Compared with crystalloid, colloid therapy slows progression of extrapulmonary tissue injury in septic sheep

Recombinant thrombomodulin may protect cardiac capillary endothelial glycocalyx through promoting Glypican-1 expression under experimental endotoxemia

Introduction

Myocardial dysfunction occurs in patients with sepsis due to vascular endothelial injury. Recombinant human thrombomodulin (rhTM) attenuates vascular endothelial injuries through endothelial glycocalyx (eGC) protection.

Hypothesis

We hypothesized that rhTM attenuates myocardial dysfunction via the inhibition of vascular endothelial injury during sepsis.

Methods

Ten-week-old male C57BL6 mice were injected intraperitoneally with 20 mg/kg of lipopolysaccharide (LPS). In rhTM-treated mice, rhTM was injected intraperitoneally at 3 and 24 h after LPS injection. Saline was injected intraperitoneally as control. To assess for eGC injury, intensity score was measured 48 h after the LPS injection. To confirm vascular endothelial injuries, ultrastructural analysis was performed using scanning (SEM) and transmission electron microscopy (TEM).

Results

The survival rate of the rhTM group at 48 h after LPS injection was significantly higher than that of the control group (68% vs. 17%, p < 0.05). The serum level of troponin I in the rhTM group was lower than that in the control (2.2 ± 0.4 ng/dL vs 9.4 ± 1.1 ng/dL, p < 0.05). The expression of interleukin-6 (IL-6) was attenuated in the rhTM-treated group than in the control (65.3 ± 15.3 ng/mL vs 226.3 ± 19.4 ng/mL, p < 0.05). The serum concentration of syndecan-1, a marker of glycocalyx damage, was significantly decreased 48 h post-administration of LPS in the rhTM-treated group than in the control group. In ultrastructural analysis using SEM and TEM, eGC peeled off from the surface of the capillary lumen in the control. Conversely, the eGC injury was attenuated in the rhTM group. Gene set enrichment analysis revealed that osteomodulin, osteoglycin proline/arginine-rich end leucine-rich repeat protein, and glypican-1, which are proteoglycans, were preserved by rhTM treatment. Their protein expression was retained in endothelial cells.

Conclusion

rhTM attenuates sepsis-induced myocardial dysfunction via eGC protection.

Neutrophil Elastase Inhibition Ameliorates Endotoxin-induced Myocardial Injury Accompanying Degradation of Cardiac Capillary Glycocalyx

Myocardial injury in sepsis may be caused by a burst of several inflammatory mediators, leading to vascular endothelial injuries. However, the contribution of neutrophil elastase (NE) to myocardial injury in sepsis is still unknown. We aimed to evaluate whether endotoxemia-induced myocardial injury is associated with NE. Lipopolysaccharide (LPS) was injected intraperitoneally at a dose of 20 mg/kg into granulocyte-colony-stimulating-factor knockout mice (G-CSF-KO), which have few neutrophils, and littermate control mice. The survival rate of G-CSF-KO mice 48 hours after LPS injection was significantly greater than that of control mice. The serum level of troponin I in G-CSF-KO mice was significantly lower than that in control mice. In addition, the concentration of inflammatory cytokine interleukin-6 (IL-6) was significantly decreased 6 and 12 hours after LPS administration compared with that in control mice. Ultrastructural analysis revealed that vascular endothelial structures and the endothelial glycocalyx in G-CSF-KO mice were clearly preserved. Next, mice were injected with 0.2 mg/kg sivelestat (an NE inhibitor) after LPS administration. The survival rate was significantly higher and the serum level of troponin I was lower in sivelestat-injected mice than in control mice, respectively. Furthermore, IL-6 levels were significantly decreased 6 and 12 hours after LPS administration compared with those in control mice. Vascular endothelial structures and the endothelial glycocalyx in sivelestat-treated mice were clearly preserved at the ultrastructural level. In conclusion, NE is significantly associated with myocardial injury in endotoxemia. Inhibition of NE may be a useful tool for the management of endotoxemia.

Monitoring Microcirculation: Utility and Barriers - A Point-of-View Review

Microcirculation is a particular organ of the cardiovascular system. The goal of this narrative review is a critical reappraisal of the present knowledge of microcirculation monitoring, mainly focused on the videomicroscopic evaluation of sublingual microcirculation in critically ill patients. We discuss the technological developments in handheld videomicroscopy, which have resulted in adequate tools for the bedside monitoring of microcirculation. By means of these techniques, a large body of evidence has been acquired about the role of microcirculation in the pathophysiological mechanisms of shock, especially septic shock. We review the characteristics of sublingual microcirculation in septic shock, which mainly consist in a decrease in the perfused vascular density secondary to a reduction in the proportion of perfused vessels along with a high heterogeneity in perfusion. Even in patients with high cardiac output, red blood cell velocity is decreased. Thus, hyperdynamic flow is absent in the septic microcirculation. We also discuss the dissociation between microcirculation and systemic hemodynamics, particularly after shock resuscitation, and the different behavior among microvascular beds. In addition, we briefly comment the effects of some treatments on microcirculation. Despite the fact that sublingual microcirculation arises as a valuable goal for the resuscitation in critically ill patients, significant barriers remain present for its clinical application. Most of them are related to difficulties in video acquisition and analysis. We comprehensively analyzed these shortcomings. Unfortunately, a simpler approach, such as the central venous minus arterial PCO₂ difference, is a misleading surrogate for sublingual microcirculation. As conclusion, the monitoring of sublingual microcirculation is an appealing method for monitoring critically ill patients. Nevertheless, the lack of controlled studies showing benefits in terms of outcome, as well as technical limitations for its clinical implementation, render this technique mainly as a research tool.

Starch or Saline After Cardiac Surgery: A Double-Blinded Randomized Controlled Trial

Background:

Despite decades of investigation, the balance of clinical risks and benefits of fluid supplementation with starch remain unresolved. Patient-centered outcomes have not been well explored in a “real-world” trial in cardiac surgery.

Objective:

We sought to compare a starch-based fluid strategy with a saline-based fluid strategy in the cardiac surgery patient.

Design:

A pragmatic blinded randomized controlled trial comparing starch-based with saline-based fluid strategy.

Setting:

A large tertiary academic center in London Ontario between September 2009 and February 2011.

Participants:

Patients undergoing planned, isolated coronary revascularization.

Measurements:

Serum creatinine and patient weight were measured daily postoperatively.

Methods:

Patients were randomized to receive 6% hydroxyethyl starch (Voluven) or saline for perioperative fluid requirements. Fluid administration was not protocolized. Co-primary outcomes were incidence of acute kidney injury (AKI) and maximum postoperative weight gain. Secondary outcomes included bleeding, transfusion, inotropic and ventilator support, and fluid utilization.

Results:

The study was prematurely terminated due to resource limitations. A total of 69 patients (19% female, mean age = 65) were randomized. Using RIFLE criteria for AKI, “risk” occurred in 12 patients in each group (risk ratio [RR] = 1.0; 95% confidence interval [CI] = 0.5-1.9; P = 1.00), whereas “injury” occurred in 7 of 35 (20%) and 3 of 34 (9%) of patients in the starch and saline groups, respectively (RR = 2.3; 95% CI = 0.6-8.1; P = .31). Maximum weight gain, bleeding and blood product usage, and overall fluid requirement were similar between groups.

Limitations:

The study had to be prematurely terminated due to resource limitations which led to a small sample size which was not sufficiently powered to detect a difference in the primary outcomes.

Conclusions:

This pragmatic double-blinded randomized controlled trial revealed a number of interesting hypothesis-generating trends and confirmed the feasibility of undertaking a logistically complex trial in a pragmatic fashion.

Sepsis-induced cardiac dysfunction and β-adrenergic blockade therapy for sepsis

Despite recent advances in medical care, mortality due to sepsis, defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, remains high. Fluid resuscitation and vasopressors are the first-line treatment for sepsis in order to optimize hemodynamic instability caused by vasodilation and increased vascular permeability. However, these therapies, aimed at maintaining blood pressure and blood flow to vital organs, could have deleterious cardiac effects, as cardiomyocyte damage occurs in the early stages of sepsis. Recent experimental and clinical studies have demonstrated that a number of factors contribute to sepsis-induced cardiac dysfunction and the degree of cardiac dysfunction is one of the major prognostic factors of sepsis. Therefore, strategies to prevent further cardiomyocyte damage could be of crucial importance in improving the outcome of sepsis. Among many factors causing sepsis-induced cardiac dysfunction, sympathetic nerve overstimulation, due to endogenous elevated catecholamine levels and exogenous catecholamine administration, is thought to play a major role. β-adrenergic blockade therapy is widely used for ischemic heart disease and chronic heart failure and in the prevention of cardiovascular events in high-risk perioperative patients undergoing major surgery. It has also been shown to restore cardiac function in experimental septic animal models. In a single-center randomized controlled trial, esmolol infusion in patients with septic shock with persistent tachycardia reduced the 28-day mortality. Furthermore, it is likely that β-adrenergic blockade therapy may result in further beneficial effects in patients with sepsis, such as the reduction of inflammatory cytokine production, suppression of hypermetabolic status, maintenance of glucose homeostasis, and improvement of coagulation disorders. Recent accumulating evidence suggests that β-adrenergic blockade could be an attractive therapy to improve the prognosis of sepsis. We await a large multicenter randomized clinical trial to confirm the beneficial effects of β-adrenergic blockade therapy in sepsis, of which mortality is still high.

THE USE OF HYDROXYETHYL STARCH 200/0,5 AS PLASMA SUBTITUTES IS SAFE IN HYPOVOLEMIC PATIENTS AS INDICATED IN CHANGES OF N-ACETYL--GLUCOSAMINIDASE AND CREATININ SERUM PARAMETERS

Hydroxyethyl Starch (HES) is a compound that improves intravascular volume effectively and rapidly without causing tissue edema. However, HES also has renal safety profile which is still being debated. Based on clinical experience in Dr. Soetomo Hospital, the frequency of acute renal failure following HES 200/0.5 administration at a dose of less than 20 ml/kg (maximum dose) is very rare. The purpose of this study was to evaluate the effect of HES 200/0.5 at a dose of less than 20 ml/kg in patients undergoing surgery. N-acetyl-b-D-Glucosaminidase (NAG) per urine creatinine ratio and creatinine serum were used as main parameter to assess renal injury. This research was observational and prospective design in patients undergoing elective surgery at Gedung Bedah Pusat Terpadu, Dr. Soetomo Hospital, who requiring resuscitation therapy with HES 200/0.5 and met the inclusion and exclusion criteria. NAG was measured prior to surgery and 12 hours after administration of fluid therapy, while creatinine serum was observed before surgery and 48 hours after resuscitation. This study was conducted for three months, and obtained 50 subjects divided into 2 groups, crystalloid group and HES 200/0.5 group. Demographic and baseline characteristics did not differ between groups, except the total bleeding volume. Total bleeding in HES 200/0.5group was higher than crystalloid group (p <0.0001). The mean volume of fluid received in HES 200/0.5 group was 2042.0 ± 673.9 mL, higher when compared with that of crystalloid group (910.0 ± 592.0 ml). Doses of HES 200/0.5 received was 8.31 ± 4.86 ml/kg. Measurement of the of NAG/creatinine ratio and creatinine serum showed significant increase in both groups, but still within the normal range. In addition, the value of these two parameters did not differ between groups. In conclusion, HES 200/0.5 in a dose of less than 20 ml/kg is safe to use in patients who suffered from hypovolemic hemorrhage, without prior history of renal impairment.

What is microcirculatory shock?

PURPOSE OF REVIEW

Microcirculatory shock is a condition defined by the presence of tissue hypoperfusion despite the normalization of systemic and regional blood flow. In this article, we discuss the characteristics of the microcirculation in septic shock, the main form of microcirculatory shock, along with its interaction with systemic hemodynamics, and the response to different therapies.

RECENT FINDINGS

In septic shock, microcirculatory abnormalities are common, and more severe in nonsurvivors. In addition, the microcirculation shows a behavior that is frequently dissociated from that of systemic hemodynamics. Therefore, microcirculatory alterations may persist despite correction of systemic hemodynamic variables. Sublingual and intestinal microcirculation might also display divergent behaviors. Moreover, microvascular alterations may improve in response to hemodynamic resuscitation, but the response might depend on the underlying microcirculatory alterations. Particularly, the response to fluids seems to be related to both its basal state and the magnitude of the increase in cardiac output.

SUMMARY

The optimal treatment of microcirculatory shock might require monitoring and therapeutic goals targeted on the microcirculation, more than in systemic variables. The clinical benefits of this approach should be demonstrated in clinical trials.

The physiologic perspective in fluid management in vascular anesthesiology

Vascular surgery patients frequently suffer from atherosclerosis and peripheral arterial occlusive disease generating endothelial dysfunction. Furthermore, ischemia and reperfusion during surgery damage endothelial cells and, especially, the endothelial glycocalix. The damage of the glycocalix promotes an increase in permeability. Not only crystalloids, which freely diffuse between the intravascular and the interstitial compartment, but also colloidal fluids cross from the intravascular space in the interstitial space with the consequence of edema formation. Possible tissue edema may result in an impairment of tissue oxygenation, leading to wound healing disturbances and initiation of inflammatory responses up to tissue apoptosis. Particularly in vascular anesthesia, this possibly means that colloids only should be administered in acute volume resuscitation immediately after unclamping a big vessel for immediate volume restoration. Which colloidal fluid should be administered is still under intense discussion. From a theoretical physiologic point of view, iso-osmolar albumin is the best choice regarding volume effect, antioxidative properties, and protection against destruction of the glycocalix. Nonetheless, albumin experimentally has not lived up to its promise in the clinical setting. Thus, further well-conducted large randomized clinical trials are necessary to ascertain the optimal fluid therapy in vascular surgery patients.

Lung ischemia-reperfusion injury: a molecular and clinical view on a complex pathophysiological process

Lung ischemia-reperfusion injury remains one of the major complications after cardiac bypass surgery and lung transplantation. Due to its dual blood supply system and the availability of oxygen from alveolar ventilation, the pathogenetic mechanisms of ischemia-reperfusion injury in the lungs are more complicated than in other organs, where loss of blood flow automatically leads to hypoxia. In this review, an extensive overview is given of the molecular and cellular mechanisms that are involved in the pathogenesis of lung ischemia-reperfusion injury and the possible therapeutic strategies to reduce or prevent it. In addition, the roles of neutrophils, alveolar macrophages, cytokines, and chemokines, as well as the alterations in the cell-death related pathways, are described in detail.

Fluids in septic shock: too much of a good thing?

In a recent issue of Critical Care, Brandt and colleagues report the effects of a 'liberal' fluid loading protocol compared to a more 'restrictive' protocol on hemodynamics and mortality in pigs in which septic shock had been induced. It appears that the former protocol was associated with higher mortality in spite of improved hemodynamics compared to the latter. The results of the paper are discussed here in view of the scope and mechanisms of these findings. With regard to fluid resuscitation, they indicate that too much of an otherwise good thing is harmful, even if overhydration and edema formation seem to have been prevented. They also do not exclude a specific toxic effect of the larger volumes of hydroxyethyl starch in the 'liberal' strategy. The precise nature of a toxic effect remains obscure, however, but may involve the kidneys.

Clinical strategies for supporting the untransfusable hemorrhaging patient

Hemorrhaging patients who cannot be transfused due to personal beliefs or the lack of compatible blood products provide a unique challenge for clinicians. Here we describe a 58-year-old African American man with a history of sickle cell-beta(+) thalassemia who had recently received a multiunit exchange transfusion and developed hematochezia followed by severe anemia. Due to the presence of multiple alloantibodies, no compatible packed red blood cell (pRBC) units could initially be located. The patient was managed with mechanical ventilation, colloid and crystalloid solutions, procoagulants, and recombinant erythropoietin. After an extensive search by our blood bank, enough compatible pRBC units were identified and the patient survived without significant clinical sequelae. Management of the untransfusable hemorrhaging patient requires a multidisciplined approach, with coordination between blood banks, hematologists, intensivists, and other specialists. Steps should be taken to avoid or limit blood loss, identify compatible pRBC units, control hypotension, maximize oxygen delivery, minimize metabolic demand, and stimulate erythropoiesis. In dire circumstances, use of experimental hemoglobin substitutes or transfusion of the least serologically incompatible pRBCs available may be considered.

Effects of a predominantly hydroxyethyl starch (HES)-based and a predominantly non HES-based fluid therapy on renal function in surgical ICU patients

PURPOSE

To compare the effects of predominantly hydroxyethyl starch (HES 6% 130/0.4)-based with predominantly gelatin 4%-based fluid therapy on renal function in surgical intensive care unit (ICU) patients.

METHODS

Before-after, retrospective, study of surgical ICU patients. All patients admitted from January to June 2005 formed the HES group, with HES 130/0.4 as the standard colloid of choice. All patients admitted from January to June 2006 formed the GEL group, with gelatin 4% as the primary colloid. Acute renal failure (ARF) was defined as new need for renal replacement therapy (RRT) or at least a two-fold increase in baseline creatinine.

RESULTS

There were 1383 patients in the HES group and 1528 in the GEL group; 118 and 87, in each group respectively, had severe sepsis. The incidence of ARF and ICU and hospital mortality rates were similar in the two groups. In a post-hoc multivariable analysis, cumulative doses >33 ml/kg of either HES (OR = 1.85, 95% CI: 1.01-3.41, p < 0.001) or gelatin (OR = 1.99, 95% CI: 1.05-3.79, p = 0.035) were associated with a higher risk of ARF.

CONCLUSIONS

The incidence of ARF was similar in patients who received predominantly HES (6% 130/.04) fluid therapy and in those who received predominantly gelatin 4%. Moderate cumulative doses of modern HES or gelatin solutions may be associated with a higher risk of ARF.

Combined therapy of pentastarch, dexamethasone, and dibutyryl-cAMP or beta 2-agonist attenuates ischaemia/reperfusion injury of rat lung

We hypothesised that combined therapy with macromolecules that seal endothelial damage [pentastarch (Penta)], an anti-inflammatory agent [dexamethasone (Dex)], and an agent that reabsorbs alveolar fluid [beta(2)-agonist or dibutyryl-cAMP (Bt(2)-cAMP)] would have additive ameliorating effects on ischaemia/reperfusion (I/R) injury of the lung. We perfused one of the following solutions into isolated rat lungs in a closed circulating system, either prior to I/R injury (groups 1-5) or following 60 min of ischaemia (groups 6-10): (1) 0.9% normal saline (NS), (2) Penta, (3) Penta+Dex, (4) Penta+Bt(2)-cAMP, (5) Penta+beta(2)-agonist inhalation, (6) Penta+Dex, (7) Penta+Bt(2)-cAMP, (8) Penta+beta(2)-agonist inhalation, (9) Penta+Dex+Bt(2)-cAMP, or (10) Penta+Dex+beta(2)-agonist inhalation. Haemodynamics, lung weight gain (LWG), capillary filtration coefficient (K(fc)), cytokine mRNA levels, and lung pathology were assessed. Results showed that Dex, Bt(2)-cAMP, or beta(2)-agonist as an additive to Penta decreased K(fc) and LWG below values seen with Penta alone. Furthermore, LWG and K(fc) values in groups with three protective agents were lower than those in groups with two protective agents. Significantly lower levels of TNF-alpha and IL-1 mRNAs were observed in groups treated with Dex. Histopathological studies showed decreased injury profiles for all combined therapy groups. We conclude that the addition of Dex, Bt(2)-cAMP, or beta(2)-adrenergic agonist to Penta solution promoted attenuation of I/R injury. Furthermore, combination therapy with three protective agents (Penta+Dex+beta(2)-adrenergic agonist) caused the greatest attenuation of I/R.

Intensive insulin therapy and pentastarch resuscitation in severe sepsis

BACKGROUND

The role of intensive insulin therapy in patients with severe sepsis is uncertain. Fluid resuscitation improves survival among patients with septic shock, but evidence is lacking to support the choice of either crystalloids or colloids.

METHODS

In a multicenter, two-by-two factorial trial, we randomly assigned patients with severe sepsis to receive either intensive insulin therapy to maintain euglycemia or conventional insulin therapy and either 10% pentastarch, a low-molecular-weight hydroxyethyl starch (HES 200/0.5), or modified Ringer's lactate for fluid resuscitation. The rate of death at 28 days and the mean score for organ failure were coprimary end points.

RESULTS

The trial was stopped early for safety reasons. Among 537 patients who could be evaluated, the mean morning blood glucose level was lower in the intensive-therapy group (112 mg per deciliter [6.2 mmol per liter]) than in the conventional-therapy group (151 mg per deciliter [8.4 mmol per liter], P<0.001). However, at 28 days, there was no significant difference between the two groups in the rate of death or the mean score for organ failure. The rate of severe hypoglycemia (glucose level, < or = 40 mg per deciliter [2.2 mmol per liter]) was higher in the intensive-therapy group than in the conventional-therapy group (17.0% vs. 4.1%, P<0.001), as was the rate of serious adverse events (10.9% vs. 5.2%, P=0.01). HES therapy was associated with higher rates of acute renal failure and renal-replacement therapy than was Ringer's lactate.

CONCLUSIONS

The use of intensive insulin therapy placed critically ill patients with sepsis at increased risk for serious adverse events related to hypoglycemia. As used in this study, HES was harmful, and its toxicity increased with accumulating doses. (ClinicalTrials.gov number, NCT00135473.)

Volume therapy with colloid solutions preserves intestinal microvascular perfusion in endotoxaemia

Colloid solutions have been suggested to improve microvascular perfusion due to their anti-inflammatory properties. Whether this also applies for the gut, an important immunological organ vulnerable to hypoperfusion is unknown. This study investigated intestinal microcirculation of endotoxaemic rats after volume therapy with colloid solutions such as hydroxyethyl starch (HES) and gelatin or isotonic saline (NaCl). In addition intestinal oxygenation and morphology as well as mesenteric leukocyte-endothelium interaction were quantified. Rats were anaesthetised with urethane and ketamine, mechanically ventilated, and monitored haemodynamically. Normotensive endotoxaemia was induced by a continuous intravenous infusion of Escherichia coli lipopolysaccharide (LPS, 1.5 mg kg(-1) h(-1)). After 1 h of LPS infusion either 6% HES (16 ml kg(-1)), 4% gelatin (16 ml kg(-1)) or 0.9% NaCl (64 ml kg(-1)) were infused for 1 h. Using intravital microscopy, functional capillary density (FCD) and red blood cell velocity (RBCV) were measured in the mucosa of the terminal ileum at baseline and 3 h after volume therapy. In another set of animals, mesenteric leukocyte-endothelium interaction was determined 3 h after volume therapy. In all animals intestinal lactate/pyruvate ratio and intestinal morphology were assessed. Three hours after volume therapy, FCD decreased in NaCl (808 [749/843] cm(-1); median [quartiles] P<0.05 versus baseline) but not in HES (995 [945/1036] cm(-1)) and gelatin (988 [867/1193] cm(-1)) groups. RBCV, lactate/pyruvate ratio and intestinal morphology did not differ among groups. Also mesenteric leukocyte-endothelium interaction was not significantly influenced by either treatment. In conclusion, early volume therapy with HES or gelatin, but not with NaCl, preserved gut microvascular perfusion during endotoxaemia but did not have a significant effect on tissue oxygenation nor morphological appearance in this experimental model. An anti-inflammatory effect of colloid solutions was not seen and fails to explain the changes in intestinal microcirculation.

Attenuation of capillary leakage by hydroxyethyl starch (130/0.42) in a porcine model of septic shock

OBJECTIVES

Capillary leakage, a frequent complication in septic shock, is characterized by loss of intravasal fluid resulting in generalized edema and hemodynamic instability despite massive fluid therapy. We have shown that administration of an established colloid 200/0.5 hydroxyethyl starch (HES) stabilized plasma volume in a porcine septic shock model. Recently, a new HES with a low molecular weight (130 kD) and lower molar substitution (0.42) has been developed. In this study, we compared effects of HES 130/0.42 and HES 200/0.5 on capillary leakage in porcine septic shock.

DESIGN

Prospective randomized, controlled animal study.

SETTING

University department of anesthesiology.

SUBJECTS

Fourteen pigs (22.9 +/- 2.8 kg).

INTERVENTIONS

Anesthetized and mechanically ventilated pigs were observed over 6 hrs.

MEASUREMENT AND MAIN RESULTS

Septic shock was induced with fecal peritonitis (0.75 g.kg of body weight autologous feces). Animals were allocated to volume-replacement therapy with either HES 130/0.42 (n = 5) or HES 200/0.5 (n = 5) and compared with nonseptic controls receiving HES 130/0.42 (n = 4). Infusion rate was titrated to maintain a central venous pressure of 12 mm Hg. Albumin escape rate was calculated using iodine 125-labeled albumin. Plasma volume was determined using chromium-51-tagged erythrocytes. Albumin escape rate increased significantly in both groups in comparison to controls (HES 200/0.5, 45% +/- 3; HES 130/0.42, 38% +/- 5), but this increase was significantly smaller with HES 130/0.42. Both HES 200/0.5 (-14%, not significant) and HES 130/0.42 (-1%, not significant) stabilized plasma volume compared with controls. Systemic oxygenation was not significantly altered in either group.

CONCLUSIONS

In this porcine septic shock model, HES 130/0.42 attenuated capillary leakage significantly more effectively than HES 200/0.5.

Comparison of lactated Ringer's, gelatine and blood resuscitation on intestinal oxygen supply and mucosal tissue oxygen tension in haemorrhagic shock

OBJECTIVES

To evaluate the effects on intestinal oxygen supply, and mucosal tissue oxygen tension during haemorrhage and after fluid resuscitation with either blood (B; n=7), gelatine (G; n=8), or lactated Ringer's solution (R; n=8) in an autoperfused, innervated jejunal segment in anaesthetized pigs.

METHODS

To induce haemorrhagic shock, 50% of calculated blood volume was withdrawn. Systemic haemodynamics, mesenteric venous and systemic acid-base and blood gas variables, and lactate measurements were recorded. A flowmeter was used for measuring mesenteric arterial blood flow. Mucosal tissue oxygen tension (PO(2)muc), jejunal microvascular haemoglobin oxygen saturation (HbO(2)) and microvascular blood flow were measured. Measurements were performed at baseline, after haemorrhage and at four 20 min intervals after fluid resuscitation. After haemorrhage, animals were retransfused with blood, gelatine or lactated Ringer's solution until baseline pulmonary capillary wedge pressure was reached.

RESULTS

After resuscitation, no significant differences in macrohaemodynamic parameters were observed between groups. Systemic and intestinal lactate concentration was significantly increased in animals receiving lactated Ringer's solution [5.6 (1.1) vs 3.3 (1.1) mmol litre(-1); 5.6 (1.1) vs 3.3 (1.2) mmol litre(-1)]. Oxygen supply to the intestine was impaired in animals receiving lactated Ringer's solution when compared with animals receiving blood. Blood and gelatine resuscitation resulted in higher HbO(2) than with lactated Ringer's resuscitation after haemorrhagic shock [B, 43.8 (10.4)%; G, 34.6 (9.4)%; R, 28.0 (9.3)%]. PO(2)muc was better preserved with gelatine resuscitation when compared with lactated Ringer's or blood resuscitation [20.0 (8.8) vs 13.8 (7.1) mm Hg, 15.2 (7.2) mm Hg, respectively].

CONCLUSION

Blood or gelatine infusion improves mucosal tissue oxygenation of the porcine jejunum after severe haemorrhage when compared with lactated Ringer's solution.

DO PLASMA SUBSTITUTES HAVE ADDITIONAL PROPERTIES BEYOND CORRECTING VOLUME DEFICITS?

The best strategy for volume therapy has been the focus of debate and there are still no unique accepted guidelines. There is increasing evidence that some plasma substitutes possess additional effects on organ perfusion, microcirculation, tissue oxygenation, inflammation, endothelial activation, capillary leakage, and tissue edema that are beyond their volume replacing properties. Whether the different plasma substitutes differ with regard this additional effects was reviewed. The additional effects of plasma substitutes have mostly been studied experimentally or in animals, much less results are available in humans. The results are not uniform ranging from beneficial to even detrimental effects of a certain volume replacement strategy. Some important results from the literature are not reflected in the actual recommendations for treating volume deficits in the critically ill: although crystalloids have been shown to have considerable negative effects on microcirculation, organ perfusion, tissue oxygenation, and endothelial integrity, they are still often recommended as first choice volume replacement strategy. In several experimental studies hypertonic solutions have been shown to have various beneficial effects, they have not been, however, translated into humans. In future, the choice of the ideal volume replacement regimen should not only be focused on its volume restoring properties, but additional effects (e.g. on organ perfusion on, tissue oxygenation, inflammation, endothelial activation, capillary leakage) should also be taken into account when treating hypovolemia in the critically ill.

Microvascular effects following treatment with polyethylene glycol-albumin in lipopolysaccharide-induced endotoxemia

OBJECTIVE

To determine whether resuscitation with polyethylene glycol conjugated bovine serum albumin (2.5% weight/volume) infused at 16 mL/kg/hr (PEG-BSA-16) or at 24 mL/kg/hr (PEG-BSA-24) for 1 hr improves microcirculatory conditions in endotoxemia compared with dextran 70 (6% weight/volume) infused at 24 mL/kg/hr (Dex).

DESIGN

Prospective study.

SETTING

University research laboratory.

SUBJECTS

Male Golden Syrian hamsters.

INTERVENTIONS

Hamsters implemented with a skinfold window chamber were given an intravenous injection of lipopolysaccharide and resuscitated within 10 mins with Dex, PEG-BSA-16, or PEG-BSA-24.

MEASUREMENTS AND MAIN RESULTS

Hamsters were observed during 24 hrs after lipopolysaccharide injection. Systemic variables measured included mean arterial pressure, heart rate, and systemic arterial blood gas. Microvascular function was characterized by measuring vessel diameter; red blood cell velocity; functional capillary density (FCD); P(O2) in arterioles, venules, and tissue; and perivascular nitric oxide concentration 6 hrs after lipopolysaccharide injection. At 6 hrs, animals with no treatment had the lowest FCD (6.7 +/- 5.7% of baseline). PEG-BSA provided significantly improved microvascular conditions as shown by restoration of FCD. Recovery of FCD was related to improved microvascular flow and perivascular and tissue P(O2), normalization of shear rate, and decreased perivascular nitric oxide concentration. These effects were related to improved fluid retention using PEG-BSA-24 as evidenced by the significantly lower hematocrit at 24 hrs after resuscitation. Nitric oxide at 6 hrs after induction of sepsis achieved perivascular millimolar concentrations, which were reduced to normal values by PEG-BSA-24 treatment. At 6 hrs there were significant differences in FCD, tissue P(O2), and perivascular nitric oxide concentration following PEG-BSA treatment by comparison with Dex treatment, although there were no differences in systemic variables between Dex and PEG-BSA groups.

CONCLUSIONS

PEG-BSA produces improved microcirculatory conditions in the treatment of endotoxemia when compared with dextran 70.

Infusion of the β-adrenergic blocker esmolol attenuates myocardial dysfunction in septic rats*

OBJECTIVE

Since beta-blocker therapy is known to be effective in patients with an injured heart, such as infarction, we designed the present study to examine the protective effects of infusion of the beta1-selective blocker esmolol on myocardial function in peritonitis-induced septic rats using an isolated working heart preparation.

DESIGN

Randomized animal study.

SETTING

University research laboratory.

SUBJECTS

Thirty-one rats treated with cecal ligation and perforation to evoke peritonitis.

INTERVENTIONS

After cecal ligation and perforation, rats were randomly allocated to the control group (normal saline 2 mL/hr, n = 11), low-dose esmolol group (10 mg/kg/hr, n = 10), or high-dose esmolol group (20 mg/kg/hr, n = 10). After obtaining blood samples for measurement of arterial lactate and tumor necrosis factor-alpha at 24 hrs, we assessed cardiac output, myocardial oxygen consumption, and cardiac efficiency (cardiac output x peak systolic pressure/myocardial oxygen consumption) at various preloads in an isolated perfused heart preparation.

MEASUREMENTS AND MAIN RESULTS

Esmolol infusion did not cause an elevation of arterial lactate levels but reduced tumor necrosis factor-alpha concentrations vs. the control group (p < .05). Both cardiac output and cardiac efficiency in the esmolol-treated rats were significantly higher throughout the study periods vs. the control group (p < .05).

CONCLUSIONS

Esmolol infusion in sepsis improved oxygen utilization of myocardium and preserved myocardial function.

Anesthesia of the critically ill equine patient

There is a plethora of information regarding anesthetic management of horses; however, controlled studies of the critically ill equine patient are few. These patients should be managed like any equine anesthetic candidate but much more stringently:I. Preoperative evaluation and appropriate therapy may represent the difference between life and death during the intraoperative and recovery periods. 2. The anesthetic induction and maintenance protocol should be based on the individual situation of the veterinary facility and personnel("comfort zone"). 3. Appropriate monitoring and intraoperative supportive measures are essential. 4. The anesthetic period is a significant perturbation to homeostasis. Even if the horse seems to have done well (ie, as indicated by the cardiopulmonary values), a problem-free anesthetic period does not guarantee a successful recovery, and close monitoring should continue until the horse is ambulatory. 5. Critically ill patients are often in a negative energy balance. Supportive measures to ensure an adequate caloric intake, such as enteral or parenteral nutrition, facilitate healing and return of homeostasis.

Tissue oxygen delivery and the microcirculation

In health, acute anemia is accompanied by changes in the distribution of blood flows at all of the central, regional, and microcirculatory levels. This redistribution in blood flows provides the capacity to maintain tissue oxygenation with hematocrit as low as 21%. What is not known with certainty is whether the capacity to maintain tissue oxygenation in the presence of acute anemia can be influenced significantly by concurrent disease such as sepsis and cardiac disease. The single clinical trial found an apparent survival benefit by not exposing patients with sepsis to blood transfusions until the hemoglobin concentration was less than 70 g/L. The question remains as to whether this observation was the consequence of a protective effect anemia or an injurious effect of transfusing old stored blood.

Practice parameters for hemodynamic support of sepsis in adult patients: 2004 update

OBJECTIVE

To provide the American College of Critical Care Medicine with updated guidelines for hemodynamic support of adult patients with sepsis.

DATA SOURCE

Publications relevant to hemodynamic support of septic patients were obtained from the medical literature, supplemented by the expertise and experience of members of an international task force convened from the membership of the Society of Critical Care Medicine.

STUDY SELECTION

Both human studies and relevant animal studies were considered.

DATA SYNTHESIS

The experts articles reviewed the literature and classified the strength of evidence of human studies according to study design and scientific value. Recommendations were drafted and graded levels based on an evidence-based rating system described in the text. The recommendations were debated, and the task force chairman modified the document until <10% of the experts disagreed with the recommendations.

CONCLUSIONS

An organized approach to the hemodynamic support of sepsis was formulated. The fundamental principle is that clinicians using hemodynamic therapies should define specific goals and end points, titrate therapies to those end points, and evaluate the results of their interventions on an ongoing basis by monitoring a combination of variables of global and regional perfusion. Using this approach, specific recommendations for fluid resuscitation, vasopressor therapy, and inotropic therapy of septic in adult patients were promulgated.

Fluid choice for resuscitation of the trauma patient: a review of the physiological, pharmacological, and clinical evidence

PURPOSE

Volume replacement regimens are discussed very emotionally. Interpretation of the literature is difficult due to variations in study design, patient population, target for volume replacement, endpoints, and type of fluids. Meta-analyses may not be very helpful because all kinds of patients and very old studies are included. The principles and options for volume replacement were reviewed exclusively in trauma patients and studies from the literature focusing on this problem were analyzed.

SOURCE

Using a MEDLINE search, volume replacement therapy in adult trauma patients published in the English language from 1985 to the end of 2002 were identified and analyzed. Studies on prehospital volume replacement, volume replacement in the emergency area or in the operating room, and volume therapy in trauma intensive care unit patients were included.

PRINCIPLE FINDINGS

The age-old crystalloid/colloid controvery has still not been resolved but has been enlarged to a colloid/colloid debate. It is now widely accepted that human albumin could easily be replaced by synthetic colloids for volume replacement in trauma patients. No superiority of a specific volume replacement strategy with regard to outcome was found. However, in several studies outcome was not the major endpoint. Although showing some promising results, the importance of hypertonic solutions for volume replacement in the trauma patient is not yet defined.

CONCLUSION

The choice of fluid therapy in trauma patients engenders the most controversy and an examination of the body of literature on this subject results in confusion. It is imperative to continue the search for substances that are effective in avoiding the development of post-trauma multi-organ dysfunction syndrome without detrimental side-effects.

Fluid therapy in horses with gastrointestinal disease

Fluid therapy is essential to the successful management of horses with gastrointestinal disease. Affected horses can present in a wide spectrum of metabolic derangement depending on the extent and severity of the underlying disease process. Precise quantitation of fluid deficits and losses is usually not possible; thus, formulating a rational plan, applying diligent and ongoing monitoring, and making adjustments to meet individual demands provide the best approach to fluid therapy in these horses. Although restoration of fluid and electrolyte homeostasis can be complicated, it is probably best in most cases to keep the approach as simple as possible and resist the urge to "over" manage.

Influence of different volume replacement strategies on inflammation and endothelial activation in the elderly undergoing major abdominal surgery

OBJECTIVE

Adequate restoration of intravascular volume remains an important maneuver in the management of the surgical patient. Influence of different volume replacement regimens on inflammation/endothelial activation in elderly surgical patients was assessed.

DESIGN

Prospective, randomized study.

SETTING

Surgical intensive care unit of a university-affiliated hospital.

PATIENTS

Sixty-six patients >65 years undergoing major abdominal surgery.

INTERVENTIONS

Ringer's lactate (RL; n=22), normal saline solution (NS; n=22) or a low-molecular HES (mean molecular weight 130 kD) with a low degree of substitution (0.4; HES 130/0.4; n=22) were administered after induction of anesthesia until the 1st postoperative day (POD) to keep central venous pressure between 8-12 mmHg.

MEASUREMENTS AND RESULTS

C-reactive protein, interleukins (IL-6, IL-8), adhesion molecules [endothelial leukocyte adhesion molecule-1 (ELAM-1) and intercellular adhesion molecule-1 (ICAM-1)] were measured prior to volume therapy at the end of surgery, 5 h after surgery and at the morning of the 1st POD. RL patients received 10,150+/-1,660 ml of RL, NS patients 10,220+/-1,770 ml of NS and the HES-treated group 2,850+/-300 ml of HES 130/0.4 and 2,810+/-350 ml of RL. Hemodynamics were similar in all groups. CRP, IL-6 and IL-8 plasma levels increased significantly higher in both crystalloid groups (IL-6 in the NS group: increase to 407+/-33 pg/ml; RL: increase to 377+/-35 pg/dl) than in the HES-130 treated group (IL-6: increase to 197+/-20 pg/dl). Plasma levels of ELAM-1 and ICAM remained almost unchanged in the HES 130-, but significantly increased in the RL- and NS-treated patients.

CONCLUSIONS

In elderly patients, markers of inflammation and endothelial injury and activation were significantly higher after crystalloid- than after HES 130/0.4-based volume replacement regimens.

Fluid therapy in sepsis with capillary leakage

Sepsis is associated with a profound intravascular fluid deficit due to vasodilatation, venous pooling and capillary leakage. Fluid therapy is aimed at restoration of intravascular volume status, haemodynamic stability and organ perfusion. Circulatory stability following fluid resuscitation is usually achieved in the septic patient at the expense of tissue oedema formation that may significantly influence vital organ function. The type of fluid therapy, crystalloid or colloid, in sepsis with capillary leakage remains an area of intensive and controversial discussion. The current understanding of the physiology of increased microvascular permeability in health and sepsis is incomplete. Furthermore, there is a lack of appropriate clinical study end-points for fluid resuscitation. This review considers critically the clinical and experimental data analysing the assessment of capillary leakage in sepsis and investigating the effects of different fluid types on increased microvascular permeability in sepsis.

Septic shock, multiple organ failure, and acute respiratory distress syndrome

In 1914, Schottmueller wrote "Septicemia is a state of microbial invasion from a portal of entry into the blood stream which causes signs of illness." In the last few decades, the evidence that sepsis results from an exaggerated systemic inflammatory host response induced by infecting organisms is compelling; inflammatory mediators are the key players in the pathogenesis of septic shock and multiorgan failure. Sepsis and its sequelae represent a continuum of clinical syndrome encompassing systemic inflammation, coagulopathy, and hemodynamic abnormalities. Severe sepsis and septic shock continue to be the major causes of morbidity and mortality in the United States; sepsis deaths currently match mortality from myocardial infarction. Despite significant advances in our understanding of the pathophysiology and technological innovations in the supportive management, mortality from septic shock remains excessive. After many disappointments with strategies to manipulate the inflammatory response, modulation of coagulation cascade to decrease sepsis mortality has become a clinical reality. This review will highlight and discuss recent advances in the pathophysiology and management of sepsis.

Intraoperative colloid administration reduces postoperative nausea and vomiting and improves postoperative outcomes compared with crystalloid administration

The debate over colloid versus crystalloid as the best solution for intraoperative fluid resuscitation is not resolved. Published studies have shown that mortality is not related to the specific fluid used for resuscitation. In addition, the quality of postoperative recovery between colloid and crystalloid has not been well investigated. In a prospective, blinded fashion, we investigated the effects of colloid and crystalloid resuscitation on nausea and vomiting and on the postoperative patient recovery profile. Patients undergoing major elective noncardiac surgery were randomized to receive 6% hetastarch in saline (HS-NS), 6% hetastarch in balanced salt (HS-BS), or lactated Ringer's solution (LR) on the basis of a fluid administration algorithm. The anesthetic was standardized. Hemodynamic targets included maintenance of arterial blood pressure, heart rate, and urine output within a predefined range. A postoperative morbidity survey was performed at baseline and daily after surgery. Ninety patients participated in the study, with 30 patients in each group. The amounts of study fluid (mean +/- SD) administered were 1301 +/- 1079 mL, 1448 +/- 759 mL, and 5946 +/- 1909 mL for the HS-NS, HS-BS, and LR groups, respectively (P < 0.05, HS-NS and HS-BS versus LR). Both the HS-NS and HS-BS (colloid) groups had a significantly less frequent incidence of nausea and vomiting, use of rescue antiemetics, severe pain, periorbital edema, and double vision. We concluded that intraoperative fluid resuscitation with colloid, when compared with crystalloid administration, is associated with an improvement in the quality of postoperative recovery.

Albumin resuscitation increases cardiomyocyte contractility and decreases nitric oxide synthase II expression in rat endotoxemia

OBJECTIVE

Hypotension and hypoperfusion during septic shock may contribute to tissue hypoxia and the intramyocardial inflammatory response that results in myocardial dysfunction. Therefore, we hypothesized that crystalloid or colloid resuscitation may alter myocardial dysfunction.

DESIGN

Randomized, controlled, prospective animal study.

SETTING

University animal laboratory.

SUBJECTS

Sprague-Dawley rats (250-300 g, n = 6/group).

INTERVENTIONS

Rats received an intraperitoneal injection of 10 mg/kg lipopolysaccharide or control. One hour later, rats were randomized to intravenous resuscitation and received either 30 mL/kg normal saline, 10 mL/kg 10% pentastarch, 10 mL/kg 5% rat albumin, or no volume.

MEASUREMENTS AND MAIN RESULTS

We measured fractional shortening of cardiomyocytes isolated 5 hrs after lipopolysaccharide or control injection. In separate identical experiments, we measured myocardial interleukin-6, macrophage inhibitory protein-2, and nitric oxide synthase II protein and messenger RNA expression. Control fractional shortening of 24.1 +/- 2.2% was decreased by lipopolysaccharide to 18.8 +/- 1.2% (p <.001). Volume resuscitation after lipopolysaccharide significantly improved fractional shortening (p <.001). In particular, albumin resuscitation increased fractional shortening to 23.5 +/- 0.9%, which was more than either saline (fractional shortening 20.1 +/- 1.7%,p <.01) or pentastarch (fractional shortening 21.4 +/- 0.9%,p <.01). Myocardial macrophage inhibitory protein-2 protein and interleukin-6 and macrophage inhibitory protein-2 messenger RNA expression and neutrophil content were elevated following lipopolysaccharide (p <.05) but were not altered by volume resuscitation. Myocardial nitric oxide synthase II protein and messenger RNA expression increased following lipopolysaccharide (p <.01) and decreased with albumin resuscitation.

CONCLUSIONS

We conclude that following lipopolysaccharide injection, volume resuscitation improves cardiomyocyte fractional shortening. Albumin resuscitation is particularly beneficial in preventing reduced cardiomyocyte contractility, and this benefit may be related to an albumin-induced reduction in nitric oxide synthase II protein and messenger RNA expression following endotoxin injection.

Sevoflurane preconditions stunned myocardium in septic but not healthy isolated rat hearts

BACKGROUND

Recent evidence indicates that sevoflurane treatment before prolonged ischaemia reduces infarct size in normal hearts, mimicking ischaemic preconditioning. We examined whether exposure to sevoflurane before brief ischaemia, inducing a 'stunned myocardium', provided such protective effects in an isolated working heart from normal or septic rats.

METHODS

With institutional approval, 91 rats were randomly allocated into one of either caecal-ligation and perforation (CLP: n=50) or sham (Sham: n=41) procedure groups 24 h before the study. After determination of baseline measurements, including cardiac output (CO), myocardial oxygen consumption (mVO(2)) and cardiac efficiency (CE; CO x peak systolic pressure/mVO(2)), each isolated heart was perfused with or without 2% sevoflurane for 15 min before global ischaemia (pre-ischaemia). After 15 min ischaemia and 30 min reperfusion, all hearts were assessed for functional recovery of myocardium (post-reperfusion).

RESULTS

During the pre-ischaemia period, 2% sevoflurane caused a significant reduction of CO in the CLP group compared with the Sham group. During the post-reperfusion period, both CO (16.9 vs 11.0 ml min(-1)) and CE (11.2 vs 7.7 mm Hg ml(-1) ( micro l O(2))(-1)) was higher in the sevoflurane-treated vs -untreated hearts from CLP rats, and was accompanied by lower incidence of reperfusion arrhythmia compared with control hearts (8 vs 32%). In contrast, 2% sevoflurane did not provide cardioprotective effects in normal rats.

CONCLUSIONS

The current study demonstrates that pre-treatment with sevoflurane minimizes myocardial dysfunction and the incidence of reperfusion arrhythmia after brief ischaemic insults in septic hearts.

Management of septic shock

Severe sepsis is a common disease process affecting some 2-11% of hospital admissions in the US. Severe sepsis and septic shock are associated with considerable morbidity and mortality, and account for a large part of intensive care unit costs. Until recently, the management of septic shock relied on the treatment of underlying infection with antimicrobial agents and surgical removal of any infectious source, and individual support of failing organs. However, in the last few years we have seen huge strides being made in our understanding of the pathophysiology of the sepsis response, and in our ability to manipulate that response. In the last couple of years these advances have come to fruition with the development of a drug, drotrecogin alfa, which specifically reduces mortality from this all too often fatal disease. While intensive early resuscitation remains the cornerstone of management, new approaches are beginning to form part of sepsis management protocols and will lead to improved outcomes for patients with this disease process.

Effect of hydroxyethyl starch infusion on colloid oncotic pressure in hypoproteinemic horses

OBJECTIVE

To determine the effect of hydroxyethyl starch (HES) on colloid oncotic pressure (pi) during fluid resuscitation of hypoproteinemic horses and to evaluate the clinical usefulness of direct and indirect methods for determination of pi before and after infusion of a synthetic colloid.

DESIGN

Prospective clinical study.

ANIMALS

11 hypoproteinemic horses.

PROCEDURE

Horses received IV infusions of 8 to 10 ml of a 6% solution of HES/kg (3.6 to 4.5 ml/lb) of body weight during fluid resuscitation. Blood samples were obtained for determination of plasma measured colloid oncotic pressure (pi meas) and plasma total protein and albumin (A) concentrations. Plasma globulin concentration (G) was calculated as the difference between plasma total protein and albumin concentrations. Calculated values for colloid oncotic pressure (piA + G) were determined by use of a predictive nomogram previously developed for horses.

RESULTS

There was no significant difference between the means of pi meas and piA + G at the beginning of HES infusion. After HES infusion, the mean of pi meas was increased significantly from baseline for 6 hours. Mean plasma total protein and albumin concentrations and piA + G were decreased significantly from baseline for 24 hours. Differences between mean pi meas and piA + G after HES infusion were significant for 24 hours.

CONCLUSIONS AND CLINICAL RELEVANCE

There was good agreement between plasma pi meas and piA + G in blood samples obtained from hypoproteinemic horses immediately before infusion of HES. Use of a predictive nomogram did not, however, account for the oncotic effect of HES. Results of comparison of pi meas to piA + G after HES infusion suggest that a significant oncotic effect was maintained for 24 hours in the study horses.

Role of endotoxin in the expression of endothelial selectins after cecal ligation and perforation

The objectives of this study were to determine 1) the changes in endothelial cell adhesion molecule expression that occur in a clinically relevant model of sepsis and 2) the dependence of these changes on endotoxin [lipopolysaccharide (LPS)]. The dual radiolabeled monoclonal antibody technique was used to quantify the expression of E- and P-selectin in LPS-sensitive (C3HeB/FeJ) and LPS-insensitive (C3H/HeJ) mice that were subjected to acute peritonitis by cecal ligation and perforation (CLP). At 6 h after CLP, the expression of both E- and P-selectin was increased in the gut (mesentery, pancreas, and small and large bowel) compared with the sham-operated and/or control animals, with a more marked response noted in LPS-insensitive mice. The lung also exhibited an increased P-selectin expression in both mouse strains. An accumulation of granulocytes, assessed using tissue myeloperoxidase activity, was noted in the lung and intestine of LPS-sensitive but not LPS-insensitive mice exposed to CLP. These results indicate that the CLP model of sepsis is associated with an upregulation of endothelial selectins in the gut vasculature and that enteric LPS does not contribute to this endothelial cell activation response.

Lung lymph response to overinfusion with hydroxyethyl starch in sheep. Comparative studies of high and low molecular weight compounds

BACKGROUND

Several hydroxyethyl starch (HES) solutions are available clinically. We performed comparative studies of low and high molecular weight HES to evaluate the effects on lung lymph flow in sheep, to see the difference in the types of HES.

METHODS

We prepared awake sheep with vascular monitorings and lung lymph fistulas. We measured systemic artery pressure (Psa), pulmonary artery pressure (Ppa), and left atrial pressure (Pla) continuously. Cardiac output (CO) was measured every 30 min. Lung lymph flow (Qlym) was collected every 15 min. After baseline measurements, two HES solutions were infused over 2 h, respectively. Experiment 1 (n=6): low molecular weight HES (MW 70 000, substitution ratio 0.5-0.55), Experiment 2 (n=5): high molecular weight HES (MW 450 000, substitution ratio 0.7).

RESULTS

Both low and high molecular HES behaved similarly as a volume expander, increasing Psa, CO, Pla and Ppa, and decreasing hematocrit. In addition, the actual oncotic pressure gradient (plasma - lymph) was widened after the start of either low or high molecular HES, but the value for high molecular HES was significantly higher than that for low molecular HES. Qlym of low molecular HES rose significantly from the baseline and the percent increase in Qlym for low molecular HES was significantly higher than that for high molecular HES.

CONCLUSION

These data suggest that low molecular HES is as useful a plasma substitute as high molecular HES, but may increase lung fluid filtration in the overinfused state.

An alternative pathway for preclinical research in fluid management

Recent meta-analyses have created uncertainties regarding the appropriate clinical role of colloid resuscitation fluids in critically ill patients and prompted changes in fluid management practice. Such changes may not be justified in view of methodological limitations inherent in the meta-analyses. Further research is nevertheless needed to resolve the questions raised concerning the relationship between choice of resuscitation fluid and patient outcome. Animal studies can play an important part by reliably indicating whether particular fluids are likely to prove effective and safe in clinical trials. It is important to avoid costly large-scale clinical trials that fail to demonstrate the clinical utility of the tested therapy, as resources expended in failed trials raise overall development costs and thereby restrict the range of therapies meeting criteria of commercial feasibility. Promising therapies may thus not be pursued, even though an urgent clinical need may exist. An alternative pathway of preclinical research may be of value in avoiding some of the major clinical trial failures of recent years, particularly in the area of sepsis. This alternative pathway commences with the formulation of hypotheses by therapeutics developers. Independent preclinical investigators are challenged, by means of a competitive request for proposals, to test the hypotheses in rigorous randomized studies employing clinically relevant animal models. Promising proposals would then be selected for further development with the aid of peer review. The results of the randomized animal studies, along with other preclinical data, could also be evaluated using accepted principles of 'critical appraisal' commonly applied to clinical trial results. This critical appraisal might, where appropriate, include meta-analysis of animal study findings. This alternative preclinical pathway to new product evaluation should be completed before the commencement of large-scale clinical trials.

Effects of modest anemia on systemic and coronary circulation of septic sheep

Although a lower transfusion trigger is generally recommended, little evidence is available about the physiological mechanisms of mild anemia in diseases with an imbalance between O2 supply and O2 demand such as sepsis. This study was undertaken to describe the systemic and coronary metabolic O2 reserve in an awake sheep model of hyperdynamic sepsis comparing two different hemoglobin levels. Twenty-four hours after sheep were rendered septic by cecal ligation and perforation (CLP), blood transfusion (n = 7, hemoglobin = 120 g/l) and isovolemic hemodilution (n = 8, hemoglobin = 70 g/l), respectively, were performed. Another 24 h later, we measured hemodynamics, organ blood flows, and systemic and myocardial O2 metabolism variables at baseline and through four stages of progressive hypoxia. Maximum coronary blood flow was 766.3 +/- 87.4 ml. min(-1). 100 g(-1) in hemodiluted sheep group versus 422.7 +/- 53.7 ml. min(-1). 100 g(-1) in the transfused sheep (P < 0.01). Myocardial O2 extraction was higher in the transfusion group (P = 0.03) throughout the whole hypoxia trial. In the hemodilution group, coronary blood flow increased more per increase in myocardial O(2) uptake than in transfused sheep (P < 0.01). This was accompanied by a lower left ventricular epicardial-to-endocardial flow ratio in hemodiluted sheep (1.13 +/- 0.07) than in transfused sheep (1.34 +/- 0.02, P < 0.05). We conclude that the lower coronary blood flow and greater myocardial O2 extraction in transfused septic sheep preserves transmyocardial O2 metabolism better in comparison to hemodiluted sheep.

Practice parameters for hemodynamic support of sepsis in adult patients in sepsis. Task Force of the American College of Critical Care Medicine, Society of Critical Care Medicine

OBJECTIVE

To present guidelines for hemodynamic support of adult patients with sepsis.

PARTICIPANTS

An international task force of nine experts in disciplines related to critical care medicine was convened from the membership of the Society of Critical Care Medicine.

EVIDENCE

Review of published literature and expertise and personal experience of task force. The strength of evidence of human studies was classified according to study design and scientific value.

CONSENSUS PROCESS

The task force met several times in person and communicated by electronic mail to identify the pertinent literature and arrive at consensus recommendations. Consideration was given to the relationship between the weight of scientific evidence and the experts'opinions. Draft documents were composed and debated by the task force until consensus was reached. The strength of recommendations was graded according to evidenced-based guidelines.

CONCLUSIONS

The panel formulated an underlying approach to the hemodynamic support of sepsis. Hemodynamic therapies should be titrated to specific and definable endpoints. The effects of therapy should be assessed by monitoring a combination of parameters of global and regional perfusion. Using this approach, the panel made specific recommendations for fluid resuscitation, vasopressor therapy, and inotropic therapy of septic patients.