Subarachnoid hemorrhage: Clinical sciences

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Introduction 0:00–0:40

Subarachnoid hemorrhage refers to an intracranial bleed that occurs between the pia and arachnoid layers of the meninges, which are protective layers that cover the brain.
If not promptly recognized and treated, blood pooling in the subarachnoid space can lead to a fatal increase in intracranial pressure.
Now, based on the underlying cause, subarachnoid hemorrhage can occur as a result of traumatic head injuries, but it could also occur spontaneously, which is also known as non-traumatic subarachnoid hemorrhage.
Now, if your patient presents with a chief concern suggesting subarachnoid hemorrhage, first, perform an ABCDE assessment to determine if they are unstable or stable.

Unstable Patient 0:40–2:32

If unstable, stabilize the airway, breathing, and circulation. At this point, you might even have to intubate the patient and start mechanical ventilation.
Next, obtain IV access, consider starting IV fluids, and don’t forget to put your patient on continuous vital sign monitoring, including heart rate, blood pressure, and pulse oximetry, as well as cardiac telemetry.
Finally, you might need to manage high intracranial pressure, or ICP for short. Now, here’s a clinical pearl to keep in mind!
In severe cases, subarachnoid hemorrhage can increase ICP, which triggers a physiological response known as the Cushing triad, which consists of bradycardia, hypertension, and irregular breathing.
Moreover, important physical exam findings associated with dangerously high ICP and potential brain herniation include dilated pupils that are unresponsive to light!
If you notice any of these signs, place an ICP monitor and start appropriate medical management, which includes elevating the head of the bed, hyperventilation, sedation, and hyperosmolar therapy.
If high ICP is partly due to ventriculomegaly, your patient will require CSF diversion, such as placing an external ventricular drain.
Finally, If high ICP persists despite medical management and CSF diversion, you should proceed to emergent decompressive craniectomy.
Let’s go back and look at stable patients. In this case, first, obtain a focused history and physical exam.

Stable Patient 2:32–2:54

When taking a patient’s history, it is important to determine the characteristics of headaches and ask about any head trauma.
This will help you determine whether the etiology is traumatic or non-traumatic. First, let’s focus on traumatic subarachnoid hemorrhage.

Traumatic subarachnoid hemorrhage 2:54–4:05

In this case, your patient will usually report a nonspecific headache and recent head trauma. Next, the physical exam will reveal neck stiffness due to blood irritating the meninges, also known as nuchal rigidity.
Additionally, your patient might present with altered mental status and focal neurologic deficits. With these findings, you should suspect traumatic subarachnoid hemorrhage, so immediately order a non-contrast head CT.
If the CT reveals blood in the subarachnoid space in cortical convexities, meaning on the surface of the brain, with or without blood in other brain compartments such as the epidural, subdural, or intraparenchymal space, you should diagnose traumatic subarachnoid hemorrhage.
Once you diagnose the condition, avoid hypertension to prevent rebleeding and correct any coagulopathy. Finally, don’t forget to consult your surgery team, more specifically, neurosurgery, for possible ICP monitoring and CSF diversion.
Now, let’s go back and take a look at non-traumatic subarachnoid hemorrhage. These patients will typically endorse the worst headache of their life, which is often called a “thunderclap” headache because the pain is maximum at onset.

Non-traumatic non-aneurysmal subarachnoid hemorrhage 4:05–5:57

In some cases, a few days or a few weeks before the patient’s presentation, they could also report a sudden, persistent, intense headache called a “warning” or sentinel headache.
This type of headache occurs due to aneurysmal wall stretching or minor aneurysmal leak and is often a sign of impending aneurysmal rupture!
Next, these individuals will deny a history of recent head trauma, but they might report cardiovascular risk factors, such as hypertension and tobacco use, as well as a family history of cerebral aneurysms.
Other important risk factors include a history of autosomal dominant polycystic kidney disease, Ehlers-Danlos type IV, and fibromuscular dysplasia.
Next, the physical exam will reveal nuchal rigidity, possibly in combination with an altered mental status and focal neurologic deficits.
Some patients might also present with ptosis and mydriasis, as well as the “down and out” deviation of the pupil. This clinical presentation is specific for cranial nerve III palsy due to a posterior communicating artery aneurysm because the posterior communicating artery runs next to the cranial nerve III.
Finally, the fundoscopic exam will often reveal papilledema, which indicates increased intracranial pressure, and sometimes, you might notice a boat-shaped hemorrhage called a subhyaloid hemorrhage .
With these findings from the focused history and physical, suspect non-traumatic subarachnoid hemorrhage and promptly order a non-contrast head CT.

Non-traumatic aneurysmal subarachnoid hemorrhage 5:57–6:59

If there are no acute findings of hemorrhage, but your suspicion of subarachnoid hemorrhage is strong, perform a lumbar puncture and send a CSF sample for analysis.
This is because the CT loses significant sensitivity for picking up subarachnoid hemorrhage after 6 hours of the event. If the CSF analysis shows elevated red blood cell count and xanthochromia, which is a yellow CSF discoloration from bilirubin due to hemoglobin breakdown, you can diagnose subarachnoid hemorrhage.
Alright, let’s go back to the head CT and discuss findings associated with hemorrhage in the subarachnoid space. In this case, you can skip the lumbar puncture and diagnose subarachnoid hemorrhage immediately.
Now, once you diagnose subarachnoid hemorrhage... Order a head CT angiogram or digital subtraction angiography to rule out a ruptured aneurysm.

Non-traumatic non-aneurysmal SAH 6:59–7:44

If angiography does not identify an aneurysm, diagnose non-traumatic non-aneurysmal subarachnoid hemorrhage, which could be secondary to conditions like an arteriovenous malformation, a dural venous sinus thrombosis, or vasculitis.
As before, prevent rebleeding by avoiding hypertension, and correct any coagulopathy. Finally, consult your neurosurgery team for possible ICP monitor placement and CSF diversion.
On the other hand, if angiography reveals an aneurysm... diagnose non-traumatic aneurysmal subarachnoid hemorrhage.

Non-traumatic aneurysmal SAH 7:44–9:26

Most aneurysm ruptures occur with saccular aneurysms, also known as berry aneurysms, in the Circle of Willis. Again, the management is based on preventing rebleeding by avoiding hypertension and correcting any coagulopathy.
Next, consult your neurosurgery colleagues to consider ICP monitoring or CSF diversion. They will also determine with neurointerventional radiology how to secure the aneurysm, which can be done via endovascular coiling or stenting, or open surgery with clipping.
After the aneurysm is secured, the patient will require ICU monitoring due to the high risk of cerebral vasospasms and delayed cerebral ischemia.
Moreover, the highest risk of cerebral ischemia is in the first 2 weeks after the rupture. Finally, to minimize the risk of ischemia, be sure to maintain euvolemia and give the calcium channel blocker nimodipine.
Now, here’s a clinical pearl to keep in mind! Seizures may occur in any patient with subarachnoid hemorrhage, so be sure to treat any seizures promptly with anti-seizure medications.
Moreover, if the hemorrhage is due to trauma, start seizure prophylaxis with an anti-seizure medication. Finally, if the patient has persistent poor mental status, consider EEG monitoring to evaluate for non-convulsive seizures.
Alright, as a quick recap… Subarachnoid hemorrhage refers to an intracranial bleed that occurs between the pia and arachnoid layers of the meninges.

Review 9:26–10:39

In unstable patients with subarachnoid hemorrhage, assess for elevated ICP and provide appropriate medical and surgical treatment.
On the other hand, if your patient is stable, be sure to determine the characteristics of headaches and ask about any head trauma.
If history reveals a nonspecific headache and recent head trauma, and their head CT shows subarachnoid hemorrhage, diagnose a traumatic subarachnoid hemorrhage.
Lastly, if there’s no history of trauma, diagnose non-traumatic subarachnoid hemorrhage, which could be non-aneurysmal or aneurysmal.
Treatment for all subarachnoid hemorrhages includes blood pressure control, correcting any coagulopathy, and neurosurgery consultations for possible ICP monitoring or CSF diversion.
Finally, in aneurysmal subarachnoid hemorrhage, the ruptured aneurysm should be secured by either endovascular approach
Subarachnoid hemorrhage: Clinical Sciences: Video | Osmosis