Current Limitations of the Assessment of Haemostasis in Adult Extracorporeal Membrane Oxygenation Patients and the Role of Point-of-Care Testing

Haemostatic perturbations are commonly seen in extracorporeal membrane oxygenation (ECMO) patients and remain a clinical challenge, contributing significantly to morbidity and mortality. The approach to anticoagulation monitoring and the management of bleeding varies considerably across ECMO centres. Routine laboratory tests have their limitations in terms of turnaround time and specificity of information provided. Newer point-of-care testing (POCT) for coagulation may overcome these issues, as it provides information about the entire coagulation pathway from clot initiation to lysis. It is also possible to obtain qualitative information on platelet function from these tests. Furthermore, the ability to incorporate these results into a goal-directed algorithm to manage bleeding with targeted transfusion strategies appears particularly attractive and cost effective. Further studies are required to evaluate the utility of POCT to optimise bleeding and anticoagulation management in these complex patients.

Stent thrombosis caused by metal allergy complicated by protein S deficiency and heparin-induced thrombocytopenia: a case report and review of the literature

A 43-year-old woman recipient of a bare metal coronary stent during an acute anterior myocardial infarction was repeatedly hospitalized with recurrent stent thrombosis (ST) over the following 3 years. Emergent coronary angiography showed a thrombus in the in-stent segment of the proximal left anterior descending artery. We repeatedly aspirated the thrombus, which immediately reformed multiple times. The discontinuation of heparin and administration of thrombolytics and argatroban, followed by repeated balloon dilatations, ended the formation of new thrombi. The patient was found to be allergic to nickel, protein S deficient and carrier of heparin-induced thrombocytopenia antibody. We discuss this case in the context of a) literature pertaining to acute coronary syndromes in the young, and b) the detailed investigations needed to identify thrombotic risk factors. Steroids may be effective to prevent recurrent ST caused by stent allergy.

HIT heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a significant complication of heparin therapy. The NP is in a pivotal position to identify patients at greater risk for HIT and promptly diagnose and intervene to prevent serious thrombotic complications.

Lower extremity manifestations and treatment of heparin-induced thrombocytopenia syndromes: a cohort study

Heparin-induced thrombocytopenia (HIT) and heparin-induced thrombocytopenia with thrombosis (HITT) syndromes are the result of an adverse reaction to heparin that results in a spectrum of laboratory and end-organ manifestations secondary to thrombosis of both arterial and venous small and large vessels. HITT most often manifests in the extremities as acral ischemia and necrosis, with a spectrum of severity. The lower extremity surgical patient is at risk for deep venous thrombosis, and when exposed to heparin products, is also at risk for the development of a heparin-induced thrombocytopenic syndrome. This article reports on a cohort of patients from a tertiary referral lower extremity reconstruction practice with the HIT/HITT syndromes, with an analysis of the frequency, medical characteristics, clinical settings, lower extremity manifestations, management, and outcomes of patients with HIT/HITT.).

Low-molecular-weight heparin for prevention of thrombosis: inverted role

BACKGROUND

Heparin induced thrombosis (HIT) after low-molecular-weight (LMWH) administration for thrombosis prevention is a limb and life threatening condition.

METHODS

Two previously healthy individuals, with nonviable forearm amputation and knee osteoarthritis, suffered from multiple arterial thromboses (>2 sites each) after postoperative administration of LMWH.

RESULTS

Both patients suffered from thrombocytopenia on the first postoperative days (4-7) and had signs of arterial occlusions on the 9th and 10th postoperative days. The patient with the initially successful forearm replantation was finally amputated below the elbow, whereas the lower extremity of the patient with total knee arthroplasty and contralateral femoral artery occlusion was salvaged with foot fingers amputation only.

CONCLUSIONS

Early recognition of the syndrome by monitoring daily platelet counts during heparin therapy is essential. In case of postheparin (LMWH or unfractionated) platelet decrease, heparin administration should be ceased after emergency testing for heparin induced antibodies. When HIT syndrome is confirmed to have occurred, heparin/LMWH must be replaced with thrombin-specific inhibitors.

A prospective study of the prevalence of heparin-induced antibodies and other associated thromboembolic risk factors in pediatric patients undergoing hemodialysis

Heparin, which is used at high doses in hemodialysis patients, may induce antibodies favoring thromboembolic complications. We prospectively investigated the prevalence of heparin-induced platelet-reactive antibodies in a cohort of 38 pediatric hemodialysis patients, by means of heparin/platelet factor 4 (H/PF4) ELISA and heparin-induced platelet activation assay (HIPA). We also assessed other acquired and congenital hypercoagulable states. Heparin-induced antibodies were detected in 13 and 21% of patients with HIPA and ELISA, respectively. Anti-H/PF4 antibodies were negatively correlated with the number of hemodialysis sessions. These antibodies disappeared after a median time of 6 months despite continuing heparin treatment. The prevalence of antiphospholipid antibodies was 21% (anticardiolipin 10.5%, anti-beta2GPI 13%, and lupus anticoagulant 5%). Blood levels of homocysteine, factor VIII, and fibrinogen were significantly higher and factor II levels were significantly lower in hemodialysis patients than in controls, whereas factor VII, factor IX, and natural coagulation inhibitor levels were similar in patients and controls. Overall, 26 of 38 patients had at least one biomarker of hypercoagulability, but only 1 patient, without anti-H/PF4 antibodies, presented with thrombosis. In conclusion, heparin induces the transient production of anti-H/PF4 antibodies in children undergoing hemodialysis, but other abnormalities probably contribute to hypercoagulability. These findings may help to improve the diagnosis and management of thrombotic events in hemodialysis patients.

Thrombocytopenia following heparin flush

A total of 23 patients who developed heparin-induced thrombocytopenia following exposure to heparin solely due to intravascular catheter or filter flush were the subjects of prospective studies of argatroban therapy. Heparin doses were 10-13,000 U, with a mean exposure of 8+/-4 days. Following heparin-induced thrombocytopenia diagnosis and heparin cessation, 13 patients received argatroban (mean dose of 1.8+/-1.1 mg/kg/min for 5.5+/-3.9 days), achieving activated partial thromboplastin times of 63+/-23 seconds, and 10 historical control patients received no direct thrombin inhibitors. Platelet count recovered to a mean of 207+/-153 x 10(9)/L (n=12) after 5.5+/-3.9 days of argatroban therapy and to a mean of 127+/-63 x 10(9)/L (n=8) 5 days after baseline in the control group. A composite end point of death, amputation, or new thrombosis within 37 days occurred in five (38.5%) argatroban-treated patients and four (40%) controls. Death was the most common untoward outcome (approximately 30% of each group). No argatroban-treated patient and two (20%) control patients experienced new thrombosis. Major bleeding was comparable between groups. Heparin-induced thrombocytopenia can occur following minimal heparin exposure, including heparin flushes; in these patients, argatroban provides effective alternative anticoagulation as compared with historical controls.

Homonymous Hemianopia Caused by Occipital Lobe Infarction in Heparin-Induced Thrombocytopenia and Thrombosis Syndrome

A 73-year-old woman developed mental confusion and finger pain after treatment with enoxaparin following arthroplasty. A platelet count was 163,000/microL. Because digital embolism was suspected, she was emergently treated with heparin and recombinant tissue plasminogen activator (rTPA). During rTPA infusion, she reported sudden hemifield loss, so the infusion was aborted. Brain CT disclosed a non-hemorrhagic occipital infarct. Platelets had fallen to 63,000 over eight days, and antibodies against a complex of heparin and platelet factor 4 were detected. These findings led to the diagnosis of heparin-induced thrombocytopenia and thrombosis syndrome (HITTS), an immune-mediated disorder in which venous and arterial thromboses occur. Right lower extremity deep venous thromboses were later diagnosed, and an MRI disclosed multiple cerebral infarcts of recent onset but different ages. Previous reports have documented brain arterial strokes in HITTS, mostly in the distribution of the middle cerebral artery, but clinical documentation is sparse, and there have been no imaging reports. This is the first report to document the clinical and imaging features of a HITTS stroke and the first to describe a stroke presumptively caused by a low molecular weight heparin. It emphasizes that HITTS may cause stroke even when the platelet count is normal. Diagnosis of HITTS should prompt immediate cessation of heparin treatment and substitution of a direct thrombin inhibitor or fondaparinux.

Risk of anaphylaxis after reexposure to intravenous lepirudin in patients with current or past heparin-induced thrombocytopenia

OBJECTIVE

To retrospectively assess the signs and symptoms indicative of adverse reactions to repeated exposures to lepirudin in patients with heparin-induced thrombocytopenia who received at least 2 courses of lepirudin therapy.

PATIENTS AND METHODS

Medical records were retrospectively assessed from adult patients who received at least 2 courses of lepirudin therapy separated by at least 1 week between January 1999 and June 2002 at The Cleveland Clinic, Cleveland, Ohio. We evaluated the list of 289 low-level terms for possible signs and symptoms of anaphylactic reactions In the medical dictionary for regulatory activities as well as patient vital signs to detect manifestations of immediate hypersensitivity reactions. Vital signs from the day before initiation of lepirudin therapy were compared with those from days 1 and 2 after exposure.

RESULTS

No cases of anaphylaxis or allergic reaction related to lepirudin administration were identified among 43 adult patients. On day 1 of lepirudin, 10 patients had lower systolic blood pressures (by > or =20 mm Hg) than pre-lepirudin values, and 4 patients had systolic blood pressures of less than 100 mm Hg.

CONCLUSIONS

Isolated asymptomatic decreases in blood pressure after patient reexposure to lepirudin most likely do not reflect anaphylaxis due to lepirudin. We believe that isolated and uncommon cases of anaphylaxis temporally related to lepirudin exposure should not preclude its use in patients with heparin-induced thrombocytopenia and past lepirudin exposure.

Alternatives to Heparin Infusion

This article offers an overview of the pathophysiology, diagnosis, and treatment of heparin-induced thrombocytopenia (HIT). This disorder is an immune-mediated reduction of platelets with subsequently increased generation of thrombin and increased risk of arterial and venous thrombosis. Heparin-induced thrombocytopenia can occur as an isolated incident or with acute thrombosis (HIT with thrombosis syndrome [HITTS]). Proper recognition, cessation of all forms of heparin (and compounds that cross-react with heparin), and rapid initiation of nonheparin anticoagulation are essential steps in reducing the risk of death, limb amputation, and new thrombotic events. Current alternatives to heparin are reviewed.

Stroke in patients with heparin-induced thrombocytopenia and the effect of argatroban therapy

OBJECTIVE

To investigate the frequency, mortality rate, and characteristics of stroke in heparin-induced thrombocytopenia and the effect of argatroban therapy in that setting.

DESIGN

Retrospective analysis of two prospective studies of argatroban therapy in heparin-induced thrombocytopenia.

SETTING

Hospitalized care.

PATIENTS

Patients were 960 patients with heparin-induced thrombocytopenia (767 argatroban-treated patients, 193 historical controls).

INTERVENTIONS

Argatroban 2 microg x kg x min, adjusted to achieve activated partial thromboplastin times 1.5-3 times baseline

MEASUREMENTS AND MAIN RESULTS

Case records were reviewed to identify patients with stroke present at or within 37 days of study entry and to assess 37-day outcomes. Stroke occurred in 30 (3.1%) patients (stroke at entry, n = 9; new stroke during follow-up, n = 24; more than one stroke, n = 4). By logistic regression with treatment, protocol, age, and gender as covariates, females were significantly more likely to suffer stroke (odds ratio, 2.48; 95% confidence interval, 1.11-5.53; p =.026) and stroke-associated mortality (odds ratio, 4.10; 95% CI, 1.12-15.01; p =.033), and argatroban-treated patients had significantly reduced odds, vs. control, of new stroke (odds ratio, 0.31; 95% confidence interval, 0.10-0.96; p =.041) and stroke-associated mortality (odds ratio, 0.18; 95% confidence interval, 0.03-0.92; p =.039). Stroke (odds ratio, 3.66; 95% confidence interval, 1.73-7.73; p <.001) and age (odds ratio per year, 1.017; 95% confidence interval, 1.004-1.029; p =.008) were significant predictors of all-cause death. In the argatroban group, baseline platelet counts were significantly less in patients with, vs. without, stroke (medians, 42 x 10/L vs. 72 x 10/L; p =.006). Of 35 stroke events, 33 (94%) were ischemic and two (6%) were hemorrhagic (one per group, none during argatroban infusion); 30 (86%) were present at or within 13 days of entry.

CONCLUSIONS

Stroke, particularly ischemic stroke, is common in heparin-induced thrombocytopenia and significantly increases mortality risk. Stroke in heparin-induced thrombocytopenia occurs most often in females, in patients with more severe thrombocytopenia, and within 2 wks of heparin-induced thrombocytopenia presentation. Argatroban therapy vs. control significantly reduces the likelihood of new stroke and stroke-associated mortality in heparin-induced thrombocytopenia without increasing intracranial hemorrhage.

The treatment and prevention of deep vein thrombosis in the preoperative management of patients who have neurologic diseases

All patients with neurologic diseases should receive perioperative VTE prophylaxis. The choice of mechanical, pharmacologic, or combined modalities of prophylaxis depends on both the underlying risk factors and surgical VTE risks. Prophylaxis and treatment options must be individualized to the patient. Prevention of VTE will help minimize the need for therapeutic treatment. Options for treatment include both inpatient and outpatient regimens using UFH or LMWH. In patients with an absolute or relative contraindication to anticoagulation, an IVC filter is an appropriate management strategy. Perioperative bridging therapy should be considered in patients with high or moderate risks for recurrent VTE.

Heparin-induced thrombocytopenia--recognition and treatment

Heparin, an important agent for the prophylaxis and treatment of venous and arterial thromboembolism, also can cause heparin-induced thrombocytopenia (HIT). This medication-induced immune-mediated syndrome is characterized by thrombocytopenia and life- or limb-threatening thrombotic events. The initial presentation of HIT is a decrease in platelet count with or without thrombosis. Heparin-induced thrombocytopenia frequently is overlooked in hospital settings, and it must be distinguished from other causes of thrombocytopenia. New therapies include the use of direct thrombin inhibitors argatroban and hirudin.

Respiratory pharmacotherapy in emergency and critical care medicine

Successful pharmacologic management of most respiratory diseases is possible. All moderately to severely affected animals benefit from rest and supplemental oxygen. Careful identification of the underlying cause as well as an understanding of the pathophysiology behind various diseases is essential to successful patient outcome.

New Treatment Options for Heparin-Induced Thrombocytopenia

Heparin, in various forms, is used in a variety of conditions including prophylaxis and treatment of thromboembolic disorders. Although the most common adverse effect related to the use of heparin is bleeding, heparin-induced thrombocytopenia (HIT) can also occur. Two types of HIT exist, HIT type I and type II. HIT type I is a mild and self-limiting disease in which the patient’s platelet count may decrease slightly but will recover with continued treatment. This is in contrast to HIT type II, which may lead to potentially devastating complications. Patients with HIT type II are at increased risk for thromboembolic complications that are mediated through autoimmune reactions and therefore require anticoagulation with danaparoid or one of the direct thrombin inhibitors, including lepirudin, argatroban, or bivalirudin. Limited data are available on the use of these agents in special populations including patients who are pregnant or those undergoing procedures such as percutaneous coronary intervention, cardiopulmonary bypass and dialysis, and pregnancy. Future therapies may include the use of unfractionated heparin in combination with glycoprotein IIb/IIIa inhibitors during cardiopulmonary bypass.