Anaphylaxis to protamine sulfate mediated by a complement-dependent IgG antibody

Development of a Novel IgG1 Anaphylaxis Mouse Model with Uniquely Characteristic Skin Manifestations Induced Through the FcγRIII-Histamine Pathway

BACKGROUND

Studies of passive anaphylaxis, in which mouse immunoglobulin G (IgG) and its antigens are administered to mice, believe that platelet-activating factor (PAF) is more important than histamine and that basophils or macrophages are primarily involved. However, the full extent of IgG-dependent anaphylaxis is still unclear; that is, little agreement has been reached about the mechanism.

METHODS

First, we established the novel model of IgG₁ anaphylaxis induced by the intravenous administration of two types of IgG₁ and a fluorescent dye-labeled antigen, as IgG₁ immune complex in HR-1 hairless mice. Subsequently, pharmacological analysis was used to investigate the underlying mechanisms of IgG₁ anaphylaxis in this established model.

RESULTS

The novel IgG₁ anaphylaxis model can induce the IgG-induced Anaphylaxis-dependent Spotted Distribution of fluorescently labeled Immune complexes in the Skin, named "G-ASDIS". Moreover, this model was triggered primarily by the FcγRIII-dependent histamine release, which is different from the conventional model in which PAF was involved in the development of IgG₁ anaphylaxis. Basophils in the circulation and mast cells in the skin may participate in the development of IgG₁ anaphylaxis and increased G-ASDIS.

CONCLUSION

Our results propose that the novel axis, namely the FcγRIII-basophils and/or mast cell-histamine pathway, is important for IgG₁ anaphylaxis. Further analysis of our model in addition to other models will lead to a broader analysis and understanding of the IgG₁ anaphylaxis mechanism.

Protamine Sulphate Hypersensitivity

Protamine hypersensitivity has been documented by intra-dermal skin testing in three patients who demonstrated sudden cardiovascular collapse and bronchospasm following the use of intravenous protamine sulphate. All patients had been given protamine previously. The effects of the anaphylactic response were terminated quickly by the administration of intravenous adrenaline associated with plasma volume expansion. Intra-dermal skin testing against all anaesthetic agents is recommended so that the specific allergen can be identified. In patients who are shown to be allergic to protamine sulphate and who require cardiac or vascular surgery careful monitoring of heparin dosage and neutralisation with hexadimethrine (Polybrene) intravenously appears to be a safe alternative.

The Use of a Heparin Removal Device: A Valid Alternative to Protamine

Purpose

Experiments were carried out to test the efficacy and safety of the heparin removal device, a plasmapheresis filter that binds and eliminates heparin, in the context of extracorporeal circulation.

Procedures and Findings

Six dogs were put on cardiopulmonary bypass after heparinization. Upon weaning, additional heparin was administered to obtain an activated clotting time above 900s. The animals were connected to the heparin removal device and with flows of 500 ml/min, activated clotting time, activated partial thromboplastin time and plasma heparin concentrations were normalised to baseline after 30 min. Hemodynamic parameters remained unaffected. A slight decrease in red and white blood cell count and in platelets was observed which however recovered spontaneously two hours after the filter procedure. No damage to blood components could be observed.

Conclusions

The use of a heparin removal device is as efficient as systemic administration of protamine to reverse the effects of heparinization. It may prevent the adverse reactions linked to protamine administration and therefore be indicated in certain subgroups of patients undergoing cardiopulmonary bypass.

Noncardiogenic pulmonary oedema following cardiopulmonary bypass: report of two cases and review of the literature

Two cases of noncardiogenic pulmonary oedema following cardiopulmonary bypass are presented. The clinical manifestations, postulated pathogenesis and management are discussed. A recent review of the literature fails to yield a unified explanation of this rare but often disastrous entity.

Imidazolium salts as small-molecule urinary bladder exfoliants in a murine model

We present a novel family of small-molecule urinary bladder exfoliants that are expected to be of great value in preclinical studies of urologic conditions and have improved potential for translation compared with prior agents. There is broad urologic interest in the therapeutic potential of such exfoliating agents. The primary agent used in preclinical models, the cationic peptide protamine sulfate (PS), has limited translational potential due to concerns including systemic adverse reactions and bladder tissue injury. Intravesical application of a safe, systemically nontoxic exfoliant would have potential utility in the eradication of Escherichia coli and other uropathogens that reside in the bladder epithelium following cystitis, as well as in chronic bladder pain and bladder cancer. Here, we introduce a family of imidazolium salts with potent and focused exfoliating activity on the bladder epithelium. Synthesis and purification were straightforward and scalable, and the compounds exhibited prolonged stability in lyophilized form. Most members of the compound family were cytotoxic to cultured uroepithelial cells, with >10-fold differences in potency across the series. Upon topical (intravesical) administration of selected compounds to the murine bladder, complete epithelial exfoliation was achieved with physiologically relevant imidazolium concentrations and brief contact times. The exfoliative activity of these compounds was markedly improved in comparison to PS, as assessed by microscopy, immunofluorescence, and immunoblotting for uroplakins. Bladder uroepithelium regenerated within days to yield a histologically normal appearance, and no toxicity was observed. Finally, the chemical scaffold offers an opportunity for inclusion of antimicrobials or conjugation with chemotherapeutic or other moieties.

Anaphylaxis during the perioperative period

Anesthesiologists use a myriad of drugs during the provision of an anesthetic. Many of these drugs have side effects that are dose related, and some lead to severe immune-mediated adverse reactions. Anaphylaxis is the most severe immune-mediated reaction; it generally occurs on reexposure to a specific antigen and requires the release of proinflammatory mediators. Anaphylactoid reactions occur through a direct non-immunoglobulin E-mediated release of mediators from mast cells or from complement activation. Muscle relaxants and latex account for most cases of anaphylaxis during the perioperative period. Symptoms may include all organ systems and present with bronchospasm and cardiovascular collapse in the most severe cases. Management of anaphylaxis includes discontinuation of the presumptive drug (or latex) and anesthetic, aggressive pulmonary and cardiovascular support, and epinephrine. Although a serum tryptase confirms the diagnosis of an anaphylactic reaction, the offending drug can be identified by skin-prick, intradermal testing, or serologic testing. Prevention of recurrences is critical to avoid mortality and morbidity.

Noncardiogenic pulmonary edema immediately following rapid protamine administration

OBJECTIVE

To report the case of a rare, potentially preventable, immediate noncardiogenic pulmonary edema reaction to the rapid administration of protamine during coronary artery bypass graft (CABG) surgery.

CASE SUMMARY

A 74-year-old white man was administered a 250-mg bolus of protamine sulfate toward the end of CABG surgery to reverse the heparin anticoagulation. Immediately following the administration of protamine, oxygen saturation declined, pink frothy sputum was suctioned from the trachea, and 1500 mL of serous fluid was removed from the airway. The patient was stabilized, but the surgeons were unable to close his chest because of the profound edema. Chest closure occurred on hospital day 6, with discharge from the intensive care unit on hospital day 28.

DISCUSSION

Noncardiogenic pulmonary edema is a rare adverse event that occurs in 0.2% of cardiopulmonary bypass patients, with mortality rates approaching 30%. Complement activation or direct pharmacologic release of histamine by high concentrations of protamine is the suspected cause. High concentrations of protamine in the lungs may directly release histamine, with significant vasodilating effects.

CONCLUSIONS

Immediate reversal of heparin anticoagulation with protamine is necessary to control bleeding; however, rapid protamine injection can be associated with life-threatening pulmonary edema. Slower, cautious administration and accurate calculation of protamine doses may prevent such an event.

Mast cell chymase in complex with heparin proteoglycan is regulated by protamine

Protamines are polycationic proteins that are widely used for neutralisation of the anticoagulant action of heparin. However, several reports have shown adverse, mast cell-dependent reactions to protamine. The exact mechanism by which protamine causes these adverse effects is not clear. In the present study, the possibility that protamine may influence mast cell chymase function was investigated. Mast cell chymase is in vivo recovered in a macromolecular complex with heparin proteoglycan, and this interaction is essential for expression of optimal enzymatic activity. Protamine was shown to strongly reduce the activity of mast cell chymase by a mechanism that involved displacement of the chymase from heparin proteoglycan.

Effective and less toxic reversal of low-molecular weight heparin anticoagulation by a designer variant of protamine

PURPOSE

This investigation assessed protamine reversal of heparin anticoagulation by formation of a protamine-heparin alpha-helix by use of a new designer-variant protamine [+18BE] that was made from an existing protamine variant [+18B] whose non-alpha-helix-forming amino acid proline (P) was replaced by an alpha-helix-forming glutamic acid (E). The rate of administration of the new [+18BE] variant protamine on efficacy and toxicity in comparison to that of [+21] standard protamine and [+18B] was also studied.

METHODS

Acetyl-EAA(K2A2K2A)4K2-Amide [+18BE] was administered intravenously in a 1:1 dose to low-molecular-weight heparin (LMWH)-anticoagulated (intravenous 150 IU antifactor Xa/kg) dogs over 10 seconds or 3 minutes (n = 7, each group). Reversal efficacy was documented by measuring activated clotting time, thrombin clotting time, antifactor Xa, and antifactor IIa. Toxicity was defined by measuring systemic blood pressure, heart rate, cardiac output, pulmonary artery pressure, and oxygen consumption. Measurements were made at baseline, after administration of LMWH, before its reversal, and for 30 minutes thereafter. Results were compared with those after LMWH reversal with [+21] standard protamine and the [+18B] variant. A total toxicity score (TTS) was calculated for each compound from maximal declines in blood pressure, heart rate, cardiac output, and oxygen consumption.

RESULTS

LMWH anticoagulation reversal was significantly (p < 0.01) less toxic over 10 seconds and 3 minutes with the [+18BE] designer variant (TTS -2.3, -2.2) compared with the [+21] standard protamine (TTS -6.4, -7.2). Percent LMWH reversal at 3 minutes revealed [+18BE] to have antifactor Xa activity as high as 91%, compared with 68% for protamine [+21], when given over 3 minutes (p < 0.05).

CONCLUSIONS

This investigation documents that a new designer variant of protamine [+18BE] has superior efficacy compared with [+21] standard protamine for reversal of LMWH anticoagulation and that this occurs with a highly favorable toxicity profile.

Reversal of heparin anticoagulation by recombinant platelet factor 4 in humans

BACKGROUND

Protamine is used to reverse the anticoagulant effects of heparin, but it can have important side effects. Platelet factor 4 (PF4) is a protein found in platelet alpha granules that binds to and thereby neutralizes heparin. We evaluated the safety and effectiveness of intravenous recombinant PF4 to neutralize heparin anticoagulation after cardiac catheterization in a phase 1, open-label trial.

METHODS AND RESULTS

The study group consisted of 18 patients having diagnostic cardiac catheterization. Heparin (5000 U) was given after vascular access was obtained. In the first 12 patients, additional heparin was given at the conclusion of the procedure so that all patients had activated coagulation times > 300 seconds before rPF4 was given. Three patients each received 0.5, 1.0, 2.5, or 5.0 mg/kg rPF4 over a period of 3 minutes at the conclusion of the catheterization procedure. In 6 additional patients, extra heparin was not given at the conclusion of the procedure, and 1.0 mg/kg rPF4 was given. Hemodynamic measurements, cardiac output, and serial blood tests were performed 5, 10, 20, and 30 minutes after rPF4 and then into the next 24 hours. There were no serious side effects in any patient, despite transient rPF4 levels as high as 14,870 ng/mL in the patients receiving 5.0 mg/kg. One patient receiving 2.5 mg/kg had a slight transient rise in liver enzymes possibly related to the rPF4. There were no important hemodynamic effects of rPF4 administration at any dose used. Doses of 2.5 and 5.0 mg/kg were uniformly effective in reversing the anticoagulant effect of heparin. At lower doses, rPF4 neutralized the effects of heparin in most but not all patients. Pharmacokinetic analysis suggested a monophasic and one-compartment clearance of the PF4-heparin complex. No neutralizing factors to rPF4 were detected in the samples collected 7 days after dosing.

CONCLUSIONS

rPF4, in doses ranging from 0.5 to 5.0 mg/kg over 3 minutes, had no serious side effects. Given in sufficient amounts, rPF4 can completely and rapidly reverse the anticoagulant effects of heparin.

Heparin and protamine use in peripheral vascular surgery: a comparison between surgeons of the Society for Vascular Surgery and the European Society for Vascular Surgery

It was the intent of this study to document, in general, the patterns and complications of heparin and protamine usage during carotid endarterectomy, aortic and femoral-popliteal-tibial reconstructions for occlusive disease, elective and emergent abdominal aortic aneurysmectomy, thromboembolectomy, and dialysis arteriovenous (AV) fistula placement by surgeons from North America and Europe. All vascular surgeons from the Society for Vascular Surgery (SVS) and the European Society for Vascular Surgery (ESVS) were surveyed by a voluntary, self-reported questionnaire. Six hundred and forty-six completed questionnaires (284 from SVS and 362 from ESVS), representing a 62% response rate, were returned for evaluation. Systemic and regional administration of heparin was common during vascular procedures performed by both SVS and ESVS surgeons. Use of protamine to reverse heparin anticoagulation varied among SVS and ESVS surgeons, respectively, during: carotid endarterectomy (54% vs. 26%, p < 0.01), elective aortic reconstruction for occlusive disease (58% vs. 23%, p < 0.001), elective aortic reconstruction for abdominal aortic aneurysm (63% vs. 27%, p < 0.001), and femoral-popliteal-tibial reconstruction (44% vs. 15%, p < 0.001). Adverse reactions to protamine among the 25,219 and 12,902 cases reported from SVS and ESVS surgeons, respectively, included: hypotension (1209 and 495 cases), pulmonary artery hypertension (65 and eight cases), anaphylaxis (52 and 10 cases), and death (seven and two cases). These adverse responses accounted for 5.3% and 4.0% of the SVS and ESVS cases, respectively. Although this study is subject to the known limitations of a retrospective survey, it is clear that heparin use is common. Protamine reversal of heparin anticoagulation is more common in North America.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug allergy

Although allergic drug reactions are just one type of adverse reaction to medications, they are clinically very important because of the morbidity and mortality they cause. An ever-expanding pharmacopeia increases the potential for allergic drug reactions. An understanding of the types of allergic drug reactions, their immunopathologic mechanisms, and the most likely medications involved; an approach to determine the drug responsible for the reaction; and ways to prevent future allergic drug reactions are important features in minimizing patient morbidity.

Allergy to protamine

Recent advances in medicine, such as cardiac catheterization, phoresis, dialysis, and cardiopulmonary bypass technology, have increased the need for heparin anticoagulation. To antagonize heparin's effect and prevent hemorrhagic complications after the procedure, protamine has likewise been used more frequently. With its increased use have come increased reports of adverse protamine reactions consisting of rash, urticaria, elevation of pulmonary artery pressure, systemic hypotension, and, at times, death. The elevation of pulmonary artery pressure, which appears to be a rather common occurrence in animals, may be an isolated finding without clinical consequences in humans. However, this pulmonary vasoconstriction may, when severe, lead to acute right-sided heart failure and systemic hypotension. Other protamine reactions involve a decrease in systemic vascular resistance and systemic hypotension without changes in pulmonary artery pressure. Causes of acute protamine reactions may involve the generation of anaphyatoxins and prostanoids either from protamine-heparin complexes or complement-fixing antiprotamine IgG antibodies, from inhibition of plasma Carboxypeptidase N, from crosslinking of cell-surface antiprotamine IgE on mast cells and basophils with subsequent mediator release, or from potentiation of IgE-mediated release of histamine through a polycationin-recognition site. Although we have come a long way in understanding the mechanisms by which protamine can cause its ill effects in humans, more work is clearly needed to define, in prospective studies, the incidence of and risk factors for protamine reactions in various patient groups, and to delineate more clearly which mechanisms are involved in each clinical type of acute protamine reaction. Hopefully, this will lead to strategies and protamine alternatives that will prevent or diminish, in frequency or severity, adverse protamine reactions. Alternatively, a clearer picture of the risk factors important for protamine reactions and the predictive value of diagnostic tests (e.g., protamine IgE antibody) can also minimize the clinical impact of this increasingly common adverse event.

Serial immunological investigations in a patient who had a life-threatening reaction to intravenous protamine

Reactions to intravenous protamine include rash, urticaria, bronchospasm, hypotension, and/or pulmonary artery pressure elevation. We have previously shown that in diabetic patients receiving daily protamine-insulin injections, the presence of anti-protamine IgE or IgG antibodies are significant risk factors for acute, life-threatening reactions when protamine is given intravenously. To study protamine reactions further, we measured serum anti-protamine IgE and IgG antibody levels, in-vitro basophil histamine release and intracutaneous skin testing to protamine serially in an NPH-insulin dependent diabetic who had a severe, protracted anaphylactic reaction to protamine. At the time of his protamine reaction, his serum contained 8.5 ng/ml of anti-protamine IgE and 1.3 micrograms/ml of anti-protamine IgG antibody. One month following the reaction both anti-protamine IgE and IgG increased to 16 ng/ml (twofold rise) and 90.5 micrograms/ml (70-fold rise), respectively. With time, both anti-protamine IgE and IgG antibody declined. Serial intradermal skin tests using protamine sulphate did not discriminate between the protamine reactor and nine normal control subjects who had no prior exposure nor any demonstrable serum IgE antibody to protamine. In-vitro basophil histamine release to protamine sulphate was inconclusive in discriminating between the protamine reactor and normal control subjects. We postulate that protamine may be an incomplete or univalent antigen that must first combine with a tissue macromolecule or possibly heparin to become a complete multivalent antigen capable of eliciting IgE antibody-dependent mediator release.

Safety of protamine sulfate administration in vasectomized men

The majority of vasectomized men develop antibodies against different sperm antigens, including protamine. Due to the fact that salmon protamine is used clinically for heparin reversal and that a cross-reactivity has been observed between human and salmon protamine, vasectomized men may be at risk for adverse reactions to protamine sulfate. In order to explore this possibility, serum samples were analyzed for the presence of anti-sperm and anti-protamine antibodies in 20 vasectomized and 20 non-vasectomized men (controls) about to undergo major heart surgery requiring heparin reversal. The patients were closely monitored for any possible reaction following the injection of protamine. Anti-sperm antibodies were detected in the serum of 15 of the vasectomized men whereas only two of the non-vasectomized subjects had this type of antibody. Twenty-five percent of the vasectomized men presented with anti-protamine antibodies; in the control group, none of the patients had developed this type of antibody. Following the administration of protamine sulfate, none of the patients in either group showed any adverse reaction to the drug. It is concluded that vasectomized men are not at increased risk towards adverse reactions following the injection of protamine sulfate.

A prospective study of the risk of an immediate adverse reaction to protamine sulfate during cardiopulmonary bypass surgery

Protamine sulfate administration may cause life-threatening reactions. We prospectively examined the incidence of immediate adverse reaction after protamine in 243 patients who underwent cardiopulmonary bypass surgery. Twenty-six patients (10.7%) had reactions, and 1.6% had a precipitous drop in blood pressure immediately after protamine administration. Risk factors were previous exposure to protamine, diabetes, history of receiving protamine-containing insulin, and possibly vasectomy. However, neither a positive skin test nor a positive IgE ELISA for antiprotamine antibody predicted that a patient would have a reaction. C4a levels were increased in patients who had reactions as compared with age-, sex-, and cardiac disease-matched patients who did not have reactions, suggesting a role for complement in some reactions. Immediate adverse reactions to protamine are very common, and alternative therapies are urgently needed to eliminate the use of protamine.

Lack of cross-reactivity between IgE to salmon and protamine sulfate

Immediate type-generalized reactions to protamine sulfate are uncommon but may be fatal. The mechanisms of severe or fatal reactions are unknown in most cases. One theory is that contaminating fish (salmon) proteins present in protamine solutions induce anaphylaxis in salmon-sensitive subjects. A second hypothesis is that protamine interacts with anti-salmon IgE to cause anaphylaxis. We assessed these hypotheses by establishing an indirect amplified enzyme-linked immunosorbent assay (ELISA) for IgE to salmon. Sera obtained from two subjects anaphylactically sensitive to salmon demonstrated high binding to salmon that was not inhibited by preincubation of sera with 500 or 1000 micrograms of protamine or Aspergillus fumigatus. Serum from a patient who experienced anaphylactic shock from protamine was indistinguishable from control sera in the ELISA for IgE to salmon. Anti-protamine IgE could not be demonstrated in separate experiments. The assays prove that 1) serum IgE to salmon is not inhibited by protamine and 2) serum from a patient experiencing a severe reaction to protamine did not contain IgE to salmon or protamine. The experiments do not support the notion that there is cross-reactivity between IgE to salmon and protamine sulfate in the cases evaluated.

Association of protamine IgE and IgG antibodies with life-threatening reactions to intravenous protamine

Life-threatening reactions to intravenous protamine, administered to reverse heparin anticoagulation, have been reported with increasing frequency as a consequence of the escalating use of cardiac catheterization and coronary bypass surgery. Retrospective studies have shown that such reactions are more common in diabetic patients receiving daily subcutaneous injections of protamine-insulin preparations. To determine whether anti-protamine IgE or IgG antibodies might explain the increased risk for protamine reactions among patients with protamine-insulin-dependent diabetes, we conducted a case-control study of 27 patients (diabetic and nondiabetic) who had acute reactions to intravenous protamine and 43 diabetic patients who tolerated protamine without a reaction during diagnostic or surgical procedures. Cases and controls were grouped according to previous exposure to protamine-insulin preparations. In diabetic patients who had received protamine-insulin injections, the presence of serum antiprotamine IgE antibody was a significant risk factor for acute protamine reactions (relative risk, 95; P = 1.0 X 10(-5), as was antiprotamine IgG (relative risk, 38; P = 1.2 X 10(-5). No patients without previous exposure to protamine-insulin injections had serum protamine IgE antibodies. In this group, anti-protamine IgG antibody was a risk factor for protamine reactions (relative risk, 25; P = 0.0062). We conclude that in protamine-insulin-dependent diabetics, the increased risk of serious reactions when intravenous protamine was given appeared to be caused largely by antibody-mediated mechanisms. In nondiabetic subjects, the presence of protamine IgG was significantly associated with an increased risk of acute protamine reactions, although many nondiabetic subjects who had reactions had no IgG antibodies.

Complement activation from protamine sulfate administration after coronary angiography

The cause of hypotension after reversal of heparin by protamine has not been well defined. In this study we evaluated complement activation (C3a and C4a) by the heparin-protamine complex in 46 consecutive patients (40 received protamine sulfate to reverse heparin, and six did not) during and after coronary angiography. In patients receiving protamine sulfate, there was a significant increase in C3a over the value before protamine sulfate administration (P less than .001) or in patients who did not receive protamine sulfate (P less than .05): 807 +/- 100 ng/ml vs. 274 +/- 75 ng/ml. There were no significant changes in C4a after protamine sulfate administration. These results indicate that the alternate complement pathway is activated when protamine sulfate is administered after coronary angiography. This may induce hypotension as well as platelet aggregation and thrombus formation and may contribute to coronary instability. Therefore, in unstable patients, heparin reversal by protamine should not be done routinely.

Acute pulmonary vasoconstriction and thromboxane release during protamine reversal of heparin anticoagulation in awake sheep. Evidence for the role of reactive oxygen metabolites following nonimmunological complement activation

When protamine (2 mg/kg) was injected intravenously into awake sheep 5 minutes after infusing heparin (200 units/kg), there was transient diffuse pulmonary vasoconstriction with mean pulmonary arterial pressure increasing from 18.0 +/- 0.7 to 43.8 +/- 2.7 mm Hg at 1 minute (x +/- SEM; n = 10). In addition, there was profound leukopenia (36.9 +/- 7.7% of baseline values at 2 minutes) with transpulmonary leukocyte sequestration and transiently elevated plasma concentrations of C3a (from 420 +/- 146 to 1,599 +/- 249 ng/ml; n = 3, p less than 0.01) and thromboxane B2 (from 0.30 +/- 0.05 to 6.3 +/- 2.8 ng/ml; n = 10, p less than 0.0001), without significant increases of plasma 6-keto-prostaglandin F1 alpha, prostaglandin F2 alpha, leukotrienes, or histamine. Intravenous injection of protamine alone produced no hemodynamic effects and did not increase plasma levels of vasoconstrictor eicosanoids. Intravenous pretreatment with either a cyclooxygenase inhibitor or a hydrogen peroxide scavenger (dimethylthiourea) blocked both the increases of thromboxane levels and the pulmonary vasoconstriction.

Unpredictable anaphylactic reaction to protamine sulfate

Anaphylactic reactions to protamine administration often can be predicted by the presence of patient risk factors. In the case described, an anaphylactic reaction to protamine occurred in a patient without identifiable risk factors. A history of prior protamine exposure, fish allergy, or vasectomy suggests patients may be at greater risk for anaphylactic response to protamine; however, patients can develop anaphylaxis in the absence of such factors.

The myocardial contractile responses to protamine sulfate and heparin

The administration of protamine sulfate for the reversal of heparin anticoagulation has been associated with adverse hemodynamic changes including hypotension and decreased cardiac output. The possible direct toxic effect of protamine on human right atrial trabeculae contracting isometrically in vitro was studied. Muscles were stimulated to contract at 1 Hz in Tyrode's solution (maintained at 34 degrees C, pH 7.4) into which protamine was continuously added. Following a polynomial regression analysis, a parabolic dose-response curve resulted. The equation was: y = 95.13 + 38.76x - 278.71x2 where y = relative developed force and x = concentration of protamine (milligrams per milliliters) (r = 0.82). The estimated concentration of protamine resulting in 50% developed force was 0.48 mg/ml. In a second series of experiments, protamine was added to the bath along with a neutralizing amount of heparin. This resulted in a limited reduction in the fall of relative developed force. Thus, protamine in high concentrations alone or in complex with heparin has a direct toxic effect on human myocardial muscle mechanics, and care is warranted in its clinical use.

Anaphylaxis

The clinical syndrome of anaphylactic shock is a disorder produced by multiple mechanisms and pharmacological and environmental factors. The syndrome may be produced by both immunologic and nonimmunologic mechanisms and is due to the release of preformed biologically active mediators and the generation of biologically active mediators. The main mediator appears to be histamine. Although there are a number of defined predisposing factors, the majority of first reactions appear unpredictably. The mainstay of treatment is the use of epinephrine, volume replacement, and positive pressure ventilation. The follow-up and documentation of details of the reaction and exhaustive efforts to determine the precipitating factor are important aspects of the subsequent safety of the patient. History may be of more value than diagnostic testing. The use of H1 and H2 blockers, with steroids and sympathomimetics, may reduce the risk or magnitude of reactions in patients with a past history of a reaction.

The mechanisms and management of noncardiogenic pulmonary edema following cardiopulmonary bypass

Cardiac surgeons have become more cognizant of the syndrome of noncardiogenic pulmonary edema after cardiopulmonary bypass. Although this syndrome is rare, its occurrence can be catastrophic. This article reviews the current understanding of several factors that have been implicated in the cause of this syndrome and discusses the various options for management of the problem once it has arisen.

Complement activation and anaphylactoid response to protamine in a child after cardiopulmonary bypass

A 2 1/2 year old boy had a sudden, severe, and unexpected anaphylactoid reaction after an otherwise uncomplicated repair of a partial atrioventricular septal defect. The reaction, comprising haemorrhagic pulmonary oedema and peripheral circulatory collapse, followed neutralisation of heparin by protamine. Measurements of serum complement (C3 and C4) concentrations suggested that a pronounced consumption of complement occurred during the adverse response.

Increased risk of severe protamine reactions in NPH insulin-dependent diabetics undergoing cardiac catheterization

Protamine is widely used for reversing systemic heparinization after cardiac catheterization. Although rare, major reactions to protamine that simulate anaphylaxis occasionally occur and have previously been associated only with an allergic reaction to fish. Because neutral protamine Hagedorn (NPH) insulin includes protamine, it might be anticipated that NPH insulin-dependent diabetic patients would develop sensitivity to protamine. Of 866 consecutive patients undergoing cardiac catheterization over a 20 month period, 651 received protamine for reversal of heparinization. Of these, 8.5% (56/651) were diabetics and 2.3% (15/651) were NPH insulin-dependent diabetics. During this period seven patients were observed immediately after administration of protamine to have major adverse reactions that required the administration of catecholamines. One death ensued. Of the seven major reactions, four occurred in NPH insulin-dependent diabetics and one occurred in a patient with an allergy to fish. The incidence of major protamine reactions was 27% (4/15) in the NPH insulin-dependent diabetics vs 0.5% (3/636) in those with no history of NPH insulin use (p less than .001). This represents a 50-fold increased risk of a major reaction to protamine if the patient was receiving NPH insulin. Accordingly, we recommend that diabetics on NPH insulin and patients with allergies to fish undergo cardiac catheterization without the use of protamine or, when necessary, that protamine be administered cautiously in anticipation of a major adverse reaction.

Successful cardiopulmonary bypass in diabetics with anaphylactoid reactions to protamine

Two insulin dependent diabetics with previous anaphylactic like (anaphylactoid) reactions to protamine underwent successful cardiopulmonary bypass for coronary artery surgery. Platelet concentrates instead of protamine were used to neutralise their systemic heparinisation. In both cases the anaphylactoid reactions first became apparent after administration of protamine sulphate at the end of cardiac catheterisation. These cases show that adverse reactions to protamine need not be a contraindication to cardiopulmonary bypass and cardiac surgery and emphasise that this condition should be considered in all patients with a history of previous protamine exposure or one which may be associated with anaphylactoid reactions to protamine.

Cardiac arrest following protamine administration

A case report of fatal cardiac arrest following protamine reversal of systemic heparinization during vascular surgery is presented. Patients who have received protamine zinc insulin, NPH insulin, and those with previous exposure to protamine sulphate or allergy to fish are more likely to have a reaction to protamine. Protamine-induced hypotension can be mediated by immunological or non-immunological mechanisms. Several alternative methods of heparin reversal which may avoid similar catastrophes are presented.

Adverse reactions to protamine sulfate following cardiac surgery

We report four patients who developed severe adverse reactions to protamine sulfate following cardiac surgery. Two types of reactions were seen. First, an immediate anaphylaxis which is a complement-dependent IgG antibody-mediated reaction. In the literature, 80% of patients who had similar reactions have had previous exposure to protamine. All patients adequately tested had positive skin tests and there is 6% mortality. The second reaction to protamine during cardiac surgery is characterized by delayed onset and profound vascular damage presenting as noncardiogenic pulmonary edema or total vascular collapse with prolonged hypotension and anasarca. These patients have negative skin tests and in our studies, no evidence of antibody mediated reaction, suggesting some other mechanisms may play a part. The mortality is high (30% of patients reported) and survivors have significant morbidity.