Subarachnoid Hemorrhage (SAH)

Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges Meninges The brain and the spinal cord are enveloped by 3 overlapping layers of connective tissue called the meninges. The layers are, from the most external layer to the most internal layer, the dura mater, arachnoid mater, and pia mater. Between these layers are 3 potential spaces called the epidural, subdural, and subarachnoid spaces. Meninges surrounding the brain. Most SAHs originate from a saccular aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms in the circle of Willis but may also occur as a result of trauma, uncontrolled hypertension Uncontrolled hypertension Although hypertension is defined as a blood pressure of > 130/80 mm Hg, individuals can present with comorbidities of severe asymptomatic or "uncontrolled" hypertension (≥ 180 mm Hg systolic and/or ≥ 120 mm Hg diastolic) that carries with it a significant risk of morbidity and mortality. Uncontrolled Hypertension, vasculitis, anticoagulant use, or stimulant use. The most classic symptom is a sudden-onset (thunderclap) headache along with neck stiffness, vomiting, a decreased level of consciousness, and seizure. As with any stroke, focal neurologic deficits are commonly present, and rapid neurologic deterioration may ensue without prompt diagnosis and intervention. An SAH should be suspected in any person presenting with thunderclap headache and neurologic symptoms, and the diagnosis can be confirmed with neuroimaging or lumbar puncture (LP). Treatment consists of reversal of anticoagulation, control of blood pressure, and neurosurgical intervention to contain the bleed and/or relieve elevated intracranial pressure ( ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)). Even with prompt neurosurgical intervention, SAH carries a high mortality rate.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Definition and Epidemiology

Definition

  • SAH is a type of cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke (stroke) resulting from intracranial hemorrhage into the subarachnoid space. 
  • Subarachnoid space: area between the arachnoid mater and the pia mater layers of the meninges Meninges The brain and the spinal cord are enveloped by 3 overlapping layers of connective tissue called the meninges. The layers are, from the most external layer to the most internal layer, the dura mater, arachnoid mater, and pia mater. Between these layers are 3 potential spaces called the epidural, subdural, and subarachnoid spaces. Meninges surrounding the brain
Subarachnoid hemorrhage

Meninges and meningeal spaces:
The image depicts the 3 layers (dura mater, arachnoid mater, pia mater) surrounding the brain and spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord. The meninges Meninges The brain and the spinal cord are enveloped by 3 overlapping layers of connective tissue called the meninges. The layers are, from the most external layer to the most internal layer, the dura mater, arachnoid mater, and pia mater. Between these layers are 3 potential spaces called the epidural, subdural, and subarachnoid spaces. Meninges serve as mechanical protection of the CNS. They also support the cerebral and spinal blood vessels and allow for passage of the CSF. The subarachnoid space is filled with CSF.

Image by Lecturio.

Epidemiology

  • Hemorrhagic strokes:
    • Account for 15%–20% of cerebrovascular accidents 
    • 50% of hemorrhagic strokes are due to SAH.
  • Saccular aneurysms:
    • Ruptured saccular aneurysms are the most common cause of SAH.
    • Approximately 3%–5% of the population has radiographic evidence of unruptured saccular aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms.
  • 15%–20% percent of SAH cases are non-aneurysmal.
  • Incidence:
    • Global incidence of SAH: 6–10 cases/100,000 person-years
    • Blacks > whites
    • Women > men (slightly)
  • Manifests most commonly at 40–60 years of age

Etiology

Risk factors

  • Genetics Genetics Genetics is the study of genes and their functions and behaviors. Basic Terms of Genetics, increased incidence seen in:
    • Autosomal dominant polycystic kidney disease Autosomal dominant polycystic kidney disease Polycystic kidney disease (PKD) is an inherited genetic disorder leading to the development of numerous fluid-filled cysts in the kidneys. The 2 main types of PKD are autosomal dominant polycystic kidney disease (ADPKD), which is often diagnosed in adulthood, and autosomal recessive polycystic kidney disease (ARPKD), which is often diagnosed antenatally or shortly after birth. Autosomal Dominant Polycystic Kidney Disease ( ADPKD ADPKD Polycystic kidney disease (PKD) is an inherited genetic disorder leading to the development of numerous fluid-filled cysts in the kidneys. The 2 main types of PKD are autosomal dominant polycystic kidney disease (ADPKD), which is often diagnosed in adulthood, and autosomal recessive polycystic kidney disease (ARPKD), which is often diagnosed antenatally or shortly after birth. Autosomal Dominant Polycystic Kidney Disease)
    • Ehlers-Danlos syndrome Ehlers-Danlos syndrome Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders that are characterized by hyperextensible skin, hypermobile joints, and fragility of the skin and connective tissue. Ehlers-Danlos Syndrome (EDS)
    • Primary aldosteronism (glucocorticoid-remediable aldosteronism (GRA))
  • Family history:
    • Up to fivefold increased risk in 1-degree relatives
    • Familial cerebral aneurysms rupture more frequently than nonfamilial aneurysms
  • Hypertension
  • Stimulant use:
    • Cocaine
    • Amphetamine/methamphetamine
    • Sympathomimetics:
      • Cold remedies
      • Appetite suppressants
  • Coagulopathy:
    • Genetic or acquired bleeding diathesis
    • Therapeutic or supratherapeutic anticoagulation
  • Cigarette smoking
    • Dose dependent
    • Risk decreases after cessation.
  • Alcohol abuse
  • Estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries deficiency (increased incidence observed in women > 50 years of age)
  • Increased incidence observed in multiparous females

Causes

  • Trauma
  • Ruptured aneurysms
    • Saccular aneurysms (“berry aneurysms,” round shape) are the most common cause of SAH.
    • Fusiform aneurysms (dilatation of the entire vessel wall for a short distance) and mycotic aneurysms (bacterial, fungal, or viral infection of the vessel wall) are also possible.
  • Arteriovenous malformations (AVMs)
  • Arterial dissections
  • Vasculitis
  • Vascular amyloid deposition
  • Illicit stimulant use

Pathophysiology

Given that saccular aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms is the most common etiology of SAH, this section will focus on the pathogenesis of saccular aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms rupture. Events downstream of the rupture itself are common to other etiologies of SAH. 

Saccular aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms

  • Acquired lesions rather than congenital
  • Most commonly located in the circle of Willis
    • Located in the anterior circulation > posterior circulation
    • Sites of bifurcation are the most vulnerable.
  • Develop over a short time in response to abnormal vascular shear forces:
    • Time period thought to be short (hours to days)
    • May rupture or harden after initial dilation
  • Not all saccular aneurysms rupture:
    • Stabilization may occur if for capacity collagen deposition > limits of elasticity
    • Stable saccular aneurysms are relatively common.

Pathologic features of ruptured saccular aneurysms

  • Abnormalities in smooth muscle organization
  • Hypocellularity
  • Intimal hyperplasia
  • Infiltration with T cells T cells T cells, also called T lymphocytes, are important components of the adaptive immune system. Production starts from the hematopoietic stem cells in the bone marrow, from which T-cell progenitor cells arise. These cells migrate to the thymus for further maturation. T Cells and macrophages
  • Thin layer of thrombosis
  • Presence of odontogenic bacterial DNA DNA The molecule DNA is the repository of heritable genetic information. In humans, DNA is contained in 23 chromosome pairs within the nucleus. The molecule provides the basic template for replication of genetic information, RNA transcription, and protein biosynthesis to promote cellular function and survival. DNA Types and Structure (possible role of dental/periodontal infection)

Risk factors for rupture

  • Aneurysm size (diameter) > 7 mm:
    • Larger aneurysms are more likely to grow than smaller aneurysms.
    • The rate of rupture risk is proportional to the diameter of the aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms.
  • Aneurysm growth: 
    • Aneurysmal growth increases the diameter of the lesion.
    • Rapid growth outpaces the ability for collagen-mediated stabilization.
  • Aneurysm site:
    • The risk of rupture varies based on the parent vessel giving rise to the aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms.
    • Posterior circulation > anterior circulation > cavernous carotid artery

Factors that may trigger rupture

  • Trauma
  • Physical exertion within 2 hours of rupture
  • Valsalva maneuver (prolonged or repetitive)
  • Uncontrolled hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension

Clinical sequelae of rupture

  • Leakage of blood into the CSF:
    • Leads to increased intracranial pressure Increased Intracranial Pressure Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) ( ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP))
    • Initial bleeding (sentinel bleed) may last only seconds but with a high incidence of rebleeding.
  • Hydrocephalus/increased ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP):
    • Blockage of CSF flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure and/or reabsorption caused by buildup of blood products and or/adhesions 
    • Continued leakage of blood into the subarachnoid space compounds the problem.
    • Endothelial dysfunction from the site of rupture causes local hyperemia and inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation.
  • Cerebral vasospasm:
    • Release of inflammatory mediators from injured vessels may cause local vasoconstriction.
    • Vasospasm causes local hypoperfusion, worsening the ischemic insult.

Clinical Presentation

History

The classic presenting symptom of SAH is a thunderclap headache. There are other presenting symptoms as well.

  • Thunderclap headache
    • Sudden onset (seconds to minutes)
    • “Worst headache of my life”
    • Often (10%–40%) preceded by less severe prodromal headaches (“sentinel headaches”)
    • Headache location/description is inconsistent among SAH sufferers.
  • Neck stiffness/ pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
    • Correlates with spread of blood into the CSF causing meningeal irritation
    • Often presents hours after the onset of headache
  • Altered level of consciousness
    • Brief loss of consciousness 
    • Altered mental status/confusion/agitation 
    • Coma Coma Coma is defined as a deep state of unarousable unresponsiveness, characterized by a score of 3 points on the GCS. A comatose state can be caused by a multitude of conditions, making the precise epidemiology and prognosis of coma difficult to determine. Coma is uncommon.
    • Sudden death occurs in > 20% of affected individuals before presenting to medical attention. 
  • Seizure
    • In approximately 10% of SAH cases
    • Generally occur in the first 24 hours
    • Associated with poor outcome 
  • Nausea/vomiting

Physical examination

  • Elevated blood pressure
    • Often in the severe range
    • May be a precipitating event for aneurysmal rupture
    • May be a reactive phenomenon to intracerebral events
  • Meningismus
    • Correlates with spread of blood into the CSF causing meningeal irritation
    • Kernig and Brudzinski signs may be present
  • Preretinal hemorrhage
    • Associated with increased ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) as opposed to true retinal involvement
    • Associated with poor outcome
  • Oculomotor nerve (CN III) palsy
    • Often presents as a unilateral pupillary defect
    • Due to CN III compression from aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms of the posterior communicating artery or superior cerebellar artery (located near CN III exit site from the brainstem)
  • Focal neurologic deficit
    • SAH can manifest with a wide variety of neurologic findings.
    • Findings depend on the size and location of the hemorrhage.

Diagnosis

Any thunderclap headache presenting with or without neurologic symptoms/signs or altered mental status should be emergently evaluated with neuroimaging. Noncontrast CT is readily available at most acute care hospitals and is the initial test of choice. 

Ottawa SAH rule

  • Clinical decision tool used to evaluate suspected SAH with emergent noncontrast CT of the head
  • Evaluated in neurologically intact patients presenting with thunderclap headache
  • Sensitivity: 100%, specificity: 15% 
  • The presence of any of the following features is an indication for emergent CT:
    • Neck pain Neck Pain Neck pain is one of the most common complaints in the general population. Depending on symptom duration, it can be acute, subacute, or chronic. There are many causes of neck pain, including degenerative disease, trauma, rheumatologic disease, and infections. Neck Pain or stiffness
    • Limited neck flexion on examination
    • Witnessed loss of consciousness
    • Onset during exertion
    • Thunderclap headache (instantly peaking pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain)
    • Age ≥ 40 years

Noncontrast head CT

  • Cornerstone of SAH diagnosis
  • Sensitivity of up to 100%:
    • If performed within 6 hours of presentation
    • If reviewed by qualified neuroradiologist
  • Should include cuts through the base of the brain
  • Locations of blood in SAH:
    • Basal cistern(s): most common
    • Sylvian fissure(s)
    • Interhemispheric fissure
    • Interpeduncular fossa
Subarachnoid hemorrhage on ct

Subarachnoid hemorrhage (SAH):
CT scan showing intracranial bleeding

Image: “CT of subarachnoid hemorrhage” by Shazia Mirza and Sankalp Gokhale. License: CC BY 4.0

Lumbar puncture (LP)

An LP should be performed promptly (despite negative CT if clinical suspicion of SAH is high). Studies should include:

  • Opening pressure
  • Cell counts:
    • RBCs
    • WBCs
    • Visual inspection for xanthochromia (yellowish appearance due to presence of bilirubin)
  • Classic LP findings:
    • Elevated opening pressure
    • Elevated RBC count 
  • False-positive LP findings:
    • A ”traumatic tap” may reveal a falsely elevated RBC count.
    • Differential of RBC counts between successive sample tubes can help differentiate false positives from true positives.
    • The RBC count should decrease or clear with successive tubes.

Identification of the bleeding source

  • After SAH is established, angiographic studies should be performed to identify the hemorrhagic source:
    • Digital subtraction angiography (DSA): preferred method, allows for intervention to be performed simultaneously with identification of the source
    • CTA and MRA: noninvasive alternatives
  • Once the bleeding source is identified, clinical decisions about appropriateness of intervention are undertaken.

Diagnostic criteria

Several scales are utilized clinically in the diagnosis and grading Grading Cancer is the 2nd leading cause of death in the US after cardiovascular disease. Many malignancies are treatable or curable, but some may recur. Thus, all malignancies must be assigned a grade and stage in order to guide management and determine prognosis. Grading, Staging, and Metastasis of severity in SAH. The Hunt and Hess grading Grading Cancer is the 2nd leading cause of death in the US after cardiovascular disease. Many malignancies are treatable or curable, but some may recur. Thus, all malignancies must be assigned a grade and stage in order to guide management and determine prognosis. Grading, Staging, and Metastasis system is among the most commonly used in clinical medicine.

Table: Hunt and Hess score with associated mortality rate
Grade Neurologic findings Mortality rate (5)
1 Asymptomatic or mild headache and slight nuchal rigidity 1
2 Severe headache, stiff neck, no neurologic deficit except cranial nerve (CN) palsy 5
3 Drowsy or confused, mild focal neurologic deficit 19
4 Stuporous, moderate or severe hemiparesis 42
5 Coma Coma Coma is defined as a deep state of unarousable unresponsiveness, characterized by a score of 3 points on the GCS. A comatose state can be caused by a multitude of conditions, making the precise epidemiology and prognosis of coma difficult to determine. Coma, decerebrate posturing 77

Management

Stabilize life-threatening conditions

  • Secure airway by intubation for:
    • Comatose state
    • Hemodynamically instability
    • Heavy sedation 
    • Paralysis
    • Hypoxemia
    • Hypoventilation
    • Elevated ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)
  • Address any trauma-related conditions:
    • Address blood loss anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview
    • Address internal organ damage
  • Normalizing cardiovascular abnormalities:
    • Check cardiac troponins on admission
    • Address arrhythmia
    • Stabilize blood pressure
  • Treat seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures 
  • Discontinue anticoagulants Anticoagulants Anticoagulants are drugs that retard or interrupt the coagulation cascade. The primary classes of available anticoagulants include heparins, vitamin K-dependent antagonists (e.g., warfarin), direct thrombin inhibitors, and factor Xa inhibitors. Anticoagulants:
    • Reversal of anticoagulation:
      • Vitamin K if on Warfarin
      • Specific reversal agents available for Factor X inhibitors
      • FFP if specific agents are unavailable or delayed
  • Consider transfer to an appropriate facility:
    • Neurologic ICU
    • Availability of specialists:
      • Neurosurgeons
      • Endovascular specialists

Neurosurgical and endovascular intervention

Consult neurosurgery Neurosurgery Neurosurgery is a specialized field focused on the surgical management of pathologies of the brain, spine, spinal cord, and peripheral nerves. General neurosurgery includes cases of trauma and emergencies. There are a number of specialized neurosurgical practices, including oncologic neurosurgery, spinal neurosurgery, and pediatric neurosurgery. Neurosurgery and/or endovascular interventionist! The goal is to stop belling, prevent rebleeding, manage ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) to prevent secondary ischemia. Possible interventions include:

  • Surgical aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms clipping
  • Endovascular coiling
  • Ventriculostomy placement
  • Decompressive hemicraniectomy: 
    • May be indicated to relieve ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) in case of intracerebral hemorrhage Intracerebral Hemorrhage Intracerebral hemorrhage (ICH) refers to a spontaneous or traumatic bleed into the brain parenchyma and is the 2nd-most common cause of cerebrovascular accidents (CVAs), commonly known as stroke, after ischemic CVAs. Intracerebral Hemorrhage
    • May be indicated to relieve ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) in case of severe cerebral edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema

Monitoring

Monitoring should be performed in an ICU by specially trained staff equipped to continuously and simultaneously address the following:

  • Prevention of vasospasm:
    • Goal is prevention of delayed cerebral ischemia
    • Drug of choice is Nimodipine
    • Treatment is continued for 21 days
  • Blood pressure control
    • Goal systolic blood pressure <160 mm Hg 
    • Goal mean arterial pressure Mean Arterial Pressure Mean arterial pressure (MAP) is the average systemic arterial pressure and is directly related to cardiac output (CO) and systemic vascular resistance (SVR). The SVR and MAP are affected by the vascular anatomy as well as a number of local and neurohumoral factors. Vascular Resistance, Flow, and Mean Arterial Pressure <110 mm Hg
    • Avoid rapid drops in blood pressure
    • Avoid hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension
    • Drug of choice is Labetalol
  • Continuous monitoring for:
    • Hemodynamic instability:
      • May require central lines, arterial lines, ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) monitor
      • IV fluid infusions for maintenance of euvolemia
    • Neurologic deterioration
      • Focused neurologic exam every 2 hours by qualified ICU nurse
      • Emergent CT for any acute deterioration
    • Hypoxemia
    • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
    • Cardiac arrhythmia
    • ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)
    • Electrolyte imbalance:
      • Hyponatremia Hyponatremia Hyponatremia is defined as a decreased serum sodium (sNa+) concentration less than 135 mmol/L. Serum sodium is the greatest contributor to plasma osmolality, which is very tightly controlled via antidiuretic hormone (ADH) release from the hypothalamus and by the thirst mechanism. Hyponatremia is especially common in this setting
      • IV fluid choice and drip rate may be adjusted to maintain eunatremia 
  • Ventriculostomy:
    • Intracranial line placed by neurosurgical staff
    • Used to monitor ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)
    • Allows for drainage of CSF to maintain to avoid ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)
  • DVT DVT Deep vein thrombosis (DVT) usually occurs in the deep veins of the lower extremities. The affected veins include the femoral, popliteal, iliofemoral, and pelvic veins. Proximal DVT is more likely to cause a pulmonary embolism (PE) and is generally considered more serious. Deep Vein Thrombosis/PE prophylaxis:
    • Mechanical means are employed as anticoagulants Anticoagulants Anticoagulants are drugs that retard or interrupt the coagulation cascade. The primary classes of available anticoagulants include heparins, vitamin K-dependent antagonists (e.g., warfarin), direct thrombin inhibitors, and factor Xa inhibitors. Anticoagulants are generally avoided until definitive repair has been undertaken
  • Seizure prophylaxis:
    • Levetiracetam is drug of choice
    • Phenytoin has been associated with poor outcomes
    • May be continued for months after initial insult

Complications

  • Rebleeding
  • Delayed cerebral ischemia secondary to cerebrovascular vasospasm
  • Neurologic deterioration
  • Hemodynamic instability
  • Elevated ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)
  • Hydrocephalus
  • Hyponatremia Hyponatremia Hyponatremia is defined as a decreased serum sodium (sNa+) concentration less than 135 mmol/L. Serum sodium is the greatest contributor to plasma osmolality, which is very tightly controlled via antidiuretic hormone (ADH) release from the hypothalamus and by the thirst mechanism. Hyponatremia (mediated by hypothalamic injury)
  • Seizures
  • Anemia
  • Cardiopulmonary events
  • Arrhythmia
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever (noninfectious)
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever (infectious)/infection/ sepsis Sepsis Organ dysfunction resulting from a dysregulated systemic host response to infection separates sepsis from uncomplicated infection. The etiology is mainly bacterial and pneumonia is the most common known source. Patients commonly present with fever, tachycardia, tachypnea, hypotension, and/or altered mentation. Sepsis and Septic Shock

Prognosis

  • Early mortality rates as high as 10%–20%
  • 1-year mortality as high as 20%–25%
  • Survivors may have significant morbidity:
    • Increased incidence of cardiovascular events
    • Neurologic, cognitive, and memory deficits are common
    • Sleep Sleep Sleep is a reversible phase of diminished responsiveness, motor activity, and metabolism. This process is a complex and dynamic phenomenon, occurring in 4-5 cycles a night, and generally divided into non-rapid eye movement (NREM) sleep and REM sleep stages. Physiology of Sleep disorders and mood disorders are common
    • Persistent seizure disorder is common
    • Anosmia is common

Screening

It is reasonable to offer screening (neuroimaging) to 1st-degree relatives of patients with SAH for saccular aneurysms.

Differential Diagnosis

  • Ischemic stroke: an ischemic infarct of the cerebral parenchyma caused by occlusion of a cerebral artery by atherosclerotic lesions or cardioembolic emboli. Ischemic stroke presents with neurologic deficits and/or altered mental status/level of consciousness that depends on the size and location of the infarct. Diagnosis is clinical and confirmed by neuroimaging. Management includes initial stabilization, possible cerebrovascular intervention, addressing identifiable underlying etiologies (severe hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension, embolus), and management of cardiovascular risk factors. 
  • Other hemorrhagic cerebral conditions: carotid/cerebral artery dissection, epidural hemorrhage Epidural Hemorrhage Epidural hemorrhage (EDH) is an event characterized by bleeding into the epidural space between the dural layers of the meninges and the skull. The primary mechanism triggering bleeding is trauma (i.e., closed head injury), which causes arterial injury, most commonly middle meningeal artery injury. Epidural Hemorrhage, intraparenchymal hemorrhage, and subdural hemorrhage Subdural Hemorrhage Subdural hemorrhage (SDH) is bleeding into the space between the dural and arachnoid meningeal layers surrounding the brain. The most common mechanism triggering the bleeding event is trauma (e.g., closed head injury) causing a tearing injury to the extracerebral "bridging" veins. Subdural Hemorrhage are other hemorrhagic manifestations of the cerebral vasculature that can present with neurologic deficits and/or altered mental status/level of consciousness. Diagnosis is clinical and confirmed by neuroimaging. Management depends on the hemorrhagic etiology and includes initial stabilization, neurosurgical/endovascular consultation, management of ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP), and monitoring in a neurologic ICU. 
  • Hypertensive encephalopathy: neurologic deficit and/or altered mental status/level of consciousness that presents in the setting of severe hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension. Diagnosis is based on the presence of elevated blood pressure and neurologic signs/symptoms. Neuroimaging is useful to rule out ischemic or hemorrhagic cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke. Management centers around careful acute lowering of the blood pressure and long-term blood pressure management.

References

  1. Singer, R. (2021). Subarachnoid hemorrhage grading scales. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/subarachnoid-hemorrhage-grading-scales
  2. Singer, R. (2021). Aneurysmal subarachnoid hemorrhage: Epidemiology, risk factors, and pathogenesis. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/aneurysmal-subarachnoid-hemorrhage-epidemiology-risk-factors-and-pathogenesis
  3. Farhan, S. (2021). Perimesencephalic nonaneurysmal subarachnoid hemorrhage. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage
  4. Frahan, S. (2021). Nonaneurysmal subarachnoid hemorrhage. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/nonaneurysmal-subarachnoid-hemorrhage
  5. Singer, R. (2021). Aneurysmal subarachnoid hemorrhage: Treatment and prognosis. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/aneurysmal-subarachnoid-hemorrhage-treatment-and-prognosis
  6. Singer, R. (2020). Aneurysmal subarachnoid hemorrhage: Clinical manifestations and diagnosis. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/aneurysmal-subarachnoid-hemorrhage-clinical-manifestations-and-diagnosis
  7. Singer, R. (2020). Unruptured intracranial aneurysms. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/unruptured-intracranial-aneurysms
  8. Majeed, H, & Ahmad, F. (2021). Mycotic aneurysm. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK560736/ 
  9. Hacein-Bey, L, & Provenzale, JM. (2011). Current imaging assessment and treatment of intracranial aneurysms. AJR. American journal of roentgenology, 196(1), 32–44. https://doi.org/10.2214/AJR.10.5329

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