Bradykinin is a mediator of anaphylactoid reactions during hemodialysis with AN69 membranes

Hypersensitive Reactions During Hemodialysis Treatment: What Do We Need to Know?

Kidney replacement therapies (KRTs) including hemodialysis (HD) are one of the treatment options for most of the patients with end-stage kidney disease. Although HD is vital for these patients, it is not hundred percent physiological, and various adverse events including hypersensitivity reactions may occur. Fortunately, these reactions are rare in total and less when compared to previous decades, but it is still very important for at least two reasons: First, the number of patients receiving kidney replacement treatment is increasing globally; and the cumulative number of these reactions may be substantial. Second, although most of these reactions are mild, some of them may be very severe and even lead to mortality. Thus, it is very important to have basic knowledge and skills to diagnose and treat these reactions. Hypersensitivity reactions can occur at any component of dialysis machinery (access, extracorporeal circuit, medications, etc.). The most important preventive measure is to avoid the allergen. However, even with very specific test, sometimes the allergen cannot be found. In mild conditions, HD can be contained with non-specific treatment (topical creams, antihistaminics, corticosteroids). In more severe conditions, treatment must be stopped immediately, blood should not be returned to patient, drugs must be stopped, and rules of general emergency treatment must be followed.

Challenges in Septic Shock: From New Hemodynamics to Blood Purification Therapies

Sepsis and septic shock are associated with high mortality, with diagnosis and treatment remaining a challenge for clinicians. Their management classically encompasses hemodynamic resuscitation, antibiotic treatment, life support, and focus control; however, there are aspects that have changed. This narrative review highlights current and avant-garde methods of handling patients experiencing septic shock based on the experience of its authors and the best available evidence in a context of uncertainty. Following the first recommendation of the Surviving Sepsis Campaign guidelines, it is recommended that specific sepsis care performance improvement programs are implemented in hospitals, i.e., "Sepsis Code" programs, designed ad hoc, to achieve this goal. Regarding hemodynamics, the importance of perfusion and hemodynamic coherence stand out, which allow for the recognition of different phenotypes, determination of the ideal time for commencing vasopressor treatment, and the appropriate fluid therapy dosage. At present, this is not only important for the initial timing, but also for de-resuscitation, which involves the early weaning of support therapies, directed elimination of fluids, and fluid tolerance concept. Finally, regarding blood purification therapies, those aimed at eliminating endotoxins and cytokines are attractive in the early management of patients in septic shock.

The Characteristics of Dialysis Membranes: Benefits of the AN69 Membrane in Hemodialysis Patients

Patients undergoing hemodialysis (HD) experience serious cardiovascular complications, through malnutrition, inflammation, and atherosclerosis. Amputation for peripheral arterial disease (PAD) is more prevalent in patients undergoing HD than in the general population. In addition, revascularization procedures in dialysis patients are often associated with subsequent amputation and high mortality rates. To improve the prognosis of dialysis patients, malnutrition and inflammation must be properly treated, which necessitates a better understanding of the characteristics of dialysis membranes. Herein, the characteristics of several dialysis membranes were studied, with a special reference to the AN69 membrane, noting several similarities to low-density lipoprotein (LDL)-apheresis, which is also applicable for the treatment of PAD. Both systems (LDL-apheresis and AN69) have anti-inflammatory and anti-thrombogenic effects because they use a negatively charged surface for extracorporeal adsorptive filtration from the blood/plasma, and contact phase activation. The concomitant use of both these therapeutic systems may have additive therapeutic benefits in HD patients. Here, we reviewed the characteristics of dialysis membranes and benefits of the AN69 membrane in dialysis patients.

Effect of Continuous Renal Replacement Therapy with the oXiris Hemofilter on Critically Ill Patients: A Narrative Review

Critically ill patients with sepsis and severe COVID-19 are commonly characterized by a dysregulated immune response and an acute kidney injury. Continuous renal replacement therapy (CRRT) is now proposed as a promising adjuvant therapy to treat these critically ill patients by removing cytokines, pathogen-associated molecular patterns, and damage-associated molecular patterns from the blood. Although multiple hemofilters, including high-cutoff membranes, the oXiris hemofilter, the CytoSorb hemoadsorption device, and the Toraymyxin hemoperfusion cartridge, have been used in current clinical practice, the use of the oXiris hemofilter in critically ill patients is of particular interest because it is the only kind of hemofilter that can provide renal replacement therapy, remove endotoxins, and adsorb cytokines simultaneously. During the past five years, a growing body of literature has shown that CRRT with the oXiris hemofilter can improve hemodynamics and organ function and can decrease cytokines and endotoxins in both septic and COVID-19 patients. Here, we performed a narrative review to describe the development history of the oXiris hemofilter and to discuss the therapeutic effect of oXiris-CRRT on critically ill patients by searching the PubMed, Web of Science, and clinicaltrials.gov databases for articles published from inception to 8 September 2022 (updated on 1 November) with an English language restriction. We also summarized the current knowledge on anticoagulation techniques and safety concerns when delivering oXiris-CRRT sessions.

Ammonia Clearance with Different Continuous Renal Replacement Therapy Techniques in Patients with Liver Failure

INTRODUCTION

Continuous renal replacement therapy (CRRT) can be used to treat hyperammonaemia. However, no study has assessed the effect of different CRRT techniques on ammonia clearance.

METHODS

We compared 3 different CRRT techniques in adult patients with hyperammonaemia, liver failure, and acute kidney injury. We protocolized CRRT to progressively deliver continuous veno-venous haemofiltration (CVVH), haemodialysis (CVVHD) or haemodiafiltration (CVVHDF). Ammonia was simultaneously sampled from the patient's arterial blood and effluent fluid for each technique. We applied accepted equations to calculate clearance.

RESULTS

We studied 12 patients with a median age of 47 years (interquartile range [IQR] 25-79). Acute liver failure was present in 4 (25%) and acute-on-chronic liver failure in 8 (75%). There was no significant difference in median ammonia clearance between CRRT technique; CVVH: 27 (IQR 23-32) mL/min versus CVVHD: 21 (IQR 17-28) mL/min versus CVVHDF: 20 (IQR 14-28) mL/min, p = 0.32. Moreover, for all techniques, ammonia clearance was significantly less than urea and creatinine clearance; urea 50 (47-54) mL/min versus creatinine 42 (IQR 38-46) mL/min versus ammonia 25 (IQR 18-29) mL/min, p = 0.0001.

CONCLUSION

We found no significant difference in ammonia clearance according to CRRT technique and demonstrated that ammonia clearance is significantly less than urea or creatinine clearance.

Blood-incompatibility in haemodialysis: alleviating inflammation and effects of coagulation

Blood-incompatibility is an inevitability of all blood-contacting device applications and therapies, including haemodialysis (HD). Blood leaving the environment of blood vessels and the protection of the endothelium is confronted with several stimuli of the extracorporeal circuit (ECC), triggering the activation of blood cells and various biochemical pathways of plasma. Prevention of blood coagulation, a major obstacle that needed to be overcome to make HD possible, remains an issue to contend with. While anticoagulation (mainly with heparin) successfully prevents clotting within the ECC to allow removal of uraemic toxins across the dialysis membrane wall, it is far from ideal, triggering heparin-induced thrombocytopenia in some instances. Soluble fibrin can form even in the presence of heparin and depending on the constitution of the patient and activation of platelets, could result in physical clots within the ECC (e.g. bubble trap chamber) and, together with other plasma and coagulation proteins, result in increased adsorption of proteins on the membrane surface. The buildup of this secondary membrane layer impairs the transport properties of the membrane to reduce the clearance of uraemic toxins. Activation of complement system-dependent immune response pathways leads to leukopenia, formation of platelet–neutrophil complexes and expression of tissue factor contributing to thrombotic processes and a procoagulant state, respectively. Complement activation also promotes recruitment and activation of leukocytes resulting in oxidative burst and release of pro-inflammatory cytokines and chemokines, thereby worsening the elevated underlying inflammation and oxidative stress condition of chronic kidney disease patients. Restricting all forms of blood-incompatibility, including potential contamination of dialysis fluid with endotoxins leading to inflammation, during HD therapies is thus still a major target towards more blood-compatible and safer dialysis to improve patient outcomes. We describe the mechanisms of various activation pathways during the interaction between blood and components of the ECC and describe approaches to mitigate the effects of these adverse interactions. The opportunities to develop improved dialysis membranes as well as implementation strategies with less potential for undesired biological reactions are discussed.

Anaphylactoid reaction during hemodiafiltration on AN69 membrane in a patient with atypical hemolytic uremic syndrome: A pediatric case report

Reactions associated with hemodiafiltration can be life threatening if not recognized early in the course of dialysis. AN69 (acrylonitrile and sodium methallyl sulfonate copolymer) membrane-associated reactions during hemodialysis have been documented in adult patients receiving angiotensin converting enzyme inhibitors, which are thought to be triggered by the negative charge of the AN69 membrane. Here, we present a 5-month-old girl requiring continuous renal replacement therapy (CRRT) for acute kidney injury secondary to atypical hemolytic uremic syndrome who experienced acute cyanosis, angioedema, tachycardia, and impaired circulation during CRRT. After switching to a different type of hemofiltration membrane, her clinical findings improved and she was able to tolerate hemodialysis. We concluded that she had experienced an anaphylactoid reaction to the AN69 membrane. To our knowledge, this case is the first pediatric case report of AN69 membrane-associated anaphylactoid reaction.

Hemodynamic disturbances and oliguria during continuous kidney replacement therapy in critically ill children

BACKGROUND

About 1.5% of patients admitted to the Pediatric Intensive Care Unit (PICU) will require continuous kidney replacement therapy (CKRT)/renal replacement therapy (CRRT). Mortality of these patients ranges from 30 to 60%. CKRT-related hypotension (CKRT-RHI) can occur in 19-45% of patients. Oliguria after onset of CKRT is also common, but to date has not been addressed directly in the scientific literature.

METHODS

A prospective observational study was conducted to define factors involved in the hemodynamic changes that take place during the first hours of CKRT, and their relationship with urinary output.

RESULTS

Twenty-five patients who were admitted to a single-center PICU requiring CKRT between January 1, 2014, and December 31, 2018, were included, of whom 56.3% developed CKRT-RHI. This drop in blood pressure was transient and rapidly restored to baseline, and significantly improved after the third hour of CKRT, as core temperature and heart rate decreased. Urine output significantly decreased after starting CKRT, and 72% of patients were oliguric after 6 h of therapy. Duration of CKRT was significantly longer in patients presenting with oliguria than in non-oliguric patients (28.7 vs. 7.9 days, p = 0.013).

CONCLUSIONS

The initiation of CKRT caused hemodynamic instability immediately after initial connection in most patients, but had a beneficial effect on the patient's hemodynamic status after 3 h of therapy, presumably owing to decreases in body temperature and heart rate. Urine output significantly decreased in all patients and was not related to negative fluid balance, patient's hemodynamic status, CKRT settings, or kidney function parameters.

Changes in hemodynamics, renal blood flow and urine output during continuous renal replacement therapies

Continuous renal replacement therapies (CRRT) affect hemodynamics and urine output. Some theories suggest a reduced renal blood flow as the cause of the decreased urine output, but the exact mechanisms remain unclear. A prospective experimental study was carried out in 32 piglets (2–3 months old) in order to compare the impact of CRRT on hemodynamics, renal perfusion, urine output and renal function in healthy animals and in those with non-oliguric acute kidney injury (AKI). CRRT was started according to our clinical protocol, with an initial blood flow of 20 ml/min, with 10 ml/min increases every minute until a goal flow of 5 ml/kg/min. Heart rate, blood pressure, central venous pressure, cardiac output, renal blood flow and urine output were registered at baseline and during the first 6 h of CRRT. Blood and urine samples were drawn at baseline and after 2 and 6 h of therapy. Blood pressure, cardiac index and urine output significantly decreased after starting CRRT in all piglets. Renal blood flow, however, steadily increased throughout the study. Cisplatin piglets had lower cardiac index, higher vascular resistance, lower renal blood flow and lower urine output than control piglets. Plasma levels of ADH and urine levels of aquaporin-2 were lower, whereas kidney injury biomarkers were higher in the cisplatin group of piglets. According to our findings, a reduced renal blood flow doesn’t seem to be the cause of the decrease in urine output after starting CRRT.

Hemodynamic Effects of Connection to Continuous Renal Replacement Therapy in a Pediatric Animal Model

To assess the hemodynamic effects of connection to continuous renal replacement therapy (CRRT) in a pediatric experimental animal model. Prospective experimental study was performed using piglets between 2 and 3 months of age and 9-11 kg. CRRT with a Prismaflex^R monitor and HF20 filter (surface of 0.2 m² ) was started after monitoring and anesthetic induction with an initial blood flow at 20 mL/min with 10 mL/min increases every minute until the goal flow of 5 mL/kg/min was achieved. Heart rate, blood pressure, central venous pressure, cardiac index, and renal blood flow were registered at baseline, 5, 15, 30, 60, 120, 180, 240, and 360 min. IBM SPSS Statistics 20.0 package was used for analysis. A P value of <0.05 was considered statistically significant. Thirty-four piglets were studied. Blood pressure, cardiac output, and systemic vascular resistance significantly decreased 5-min after CRRT connection (mean arterial pressure from 85.5 to 70.8 mm Hg, P < 0.001, cardiac index from 3.6 to 3.3 L/min/m² P = 0.024, and systemic vascular resistance index from 1759 to 1607 dyn.s/cm⁵ P = 0.012). No significant changes were found in renal blood flow or central venous pressure. All parameters gradually increased at 15 and 30 min after connection but complete recovery was never achieved. Connection to CRRT produces a significant decrease in arterial pressure, cardiac index, and peripheral vascular resistances in hemodynamically stable piglets.

Diagnosis, Treatment, and Prevention of Hemodialysis Emergencies

Given the high comorbidity in patients on hemodialysis and the complexity of the dialysis treatment, it is remarkable how rarely a life-threatening complication occurs during dialysis. The low rate of dialysis emergencies can be attributed to numerous safety features in modern dialysis machines; meticulous treatment and testing of the dialysate solution to prevent exposure to trace elements, toxins, and pathogens; adherence to detailed treatment protocols; and extensive training of dialysis staff to handle medical emergencies. Most hemodialysis emergencies can be attributed to human error. A smaller number are due to rare idiosyncratic reactions. In this review, we highlight major emergencies that may occur during hemodialysis treatments, describe their pathogenesis, offer measures to minimize them, and provide specific interventions to prevent catastrophic consequences on the rare occasions when such emergencies arise. These emergencies include dialysis disequilibrium syndrome, venous air embolism, hemolysis, venous needle dislodgement, vascular access hemorrhage, major allergic reactions to the dialyzer or treatment medications, and disruption or contamination of the dialysis water system. Finally, we describe root cause analysis after a dialysis emergency has occurred to prevent a future recurrence.

Safety and tolerability during build-up phase of a rush venom immunotherapy

BACKGROUND

Safety and tolerability of venom immunotherapy (VIT) in patients with concomitant disease and comedications, especially β-blockers (BBs) and angiotensin-converting enzyme inhibitors (ACEIs), are under discussion.

OBJECTIVE

To identify risk factors for the occurrence of systemic reactions (SRs) during the build-up phase of a 3-day rush VIT with focus on comorbidities and related comedications.

METHODS

Data of 175 three-day rush VIT courses (Vespula venom, n = 161; honeybee venom, n = 14) were analyzed. Starting with 0.02 μg of venom, the maintenance dose of 100 μg was reached in 15-dose increments within 3 days. Local reactions (LRs) and SRs were documented during the build-up phase. Comorbidities and related comedications were registered. Univariate, bivariate, and multivariate data analysis was performed.

RESULTS

During the 3-day rush VIT, an LR was seen in 74 (42.3%) of 175, a large LR (>10-cm diameter) in 82 (46.9%) of 175, and SRs in 19 (10.9%) of 175 VIT courses. Multivariate logistic regression revealed that female sex (P = .01), immunotherapy with honeybee venom (P = .003), and accompanying ACEI medication (P = .03) were independent predictors of the development of SRs during the build-up phase of VIT.

CONCLUSION

This study revealed that female sex, honeybee VIT, and ACEI use independent predictors for SRs.

Evaluation of the Biocompatibility of Dialysis Membranes

BACKGROUND

Improvements in the biocompatibility of dialysis membranes have reduced biological responses elicited by blood-membrane interactions. In this article, recent technological developments in dialysis membranes with regard to biocompatibility and recent progress in the evaluation of the biocompatibility of dialysis membranes are reviewed.

SUMMARY

The focus of investigation into dialysis membranes in recent years has focused on not only membrane materials, but also their surface textures, which have been changed, for example, by coating with vitamin E or by changing the amount and type of hydrophilizing agents used. Research and development is directed at altering the chemical and physical properties of membrane surfaces to suppress biological responses that are particularly elicited as a result of platelet activation. To develop membranes with excellent biocompatibility, biocompatibility should be evaluated on a like-for-like basis under conditions that are similar to those in clinical settings. Evaluation using actual dialyzers can be performed using porcine blood, platelet-rich plasma isolated from porcine blood (and platelet-rich plasma with leukocytes), or suspension of neutrophils isolated from porcine blood or cultured human monocytes.

KEY MESSAGES

Highly biocompatible dialysis membranes can be developed when the overall correlations among biological reactions are examined by integrating all data on biological responses elicited by blood-membrane interactions or mutual interactions among blood cells.

Activation of basophils is a new and sensitive marker of biocompatibility in hemodialysis

The hemodialysis procedure involves contact between peripheral blood and the surface of dialyzer membranes, which may lead to alterations in the pathways of innate and adaptive immunity. We aimed to study the effect of blood–membrane interaction on human peripheral basophils and neutrophils in hemodialysis with high- and low-permeability polysulfone dialyzers. The surface expression of CD203c (basophil selection marker) and CD63 (activation marker) after activation by the bacterial peptide formyl-methionyl-leucyl-phenylalanine (fMLP) or anti-Fcε receptor I (FcεRI) antibody and the absolute number of basophils was investigated before and after hemodialysis with each of the dialyzers. Moreover, the expression on neutrophils of CD11b, the CD11b active epitope, and CD88 was analyzed in the same groups of individuals. The expression of CD63 in basophils following activation by fMLP was significantly higher in the patient group compared with that in healthy controls, but no differences were observed after activation by anti-FcεRI. During the hemodialysis procedure, the low-flux membrane induced up-regulation of CD63 expression on basophils, while passage through the high-flux membrane did not significantly alter the responsiveness. In addition, the absolute number of basophils was unchanged after hemodialysis with either of the dialyzers and compared with healthy controls. We found no significant differences in the expression of the neutrophil activation markers (CD11b, the active epitope of CD11b, and CD88) comparing the two different dialyzers before and after dialysis and healthy controls. Together, these findings suggest that alterations in basophil activity may be a useful marker of membrane bioincompatibility in hemodialysis.

Clinical Implication of the Renin-angiotensin-aldosterone Blockers in Chronic Kidney Disease Undergoing Hemodialysis

The renin-angiotensin-aldosterone system (RAAS) blockers have been widely used in chronic kidney disease patients undergoing hemodialysis; however, whether RAAS blockers have beneficial effects for cardiovascular disease in those patients has not been fully defined. This review focuses on the effects of RAAS blockers in chronic kidney disease undergoing hemodialysis for cardiovascular disease.

Recurrent intradialytic heparin induced anaphylaxis: workup and management

Heparin has been widely used for intradialytic anticoagulation since the 1940s. Heparin induced anaphylaxis can be life threatening, mandating early recognition and intervention. However, due to its relative rarity many physicians remain unaware. We report the case of a 70-year-old woman requiring dialysis, who developed recurrent anaphylaxis to intradialytic heparin. We describe a systematic approach to confirm the suspected heparin allergy, which must include an evaluation of predisposing factors, the dialysis equipment and concomitant medications. Further workup for safe alternatives employing skin prick and intradermal tests, as well as provocation tests are discussed.

High-flux versus low-flux membranes for end-stage kidney disease

BACKGROUND

Clinical practice guidelines regarding the use of high-flux haemodialysis membranes vary widely.

OBJECTIVES

We aimed to analyse the current evidence reported for the benefits and harms of high-flux and low-flux haemodialysis.

SEARCH METHODS

We searched Cochrane Renal Group's specialised register (July 2012), the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1948 to March 2011), and EMBASE (1947 to March 2011) without language restriction.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared high-flux haemodialysis with low-flux haemodialysis in people with end-stage kidney disease (ESKD) who required long-term haemodialysis.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two authors for study characteristics (participants and interventions), risks of bias, and outcomes (all-cause mortality and cause-specific mortality, hospitalisation, health-related quality of life, carpal tunnel syndrome, dialysis-related arthropathy, kidney function, and symptoms) among people on haemodialysis. Treatment effects were expressed as a risk ratio (RR) or mean difference (MD), with 95% confidence intervals (CI) using the random-effects model.

MAIN RESULTS

We included 33 studies that involved 3820 participants with ESKD. High-flux membranes reduced cardiovascular mortality (5 studies, 2612 participants: RR 0.83, 95% CI 0.70 to 0.99) but not all-cause mortality (10 studies, 2915 participants: RR 0.95, 95% CI 0.87 to 1.04) or infection-related mortality (3 studies, 2547 participants: RR 0.91, 95% CI 0.71 to 1.14). In absolute terms, high-flux membranes may prevent three cardiovascular deaths in 100 people treated with haemodialysis for two years. While high-flux membranes reduced predialysis beta-2 microglobulin levels (MD -12.17 mg/L, 95% CI -15.83 to -8.51 mg/L), insufficient data were available to reliably estimate the effects of membrane flux on hospitalisation, carpal tunnel syndrome, or amyloid-related arthropathy. Evidence for effects of high-flux membranes was limited by selective reporting in a few studies. Insufficient numbers of studies limited our ability to conduct subgroup analyses for membrane type, biocompatibility, or reuse. In general, the risk of bias was either high or unclear in the majority of studies.

AUTHORS' CONCLUSIONS

High-flux haemodialysis may reduce cardiovascular mortality in people requiring haemodialysis by about 15%. A large well-designed RCT is now required to confirm this finding.

Continuous renal replacement therapy in dogs and cats

Continuous renal replacement therapy (CRRT) is a relatively new extracorporeal blood purification modality that is rapidly gaining acceptance for the treatment of acute kidney injury in cats and dogs. The author has used CRRT for the treatment of leptospirosis, tumor lysis syndrome, heatstroke, pre- and postsurgical support of ureteral obstructions, as well as aminoglycoside and melamine toxicities. As the name implies, CRRT is a slow gradual process, and once treatment begins, patients continue therapy until their renal function returns, they are transitioned to intermittent hemodialysis (IHD), or they are euthanized. Unlike IHD, which is a primarily diffusive therapy, CRRT uses diffusion as well as convection. Because of its efficient use of fluids, CRRT units use prepackaged fluids, eliminating the need for costly water purification systems that are needed for IHD.

Heparin-induced anaphylactic and anaphylactoid reactions: two distinct but overlapping syndromes

BACKGROUND

Heparin-induced anaphylactic and anaphylactoid reactions are of increasing clinical and scientific interest, particularly given the recent identification of a syndrome of heparin-induced anaphylaxis due to oversulfated chondroitin sulfate (OSCS), a contaminant in certain heparin preparations. However, heparin-induced anaphylactoid reactions also have been reported to be a consequence of immune-mediated heparin-induced thrombocytopenia (HIT).

OBJECTIVE

To summarize the clinical features and pathophysiology of two distinct disorders, HIT-associated anaphylactoid reactions as well as anaphylaxis resulting from OSCS-contaminated heparin.

METHODS

We review literature describing these two types of heparin-induced anaphylactic and anaphylactoid reactions, and seek potential pathophysiologic links between them.

RESULTS

Intravenous bolus heparin administered to patients with circulating 'HIT antibodies', usually as a result of recent heparin therapy, can produce anaphylactoid reactions, probably as a consequence of in vivo activation of platelets and, possibly, leukocytes. Affected patients often evince fever/chills, hypertension and/or acute respiratory compromise ('pseudo-pulmonary embolism'). In contrast, heparin-induced anaphylaxis is caused by activation of the contact system, with formation of vasoactive kinins (bradykinin, des-arg(9)-bradykinin). This latter syndrome has been linked in an epidemic form to administration of OSCS-contaminated heparin; these reactions feature prominent hypotension and laryngeal edema. Hemodialysis patients are at increased risk for both syndromes. There is evidence that OSCS-contaminated heparin itself increases the risk of HIT compared with non-contaminated heparin.

CONCLUSION

Two distinct syndromes of heparin-induced anaphylaxis and anaphylactoid reactions exist. These seem to share certain epidemiologic features, given that OSCS-contaminated heparin can produce anaphylaxis through contact system activation but also could increase risk of HIT and HIT-associated anaphylactoid reactions.

Hypertension in dialysis and kidney transplant patients

For the first time, the Canadian Hypertension Education Program has studied the evidence supporting blood pressure control in people requiring renal replacement therapy for end-stage kidney disease, including those on dialysis and with renal transplants. According to the Canadian Organ Replacement Registry's 2008 annual report, there were an estimated 33,832 people with end-stage renal disease in Canada at the end of 2006, an increase of 69.7% since 1997. Of these, 20,465 were on dialysis and 13,367 were living with a functioning kidney transplant. Thus, it is becoming more likely that primary care practitioners will be helping to care for these complex patients. With the lack of large controlled clinical trials, the consensus recommendation based on interpretation of the existing literature is that blood pressure should be lowered to below 140/90 mmHg in hypertensive patients on renal replacement therapy and to below 130/80 mmHg for renal transplant patients with diabetes or chronic kidney disease.

Safety of angiotensin-converting enzyme inhibitors while receiving venom immunotherapy

BACKGROUND

Case reports have raised concern about concurrent use of angiotensin-converting enzyme inhibitors (ACE-Is) in patients receiving venom immunotherapy (VIT). No surveys have been performed on the number of venom allergic patients who take ACE-Is and their outcomes.

OBJECTIVE

To survey the use of ACE-Is and systemic reaction (SR) characteristics in patients receiving VIT.

METHODS

A retrospective medical record review was performed on all patients evaluated for Hymenoptera venom allergy at a single center from 2000 to 2005. Patient records were evaluated for presenting symptoms, specific IgE testing, VIT treatment course, ACE-I use during VIT, and the presence of any SRs to field stings or VIT.

RESULTS

Of 288 patients evaluated from 2000 to 2005 for Hymenoptera venom allergy, 157 were found to have venom specific IgE. Of these 157 patients, 79 (50%) of those with Hymenoptera venom allergy underwent VIT. Seventeen of these 79 patients (21%) were taking an ACE-I during VIT. The mean overlap of a patient taking an ACE-I with the time they were receiving VIT was 30.9 months (range, 3-114 months). Patients taking ACE-Is were older (mean age, 56.2 vs 36.4 years; P < .001) and received VIT for a longer period (mean, 72.3 vs 29.9 months; P < .04). Thirteen of 62 patients not taking an ACE-I (21%) experienced an SR during their VIT. No patients taking an ACE-I experienced an SR to VIT while taking an ACE-I (P = .03).

CONCLUSIONS

This study suggests that there is not an association between ACE-I use and increased frequency of SRs to venom immunotherapy.

Shortness of Breath and Abdominal Pain Within Minutes of Starting Hemodialysis

A 45-year-old woman on hemodialysis without significant problems for 6 years developed acute onset of anxiety, shortness of breath, and abdominal pain within minutes of initiating her hemodialysis treatment. Her blood pressure was stable throughout the episode. The treatment was discontinued and she was admitted to the hospital. Routine blood chemistries were unremarkable except for mild eosinophilia (5%). An ethylene oxide reaction was suspected. She was dialyzed the following day after rinsing the dialyzer with 2 L of saline. A similar reaction occurred. The following day she was dialyzed on an ethylene oxide-free dialyzer and the hemodialysis treatment was uneventful.

The effect of electronegativity and angiotensin-converting enzyme inhibition on the kinin-forming capacity of polyacrylonitrile dialysis membranes

The combination of negatively-charged membranes and angiotensin I-converting enzyme inhibitors (ACEi) evokes hypersensitivity reactions (HSR) during hemodialysis and bradykinin (BK)-related peptides have been hypothesized as being responsible for these complications. In this study, we tested the effects of neutralizing the membrane electronegativity (zeta potential) of polyacrylonitrile AN69 membranes by coating a polyethyleneimine layer (AN69-ST membranes) over the generation of kinins induced by blood contact with synthetic membranes. We used minidialyzers with AN69 or AN69-ST membranes in an ex vivo model of plasma and we showed that plasma dialysis with AN69 membranes led to significant BK and des-Arg(9)-BK release, which was potentiated by ACEi. This kinin formation was dramatically decreased by AN69-ST membranes, even in the presence of an ACEi, and kinin recovery in the dialysates was also significantly lower with these membranes. High molecular weight kininogen and factor XII detection by immunoblotting of the protein layer coating both membranes corroborated the results: binding of these proteins and contact system activation on AN69-ST membranes were reduced. This ex vivo experimental model applied to the plasma, dialysate and dialysis membrane could be used for the characterization of the kinin-forming capacity of any biomaterial potentially used in vivo in combination with drugs which modulate the pharmacological activity of kinins.

[Drug treatment of hypertension in hemodialysed patients]

A fraction of the dialyzed patients remains hypertensive despite achievement of the "dry weight" and will eventually require a pharmacological antihypertensive treatment. There is only scarce randomized intervention trials available in those patients so it is difficult to estimate whether the cardiovascular benefit of the treatment is related to blood pressure lowering per se or to class or drug specific properties. This paper reviews the different class of antihypertensive drugs focusing on their advantages and disadvantages in dialysis patients. On a practical ground, prescription will be driven by pharmacokinetics considerations and mostly according to specific indications pertinent to cardiovascular complications associated with hypertension.

Dialysis headache

We describe the various side effects occurring in dialysis sessions and indicate measures for their prevention and/or treatment. Next, we analyze dialysis headache in terms of incidence, prevalence, criteria for its inclusion in the classification of the International Headache Society, and factors related to its triggering, ie, bradykinin and nitric oxide (NO), which have increased plasma levels during dialysis. This permits a critical analysis in comparison with NO donor headache in terms of the pathophysiologic mechanisms that mediate the triggering of both conditions. A similarity is particularly detected in terms of the role of NO as the last link in the chain of events that precedes the onset of headache, which is preceded by a latency period of 3 to 4 hours, much longer than the few seconds needed to inactivate NO. A hypothesis is raised to explain this phenomenon, opening new perspectives for the study of the pathophysiology of headaches, including primary headaches.

Kinin-dependent hypersensitivity reactions in hemodialysis: metabolic and genetic factors

Although the association of angiotensin I-converting enzyme inhibitors (ACEis) with a negatively charged membrane is thought to be responsible for hypersensitivity reactions (HSRs) during hemodialysis, we hypothesize that these complications are due to changes in plasma aminopeptidase P (APP) activity and genotype. To test this hypothesis, we measured plasma APP activity in 14 patients who suffered HSR (HSR+) while dialyzed with an AN69 membrane and simultaneously treated with an ACEi. APP activity was also studied in a control group (n=39) dialyzed under the same conditions, but who did not suffer any side effect (HSR-). We found significantly decreased plasma APP activity (P=0.013) in HSR+ subjects as well as altered degradation of endogenous des-Arginine(9)-bradykinin, with a significantly lower beta value (P<0.001). The same analytical approach was taken in 171 relatives of HSR+ patients. Variance component analysis suggested that genetic differences may explain 61% of the phenotypic variability of plasma APP activity (P<0.001) and the kinetic parameters that characterized kinin degradation. We also showed that the C-2399A single-nucleotide polymorphism at the XPNPEP2 locus was a significant predictor of APP activity in the 39 HSR- controls (P=0.029). Furthermore, a recessive genetic model for the A allele disclosed a significant difference in mean APP activity by genotype (P<0.001). Finally, our study defined the nonspecific inhibition of recombinant APP by some ACEis. In conclusion, this paper highlights the complexity of HSR in hemodialysis, suggesting, as with angioedema, that these rare, but life-threatening adverse events are governed by several metabolic and genetic factors.

Management of hypertension in hemodialysis patients

The relationship of hypertension with adverse outcomes is uncertain in the hemodialysis population. If hypertension is an etiologically significant cardiovascular risk factor in hemodialysis patients, the first step would be to assess the level of BP accurately. BP obtained at home over a week and averaged using a validated oscillometric automatic device can prove valuable. To the extent BP lowering influences cardiovascular outcomes, home BP of 150/90 mm Hg would warrant therapy, since it correlates with target organ damage and hypertension diagnosed by ambulatory BP monitoring. To manage hypertension, limiting dietary sodium intake and individualizing dialysate sodium delivery would be first steps. The magnitude of reduction in BP with dietary sodium restriction and the whether dialysate sodium can be safely limited in those who are hypotension-prone is unclear. Antihypertensive drug therapies can effectively reduce BP and are needed by the vast majority of hemodialysis patients. Whether control of hypertension translates into better outcomes is not known, but collective evidence suggests that hypertension should be controlled in hemodialysis patients.

Haemodialysis-associated anaphylactic and anaphylactoid reactions

Anaphylactic and anaphylactoid reactions related to haemodialysis have been increasingly described for almost 3 decades. The majority of these cases used to occur with ethylene oxide sterilized, and complement-activating cellulose membranes. However, a considerable number of publications have focused on polyacrylonitrile AN69 high flux membranes, angiotensin converting enzyme inhibitors and iron as other important causes of potentially severe haemodialysis-related anaphylactoid reactions. Clinical manifestations vary considerably and generally do not allow differentiation between IgE-mediated anaphylaxis and anaphylactoid reactions (e.g. from nonspecific mediator release). Successful management of these patients requires multidisciplinary approach and involves prompt recognition and treatment by the attending physician, and identification of the offending agent(s) with subsequent avoidance of the incriminated compound(s). This review focuses on some major causes of anaphylactoid and anaphylactic reactions during haemodialysis. Special consideration is given to the therapeutic and diagnostic approach.

In vitro and in vivo evaluation of Adacolumn cytapheresis in healthy subjects

Adacolumn is a medical device for adsorptive cytapheresis. It has been developed for selective adsorption of granulocytes and monocytes from peripheral blood of patients with immune disorders, such as autoimmune diseases and chronic inflammatory diseases. A double blind sham-controlled crossover study design was used in order to evaluate in vivo biological responses of leukocytes as well as biocompatibility during and after Adacolumn cytapheresis in healthy volunteers. In addition, experiments were undertaken to further evaluate leukocyte reactions to Adacolumn carrier (G-1: cellulose diacetate) beads in vitro. Six healthy volunteers, 4 males and 2 females, with a mean age of 26.7 years were randomly assigned to one of the two treatment arms in a crossover fashion. Three subjects received a single Adacolumn treatment, followed by a single sham treatment at an interval of 7 days. The other three subjects received the two treatments in reverse order. All subjects were followed up 7 days after the last treatment. Additionally, in vitro investigations were carried out using blood from the healthy donors to examine the effect of G-1 beads on granulocyte functions. In vitro exposure of human peripheral blood to G-1 beads caused downregulation of L-selectin expression and upregulation of Mac-1 expression on granulocytes, leading to a marked reduction of adhesive capacity of granulocytes to endothelial cells. The exposure also led to decreased granulocyte chemotactic activity to IL-8. The number of granulocytes and monocytes clearly decreased during Adacolumn cytapheresis. Granulocytes showed marked phenotypic changes of L-selectin(Low) and Mac-1(Hi) after passing through Adacolumn in vivo. Expression of TNF-alpha and chemokine receptors was downregulated. In addition, TNF-alpha and IL-1beta producing capacity of peripheral blood leukocytes was decreased after Adacolumn cytapheresis and these changes lasted even one week after the cytapheresis. The level of complement fragments, C3a and C5a, increased, while bradykinin concentration did not change during Adacolumn cytapheresis. Exposure of human peripheral blood to G-1 beads, both in vitro and in vivo, caused a significant reduction of adhesive capacity and proinflammatory cytokine producing capacity of peripheral blood leukocytes. Such changes were not observed after sham apheresis. Despite complement activation, tolerability of Adacolum cytapheresis was not influenced. These findings may at least partly explain the beneficial effect of Adacolumn cytapheresis in the treatment of autoimmune diseases.

Dialyzer reactions in a patient switching from peritoneal dialysis to hemodialysis

Many terms have been used to describe the collection of signs and symptoms triggered by the initial use of dialyzers. These reactions can be divided into Type A (hypersensitivity reactions, with the incidence of 4/100,000) and Type B (nonspecific reactions, incidence 3-5/100). Many different mechanisms have been postulated, including complement activation, pulmonary leukostasis, hypersensitivity to ethylene oxide, interaction between the AN69 membrane and angiotensin-converting enzyme inhibitors, and dialysate contamination. An unusual case of dialyzer reactions is presented here, involving a patient who had to discontinue peritoneal dialysis when she was admitted with fungal peritonitis. Upon initiation of hemodialysis, she experienced dyspnea and burning sensation and demonstrated significant leukopenia, thrombocytopenia, and oxygen desaturation. These reactions persisted despite double-rinsing of the dialyzers and the use of several different dialyzers with synthetic membranes (polysulfone and AN69), and a variety of sterilization methods (electron beam and gamma radiation). In the end, a simple measure was found to be effective in preventing further dialyzer reactions in this fascinating case.

Contact activation in low-density lipoprotein apheresis systems

BACKGROUND

Anaphylactoid reactions due to contact activation have been observed in patients on ACE inhibitor therapy and hemodialysis with negatively charged dialysis membranes. Negatively charged surfaces are functional constituents of different LDL apheresis systems. Therefore, contact activation was investigated during LDL apheresis with three different systems: (i) heparin-induced extracorporeal LDL precipitation (HELP); (ii) dextran sulfate cellulose (DSC) columns; and (iii) modified polyacrylate gels (DALI) in a clinical setting.

METHODS

24 prevalent patients on regular LDL apheresis treatment were included in the study. Bradykinin, prekallikrein, and HMW kininogen were measured during a single LDL apheresis at different sites of the systems.

RESULTS

LDL apheresis with DSC and DALI was associated with an extreme release of bradykinin after the passage of plasma or blood through the LDL adsorbers as well as with a decrease of prekallikrein and HMW kininogen during the course of the treatment. Bradykinin release exceeded the degradation capacity of the kininase II, since markedly elevated bradykinin concentrations were observed in the arterial line of the extracorporeal circuits of both systems. This was not associated with anaphylactoid reactions. In contrast to the treatments with DSC and DALI, the HELP system did not lead to any activation of the kallikrein-kinin system.

CONCLUSION

From our data we conclude that angiotensin converting enzyme (ACE) inhibitors are contraindicated in patients on LDL apheresis with the DSC and the DALI system. Because the HELP system does not activate the kallikrein-kinin system, patients who need ACE inhibitors are predisposed for this LDL apheresis procedure.

International union of pharmacology. XLV. Classification of the kinin receptor family: from molecular mechanisms to pathophysiological consequences

Kinins are proinflammatory peptides that mediate numerous vascular and pain responses to tissue injury. Two pharmacologically distinct kinin receptor subtypes have been identified and characterized for these peptides, which are named B1 and B2 and belong to the rhodopsin family of G protein-coupled receptors. The B2 receptor mediates the action of bradykinin (BK) and lysyl-bradykinin (Lys-BK), the first set of bioactive kinins formed in response to injury from kininogen precursors through the actions of plasma and tissue kallikreins, whereas the B(1) receptor mediates the action of des-Arg9-BK and Lys-des-Arg9-BK, the second set of bioactive kinins formed through the actions of carboxypeptidases on BK and Lys-BK, respectively. The B2 receptor is ubiquitous and constitutively expressed, whereas the B1 receptor is expressed at a very low level in healthy tissues but induced following injury by various proinflammatory cytokines such as interleukin-1beta. Both receptors act through G alpha(q) to stimulate phospholipase C beta followed by phosphoinositide hydrolysis and intracellular free Ca2+ mobilization and through G alpha(i) to inhibit adenylate cyclase and stimulate the mitogen-activated protein kinase pathways. The use of mice lacking each receptor gene and various specific peptidic and nonpeptidic antagonists have implicated both B1 and B2 receptors as potential therapeutic targets in several pathophysiological events related to inflammation such as pain, sepsis, allergic asthma, rhinitis, and edema, as well as diabetes and cancer. This review is a comprehensive presentation of our current understanding of these receptors in terms of molecular and cell biology, physiology, pharmacology, and involvement in human disease and drug development.

Drug therapy for hypertension in hemodialysis patients

The majority of end-stage renal disease (ESRD) patients are hypertensive. Drug therapy for hypertension in hemodialysis (HD) patients includes all classes of antihypertensive drugs, with the sole exception of diuretics. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers may decrease morbidity and mortality by reducing the mean arterial pressure (MAP), aortic pulse wave velocity, and aortic systolic pressure augmentation, as well as left ventricular hypertrophy (LVH) and probably reduction of C-reactive protein (CRP) and oxidant stress. Potential risk factors include hyperkalemia, anaphylactoid reaction with AN69 membranes (particularly ACE inhibitors), and aggravation of renal anemia. beta-blockers decrease not only mortality, blood pressure (BP), and ventricular arrhythmias, but also improve left ventricular function in ESRD patients. Nonselective beta-blockers can cause an increase in serum potassium (particularly during fasting or exercise). Lisinopril and atenolol have a predominant renal excretion and therefore a prolonged half life in ESRD patients. Thus thrice-weekly supervised administration of these drugs after HD can enhance BP control. The use of calcium channel blockers is also associated with lower total and cardiovascular-specific mortality in HD patients. Minoxidil is a very potent vasodilator that is generally reserved for dialysis patients with severe hypertension. Hypertensive dialysis patients who are noncompliant with their medications may benefit from transdermal clonidine therapy once a week. The majority of dialysis patients need a combination of several antihypertensive drugs for adequate BP control.

Covalently immobilized thrombomodulin inhibits coagulation and complement activation of artificial surfaces in vitro

Thrombomodulin (TM) serves as the endothelial cell receptor for thrombin and alters its characteristics from pro- to anticoagulant. Additionally, it promotes the formation of activated protein C. We evaluated the conservation of the overall outcome of these functions in recombinant TM linked to artificial surfaces by incubation with human whole blood in vitro. TM was covalently immobilized through poly(ethylene glycol) (PEG) spacers onto thin films of poly(octadecene alt maleic anhydride) covering planar glass substrates. TM binding to the polymer films was achieved after active ester formation at the carboxylic acid terminus of the PEG spacers and thoroughly characterized by HPLC-based amino acid analysis, immunofluorescence and ellipsometry. TM-coated samples were incubated for 3h with freshly drawn whole human blood anticoagulated with heparin (5IU/ml) using in-house developed incubation systems. The substantially reduced activation of blood coagulation (TAT) for TM-coated samples correlates well with the degree of contact activation (bradykinin and FXIIa formation) while no significant effects were observed for the platelet activation (PF4). Further, complement activation (C5a levels), was strongly diminished at the TM-containing surfaces. We conclude that the suggested method for preparation of TM immobilization may serve to prepare model substrates for studies on TM interactions but similarly provides a promising coating strategy for blood contacting medical devices.

Congestive heart failure in patients with chronic kidney disease and on dialysis

CHF is highly prevalent in ESRD and is a leading cause of death in such patients. Hypertension, renal anemia, and comorbid conditions such as coronary artery disease are particularly important risk factors for CHF in ESRD. Dialysis hypotension may be a marker of poor prognosis in such persons. Recent studies suggest that lipid peroxidation and L-carnitine deficiency may contribute to CHF in some patients with ESRD. All forms of renal replacement therapy are capable of ameliorating symptoms of CHF, but their effect on cardiovascular mortality has not been firmly established. Drug therapy, particularly angiotensin-converting enzyme inhibitors and beta-adrenergic receptor blockers, is under-used in patients with ESRD and CHF. Heart/kidney transplantation may be a viable option for some patients with advanced CHF and ESRD.

The pharmacokinetics and pharmacodynamics of angiotensin-receptor blockers in end-stage renal disease

Angiotensin-converting enzyme (ACE) inhibitors and more recently angiotensin-receptor blockers (ARBs) have become popular therapies in the end-stage renal disease (ESRD) patient. The ability of either of these drug classes to reduce blood pressure in the ESRD patient is well accepted; however, there is considerably less information available to guide the clinician in the safe and effective use of these drugs in the ESRD patient with congestive heart failure and/or coronary artery disease. Head-to-head studies in the ESRD patient are lacking for both drug classes. Several pharmacokinetic factors can influence the selection of these drugs, including dialysability and the propensity for systemic accumulation. ACE inhibitors (ACE-Is) and ARBs are recognised as having a range of nonpressor effects that are pertinent to patients with ESRD. Such effects include their ability to decrease both thirst drive and erythropoiesis. These drug classes, though, are distinguishable by the unique adverse effect profile for ACE-Is. As is the case in patients without renal failure, ESRD patients can experience cough and, less frequently, angioneurotic oedema with ACE-Is. In the ESRD population, so-called anaphylactoid dialyser reactions can occur in conjunction with ACE-I use. The use of a drug from within the ARB class carries both less risk and permits a compound with a preferred pharmacokinetic profile limited dialysability and minimal systemic accumulation to be administered. These attributes would favour the increased use of ARBs in this population.

Hypotensive reaction during staphylococcal protein A column therapy in a patient with anomalous degradation of bradykinin and Des-Arg9-bradykinin after contact activation

BACKGROUND

Hypotensive reactions have occurred in patients taking angiotensin converting enzyme (ACE) inhibitors after infusion of blood previously in contact with negatively charged surfaces capable of generating kinins, which accumulate when ACE, a kininase, is inhibited. A patient with anomalous bradykinin (BK) metabolism who experienced hypotension during extracorporeal staphylococcal protein A (SPA) therapy while on an ACE inhibitor was studied.

CASE REPORT

A patient with mitomycin-associated hemolytic-uremic syndrome received SPA treatments after her ACE inhibitor, lisinopril, was held. Lisinopril was restarted before her 18th SPA treatment, and immediately after return of treated plasma she developed facial redness and hypotension, which resolved after the return stopped and recurred when restarted. To study formation and degradation of kinins, exposed her plasma to glass beads. We found a normal kinin formation rate but an abnormal degradation and accumulation of Des-Arg9-BK. The kinin degradation enzymes ACE, aminopeptidase P (APP), and carboxypeptidase N (CPN) were measured while on an ACE inhibitor, showing absence of ACE activity, low APP, but normal CPN.

CONCLUSION

This patient's vasodilation and hypotension during SPA therapy was associated with a pre- existing anomaly of BK metabolism. Her ACE inhibitor shifted degradation toward Des-Arg9-BK formation, and her low APP was associated with a prolonged t50 and accumulation of the vasoactive Des-Arg9-BK.

Hepatorenal syndrome. Definition, pathophysiology, and intervention

Hepatorenal syndrome is a well characterized entity in which vasodilation of splanchnic vessels and intense constriction of the renal cortical vasculature occur in concert. The condition is often fatal unless orthotopic liver transplantation (OLT) is performed. Many extracorporeal blood purification techniques exist which can be offered to patients awaiting OLT. Continuous hemofiltration, with or without other modalities such as therapeutic plasma exchange and hemoperfusion, may be helpful in improving the level of consciousness of these patients. Unfortunately, mortality and hepatic regeneration do not appear to be affected by such interventions. The development of a hybrid bioartifical liver support system and pharmacologic manipulation of the hemodynamic perturbations that occur in HRS provide particularly appealing prospects as a means of providing a bridge to liver transplantation in the future.