HOME

TheInfoList



OR:

An external ventricular drain (EVD), also known as a
ventriculostomy Ventriculostomy is a neurosurgical procedure that involves creating a hole (stoma) within a cerebral ventricle for drainage. It is most commonly performed on those with hydrocephalus. It is done by surgically penetrating the skull, dura mater, ...
or extraventricular drain, is a device used in
neurosurgery Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty concerned with the surgical treatment of disorders which affect any portion of the nervous system including the brain, spinal cord and pe ...
to treat
hydrocephalus Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased pressure inside the skull. Older people may have headaches, double vision, poor balance, urinary incon ...
and relieve elevated
intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adult. ...
when the normal flow of
cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the b ...
(CSF) inside the brain is obstructed. An EVD is a flexible plastic catheter placed by a
neurosurgeon Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty concerned with the surgical treatment of disorders which affect any portion of the nervous system including the brain, spinal cord and per ...
or neurointensivist and managed by
intensive care unit 220px, Intensive care unit An intensive care unit (ICU), also known as an intensive therapy unit or intensive treatment unit (ITU) or critical care unit (CCU), is a special department of a hospital or health care facility that provides intensiv ...
(ICU) physicians and nurses. The purpose of external ventricular drainage is to divert fluid from the ventricles of the brain and allow for monitoring of
intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adult. ...
. An EVD must be placed in a center with full neurosurgical capabilities, because immediate neurosurgical intervention can be needed if a complication of EVD placement, such as bleeding, is encountered. EVDs are a short-term solution to hydrocephalus, and if the underlying hydrocephalus does not eventually resolve, it may be necessary to convert the EVD to a
cerebral shunt A cerebral shunt is a device permanently implanted inside the head and body to drain excess fluid away from the brain. They are commonly used to treat hydrocephalus, the swelling of the brain due to excess buildup of cerebrospinal fluid (CSF). If ...
, which is a fully internalized, long-term treatment for hydrocephalus.


EVD placement

The EVD catheter is most frequently placed by way of a twist-drill craniostomy placed at
Kocher's point Kocher's point is a common entry point through the frontal bone for an intraventricular catheter to drain cerebrospinal fluid from the anterior horn of the lateral ventricle. It is located 2–3 centimeters lateral to the midline (at approximately t ...
, a location in the
frontal bone The frontal bone is a bone in the human skull. The bone consists of two portions.''Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, part ...
of the skull, with the goal of placing the catheter tip in the frontal horn of the
lateral ventricle The lateral ventricles are the two largest ventricles of the brain and contain cerebrospinal fluid (CSF). Each cerebral hemisphere contains a lateral ventricle, known as the left or right ventricle, respectively. Each lateral ventricle resembl ...
or in the
third ventricle The third ventricle is one of the four connected ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and left latera ...
. The catheter is typically inserted on the right side of the brain, but in some cases a left-sided approach is used, and in other situations catheters are needed on both sides. EVDs can be used to monitor intracranial pressure in patients with
traumatic brain injury A traumatic brain injury (TBI), also known as an intracranial injury, is an injury to the brain caused by an external force. TBI can be classified based on severity (ranging from mild traumatic brain injury TBI/concussionto severe traumatic ...
(TBI),
subarachnoid hemorrhage Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain. Symptoms may include a severe headache of rapid onset, vomiting, decreased level of cons ...
(SAH), intracerebral hemorrhage (ICH), or other brain abnormalities that lead to increased CSF build-up. In draining the ventricle, the EVD can also remove blood products from the ventricular spaces. This is important because blood is an irritant to brain tissue and can cause complications such as
vasospasm Vasospasm refers to a condition in which an arterial spasm leads to vasoconstriction. This can lead to tissue ischemia and tissue death (necrosis). Cerebral vasospasm may arise in the context of subarachnoid hemorrhage. Symptomatic vasospasm or de ...
.


Ongoing care

The EVD is leveled to a common reference point that corresponds to the skull base, usually the tragus or
external auditory meatus The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the pinna to the eardrum and is about in length and in diameter. Struct ...
. The EVD is set to drain into a closed, graduated burette at a height corresponding to a particular pressure level, as prescribed by a healthcare professional, usually a
neurosurgeon Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty concerned with the surgical treatment of disorders which affect any portion of the nervous system including the brain, spinal cord and per ...
or neurointensivist. Leveling the EVD to a set pressure level is the basis for
cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the b ...
(CSF) drainage;
hydrostatic pressure Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body "fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an imme ...
dictates CSF drainage. The fluid column pressure must be greater than the weight of the CSF in the system before drainage occurs. It is therefore important that family members and visitors understand the patient's head of bed position cannot be changed without assistance. An example of a healthcare provider order regarding an EVD is: set EVD to drain CSF for ICP > 15 mm Hg, check and record cerebrospinal fluid drainage and
intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adult. ...
at least hourly. Continuous CSF drainage is associated with a higher risk of complications. The
cerebral perfusion pressure Cerebral perfusion pressure, or CPP, is the net pressure gradient causing cerebral blood flow to the brain (brain perfusion). It must be maintained within narrow limits because too little pressure could cause brain tissue to become ischemic (having ...
(CPP) can be calculated from data obtained from the EVD and systemic blood pressure. In order to calculate the CPP the
intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adult. ...
and
mean arterial pressure In medicine, the mean arterial pressure (MAP) is an average blood pressure in an individual during a single cardiac cycle. MAP is altered by cardiac output and systemic vascular resistance. Testing Mean arterial pressure can be measured direct ...
(MAP) must be available. CPP=MAP-ICP


Complications

EVD placement is an invasive procedure. It is associated with several potential complications:


Bleeding

Bleeding can occur along the EVD insertion tract or in the several layers of the meninges that prohibit passage into the brain. If drilling or dural puncture is not successful, the surgeon may dissect away dura and create a secondary bleed known as an epidural or subdural hemorrhage. Bleeding from EVD placement can be life-threatening and can require neurosurgical intervention in some cases. The risk of hemorrhage with EVD placement is increased if the patient suffers from
coagulopathy Coagulopathy (also called a bleeding disorder) is a condition in which the blood's ability to coagulate (form clots) is impaired. This condition can cause a tendency toward prolonged or excessive bleeding (bleeding diathesis), which may occur spo ...
.


Mechanical

Mechanical complications from EVD placement can be categorized into: *Malplacement If the EVD is not placed with the tip of the catheter in the lateral or third ventricle, it is considered malplaced. If the catheter crosses critical brain regions such as the
internal capsule The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the ...
or the upper
brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...
, malplacement can be symptomatic. *Obstruction Obstruction/occlusion of EVD commonly due to fibrinous/clot like material or kinking of the tube. The brain can swell due to pressure build up in the ventricles and permanent brain damage can occur. Physicians or nurses may have to adjust or flush these small diameter catheters to manage medical tube obstructions and occlusions at the intensive-care bedside. *Migration After EVD placement, the drain is tunneled subcutaneously and secured with
surgical suture A surgical suture, also known as a stitch or stitches, is a medical device used to hold body tissues together and approximate wound edges after an injury or surgery. Application generally involves using a needle with an attached length of threa ...
s and/or
surgical staple Surgical staples are specialized staples used in surgery in place of sutures to close skin wounds or connect or remove parts of the bowels or lungs. The use of staples over sutures reduces the local inflammatory response, width of the wound, ...
s. However, it is possible for the EVD to dislodge or migrate. This will cause the tip of the drain to migrate away from its intended position and provide inaccurate ICP measurement or lead to occlusion of the drain.


Infection

The EVD is a foreign body inserted into the brain, and as such it represents a potential portal for serious infection. Historically, the rate of infections associated with EVDs has been very high, ranging from 5% to > 20%. Infections associated with EVDs can progress to become a severe form of brain infection known as
ventriculitis Ventriculitis is the inflammation of the ventricles in the brain. The ventricles are responsible for containing and circulating cerebrospinal fluid throughout the brain. Ventriculitis is caused by infection of the ventricles, leading to swelling ...
. Protocols designed to reduce the rate of EVD infections have been successful, applying
infection control Infection prevention and control is the discipline concerned with preventing healthcare-associated infections; a practical rather than academic sub-discipline of epidemiology. In Northern Europe, infection prevention and control is expanded from ...
'bundle' approaches to reduce the rate of infection to well less than 1%.


Neurological

Although neurological deficits from passing the EVD catheter across the brain are uncommon, there can be an association of a patient's poor neurological status with EVD malplacement. In one report, the EVD was inserted too deeply into the fourth ventricle; the authors hypothesized that the patient's coma was due to irritation of the recticular activating system. The patient's level of consciousness improved after the EVD was adjusted.


References

{{reflist Medical drains Neurosurgery