Extracorporeal techniques of endotoxin removal: a review of the art and science

Effect of polymyxin B-immobilized fiber hemoperfusion on respiratory impairment, hepatocellular dysfunction, and leucopenia in a neonatal sepsis model

PURPOSE

Sepsis and septic shock remain a major source of morbidity and mortality in neonates despite advances in antimicrobials and aggressive supportive care. Our aim was to study the effects of polymyxin-B direct hemoperfusion (PMX-DHP) therapy on sepsis-induced respiratory impairment, liver dysfunction and leucopenia in a neonatal cecal ligation and perforation (CLP) model.

METHODS

Fourteen anesthetized and mechanically ventilated 3-day-old piglets underwent CLP and an arteriovenous extracorporeal circuit from 3 h until 6 h post-CLP, with a PMX column in the PMX-DHP treated group (7 piglets). Changes in oxygen saturation, PCO(2), base excess, white blood cell (WBC) count, platelet count, hematocrit (Hct%), serum glutamate pyruvate transaminase (SGPT), and serum glutamic oxaloacetic transaminase were measured before CLP and at 1, 3 and 6 h after.

RESULTS

At 6 h, the PMX-DHP group showed lower Hct%, and SGPT in comparison to the control group, but higher oxygen saturation and WBC count. No effects on the platelet count were found. The survival times of the PMX-DHP group were longer than in control.

CONCLUSION

PMX-DHP therapy limited the respiratory impairment, liver dysfunction and leucopenia in a neonatal septic model, which resulted in an improvement of survival time.

Endotoxin-binding affinity of sevelamer hydrochloride

BACKGROUND

Sevelamer hydrochloride has been shown to attenuate circulating biomarkers of inflammation in patients with chronic kidney failure. We hypothesize that sevelamer hydrochloride binds bacterial endotoxin (ET) resulting in a decrease in ET levels and cytokine production.

METHODS

To assess the ET-binding affinity of sevelamer hydrochloride, purified Escherichia coli ET was incubated with sevelamer hydrochloride (0-50 mg/ml). After incubation, ET was measured in supernatants. In addition, THP-1-derived monocytes were co-incubated with supernatants of sevelamer hydrochloride and ET. After 24-hour incubation, TNF-alpha was measured. The effect of pH on the ET-binding affinity of sevelamer hydrochloride, as well as cooperative binding between ET and phosphate for sevelamer hydrochloride were assessed.

RESULTS

Sevelamer hydrochloride exhibited time- and dose-dependent binding affinity for ET, resulting in a marked reduction in free ET levels. The 1-hour dose-dependent ET-binding effect of sevelamer hydrochloride translated into a marked reduction in TNF-alpha levels. Varying the pH conditions did not affect the ET-binding affinity of sevelamer hydrochloride. The addition of phosphate (0-50 mM) resulted in a further reduction in free ET levels, translating into a further increase in the binding affinity of sevelamer hydrochloride for ET.

CONCLUSIONS

This study demonstrates that sevelamer hydrochloride binds to ET, thereby reducing free ET and cytokine levels. Positive cooperative binding was also noted between phosphate and ET for sevelamer hydrochloride. This study supports the hypothesis that sevelamer hydrochloride might bind to ET in the intestinal lumen and reduce systemic inflammation. Animal and human studies are required to examine this hypothesis.

Effect of hemoperfusion using polymyxin B-immobilized fiber on IL-6, HMGB-1, and IFN gamma in a neonatal sepsis model

To evaluate effects of polymyxin B direct hemoperfusion (PMX-DHP) on a neonatal sepsis cecal ligation and perforation (CLP) model, in 24 anesthetized and mechanically ventilated 3-d-old piglets, 16 were assigned to CLP and an arteriovenous extracorporeal circuit from 3 h until 6 h post-CLP, with a PMX-column in PMX-DHP-treated group (8 piglets) and 8 as sham. Plasma lipopolysaccharide (LPS) was measured at before CLP and at 3 and 9 h. Changes in mean systemic blood pressure (mSBP), mean pulmonary blood pressure, serum IL-6, tumor necrosis factor alpha, interferon gamma, and highly mobile group-1 box protein were measured before CLP and at 1, 3, 6, and 9 h. LPS was lower in the sham and PMX-DHP groups than in the control at 9 h. The mSBP was higher in the sham and PMX-DHP groups than in the control at both 6 h. IL-6 was lower in the sham and PMX-DHP groups than in the control at 6 h. HMGB-1 was lower in the PMX-DHP group than in the control at 6 h. IFN-gamma was only detected in the control group at 9 h. Survival times in the PMX-DHP group were longer than in the control. Thus, PMX-DHP improved septic shock in a neonatal septic model.

Endotoxin and cytokine removal in sepsis

Sepsis, the leading cause of mortality in intensive care units, is a complex series of interrelated effects caused by the overproduction of multiple mediators and their unrestrained biological activity. Both proinflammatory and antiinflammatory mediators participate in the high complexity of sepsis and explain the failure of specific therapies to improve survival. Continuous extracorporeal therapies have been proposed as therapeutic options and as tools for blood purification in sepsis. Along these lines and in order to achieve higher clearances and mass removal rates, we studied the effects of plasmafiltration coupled with adsorption and provided in vitro and in vivo evidence that adsoprtion of multiple cytokines, activated complement components, and lipid mediators such as the platelet-activating factor occurs. We also showed that such treatment may lead to improved survival in a rabbit model of sepsis and to improved hemodynamics, reduced norepinephrine dose, and restoration of near-to-normal responsiveness of blood leukocytes to endotoxin in humans. It is anticipated that treatment of plasma, as a modular device to conventional hemofiltration, may pave the way to innovative approaches in the extracorporeal treatment of septic patients.

Traumatic Shock Alias Posttrauma Critical Illness

Trauma is the most common cause of death under the age of 45. Many trauma patients die of multiple organ failure, especially acute respiratory distress syndrome. The basic cause of traumatic shock has only partially been elucidated. Data resources include research papers on the subject of trauma and shock from 1875 to the present. These papers numbered more than 40,000. Almost all of the papers proposed that traumatic shock was due to hypovolemia. The concept of a shock toxin as promulgated during World War I is correct. This toxin is a thrombogenic aminophospholipid that occurs only on the inner layer of all cell membranes and is liberated by cell destruction. It causes disseminated intravascular coagulation, which may obstruct the microcirculation of any and all organs producing multiple organ failure by microclots. These microclots may be lysed by plasminogen activator and circulation to the organs restored.

A Review of Septic Shock

The mortality of septic shock, both in percentage of septic shock cases and total number of septic shock cases, has been increasing over the past several decades. This is despite major advances in diagnosis and treatment. The basic cause of traumatic and septic shock has only partially been elucidated. This review presents information about the basic cause and mechanism of septic shock as well as a new treatment based on this information. Data sources include research papers on the subject of septic shock from 1875 until the present. These papers numbered more than 10,000, most of which are not included in the reference list because many are duplicative. The main result of the review of literature is that all of a wide variety of treatments of septic shock have not resulted in a lowering of mortality, but in fact have increased it. Another toxin (in addition to endotoxin and its secondarily induced host mediators) is proposed. This toxin causes disseminated intravascular coagulation, which may obstruct the microcirculation of any and all organs, producing multiple organ failure by microclots. These microclots may be lysed by plasminogen activator and circulation to the organs restored.

Renal replacement therapies

Slow continuous renal replacement therapy is more hemodynamically stabilizing and is replacing conventional hemodialysis as the therapy of choice for acute renal failure in the intensive care unit. This article presents practical information, including basic terminology, basic physiology, technical aspects, and indications for and application of this technique.

Continuous venovenous hemofiltration improves cardiac performance by mechanisms other than tumor necrosis factor-alpha attenuation during endotoxic shock

OBJECTIVE

To assess the effects of continuous venovenous hemofiltration (CWH) on global and regional hemodynamics, plasma lactate, and tumor necrosis factor-oa (TNF-a) levels during endotoxic shock in dogs.

METHODS

Thirty pentobarbital-anesthetized and mechanically ventilated dogs were divided into six groups of five dogs each. Group 1 served as a control, undergoing CWH at 3 Uhr without endotoxin. Group 2 served as the endotoxin-alone time-matching group. Group 3 received CWH 1 hr after endotoxin at 3 Uhr for 270 mins. Group 4 received CWH 1 hr after endotoxin at 3 Uhr for 150 mins and at 6 Uhr for an additional 120 mins. Group 5 and group 6 received the ultrafiltrate from group 1 and group 3, respectively.

MEASUREMENTS AND MAIN RESULTS

Three hours after endotoxin challenge, dogs treated with CWH at 3 Uhr had a higher cardiac output (4.9 + 0.6 vs. 2.9 + 0.6 Umin; p < .05) and stroke volume (35 + 7 vs. 20 + 4 mL; p < .05) and a lower pulmonary vascular resistance (116 26 vs. 331 + 126 dyne-sec/cm5; p < .05) than the endotoxin-alone group. Five hours after endotoxin, dogs treated with CWH at 6 Uhr also had higher hepatic (464 + 164 vs. 126 + 75 mUmin; p < .05) and femoral (95 + 46 vs. 30 + 34 mL/min; p < .05) blood flow. Moreover, dogs treated with CWH at 6 Uhr had higher mean arterial blood pressure (84 + 24 vs. 40 + 15 mm Hg; p < .05) and left ventricular stroke work index (1.1 + 0.6 vs. 0.2 + 0.2 g/kg; p < .05) than the endotoxin-alone group. Plasma lactate levels were lower in the CWH group at 6 Uhr (2.7 + 1.1 mmol/L) than in the endotoxin-alone group (4.4 + 0.6 mmol/L; p < .05). Plasma TNF-ao levels were unaffected, and only minor amounts of TNF-o were found in the ultrafiltrate.

CONCLUSION

In this acute endotoxic shock model, CWH at 3 Uhr improved cardiac performance and decreased pulmonary vasoconstriction. Moreover, CWH at 6 LUhr also increased arterial blood pressure and left ventricular stroke work, increased hepatic and femoral arterial blood flow, and decreased blood lactate levels. These effects were not attributable to TNF-alpha removal.

Traumatic and septic shock alias post-trauma critical illness

BACKGROUND

The mortality associated with septic shock, both in percentage of septic shock cases and total number of septic shock cases, has been increasing over the past several decades. This is despite major advances in diagnosis and treatment. The basic cause of traumatic and septic shock has been only partially elucidated.

METHODS

Data sources include research papers on the subject of traumatic and septic shock from 1875 to the present. These papers numbered over 10 000, few of which are included in the reference list because many are duplicative or negative. Over 1000 articles were reviewed which documented the unsuccessful search for a treatment for septic shock based on the theory that septic shock is due to endotoxin and its secondarily induced host mediators. These references are available from the author.

RESULTS

and conclusion The concept of a shock toxin in trauma and sepsis as promulgated during World War I is correct. This toxin is a thrombogenic aminophospholipid which occurs only on the inner layer of all cell membranes and is liberated by cell destruction. It causes disseminated intravascular coagulation which may obstruct the microcirculation of any or all organs, producing multiple organ failure by microclots. These microclots may be lysed by plasminogen activator and circulation to the organs restored.

Extracorporeal adsorbent-based strategies in sepsis

Gram-negative bacterial sepsis remains a challenging diagnostic and therapeutic dilemma to the practicing clinician. Bacterial-derived products (eg, gram-negative bacterial lipopolysaccharide or endotoxin) and host inflammatory mediators (eg, tumor necrosis factor-alpha and interleukin-1) are believed to play a pivotal role in the pathogenesis of sepsis and septic shock. Despite the many advances in the treatment of sepsis, mortality rates in septic patients remain high. Indeed, numerous clinical trials using biologically engineered immunotherapies targeting specific inflammatory mediators have proven unsuccessful. This lack of success has led to a renewed interest in blood purification techniques using extracorporeal therapies. During sepsis, circulating bacterial-derived products as well as inflammatory mediators can be reduced and/or eliminated by various extracorporeal adjunctive therapies such as plasma exchange, continuous renal replacement, and adsorbent-based therapies. Adsorbents have commonly been used orally for gastrointestinal removal of toxins or drugs. However, their potential use in sepsis has received little attention. The incorporation of adsorbents in hemoperfusion columns has allowed their use for the removal of toxic compounds from the circulatory system. Adsorbents developed for use in sepsis can bind toxins in a nonselective (eg, charcoal), selective (eg, polymyxin B-immobilized polystyrene-derivative fiber), or specific (eg, antibody-coated microsphere-based detoxification system) way. However, despite an explosive development in the experimental use of these promising therapies, randomized clinical trials are currently lacking. In summary, a multi-disciplinary complex therapeutic approach remains a prerequisite to the successful treatment of sepsis.