Emergency Neurological Life Support: Subarachnoid Hemorrhage

DOI: https://doi.org/10.1007/s12028-017-0458-8

Abstract-Summary Subarachnoid hemorrhage (SAH) is a neurological emergency because it may lead to sudden neurological decline and death and, depending on the cause, has treat- ment options that can return a patient to normal.

Extended: Subarachnoid hemorrhage (SAH) is a neurological emergency.

Introduction Although trauma is the most common cause of blood in the subarachnoid space, this protocol will focus on non- traumatic SAH, of which the predominant cause is a ruptured intracranial aneurysm or arteriovenous malformation (AVM).

At least half of the remainder of atraumatic SAH cases are caused by non-aneu-

rysmal bleeding from a “perimesencephalic” SAH.

These guidelines discuss the diagnosis and management of aneurysmal SAH upon admission to the emergency department (ED) and provide an evidence-based review of SAH management.

Clinical Features The vast majority of patients with aneurysmal SAH experience abrupt onset of a severe headache, which may be associated with vomiting, neck pain, neck stiffness, or loss of consciousness.

The remaining 50% of patients present with a broad spectrum of neurological deficits ranging from minor mental status changes to focal deficits associated with the headache.

Although the classic presentation of SAH includes onset of thunderclap head- ache with exertion or a Valsalva maneuver, this presentation (headache developing

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with exertion) actually occurs in a minority of patients, some of whom develop symptoms during sleep [371].

All patients with a new, severe headache and a new abnormality in their neuro-

logical exam should be evaluated further.

Among neurologically intact patients, clinicians should strongly consider further diagnostic evaluation if the headache is abrupt in onset, more severe than any prior headache and/or unique in character, especially if the patient exhibits or describes worrisome associated symptoms.

Prehospital Care For patients presenting with isolated headache who are neurologically intact, there are no specific prehospital interventions, apart from consideration of analgesics.

For patients presenting with headache who are neurologically altered, pre-notifi-

cation of the ED staff and check of a finger stick glucose are important steps.

Prehospital providers should be prepared to use suction to facilitate visualization

during direct laryngoscopy.

Airway and Hemodynamic Management The decision to perform an endotracheal intubation is based on the ability of the patient to control his or her airway, the presence of hyperventilation, hypoxia resis- tant to supplemental oxygen, or an anticipated clinical decompensation, especially if transfer to another facility is planned (see the ENLS Airway, Ventilation, and Sedation protocol).

Cardiovascular resuscitation should be performed, if necessary, in accordance

with Advanced Cardiovascular Life Support guidelines.

Brain Imaging The first step in the diagnosis of SAH in the ED is non-contrast head CT [372–374].

The CT in patients with aneurysmal SAH will show blood, which appears hyper-

dense (i.e. brighter than brain), in the subarachnoid space.

The sensitivity of head CT for SAH decreases as time elapses. In one study using multi-detector scanners, CT sensitivity in SAH patients with

a normal mental status was still only 91% [375].

One recent study suggested that CT was 100% sensitive within three days of the

headache onset [376].

The last relevant study—a multi-center, ED-based study that has not been inde- pendently verified—found that CT is 100% sensitive if performed within 6 h of headache onset [377].

Of the 240 of 3132 (7.7%) ED patients with headache in the study, CT was 93%

sensitive overall.

CT revealed the SAH in all of these early-presenters.

CT Negative for SAH/LP Positive To measurement of the opening pressure and assessment for xanthochromia, a trau- matic tap can be distinguished from SAH by comparing the number of RBCs pres- ent in the first tube of CSF as compared to the last.

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4 Treatment

Whereas the number of RBCs will decrease from the first to the last tube in a

traumatic tap, the number of RBCs should not substantially decline in SAH.

The absolute number of RBCs in the last tube may help to distinguish a traumatic

tap from SAH.

A retrospective study of 1739 patients with acute non-traumatic headache con- ducted in 12 Canadian EDs found that the presence of fewer than 2000 × 106/L RBCs in the final tube and the absence of xanthochromia had a negative predictive value of 100% [95% confidence interval 99.2 to 100%] for excluding SAH [378].

Alternative Diagnostic Pathways Other diagnostic pathways have been suggested, including the use of magnetic reso- nance imaging (MRI), which is highly sensitive for blood, including SAH, and is superior to CT in terms of timing the bleed.

Another model includes an LP-first strategy based on mathematical modeling that indicated improved resource management and a higher rate of LP (it should be noted that this method has not been clinically tested in the CT era and is not com- monly used) [379].

Primary CT followed by CT angiography (CTA) has been suggested as a possi-

ble diagnostic pathway [380, 381].

Among other issues, however, the CT (if negative) followed by CTA will primar-

ily diagnose an aneurysm as opposed to diagnosing a bleed.

SAH Confirmed If not already done, blood should be sent to the laboratory for a complete blood count as well as coagulation tests (PT, PTT, INR, platelets), electrolytes, renal func- tion tests, troponin, and a type and screen.

Both therapies isolate the aneurysm from the cerebrovascular circulation and

should be carried out as soon as feasible [372].

Several studies have shown that patients have improved outcomes when they are treated at high volume centers, defined as those that treat >35 cases per year [372, 382, 383].

Low volume centers should strongly consider transfer of the patient to a high-

volume center as soon as feasible.

Initial Orders Once the diagnosis of SAH is made and the patient is stabilized, the clinician should speak to a cerebrovascular specialist.

To the standard communication about a patient’s history and presentation, the conversation should address airway status, the clinical status of the patient (often measured using the Hunt and Hess or the World Federation of Neurological Surgeons scores), results of brain imaging and/or CSF analysis, and presence or absence of hydrocephalus.

The discussion should also include goals of BP control, review of administered medications for pain and anxiety, laboratory results (especially coagulation tests), seizure prophylaxis, as well as which clinician will take responsibility for vascular imaging.

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Seizure Prophylaxis Acute seizures should be treated with anticonvulsants, but prophylactic anticonvul- sants are optional.

Both the AHA and NCS guidelines suggest consideration of anticonvulsants in the immediate post-hemorrhage period [372, 384], while other experts recommend against this practice [385].

A very short course of prophylactic anticonvulsants may be recommended in the

period following diagnosis and before definitive aneurysm treatment.

Decline in Neurological Status New hypoxia may result from neurogenic pulmonary oedema.

Cardiovascular collapse could be the result of increasing hydrocephalus, brain herniation (Cushing’s response), neurocardiogenic shock from Takotsubo cardio- myopathy, or respiratory failure from neurogenic pulmonary oedema.

Physical examination may show further evidence of herniation or a new seizure

requiring treatment.

A repeat CT scan is also necessary, as it may show herniation, ultra-early rebleed- ing, development of or increase in hydrocephalus, or, rarely, development of an intraparenchymal or subdural hematoma.

Coagulopathy For patients with SAH taking antiplatelet agents, such as aspirin, clopidogrel or prasugrel, management recommendations were recently published by mem- bers of the Neurocritical Care Society and Society of Critical Care Medicine in their 2016 Guideline for Reversal of Antithrombotics in Intracranial Hemorrhage [386].

In the 2016 Guideline, platelet transfusion is recommended for patients receiving aspirin- or ADP inhibitor- associated SAH who will undergo a neurosurgical procedure.

Platelet transfusion is not recommended if no neurosurgical procedure is planned. The risk–benefit ratio of anti-platelet therapy reversal using other hemostatic agents such as desmopressin (DDAVP) should be considered for the individual patient in consultation with local experts in coagulopathy management.

Treat Pain and Anxiety Treatment of pain, vomiting, and anxiety is clinically important.

Judicious amounts of short-acting IV analgesics, such as fentanyl, should be

used to help the patient avoid straining, valsalva, and stress. Treating vomiting with anti-emetics may also be helpful. These steps may also help to control BP elevation related to pain and/or anxiety.

BP Management Modest hypertension (mean arterial pressure, or MAP, <110) may not require treatment.

Pre-morbid BPs should be considered and used to inform the risks and benefits

of treatment.

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Experts in the field use antihypertensive medications that are short acting, easily titratable, and can be administered as a continuous infusion to reduce the systolic pressure to below 160 mmHg, or the MAP < 110 mmHg, keeping in mind the prin- ciples mentioned above.

Hydrocephalus The clinician should carefully evaluate the CT scan for hydrocephalus, which occurs in up to 30% of SAH patients in the first 3 days.

If the hydrocephalus is symptomatic, it can be treated with an external ventricu- lar drain (EVD), although some data suggest that EVD placement may be associ- ated with rebleeding [372].

Comatose patients with hydrocephalus may have elevated ICP, so placement of a drain (EVD or lumbar drain) will not only reduce ICP via CSF diversion, but it will also provide a means to monitor ICP throughout the hospitalization.

Antifibrinolytic Agents Prevention of rebleeding prior to definitive aneurysm treatment is an important strategy.

Early definitive treatment of the aneurysm is generally recommended [372]. There has been an increased interest in early, short-term antifibrinolytic treat- ment with either epsilon aminocaproic acid or tranexamic acid in situations where surgical options are not readily available.

One study of immediate administration of tranexamic acid (TXA) in SAH patients, most of whom were treated with TXA within 24 h, demonstrated an 80% reduction in rebleeding before the definitive treatment [384, 387].

Oral Nimodipine The use of oral (or per nasogastric tube) nimodipine has been shown in multiple randomized trials to improve outcomes of SAH patients presumably by limiting delayed cerebral ischemia [388].

Because nimodipine is administered enterally, and many acute SAH patients cannot swallow, and vasospasm is typically not an urgent concern (except in rare cases of ultra-early vasospasm or patients who present in a delayed manner several days after ictus), the administration of oral nimodipine is not listed as a priority in the first hour.

Pediatric Considerations Ruptured aneurysms are rare in children and more commonly occur in adolescence than early childhood.

Infectious aneurysms, mostly caused by endocarditis related to congenital or rheumatic cardiac anomalies, also are more common in children and tend to occur in peripheral vessels.

AVMs as a cause for SAH are proportionally more common in children than in adults; there may also be an underlying conditions such as hereditary hemorrhagic telangiectasia.

Because SAH is uncommon in children, the diagnosis often is not suspected at

first presentation, which has implications for early diagnosis and management.

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SAH is much less common in children than meningitis, for which LPs are per-

formed often without imaging.

Because SAH is much less common in children, treatment should occur at a high

volume center with experienced specialists.

Vasospasm does occur but is less common than in adults.

Acknowledgement A machine generated summary based on the work of Edlow, Brian L.; Samuels, Owen 2017 in Neurocritical Care.

Emergency Neurologic Life Support: Meningitis and Encephalitis