensation of the PEEP-induced systemic hemodynamic suppression by titrated volume resuscitation with hydroxyethyl starch.

MEASUREMENTS AND MAIN RESULTS

We continuously measured microvascular hemoglobin saturation (mu-Hbo2) by light-guide spectrophotometry in the gastric mucosa. Dopexamine, but not dopamine, significantly increased gastric mucosal mu-Hbo2 by about 20%, regardless of the dose and the ventilation mode. Both catecholamines dose-dependently increased cardiac output and oxygen delivery by up to 75% without effects on systemic oxygen saturation. The effects of dopexamine on mu-Hbo2 as well as on cardiac output and oxygen delivery were prevented by selective beta2-adrenoceptor-blockade.

CONCLUSIONS

Dopexamine but not dopamine improved gastric mucosal oxygenation in dogs. This effect was independent of the dosage and the ventilation mode. Thus, dopexamine may reverse a decrease in splanchnic oxygenation induced by ventilation with PEEP. The dopexamine-induced increase in gastric mucosal oxygenation was mediated by beta2-adrenoceptors, which explains the superior effects of dopexamine to dopamine on mu-Hbo2. The regional effects of both catecholamines were not mirrored by systemic hemodynamics.

Effects of dobutamine and dopexamine on hepatic micro- and macrocirculation during experimental endotoxemia: an intravital microscopic study in the rat

OBJECTIVE

To test the effects of dobutamine and dopexamine on hepatic portal and sinusoidal blood flow in a model of normodynamic endotoxemia.

DESIGN

Randomized, controlled trial.

SETTING

Experimental laboratory.

SUBJECTS

Male Wistar rats (250-350 g).

INTERVENTIONS

A total of 40 male Wistar rats were randomized into four groups: a control group, which only received Ringer's solution; an endotoxin group, which received a continuous infusion of 2 mg/kg body weight (bw)/hr of endotoxin; a dobutamine group, which received endotoxin and a continuous infusion of dobutamine (3 microg/kg bw/min); and a dopexamine group, which received endotoxin and dopexamine (2 microg/kg bw/min). The experimental period was 120 min.

MEASUREMENTS AND MAIN RESULTS

Mean arterial blood pressure (MAP), heart rate (HR), and cardiac output (CO) were detected. Portal blood flow was measured using an ultrasonic flow probe positioned around the portal vein, and sinusoidal blood flow was detected in the left liver lobe using intravital microscopy. All detected variables remained stable in the control group. In the endotoxin group, HR increased significantly and MAP decreased significantly from 111 +/- 10 mm Hg to 95 +/- 8 mm Hg at 120 mins, whereas CO remained unchanged. Both in the dobutamine and the dopexamine group HR increased and MAP decreased more than in the endotoxin group. CO increased in both groups significantly. Portal blood flow (23 +/- 4 mL/min to 16 +/- 3 mL/min) and sinusoidal blood flow (38.6 +/- 2.5 to 22.8 +/- 1.2 10(3) microm(3)/sec) decreased significantly in the endotoxin group. In the dobutamine and the dopexamine group portal and sinusoidal blood flow remained at baseline values.

CONCLUSIONS

In our model of endotoxemia, dobutamine and dopexamine preserved systemic and hepatic blood flow. These preservations of hepatic blood flow during endotoxemia could portend beneficial effects but need to be studied further.

A randomized study to evaluate the effect of a perioperative infusion of dopexamine on colonic mucosal ischemia after aortic surgery

PURPOSE

Colonic ischemia after aortic surgery is associated with increased mortality and morbidity rates. This study was conducted as a single-center side arm to a multicenter, randomized, placebo-controlled study to evaluate the effect of dopexamine hydrochloride on its incidence.

METHODS

Thirty patients, mean age 65.1 years (range, 46-84), undergoing elective infrarenal aortic surgery were entered. Preoperative hemodynamic and respiratory parameters were optimized. Patients were then randomly assigned to receive a perioperative infusion of dopexamine at 2 microg/kg per minute (n = 12) or 0.9% saline placebo (n = 18). All patients underwent colonoscopy and biopsy preoperatively and 1 week postoperatively. Specimens were assessed for evidence of mucosal ischemia, presence of mast cell tryptase, myeloperoxidase activity, and both the inducible and endothelial isoforms of nitric oxide synthase.

RESULTS

There was no significant difference in perioperative fluid and blood requirements or hemodynamic and respiratory parameters between the two groups. However, there was significantly less evidence of mucosal ischemic changes in dopexamine-treated patients (n = 1) compared with placebo (n = 8) (P =.049). Furthermore, when preoperative biopsies were compared with those performed 1 week postoperatively, nine (50%) patients in the placebo group and two (16.7%) in the dopexamine group scored worse. Although there was no significant difference in inflammatory markers between the two groups, both mast cell tryptase and myeloperoxidase expression were increased in patients with histologic evidence of ischemia (P <.05). Furthermore, inducible nitric oxide synthase staining within the vascular (P =.001) and lamina propria (P <.05) components of the mucosa was also significantly greater.

CONCLUSION

A perioperative dopexamine infusion affords significant histologic protection to colonic mucosa after aortic surgery.

Milrinone improves intestinal villus blood flow during endotoxemia

PURPOSE

To determine whether the compromised intestinal villus blood flow in a rat model of endotoxemia could be improved by continuous infusion of the phosphodiesterase (PDE) inhibitor milrinone.

METHODS

Twenty-four anesthetized and ventilated rats were laparotomized and an ileal portion was exteriorized and opened by an antimesenteric incision. The ileal segment was fixed with the mucosal surface upward. Microcirculatory parameters were assessed by intravital videomicroscopy. The animals were randomly assigned to receive one of three treatments: infusion of Escherichia coli lipopolysaccharides without phosphodiesterase inhibitor pretreatment (=LPS group); or infusion of LPS with milrinone pretreatment (= milrinone group), or without infusion of LPS or milrinone (=control group). Macrohemodynamic parameters (MAP, HR) and microhemodynamic parameters of ileal mucosa (mean diameter of central arterioles = D(A) and mean erythrocyte velocity within the arterioles= V(E)) were measured 30 min before and at 0, 60, and 120 min after induction of endotoxemia. Mucosal villus blood flow was calculated from D(A) and V(E).

RESULTS

In the milrinone group MAP decreased 60 min after induction of endotoxemia whereas it remained stable in the control and the LPS group. In both groups given endotoxin V(E) decreased after start of LPS infusion. In contrast, D(A) decreased in the LPS group, but increased in the milrinone group after 120 min of endotoxemia. Thus, the endotoxin-induced decrease of intestinal villus blood flow was diminished but not fully restored by milrinone infusion.

CONCLUSION

Our results indicate that milrinone has some beneficial microcirculatory effects during endotoxemia. Although it contributed to systemic hypotension, it attenuated intestinal mucosal hypoperfusion.

Effect of dopexamine on intestinal tissue concentrations of high-energy phosphates and intestinal release of purine compounds in endotoxemic rats

OBJECTIVES

To determine the effect of dopexamine, a synthetic catecholamine ligand for dopaminergic and beta2-adrenergic receptors, on intestinal release of adenosine 5'-triphosphate (ATP) degradation products and on intestinal tissue concentrations of high-energy phosphates during endotoxemia.

DESIGN

Randomized, controlled trial.

SETTING

Experimental laboratory.

SUBJECTS

Twenty-one male Wistar rats.

INTERVENTIONS

Rats given endotoxin (Escherichia coli lipopolysaccharide [LPS]; 1.5 mg/kg i.v. over 60 mins) were treated with a continuous infusion of dopexamine (DPX; 2.5 microg/kg/min, n = 7, group LPS + DPX) or 0.9% saline (n = 7, group LPS) during a study period of 120 mins. Animals in the control group (n = 7) received a volume-equivalent infusion of 0.9% saline without endotoxin.

MEASUREMENTS AND MAIN RESULTS

In all groups, arterial and portal venous concentrations of adenosine, hypoxanthine, and uric acid were measured at baseline and at 60 and 120 mins after the endotoxin challenge, and we calculated the portal venous/arterial concentration differences as an indicator of the intestinal release of the purine compounds. Furthermore, at the end of the study, the intestinal tissue concentrations of the high-energy phosphates ATP, adenosine 5'-diphosphate (ADP), adenosine 5'-monophosphate (AMP), creatine phosphate, and adenosine were determined, and we calculated the adenine nucleotide pool, the ATP/ADP and AMP/adenosine ratios, and the adenylate energy charge of the intestinal tissue. Endotoxemia decreases intestinal tissue ATP, ADP, AMP, and creatine phosphate concentrations, increases tissue adenosine content, and increases the release of hypoxanthine and uric acid from the intestinal tract. Dopexamine attenuates the endotoxin-induced decrease of the intestinal tissue adenine nucleotide pool, the AMP/adenosine ratio, and the release of the ATP-degradation products hypoxanthine and uric acid from the intestinal tract.

CONCLUSIONS

Normotensive endotoxemia is associated with a deterioration of the intestinal energy balance and an increased release of ATP degradation products, indicating intestinal tissue ischemia. Furthermore, these results suggest the beneficial effects of dopexamine on pathophysiologic alterations of the intestinal energy metabolism during endotoxemia.

Effect of a dopexamine-induced increase in cardiac index on splanchnic hemodynamics in septic shock

In 12 patients with hyperdynamic septic shock we studied the effect of dopexamine, a combined dopamine and beta-adrenergic agonist, on hepatosplanchnic hemodynamics and O(2) exchange. All patients required noradrenaline to maintain mean arterial pressure > 60 mm Hg (noradrenaline >/= 0.04 microg x kg(-1) x min(-1)) with a cardiac index >/= 3.0 L/min/m(2). Splanchnic blood flow (Qspl) was measured using primed continuous infusion of indocyanine green dye with hepatic venous sampling. In addition tonometric gastric mucosal-arterial and gastric mucosal-hepatic venous P CO(2) gradients were assessed as indicators of regional energy balance. After 90 min of stable hemodynamics a first measurement was obtained. Then dopexamine infusion was titrated (1-4 microg x kg(-1) x min(-1)) to increase cardiac output by approximately 25% (20-30%). After 90 min all measurements were repeated, and dopexamine was withdrawn followed by a third measurement. Median Qspl (0.86/1.23-0. 66 versus 0.96/1.42-0.85 L/min/m (2) [median value/25th-75th percentiles], p < 0.05) increased whereas the fractional contribution of Qspl to total blood flow decreased (21/28-13 versus 19/28-12%, p < 0.05). Although both global and regional oxygen delivery (DO(2)) consistently increased, neither global or regional V O(2) nor PCO(2) gradients were significantly affected. In patients with septic shock and ongoing noradrenaline treatment dopexamine seems to have no preferential effects on hepatosplanchnic hemodynamics, O(2) exchange, or energy balance.