Morning Report: 3/26/2013

Thanks to Dr. Jegede for today’s Morning Report!

Subarachnoid Hemorrhage

Headaches make up 2% of all ED visits. Of all those with headaches, only about 1% will have a SAH.
Among those with sudden onset headache and normal neuro exam, 10-16% will have SAH.

Cause of SAH: Trauma is the most common cause of all SAH. Most spontaneous cases are related to ruptured aneurysm. Ruptured aneurysms account for 85% of all spontaneous SAH. About 80-85% of aneurysms are in the anterior circulation and the rest are in the posterior circulation.

What causes aneurysm? Aneurysms were once thought to be congenital, but studies found that aneurysms are rare in children. The current theory now is that aneurysms develop gradually over a lifetime due to acquired arterial wall changes.

The biggest risk factor for aneurysm rupture is size. Aneurysms less than 10mm have a 0.7% risk of rupture while larger aneurysms are 5 times more likely to rupture

Who needs SAH workup?

Someone with a classic thunderclap worst headache of life.

Of all patients with worst headache of life, 10 to 16% will have a serious pathology such as SAH
70% of all pts with SAH p/w isolated severe sudden onset headache.
Physical exam (aside from the headache), may be completely normal in pts with SAH. In comatose pts, the eye exam may reveal retinal hemorrhages which are seen in 10% of pts with SAH.

Diagnostic Studies

CT w/o Contrast: CT finding of hemorrhage is time dependent. As time goes on from symptom onset, blood is degraded and diluted as the CSF is continuously circulated.

Sensitivity of CT can range from 90 to 98% in the first 24hours with decreasing sensitivity after 12hours

Lumbar Puncture

All pts with neg CTs should have an LP.

LP can detect small amounts of blood that may not be apparent on CT
Interpretation of the LP can be challenging. There is no set criteria for a positive LP in the diagnosis of SAH. When the CSF has blood, the dilemma is trying to find out if it is due to a traumatic tap or SAH. If no RBC is in tube 4, the CSF is normal. On the other hand, it is accepted that the presence of constant numbers of RBC from tube 1 to tube 4, is abnormal. The gray area becomes when there is decreasing number of RBCs from tube 1 through 4 without complete clearing. In this case there is no clear data to show average number of RBCs to make a diagnosis of SAH
Xanthochromia: produced by breakdown of hgb in the csf into pigmented byproducts. Presence of xanthochromia is suggestive of SAH. Xanthochromia may take up to 12hours to develop and can last for up to 2weeks.

CTA can be helpful in detecting ruptured aneurysm in patients with ambigious LP results or pts with difficult LP.

Management of SAH

Neurosurgery must be consulted for definitive therapy. In most cases pt will be required to be transferred to a tertiary care facility. Serial neuro exams should be done to assess for deterioration.

Airway management

Head of bed should be kept at 30deg to facilitate venous drainage

BP management: One of the main complications of SAH is rebleeding which is a significant cause of morbidity and mortality. High BP increases the risk of rebleeding, whereas lower pressures may compromise cerebral perfusion pressure leading to cerebral ischemia. Target BP should be discussed with neurosurgery. Nicardipine, Labetalol and Esmolol are commonly used agents.

Vasospasm prevention: Vasospasm is a delayed complication that may develop several days and up to 2 weeks post SAH, peaking at 7 to 10 days after the event. Pts should be started on Nimodipine 60mg po q4hrs to prevent this. Nicardipine has also been shown to reduce vasospasm.

Seizure prophylaxis: highest risk of seizure occurs in patients with a higher clinical grade of SAH. They should be placed on prophylaxis because they are likely to deteriorate after a seizure

Definitive Aneurysm Repair: Clipping vs. Coiling: studies show improved outcomes for pts who underwent endovascular coiling. Pts who undergo clipping have an increased risk of having a seizure while pts who undergo coiling have a slightly increased risk of rebleeding.

Prognosis: in Hospital mortality after a SAH is still >30% even with transfer to a neurosurgical ICU. The complication of rebleeding is the reason most pts die as up to 80% of pts who rebleed die or remain disabled.

Reference:

Emergency Practice. “Evidence Based Approach to Diagnosis and Management of Aneurysmal Subarachnoid Hemorrhage in the Emergency Department”. Vol 11 Number 7 July 2009