Management of Ventriculoperitoneal Shunts in the Emergency Department

The ventriculoperitoneal shunt (VPS) is a rarely encountered but often intimidating device that can present with many complications. This article discusses the indications and complications of VPS and its management in the emergency department (ED

Introduction

The ventriculoperitoneal shunt (VPS) is a device that diverts cerebrospinal fluid (CSF) from the cranial vault to the abdominal cavity, or the peritoneum. Ventriculoperitoneal shunts are placed for various reasons with some 30,000 inserted yearly.¹ Although shunt insertion is a common neurosurgical procedure, revision rates are high in the pediatric population and complication rates in adults range between 17-33% annually.² Emergency physicians will encounter patients with shunt complications and must know the appropriate troubleshooting techniques in the ED.

Indications

Hydrocephalus results from abnormal or excessive cerebrospinal fluid accumulation (CSF) and is the main indication for VPS insertion. CSF is created and circulates within the ventricular system, which consists of four ventricles within the brain. The term, communicating hydrocephalus is used when CSF is unable to be reabsorbed into the body, while non-communicating or obstructive hydrocephalus occurs when there is a physical blockage within the ventricles.³ Several causes of hydrocephalus may warrant VPS insertion; these include normal pressure hydrocephalus, idiopathic intracranial hypertension, complications from subarachnoid hemorrhage, a variety of congenital disorders (i.e. Dandy-Walker, variants of spinal bifida), malignancy and infection due to cytomegalovirus, rubella, and toxoplasmosis.⁴

The VPS consists of four components: a proximal ventricular catheter, a one-way valve, a reservoir and a distal peritoneal catheter.⁴ The valve and reservoir are housed together under the scalp. The standard valve continuously drains CSF when the ventricular pressure is greater than 10 mmHg, while some valves are programmable with a pressure gauge set for an adjustable flow rate.¹ The VPS runs from the ventricular system out of the skull and under the scalp as it traverses down into the peritoneal cavity beneath the skin by way of the neck and chest wall. Other alternatives to VPS include shunting to the atria, lung space or more invasive interventions like ventriculostomy.

Complications

VP shunt-related complications present with a variety of vague symptoms. The chief complaints of VPS-associated failure include headache, fever, nausea, vomiting, abdominal pain, lethargy, ataxia and mental status changes including coma.⁶ These symptoms can arise suddenly or over several days.⁶ In the presence of a severe increase in intracranial pressure (ICP) secondary to VPS failure, patients may present with a decreased level of consciousness, changes in personality and cognition, seizures and bradycardia.⁷ The most common causes of VPS malfunction include functional failure, mechanical failure and infection.

Functional VPS failures occur in the setting of over-drainage or slit ventricle syndrome and under-drainage. Overdrainage leads to a reduction in CSF volume and puts patients at risk for subdural hematomas secondary to tearing of the bridging veins.⁸ The slit ventricle syndrome is a result of over-drainage resulting in small ventricular size on radiographic imaging.⁹ These patients may present with headaches and nausea that are exacerbated in the upright position. The factors that may contribute to over-drainage are most notably inherent valve malfunction. VPS under-drainage results from tissue occluding the apertures of the proximal shunt apparatus and will present with worsening hydrocephalus on brain imaging.

Mechanical failure may arise from misplacement, migration, disconnection and/or fracture of the VPS apparatus.¹⁰ The most common location for a fracture is along the clavicle or lower ribs. Migration occurs when a correctly placed catheter shifts, and drainage is partially or completely compromised.¹⁰Misplacement is the earliest sign of mechanical failure due to insertion into the brain parenchyma, temporal horn or choroid plexus with post-operative signs of shunt failure. Disconnection typically occurs shortly after insertion and may result in fluid accumulating at the skin site around the disconnection.¹⁰

Infection is the second most common cause of shunt failure and carries a risk of severe morbidity and mortality. ¹¹ Most VPS infections occur within the first two months after placement and are often due to skin flora such as staphylococcus aureus and epidermidis.^7,12 Patients with internal infections involving the shunt and CSF may present with altered mentation, headache and meningismus. Those patients with an external infection involving the tissue surrounding the shunt will present with local swelling, erythema, and tenderness.

Some patients may also experience abdominal complications as a result of increases in abdominal pressure or pseudocyst formation.¹⁰ A pseudocyst may form around the distal end of the peritoneal catheter and if large enough can cause severe abdominal pain. Computed tomography is the best imaging modality to assess for abdominal pseudocyst formation.

Management

The first part of the assessment for patients with VPS is to obtain a thorough history and neurological examination. On physical examination, clinicians should palpate for the reservoir and the valve below the scalp to identify any disconnections under the skin, overlying skin changes and overall appearance. A gentle reservoir compression can provide emergency physicians with information regarding proximal versus distal obstruction with a difficult compression representing a distal flow obstruction whereas a slow refill may suggest a proximal obstruction.¹⁰

The most common radiologic studies in patients with concern for VPS failure included CT of the brain and a shunt series X-ray.¹³ A shunt series includes an anteroposterior (AP) and lateral view of the skull, chest and abdomen to identify any mechanical causes of VPS malfunction such as fracture or displacement of the system. The skull X-ray may also provide information on the specific shunt used (i.e. Codman, Integra, Sophysa) and its current settings. These settings and valve type should be documented for future reference. In the context of significant clinical suspicion of shunt failure, neurosurgical consultation should be sought for further guidance.

In rare instances, VP shunt tapping or collection of CSF is indicated. CSF should be collected for patients that present with fever or high suspicion of VPS-associated infection. It is controversial within the literature whether VPS tapping is safe when a lumbar puncture will provide the same information and lower the risk of infection.⁴ Either can be performed, but neurosurgical consultation is advised. In the case of a decompensating patient, a VPS tap is reasonable, which will allow for the removal of excess CSF. To withdraw CSF from the reservoir under the skin, use a butterfly needle, IV tubing and a syringe under a sterile technique. Shunt pressure can be measured using a manometer from a lumbar puncture kit.

In the face of shunt failure, a rapid increase in ICP may occur and can result in herniation. When suspected, emergency medicine physicians must employ measures to reduce ICP whether by intubation and hyperventilation, hyperosmolar therapy and/or emergent neurosurgical decompression.

Conclusion

VPS are devices that emergency medicine physicians frequently encounter. These devices are prone to several complications along the apparatus with potentially devastating consequences. Providers must be skilled in diagnosing and treating acute VP shunt complications. The evaluation should begin with a thorough history and physical examination, followed by appropriate imaging, procedures, and prompt neurosurgical consultation if necessary.

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