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

Cardiovascular and Respiratory Toxicity of Protamine Sulfate in Zebrafish and Rodent Models

Protamine sulfate (PS) is the only available option to reverse the anticoagulant activity of unfractionated heparin (UFH), however it can cause cardiovascular and respiratory complications. We explored the toxicity of PS and its complexes with UFH in zebrafish, rats, and mice. The involvement of nitric oxide (NO) in the above effects was investigated. Concentration-dependent lethality, morphological defects, and decrease in heart rate (HR) were observed in zebrafish larvae. PS affected HR, blood pressure, respiratory rate, peak exhaled CO₂, and blood oxygen saturation in rats. We observed hypotension, increase of HR, perfusion of paw vessels, and enhanced respiratory disturbances with increases doses of PS. We found no effects of PS on human hERG channels or signs of heart damage in mice. The hypotension in rats and bradycardia in zebrafish were partially attenuated by the inhibitor of endothelial NO synthase. The disturbances in cardiovascular and respiratory parameters were reduced or delayed when PS was administered together with UFH. The cardiorespiratory toxicity of PS seems to be charge-dependent and involves enhanced release of NO. PS administered at appropriate doses and ratios with UFH should not cause permanent damage of heart tissue, although careful monitoring of cardiorespiratory parameters is necessary.

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.

Heparin-binding copolymer reverses effects of unfractionated heparin, enoxaparin, and fondaparinux in rats and mice

The parenteral anticoagulants may cause uncontrolled and life-threatening bleeding. Protamine, the only registered heparin antidote, is partially effective against low-molecular weight heparins, completely ineffective against fondaparinux and may cause unacceptable toxicity. Therefore, we aimed to develop a synthetic compound for safe and efficient neutralization of all parenteral anticoagulants. We synthesized pegylated PMAPTAC block copolymers, and then, we selected a lead heparin-binding copolymer (HBC). We assessed the effectiveness of HBC in the model of arterial thrombosis electrically induced in the carotid artery of rats by measuring thrombus weight, bleeding time, activated partial thromboplastin time, activated clotting time, and anti-factor Xa activity. The intravital tissue distribution, the cardiorespiratory, and organ toxicity were monitored. HBC diminished antithrombotic and anticoagulant effects of unfractionated heparin. Moreover, it stopped bleeding and completely reversed the enhancement of clotting times and anti-factor Xa activity caused by enoxaparin or fondaparinux. We observed slight pulmonary congestion and cell infiltration, but the cardiorespiratory parameters remained unchanged. We found a strong signal of fluorescently-labeled HBC in the urine, and a weaker in the liver and in the kidney. No signs of hepatic or nephrotoxicity were observed in the blood biochemistry or histopathologic examination. We developed a copolymer efficiently neutralizing effects of heparins in the living organism, which shows a very promising efficacy/safety profile and may help in the management of uncontrolled bleeding resulting from an anticoagulant injection. HBC could enable the safe replacement of unfractionated heparin with low-molecular weight heparins in patients undergoing cardiac surgery and complex vascular procedures.

The Toxicokinetic Profile of Dex40-GTMAC3-a Novel Polysaccharide Candidate for Reversal of Unfractionated Heparin

Though protamine sulfate is the only approved antidote of unfractionated heparin (UFH), yet may produce life threatening side effects such as systemic hypotension, catastrophic pulmonary vasoconstriction or allergic reactions. We have described 40 kDa dextrans (Dex40) substituted with glycidyltrimethylammonium chloride (GTMAC) as effective, immunogenically and hemodynamically neutral inhibitors of UFH. The aim of the present study was to evaluate in mice and rats toxicokinetic profile of the most promising polymer—Dex40-GTMAC3. Polymer was rapidly eliminated with a half-time of 12.5 ± 3.0 min in Wistar rats, and was mainly distributed to the kidneys and liver in mice. The safety studies included the measurement of blood count and blood biochemistry, erythrocyte osmotic fragility and the evaluation of the histological alterations in kidneys, liver and lungs of mice and rats in acute and chronic experiments. We found that Dex40-GTMAC3 is not only effective but also very well tolerated. Additionally, we found that protamine may cause overt hemolysis with appearance of permanent changes in the liver and kidneys. In summary, fast renal clearance behavior and generally low tissue accumulation of Dex40-GTMAC3 is likely to contribute to its superior to protamine biocompatibility. Intravenous administration of therapeutic doses to living animals does not result in the immunogenic, hemodynamic, blood, and organ toxicity. Dex40-GTMAC3 seems to be a promising effective and safe candidate for further clinical development as new UFH reversal agent.

Chemically modified poly(2-hydroxyethyl methacrylate) cryogel for the adsorption of heparin

Various clinical procedures, such as cardiovascular surgery or extracorporeal blood purification, involve systemic anticoagulation using heparin. High concentrations of circulating heparin require neutralization due to possible serious bleeding complications. The intravenous administration of the heparin antagonist protamine sulfate is routinely clinically performed, but is frequently associated with adverse reactions. Therefore, there is a need for a valid and safe alternative to achieve extracorporeal heparin removal from blood or plasma, such as a filter, a matrix, or an adsorbent. Here, we describe the development of a macroporous poly(2-hydroxyethyl methacrylate)-based monolithic cryogel functionalized with l-lysine (pHEMA-lys) and the characterization of its selective heparin adsorption. The maximum binding capacity was quantified in vitro using aqueous and serum solutions under static and dynamic conditions, and fresh human plasma under static conditions. The pHEMA-lys bound 40,500 IU and 32,500 IU heparin/g cryogel at the equilibrium in aqueous solution and 50% serum, respectively. In human plasma spiked with 100 IU/mL of heparin, the binding was still highly efficient (4330 IU/g cryogel after 30 min, i.e., 87% of the initial concentration). The cryogels showed good blood compatibility, as indicated by negligible adsorption of albumin, antithrombin III, and total protein, and may thus be suitable for extracorporeal heparin removal.

Prevention of the pulmonary vasoconstrictor effects of HBOC-201 in awake lambs by continuously breathing nitric oxide

BACKGROUND

Hemoglobin-based oxygen-carrying solutions (HBOC) provide emergency alternatives to blood transfusion to carry oxygen to tissues without the risks of disease transmission or transfusion reaction. Two primary concerns hampering the clinical acceptance of acellular HBOC are the occurrence of systemic and pulmonary vasoconstriction and the maintenance of the heme-iron in the reduced state (Fe2+). We recently demonstrated that pretreatment with inhaled nitric oxide prevents the systemic hypertension induced by HBOC-201 (polymerized bovine hemoglobin) infusion in awake mice and sheep without causing methemoglobinemia. However, the impact of HBOC-201 infusion with or without inhaled nitric oxide on pulmonary vascular tone has not yet been examined.

METHODS

The pulmonary and systemic hemodynamic effects of breathing nitric oxide both before and after the administration of HBOC-201 were determined in healthy, awake lambs.

RESULTS

Intravenous administration of HBOC-201 (12 ml/kg) induced prolonged systemic and pulmonary vasoconstriction. Pretreatment with inhaled nitric oxide (80 parts per million [ppm] for 1 h) prevented the HBOC-201--induced increase in mean arterial pressure but not the increase of pulmonary arterial pressure, systemic vascular resistance, or pulmonary vascular resistance. Pretreatment with inhaled nitric oxide (80 ppm for 1 h) followed by breathing a lower concentration of nitric oxide (5 ppm) during and after HBOC-201 infusion prevented systemic and pulmonary vasoconstriction without increasing methemoglobin levels.

CONCLUSIONS

These findings demonstrate that pretreatment with inhaled nitric oxide followed by breathing a lower concentration of the gas during and after administration of HBOC-201 may enable administration of an acellular hemoglobin substitute without vasoconstriction while preserving its oxygen-carrying capacity.

Role of Endothelin-1 and Thromboxane A2 in the Pulmonary Hypertension Induced by Heparin–Protamine Interaction in Anesthetized Dogs

This study aimed to study the role of thromboxane A2 (TXA2) and endothelin-1 (ET-1) in the pulmonary hypertension induced by interaction of heparin-protamine in anesthetized dogs. The effect of inhaled nitric oxide (NO) was also investigated in this model. Dogs were anesthetized and instrumented for acquisition of mean arterial blood pressure, mean arterial pulmonary pressure (MPAP), and pulmonary pressure gradient (PPG). Cardiac index (CI), heart rate, and index of systemic vascular resistance were also obtained. Intravenous administration of heparin (500 IU/kg) 3 minutes before protamine (10 mg/kg) caused marked pulmonary hypertension, as evaluated by the increase in MPAP and PPG. This was accompanied by systemic hypotension, CI decrease, and tachycardia. Indomethacin (10 mg/kg), dazoxiben (10 mg/kg), or tezosentan (10-mg/kg bolus plus 10-mg/kg/h infusion) significantly reduced the increase in MPAP and PPG, but had no effect on the systemic hypotension. Similar results were obtained with inhaled NO (3 ppm). Plasma TXB2 levels were markedly elevated during the pulmonary hypertension, and this was abolished in indomethacin-treated dogs. Our study shows that interaction of heparin-protamine in anesthetized dogs lead to TXA2- and ET-1-mediated pulmonary hypertension. Drugs that interfere with the synthesis of these mediators as well as inhaled NO may be of beneficial value to control this disorder.

Effect of site of venous protamine administration, previously alleged risk factors, and preoperative use of aspirin on acute protamine-induced pulmonary vasoconstriction

OBJECTIVE

To determine whether the incidence of protamine-induced pulmonary vasoconstriction (PIPV) is influenced by central venous versus peripheral venous infusion of protamine and whether aspirin ingestion within a week of surgery would decrease the incidence of PIPV.

DESIGN

Single-institution, prospective, observational, randomized trial.

SETTING

University teaching hospital.

PARTICIPANTS

One thousand four hundred ninety-seven consecutive patients undergoing cardiopulmonary bypass procedures.

INTERVENTION

Protamine neutralization of heparin by infusion pump via either central venous or peripheral venous route.

MEASUREMENTS AND MAIN RESULTS

Five previously suspected risk factors (valve surgery, prior protamine exposure, history of pulmonary hypertension, fish allergy, and vasectomy), aspirin ingestion within 7 days of surgery, and demographic information were recorded. PIPV was defined as an abrupt increase in mean PA pressure of 7 mmHg or more with associated right ventricular dysfunction as assessed by observation of the right ventricle in the field and regional wall motion abnormality by transesophageal echocardiogram and hypotension (systolic blood pressure < or = 90 mmHg). Data were collected via continuous strip chart recording. A total of 10 patients (0.6%) developed PIPV during protamine infusion. The incidents were similar with respect to the site of venous administration. Prior exposure to protamine was associated with a greater incidence of PIPV (odds ratio 6.9; p < 0.01). Other previously suspected risk factors did not achieve statistical significance. None of the 766 patients who ingested aspirin experienced PIPV as opposed to 10 of the 731 patients who did not ingest aspirin (odds ratio 0.08; p < 0.001).

CONCLUSIONS

Although the site of venous protamine administration does not influence incidence of PIPV, aspirin ingestion within 1 week of surgery may decrease it. These data also confirmed other studies suggesting that previous protamine administration predisposes to this protamine reaction.

Low molecular weight protamine (LMWP) as nontoxic heparin/low molecular weight heparin antidote (II): in vitro evaluation of efficacy and toxicity

Patients undergoing anticoagulation with heparin or low molecular weight heparin (LMWH) require a superior antidote that possesses more selective biological actions and a better safety profile than protamine. We had previously developed 2 low molecular weight protamine (LMWP) fractions (TDSP4 and TDSP5) from thermolysin-digested protamine as potential nontoxic, heparin-neutralizing agents. In this, the second article in this series, studies focused on in vitro evaluation of heparin/LMWH-neutralizing efficacy and putative toxicity. These LMWP fractions, particularly TDSP5, were effective and fully capable of neutralizing a broad spectrum of heparin-induced anticoagulant activities (ie, aPTT, anti-Xa, and anti-IIa activities). Additionally, these LMWP fractions could neutralize the activities of commercial LMWH. As assessed by the anti-Xa assay, TDSP5 was as effective as, although less potent than, protamine in reversing the activity of Mono-Embolex (molecular weight 5000-7000) and 2 other different sizes (molecular weight of 3000 and 5000 d) of LMWH preparations. Furthermore, compared with protamine, TDSP5 exhibited a much-reduced toxicity and thus an improved safety profile, as reflected by its reduced ability to activate the complement system and cross-react with the antiprotamine antibodies, which are 2 primary indices of protamine toxicity.

The effect of differing rates and injection sites on the amount of protamine delivered before detection of hemodynamic alterations in dogs

OBJECTIVES

To determine the effect of the route and rate of protamine administration on the amount of protamine that could be delivered before a hemodynamic reaction occurred in dogs.

STUDY DESIGN

Prospective randomized experimental study.

ANIMALS

Twenty adult mixed-breed dogs weighing 25.1+/-2.5 kg.

METHODS

Before vascular surgery, the dogs were heparinized to reach an activated clotting time (ACT) of 300 seconds. After completion of the vascular surgery, protamine was administered intravenously until a hemodynamic reaction was recorded. The 4 groups of dogs were given protamine at 5 mg/min (slow) or 10 mg/min (fast) via the cephalic or the jugular veins. Systemic and pulmonary arterial pressures, central venous pressure (CVP), and pulmonary arterial occlusion pressure (PAOP) were recorded before and after protamine administration. The dose of protamine was recorded when a reaction occurred, which was defined as mean arterial pressure (MAP) <60 mm Hg or mean pulmonary arterial pressure (MPAP) >20 mm Hg or more than double the baseline value.

RESULTS

Significant decreases in systolic arterial pressure (SAP), MAP, and diastolic arterial pressure (DAP) and significant increases in systolic (SPAP), mean (MPAP), and diastolic (DPAP) pulmonary arterial pressures were recorded after protamine administration. The cephalic slow group had significantly fewer protamine reactions than other groups (chi-square = 8.57, P = .03, df = 3). Significantly more protamine could be delivered from the cephalic vein (52.5+/-14.5 mg) compared with the jugular vein (37.6+/-16 mg) before a reaction occurred (P = .048).

CONCLUSION

The rate of administration did not have an effect on the amount of protamine delivered. Adverse reactions were minimized when protamine was administered via the cephalic vein at a slow rate.

CLINICAL RELEVANCE

We would recommend delivering protamine after cardiopulmonary bypass or vascular surgery through a peripheral venous route.

Low-dose protamine based on heparin-protamine titration method reduces platelet dysfunction after cardiopulmonary bypass

OBJECTIVE

The heparin-protamine titration method that uses the Hepcon hemostasis management system (Medtronic HemoTec Inc, Englewood, Colo) reduced blood loss in cardiac surgery in previous reports, but the mechanism is not fully understood. This study tests the hypothesis that reduced protamine administration preserves platelet function in human cardiac surgery.

METHODS

Platelet count, alpha-granule secretion, and aggregation to thrombin before and after cardiopulmonary bypass in human beings were evaluated. In the control group (n = 14), a fixed dose of protamine (3 mg/kg) was administered. In the titration group (n = 20), protamine doses were based on the heparin concentration measured by the Hepcon system.

RESULTS

Heparin concentrations before protamine administration were higher in the titration group (P =.0012), but protamine doses of patients in the titration group were markedly lower than those of the control group (P <.0001). During protamine infusion at a rate of 0.3 mg. kg(-1). min(-1), the percentage of granule membrane protein-140-positive platelets significantly increased in the control group compared with the titration group (18.8% +/- 8.6% vs 13.0% +/- 5.3%, P =.0188). After protamine administration, aggregation of washed platelets to thrombin recovered almost to the preoperative level in the titration group; however, it remained lower in the control group (20% +/- 20% vs 55% +/- 18%, P =.0009).

CONCLUSION

Low-dose administration of protamine, based on a heparin-protamine titration method, restores not only the blood coagulation but also the platelet responses to thrombin and attenuates platelet alpha-granule secretion during heparin neutralization. Overdose of protamine activates platelets and may predispose patients to excessive bleeding after cardiac surgery.

Involvement of fibrinogen in protamine-induced pulmonary hypertension

Protamine reversal of heparin anticoagulation occasionally results in pulmonary hypertension as well as systemic hypotension. To examine the contribution of blood components to this induction of pulmonary hypertension, we developed an isolated rat lung perfusion model and perfused heparinized plasma, heparinized serum, and Hepes (4% bovine serum albumin, 20 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, 5 mM glucose, in warm physiological saline) buffer solution with or without fibrinogen. Perfusion with heparinized plasma and Hepes buffer solution with fibrinogen caused pulmonary hypertension; perfusion with heparinized serum or Hepes buffer solution without fibrinogen did not, suggesting that fibrinogen is involved in the induction of pulmonary hypertension. We also labeled protamine with 125I and compared the amounts of protamine accumulating in the lung with different concentrations of fibrinogen. The amount of protamine trapped in the lung increased according to the concentration of fibrinogen. Fibrinogen may accelerate the reaction between pulmonary endothelial cells and protamine or protamine-heparin complexes. In the mechanism of protamine-induced pulmonary hypertension, fibrinogen, as well as heparin and protamine, may be an essential component.

The inflammatory response and extracorporeal circulation

Defining the cause of organ and tissue dysfunction associated with the use of perfusion systems will produce methods of prevention or treatment and improve patient outcome. The problem is the plethora of triggers, effectors, and mediators in this process, which can now be measured. Each new measureable compound becomes another biochemical "smoking gun" without physiological data to show any relevance to the human problem. This review critically compares and contrasts the role of certain, largely novel, initiation, amplification, and cytotoxic mechanisms in the inflammatory response of the myocardium and pulmonary systems after a period of cardiopulmonary bypass. The available evidence strongly points to the process being different for each of these tissue beds. These data suggest that ensuring normal lung and heart functions after surgery will require separate therapeutic strategies.

Enhancement of the leukocyte-endothelial cell interaction in collecting venules of skeletal muscle by protamine

OBJECTIVE

A transient but severe systemic leukopenia regularly occurs after the antagonization of heparin by protamine in patients and in animals. The aim of the present study was to investigate the site and mechanisms of white blood cell retention during this transient leukopenia by studying the leukocyte-endothelial cell interaction in skeletal muscle venules.

METHODS

Syrian golden hamsters were equipped with a dorsal skinfold chamber for intravital fluorescence microscopy and arterial and venous catheters for drug infusion, blood pressure measurement, and blood sampling. Microhemodynamic parameters and leukocyte-endothelial cell interactions were observed in one single collecting venule per animal after intravenous infusion of saline solution (control, n = 10), of protamine (n = 9), and after infusion of heparin followed by either intravenous protamine (n = 9) or intraarterial protamine (n = 9).

RESULTS

All parameters remained unchanged in the control group. Whereas venular diameters remained unchanged, protamine transiently increased arterial blood pressure and venular erythrocyte velocity in all groups. Systemic leukocyte counts and the venular leukocyte discharge concentration decreased concurrently after protamine administration by about 60% to 70% at 2 minutes while the fraction of rolling leukocytes and the number of adherent leukocytes remained unchanged. Two and one-half minutes later, systemic leukocyte counts and venular discharge concentrations normalized while the fraction of leukocytes rolling slowly along or adhering firmly to the venular endothelial wall increased considerably and similarly in all groups receiving protamine. Myeloperoxidase (an indicator of polymorphonuclear leukocytes) determination in 20 separate hamsters 2 minutes after protamine infusion revealed increased myeloperoxidase activity exclusively in the lungs.

CONCLUSION

The response of leukocytes to protamine infusion with or without prior heparinization is biphasic: initial retention of leukocytes in the lungs is followed by enhanced leukocyte-endothelial cell interaction in the systemic circulation.

Differential effects of novel protamine variants on myocyte contractile function with left ventricular failure

BACKGROUND

Protamine administration can cause left ventricular (LV) dysfunction, which may have clinical significance in the setting of congestive heart failure (CHF). Protamine variants have recently been constructed with heparin reversal capacity similar to protamine. The purpose of this study was to examine the potential differential effects of these protamine variants on isolated myocyte contractile function in normal myocytes and in myocytes after the development of CHF.

METHODS

Contractile function was measured by means of computer-aided videomicroscopy in myocytes from five normal pigs and five pigs with CHF induced by rapid pacing (240 beats/min for 3 weeks). Myocyte contractility was examined in the presence of 40 micrograms/ml native protamine or one of three protamine variants: (1) reduced charge (+18) and lysine substituted for arginine; (2) lysine-substituted variant with glutamic acid substituted for the initial proline; or (3) arginine-rich peptide with a terminal arginine-glycine-aspartic acid (RGD) amino acid sequence.

RESULTS

In the presence of native protamine, myocyte percent shortening fell from baseline in both the normal (2.86 +/- 0.15 versus 4.58 +/- 0.08, p < 0.05) and the CHF groups (1.01 +/- 0.06 versus 2.07 +/- 0.05, p < 0.05). With both of the lysine-substituted protamine variants, percent shortening fell from baseline in the normal group (3.42 +/- 0.20 for arginine and 3.74 +/- 0.20 for glutamic acid versus 4.58 +/- 0.08, p < 0.05), and was unchanged in the CHF group (1.94 +/- 0.13 versus 2.07 +/- 0.05, p = 0.34 for arginine; and 1.96 +/- 0.10 versus 2.07 +/- 0.05, p = 0.31, for glutamic acid). However, with the arginine/RGD variant, percent shortening fell from baseline in both the normal (2.86 +/- 0.23 versus 4.58 +/- 0.08, p < 0.05) and the CHF groups (1.32 +/- 0.10 versus 2.07 +/- 0.05, p < 0.05).

CONCLUSIONS

Specific changes in the primary and secondary structures of protamine had different effects on myocyte contractile function. Furthermore, the negative effects of lysine-substituted protamine variants on myocyte contractility were less pronounced in both CHF and normal myocytes. Thus protamine variants may be of clinical use, particularly in the setting of preexisting LV dysfunction.

Reversible inhibition by protamine of human synovial and rabbit platelet secretory phospholipase A2

We investigated the effects of protamine on the release and the activity of 14 kDa type II phospholipase A2 (sPLA2). Protamine blocks both release and activity of sPLA2 from thrombin-stimulated platelets in a concentration-dependent manner. Heparin, an anionic sulfate polysaccharide which has a high affinity for this enzyme, has no inhibitory effect on sPLA2 by itself but it is able to reverse the inhibitory effect of protamine. The liberation by thrombin of platelet factor 4, an alpha-granule constituent, unlike to that of ATP stored in dense bodies, was suppressed by protamine. Platelet aggregation, determined in parallel, was not affected by protamine. Also, protamine did not inhibit platelet arachidonic acid liberation, which is mainly produced by cytosolic PLA2. The non-proteinaceous polycationic hexadimethrine and acidic protein casein failed to inhibit platelet sPLA2 activity. By contrast, the basic polypeptides poly(L-arginine) and poly(L-lysine) potently inhibited sPLA2 activity, indicating the important role of basic amino acids in the inhibitory effect evoked by protamine. Activities of the human recombinant sPLA2 and the unpurified synovial enzyme of patients with rheumatoid arthritis were also inhibited by the same range of protamine, poly(L-arginine) and poly(L-lysine) concentrations. Our results demonstrate that protamine, unlike heparin, blocks platelet sPLA2 release and exerts a reversible inhibitory effect on its activity, probably through the interaction of basic amino acids with the enzyme.

Biochemical and cellular effects of heparin-protamine injection in rabbits are partially inhibited by a PAF-acether receptor antagonist

The origin of the thrombocytopenia and leucopenia induced by protamine-heparin complexes is unknown. We studied the biochemical and cellular effects of protamine (6 mg x kg-1, i.v.) injected after heparin (5 mg x kg-1, i.v.) in New Zealand rabbits. After protamine injection (0.5 min) increases in blood platelet-activating factor (PAF-acether, PAF) (27.6 +/- 27.6 to 148.2 +/- 48.9 pg x ml-1, P < 0.05), thrombocytopenia (403 +/- 64 to 166 +/- 13 cells x 10(-3) x mm-3, P < 0.05) and leucopenia (7650 +/- 930 to 4300 +/- 668 cells x mm-3, P < 0.05) were noted. Plasma thromboxane B2 increased at 1 min (125.6 +/- 24.4 to 879.7 +/- 141.0 pg x ml-1, P < 0.01). Protamine alone induced no change. Indomethacin (3 mg x kg-1, i.v.) did not counteract the effects of heparin-protamine. Pretreatment with the PAF receptor antagonist BN 52021 [9H1, 7a-(epoxymethano)-1 H,6aH-cyclopenta[c]furo[2,3-b]furo-[3',2',3,4]cyclopenta[1,2-d]fur an-5,9, 12(4H)trione,3-tert-butylhexahydro-4,7b,11 hydroxy-8 methyl] alone (3 mg x kg-1, i.v.) delayed thrombocytopenia and reduced plasma thromboxane B2 concentration but did not modify leucopenia. Thus thrombocytopenia and thromboxane B2 release triggered by heparin-protamine may be potentiated by the release of PAF.

The human inflammatory response

Inflammation is a protective response of vascularized tissue normally elicited toward nonself-determinants or tissue injury. Inflammation functions as part of normal host surveillance mechanisms to destroy or quarantine both harmful agents and damaged tissue. Most forms of inflammation are exaggerated out of proportion to the stimulus, because humoral amplification systems recruit additional components of the immune system initiating the production of proinflammatory mediators, including cytokines synthesized by activated macrophages. These act as secondary messengers to induce synthesis and expression of specific adhesion molecules on endothelial cells and white cells. Polymorphonuclear leukocytes play a central role in the acute inflammatory response. Anaphylaxis, an immediate hypersensitivity reaction to substances administered in the perioperative period, serves as a useful model for some of the problems of acute inflammation because there are important interrelationships with the cardiovascular system, endothelium, and coagulation. Mast cells and basophils produce the acute inflammation associated with anaphylaxis mediated by immunoglobulin E (IgE) antibodies, whereas the immunoglobulin G (IgG)-antigen interaction activates the complement cascade to generate anaphylatoxins, specifically C5a. Activation of white cells causes release of proteolytic enzymes, production of oxygen-derived free radicals, and the synthesis of a variety of lipid mediators. Protamine sulfate is one of the most common causes of life-threatening anaphylactic reactions during cardiac surgery. Differing responses occur, dependent on the presence of either IgE or IgG antibodies with the activation of the mast cell or the complement system, respectively. The many different amplifying pathways that can be recruited during anaphylaxis and the array of mediators involved are important when therapeutic intervention is considered. The challenge for the future will be to identify a pharmacologic agent that will arrest the inflammatory cascade and thus prevent further amplification and resultant host injury.

Restoration of the normal coagulation process: advances in therapies to antagonize heparin

A number of naturally occurring anticoagulants exist that preserve normal blood fluidity and limit blood clot formation to vascular injury sites, thus acting as regulators of hemostasis. The protein C/protein S pathway is one system that acts to modulate thrombin formation. The activation of protein C by thrombin is accelerated more than 1,000-fold at the endothelial surface by thrombomodulin localized on the endothelial cell. Activated protein C then binds to its co-factor, protein S, and the protein C/protein S complex exerts its antithrombotic function by inactivating the coagulation factors Va and VIIIa. Patients deficient in protein C and protein S may be particularly vulnerable to thrombotic events after cardiac surgery. In addition, several studies suggest that reductions in protein C and protein S concentrations, as well as thrombomodulin, occur during cardiopulmonary bypass (CPB). The possibility of a low anticoagulant potential when heparinization is reversed may be an important factor in the subsequent morbidity associated with thrombotic complications. Aprotinin is a serine protease inhibitor that in vitro binds competitively with the serine protease-activated protein C. However, aprotinin in the clinical setting has not been reported to alter levels of protein C in patients undergoing CPB. Reversal of the heparinization needed for CPB is almost universally performed with protamine. However, protamine has many deleterious effects. Recombinant platelet factor 4 (rPF4) has been proposed as an alternative to protamine. We investigated the effective heparin neutralization dose of rPF4 vs. the standard agent protamine in human blood activated through exposure to the CPB circuit. Activated clotting time (ACT) measurements suggested a 2:1 (w/w) reversal ratio for rPF4 and protamine. The first human open-label phase 1 trial of rPF4 reported no serious side effects and no important hemodynamic effects. Doses of 2.5 and 5.0 mg/kg were uniformly effective in reversing the anticoagulant effect of heparin and reducing the ACT to <200 s by 5 min after administration. Repeated monitoring of the ACT did not detect a rebound effect of heparin.

Protamine-induced pulmonary venoconstriction in heparinized pigs

Reversal of heparin anticoagulation with protamine may be associated with acute pulmonary vasoconstriction. The specific site of pulmonary vasoconstriction has not been determined. This study was designed to determine the site of protamine-induced pulmonary vasoconstriction and the role of nitric oxide (NO) after protamine injection. Pigs were anesthetized and instrumented with catheters for monitoring pulmonary arterial, systemic arterial, and central venous pressures. Pulmonary capillary pressure was estimated using the arterial occlusion concept, while left atrial pressure was estimated from the equilibrium wedge pressure. Hemodynamic measurements were made during baseline, before and after heparin (200 U/kg), at peak pressure response after protamine injection (2 mg/kg), and 10 and 30 min thereafter. In the control group, pulmonary vascular resistance (PVR) values during baseline and after heparin were identical (2.7 +/- 0.4 mm Hg.L-1.min-1). At peak protamine response (1-2 min) PVR increased to 8.0 +/- 1.6, but returned to baseline value after 10 min (2.8 +/- 0.3) and remained stable for 30 min (2.2 +/- 0.3). The increase in PVR after protamine was primarily due to an increase in venous resistance from 1.0 +/- 0.2 to 4.9 +/- 1.4 mm Hg.L-1.min-1, and a much smaller increase in arterial resistance from 1.7 +/- 0.3 to 3.4 +/- 0.6 mm Hg.L-1.min-1. A second group was treated with nitrow-L-arginine (LNA, 20 mg/kg) to inhibit NO release, and then heparin and protamine were administered as in the first group. Heparin had no effect on pressures, but protamine increased PVR by the same magnitude as in Group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Heparin-enhanced plasma phospholipase A2 activity and prostacyclin synthesis in patients undergoing cardiac surgery

Although eicosanoid production contributes to physiological and pathophysiological consequences of cardiopulmonary bypass (CPB), the mechanisms accounting for the enhanced eicosanoid production have not been defined. Plasma phospholipase A2 (PLA2) activity, 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), and thromboxane B2 (TXB2) levels were measured at various times during cardiac surgery. Plasma PLA2 activity increased after systemic heparinization, before CPB. This was highly correlated with concurrent increases in plasma 6-keto-PGF1 alpha, TXB2 concentrations did not increase with heparin administration but did increase significantly after initiation of CPB. High plasma PLA2 activity, 6-keto-PGF1 alpha, and TXB2 concentrations were measured throughout the CPB period. Protamine, administered to neutralize the heparin, caused an acute reduction of both plasma PLA2 activity and plasma 6-keto-PGF1 alpha, but no change in plasma TXB2 concentrations. Thus the ratio of TXB2 to 6-keto-PGF1 alpha increased significantly after protamine administration. Enhanced plasma PLA2 activity was also measured in patients with lower doses of heparin used clinically for nonsurgical applications. Human plasma PLA2 was identified as group II PLA2 by its sensitivity to deoxycholate and dithiothreitol, its substrate specificity, and its elution characteristics on heparin affinity chromatography. Heparin addition to PMNs in vitro resulted in dose-dependent increases in cellular PLA2 activity and release of PLA2. The PLA2 released from the PMN had characteristics similar to those of post-heparin plasma PLA2. In conclusion, plasma PLA2 activity and 6-keto-PGF1 alpha concentrations are markedly enhanced with systemic heparinization. Part of the anticoagulant and vasodilating effects of heparin may be due to increased plasma prostacyclin (PGI2) levels. In addition the pulmonary vasoconstriction sometimes associated with protamine infusion during cardiac surgery might be due to decreased plasma PLA2 activity, with an associated increased TXB2/6-keto-PGF1 alpha ratio.

Thromboxane A2 receptor-specific antagonism in hypothermic cardiopulmonary bypass

Using a thromboxane A2 receptor-specific antagonist, SQ 30,741, this study was undertaken to define the role of thromboxane A2 in postischemic myocardial reperfusion injury and in the heparin-protamine reaction. Eighteen heparinized (300 units/kg) sheep were placed on cardiopulmonary bypass (CPB) after complete instrumentation, cooled to 28 degrees C, and had their aortas crossclamped for 1 hour. They were then rewarmed to 36 degrees C and weaned from CPB without inotropic support. Control sheep (n = 6) received a saline infusion throughout the procedure. Bolus animals (n = 6) received 5 mg/kg of SQ 30,741 at 5 minutes after discontinuation of CPB and before protamine sulfate administration. Infusion animals (n = 6) received an SQ 30,741 bolus of 5 mg/kg followed by a continuous infusion of 5 mg.kg-1 hr-1 of SQ 30,741 initiated before CPB. All animals received 5 mg/kg of protamine sulfate over a 15-second period 15 minutes after being weaned from CPB. Control animals exhibited significantly decreased global myocardial function after the 1-hour ischemic interval. Further significant functional decline and increase in pulmonary pressure occurred after protamine sulfate administration. Bolus animals experienced a similar postischemic injury, but had no further decrease in function following protamine infusion. Infusion animals had significantly improved global myocardial function after bypass compared with both other groups and were also protected from the deleterious effects of protamine sulfate administration.(ABSTRACT TRUNCATED AT 250 WORDS)

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)

The beneficial effects of aminophylline administration on heparin reversal with protamine

The aim of this study was to demonstrate the beneficial effects of aminophylline on protamine cardiotoxicity. Thirty-four patients were examined, 17 of whom received aminophylline 3 mg/kg before protamine administration, being the study group, while the other 17, being the control group, did not. All cardiac output and biochemical measurements were evaluated 5 min following protamine administration. The cAMP level was 43.4 +/- 3.51 pmol/ml in the study group and 18.7 +/- 2.98 in the control group (P < 0.0001) before protamine administration, while the oxygen extraction rate decreased from 49% to 44 +/- 2% in the control group, and from 51.2% to 47 +/- 3% in the study group (P < 0.03). The N-acetyl glucosaminidase value was 16.9 +/- 13.9 pmol/ml in the study group and 27.8 +/- 1.47 pmol/ml in the control group (P < 0.01), and myocardial lactate extraction was -0.20 +/- 0.03 in the control group and -0.07 +/- 0.07 in the study group (P < 0.001). The left ventricular stroke work index was 28.6 +/- 3.14 gm/m2 in the control group and 37 +/- 6.77 gm/m2 in the study group (P < 0.002). The findings of this study led us to conclude that the adverse effects of heparin neutralization using protamine can be relieved by aminophylline.

Catastrophic vasoconstriction after protamine reversal of heparin anticoagulation in the goat

Catastrophic pulmonary vasoconstriction after protamine reversal of heparin anticoagulation was observed frequently in goats that underwent centrifugal biventricular bypass pump implant. Care should be taken when protamine is used to reverse heparin anticoagulation in goats.

In vitro hematological testing of rotary blood pumps: remarks on standardization and data interpretation

Pump test procedures using blood will have to meet several standards not only to obtain reliable results in vitro but also to allow comparison of results of different investigators. This article reviews some of the issues that should be considered in pump testing, especially referring to the discussions held at the International Workshops on Rotary Blood Pumps in 1988 and 1991. The test loop itself should meet some requirements such as constant physiological temperature, standardized circulating volume, control of pressure and flow, and exact definition of the blood-contacting surface. Specifications have to be made concerning the test fluid blood, including sampling technique, anticoagulation, blood gases, pH, and glucose level. Only fresh blood should be used. Heparin is recommended for anticoagulation because it will be used also in vivo. Different procedures for cleaning and rinsing of plastic materials for reuse are mentioned. Bacterial overgrowth, which can lead to extreme oxygen consumption and acidosis, may be avoided through addition of antibiotics (e.g., gentamicin). To be able to compare data of the different working groups, a new modified index of hemolysis (MIH) has been defined.

Activation of leukocytes with complement C5a is associated with prostanoid-dependent constriction of large arteries in atherosclerotic monkeys in vivo

Activated leukocytes release a variety of substances which have been shown in vitro to modulate vascular tone. The chemotactic peptide complement C5a is a physiological activator of leukocytes. We injected human recombinant complement C5a (10 and 100 micrograms) into the blood-perfused hind limb of normal and atherosclerotic cynomolgus monkeys and examined vascular responses. In both normal and atherosclerotic monkeys, the high dose of C5a produced about 65% decrease in leukocyte cell count in venous blood drainage from the hind limb. Injection of C5a produced a pronounced increase in resistance of large arteries (segment from iliac artery to dorsal pedal artery) in atherosclerotic, but not in normal monkeys. The constrictor effect of C5a in atherosclerotic monkeys was abolished by the thromboxane A2 receptor antagonist SQ 29,548 (2 mg/kg i.v.). The platelet-activating factor antagonist WEB 2086 (5 mg/kg, i.v.) did not alter vascular responses to C5a. We conclude that activation of leukocytes produces constriction of large arteries in atherosclerotic, but not normal, monkeys in vivo. This response may be mediated in part by release of thromboxane A2.

Mechanism of hypotension following rapid infusion of protamine sulfate in anesthetized dogs

Protamine sulfate (PS), used to neutralize the anticoagulant effect of heparin, is often associated with systemic hypotension. Whether this hypotension is secondary to a depression of myocardial function is not clear. The present study tested the hypothesis that systemic hypotension was accompanied by a depression in myocardial function and examined the possible role of histamine in mediating the cardiovascular response to PS. Seven conditioned dogs were chronically instrumented with pressure and ultrasonic dimension transducers. Studies were conducted under halothane anesthesia 7 to 10 days after instrumentation. Cardiac contractility was assessed using the slope, Ees, of the linear regression of the left ventricular end-systolic pressure-diameter relationship. Intravenous infusion of PS, 5 mg/kg, when given in periods of less than 30 seconds, decreased systemic arterial pressure by 45% (from 101 +/- to 54 +/- 5 mm Hg) without change in heart rate. Cardiac output decreased by 22% from control and the slope Ees decreased by 37% (from 14.5 +/- 1.2 to 8.7 +/- 1.4 mm Hg/mm). Systemic vascular resistance decreased by 34% (from 2581 +/- 121 to 1712 +/- 200 dyne.s.cm-5). The cardiovascular depression caused by PS was transient and could not be reproduced by a repeated dose given within a 60-minute period. Antagonists of histamine (diphenhydramine and cimetidine) could not attenuate the PS-induced cardiovascular depression. This depression was independent of preheparinization and did not occur when PS was infused slowly over a 2-minute period. The data clearly demonstrate negative inotropic and vasodilator effects of PS following rapid administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous injection of Albunex microspheres causes thromboxane mediated pulmonary hypertension in pigs, but not in monkeys or rabbits

Intravenous injection of the ultrasound contrast agent Albunex (manufactured by Nycomed AS, Oslo, Norway; 400 million air-filled albumin microspheres per ml, mean diameter 4 +/- 1 microns) caused a dose-dependent increase of mean pulmonary arterial pressure in nine pigs. The highest dose (0.014 +/- 0.002 ml kg-1) increased mean pulmonary arterial pressure from 17 +/- 1 mmHg to 42 +/- 3 mmHg and decreased mean systemic arterial pressure from 111 +/- 9 to 93 +/- 12 mmHg. The pressure responses began 22 +/- 1 s after particle injection, and reached maximum after 51 +/- 3 s. No changes in mean pulmonary arterial pressure or mean systemic arterial pressure were observed after Albunex injections during treatment with indomethacin (10 mg kg-1 + 5 mg kg-1 h-1 i.v., n = 6) or the thromboxane A2 receptor antagonist HN-11500 (10 mg kg-1 + 5 mg kg-1 h-1 i.v., n = 3). No Doppler enhancement could be detected in a carotid artery following injection of 0.12 ml kg-1 Albunex during indomethacin treatment. In five rabbits, Albunex caused Doppler enhancement in a carotid artery, and 0.48 ml kg-1 did not affect mean pulmonary arterial pressure or other haemodynamic parameters in five rabbits or in three cynomolgus monkeys. The pressure response in pigs may be explained by release of thromboxane A2 from the pulmonary intravascular macrophages during phagocytosis of the microspheres. This response to Albunex was totally absent in rabbits and monkeys.

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.

RETRACTED: Does the preparation of heparin influence anticoagulation during cardiopulmonary bypass?

Various preparations of heparin from different manufacturers are commercially available. The influence of bovine lung heparin (BLH) and porcine mucosal heparin (PMH) on anticoagulation and heparin plasma concentration was investigated in four groups of 10 patients undergoing elective aortocoronary bypass grafting either after single dose or repetitive dose (after 60 minutes) of one of these heparin preparations. Heparin plasma concentration increased significantly after injection of heparin (BLH: minimum, 1.67 U/mL; maximum, 2.10 U/mL; PMH: minimum, 1.69 U/mL; maximum, 2.15 U/mL). Sixty minutes after the initial dose, heparin plasma levels were higher in the patients who received PMH. Supplemental heparin doses 60 minutes after the loading dose increased plasma heparin concentration only with porcine mucosal heparin. Elimination of heparin in the urine was not different among the groups. Fibrinogen and antithrombin III concentrations, as well as activated clotting time (ACT; always greater than 400 seconds) and partial thromboplastin time (PTT; always greater than 300 seconds), did not differ among the groups, indicating effective anticoagulation during the bypass period with both types of heparin. It can be concluded that sufficient anticoagulation can be achieved with either kind of heparin. PMH seems to be longer acting and a repeat dose in these patients seems to be necessary only if cardiopulmonary bypass lasts longer than 90 minutes.

Oxygen radicals and lung injury

This article describes the formation of oxygen radicals and their biological effects, especially in relation to lung injury. Various recent experimental data are reviewed. The relationships between hydrostatic effects and permeability effects in producing injury and edema are stressed. Means of prevention and problems related to extrapolation to clinical situations are focused.

Increased prostacyclin and adverse hemodynamic responses to protamine sulfate in an experimental canine model

Prostanoid activity was correlated with the hemodynamic effects of protamine sulfate reversal of heparin in 24 dogs undergoing three different pretreatment regimens: Group I (n = 8) received saline, Group II (n = 8) received the thromboxane synthetase inhibitor U63,557A (30 mg/kg), and Group III (n = 8) received indomethacin (10 mg/kg). Pretreatment substances were administered as 5-min intravenous infusions 20 min before anticoagulation with intravenous heparin (150 IU/kg). Protamine sulfate (1.5 mg/kg) was subsequently given as a 10-sec intravenous infusion 30 min after heparin had been administered. Hemodynamic data, as well as prostacyclin (PGI2) and thromboxane (TxA2) activity in aortic, venous, and pulmonary artery blood samples, were assessed over a 30-min time period following protamine administration. Group III indomethacin pretreatment provided the most protection from declines in blood pressure, heart rate, cardiac output, venous oxygen saturation, oxygen consumption, and elevations in pulmonary pressures and was accompanied with actual declines in PGI2. Group II U63,557A pretreatment was associated with the most severe hemodynamic changes and the greatest increase in PGI2 (+576%). Elevated PGI2 correlated with hypotension at 1 and 3 min (P less than 0.01), as well as pulmonary artery pressure declines at all times following protamine reversal. TxA2 changes did not correlate with hemodynamic changes. Protamine's adverse hemodynamic responses were attenuated with cyclooxygenase blockade by indomethacin, but were worsened with selective TxA2 blockade with U63,557A. Excess arachadonic acid precursors in the latter setting may increase PGI2 production. This study, for the first time, raises the possibility that PGI2 contributes to the adverse effects accompanying protamine reversal of heparin anticoagulation.

Dimethylthiourea inhibition of B16 melanoma growth and induction of phenotypic alterations; relationship to ATP levels

1,3 Dimethylthiourea (DMTU) has previously been shown by us to inhibit the growth of melanoma cells and to induce phenotypic alterations in these cells, including ultrastructural alterations of mitochondria. These findings raised the possibility that impaired mitochondrial function might be involved in mediating the effect of DMTU on cell growth and phenotypic expression. The present study indicates that DMTU as well as another growth inhibitory methylurea derivative, tetramethylurea (TMU) significantly decrease ATP content in the B16 melanoma cell line. 1,3 Dimethylurea (1,3DMU) and 1,1 dimethylurea (1,1DMU) which are poor growth inhibitors, do not reduce ATP content significantly. Altered energy metabolism in the DMTU-treated cells is reflected by inhibition of the activity of cytochrome c oxidase and by increased lactate levels. A cell line selected for resistance to growth inhibition by DMTU was shown to be completely resistant to induction of phenotypic alterations by DMTU. These cells possess high lactate levels, high ATP content and a somewhat decreased Na/K ATPase activity as compared to wild type B16 F10 cells. 1,3 DMTU treatment of the resistant cells leads to a decrease in the activity of the mitochondrial enzyme cytochrome c oxidase, similar to its effect on the wild type B16 F10 cells. DMTU also reduces ATP content moderately in the resistant cells. However, the levels of ATP do not decrease beyond those found in untreated B16 F10 wild type cells. Taken together the results suggest that decreased ATP content might be involved, at least partially, in mediating the effects of DMTU on B16 melanoma cell growth and phenotypic expression.

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.

Reversal of protamine-induced catastrophic pulmonary vasoconstriction by prostaglandin E1

A case of catastrophic pulmonary vasoconstriction occurring after cardiopulmonary bypass after protamine reversal of heparin treated successfully with intravenous prostaglandin E1 is reported. Systemic hypotension was counteracted by epinephrine given through the left atrium. Protamine-heparin reactions are reviewed and a pathophysiological mechanism for the beneficial effect seen with prostaglandin E1 is proposed.

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.