# Presentation: 161246

## Spotlight Case December 2006

**Hidden Heparins: HIT Happens**

## Source and Credits

- This presentation is based on the December 2006 AHRQ WebM&M Spotlight Case
- See the full article at _[http://](http://webmm.ahrq.gov/)__[webmm.ahrq.gov](http://webmm.ahrq.gov/)_
- CME credit is available through the Web site
- Commentary by: **Patrick F. Fogarty, MD, **University of California, San Francisco
- Editor, AHRQ WebM&M: Robert Wachter, MD
- Spotlight Editor: Tracy Minichiello, MD
- Managing Editor: Erin Hartman, MS

## Objectives

*	**At the conclusion of this educational activity, participants should be able to:*
- Review presentation of heparin-induced thrombocytopenia (HIT)
- Discuss management of HIT
- Identify safeguards to avoid future exposure to heparin in individuals with HIT

## Case: Hidden Heparins

*	**A patient with a history of end-stage renal disease requiring hemodialysis was admitted for evaluation of non-healing ulcers and leukocytosis. She had been admitted one month prior for evaluation of peripheral artery disease. During that hospitalization, the patient underwent angioplasty of the right femoral artery, complicated by post-operative gangrene of the right foot requiring above-the-knee amputation.*

## Case: Hidden Heparins

*	**She also developed axillary vein thrombosis, and ultimately a diagnosis of heparin-induced thrombocytopenia (HIT) was made. She was treated with argatroban, and it was noted  on the chart that the patient should receive no further heparin.*

## Heparin-Induced Thrombocytopenia

- HIT occurs when heparin molecules stimulate formation of a pathogenic IgG antibody or “HIT antibody” which results in:
- platelet activation            thrombosis
- platelet clearance            thrombocytopenia
- More frequent with unfractionated heparin than low molecular weight heparin

## HIT: 4 T’s Diagnosis

**T**hrombocytopenia: platelet count drops to <150 x 109/L or by ≥ 50% below baseline
**T**iming: within 5-10 days of heparin exposure
**T**hrombosis: up to half of patients will develop  venous or arterial thrombosis
- o**T**her: no other etiology for thrombocytopenia

*Warkentin TE, Kelton JG. **N Eng J Med. 2001;344:1286-1292.**Warkentin TE, Kelton JG. Am J Med. 1996;101:502-507.*

## HIT: Diagnosis

- Laboratory diagnosis can confirm disease
- However, due to slow turnaround time, may not be helpful in initial diagnosis
- HIT antibody ELISA
- Serotonin-release assay

## HIT: Treatment

- Discontinue of all forms of heparin
- Initiate an alternative anticoagulant—direct thrombin inhibitor (DTI)
- Continue DTI until platelet count recovery has occurred and adequate anticoagulation with a coumarin derivative has been achieved

## Direct Thrombin Inhibitors

| AGENT  | DESCRIPTION  | INDICATION  | DOSING  | COMMENT  |
| --- | --- | --- | --- | --- |
| Argatroban | Synthetic direct thrombin inhibitor | Prophylaxis or treatment of HIT, including post-percutaneous coronary intervention | Obtain baseline PTT. Start continuous infusion at 2 μ/kg/min. Titrate to achieve PTT of 1.5 to 3 times the baseline value. Do not allow PTT to exceed 100 seconds, nor the infusion rate to exceed 10 μg/kg/min.  |  Patients with hepatic insufficiency: initial infusion rate =0.5 μg/kg/min.
 Increases the INR in warfarin-treated patients; interpret INR accordingly |
| Lepirudin (Refludan)  | Recombinant hirudin; direct thrombin inhibitor  | Treatment of HIT with associated thrombosis  | Obtain baseline PTT. Give slow bolus of 0.4 mg/kg then continuous infusion of 0.15 mg/kg/hr. Titrate to achieve PTT of 1.5 – 2.5 times baseline value. PTTs should be obtained 4 hours after starting the infusion and at least daily during treatment  |  Patients with renal insufficiency: initial bolus =0.2mg/kg
 Half of patients develop anti-drug antibodies that increase half-life; may necessitate a decrease in dose |
| Bivalirudin (Angiomax)  | Semi-synthetic derivative of hirudin; direct thrombin inhibitor  | Unstable angina in patients undergoing percutaneous transluminal coronary angioplasty  | 1.0 mg/kg IV bolus followed by 2.5 mg/kg/hr infusion for 4 hours; may continue infusion at 0.2 mg/kg/hr for up to 20 hours |  FDA-approved for concomitant use with aspirin
 Not approved for use in patients with HIT
 |

## HIT: Duration of Treatment

- HIT associated with thrombosis—minimum of 3-6 months
- HIT without thrombosis—risk of thrombosis persists for at least 30 days, with up to 50% of patients developing venous or arterial events; continue warfarin for 4 weeks

*Warkentin TE, Kelton JG. Am J Med. 1996;101:502-507.**Fogarty PF, Dunbar CE. Lippincott, Williams and Wilkins; 2005:256-257.**Alving BM. Blood. 2003;101:31-37. Epub 2002 Aug 15.*

## Case (cont.): Hidden Heparins

*	**On this admission, the patient was found to be tachycardic and hypotensive, with excoriations of the skin over the breast, abdomen, right thigh, and gluteal region. **Her labs were significant for leukocytosis of 17.1 x 10**9**/L and hypoalbuminemia of 2.4 gm/dl. The patient was started on antibiotics (amikacin and vancomycin). Blood cultures eventually grew candida, and amphotericin was added to her regimen. *

## Case (cont.): Hidden Heparins

*	**She appeared to be improving with a decrease in WBC to 10 x 10**9**/L. Over the next few days, however, she developed ischemia in her right hand, which eventually became cold and pulseless. It was also noted at this time that her platelet count had dropped since admission. On hospital day 8 the leukocyte count increased again, her respiratory status worsened, and she died, presumably from overwhelming sepsis.*

## Analysis of the Case

- Patient may have had complications of ongoing HIT when she was admitted
- Tachycardia and hypotension: PE
- Excoriations on skin: heparin-related skin reaction vs. warfarin induced skin necrosis
- Leukocytosis: due to inflammation from infarction

*Warkentin TE. Marcel Dekker; 2004:53-106. **Balestra B, et al. Eur J Haematol. 1994;53:61-63.**Hartman AR, et al. J Vasc Surg. 1988;7:781-784.*

## Heparin Related Skin Reaction in HIT

- Skin reaction
- 10%-20% of patients with HIT will develop skin lesions at injection site
- Painful erythematous plaques that may become necrotic

*Picture reprinted with permission from International **Journal of Dermatology. 2005;44:964-966.*

**Notes:**
Reprinted with permission. International Journal of Dermatology. 2005;44:964-966.

## Case (cont.): Hidden Heparins

*	**Autopsy revealed thrombi in the vessels of skin of breast and abdomen. A thorough review of the chart and hemodialysis records revealed that during this second hospitalization the patient had been repeatedly exposed to heparin during dialysis sessions, despite her recent history of HIT and the chart notes to avoid heparin.*

## Re-exposure to Heparin in Patients with HIT

- When measured by ELISA, the median duration of HIT antibody positivity is 85 days
- If antibodies present at time of re-challenge with heparin, patient can develop *rapid-onset *HIT with thrombocytopenia and thrombosis as soon as 24 hours after exposure

*Warkentin TE, Kelton JG. **N Eng J Med. 2001;344:1286-1292.**Warkentin TE. Marcel Dekker; 2004:53-106.**Boshkov LK, et al. Br J Haematol. 1993;84:322-328. *

## Re-exposure to Heparin in Patients with HIT

- Not generally recommended but may be considered in certain compelling clinical situations (in need of bypass, vascular surgery) with plan for _brief_ exposure
- Delay until at least 100 days after diagnosis of HIT (to allow antibodies to disappear)
- Document clearance of HIT antibody before re-exposing to heparin

*Warkentin TE, Kelton JG. **N Eng J Med. 2001;344:1286-1292.**Warkentin TE. Marcel Dekker; 2004:53-106.**Boshkov LK, et al. Br J Haematol. 1993;84:322-328. *

## HIT Associated with HeparinExposure from Flushes

- Small quantities of heparin (IV flush) can lead to HIT antibody formation or HIT itself
- Minor exposure via this route in patient with persistently circulating HIT antibodies can promote re-emergence or worsening of thrombocytopenia or thrombosis
- In most institutions, heparin for flushes does not require an order and is available on the floor

*See Notes for complete references.*

## Prevention of Re-exposure to Heparin in Patients with HIT

- Add heparin to patient’s allergy list and update hospital electronic profile to provide alerts
- Place “Heparin-Induced Thrombocytopenia: No Heparin” placard above patient’s bed
- Use electronic alerts if heparin ordered in heparin allergic patient

## Example of Electronic Alert

**	***Example of electronic alert upon attempting to order Heparin in a patient with Heparin allergy: WORx**** Software. *

## Consider switch to use of normal saline for flushing IV catheters to prevent inadvertent exposure from heparin not ordered through pharmacy
Meta-analysis shows no benefit of UFH vs. NS for patency of peripheral or central catheters
Heparin still used routinely for flushing dialysis circuit
HIT patients at risk not clearly labeled with heparin allergy

- Meta-analysis shows no benefit of UFH vs. NS for patency of peripheral or central catheters
- Heparin still used routinely for flushing dialysis circuit
- HIT patients at risk not clearly labeled with heparin allergy

*Warkentin TE, et al. Blood. 1998;92(suppl 1):91b. **Randolph AG, et al. BMJ. 1998;316:969-975. *

**Prevention of Re-exposure to Heparin in Patients with HIT**

## Take-Home Points

- HIT can occur in any patient after exposure to any amount of any type of heparin
- Clinical presentation of HIT can include isolated thrombocytopenia, isolated arterial or venous thrombosis or both
- Skin lesions in a thrombocytopenic patient exposed to heparin should raise suspicion for HIT

## Take-Home Points

- All patients with a prior history of HIT should have the medical and pharmacy record permanently amended to indicate the diagnosis
- Identify in-hospital use of heparin that circumvents a provider’s order
- Consider institutional policies that can lower the risk of heparin exposure by patients who have HIT