Risks and complications associated with ventriculoperitoneal shunt.
Many of the complications of VP shunt insertion are common to all procedures where extremity soft tissue dissection is performed:
Table: Neurosurgical Risks & Complications
Complications particular to VP shunt insertion include:
Complications of ventriculoperitoneal shunt placement include: ileus, catheter in brain, subdural hematoma, brain hematoma, neck hematoma, skin perforation, lung injury,
bowel injury, peritonitis, obstruction, infection, disconnection, and exposed catheter.
Failure of the normal propulsive activity of the muscles lining the walls of the intestines that moves material (food, fluid, etc.) forward along the digestive pathway from the stomach to the rectum.
Ileus is a frequent, almost always transient, complication of surgery in the abdomen, including
Immediate post operative
Ileus is usually detected shortly after surgery when the abdomen is auscultated (listened to) with a stethoscope and normal bowel sounds (of fluid and food moving through the intestines) are absent.
The intestines are very sensitive to manipulation.
Fluid and food that do not move forward collect and distend the proximal portion of the intestines and prevent the stomach from emptying, leading to vomiting.
Management of ileus is conservative. Usually just waiting for a day or two. If fluid accumulates in the stomach and vomiting occurs or seems likely it may be necessary to place a nasogastric (through the nose, down the throat, into the stomach) tube that is then attached to a suction device to empty the stomach.
The frequency of ileus following abdominal surgery is higher with larger surgeries.
Ileus can be prevented (or minimized) by minimizing the amount of intra-abdominal manipulation.
Shunt passer makes a tunnel under the skin through the subcutaneous tissues of the neck, chest, and upper abdomen
The ventricular catheter portion of the ventriculoperitoneal (VP) shunt system is usually inserted "blind", guided by reference to external landmarks on the patient's head. (Stereotactic techniques can be used for patients with small ventricles more easily missed with landmark-directed placement. Endoscopy is another alternative for ventricular catheter placement in patients with complicated ventricular anatomy. Landmark-guidance is by far the most common technique used. If the catheter is misdirected it can end up in the brain tissue instead of in the ventricle. Even if CSF initially comes out the surgeon's end, it may do so because fluid entered through the holes in the tip during a passage through the ventricle into the brain (illustration).
As long as even a few of the holes at the tip of the ventricular catheter are in the ventricle there will be CSF flow out. Partial location in brain parenchyma is compatible with CSF flow.
Intraoperative - misplacement of the tip of the ventricular catheter in the brain should be suspected intraoperatively if no cerebrospinal (CSF) flows out from the surgeon's end of the catheter. In patients with very small ventricles the absence of CSF flow may be due to the small amount of fluid, and in patients with very low intracranial pressure their may not be enough of a pressure gradient to push the fluid out of the ventricle.
Immediate post operative
if no CSF comes out in a patient with normal to large ventricles expected to contain fluid under normal to high pressure (the vast majority of those shunted) a post operative CT will be required to confirm that the ventricular catheter is not sitting in the anterior horn of the lateral ventricle.
Delayed post operative
fluid flowing out from his or her end of the ventricular catheter during passage may mislead the surgeon into believing that the catheter tip is in the ventricle (initial CSF flow with tip ultimately in brain tissue described above). A CT scan to check for ventricular placement may not be obtained for several days in such cases and then usually because an expected immediate or rapid improvement in the patient's condition (patients shunted for acute hydrocephalus) does not occur.
Delayed - some patients are shunted for chronic hydrocephalus and are not expected to show improvement for several days or weeks (if at all). In these patients parenchymal (in brain tissue) placement of a ventricular catheter may be discovered only weeks, months, or years after surgery, on a CT scan frequently obtained for an indication other than evaluation of catheter position.
Surgeon -- planning: catheter in brain ventriculoperitoneal shunt placement may be considered due to a planning error if the patient's ventricles are very small and stereotactic placement capabilities were available.
Using a catheter too long may overshoot the ventricle when passed until the surgeon's end is flush with the outer skull (see ventriculoperitoneal shunt insertion procedure).
Surgeon -- judgment: catheter in brain ventriculoperitoneal shunt placement where the surgeon misjudged landmarks by which the catheter was passed.
Patient -- anatomy: in some patients the relationship between the ventricles and surface landmarks used for "blind" cannulation may be irregular leading to catheter in brain ventriculoperitoneal shunt.
Patient -- disease: distortions due to the patient's neurosurgical disease (tumor, hematoma, etc.) may alter ventricle-surface landmarks relationships.
The consequence of a misplaced ventricular catheter depends on the severity and acuity of the patient's hydrocephalus.
Technique:
One technique to prevent placement of the distal ventricular catheter tip in brain parenchyma (instead of ventricle) is to place the tip at target endoscopically rather than blindly with reference to external cranial landmarks (the standard technique).
The surgeon who places ventricular catheters should be comfortable with the surface anatomy the skull and the landmarks from which he or she will set the trajectory the catheter will take from the skin to the ventricle.
Bridging veins span the space between the surface of the brain and the midline sagittal sinus (into which they drain). Normally these vessels are not under any tension because the brain-to-sinus distance is small. As the volume of the brain decreases, the distance of its outer surface from the inner surface of the skull (essentially that across which the bridging veins stretch) increases -- increasing the tension on the veins. At some critical tension the veins rupture releasing blood into the subdural space (subdural hematoma). The larger the ventricular volume is (ie: the greater the degree of hydrocephalus) prior to shunting, the greater the increase in distance over which the bridging veins will be stretched following placement of a shunt when the ventricular volume decreases.
Immediate post operative: Subdural hematoma following ventriculoperitoneal shunt is rarely recognized immediately post-operatively. This may be because these hematomas form and enlarge slowly.
Delayed post operative: Subdural hematoma after ventriculoperitoneal shunt usually presents with headache or progressive neurologic deficit days or weeks after insertion of a VP shunt.
Some VP shunt-related subdural hematomas are discovered only incidentally (ie: no symptoms (office symptoms) or signs) when a patient is scanned (CT or MRI) to rule out a suspected non-shunt-related pathology (such as a tumor or stroke). Others are discovered on "routine" follow up scanning months or years after a shunt is placed, in a patient who is totally asymptomatic.
Surgeon -- planning:
Patients at high risk for developing hematomas, especially frail, elderly patients with long-standing dementia and multiple medical problems should not be shunted for any but the most desperate cases, and these only after the patient (and family) have been fully apprised of the high risk of serious morbidity and mortality..
Surgeon -- judgment:
An important surgical decision especially in shunting for normal pressure hydrocephalus is the selection of the valve due to the high propensity for the development of subdural fluid collections in the elderly population which is the same population most frequently shunted for normal pressure hydrocephalus.
Patient -- physiology, disease, anatomy:
Patients with massive hydrocephalus and advanced atrophy of the brain are at a high risk for development of subdural hematoma after shunting.
Life threatening: subdural hematoma ventriculoperitoneal shunt
Neurologic deficit: subdural hematoma ventriculoperitoneal shunt
Pain: subdural hematoma ventriculoperitoneal shunt
Neurophysiologic compromise: subdural hematoma ventriculoperitoneal shunt
The frequency of subdural hematoma complicating VP shunt insertion is
Infection of a VP shunt is a dreaded complication because it frequently requires revision (removal and replacement of the entire system.
Passage of a catheter through the brain can traumatize vessels large enough to bleed a clinically significant volume.
Intraoperative: brain hematoma ventriculoperitoneal shunt
Immediate post operative: brain hematoma ventriculoperitoneal shunt
Delayed post operative: brain hematoma ventriculoperitoneal shunt
Delayed: brain hematoma ventriculoperitoneal shunt
Surgeon -- technique:
brain hematoma usually results from trauma to small blood vessels in the brain parenchyma (as opposed to the large vessels in the subarachnoid space on the brain's surface usually spared during passage of the ventricular catheter.
It is unclear whether any particular technique -- faster, slower, with a twist - is less traumatic than any other.
Life threatening:
brain hematomas that reach a size where they contribute to increased intracranial pressure and tissue shifts (herniation) are life threatening.
Neurologic deficit:
The common locations for cortical entry and passage of VP shunt ventricular catheters are both relatively "ineloquent" -- they do not mediate any of the functions testable in the course of a standard neurologic examination. Although the parenchymal entry sites avoid eloquent cortex, a traumatic passage parenchymal hematoma that continues to enlarge can impinge on eloquent areas and cause deficits (such as aphasia and hemiparesis) on neurologic exam.
Neurophysiologic compromise:
Large enough brain hematomas can be contribute to increased intracranial pressure.
Reoperation:
A clinically significant (causing symptoms -- headache ..., and signs -- aphasia, hemiparesis...) brain hematoma may require a return to the operating room.
A clinically significant hematoma should be removed. A clinically one found on CT in an asymptomatic patient should be left alone.
The frequency of brain hematoma following ventriculoperitoneal shunt insertion is very low. The incidence will never be known because besides those discovered on CT scans done for an unrelated indication, a large number of catheter passage-related hematomas are clinically silent -- only those that cause symptoms and signs are imaged and diagnosed.
Equipment: brain hematoma ventriculoperitoneal shunt
Planning: Subdural hematoma following insertion of a ventriculoperitoneal shunt
Technique: Subdural hematoma following insertion of a ventriculoperitoneal shunt
VP shunt systems include several components in sequence that provide a continuous pathway for CSF flow from the ventricle in the brain to the peritoneal space in the abdomen.
disconnection between elements of the ventriculoperitoneal shunt system results in failure of drainage which can result in:
Pain: headache
Neurophysiologic compromise: increased intracranial pressure
disconnection ventriculoperitoneal shunt
No consequence:
However, some patients with VP shunts placed long ago for now unclear indications who are no longer (or were never truly) drainage dependent, are found on imaging of the head, neck, chest, or abdomen, done for non-shunt related indications, to have disconnected segments.
The subcutaneous tunnel is located a few millimeters below the skin surface in the space between the subcuticular and superficial muscule fascial layers of the head, neck, chest, and abdomen.
Intraoperative: skin perforation ventriculoperitoneal shunt
Immediate post operative: skin perforation ventriculoperitoneal shunt
Delayed post operative: skin perforation ventriculoperitoneal shunt
Delayed: skin perforation ventriculoperitoneal shunt
ventriculoperitoneal shunt insertion
Prolongation of surgery:
skin perforation ventriculoperitoneal shunt
Skin perforation during tunneling
The frequency of neck hematoma complicating ventriculoperitoneal shunt is low.
Technique:
Perforation of the skin during tunneling can be avoided by making sure that the advancing end of the tunneling device does not point upwards (toward the skin surface) and maintaining control during even forceful advancing between the subcutaneous tissues.
Bleeding - Injury to the external jugular vein or other vascular structures in the neck can result in bleeding and swelling appreciated at the time of surgery or afterwards
Intraoperative: neck hematoma ventriculoperitoneal shunt
Immediate post operative: neck hematoma ventriculoperitoneal shunt
Delayed post operative: neck hematoma ventriculoperitoneal shunt
Delayed: neck hematoma ventriculoperitoneal shunt
Life threatening: the trajectory of a ventricular catheter from a either a coronal or posterior parietal (see ventriculoperitoneal shunt insertion procedure) skin-skull entry avoids most brain structures that would cause death on catheter entry. Placement of a catheter into the brainstem could be life threatening.
Neurologic deficit: Neurologic deficit can result from placement of the catheter into structures nearby (wrong trajectory) or beyond (wrong catheter length) the desired catheter tip target.
Neurophysiologic compromise: Increased intracranial pressure (ICP) associated with hydrocephalus is probably the most common indication for VP shunt placement. A shunt that is nonfunctional because its distal (draining) tip is in brain tissue rather than CSF will not lower ICP.
Reoperation: reoperation may be required for ventricular catheter misplaced into brain parenchyma to: relieve a neurologic deficit or to establish CSF drainage.
No consequence: in patients
Pneumothorax - Passage of the tunneling catheter below the clavicle into the lung perforates the inner (visceral) latter of the pleura allowing air to escape from the lung into the space between the visceral and pariteral (outer) pleural layers, resulting in pneumothorax. Sometimes this is recognized intraoperatively but may not be until postoperatively when the patient complains of chest pain or is found to have difficulty breathing
The intestines lie just deep to the inner layer of peritoneum and are vulnerable to injury to injury during the dissection and exposure of the site for placement of the peritoneal end of a VP shunt system.
Intraoperative:
Injury to the bowel may be recognized intraoperatively if bowel contents of distinctive appearance and odor appear in the surgical field during lysis (breaking up) of adhesions (scars between loops of intestine or between the intestines and the abdominal wall [parietal peritoneum]) during placement of the peritoneal end of the ventriculoperitoneal shunt drainage tubing.
Immediate post operative:
Peritonitis (bowel contents causing irritation of the peritoneum) following perforation of intestine may present as early as Recovery with a stiff, exquisitely tender, silent, abdomen.
Delayed post operative:
Delayed:
Life threatening:
injury to bowel ventriculoperitoneal shunt
Pain:
injury to bowel during placement of a ventriculoperitoneal shunt can result in painful peritonitis but unless it does is likely to be painless. Surgery to repair injured bowel may be more extensive than would have been an uncomplicated VP shunt placement, with more postoperative pain than anticipated at the time he or she signed the surgical consent.
Physiologic compromise: injury to bowel ventriculoperitoneal shunt
Prolongation of surgery: injury to bowel ventriculoperitoneal shunt
Reoperation:
No consequence:
Peritonitis is an infection in the peritoneal cavity.
Immediate post operative:
peritonitis due to a large bowel content spill can present within a few hours of ventriculoperitoneal shunt insertion.
Delayed post operative: peritonitis following ventriculoperitoneal shunt insertion
Delayed: peritonitis following ventriculoperitoneal shunt insertion
Drainage of cerebrospinal fluid (CSF) through a ventriculoperitoneal (VP) shunt requires that the tubing from the ventricle to the reservoir, from the reservoir to the valve, and from the valve to the peritoneal cavity (abdomen) all be open (unobstructed).
Immediate post operative:
Because the production of CSF continues
Delayed post operative:
Restoration of drainage is required when VP shunt obstruction results in inadequate CSF drainage with hydrocephalus.
The frequency of VP shunt obstruction is
VP shunt obstruction can be avoided
The VP shunt tubing lies a few millimeters below the skin surface