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Diagnosis
The diagnosis of SAH is critical. About half of affected patients seek medical attention before a major SAH, but some studies have shown that up to 60% of them are misdiagnosed, usually because the significance of a severe headache was overlooked.1 A recent retrospective study of 217 SAH patients seen at four tertiary-care neurosurgical centers found that 25% were misdiagnosed on initial diagnosis. The specialists involved in the initial diagnoses typically worked in internal medicine (43%), an emergency department or walk-in clinic (41%), or neurology (19%). This study demonstrated that misdiagnosed SAH patients were more likely to deteriorate clinically and have a poor outcome than patients diagnosed correctly at the initial medical evaluation. Medical centers with appropriate specialists and facilities enhance the likelihood of a proper diagnosis, which may make use of the following techniques:
CT scan. It is recommended that a noncontrast CT scan of the head should be conducted on all patients with suspected SAH within 24 hours of the initial hemorrhage, because the ability to detect the clot declines over time.2 In 92% of cases, a high-density clot is evident within the subarachnoid space, which confirms the presence of SAH.3 The CT scan provides an estimate of the origin and extent of the hemorrhage, and it may indicate bleeding into the intraventricular and intracerebral spaces.4
Diagnostic lumbar puncture. CT evidence of blood can disappear rapidly in the first few days after hemorrhage. Therefore, if the initial CT scan is negative, it is recommended that a lumbar puncture for analysis of cerebrospinal fluid (CSF) should be conducted on all patients with suspected SAH. It is important to distinguish SAH from bleeding caused by the lumbar puncture itself. SAH is suggested by the presence of a constant level of thousands of red blood cells per mm3 of CSF, especially when the CSF supernatant remains xanthochromatic after centrifugation.4 Xanthochromia should be confirmed with spectrophotometry, not the naked eye.2
Cerebral angiography. Selective catheter cerebral angiography is the method of choice for diagnosing a cerebral aneurysm as the cause of SAH.3,4 However, angiography will not identify the source of bleeding in approximately 20%-25% of cases. The AHA Stroke Council guidelines recommend magnetic resonance angiography or contrast CT if conventional angiography cannot be performed.
MRI. Although MRI is slightly more sensitive than CT in the first few days, its longer imaging time increases the risk of movement artifacts.2 The current AHA guidelines do not recommend MRI in the diagnosis of SAH due to concerns over the lack of blinded studies comparing MRI with CT and concerns about the relative insensitivity for detecting subarachnoid blood in the acute stage after SAH.3
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Sources:
- Mayer PL, Awad IA, Todor R, et al. Misdiagnosis of symptomatic cerebral aneurysm. Prevalence and correlation with outcome at four institutions. Stroke;27:1558-1563.
- Vermeulen M. Subarachnoid haemorrhage: diagnosis and treatment. J Neurol 1996;243:496-501.
- Mayberg MR, Batjer HH, Dacey R et al. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a statement for healthcare professionals from a special writing group of the Stroke Council, American Heart Association. Stroke 1994;25:2315-2328.
- Findlay JM. Current management of aneurysmal subarachnoid hemorrhage guidelines from the Canadian Neurosurgial Society. Can J Neurol Sci 1997; 24:161-170.
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DO NOT ADMINISTER NIMOTOP INTRAVENOUSLY OR BY OTHER PARENTERAL ROUTES. DEATHS AND SERIOUS, LIFE-THREATENING ADVERSE EVENTS HAVE OCCURRED WHEN THE CONTENTS OF NIMOTOP CAPSULES HAVE BEEN INJECTED PARENTERALLY
(See
WARNINGS and DOSAGE AND ADMINISTRATION.) |
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- In patients with SAH, Nimotop® controls damage with a low side effect profile.
- Decreased blood pressure is the most common side effect, occurring in 4.4% of patients. Blood pressure should be monitored during therapy.1
- Other side effects occurring at a low frequency of ≥1.0% include headache, nausea, and bradycardia.1
- No clinically significant effects on hematologic factors, renal or hepatic function, or carbohydrate metabolism have been causally associated with oral nimodipine.1
- Nimotop® does not appear to affect anesthetic management.2
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Sources:
- Nimotop® (nimodipine) Capsules Prescribing
Information December 2005
- Stullken EH, Johnston WE, Prough DS. Implications of nimodipine prophylaxis of cerebral vasospasm on anesthetic management during intracranial aneurysm clipping. J. Neurosurg. 1985; 62:200-205.
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© Bayer HealthCare Pharmaceuticals.
Bayer HealthCare Pharmaceuticals
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Wayne, NJ 07470
The information provided on Bayer products is only intended for the United States audience. Regulatory requirements, regulations, laws, and distribution of information about drug products may vary from country to country. Product names and indications (product uses) also may be different in different countries. The prescribing information provided here is based on United States labeling and may not be appropriate outside of the US.
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