Protamine-induced circulatory changes

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.

Protamine (heparin)-induced thrombocytopenia: a review of the serological and clinical features associated with anti-protamine/heparin antibodies

Protamine is widely used in medicine as a rapidly-acting antidote to heparin, particularly for reversing heparin anticoagulation after cardiac surgery. Protamine is also used as a stabilizing additive to certain preparations of insulin. Recent reports demonstrate that protamine and heparin form multimolecular complexes that result in high rates of immunization in post-cardiac surgery patients, particularly of immunoglobulin G (IgG) class antibodies; a subset of these anti-protamine/heparin IgG antibodies activates platelets through their FcγIIA (IgG) receptors. Although the clinical consequences of anti-protamine/heparin antibodies that are newly generated after cardiac surgery are unknown, there is evidence that platelet-activating anti-protamine/heparin antibodies already present at the time of cardiac surgery might occasionally explain more severe thrombocytopenia with delayed platelet count recovery, as well as thromboembolic complications, in the post-cardiac surgery setting. Triggers for such antibodies remain poorly-defined, but could include preoperative administration of heparin to diabetic patients receiving protamine-insulin as well as recent previous cardiac surgery. Anti-protamine/heparin antibodies have several features in common with anti-platelet factor 4 (PF4) PF4/heparin antibodies implicated in heparin-induced thrombocytopenia (HIT), including immunization by heparin-containing multimolecular complexes, predominant IgG class, pathological platelet-activating properties, relatively rapid IgG formation without IgM precedence, and antibody transience. Despite these similarities, the risk of anti-protamine/heparin antibody-mediated complications seems to affect the early post-cardiac surgery period, whereas HIT usually occurs at least 5 days following cardiac surgery. Clinicians need to become aware of this recently recognized immunohematological disorder, and research is needed to identify triggers of immunization, improve detection of pathological antibodies and identify patients at risk of this complication.

Effects of Prostacyclin on Heparin Reversal with Protamine

This study was planned to show the beneficial effects of prostacyclin (PGI2) utilization on adverse effects of protamine. PGI2 was administered at a rate of 5 ng/kg/min. Twenty patients entered this study. Half of them received PGI2 whereas the others did not.

Right ventricular end-diastolic volume index and right ventricular stroke work index were 72 mL/m2 and 2.2 g.m/m2, respectively, after patients were weaned off the bypass and 79 and 1.5, respectively, at five minutes after pro tamine administration in the control group; these values were 88 and 3.2, re spectively, and 86 and 3, respectively, in the PGI2 group. Left ventricular stroke work index (g.m/m2) was 27.9 in the control group and 36.7 in the PGI2 group (p < 0.05) after protamine administration.

Thromboxane B2 levels (pmoL/mL) in coronary sinus (CS) blood were 251 in the control group and 90 in the PGI2 group at five minutes after protamine administration (p < 0.05). Myocardial blood flow was 174 mL in the control group and 245 mL in the PGI2 group at five minutes after protamine adminis tration (p < 0.05). Cyclic adenosine monophosphate (cAMP) and cyclic guano- sine monophosphate (cGMP) levels in CS blood were 17 pmoL/mL and 2.1 pmoL/mL, respectively, in the control group and 36 and 0.3, respectively, in the PGI2 group at five minutes after protamine administration. Leukotriene B4 level was 129 and 57 pmoL/mL in the control and PGI2 groups, respectively (at the same time as the cAMP measurement) (p < 0.05).

From the results of this study the authors conclude that adverse effects of heparin reversal with protamine can be reduced with the use of PGI2.

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.

Protamine Administration Via the Ascending Aorta May Prevent Cardiopulmonary Instability

OBJECTIVE

The method of protamine administration may influence adverse reactions. The authors investigated the effects of 3 different methods of protamine administration on cardiopulmonary function.

DESIGN

Prospective, randomized clinical study.

SETTING

Single university hospital.

PARTICIPANTS

Human volunteer patients.

INTERVENTIONS

Ninety-five patients undergoing cardiac surgery were randomized prospectively into 3 groups. Group central vein control (CVC) and group central vein (CV) received protamine via a central vein over 10 minutes and 2 minutes, respectively. Group ascending aorta (AA) received protamine via the ascending aorta over 2 minutes. Hemodynamic parameters were assessed at 7 intraoperative time points, and pulmonary parameters were assessed at 4 intraoperative time points.

MEASUREMENTS AND MAIN RESULTS

The groups were similar regarding preoperative demographics, intraoperative care, and baseline cardiopulmonary function. However, both the CVC and CV groups exhibited decreased blood pressure and impaired pulmonary oxygenation after protamine administration; these changes were not observed in the AA group. Within-group changes in mean arterial blood pressure after protamine administration were significant in the AA group (mean increase 6.5 mmHg; p = 0.01) but not in the CVC (mean decrease 3.1 mmHg, p = 0.13) or CV (mean decrease 4.3 mmHg, p = 0.14) groups. Within-group changes in arterial oxygenation after protamine administration were significant in the CVC (mean decrease 85 mmHg; p<0.001) and CV (mean decrease 47 mmHg; p = 0.009) groups but not in the AA group (mean decrease 8 mmHg; p = 0.82).

CONCLUSIONS

The results indicated that administration of protamine via the ascending aorta may be the preferred route. The potential ability of administering protamine via the ascending aorta to prevent cardiopulmonary instability in patients undergoing cardiac surgery deserves further clinical investigation.

Bioactive substances from marine fishes, shrimps, and algae and their functions: present and future

Marine fishes, shrimps, and algae have many important bioactive substances, such as peptides, unsaturated fatty acids, polysaccharides, trace elements, and natural pigments. The introduction of these substances contributes to a significant improvement in developing them in final processed products. In fact, the knowledge of these bioactive substances has experienced a rapid increase in the past 20 years and prompted the relevant technological revolution with a decisive contribution to the final application. The purpose of this review was to introduce critically and comprehensively the present knowledge of these bioactive substances and pointed out their future developmental situation.

High incidence of antibodies to protamine and protamine/heparin complexes in patients undergoing cardiopulmonary bypass

Protamine is routinely used to reverse heparin anticoagulation during cardiopulmonary bypass (CPB). Heparin interacts with protamine to form ultralarge complexes that are immunogenic in mice. We hypothesized that patients exposed to protamine and heparin during CPB will develop antibodies (Abs) to protamine/heparin (PRT/H) complexes that are capable of platelet activation. Specimens from a recently completed prospective clinical trial (HIT [for heparin-induced thrombocytopenia] 5801 study; n = 500) of CPB patients were examined for PRT/H Abs at baseline, at time of hospital discharge (between days 3 through 7), and 30 days after CPB. PRT/H antibody features were characterized and correlated with adverse cardiovascular outcomes. We found a high incidence of PRT/H antibody formation (29%) in patients undergoing cardiac surgery. PRT/H Abs were of high titer (mean titer 1:14,744), showed heparin-dependent binding, and activated platelets in the presence of protamine. PRT/H Abs showed no cross-reactivity to platelet factor 4/heparin complexes, but were cross-reactive with protamine-containing insulin preparations. In the absence of circulating antigen at day 30, there were no complications of thrombocytopenia, thrombotic events, or long-term cardiovascular events. These studies show that Abs to PRT/H occur commonly after cardiac bypass surgery, share a number of serologic features with HIT Abs, including platelet activation, and may pose health risks to patients requiring drug reexposure.

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.

Catastrophic cardiovascular adverse reactions to protamine are nitric oxide/cyclic guanosine monophosphate dependent and endothelium mediated: should methylene blue be the treatment of choice?

Clinical and experimental observations prove that heparin-neutralizing doses of protamine increase pulmonary artery pressures and decrease systemic BP. Protamine also increases myocardial oxygen consumption, cardiac output, and heart rate, and decreases systemic vascular resistance. These cardiovascular effects have clinical consequences that have justified studies in this area. Protamine adverse reactions usually have three different categories: systemic hypotension, anaphylactoid reactions, and catastrophic pulmonary vasoconstriction. The precise mechanism that explains protamine-mediated systemic hypotension is unknown. Four experimental protocols performed at Mayo Clinic, Rochester, MN, studied the intrinsic mechanism of protamine vasodilation. The first study reported in vitro systemic and coronary vasodilation after protamine infusion. The second in vitro study suggested that the pulmonary circulation is extensively involved in the protamine-mediated effects on endothelial function. The third study, carried out in anesthetized dogs, reported the methylene blue and nitric oxide synthase blockers neutralization of the protamine vasodilatatory effects. The fourth study suggested that protamine also causes endothelium-dependent vasodilation in heart microvessels and conductance arteries by different mechanisms including hyperpolarization. Reviewing these experimental results and our clinical experience, we suggest methylene blue as a novel approach to prevent and treat hemodynamic complications caused by the use of protamine after cardiopulmonary bypass. In the absence of prospective clinical trials, a growing body of cumulative clinical evidence suggests that methylene blue may be strongly considered as a therapeutic approach in the treatment of distributive shock.

Hemostatic effects of low-dose protamine following cardiopulmonary bypass

Twenty-eight patients undergoing cardiac surgery were prospectively studied and were assigned to two groups. The patients received 0.8- (Group L) or 2.0-fold (Group H) dose of protamine for the neutralization after cardiopulmonary bypass (CPB) which was determined by Hepcon HMS(R) assay system in which the reagent chamber containing the concentration of protamine that completely neutralized the heparin had the shortest clotting time. Mean dose of protamine was 1.60 +/- 0.50 mg kg(-1) in Group L, and 3.56 +/- 1.48 mg kg(-1), respectively. Activated clotting times (ACT) were comparable between the two groups through this study period. In Group H, platelet counts significantly decreased to 69% of that before protamine administration, and plasma platelet factor 4 level significantly increased to approximate 2-fold of that before protamine administration just after protamine administration, respectively. However, these phenomena were not observed in Group L. In addition, these hemostatic changes occurred transiently just after protamine administration. We conclude that the low-dose protamine may prevent transient platelet depletion following CPB. Low-dose protamine can neutralize anticoagulation effect of heparin sufficiently and may mitigate protamine-induced platelet dysfunction.

Experimental inhibition of protamine cardiotoxicity by prostacyclin

Twelve animals (26+/-5 kg) were subjected to the study. In this experimental study, the authors used prostacyclin to inhibit the toxic metabolite release during protamine administration. Animals were divided into two equal groups. Six animals received prostacyclin (the prostacyclin group), and the other six animals did not receive any additional treatment (the control group). All cardiac output and biochemical measurements were evaluated at baseline; before cardiopulmonary bypass; and at 5, 30, and 60 minutes after protamine administration. The measured cardiac index showed that the hearts treated with prostacyclin had satisfactory preservation of left ventricular function. Metabolic and biochemical data showed that the tumor necrosis factor level was raised significantly in the control group (20.75+/-2.2 in the control group and 13.75+/-2.5 pg/mL in the prostacyclin group). Also, E and P selectin levels were elevated in the control group, but this change was less marked in the prostacyclin group. In addition, the intracellular adhesion molecule-1 (ICAM-1) level was significantly higher in the control group than in the prostacyclin group (9.26+/-2.13 in the control group and 5.13+/-1.66 ng/mL in the prostacyclin group). The authors observed that prostacyclin inhibited the toxic mediator release during heparin reversal with protamine. This inhibition is one way of protecting the myocardium reserves from protamine cardiotoxicity.

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.

Protamine induces elevation of cytosolic free Ca2+ in cultured porcine aortic endothelial cells

To test the hypothesis that protamine influences calcium movement in endothelial cells, we measured the concentration of intracellular free calcium ([Ca2+]i) in cultured porcine aortic endothelial (PAE) cells in Krebs solution (2.5mM Ca2+, pH 7.4) at 37 degrees C, by fura-2 fluorimetry. The basal [Ca2+]i of PAE cells was 113+/-18 nM (n=6). Protamine increased [Ca2+]i in a concentration-dependent manner (EC50, the concentration having 50% of the maximum effect, 1.4+/-0.3 microg mL(-1), n=6). The response of PAE cells to 100 microg mL(-1) protamine (330+/-80 nM, n=6) was blocked by a Ca2+ chelator, 5 mM glycoletherdiaminetetraacetic acid (EGTA; 131+/-16 nM, n=6), and by a non-selective Ca2+ channel blocker, 3 mM Co2+ (134+/-14 nM, n=6). These results suggest that Ca2+ influx through cell-membrane Ca2+ channels is mainly responsible for the protamine-induced Ca2+ elevation.

Systemic hypotensive response to protamine following chronic inhibition of nitric oxide synthase in rats

PURPOSE

The aims of the present studies were to determine whether the systemic hypotensive response to protamine was modified in rats pre-treated for two weeks with the nitric oxide synthase inhibitor, NG-nitro-L-arginine-methyl ester (L-NAME), and to evaluate the inhibitory effect of heparin on the systemic hypotensive response to protamine in vivo.

METHODS

Male rats were randomly assigned into four groups. Normal saline 12 microliters.day-1, D-NAME (an inactive enantiomer of L-NAME), 10 mg.kg-1, L-NAME, 1 or 10 mg.kg-1.day-1 i.p. was administered for two weeks and the haemodynamic changes were measured after protamine administration. In another experiment, male rats were assigned to two groups. In one, the heparin group, protamine was administered after heparin had been administered and in the other, protamine group, protamine alone was administered.

RESULTS

L-NAME inhibited the decrease in systemic arterial pressure after protamine administration (P < 0.05), but D-NAME had no effect. Also, heparin reduced the decrease in systemic arterial pressure after protamine (P < 0.05).

CONCLUSION

Nitric oxide is mainly responsible for mediation of the systemic hypotensive response to protamine which is also reduced by heparin.

The effect of protamine on the epicardial microflow and the graft flow in open-heart surgery

To evaluate the effect of coronary revascularization on myocardial perfusion and surgical outcome regarding graft flow, we used laser Doppler flowmetry to assess the epicardial microcirculation in patients undergoing coronary artery bypass grafting (CABG) or valve replacement (VR) and electromagnetic flowmetry to measure graft flow in the CABG group. In the CABG group, the preoperative mean laser Doppler flow rate (LDF) in the epicardium of the left ventricle significantly increased at the end of cardiopulmonary bypass (CPB) (22 +/- 7 arbitrary units (AU) to 60 +/- 13 AU, p < 0.001). This value further increased 10 min after protamine infusion (66 +/- 14 AU, p < 0.01), but was significantly reduced 30 min later (51 +/- 14 AU, p < 0.002). Compared to the post-CPB value (34 +/- 10 ml/min) before protamine infusion, the mean graft flow (ml/min) to this area significantly increased 10 min after protamine infusion (41.3 +/- 10 ml/min, p < 0.001) but significantly decreased 30 min later (29 +/- 9 ml/min, p < 0.001). The preoperative mean LDF in the VR group was significantly higher than in the CABG group (p < 0.01). In the CABG group, there was a positive correlation between the LDF and graft flow at the end of CPB (r = 0.788) and 10 (r = 0.767) and 30 (r = 0.784) min after protamine infusion. This study shows that coronary bypass grafting increases the myocardial microcirculation which, together with graft flow, could give an early indication of the effect of surgery on myocardial microcirculation. Furthermore, protamine was found to be one of the factors contributing to graft flow reduction postoperatively and, therefore, newer methods of heparin reversal may be desirable.

Prophylactic administration of histamine 1 and/or histamine 2 receptor blockers in the prevention of heparin- and protamine-related haemodynamic effects

The efficacy of prophylactic administration of H1 and H2 receptor blockers to prevent adverse haemodynamic responses to heparin and protamine was studied. The control group (n = 10) received no histamine receptor blocker, group H1 (n = 10) received oral terfenadine 60 mg, group H2 (n = 10) received oral ranitidine 300 mg, and group H1+H2 (n = 10) received both terfenadine and ranitidine on the night before the operation and on call to the operating room. Heparin sulphate 300 U/kg was injected directly into the right atrium, and protamine hydrochloride was administered at the conclusion of bypass over at least three minutes through a peripheral route. Following the injection of heparin, plasma histamine-like activity (H-LA) was increased significantly in all four groups. While systolic, diastolic, mean arterial and central venous pressures were decreased significantly in the control group, no significant changes were observed in the H1 and H2 groups. Protamine infusion did not lead to an increase in H-LA. Prophylactic administration of histamine receptor blockers (H1 or H2) attenuated the heparin-induced adverse haemodynamic response but did not change the protamine-related haemodynamic effects. Factors other than histamine may play a major role in protamine induced cardiovascular changes.

Protamine-induced hypotension in heart operations: application of the concept of ventricular-arterial coupling

Protamine sulfate often causes hypotension during heparin neutralization. The concept of ventricular-arterial coupling was applied to determine whether a negative inotropic effect or a vasodilating effect of protamine was the major contributing factor to this hypotension. Thirty-five patients who underwent cardiac operations were studied during operation by measuring instantaneous left ventricular pressure and aortic flow to examine the end-systolic pressure-volume relationship. We obtained end-systolic elastance and effective arterial elastance values in a beat-to-beat fashion with a single-beat estimation method. In 28 of the 35 patients (80%), mean arterial pressure decreased more than 10 mm Hg with protamine infusion. Parameters were compared at the following three points: before a decrease in mean arterial pressure (control), at maximally decreased mean arterial pressure (maximum), and at a middle point between control and maximum values (midpoint). At both midpoint and maximum, mean arterial pressure decreased significantly (control 79.6 +/- 12.6 mm Hg, midpoint 66.5 +/- 10.8 mm Hg, maximum 52.7 +/- 9.9 mm Hg; p < 0.01). Similar changes were observed in effective arterial elastance (control 2.00 +/- 0.75 mm Hg/ml, midpoint 1.60 +/- 0.53 mm Hg/ml, maximum 1.31 +/- 0.46 mm Hg/ml; p < 0.01). Although the decrease in end-systolic elastance at midpoint (control 3.08 +/- 1.61 mm Hg/ml, midpoint 2.92 +/- 1.68 mm Hg/ml) did not reach statistical significance, end-systolic elastance significantly decreased at maximum (2.63 +/- 1.46 mm Hg/ml; p < 0.01). Continuous measurements showed that the decreases in mean arterial pressure and effective arterial elastance always preceded the depression of end-systolic elastance and that afterload reduction by vasodilating effect of protamine was the mechanism most likely to have initiated the hypotension. Delayed decrease in contractility may be ascribed to reduced coronary perfusion pressure caused by vasodilation or to a direct effect of protamine.

Nitric oxide inhibition attenuates systemic hypotension produced by protamine

BACKGROUND

Protamine reversal of heparin anticoagulation often causes systemic hypotension, and in vitro studies suggest that this may be mediated by release of nitric oxide from the endothelium. The present investigations were designed to evaluate the direct myocardial effects of protamine and to determine in vivo whether nitric oxide inhibition can prevent hypotension during protamine infusion.

METHODS/RESULTS

Protamine sulfate (50 microg/ml) was added to perfusate of eight isolated rabbit heart preparations; in six other preparations, a similar concentration of prolamine was added to heparinized (5 U/ml) Krebs perfusate. Left ventricular developed pressure, maximum rate of pressure rise, and heart rate declined significantly (p < 0.01) in hearts exposed to protamine only (65.0% +/- 6.6%, 55.5% +/- 6.0%, and 87.6% +/- 2.5% of baseline, respectively), whereas protamine added to heparinized perfusate caused little change in developed pressure, maximum rate of pressure rise, and heart rate (85.3% +/- 5.4%, 84.9% +/- 5.5%, and 98.8% +/- 1.6%). To study systemic effects of protamine, we measured hemodynamic parameters in 12 heparinized dogs (150 U/kg). During protamine infusion (1.5 mg/kg intravenously over 30 seconds), mean blood pressure decreased by 46% +/- 7% from baseline (P < 0.05), cardiac output decreased by 38% +/- 4% (p < 0.05), and systemic vascular resistance decreased bv by 14& +/- 9%. After hemodynamic stabilization, Ng-monomethyl-L-arginine (2 mg/kg), a competitive inhibitor of nitric oxide synthesis, was administered to six dogs, and methylene blue (2 mg/kg), an inhibitor of cyclic guanosine monophosphate synthesis, was administered to the remaining six dogs. After treatment with Ng-monomethyl-L-arginine and methylene blue, the second infusion of protamine sulfate caused no significant change in blood pressure or cardiac output. In an additional six dogs, Ng-monomethyl-L-arginine pretreatment (5 mg/kg) blocked the effects of the first dose of protamine. The effect of Ng-monomethyl-L-arginine could be reversed by the addition of (6 mg/kg) L-arginine but not D-arginine.

CONCLUSIONS

Protamine-heparin complex does not cause direct myocardial depression but does lead to severe hypotension in vivo. The finding that hypotension can be blocked by inhibitors of the nitric oxide pathway confirms previous in vitro studies indicating that the effects of protamine are mediated, in part, by the vascular endothelium. Further, these studies suggest a novel approach to prevention of hemodynamic complications caused by heparin reversal after cardiopulmonary bypass.

Effects of differing rates of protamine reversal of heparin anticoagulation

BACKGROUND

Protamine sulfate reversal of heparin anticoagulation may be associated with adverse cardiovascular side effects. The purpose of this study was to determine whether diminished systemic oxygen consumption and hemodynamic changes were more likely to accompany rapid versus slow protamine administration.

METHODS

Fifteen patients undergoing abdominal aortic aneurysm resection in a prospective randomized double-blinded study received intravenous protamine (1.5 mg/kg) rapidly during a 3-minute period (group I, n = 7) or slowly during a 15-minute period (group II, n = 8). Systemic oxygen consumption (VO2) and hemodynamic parameters were assessed for up to 20 minutes after protamine administration began.

RESULTS

Blood pressure declines (millimeters of mercury) were greatest in group I with rapid protamine administration (-19 systolic and -9 diastolic) compared with group II with slow protamine administration (-12 systolic and -1 diastolic). Heart rate fell markedly in both groups I and II. Cardiac output (CO) declined in group I at virtually all time periods. Similar CO declines in group II occurred 10 minutes after protamine infusion had begun and persisted for 3 minutes after protamine administration was complete. Maximum VO2 decreases were -16% (60 seconds into protamine infusion) and -13% (1.5 minutes after protamine infusion) in groups I and II, respectively, with statistically significant declines (p < 0.05) occurring only in group I compared with baseline values. Statistically significant differences (p < 0.01), however, were found when mean declines during and after protamine infusion were compared with controls for both CO and VO2 in both groups.

CONCLUSIONS

Significant declines in systemic VO2 and hemodynamic perturbations accompany protamine reversal of heparin anticoagulation during aortic surgery. Rapid protamine administration increases the magnitude of these adverse responses.

Protamine induces endothelium-dependent vasodilatation of the pulmonary artery

BACKGROUND

Protamine sulfate, which is used for heparin neutralization, has been reported to induce catastrophic pulmonary vasoconstriction after infusion. However, in the systemic circulation, protamine infusion induces hypotension due to peripheral vasodilation.

METHODS

To determine whether protamine also could induce vasodilation in the pulmonary circulation, third-order canine pulmonary artery segments were studied in vitro in organ chambers.

RESULTS

In pulmonary artery segments that were caused to contract with phenylephrine (10(-5) mol/L), protamine sulfate (40 to 400 micrograms/mL, final organ bath concentration) produced concentration-dependent relaxation in canine pulmonary artery segments with endothelium (to 74% +/- 7% of the initial contraction to phenylephrine) that was significantly greater (p < 0.05) than in segments without endothelium (30% +/- 6% of the initial phenylephrine contraction). Pretreatment of arterial segments with NG-monomethyl-L-arginine (10(-5) mol/L), the competitive inhibitor of nitric oxide synthesis from L-arginine, did not change tension of arterial segments, but NG-monomethyl-L-arginine attenuated the relaxation to protamine. The inhibitory effect of NG-monomethyl-L-arginine could be reversed by the addition of L-arginine (10(-4) mol/L) but not D-arginine (10(-4) mol/L). Endothelium-dependent vasodilation to protamine (40 to 400 micrograms/mL) also could be inhibited by heparin (8 U/mL, final organ bath concentration). However, the inhibitory effect of heparin could be overcome by adding higher concentrations of protamine.

CONCLUSIONS

Protamine-mediated pulmonary vasodilatation could be an important mechanism to protect against the constrictive effects of autocoids generated during heparin neutralization. Such a mechanism might be dysfunctional in certain persons and put them at risk for pulmonary vasoconstriction after protamine infusion.

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)

Reversal of heparin anticoagulation by recombinant platelet factor 4 and protamine sulfate in baboons during cardiopulmonary bypass

The ability of recombinant platelet factor 4 and protamine to neutralize heparin after cardiopulmonary bypass was compared in anesthestized baboons. Clotting titration curves of heparinized baboon blood demonstrate an anticoagulant effect of protamine that is not seen with recombinant platelet factor 4. Neither drug caused meaningful changes in central pressures or cardiac output within 30 minutes after injection. After 30 minutes of cardiopulmonary bypass, recombinant platelet factor 4 normalized thrombin times and activated partial thromboplastin times within minutes of injection, but protamine did not. Neither drug altered bleeding times. Recombinant platelet factor 4 caused a species-specific leukopenia in baboons and significantly increased activated complement protein 3 (C3a) more than protamine. However, the increase in plasma C3a was small and neither drug caused a significant increase in plasma neutrophil elastase-alpha 1 proteinase inhibitor complex. We conclude that recombinant platelet factor 4 is effective and safe in baboons, does not have an anticoagulant effect with excess concentration, and reverses in vivo heparin more rapidly than protamine. The data support progression to a clinical trial.

Use of the activated coagulation time and heparin dose-response curve for the determination of protamine dosage in vascular surgery

The activated coagulation time (ACT) can be used to construct a two-point heparin dose-response curve (HDRC) from the ACT values at baseline and 5 minutes after heparin administration. The ACT value at any subsequent time interval can then be used to estimate the residual heparin activity from the HDRC. The protamine dose is calculated to be the amount of residual heparin multiplied by a correction factor (1.3 was suggested for cardiac surgery). In vascular surgery, heparin and protamine dosing remain empirical, ACT monitoring is not standard, and use of the HDRC has not been previously investigated. Forty-five patients were prospectively randomized to one of three groups. ACT was measured before heparinization (1 mg/kg, 1 mg = 100 U), 5 minutes later, and then every 30 minutes until just prior to and after protamine administration. Group I received 1 mg/kg of protamine. In Groups II and III the residual heparin activity was interpolated from the HDRC and multiplied by 1.3 or 1.0, respectively, to derive the protamine dosage. Randomization created balanced groups with respect to demographic data. The individual peak effect of heparin ranged from 177% to 401% of control. The ACT returned to control after protamine in all groups. The protamine dose was significantly less when the HDRC was used (P < 0.05). Group III received the least protamine (0.64 +/- 0.07 mg/kg, P < 0.05). No adverse protamine reactions or postoperative bleeding occurred. It is concluded that ACT monitoring and use of the HDRC provides a safe and easy method to individualize protamine dosage in vascular surgery.

Pilot study of the efficacy of a thrombin inhibitor for use during cardiopulmonary bypass

Heparin is normally used for anticoagulation during cardiopulmonary bypass (CPB), but its use is contraindicated in patients with a history of heparin-induced thrombocytopenia, heparin-provoked thrombosis, or both. Heparin therapy can also be ineffective due to heparin resistance. A short-acting, oligonucleotide-based thrombin inhibitor (thrombin aptamer) may potentially serve as a substitute for heparin in these and other clinical situations. We tested a novel thrombin aptamer in a canine CPB pilot study to determine its anticoagulant efficacy, the resultant changes in coagulation variables, and the aptamer's clearance mechanisms and pharmacokinetics. Seven dogs were studied initially: Four received varied doses of the aptamer (to establish the pharmacokinetic profile) and 3 received heparin. Subsequently, 4 other dogs underwent CPB, receiving a constant infusion of the aptamer before CPB (to characterize the baseline coagulation status), with partial CPB and hemodilution, during 60 minutes of total CPB, and, finally, after a 2-hour recovery period. At a 0.5 mg.kg-1.min-1 dose, the activated clotting time rose with aptamer infusion from 106 +/- 12 seconds to 187 +/- 8 seconds (+/- 1 standard deviation) (p = 0.014), increased further with hemodilution (to 259 +/- 41 seconds; p = 0.017), and was even more prolonged during total CPB (> 1,500 seconds; p < 0.001). This later increase in the activated clotting time paralleled a rise in the plasma concentration of the thrombin aptamer during total CPB, as determined by high-performance liquid chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of heparin with polyallylamine-immobilized surfaces

A new method to bind ionically and remove heparin from solution and dilute serum is described. Utilizing cellulose diacetate (CA) as the polymer substrate, a cationic polymer chain--poly(allylamine)-PALA--was immobilized directly onto the CA surface and onto the surface using poly(ethylene glycol) (PEG) spacer groups. The ionic interaction between the anionic heparin molecule and the cationic PALA polymer is specific and effective to remove heparin from the bulk solution. The binding properties of heparin onto the PALA and PEG-PALA surfaces were examined. The effects of PEG spacers on heparin binding onto the PALA-immobilized surface were investigated by varying the Mw of PEG spacers. PALA (Mw 8500)-immobilized surfaces exhibited enhanced heparin binding. The maximum heparin binding was observed in the region of PEG Mw 2000-4000. For the high-molecular-weight PALA (Mw 50,000)-immobilized surfaces, heparin binding was independent of the molecular weight of PEG. PEG spacers were also evaluated for their ability to prevent or decrease protein (albumin) adsorption. It was observed that at high albumin concentrations, the adsorption of proteins decreased with increasing chain length of PEG, up to Mw 3400. These observations suggest that low-molecular-weight PALA (Mw 8500)-immobilized CA surfaces with PEG spacers (Mw 3400) may provide increased heparin binding capacity and decreased protein adsorption.

Neutralization of the antithrombotic effects of heparin and Fraxiparin by protamine sulfate

In general, the in vitro anti Xa activity of low molecular weight heparins is neutralized to a lesser degree than the anti Xa activity of unfractionated heparin. To determine whether these differences occur in vivo, a rabbit stasis thrombosis model and a rat laser-induced thrombosis model were utilized. In the laser model, a similar degree of neutralization of the antithrombotic activity of heparin and Fraxiparin was obtained. However, in the stasis thrombosis model, significant antithrombotic activity of Fraxiparin remained after equigravimetric protamine administration. Ex vivo APTT, thrombin time, Heptest, amidolytic anti Xa and anti IIa assays were performed. A coefficient (r = .806) was obtained for the correlation of Heptest activity to antithrombotic effect in the stasis thrombosis model, while the coefficients obtained for the other tests ranged from .152-.570. However, after neutralization by protamine, the thrombin time exhibited the highest correlation coefficient (r = .685) between ex vivo activity and residual antithrombotic effect. Since Fraxiparin retains antithrombotic activity after protamine administration, clinical benefit may be observed for this low molecular weight heparin as compared to unfractionated heparin after neutralization.

Protamine releases endothelium-derived relaxing factor from systemic arteries. A possible mechanism of hypotension during heparin neutralization

BACKGROUND

When used to reverse the anticoagulant effect of heparin, protamine sulfate often causes vasodilation that can lead to systemic hypotension. Protamine is rich in the basic amino acid arginine, which is the precursor of endothelial cell synthesis of nitric oxide, and nitric oxide is the active component of endothelium-derived relaxing factor (EDRF).

METHODS AND RESULTS

To determine whether the hypotensive effect of protamine could be due to stimulated release of EDRF, we studied rings (4-5 mm) of canine coronary, femoral, and renal artery suspended in organ chambers containing physiological salt solution (37 degrees C and 95% O2-5% CO2). Arterial rings with and without endothelium were contracted with prostaglandin F2 alpha (2 x 10(-6) M) and exposed to increasing concentrations of protamine (final organ bath concentration, 40-400 micrograms/ml). In arterial segments without endothelium, protamine caused only a modest decrease in tension. However, protamine induced concentration-dependent relaxation in all arterial segments with endothelium, which was significantly greater than in segments without endothelium (p less than 0.05). The endothelium-dependent relaxation induced by protamine was inhibited by NG-monomethyl-L-arginine (L-NMMA) (10(-5) M), but L-NMMA had no effect on rings without endothelium. The action of L-NMMA could be reversed by L-arginine (10(-4) M) but not D-arginine (10(-4) M).

CONCLUSIONS

This study demonstrates that protamine stimulates the release of EDRF from arterial endothelium, and that endothelium-dependent vasodilation may be an important cause of systemic hypotension during protamine infusion.

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)

Determinants of outcome in lesions of the thoracic aorta in patients with multiorgan system trauma

Of all patients presenting at our level 1 trauma center with multiorgan system injuries, 33 have been identified with acute lesions of the thoracic aorta. Mean severity injury score was 24 +/- 3. Four patients underwent resuscitative thoracotomy upon arrival in the emergency department. One survived and fully recovered. The rest underwent diagnostic procedures and repair of aortic lesions in conjunction with surgical treatment of other injured organ systems. The overall survival rate was 82 percent. Survivors arrived significantly faster to the ED and had lesser degree of multiorgan system injuries. There was no difference in the time spent to make the diagnosis of acute aortic disruption for survivors and nonsurvivors, nor was a difference in time to arrive in the operating room once the diagnosis of aortic injury has been established. Morbidity was related to ischemia to distal organs in four patients of whom two presented with multiple lesions of the thoracic aorta; two remained paralyzed and two had only lower limb spasticity. All discharged survivors were alive at 12 months' follow-up. The type of surgical repair did not influence the outcome of patients with single, typical aortic lesions; however, "clamp/sew" technique was not adequate when multiple aortic tears were found intraoperatively. The outcome of surgical treatment of the traumatic aortic lesions of patients with polytrauma may be influenced by the speed of arrival to the ED, the magnitude of multiorgan system involvement, and the application of appropriate surgical technique for repair according to the intrathoracic findings and the timing of aortic repair vis-a-vis other surgical treatment.

Hemodynamic effects of intraaortic versus intravenous protamine administration after cardiopulmonary bypass in man

A hemodynamic study of men undergoing elective coronary artery bypass surgery was undertaken to elucidate the side effects of protamine given into the ascending aorta (group A, n = 16) or into the central venous line (group V, n = 16). After termination of extracorporeal circulation, protamine was infused over 120 seconds, and the hemodynamic profile was continuously recorded. During the first minute, the systemic arterial pressure fell to about 60% of the preprotamine level in both groups, but the hemodynamic changes occurred more rapidly (p < 0.05) in group V than in group A, with maximal pressure drop at 61.7 +/- 2.7 vs 74.4 +/- 4.9 seconds. Following spontaneous restoration of the systemic blood pressure, the pulmonary artery pressure rose considerably in both groups, as did the pulmonary capillary wedge and central venous pressures, reaching higher levels in the intravenous group. The cardiovascular responses were again more rapid in group V than in group A (p = 0.004). The degree of systemic hypotension thus did not benefit from use of the intraaortic rather than the intravenous route for administering protamine. The more pronounced and more rapid pulmonary circulatory changes in the intravenous group suggest that the hemodynamic effects of protamine are initiated in the lungs.

The role of plasma proteins in formation of obstructive protamine complexes

Formation of complexes between heparin and protamine (in saline), or heparin, plasma proteins, and protamine (in plasma) was assessed by measurements of light transmission through different test solutions. To examine the formation of these complexes, 125I-labeled protamine was used. Addition of 125I-protamine to plasma or blood resulted in the sedimentation of 125I-protamine in the form of insoluble complexes. This complex formation was not affected by the presence of heparin, suggesting that protamine-plasma protein interaction may be primarily responsible for precipitation of 125I-protamine. To assess the capability of these complexes to obstruct the pulmonary circulation, an in vitro experimental model was developed. Citrated serum, plasma, blood, or saline were allowed to flow through a glass bead column with the help of a peristaltic pump. A pressure transducer positioned before the column allowed pressure measurements at a constant flow rate during the experiment. Mixing of protamine with plasma or blood prior to their passage through the glass bead column resulted in a significant increase in pressure suggesting that the column was being clogged with insoluble complexes. The increase in pressure occurred both in the presence and absence of heparin in plasma or blood. Under identical experimental conditions, the increase in pressure was insignificant when protamine was added to saline or serum regardless of whether heparin was present or absent. This was further confirmed by the use of 125I-protamine. These observations suggest that protamine forms insoluble complexes with certain plasma proteins. Based on these observations, it is hypothesized that following intravenous administration, protamine immediately forms complexes in circulating blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Aprotinin reduces intraoperative and postoperative blood loss in membrane oxygenator cardiopulmonary bypass

To determine whether aprotinin can provide a significant improvement of hemostasis in cardiopulmonary bypass using a membrane oxygenator, we tested this drug in a prospective, randomized, double-blind, placebo-controlled clinical trial. The subjects were 80 male patients undergoing cardiopulmonary bypass for coronary artery bypass grafting. Forty patients received aprotinin and 40 patients served as placebo controls. Aprotinin (4 x 10(6) KIU) was given as a continuous infusion, starting before operation and continuing until after cardiopulmonary bypass; additionally, 2 x 10(6) KIU aprotinin was added to the pump prime. Intraoperative and postoperative bleeding, respectively two thirds and one third of the total perioperative blood loss, were both significantly reduced in the aprotinin-treated group (p less than 0.01). The total average perioperative blood loss, corrected to a hemoglobin concentration of 7 mmol/L, was 550 mL in the aprotinin-treated patients versus 900 mL in the control patients. This reduction in blood loss, furthermore, significantly decreased the amount of postoperative blood transfusions (p less than 0.05) and increased the percentage of patients who did not receive postoperative donor blood from 42% to 68%. Aprotinin increased the activated clotting time significantly during cardiopulmonary bypass, which led to a reduction in heparin usage. The improved hemostasis during operation, despite the prolonged activated clotting time, might even abolish the need for heparin conversion with protamine at the end of cardiopulmonary bypass, thus allowing retransfusion through cardiotomy suction to be continued, which saves the blood that is currently lost with vacuum suction.

Systemic and pulmonary circulatory effects of protamine following cardiopulmonary bypass in man

The cardiovascular effects of protamine were studied in 19 men with normal left ventricular function undergoing primary myocardial revascularization. Protamine was given over 120 sec after termination of cardiopulmonary bypass. Arterial and pulmonary pressures, aortic blood flow, central venous pressure, heart rate and electrocardiogram were continuously registered. Pulmonary capillary wedge pressure was recorded at the times of maximal hemodynamic response. The systolic arterial pressure fell from 116 to 66 mmHg about 60 sec after the start of protamine infusion, but spontaneously began to rise after a few seconds, reaching 90% of pre-protamine levels at 126 sec. No inotropic drugs or volume infusion were given. At about 2 min, the mean pulmonary artery pressure rose from 16.3 to 26.2 mmHg and the central venous pressure from 7.0 to 11.4 mmHg. The heart rate and cardiac output were almost unchanged throughout. Systemic hypotension and pulmonary hypertension are suggested to represent true side effects of protamine or protamine/heparin complex. When left ventricular function is good, the hypotension reverses without treatment. Volume infusion may indeed precipitate right heart failure when the pre-load effect is added to the subsequent protamine-induced pulmonary hypertension.

Prophylactic administration of histamine1 and histamine2 receptor blockers in the prevention of protamine-related haemodynamic effects

We studied the effects of the prophylactic administration of histamine1 and histamine2 receptor blockers on haemodynamic changes, including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MBP), central venous pressure (CVP), and heart rate (HR, beats.min-1) before and after the administration of protamine in two groups of patients having coronary artery bypass graft surgery. Group I patients received no histamine blockers, whereas patients in Group II were treated prophylactically with both H1 (diphenhydramine) and H2 (cimetidine) receptor blockers. The mean SBP, DBP, MBP, CVP, and HR before (and after) administration of protamine in group I patients were 114 +/- 16 (90 +/- 16) mmHg, 64 +/- 11 (51 +/- 8) mmHg, 81 +/- 11 (65 +/- 10) mmHg, 10 +/- 3 (11 +/- 7) mmHg, and 92 +/- 10 (87 +/- 13) before (and after) protamine administration. Group II patients had mean SBP, DBP, MBP, CVP, and HR of 113 +/- 19 (113 +/- 17) mmHg, 61 +/- 12 (62 +/- 11) mmHg, 79 +/- 15 (80 +/- 13) mmHg, 9 +/- 3 (9 +/- 2) mmHg, and 88 +/- 6 (86 +/- 4) before (and after) protamine administration. Our data show that only in Group I patients who did not receive histamine receptor blockers, were there significant haemodynamic changes following protamine administration (P less than 0.05). We conclude that the prophylactic administration of histamine receptor blockers prevents some of the adverse haemodynamic effects associated with protamine administration.

Effects of protamine on histamine release from human lung

Animal mast cell models demonstrate direct histamine release by protamine. Investigators have proposed that protamine also releases histamine in man. We studied the effects of protamine alone and heparin-protamine mixtures on minced lung tissue for evidence of histamine release. We were unable to demonstrate the release of histamine despite positive anti-IgE controls. Nonimmunologic histamine release from human lung appears unlikely as a mechanism for protamine reactions in man.

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.

The effect of histamine-receptor blockade on the hemodynamic responses to protamine

A prospective randomized study was undertaken to evaluate the use of histamine-receptor blockade to prevent protamine-induced hypotension in patients undergoing elective aortocoronary artery bypass graft surgery. Normotensive patients with good left ventricular function who did not receive vasoactive or inotropic agents after cardiopulmonary bypass (CPB) were allocated to either a study or a control group. After CPB, patients in the study group received 10 mg of chlorpheniramine, and 400 mg of cimetidine, intravenously, five minutes before infusion of protamine. In both groups, protamine was injected via a central venous cannula at 2.5 mg/sec. Hypotension in the control group was significantly more severe and prolonged than in the study group. Systolic and mean arterial blood pressures in the control group fell 35% and 34%, differing significantly (P less than 0.01) from the study group in whom the reduction was 24% for both systolic and mean pressures. In addition, the control group showed significant falls in central venous pressure and increases in heart rate following protamine. In conclusion, it appears that the hemodynamic changes are only partially mediated through histamine action, and the normal response to protamine may be modified, but not abolished, by H1 and H2 receptor blockade. This blockade may, however, prevent the reduction in right heart preload and increase in heart rate following protamine.

Pulmonary hypertensive effect of heparin and protamine interaction: evidence for thromboxane B2 release from the lung

The characteristic pulmonary hypertensive effect of the heparin and protamine interaction has been studied in the isolated pig lung preparation using sequential autologous blood perfusate and dextran perfusate. A significant (p less than 0.001) increase in pulmonary artery pressure at constant flow was seen in 10 of 14 dextran and 12 of 15 blood perfusions. The average increase for dextran was 112 percent and for blood, 109 percent. Antihistamines did not inhibit the response. However, this was abolished in all 11 animals treated with aspirin. In 11 intact swine, thromboxane B2 blood levels increased significantly (p less than 0.01) from 0.46 +/- 0.38 ng/dl to 2.97 +/- 1.5 ng/dl. Thus, pulmonary hypertension associated with protamine reversal of heparinization is associated with prostaglandin release from the lung, and this does not require mediation of platelets or leukocytes.