Hospital Acquired Venous Thromboembolism: A Preventability Assessment.

Background: The American Heart Association has a call to action to reduce hospital acquired venous thromboembolism (HA-VTE) by 20% by the year 2030. There is increasing recognition that quality improvement initiatives for VTE reduction should focus on reducing potentially preventable HA-VTE. The objective of our study was to determine what proportion of HA-VTE events are potentially preventable. Methods: This was a retrospective, single center pilot study of 50 patients with HA-VTE. Seven preventability factors were identified with a focus on VTE prescription and administration. Data were extracted through chart review using a systematic data collection form. The primary endpoint was the proportion of patients with potentially preventable HA-VTE. Descriptive statistics were used. Results: The median age was 66 years with an admission VTE risk level of moderate-high in 94%. Potentially preventable HA-VTE was found in 40% of cases. Missed doses occurred in 29.8% with a median of 2 missed doses and a range of 1 to 20. Patient refusal was the most common reason for missed doses in 71%. Delays in initiation occurred in 12.7%. Sixty percent of those on mechanical prophylaxis only had nonadherence. Conclusion: Forty percent of HA-VTE cases were potentially preventable. Missed doses was the most common preventability factor identified with patient refusal accounting for most missed doses.

Potential Dexamethasone-Direct Oral Anticoagulant Drug Interaction: Is This a Concern in COVID?

OBJECTIVE: To evaluate the literature on a potential dexamethasone-direct oral anticoagulant (DOAC) drug interaction and provide management considerations with COVID hypercoagulability. DATA SOURCES: A search of EMBASE, PubMed, and Google Scholar (January 1990 to May 2021), limited to the English language, using applicable search terms resulted in 137 articles, with 21 relevant articles included. Regulatory agency and clinical guidance documents were also reviewed. STUDY SELECTION AND DATA EXTRACTION: Included articles describe in vitro or in vivo animal or human data for dexamethasone induction of cytochrome P450 (CYP) 3A4 or P-glycoprotein (P-gp). DATA SYNTHESIS: Dexamethasone has the potential to interact with the DOACs via CYP3A4 and/or P-gp induction. Only apixaban and rivaroxaban have CYP3A4 metabolism. Dexamethasone can increase CYP3A4 activity by up to 70% and reduce the area under the concentration-time curve (AUC) of CYP3A4 substrates by >40%, which is consistent with criteria for a weak CYP inducer. In rodents, dexamethasone P-gp induction is associated with AUC reductions of 20% to 50%. Human data are lacking. RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE: Severe COVID-19 infection is associated with hypercoagulability. Although heparins are the preferred anticoagulants for hospitalized COVID-19 patients, DOACs are being utilized. Dexamethasone is recommended for hospitalized COVID-19 patients requiring supplemental oxygen. The concurrent use of dexamethasone and apixaban or rivaroxaban in such patients carries the potential for reduced anticoagulant effect during a state of heightened thrombotic risk. CONCLUSIONS: Concurrent use of dexamethasone and apixaban or rivaroxaban in hospitalized COVID-19 patients with laboratory evidence of COVID coagulopathy should be avoided until higher-quality data are available.

Serotonin-release assay-positive but platelet factor 4-dependent enzyme-immunoassay negative: HIT or not HIT?

IgG-specific and polyspecific PF4-dependent enzyme-immunoassays (EIAs) have exceptionally high sensitivity (≥99%) for diagnosis of heparin-induced thrombocytopenia (HIT), a drug reaction caused by platelet-activating antibodies detectable by serotonin-release assay (SRA). The IgG-specific EIAs are recommended for screening, as their high sensitivity is accompanied by relatively high specificity vis-à-vis polyspecific EIAs. We investigated the frequency of SRA-positive/EIA-negative (SRA+/EIA-) HIT, prompted by referral to our reference HIT laboratory of serial blood samples from a patient ("index case") with false-negative IgG-specific EIAs. Despite initial clinical suspicion for HIT, repeat negative IgG-specific EIAs prompted heparin resumption, which triggered recurrent thrombocytopenia and near-fatal cardiac arrest, indicating likely post-heparin HIT-associated anaphylactoid reaction. Further investigations revealed a strong-positive SRA, whether performed with heparin alone, PF4 alone, or PF4/heparin, with inhibition by Fc receptor-blocking monoclonal antibody (indicating IgG-mediated platelet activation); however, five different IgG-specific immunoassays yielded primarily negative (or weak-positive) results. To investigate the frequency of SRA+/EIA- HIT, we reviewed the laboratory and clinical features of patients with this serological profile during a 6-year period in which our reference laboratory investigated for HIT using both SRA and IgG-specific EIA. Although ~0.2% of 8546 patients had an SRA+/EIA- profile, further review of 15 such cases indicated clerical/laboratory misclassification or false-positive SRA in all, with no SRA+/EIA- HIT case identified. We conclude that while SRA+/EIA- HIT is possible-as shown by our index case-this clinical picture is exceptionally uncommon. Moreover, the requirement for a positive EIA is a useful quality control maneuver that reduces risk of reporting a false-positive SRA result.

Guidance for the practical management of the heparin anticoagulants in the treatment of venous thromboembolism.

Venous thromboembolism (VTE) is a serious and often fatal medical condition with an increasing incidence. Despite the changing landscape of VTE treatment with the introduction of the new direct oral anticoagulants many uncertainties remain regarding the optimal use of traditional parenteral agents. This manuscript, initiated by the Anticoagulation Forum, provides clinical guidance based on existing guidelines and consensus expert opinion where guidelines are lacking. This specific chapter addresses the practical management of heparins including low molecular weight heparins and fondaparinux. For each anticoagulant a list of the most common practice related questions were created. Each question was addressed using a brief focused literature review followed by a multidisciplinary consensus guidance recommendation. Issues addressed included initial anticoagulant dosing recommendations, recommended baseline laboratory monitoring, managing dose adjustments, evidence to support a relationship between laboratory tests and meaningful clinical outcomes, special patient populations including extremes of weight and renal impairment, duration of necessary parenteral therapy during the transition to oral therapy, candidates for outpatient treatment where appropriate and management of over-anticoagulation and adverse effects including bleeding and heparin induced thrombocytopenia. This article concludes with a concise table of clinical management questions and guidance recommendations to provide a quick reference for the practical management of heparin, low molecular weight heparin and fondaparinux.

Optimizing Anticoagulation Management Through the Use of a Hospital Engagement Network Metric for Inpatient Anticoagulant-Associated Hemorrhage.

BACKGROUND: The University HealthSystem Consortium (UHC), a national hospital engagement network (HEN), establishes health-system metrics to assess and improve quality of care. In 2012, a metric for inpatient anticoagulant hemorrhage was developed. The utility of this metric to improve anticoagulation care has not been assessed. OBJECTIVE: To identify opportunities to improve anticoagulation safety through the use of a HEN metric for inpatient anticoagulant-associated hemorrhage. METHODS: This was a single-center, retrospective, observational study of metric identified patients with presumed inpatient anticoagulant hemorrhage. Records were reviewed to confirm anticoagulant hemorrhage and identify bleed site and severity. A structured process was used to assess bleed preventability and subsequently identify opportunities for improving care. Each bleed was reviewed by 2 investigators. RESULTS: Anticoagulant hemorrhage was confirmed in 85.9% (61/71) with heparin infusion the most common anticoagulant. Patients were primarily medical, with a mean age of 72.7 ± 15 years. The most common bleed sites were gastrointestinal (24.6%) and retroperitoneal (21.3%). Major bleeding occurred in 60.7% (37/61). Anticoagulant hemorrhage was preventable in 18% (11/61) of cases with heparin protocol noncompliance the most common cause of a preventable bleed. Several opportunities for improving heparin infusion therapy were recognized and protocol changes were implemented. CONCLUSIONS: The UHC metric accurately captures inpatient anticoagulant-associated hemorrhage the majority of time. The UHC metric on anticoagulant-associated hemorrhage can be a useful part of a health system's overall plan for the safe use of anticoagulants in the hospital setting.

Dabigatran versus warfarin major bleeding in practice: an observational comparison of patient characteristics, management and outcomes in atrial fibrillation patients.

Data comparing the patient characteristics, management and outcomes for dabigatran versus warfarin major bleeding in the practice setting are limited. We performed a retrospective single health system study of atrial fibrillation patients with dabigatran or warfarin major bleeding from October 2010 through September 2012. Patient identification occurred through both an internal adverse event reporting system and a structured stepwise data filtering approach using the International Classification of Diseases diagnosis codes. Thirty-five dabigatran major bleeding patients were identified and compared to 70 warfarin major bleeding patients. Intracranial bleed occurred in 4.3 % of warfarin patients and 8.6 % of dabigatran patients. Dabigatran patients tended to be older (79.9 vs. 76 years) and were more likely to have a creatinine clearance of 15-30 mL/min (40 vs. 18.6 %, p = 0.02). Over one-third of dabigatran patients had an excessive dose based on renal function. More dabigatran patients required a procedure for bleed management (37.1 vs. 17.1 %, p = 0.03) and received a hemostatic agent for reversal (11.4 vs. 1.4 %, p = 0.04). Dabigatran patients were twice as likely to spend time in an ICU (45.7 vs. 27.1 %, p = 0.06), be placed in hospice/comfort care (14.3 vs. 7.1 %, p = 0.24), expire during hospitalization (14.3 vs. 7.1 %, p = 0.24), and expire within 30-days (22.9 vs. 11.4 %, p = 0.28). In a single hospital center practice setting, as compared to warfarin, patients with dabigatran major bleeding were more likely to be older, have renal impairment, require a procedure for bleed management and receive a hemostatic agent. Patients with dabigatran major bleeding had an excessive dose for renal function in more than one-third of cases.

Anticoagulant drug-drug interactions with cannabinoids: A systematic review.

This systematic review evaluates the extent to which the effect of anticoagulants may be altered in the presence of cannabinoids. The following databases were searched: EMBASE, PubMed, Web of Science, Scopus, PscycINFO, and CINAHL from database inception through May 2023. Search terms included cannabis AND anticoagulant AND drug interactions and related keywords. The major outcome was hemorrhage or thrombosis and if available the relative change in quantitative intensity of anticoagulation after cannabinoid exposure. The search generated 959 citations. After the removal of 440 duplicates, 519 citations were screened. Overall, with the exception of warfarin, evidence supporting an interaction between cannabinoids and anticoagulants is non-existent. Seven case reports evaluating an interaction with warfarin were reported. Cannabis doses involved were either extremely high (e.g., >260 mg/day of delta-9-tetrahydrocannabidiol [THC] or >600 mg/day of cannabidiol [CBD]) or were not known. Hemorrhage was identified in 14.2% (1/7) of reports and thrombosis in 0%. Quantitative anticoagulation levels were increased in patients on warfarin (elevated International Normalized Ratio [INR]) in six of seven cases. A maximum INR change was available in five of seven reports, ranging from +0.4 to +9.61. One report found no change in INR after 4 days of medical cannabis exposure. Another report outlined two separate episodes of INR elevation associated with bleeding requiring hospitalization and reversal after marijuana smoking. Four cases involved reduction in weekly warfarin dose ranging from 22% to 31%. The Drug Information Probability Score was calculated in six cases, with a score of probable for five cases and possible for one. Very low-quality data support a potential drug-drug interaction with warfarin and both THC and CBD. Clinician recognition of this potential interaction is important. Available evidence supports the need to conduct a drug interaction study between cannabinoids and warfarin to clarify the existence of an interaction.

Venous limb gangrene and fatal hemorrhage: adverse consequences of HIT "overdiagnosis" in a patient with antiphospholipid syndrome.

This unfortunate patient case highlights the problems with "overdiagnosis" of HIT. Despite "positive" tests for HIT antibodies, the low pretest probability for HIT and the known propensity of patients with APS to yield false-positive HIT antibody results suggests that the patient did not have a true diagnosis of HIT. Moreover, the early administration of warfarin and the choice of argatroban for parenteral anticoagulation when monitoring was hindered by a prolonged baseline aPTT likely play a key factor in the progression of UE DVT to VLG. Ironically, the problems of anticoagulant monitoring posed by the prolonged baseline aPTT likely contributed to the subsequent overanticoagulation and fatal pulmonary hemorrhage. With benefit of hindsight, avoiding the temptation to test for HIT in a low pretest probability situation, and treatment with either heparin using anti-factor Xa monitoring or with non-aPTT-monitored therapy such as LMWH or fondaparinux would likely have resulted in a more favorable clinical course.

Drug-induced thrombocytopenia in critically ill patients.

Thrombocytopenia occurs in 15% to 58% of intensive care unit patients. The incidence varies based upon patient population, timing and frequency of platelet monitoring, and definition of thrombocytopenia. Up to 25% of acutely ill patients develop drug-induced thrombocytopenia. When drug-induced thrombocytopenia is suspected, nondrug related causes must be evaluated and excluded. Establishing the diagnosis of drug-induced thrombocytopenia is challenging, as hundreds of medications have been implicated. Medications commonly associated with drug-induced thrombocytopenia include glycoprotein IIb/IIIa inhibitors, cinchona alkaloids, antibiotics, anticonvulsants, and heparin. Once the diagnosis is suspected, clinicians should identify the start date of medications to assess the timeline of development. The likelihood of each medication causing thrombocytopenia must be evaluated. The risk vs. benefit of discontinuing the suspected medication and availability of alternative medications must be assessed. The role of corticosteroids, immune globulin, and plasmapheresis is uncertain. Once the offending agent has been discontinued, the overall prognosis is excellent. In the case of suspected or confirmed heparin-induced thrombocytopenia, an alternative anticoagulant should be initiated. Drug-induced thrombocytopenia should be documented in the medical record and reported according to institutional and national standards. This review focuses on immune-mediated drug-induced thrombocytopenia from medications commonly utilized in the critically ill patient.

Recombinant factor VIIa to manage major bleeding from newer parenteral anticoagulants.

OBJECTIVE: To evaluate the use of recombinant factor VIIa (rFVIIa) to reverse major bleeding from newer parenteral anticoagulant therapy. DATA SOURCES: MEDLINE/PubMed was searched from January 2000 through December 2009 using the terms recombinant factor VIIa, rFVIIa, NovoSeven, enoxaparin, argatroban, fondaparinux, lepirudin, bivalirudin, idraparinux, nadroparin, hirudin, and desirudin. References of identified articles were reviewed. DATA SYNTHESIS: Data evaluating the role of rFVIIa to reverse major bleeding from newer parenteral anticoagulant therapy is limited to case reports and small laboratory investigations. Laboratory investigations suggest that rFVIIa may be effective in reversing the hemostatic effects of newer parenteral anticoagulants. In most case reports analyzed, standard interventions for bleeding (eg, fresh frozen plasma, packed red blood cells) were attempted prior to using rFVIIa. Sixteen published cases describe the use of rFVIIa to reverse major bleeding from low-molecular-weight heparins, synthetic pentasaccharides, and direct thrombin inhibitors. Initial doses ranged from 20 to 120 mug/kg. rFVIIa was considered effective or partially effective based upon clinical response in 13 cases. Use was not effective in 3 cases because of a thrombotic event, no change in hemostasis, and death from bleeding complications. As thrombosis is the major safety concern, an individualized risk-benefit assessment is required prior to the use of rFVIIa therapy to restore hemostasis. CONCLUSIONS: rFVIIa may be considered to manage major refractory bleeding from newer parenteral anticoagulant agents when the benefit is thought to outweigh the thrombotic risk.

Timing of Initiation of Oral Anticoagulation after Acute Ischemic Stroke in Patients with Atrial Fibrillation.

Patients with atrial fibrillation (AF) who suffer an acute ischemic stroke are at risk for both hemorrhagic transformation and recurrent ischemic stroke in the acute post-stroke period. Oral anticoagulants are recommended for secondary stroke prevention in patients with AF. The optimal time to initiate anticoagulant therapy after acute ischemic stroke in patients with AF is uncertain. There is concern that early initiation increases the risk of hemorrhagic transformation, whereas delayed initiation leaves the patient at risk for recurrent ischemic stroke. In this article, we provide a review of the risk of hemorrhagic transformation of acute ischemic stroke as well as review the literature and major guidelines addressing the timing of anticoagulation initiation after an acute ischemic stroke in patients with AF. Relevant articles published from 1990 to the present were identified using the PubMed and Embase databases. The majority of available literature is observational data. Large ischemic lesions, cerebral microbleeds, thrombolytic therapy, and other clinical factors may increase the risk of hemorrhagic transformation of an acute ischemic stroke. Parenteral anticoagulation within 48 hours is associated with an increased risk of hemorrhagic transformation and is not recommended. Insufficient data exist to support the safety of routine oral anticoagulant (direct oral anticoagulants or warfarin) initiation within 48 hours of an acute ischemic stroke. Direct oral anticoagulant initiation within 2 days of an acute ischemic stroke is associated with a 5% rate of hemorrhagic transformation. Infarct size and presence of hemorrhage are important factors in identifying the optimal time to initiation and should guide decisions when available. A recommended framework for patient decision making is provided. Randomized controlled trials in this area are needed to identify the optimal timing of anticoagulation initiation, and such trials are under way.

American Society of Hematology 2019 guidelines for management of venous thromboembolism: prevention of venous thromboembolism in surgical hospitalized patients.

BACKGROUND: Venous thromboembolism (VTE) is a common source of perioperative morbidity and mortality. OBJECTIVE: These evidence-based guidelines from the American Society of Hematology (ASH) intend to support decision making about preventing VTE in patients undergoing surgery. METHODS: ASH formed a multidisciplinary guideline panel balanced to minimize bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline-development process, including performing systematic reviews. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess evidence and make recommendations, which were subject to public comment. RESULTS: The panel agreed on 30 recommendations, including for major surgery in general (n = 8), orthopedic surgery (n = 7), major general surgery (n = 3), major neurosurgical procedures (n = 2), urological surgery (n = 4), cardiac surgery and major vascular surgery (n = 2), major trauma (n = 2), and major gynecological surgery (n = 2). CONCLUSIONS: For patients undergoing major surgery in general, the panel made conditional recommendations for mechanical prophylaxis over no prophylaxis, for pneumatic compression prophylaxis over graduated compression stockings, and against inferior vena cava filters. In patients undergoing total hip or total knee arthroplasty, conditional recommendations included using either aspirin or anticoagulants, as well as for a direct oral anticoagulant over low-molecular-weight heparin (LMWH). For major general surgery, the panel suggested pharmacological prophylaxis over no prophylaxis, using LMWH or unfractionated heparin. For major neurosurgery, transurethral resection of the prostate, or radical prostatectomy, the panel suggested against pharmacological prophylaxis. For major trauma surgery or major gynecological surgery, the panel suggested pharmacological prophylaxis over no prophylaxis.

The financial impact of heparin-induced thrombocytopenia.

BACKGROUND: Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction that increases patient morbidity and mortality. The financial impact of HIT to an institution is thought to be significant. The objective of this study was to evaluate the financial impact of HIT. METHODS: A case-control study was employed. Case patients were identified as newly diagnosed HIT patients. Control subjects were matched by diagnosis-related group, primary diagnosis code, primary procedure code, and hospital admission date. The financial/decision support database of the hospital was queried to identify the matched control subjects, total cost, and reimbursement. The determination of financial impact included the total profit or (total loss) and the backfill effect (ie, the lost operating margin resulting from increased length of stay). Length of stay and mortality were compared. RESULTS: Data from 22 case patients and 255 control subjects were analyzed. On average, HIT case patients incurred a financial loss of $14,387 per patient and an increase in length of stay of 14.5 days. When confining the analysis to only Medicare case patients (n = 17) and Medicare control subjects, case patients incurred a financial loss of $20,170 per case and an increase in length of stay of 15.8 days. Depending on the occupancy rate of the institution, additional financial loss could result from the backfill effect. Mortality was not significantly affected. CONCLUSION: For an institution that sees 50 new cases of HIT per year, the projected annual financial impact ranges from approximately $700,000 to $1 million. Institutions with high bed occupancy rates may see an additional loss from the backfill effect.

Quality experiential education.

The 2007 Accreditation Council for Pharmacy Education (ACPE) Accreditation Standards and Guidelines for the Professional Program in Pharmacy delineate new expectations for experiential education within curricula and include guidance on the development and conduct of Pharmacy Practice Experiences. The American College of Clinical Pharmacy (ACCP) Educational Affairs Subcommittee C developed a position statement to further delineate the views of ACCP on factors necessary to meet contemporary standards for doctoral education in pharmacy and to provide guidance to our membership on how to implement the new standards. This White Paper provides explanation and supporting documentation for positions on quantitative and qualitative aspects of experiential education, as well as requirements for practice sites, preceptor roles, qualification, credentialing, and development and assessment of student performance.

Characteristics, Management, and Outcomes of Patients with Atrial Fibrillation Experiencing a Major Bleeding Event While on Rivaroxaban.

Rivaroxaban, the first oral direct factor Xa inhibitor, was approved for stroke prevention in nonvalvular atrial fibrillation in 2011. Limited data are available regarding major bleeding in a clinical practice setting. The purpose of this study is to describe the patient characteristics, management, and outcomes of major bleeding events in patients receiving rivaroxaban for atrial fibrillation. This retrospective, single health system study identified patients with rivaroxaban having a major bleeding event between July 2011 and June 2014. Patients were identified through adverse event reporting or by cross-referencing rivaroxaban with International Classification of Diseases, Ninth Revision diagnosis codes for atrial fibrillation and hemorrhage, with and without transfusion. A total of 60 patients were identified. The mean age of patients was 80.3 ± 7.4 years. The most common bleed sites were gastrointestinal (63.3%) and intracranial (26.7%). Higher dose than recommended based on renal function was present in 35% of patients and concurrent antiplatelet therapy occurred in 70%. Activated prothrombin complex concentrate was utilized in 30% of patients and recombinant factor VIIa in 6.7%. A procedure or surgery was performed for bleed management in 10 patients. Anticoagulation was held at discharge in 76% of patients. A total of 6 patients died during hospital admission, 5 of whom experienced an intracranial hemorrhage. In conclusion, patients experiencing a rivaroxaban major bleeding event were elderly, often renally impaired, and receiving concurrent antiplatelet therapy. In-hospital mortality was 10%. The majority of patients (76%) had anticoagulation therapy held at discharge.

Major bleeding with apixaban in atrial fibrillation: patient characteristics, management, and outcomes.

OBJECTIVES: To identify patient characteristics, bleed management, and bleed outcomes in patients experiencing an apixaban major bleeding event and to identify opportunities to improve the safe use of apixaban. METHODS: This retrospective single health-system study identified apixaban patients experiencing a major bleeding event between January 2013 and May 2016 through electronic medical record review. Patient characteristics, bleed management, and outcomes were extracted in those with a confirmed major bleed assessed by the International Society on Thrombosis and Haemostasis criteria. RESULTS: Fifty major bleeding events occurred in 49 patients (79 ± 9.8 years). Patient characteristics included history of hypertension (94%), anemia (68%), and concomitant antiplatelet use (68%). Gastrointestinal bleeding occurred in 72% of patients and intracranial hemorrhage in 14% of patients. Packed red blood cells (PRBCs) were utilized in 82% of patients and reversal agents were administered to 6% of patients. Mortality during the hospital admission for the bleed was 0%. Anticoagulation was held at discharge in 64% of patients and remained held at 30 days in the majority of patients. Of those on concurrent aspirin therapy, an appropriate indication was not found in 64.7% of patients. CONCLUSIONS: Patients with major bleeding were elderly and frequently on inappropriate concomitant antiplatelet therapy. The majority of patients were managed with PRBC transfusion. More than half of patients had anticoagulation therapy held at discharge. Concerns with prescribing and patient management were identified leading to recommendations for improving the safe use of apixaban therapy.

The incidence of recognized heparin-induced thrombocytopenia in a large, tertiary care teaching hospital.

BACKGROUND: Heparin-induced thrombocytopenia (HIT) is estimated to occur in up to 5% of patients receiving unfractionated heparin. The goal was to determine the incidence of HIT within our 1,061-bed tertiary care institution. METHODS: A retrospective review of three hospital database systems (ie, admission, pharmacy, and laboratory) was undertaken for a 1-year period ending in March 2004. The pharmacy database was queried to identify patients who received heparin and those who received a direct thrombin inhibitor (DTI). The medical records of patients receiving a DTI were reviewed to categorize the indication for DTI therapy. The laboratory system database was queried to retrieve heparin platelet factor 4 immunoassay results. RESULTS: A total of 58,814 patient admissions occurred with an estimated 24,068 patients being exposed to unfractionated heparin. DTI therapy was administered to 133 patients. Of these, 49 new HIT cases and 15 cases of suspected HIT (unconfirmed) were identified. The overall incidence of recognized new HIT was 0.2%. New HIT occurred in 0.76% of patients receiving therapeutic-dose IV heparin and in < 0.1% of patients receiving antithrombotic prophylaxis (subcutaneous heparin). Forty-nine percent of all new HIT cases were in coronary artery bypass and/or valve replacement surgery patients, while no cases were identified in hip/knee arthroplasty patients. CONCLUSIONS: The incidence of recognized HIT in a large teaching institution was 0.2%, with a 0.76% incidence in those patients receiving therapeutic-dose IV heparin. The low incidence likely reflects a brief duration of heparin exposure for many patients. Approximately half of all new HIT cases were recognized in the cardiovascular surgery population.