Subarachnoid hemorrhage (SAH) is a frightening disorder in which blood ruptures from an artery in the brain and leaks into the cerebrospinal fluid (CSF). The result is that someone who is relatively young, often in their fifties or so, suddenly develops the worst headache they’ve ever had and may go on to lose consciousness and have a 50% chance of dying.
Only about a third of patients with SAH have a “good result” after treatment. As if this wasn’t enough, subarachnoid hemorrhage can set off a cascade of other problems. To safeguard against these further complications, victims of subarachnoid hemorrhage are monitored in an intensive care unit after they first come into the hospital.
There are four major complications to subarachnoid hemorrhage. Those complications are vasospasm, hydrocephalus, seizures, and rebleeding.
The word vasospasm means that blood vessels in the brain “spasm” and clamp down, reducing and sometimes even stopping blood flow to parts of the brain. The result is a stroke.
Vasospasm occurs in about 20-30% of patients who have SAH. It usually occurs three to ten days after the initial bleed. Strangely, not all kinds of subarachnoid hemorrhage carry the same risk of vasospasm. SAH due to trauma, for example, is more likely to cause vasospasm than a bleed due to a berry aneurysm.
Because vasospasm is difficult to treat if it occurs, the emphasis of hospital care is prevention. The blood pressure medication nimodipine has been shown to reduce the likelihood of a poor outcome after vasospasm (though it does not seem to reduce the risk of developing vasospasm in the first place). Too little blood in the body has also been shown to correlate with vasospasm risk, and so the patient is given adequate fluids by IV. Other more experimental techniques for preventing vasospasm include giving statin medications.
People who have SAH are watched closely for signs of vasospasm with repeated neurological exams. If there’s a sudden worsening test result, it could mean vasospasm is occurring. Use of techniques like transcranial Doppler can also hint that someone is developing vasospasm.
The first step of treating vasospasm is so-called “triple-H” or hyperdynamic therapy. Triple-H stands for hypertension, hemodilution, and hypervolemia. This means that the blood pressure is kept a bit high (hypertension), a bit thin (hemodilution), and that we try to make sure there's a lot of it (hypervolemia). While the evidence for this approach is not strong, the theory is that triple-H therapy increases blood flow in the brain, thereby reducing the chances of ischemic damage caused by loss of blood flow.
If vasospasm persists in spite of triple-H therapy, more invasive options, like angioplasty (opening the blood vessel with a catheter threaded through the blood vessels) or using a catheter to inject medications like nimodipine directly at the narrowed spot, may be attempted.
Sometimes a blood clot from the subarachnoid hemorrhage can become lodged in one of the important natural drainage sites of cerebrospinal fluid (CSF). Normally, CSF is produced in the ventricles of the brain. It then travels out through small openings known as foramina. If these openings are clogged, the CSF is still produced, but has nowhere to go. The result is an increase in pressure inside the ventricles of the brain, which is known as hydrocephalus. The pressure spreads to the brain and skull.
Increased intracranial pressure can lead to decreased consciousness and coma. If left untreated, the brain can be pushed through tight regions like the opening at the base of the skull, resulting in death. To prevent this pressure build-up, neurosurgeons may place a shunt into the skull to monitor pressure and drain out excess CSF. If pressure continues to build or is very severe, a craniostomy may be performed to remove part of the skull and allow room for the brain to swell.
Blood can irritate the cerebral cortex and result in a seizure. However, only about 5% of patients with SAH go on to have epilepsy. Although seizures can worsen the outcome of a patient in the ICU, the risks of side effects from common anti-epileptics may outweigh the benefits unless the patient is noted to have a seizure. In this case, the patient may be continued on a medication for six to twelve months after the hemorrhage.
After a SAH due to a berry aneurysm, the risk of rebleeding is about 3-4% within the first 24 hours, then 1-2% per day in the first month. About 70% of people whose aneurysms rupture again die as a result. Frequent neurological examinations and periodic head CT scans, especially in the period shortly after the initial bleed, can help detect rebleed if it occurs.
To prevent rebleeding, high-risk aneurysms in the brain are sealed off. This can be done by using a type of surgical staple to clip the aneurysm off from the rest of the artery, or by threading a catheter through the arteries up to the aneurysm and inserting metal coils or a sealant substance to seal the aneurysm. Which procedure is better is a complex decision that varies from person to person and will need to be discussed with the medical team.
While the four main complications of subarachnoid hemorrhage may seem like more than enough, unfortunately there are several more potential dangers that come from having a serious enough illness to require care in an intensive care unit. Deep vein thrombosis of the legs, hyponatremia, and hospital-acquired infections must also be guarded against. Surviving the initial bleed is only part of the challenge of subarachnoid hemorrhage. Surviving the rest will require close cooperation with a team of medical specialists.
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