Heparin-induced thrombocytopenia: a common complication in cardiac transplant recipients

The impact of pre-existing hematologic disorders on morbidity and mortality following heart transplantation: Focus on early graft dysfunction

BACKGROUND

Heart transplantation (HT) is the gold standard therapy for advanced heart failure, providing excellent long-term outcomes. However, postoperative outcomes are limited by bleeding, infections, and primary graft dysfunction (PGD) that contribute to early mortality after HT. HT candidates with pre-existing hematologic disorders, bleeding, and clotting, may represent a higher risk population. We assessed the short- and long-term outcomes of patients with pre-existing hematologic disorders undergoing HT.

METHODS AND RESULTS

Medical records of all adult patients who received HT from January 2010 to December 2019 at our institution were retrospectively reviewed. Hematologic disorders were identified via chart review and adjudicated by a board-certified hematologist. Inverse probability weighting and multivariable models were used to adjust for potential pretransplant confounders. Four hundred and ninety HT recipients were included, of whom 29 (5.9%) had a hematologic disorder. Hematologic disorders were associated with severe PGD requiring mechanical circulatory support (aOR 3.15 [1.01-9.86]; p = .049), postoperative infections (aOR 2.93 [1.38-6.23]; p = .01), and 3-year acute cellular rejection (ACR) (≥1R/1B) (aSHR 2.06 [1.09-3.87]; p = .03). There was no difference in in-hospital mortality (aOR 1.23 [.20-7.58], p = .82) or 3-year mortality (aHR 1.58 [.49-5.12], p = .44).

CONCLUSIONS

Patients with hematologic disorders undergoing HT are at increased risk of severe PGD, postoperative infections, and ACR, while in-hospital and 3-year mortality remain unaffected.

Cardiac transplantation after heparin induced thrombocytopenia: A systematic review

PURPOSE

Heparin induced thrombocytopenia (HIT) presents a unique challenge in patients requiring orthotopic heart transplantation (OHT). We sought to pool the existing evidence in a systematic review.

METHODS

Electronic search was performed to identify all relevant studies on OHT in patients with HIT. Patient-level data for 33 patients from 21 studies were extracted for statistical analysis.

RESULTS

Median patient age was 51 [41, 55] years, with 75.8% (25/33) males. All patients had a clinical diagnosis of HIT, and anti PF4/Heparin antibodies were positive in 87.9% (29/33). Median lowest reported platelet count was 46 × 10⁹ /L [27.2, 73.5]. Intraoperatively, 61% (20/33) of patients were given unfractionated heparin (UFH), while 39% (13/33) were given alternative anticoagulants. The alternative agent subgroup required more antifibrinolytics [54% (7/13) vs. 10% (2/20), p = 0.02] and clotting factors [69.2% (9/13) vs. 15.0% (3/20) p<0.01]. Peri-operative thrombosis occurred more in [53.8% (7/13) vs 0% (0/20, p<0.01) alternate agent subgroup. More patients in the alternate agent subgroup required post-operative transfusions [54% (7/13) vs. 0% (0/20), p<0.01]. Thirty-day mortality of 15.2% (5/33) was comparable between the subgroups.

CONCLUSION

Heparin use during OHT may be associated with less adverse effects compared to use of other anticoagulants with no difference in 30-day mortality. This article is protected by copyright. All rights reserved.

Safety and Efficacy of Living Donor Hepatectomy Without Systemic Heparinization: Short- and Long-Term Outcomes

There is no consensus regarding the use of systemic heparin, and long-term outcomes of living donor hepatectomy (LDH) without systemic heparinization have not yet been determined. This study was performed to determine whether systemic heparinization can be omitted during LDH, with a focus on donor safety and long-term outcomes. We retrospectively analyzed the outcomes of 175 cases of LDH performed in our institution between January 2011 and December 2014: group I (n = 79) received systemic heparinization, whereas group II (n = 96) did not, but liver graft was flushed with a heparinized perfusate. Postoperative bleeding requiring blood transfusion or intervention was more frequent in group I than in group II (P = .028). The decreases in donor hemoglobin and hematocrit levels, and platelet count during the early postoperative period, were greater in group I than in group II. In multivariate analysis, systemic heparin was the only independent risk factor for blood transfusion (odds ratio [OR] = 5.114; 95% confidence interval [CI]: 1.201-21.775; P = .027) and significant postoperative bleeding (OR = 7.731; 95% CI: 1.345-44.429; P = .022) after LDH. Most postoperative complications including graft vascular thrombosis were similar between the 2 groups, as was the survival rate, and neither graft loss due to vascular thrombosis nor non-anastomotic biliary stricture was evident. In conclusion, omission of systemic heparinization during LDH is a feasible and safe option without adverse effects.

Anticoagulation management strategies in heart transplantation

Anticoagulation before, during, and after heart transplantation (HT) presents unique challenges to clinicians. Bleeding and thrombotic morbidity continues to affect this patient population throughout all phases of the HT journey. Reversal is commonly required since patients are commonly bridged to HT with left ventricular assist devices, which require chronic anti platelet and anticoagulation. Caution must be exercised in patients requiring cardiopulmonary bypass during surgery who are at risk of complications from heparin induced thrombocytopenia. The reported incidence of venous thromboembolism following HT is high, particularly during the first post-HT year, most likely due to surgery, biopsies, specific immunosuppression (mTOR inhibitors) and immobilization. It is crucial to maintain long-term oral anticoagulation after the first venous thromboembolism event, especially when risk factors exist. A major issue, and one for which there remains considerable debate, is the optimal treatment of such complications, particularly upper extremity venous thrombosis. For both warfarin and the thrombin inhibitors or Factor Xa inhibitors, the clinician must determine potential drug interactions based on the HT drug regimen, and then develop a patient-specific management strategy.

Coil Embolization for a Cerebral Aneurysm in a Heart Transplantation Patient: A Case Report

The number of heart transplantations performed in Japan has been continuously increasing. Here, we report the case of a patient with an unruptured cerebral artery aneurysm after undergoing heart transplantation and was treated using coil embolization. The patient was a 50-year-old woman who was positive for heparin-induced thrombocytopenia (HIT) antibodies and underwent heart transplantation for dilated cardiomyopathy. An unruptured middle cerebral artery aneurysm was treated with coil embolization using argatroban as a heparin substitute. The patient was discharged without any complications. Despite these patients with heart transplantation are characterized by high HIT antibodies rate and the need for immunosuppressive agents, they currently have an excellent prognosis, especially in Japan. Therefore, the knowledge of patient characteristics after heart transplantation is essential for ensuring that these patients receive the most appropriate treatment.

Simultaneous Liver-Kidney Transplantation in Patient with a History of Heparin-Induced Thrombocytopenia: A Case Report and Literature Review

Patient: Male, 58

Final Diagnosis: Heparin-induced thrombocytopenia

Symptoms: Liver and kidney failure

Medication: —

Clinical Procedure: Simultaneous liver-kidney transplantation

Specialty: Transplantology

Is Systemic heparinization necessary during living donor hepatectomy?

Systemic heparinization has traditionally been performed during living donor hepatectomy (LDH) at most transplant centers because of the possibility of graft vascular thrombosis. However, no consensus on the use of systemic heparinization during LDH has yet emerged. The aims of the present study were to compare donor and recipient outcomes with reference to systemic heparinization and to determine whether or not systemic heparin needs to be administered to living donors. Via a retrospective review, we analyzed the outcomes of 137 LDHs performed at our institution from January 2011 to October 2013; 79 donors received systemic heparinization (group I), whereas 58 did not, but the liver graft was flushed with a heparinized perfusate (group II). Patient demographics, intraoperative parameters, laboratory data, postoperative complications, and survival rates were compared between the 2 groups. The overall complication rates did not differ significantly between the 2 groups, but postoperative bleeding requiring red blood cell transfusions occurred more frequently in group I versus group II (7.6% versus 0.0%, P = 0.03). The incidences of graft vascular thrombosis were similar in the 2 groups, and no graft loss caused by vascular thrombosis was evident during the early postoperative period. Moreover, no difference in either posttransplant graft function or survival was apparent between the 2 groups. The rates of decreases in donor hemoglobin, hematocrit, and platelet count levels during the early postoperative period were significantly higher in group I versus group II. In conclusion, the omission of systemic heparinization during LDH is both feasible and safe, with no adverse effects on donor or recipient outcomes.

Drug-Induced Immune Thrombocytopenia

Thrombocytopenia is commonly seen in laboratory findings, especially in critically ill patients. Although the incidence is rare, drug-induced immune thrombocytopenia (DITP) is a serious complication that is often overlooked as a cause of thrombocytopenia. Over the last century, extensive research and data collection have been done in an attempt to better characterize DITP. Heparin-induced thrombocytopenia is the most common DITP and has distinct pathogenesis, diagnosis, and treatment options. However, other offending medications are less well known and have triggered many questions and constant search for answers. This review will discuss both drug-induced immune-mediated and nonimmune-mediated thrombocytopenias, with a focus on immune-mediated processes. Thrombocytopenia caused by chemotherapy will not be discussed in this article.

[Fondaparinux as an alternative anticoagulant in heparin-induced thrombocytopenia in the patient with a ventricular assist device]

Heparin-induced thrombocytopenia is a reaction associated with the use of this drug. It occurs in up to 3% of patients treated for at least 5 days. Its treatment is to stop the heparin, and according to patient needs, replace it with another anticoagulant. We present a patient who, after a heart transplant, and the need for a ventricular assist device, required anticoagulation. The patient developed heparin-induced thrombocytopenia. Heparin was stopped and anticoagulation was replaced by fondaparinux. The peri-operative complications and the management of the coagulation are described.

[Massive haemorrhage after bivalirudin anticoagulation in two heart transplant patients]

Heparin-induced thrombopenia is a common autoimmune complication. It is a prothrombotic state due to the formation of antibodies against heparin/platelet factor 4 complexes. In this situation drugs other than heparin must be used for anticoagulation during extracorporeal circulation (bypass) surgery. Two cases of heart transplantation are presented in whom bivalirudin was used as an anticoagulant during the cardiopulmonary bypass. Severe bleeding complications were observed in both patients. The diagnosis of heparin-induced thrombopenia needs to be improved, as well as the development of protocols for using new drugs other than heparin. For this reason, we have reviewed current protocols and alternative therapies to heparin.

Heparin-induced thrombocytopenia: is it a graft-threatening complication?

Heparin-induced thrombocytopenia (HIT), a prothrombotic complication of heparin therapy, can lead to serious thromboembolic events and cause significant morbidity and mortality. We aim to study the prevalence of HIT in the transplant population at our institute. This is a retrospective, single-center study which looked into the transplant database over a 25-year period. In patients with clinical suspicion of HIT, the 4T score was used, and laboratory tests such as ELISA HIT antibody and functional serotonin release assay, along with clinical manifestation of thromboembolic events were reviewed. Medical records of 2800 patients who underwent transplantation from January 1985 to December 2010 were reviewed. HIT antibody assay was performed in 262 patients from this group in which HIT was suspected. Of these, only 48 patients were HIT antibody positive along with moderate to high 4T score. The mean 4T score was 6.75 ± 1.4. Thrombotic complications were seen in 11 patients, with the highest in cardiac transplant recipients. Direct thrombin inhibitor (DTI) therapy was used in only eight patients who had thrombotic event. No other complications or mortality was reported in any of the HIT antibody-positive transplant patients. To our knowledge, this is the first study of its kind that has shown very low incidence of HIT in the transplant population except for in cardiac transplant recipients.

Allograft coronary artery thrombosis: a case report of early cardiac allograft left ventricular myocardial infarction

Cardiac allograft dysfunction is a major cause of morbidity and mortality in the early post-transplantation period. This is a critical condition that requires prompt diagnosis and management. We present the case of a 57-year-old man with ischemic cardiomyopathy who underwent cardiac transplantation and developed a rare case of coronary artery thrombosis in the setting of heparin-induced thrombocytopenia and thrombosis syndrome (HITTS) within the first 2 postoperative weeks. Transmural myocardial infarction (MI) was initially noted on cardiac magnetic resonance (CMR) imaging as regional left ventricular wall motion abnormalities and transmural hyperenhancement after gadolinium administration, prompting further evaluation of the coronary circulation with angiography.

Heparin induced thrombocytopenia: case presentation and review

Heparin Induced Thrombocytopenia (HIT) is an adverse effect of heparin therapy with possibly devastating consequences. We present a case of HIT Type II. An in-depth review of HIT is presented, examining the important clinical symptoms and diagnostic indicators. The treatment of HIT is then discussed, with an emphasis on current therapies. An extensive literature review has been performed to present a comprehensive review of the causes, pathophysiology and treatment of HIT.

Risks and complications of coronary angiography: a comprehensive review

Coronary angiography and heart catheterization are invaluable tests for the detection and quantification of coronary artery disease, identification of valvular and other structural abnormalities, and measurement of hemodynamic parameters. The risks and complications associated with these procedures relate to the patient’s concomitant conditions and to the skill and judgment of the operator. In this review, we examine in detail the major complications associated with invasive cardiac procedures and provide the reader with a comprehensive bibliography for advanced reading.

Perioperative management of partial face transplantation involving a heparin antibody-positive donor

Heparin-induced thrombocytopenia (HIT) is an immunologic condition that may lead to thrombosis. We present a case of face transplantation from a donor who had suffered a severe stroke, possibly from HIT, during cardiac surgery. The procedure was planned to include full heparinization. The anesthesia team was involved in the early planning phase and had detailed access to the donor's medical history; alternative anticoagulation for the donor and recipient was suggested so as to avoid a possible complication.

Danaparoid cross-reactivity with heparin-induced thrombocytopenia antibodies: report of 12 cases

PURPOSE

Danaparoid is a safe and effective drug for the treatment of heparin-induced thrombocytopenia (HIT). We describe an uncommon complication: danaparoid cross-reactivity with HIT antibodies.

DESIGN AND SETTING

A retrospective observational multicenter study on HIT was conducted in France. In this study concerning HIT patients treated with lepirudin, 12 patients were treated with lepirudin because danaparoid cross-reacted with the heparin-dependent antibodies.

RESULTS

Three groups of situations can be separated. In a first group, four patients received a short course of danaparoid until their initial functional HIT assay showed a cross-reactivity between danaparoid and HIT antibodies. One patient presented a fatal thrombotic complication but the relationship between this thrombotic complication and danaparoid cross-reactivity cannot be certain. In a second group, four patients received for 4 days at least a danaparoid treatment while the initial functional test did not show any danaparoid cross-reactivity. During danaparoid treatment, no significant increase of platelet count was observed and two patients presented a fatal thrombotic complication. In a third group, cross-reactivity between danaparoid and HIT antibodies was not checked before danaparoid therapy. During danaparoid treatment, no significant increase of platelet count was observed and the four patients developed a venous thromboembolic complication.

CONCLUSION

Absence of any increase in platelet count after 3 to 5 days of danaparoid therapy and/or the occurrence of a new thrombotic event should lead to danaparoid cross-reactivity suspicion. However, before attributing thrombotic complications to danaparoid cross-reactivity, it is crucial to verify that the patients received the recommended danaparoid dosage regimen.

Heparin-induced thrombocytopenia after liver transplantation

BACKGROUND

Unfractionated heparin sodium (UFH) or low-molecular weight heparin (LMWH) is used in anticoagulant protocols at several institutions to prevent thrombosis after liver transplantation. Heparin-induced thrombocytopenia (HIT) is an adverse immune-mediated reaction to heparin, resulting in platelet count decreases of more than 50%. The frequencies of HIT after liver transplantation and platelet factor 4/heparin-reactive antibody (HIT antibody) positivity in liver transplantation patients, however, are unknown.

PATIENTS AND METHODS

The 32 men and 20 women underwent living donor liver transplantation. We started LMWH (25 IU/kg/h) on postoperative day (POD) 1, switching to UFH (5000 U/d) on POD 2 or 3. The dose of UFH was changed according to the activated clotting time level. HIT antibody levels were measured the day before surgery and on POD 7 and 14. Platelet count was measured daily for 3 weeks.

RESULTS

The average platelet counts preoperatively, and on POD 7, 14, and 21 were 65, 88, 149, and 169 x 10(9)/L, respectively. Two patients developed hepatic artery thrombosis on POD 11 and 19, respectively, although they were HIT antibody-negative and their platelet counts were stable. In 2 other patients, the platelet count decreased suddenly from 107 x 10(9)/L on POD 4 to 65 x 10(9)/L on POD 6 and from 76 x 10(9)/L on POD 7 to 33 x 10(9)/L on POD 9, respectively. The heparin-induced platelet aggregation test was negative in these patients. The percentage of HIT antibody-positive patients was 0.5% preoperatively, 5.6% on POD 7, and 5.6% on POD 14. None of the subjects/patients developed UFH-related HIT.

CONCLUSIONS

In our series, the occurrence of HIT after liver transplantation was uncommon.

[Heparin-induced thrombocytopenia]

Hemorrhage is the most common and best-recognized complication of heparin treatment. However, a potentially more dangerous complication is the development of heparin-induced thrombocytopenia (HIT). All patients exposed to heparin, irrespective of the dose and route of administration, are at risk of developing HIT. It is due to the formation of antibodies against the heparin-platelet factor 4 complex, which cause secondary activation of platelets, coagulation and, finally, increased thrombin production. The main symptom is the sudden onset of thrombocytopenia involving a drop in the platelet count to less than 50% of the basal level, with or without the appearance of thrombotic complications some 5 to 14 days after the start of heparin therapy. Heparin-induced thrombocytopenia can be detected early in patients receiving heparin by monitoring the platelet count. Demonstration of heparin-dependent platelet activation using an antigen or functional assay confirms the clinical diagnosis. Once the diagnosis of HIT has been confirmed serologically or there is a high level of suspicion of HIT, heparin must be suspended and treatment with an alternative anticoagulant should be considered. This review contains a discussion of the diagnosis and treatment of this syndrome.

Reducing thrombotic complications in the perioperative setting: an update on heparin-induced thrombocytopenia

Heparins are widely used in the perioperative setting. Immune heparin-induced thrombocytopenia (HIT) is a serious, antibody-mediated complication of heparin therapy that occurs in approximately 0.5%-5% of patients treated with heparin for at least 5 days. An extremely prothrombotic disorder, HIT confers significant risks of thrombosis and devastating consequences on affected patients: approximately 38%-76% develop thrombosis, approximately 10% with thrombosis require limb amputation, and approximately 20%-30% die within a month. HIT antibodies are transient and typically disappear within 3 mo. In patients with lingering antibodies, however, re-exposure to heparin can be catastrophic. In the perioperative setting, heightened awareness is important for the prompt recognition, diagnosis, and treatment of HIT. HIT should be considered if the platelet count decreases 50% and/or thrombosis occurs 5-14 days after starting heparin, with other diagnoses excluded. On strong clinical suspicion of HIT, heparin should be discontinued and a parenteral alternative anticoagulant initiated, even before laboratory confirmation of HIT is obtained. Subsequent laboratory test results may help with the decision to continue with nonheparin therapy or switch back to heparin. Heparin avoidance in patients with current or previous HIT is feasible in most clinical situations, except perhaps in cardiovascular surgery. If the surgery cannot be delayed until HIT antibodies have disappeared, intraoperative alternative anticoagulation is recommended.

Heparin-induced Thrombocytopenia, a Prothrombotic Disease

Heparin-induced thrombocytopenia (HIT) is a serious, yet treatable prothrombotic disease that develops in approximately 0.5% to 5% of heparin-treated patients and dramatically increases their risk of thrombosis (odds ratio, 37). The antibodies that mediate HIT (ie, heparin-platelet factor 4 antibodies) occur more frequently than the overt disease itself, and, even in the absence of thrombocytopenia, are associated with increased thrombotic morbidity and mortality. HIT should be suspected whenever the platelet count drops more than 50% from baseline (or to <150 x 10(9)/L) beginning 5 to 14 days after starting heparin (or sooner if there was prior heparin exposure) or new thrombosis occurs during, or soon after heparin treatment, with other causes excluded. When HIT is strongly suspected, with or without complicating thrombosis, heparins should be discontinued, and a fast-acting, nonheparin alternative anticoagulant such as argatroban should be initiated immediately. With prompt recognition, diagnosis, and treatment of HIT, the clinical outcomes and health economic burdens of this prothrombotic disease are improved significantly.

Heparin-induced thrombocytopenia in the critical care setting: Diagnosis and management^

BACKGROUND

Thrombocytopenia is a common occurrence in critical illness, reported in up to 41% of patients. Systematic evaluation of thrombocytopenia in critical care is essential to accurate identification and management of the cause. Although sepsis and hemodilution are more common etiologies of thrombocytopenia in critical illness, heparin-induced thrombocytopenia (HIT) is one potential etiology that warrants consideration.

OBJECTIVE

This review will summarize the pathogenesis and clinical consequences of HIT, describe the diagnostic process, and review currently available treatment options.

DATA SOURCE

MEDLINE/PubMed search of all relevant primary and review articles.

DATA SYNTHESIS AND CONCLUSIONS

HIT is a clinicopathologic syndrome characterized by thrombocytopenia (>/=50% from baseline) that typically occurs between days 5 and 14 after initiation of heparin. This temporal profile suggests a possible diagnosis of HIT, which can be supported (or refuted) with a strong positive (or negative) laboratory test for HIT antibodies. When considering the diagnosis of HIT, critical care professionals should monitor platelet counts in patients who are at risk for HIT and carefully evaluate for, a) temporal features of the thrombocytopenia in relation to heparin exposure; b) severity of thrombocytopenia; c) clinical evidence for thrombosis; and d) alternative etiologies of thrombocytopenia. Due to its prothrombotic nature, early recognition of HIT and prompt substitution of heparin with a direct thrombin inhibitor (e.g., argatroban or lepirudin) or the heparinoid danaparoid (where available) reduces the risk of thromboembolic events, some of which may be life-threatening.

Evaluation of treatment with direct thrombin inhibitors in patients with heparin-induced thrombocytopenia

STUDY OBJECTIVE

To evaluate the efficacy, safety, and associated costs of anticoagulation with argatroban, bivalirudin, and lepirudin for managing patients with heparin-induced thrombocytopenia (HIT) or presumed HIT.

DESIGN

Retrospective medical record review.

SETTING

University-affiliated teaching hospital.

PATIENTS

Forty-two patients who were hospitalized between January 1 and December 31, 2004, and who were treated with bivalirudin, argatroban, or lepirudin for at least 24 hours.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the time to reach the desired goal for activated partial thromboplastin time (aPTT). Secondary outcomes were the number of aPTT measurements within the therapeutic range, costs, treatment duration, clinical outcomes, and adverse events. Of the 42 patients who met the inclusion criteria, 24 received bivalirudin, 13 received argatroban, and 5 received lepirudin. Patients receiving bivalirudin who reached therapeutic aPTTs attained them sooner than those receiving either argatroban or lepirudin (8.5 vs 14 and 24 hrs, respectively, p=0.124). Average percentage of therapeutic aPTTs/patient was greatest in the argatroban group (62%), followed by the bivalirudin (57%) and lepirudin (29%) groups (p=0.062). Average drug cost/day/patient was greater in the lepirudin group than the other groups, whereas average laboratory costs were similar among groups. Treatment duration was longer with argatroban than with bivalirudin or lepirudin. Bleeding rates were similar in the argatroban and bivalirudin groups, but higher than in the lepirudin group. A composite of clinical outcomes (deep vein thrombosis, nonfatal myocardial infarction, nonfatal stroke, limb amputation, and all-cause mortality) were similar among the three groups.

CONCLUSION

All three drugs were effective as anticoagulants for patients with HIT or presumed HIT. Based on average use and average wholesale price, bivalirudin cost less per day than the other two agents. Although not yet approved by the United States Food and Drug Administration for management of HIT, bivalirudin appears to be a viable treatment alternative for anticoagulation therapy.

Use of bivalirudin, a direct thrombin inhibitor, and its reversal with modified ultrafiltration during heart transplantation in a patient with heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is an increasingly common clinical finding in patients presenting for cardiac transplantation. Bivalrudin, a reversible direct thrombin inhibitor, is a molecular anti-coagulant with short half-life and the potential for removal by intraoperative hemofiltration. Herein we describe the dosing and intraoperative management of bivalrudin anti-coagulation in a patient undergoing urgent cardiac transplantation in the context of recently diagnosed HIT.

Heparin-induced thrombocytopenia in patients receiving mechanical circulatory support

OBJECTIVES

Patients receiving mechanical circulatory support are at risk for the development of heparin-induced thrombocytopenia due to the prolonged postoperative use of heparin. We evaluated their antibody status and outcome.

METHODS

Between 2003 and 2004, 115 patients received mechanical circulatory support for more than 5 days. Blood samples from postoperative day 7 were retrospectively analyzed for anti-platelet factor 4/heparin antibodies and heparin-induced platelet activation.

RESULTS

Overall, 12 (10.6%) patients had heparin-induced thrombocytopenia as defined by in vitro platelet activation, 28 (24.8%) had nonactivating antibodies, and 73 (64.6%) were classified as negative for antibodies. Patients positive for heparin-induced thrombocytopenia had the highest levels of anti-platelet factor 4/heparin immunoglobulin G antibodies. Freedom from thromboembolism was 33%, 33%, and 16% at 1, 3, and 6 months for positive patients, 77%, 68%, and 55% for negative patients (P < .001), and 70%, 53%, and 53% for patients with nonactivating antibodies (P = .068), respectively. The relative risk for thromboembolism in antibody positive patients peaked in the first month of support (odds ratio 7.46, P = .002). Independent risk factors for thromboembolic events included higher anti-platelet factor 4/heparin antibody titers, female gender, and higher fibrinogen levels.

CONCLUSION

Heparin-induced thrombocytopenia was more prevalent in patients receiving mechanical circulatory support than in other cardiac patients. Frequent antibody screening is recommended due to the increased risk of thromboembolism. Heparin alternatives should be subjected to clinical trials in these high-risk patients.

Prevalence of heparin-induced antibodies in patients with chronic renal failure undergoing hemodialysis

Heparin-induced thrombocytopenia (HIT) type II is a serious complication of heparin therapy. It presents initially as thrombocytopenia, and is associated with thrombosis in 20-50% of the cases. HIT is related to the presence of heparin-induced antibodies (HIA), which show specificity for the PF4-heparin (PF4-H) complex. The FcgammaRIIa receptor has been suggested to participate in the pathogenic mechanism of HIA. Since patients undergoing chronic hemodialysis (HD) are exposed repeatedly to heparin, we studied the prevalence of HIA and their eventual relationship with thrombocytopenia and/or thrombosis, and the possible participation of the FcgammaRIIa polymorphism. We studied 207 patients with chronic renal failure (CRF) undergoing HD. As a control we included 130 blood donors and 28 patients with CRF without HD. The HIA patients were studied with the use of a PF4-H ELISA. Additionally, in some positive cases for the previous test, a 14C- serotonin release assay (14C-SRA) was performed. The polymorphism FcgammaRIIa H/R131 was studied by polymerase chain reaction (PCR) with allele-specific primers. Thirty-seven patients (17.9%) undergoing HD presented with HIA. The majority of these antibodies were IgG, IgM, and IgA. The HIA investigated presented specificity against the PF4-H complex, but not against PF4 alone (P<0.001). Twelve out of 22 (54.5%) PF4-H antibodies were positive when tested with the 14C-SRA. The distribution of the FcgammaRIIa polymorphism in patients and healthy controls was 42.6% and 41.6% for H/H131, 41% and 48.9% for the H/R131 isoform, and 16.4% and 9.5% for the R/R131 isoform, respectively. No statistically significant difference in the FcgammaRIIa isoform distribution was found. Twenty-nine out of 156 patients (18.5%) presented thrombocytopenia, and 21/207 (12.4%) had thrombosis of the native vein arterio-venous fistula (AVF). We did not find any statistically significant between HIA and thrombocytopenia or thrombosis. An important proportion of patients with CRF undergoing HD developed HIA, but these cases were not associated with thrombocytopenia or thrombosis of AVF. The frequency of the FcgammaRIIa polymorphism did not statistically differ between HIT type II and normal controls.

Impact of intraoperative heparin on laparoscopic donor nephrectomy

PURPOSE

At many centers systemic heparinization is performed during laparoscopic donor nephrectomy because of concerns regarding graft thrombosis. However, no consensus exists in this regard. We evaluated the impact of intraoperative heparin on donor and recipient outcomes.

MATERIALS AND METHODS

Between September 2000 and February 2003, 79 consecutive patients underwent laparoscopic live donor left nephrectomy at our institution. They were sequentially divided into 2 groups, that is group 1-the initial 40 patients who intraoperatively received 5,000 IU heparin intravenously and group 2-subsequent patients who did not receive heparin. The 2 groups were well matched demographically. Data were compared using the paired 2-tailed t test.

RESULTS

The 2 donor groups were comparable in regard to mean blood loss (139 vs 179 cc, p = 0.59), intraoperative urine output (1.6 vs 1.6 l, p = 0.74), warm ischemia time (4 vs 4.2 minutes, p = 0.52), operative time (3.5 vs 3.5 hours, p = 0.97), and cold ischemia time (75 vs 82 minutes, p = 0.38). Complications occurred in 1 patient in group 1 (rhabdomyolysis induced acute renal failure) and in 2 in group 2 (chylous ascites and lumbar vein injury, respectively). No graft was lost due to vascular thrombosis in either group. Recipient immediate, early and delayed (6-month) graft function was comparable between the 2 groups. Acute rejection occurred in 5 recipients in group 1 and 1 in group 2. There was 1 recipient death per group at delayed followup.

CONCLUSIONS

Routine use of heparin during laparoscopic donor nephrectomy is not necessary. Because of its potential for causing intraoperative or early postoperative hemorrhage, we no longer routinely administer intraoperative heparin during laparoscopic donor nephrectomy at our institution.