Stop the Bleeding! An Update on the Prevention and
Transcription
Stop the Bleeding! An Update on the Prevention and
Vol. XV Issue 2 Mar.Apr 2005 Stop the Bleeding! An Update on the Prevention and Treatment of Intracerebral Hemorrhage Intracerebral hemorrhage (ICH) is the most fatal form of stroke. Mortality at 30 days can exceed 50% while, among survivors, as few as 20% live independently at 6 months (Figure 1).1, 2 ICH accounts for 10% to 15% of all strokes in the United States, affecting approximately 65,000 people each year, with higher figures in Asia where 20% to 40% of strokes may be due to ICH.3 While effective strategies have been sorely lacking for treating ICH when it occurs, as well as preventing it in patients at risk, recent exciting developments point the way to novel interventions that may soon offer hope. Epidemiologic studies suggest the majority of primary ICH cases are the manifestation of two forms of chronic small vessel disease, hypertensive vasculopathy and cerebral amyloid angiopathy (CAA). Acute vascular injuries, such as those associated with malignant hypertension, account for a smaller proportion, while secondary ICH can result from tumors, vascular malformations, and the occasional ruptured aneurysm. Hemorrhage location within the brain often provides clues to the underlying cause, with longstanding hypertension causing ICH in the basal ganglia, thalamus, brain stem, and cerebellum, and CAA causing lobar and rarely cerebellar ICH (Figure 2).4-8 S m a l l Ve s s e l D i s e a s e a n d I C H Longstanding hypertension causes lipohyalinosis of small, deep penetrating arteries, the rupture of which results most commonly in deep hemispheric or brain stem hemorrhage.4 Occasionally, lobar hemorrhages also may occur in association with hypertension. Figure 1. Outcome at 3 months for 435 patients with supratentorial ICH (333 unrelated to warfarin and 102 with warfarin-related ICH) admitted to Massachusetts General Hospital. Mortality is reported as a percentage of the entire cohort. There were no survivors in persistent vegetative state (Glasgow Outcome Scale (GOS) score. 2. Reprinted from Arch Intern Med 2004; 164;880-884. STROKE Clinical Updates © National Stroke Association majority of anticoagulant-related ICH occurs when the INR is 2.0 to 3.0,18 suggesting that factors other than intensity of anticoagulation predispose to hemorrhage. The current leading hypothesis is that, in most cases, warfarin does not affect hemorrhage occurrence, but rather hemorrhage severity. Thus, a hemorrhage that might remain subclinical in the absence of anticoagulation enlarges to become a devastating ICH in an anticoagulated patient.16 The identification of CAA as a risk factor for warfarinrelated hemorrhages in the lobar brain regions22 supports this hypothesis, as does the observation that leukoaraiosis, a neuroimaging manifestation of small vessel disease, is associated with a higher risk of ICH in patients treated with warfarin.23, 24 Figure 2. Axial CT scans from 5 patients demonstrate ICH in the pons (a), cerebellum (b), thalamus (c), basal ganglia (d), and the corticosubcortical or lobar brain regions (e). Epidemiologic studies support the association between hypertension and nonlobar ICH, 8 and clinical trials demonstrate a clear decrease in risk of ICH with sustained blood pressure control.8-10 Cerebral amyloid angiopathy (CAA), defined as amyloid deposition in cerebral vessel walls, affects capillaries, arterioles, and small to medium-sized arteries of the cerebral cortex, overlying leptomeninges, and cerebellum.5, 11 12 In a process that begins with amyloid deposition in the smooth muscle media of these vessels and culminates in total obliteration of viable smooth muscle cells, CAA causes ICH when severely affected vessels rupture with extravasation of blood into the brain parenchyma. The main constituent of vascular amyloid in sporadic CAA is the b-amyloid peptide (Ab). The only established risk factor for CAA, other than age, is possession of the Apoliprotein E (APOE) e2 and e4 alleles.8, 13-15 Anticoagulation-related ICH Anticoagulation with warfarin increases the risk of ICH and worsens its severity, approximately doubling its mortality (Figure 1).16-18 Of note, among the smaller proportion of patients with warfarin-related ICH who survive, functional outcome appears to be no different from those surviving non warfarin-related ICH.18 The annual risk of ICH in patients undergoing long-term anticoagulation for atrial fibrillation is 0.2% to 0.6%, with higher rates noted in clinical trials using target international normalized ratio (INR) values > 4.0.19 The excess mortality of ICH when it occurs is likely related to prolonged bleeding after symptom onset, which is commonly observed in patients with anticoagulationrelated ICH.20 This observation highlights the importance of emergent reversal of anticoagulation for patients with warfarin-related ICH. While long-term anticoagulation clearly increases the risk of developing ICH, the mechanisms by which it leads to bleeding remain unclear. Risk of ICH rises with increasing intensity of anticoagulation.21 Nonetheless, the Acute ICH Patients with acute ICH present like patients with other types of stroke, with the sudden onset of focal neurologic dysfunction, although seizure and reduction in level consciousness tend to occur more commonly with ICH. Decreased level of consciousness is prominent with large hematomas as well as smaller lesions in the thalamus and brainstem. Headache and vomiting due to increased intracranial pressure are also common. Approximately one-fourth of patients who are initially alert experience deterioration in their levels of consciousness within the first 24 hours.25, 26 Ongoing bleeding, leading to larger accumulations of blood in the brain, is the most important cause of this deterioration.27 Although hematoma formation sets off a series of reactions in the involved tissue that contribute to neurologic injury,28-31mass effect of the ICH itself appears to be the primary mechanism of injury. The damage caused by ICH is proportional to the volume of blood that extravasates from the ruptured vessel or vessels.20, 32, 33 ICH was once thought to be a brief event lasting seconds to minutes; however, several studies suggest that as many as 30% to 40% of patients experience ongoing bleeding while in the emergency room, particularly if they are taking warfarin.20, 27, 34 Tr e a t m e n t o f A c u t e I C H Although ICH patients frequently become critically ill and require specialized care within the intensive care unit, management interventions most likely to affect outcome must be made within the first few hours of ictus in the emergency department (ED). Early intubation is essential for patients with impaired arousal when they are at risk for aspiration, hypoxemia and hypercarbia due to impairment of reflexes that protect the airway. The CT scan must be evaluated for evidence of herniation or hydrocephalus, findings that should prompt emergent neurosurgical evaluation. Osmotic agents are the treatment of choice for reducing intracerebral pressure (ICP) and reversing mass effect in patients with herniation. Because of the transient nature of its effect on ICP and the high risk of rebound elevations in ICP associated with prolonged exposure, hyperventilation should be reserved for use in those patients about to undergo emergent neurosurgical intervention. Blood pressure elevation is common in acute ICH, but whether it is a consequence of the hemorrhage or a contributor to prolonged bleeding is not understood. Current American Heart Association Guidelines recommend maintaining the mean arterial pressure <130 mm Hg, the systolic blood pressure < 180 mm Hg, and the cerebral perfusion pressure above 70 mm Hg.1, 2 Since roughly one-quarter of ICH patients in the ICU may develop seizures within the first 72 hours,35 prophylactic antiepileptic therapy may be reasonable in critically ill patients, but is unproven. Prophylactic anticoagulation for prevention of deep venous thrombosis may be started 24 to 48 hours after ICH when there is no evidence of ongoing hematoma expansion.36 Given the evidence linking hyperglycemia to increased mortality in ICH, tight glucose control may be an important supportive measure.37 Hemostatic Management The volume of blood that extravasates from the ruptured vessel is a potent determinant of outcome. The documentation among ICH patients imaged within 3 hours of symptom onset, which showed 38% had evidence of ongoing bleeding in the ED, suggests that emergently arresting this bleeding will result in smaller hematoma volumes and improvement in outcome. Recombinant activated factor VII (rFVIIa) is approved as a treatment for bleeding in patients with hemophilia who have antibodies to factor VIII or IX. The results of the recently published phase IIB, dose-ranging, proofof-concept study, the Recombinant Activated Factor VII Intracerebral Hemorrhage Trial,38 raise the exciting possibility that stopping the bleeding may well be the first effective specific intervention for acute ICH. To evaluate the effect of rFVIIa on hematoma expansion, the investigators conducted a multicenter, double-blind, placebo-controlled trial involving 399 patients with primary ICH without evidence of coagulopathy. Patients were assigned to receive 1 of 3 doses of rFVIIa (40, 80, or 160 µg/kg of body weight) or placebo. Serial CT scans were completed over the course of each patient’s hospitalization, and the volume of extravasated blood was measured on each scan to determine whether the hematoma had expanded. Primary outcome was mean percentage increase in hematoma volume measured 24 hours after administration of drug or placebo. The group receiving the highest dose of rFVIIa had a significantly smaller increase than the placebo group, but there was a trend toward benefit with smaller doses as well (Figure 3).38 Strikingly, 3-month mortality in the combined rFVIIa group was 18% compared to 29% in the placebo group, without an increase in severe disability despite the fact that severe arterial and venous thromboembolic adverse events were more than 3 times as common in the rFVIIa groups as in the placebo group (7% vs 2%). These results, while promising, require confirmation in the larger phase III trial already being planned. In particular, it will be important to determine whether lower doses of rFVIIa can achieve equally impressive effects on hematoma expansion and clinical outcome while minimizing thromboembolic complications. Reversal of anticoagulation The principles of hemostatic management probably apply even more crucially to anticoagulantassociated ICH, where emergent reversal of anticoagulant effect is likely to improve outcome. Although the ideal agents and proper dosing strategies remain to be determined, the present state of knowledge suggests that immediate correction of the coagulopathy is mandatory, along with frequent monitoring of the coagulation status in the emergency department to insure complete and sustained reversal of coagulopathy (www.stopstroke.org/ed_ich_protocol.htm). Ve n t r i c u l a r B l o o d a n d Hydrocephalus The presence of blood within the ventricles is common in patients with ICH, and associated with high mortality.39 Although the deleterious effect of intraventricular blood may be related to the development of obstructive hydrocephalus, evidence suggests blood within the ventricles can have direct toxic effects independent of hydrocephalus. Ongoing clinical trials are investigating whether the application of thrombolytics through indwelling intraventricular catheters is safe and improves outcome.40 Surgical Evacuation Surgical evacuation of cerebellar hemorrhages is life saving and deficit-sparing. While patients whose hemorrhages are < 3 cm in diameter as measured on CT scan may recover well without surgery, all patients with cerebellar ICH should receive emergent neurosurgical evaluation. The application of surgical evacuation to hemorrhages elsewhere in the brain, however, is less clear. Although evacuation offers the theoretical benefits of reducing mass effect and arresting the release of toxic byproducts of the hematoma, its benefit has not been confirmed in randomized trials.41 At present, many centers restrict surgical intervention to patients with cerebellar ICH and those with lobar ICH who develop neurologic deterioration. Primary Prevention of ICH The most crucial intervention to prevent ICH is adequate control of hypertension.10 Although no existing medications have been proven to prevent CAA-related hemorrhage, there are multiple potential targets for therapies aimed at altering the metabolism or bioactivity of Ab. One approach to reach early clinical trials is the use of a low molecular weight anionic molecule that interferes with the interaction of Conclusion ICH is the most lethal form of stroke. Prompt evacuation of cerebellar hemorrhages is both life-saving and deficitsparing. While the emergent institution of supportive measures in the ED is crucial, targeted hemostatic therapy with rFVIIa provides the first promising specific treatment for acute ICH. Primary and secondary prevention of ICH at present involve aggressive control of hypertension and the judicious selection of patients for long-term anticoagulation. Figure 3. Estimated Mean Percent Change in ICH Volume 24 Hours after administration of rFVlla or placebo for 399 patients enrolled in the Recombinant Activated Factor VII Intracerebral Hemorrhage Trial. 38 RR indicates relative reduction. Bars represent 98.3% confidence intervals. Ab with sulfated glycosaminoglycans in the basement membrane of vessel walls.42 Secondary prevention of ICH Secondary prevention strategies differ depending on whether the initial ICH was lobar or nonlobar. The recurrence rate for lobar hemorrhage is considerably higher than for nonlobar hemorrhage.43, 44 While careful control of hypertension reduces the risk of recurrent nonlobar hemorrhage,10 it probably has little effect on recurrent lobar hemorrhage.43 According to a decision analysis model, the risk of recurrent hemorrhage outweighs the benefit of anticoagulation in patients with both nonvalvular atrial fibrillation and a history of lobar hemorrhage, while patients with a history of nonlobar hemorrhage may benefit from anticoagulation if their ischemic stroke risk is high.45 The risk of using aspirin in patients with atrial fibrillation and previous lobar ICH may outweigh the benefits in patients at low risk for ischemic stroke, but the cardiovascular benefits of ASA must also be taken into account. Authors: AmytisTowfighi, MD and Jonathan Rosand, MD, MSc Vascular and Critical Care Neurology, Massachusetts General Hospital/Harvard Medical School Research Support Research funding: American Academy of Neurology Research and Education Foundation; National Stroke Association; and the National Institute of Neurological Disorders and Stroke. Dr. Rosand is a member of the Recombinant Activated Factor VII Intracerebral Hemorrhage Trial Investigators Group and has received research support and speaking fees from Novo Nordisk A/S. Send correspondence to: Sponsored by an educational grant from Novo Nordisk Jonathan Rosand, MD, MSc Neurology Clinical Trials Unit 15 Parkman Street, ACC 836 Boston, MA 02114 USA Tel: (617)724-8773 Fax: (617)726-5346 Email: jrosand@partners.org References 1.Lépine R. Note sur la paralysie glosso-labiée cérébrale à forme pseudo-bulbaire. Revue Mensuelle de Médecine et de Chirurgie. 1877;1:909-922. 2.Davison C, Kelman H. Pathological laughing and crying. 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Wayne Clark, M.D. Neurologist Oregon Health Sciences University Ashfaq Shuaib, M.D. Director of Neurology University of Alberta Jeffrey Hecht, M.D. Physiatrist Patricia Neal Rehabilitation Center Don Smith, M.D. Neurologist Colorado Neurological Institute William G. Barsan, M.D. Emergency Medicine University of Michigan Robert W. Hobson II, M.D. Vascular Surgeon UMDNJ-NJ Medical School Joseph Zambramski, M.D. Neurosurgeon Barrow Neurological Institute Jose Billér, M.D. Neurologist Indiana University Marc Mayberg, M.D. Executive Director Seattle Neuroscience Institute Editorial Board Editor, Steven R. Levine, M.D. Professor of Neurology Stroke Program Mt. Sinai School of Medicine