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

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.

Coagulation considerations for infants and children undergoing cardiopulmonary bypass

Cardiac surgery involving cardiopulmonary bypass imposes a significant pathophysiologic burden on patients. Pediatric patients are especially predisposed to the adverse effects of surgery and bypass on the coagulation system, with resultant bleeding, transfusion, and poor outcomes. These risks accrue to pediatric patients in inverse proportion to their weight and are attributable to hematologic immaturity, coagulation defects associated with congenital heart disease, bypass equipment, and the nature of congenital heart surgery. Standard anticoagulation does not completely inhibit thrombin generation, and continuous consumption of coagulation factor continues throughout bypass. Conventional measurements of anticoagulation during bypass poorly reflect this incomplete anticoagulation, and alternate methods may improve anticoagulant therapy. Emerging therapies for blocking the effects of bypass on the coagulation system hold promise for decreasing bleeding and related complications, and improving outcomes in congenital heart surgery.

Serious anaphylactic reactions due to protamine sulfate: a systematic literature review

Anaphylactic reactions caused by injection of protamine sulfate during cardiac surgery are a well-known complication. A systematic literature review was therefore conducted to gather evidence of the knowledge concerning these side effects, and to see if any prospective randomized studies supported this. Studies investigating the effect of protamine sulfate in human beings were extracted from MEDLINE, Embase and the Cochrane Library, retrieving 487 articles. Abstracts were evaluated by both authors, and referred articles not found in the primary search were furthermore extracted from reviews and case reports, resulting in a total of 272 relevant articles. Of these, 9 retrospective studies and 16 prospective studies were performed in an evidence-based manner. However, only 3 of the 16 prospective articles had an optimal design as far as inclusion criteria, randomization, and description of symptoms were concerned. Incidence of anaphylactic reactions in the prospective studies was 0.69% compared to 0.19% in the retrospective studies, but caution should be taken due to a pronounced heterogeneity of those studies. One study found heparinase I unsuitable as replacement for protamine sulfate. Overall, our findings support the low incidence of anaphylactic reactions reported in previous studies, but of note only few prospective investigations was conducted on the subject. Our study also emphasizes the need for critical appraisal of many routine procedures: in all aspects of medical care, systematic literature review conducted in a well-structured, repeated manner should be given high priority.

Adverse events after protamine administration following cardiopulmonary bypass in infants and children

We performed this study to determine the incidence of and risk factors for adverse events (AEs) in infants and children after the IV administration of protamine after cardiopulmonary bypass. In a retrospective cohort study, all relevant anesthesia records from a 3-yr period were examined to identify AEs after protamine. The AEs were then grouped into three categories by applying increasingly strict criteria. Among 1249 anesthesia records, there were no documented episodes of isolated or hypotension-associated right-sided cardiac failure or acute pulmonary dysfunction. The incidence of systemic hypotension after protamine was between 1.76% (95% confidence interval [CI], 1.11%-2.65%) and 2.88% (95% CI, 2.03%-3.97%), depending on the strictness of case definition. To identify risk factors, we performed a nested case-control study in which unmatched controls were randomly selected from the parent cohort at a 4:1 ratio to cases. Cases of hypotension after protamine were more likely during operations on girls (odds ratio [OR], 6.47; 95% CI, 1.66-32.8), after larger doses of protamine (OR, 1.88; 95% CI, 1.03-3.63), or after smaller doses of heparin (OR, 0.49; 95% CI, 0.17-0.67).

IMPLICATIONS

Systemic hypotension after protamine administration occurred in 1.76%-2.88% of pediatric patients having cardiac surgery. Female sex, larger protamine dose, and smaller heparin dose were each associated with increased risk. The development of protamine alternatives or prophylactic therapies may be useful for reducing the frequency of these events.

A review of anti-inflammatory strategies in cardiac surgery

It is generally accepted that cardiac surgery is frequently associated with the development of systemic inflammatory response. This phenomenon is very variable clinically, and can be detected by measuring plasma concentrations of certain inflammatory markers. Complement component, cytokines and adhesion molecules are examples of these markers. Systemic inflammation can be potentially damaging to major organs. Several anti-inflammatory strategies have been used in recent years, aiming to attenuate the development of systemic inflammatory response. This article summarizes recently published literature concerning the use of anti-inflammatory techniques and pharmacological agents in cardiac surgery. In particular, the anti-inflammatory effects of off-pump surgery, leukocyte filtration, corticosteroids, aprotinin, phosphodiesterase inhibitors, dpoexamine, H2 antagonists and ACE inhibitors are reviewed. The overall conclusion is that although certain strategies reduce plasma levels of inflammatory mediators, convincing evidence of significant clinical benefits is yet to come.

Mortality and adverse events after protamine administration in patients undergoing cardiopulmonary bypass

We designed this study to determine whether adverse hemodynamic events after a protamine administration increase the risk of in-hospital mortality. Using a retrospective cohort study design, medical and anesthesia records of patients undergoing cardiopulmonary bypass (CPB) at the Hospital of the University of Pennsylvania, Philadelphia, between 1990 and 1994 were reviewed. Adverse events after a protamine administration were determined using strict, predefined criteria, and in-hospital mortality was assessed without knowledge of exposure status. Mortality was more frequent among the 53 patients with adverse events (13.2%) than the 223 patients without events (2.7%; crude odds ratio 5.50; 95% confidence interval, 1.49-20.6). After adjusting for confounders, the odds ratio was 6.98 (95% confidence interval, 1.36-35.9; P = 0.017). Those suffering severe events had the highest mortality (23.5% compared with 8.3% among those with less severe events versus 2.7% among those without any event, P = 0.001 for trend). In addition, the odds ratio was largest when using the strictest definition for protamine-related events. In conclusion, patients undergoing CPB who experience adverse events after a protamine administration have an increased risk of in-hospital mortality. Further studies to confirm these findings and development and testing of protamine alternatives or prophylactic therapies are required to determine if mortality can be reduced.

IMPLICATIONS

A retrospective cohort study demonstrated an association between adverse events after a protamine administration and increased in-hospital mortality.

Risk factors for clinically important adverse events after protamine administration following cardiopulmonary bypass

OBJECTIVES

The purpose of this study was to determine risk factors for adverse events following protamine administration after cardiopulmonary bypass.

BACKGROUND

Intravenous protamine administration is associated with a risk of severe systemic reactions. However, risk factors for these events have not been well delineated, thus hampering development of preventive strategies.

METHODS

A case-control study nested within a cohort of consecutive patients undergoing surgery requiring cardiopulmonary bypass was performed. The primary case definition included those events (pulmonary hypertensive and systemic hypotensive) occurring within 10 min of protamine administration in the absence of other measurable causes of hemodynamic compromise.

RESULTS

Comparing the 53 cases to the 223 control subjects, three risk factors were independently associated with events (multivariable odds ratio [95% confidence interval]): neutral protamine Hagedorn insulin use (8.18 [2.08, 32.2]); fish allergy (24.5 [1.24, 482.3]), and a history of nonprotamine medication allergy (2.97 [1.25, 7.07]). These risk factors demonstrated an increasingly strong association with progressively more specific case definitions. An estimated 39% of cardiopulmonary bypass patients had one or more of these risk factors. Prior intravenous protamine, central venous pressure prior to protamine, preoperative ejection fraction and the need for inotropes when coming off bypass did not exhibit statistically significant associations with events (all p > 0.15). Prior protamine allergy was associated specifically with an increased risk of pulmonary hypertension (multivariable odds ratio 189; 95% confidence interval 13, 2,856).

CONCLUSIONS

Immunologic factors are important in predisposing individuals to protamine reactions, and a substantial proportion of patients are at considerably increased risk Strategies to reduce the risk of protamine-associated events are needed.

Comparison of the effects of enoximone and isoproterenol on protamine cardiotoxicity in anesthetized dogs

In this study we investigated the effects of isoproterenol and enoximone on protamine cardiotoxicity because administration of protamine for heparin reversal during open heart surgery depresses left ventricular function. Eighteen mongrel dogs were entered into this study. After induction of general anesthesia and a stabilization period, a thermodilution catheter was inserted via the jugular vein. Another 2 catheters were inserted into the left ventricle and femoral artery. Heparin and protamine were used in all animals. Heparin dosage was 300 U/kg, and protamine dosage was 4.5 mg/kg. The animals were divided into 3 groups. Six animals received enoximone (5 micrograms/kg per min), 6 animals received isoproterenol (0.05 microgram/kg per min), and 6 animals received no inotropic agent. Measurements were performed before treatment, 5 min after protamine administration, and at 15-min intervals for 1 h. Cardiac output (CO), mean arterial pressure, pulmonary capillary wedge pressure, first derivative of left ventricular pressure (1 +/-) left ventricular systolic pressure, and heart rate were measured. CO was 1582 +/- 34 ml/min in the isoproterenol group (I + P), 1684 +/- 61 ml/min in the enoximone group (E + P), and 1471 +/- 37 ml/min in the protamine group (P) (p < 0.05 E + P vs I + P and P) 60 min after protamine administration. The first derivative of left ventricular pressure (dP/dt) was 1995 +/- 61 mmHg/sec in the I + P group, 2320 +/- 85 mmHg/sec in the E + P group, and 1816 +/- 48 mmHg/sec in the P group (p < 0.05 E + P vs I + P and P). In our experimental study, the isoproterenol and protamine combination did not increase hemodynamic activity. However, isoproterenol alone significantly increased hemodynamic activity as determined by dP/dt values. Protamine administration impairs the effects of beta agonists on the myocardium. In the protamine group, CO and pressure-dependent values were significantly reduced. Isoproterenol administration did not reverse this deterioration because of the loss of the beta-receptor activity. Inotropic agents acting through the beta-adrenergic system have partial effects on myocardium. Enoximone, a phosphodiesterase inhibitor, reverses deterioration of cardiac function after protamine administration because it increases myocardial function via the phosphodiesterase system.

Adverse events after protamine administration in patients undergoing cardiopulmonary bypass: risks and predictors of under-reporting

A retrospective cohort study of patients undergoing cardiopulmonary bypass over 2 years at a single hospital was performed to determine the rate and predictors of attributing events to protamine and reporting them to a well-developed, hospital-based adverse drug reaction (ADR) program. Overall, 123 (12.9%) of 952 procedures were associated with an adverse event. Thirteen percent of these events were attributed to protamine in the medical record and 2.4% were reported to the ADR program. Only 19% of events attributed to protamine were reported. Even after excluding events with other measurable etiologies, the incidence of adverse events (2.6%) was still higher than that of attributed (0.8%) or reported (0.3%) events. Events that manifest as pulmonary hypertension occurred sooner after protamine, or were severe were significantly more likely to be attributed to protamine. These predictors demonstrated similar relationships with the probability of reporting events. Reliance on reporting of adverse events could not only underestimate the risk of these events, but might bias studies by identifying non-representative events.

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.

Effects of protamine on myocyte contractile function and beta-adrenergic responsiveness

The use of protamine sulfate in patients has been associated with severe circulatory collapse and myocardial failure. However, the exact mechanisms responsible for these reactions to protamine remain unclear. Accordingly, we examined the effect of protamine on isolated myocyte contractile function. Indexes of isolated myocyte contractile function, percent shortening, and velocity of shortening were examined using videomicroscopy. Porcine cardiocytes (n = 75) were studied at baseline and in the presence of 80 micrograms/mL protamine. In addition, myocyte function was examined sequentially, first during treatment with 8 IU/mL heparin and then after the addition of a protamine dose sufficient to completely bind the heparin. The binding of heparin and protamine resulted in the formation of a heparin-protamine complex. The protamine concentration of 80 micrograms/mL is approximately equal to the serum concentration of protamine obtained in patients when administered in a dose of 5 mg/kg. In the presence of 80 micrograms/mL protamine, both percent shortening and velocity of shortening fell by more than 32% from baseline values (p < 0.05). The presence of either heparin alone or the heparin-protamine complex resulted in no change in baseline myocyte contractile measurements. Furthermore, to examine the effect of protamine on myocyte beta-adrenergic responsiveness a second series of experiments were performed. Myocyte contractile function was measured when 25 nmol/L isoproterenol was added to each of the protocols above. The presence of 80 micrograms/mL protamine resulted in a significant blunting of myocyte beta-adrenergic responsiveness. The presence of either heparin alone or the heparin-protamine complex resulted in no change in myocyte beta-adrenergic responsiveness.(ABSTRACT TRUNCATED AT 250 WORDS)

Open heart surgery increases the levels of histamine in arterial and coronary sinus blood

The possible release of histamine into the coronary circulation during reperfusion of the cold, cardioplegic heart was investigated during open heart surgery in 13 patients (cardioplegic arrest 54 (35-120 min) (median (range)), cardiopulmonary bypass (CPB) 96 (65-360) min. Samples were drawn concomitantly from coronary sinus and arterial blood before cardioplegia and during myocardial reperfusion for measurement of histamine (radioenzymatic method). Additional arterial samples were drawn pre-, per- and postoperatively. CPB induced a sustained increase in arterial histamine (from 4.02 +/- 2.71 nmol/l preoperatively (mean +/- SD) to maximum 16.31 +/- 7.12 nmol/l, p < 0.009). Immediately before cardioplegia histamine levels were higher in arterial than coronary sinus blood (9.24 +/- 4.85 versus 4.04 +/- 2.07 nmol/l, p < 0.002). During myocardial reperfusion coronary sinus histamine increased to levels similar to that of arterial blood. In conclusion, histamine is released during CPB. Before cardioplegic arrest, there is a net uptake of histamine by the heart, which is abolished during reperfusion, possibly due to increased cardiac release of histamine.