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ساعت ٤:٠٦ ‎ق.ظ روز ۱۳۸٩/۸/٢٩   کلمات کلیدی: subarachnoid hemorrhage ،rebleeding

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Be Alert for Rebleeding in Patients with Subarachnoid Hemorrhage
Nirav G. Shah MD
Subarachnoid hemorrhage (SAH) is a commonly misdiagnosed problem. Although SAH may produce minor symptoms (see Table 202.1), it is often fatal, and early surgical intervention can improve outcomes.
Watch Out For
The typical patient who develops a subarachnoid hemorrhage frequently has a positive personal or family history for SAH, a history of polycystic kidney disease, hypertension, alcohol abuse, or cigarette smoking. In addition, the incidence is more common in patients with heritable connective-tissue disease, especially fibromuscular dysplasia. A ruptured saccular aneurysm is the most common etiology of subarachnoid hemorrhage, followed by trauma, arteriovenous malformations, illicit drug use (especially cocaine), and vasculitides.
The most common presenting symptom of subarachnoid hemorrhage is headache of unusual severity. Patients typically describe their pain as “the worst headache of my life.” Sometimes, the life-threatening bleed may be preceded by a small bleed and headache, which is called a sentinel headache. Other symptoms may include nuchal rigidity, diminished level of consciousness, aphasia, and bilateral weakness of the lower extremities. Signs that are apparent on physical examination include papilledema, third or sixth nerve palsy, nystagmus, left-side visual neglect, or retinal hemorrhage.
The most important study to obtain when suspecting a subarachnoid hemorrhage is a noncontrasted computed tomography (CT) scan of the head. Preferably, the study should be done with thin cuts about 3 mm in thickness in order to identify small collections of blood. The CT scan is most sensitive if obtained within 24 hours of the bleed. In one study, the percentage of positive scans went from 92% to 50% from day one to day seven. Of note is that if the underlying etiology of the subarachnoid bleed is a ruptured aneurysm, the location of blood on the CT scan does not accurately predict the location of the aneurysm. If the CT scan is negative but the clinical syndrome is still consistent with SAH, a lumbar puncture should be performed to identify blood in the cerebrospinal fluid.
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TABLE 202-1 HUNT-HESS SCALE FOR GRADING SUBARACHNOID HEMORRHAGE
GRADENEUROLOGICAL STATUS
1 Asymptomatic; or minimal headache and slight nuchal rigidity
2 Moderate to severe headache; nuchal rigidity; no neurologic deficit except cranial nerve palsy
3 Drowsy; minimal neurologic deficit
4 Stuporous; moderate to severe hemiparesis; possible early decerebrate rigidity and vegetative disturbances
5 Deep coma; decerebrate rigidity; moribund appearance
What to Do
The treatment of subarachnoid hemorrhage includes active management of cerebral perfusion pressure, prophylaxis for vasospasm, anticonvulsive therapy to prevent seizures, and definitive therapy via surgery or endovascular repair. There is ongoing debate whether early surgery or endovascular repair portends a better prognosis compared with waiting 10 to 14 days for the improvement of edema prior to definitive therapy.
The three most common complications of subarachnoid hemorrhage are rebleeding, vasospasm, and hydrocephalus. Rebleeding is a significant risk in patients with an SAH and occurs with an incidence of approximately 3% to 6%. It most frequently occurs in the first 24 hours following a bleed with the highest risk in the first 6 hours. Rebleeding can present with altered mental status. Any changes in mental status after SAH warrants an emergent repeat CT scan. The factors that can most reliably predict the possibility of rebleeding are size of aneurysm and the Hunt-Hess Grade of the neurological status.
The second complication, vasospasm, is the leading cause of mortality in patients with ruptured aneurysms. The time of occurrence is usually between days three and seven but can be seen as far out as 14 days from subarachnoid hemorrhage. This should be suspected with any change in neurologic status or with any focal deficits. One method used to monitor for vasospasm is transcranial Doppler, which looks for changes in the velocity of blood flow as a precursor to actual symptomatic vasospasm. The risk of vasospasm is based on size of bleed, location, age, and neurologic status. Nimodipine, a calcium antagonist, has been used to significantly reduce the occurrence of vasospasm. Once vasospasm occurs after aneurysm clipping, treatment is optimized by use of the triple-H therapy, which includes hemodilution, induced hypertension, and hypervolemia.
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Acute or chronic hydrocephalus is also a possible complication associated with subarachnoid hemorrhage. The etiology is thought to be secondary to occlusion of cerebrospinal fluid flow from debris or decreased cerebrospinal fluid production. Risk factors for the development of hydrocephalus include age at presentation, the location of the bleed, the size of the bleed, and concomitant intraventricular hemorrhage. The clinical presentation typically includes altered mental status with radiologic confirmation by CT scan. The treatment includes drainage of cerebrospinal fluid via ventriculostomy. Typically, about 50% of the patients with acute hydrocephalus have resolution of symptoms while the remaining patients have poorer outcomes with a high rate of mortality.
Suggested Readings
Edlow JA, Caplan LR. Avoiding pitfalls in the diagnosis of subarachnoid hemorrhage. N Engl J Med. 2000;342:29–36.