Pediatric emergency medicine trisk 1165

TABLE 135.4 SIGNS AND SYMPTOMS OF SHUNT INFECTION IN PATIENTS WITHOUT WOUND INFECTION Change in sensorium Irritability Fever Vomiting Adbominal pain Shunt obstruction Adapted with permission from Odio C, McCracken GH, Nelson JD CSF shunt infections in pediatrics: a seven-year experience Am J Dis Child 1984;138:1103–1108 The peritoneal portion of the shunt may become infected through the shunt mechanism or via a primary peritoneal infection Peritoneal infection can result in loculated, cystic pools of infection around the terminal portion of tubing (pseudocysts) These infections may be indolent in their presentation, and the shunt tap from the reservoir may not show evidence of infection Shunt nephritis is a rare but serious complication of ventricular–atrial shunts Renal deposition of antigen–antibody complexes leads to complement activation, which damages the renal tissue Unfortunately, the child with an infected CSF shunt may present with nonspecific signs and symptoms ( Table 135.4 ) Children commonly develop symptoms of shunt malfunction, such as lethargy or irritability Meningismus is not often present Infection may also manifest as abdominal complaints, such as pain or vomiting, especially when the infection involves the distal catheter tip Fever is not always present in patients with shunt infections and is uncommonly the only sign As previously mentioned, infection is most common within a few months of the shunting procedure, is uncommon after months, and is rare more than year afterward These rules are less applicable in patients with gram-negative infections, which can occur later after shunt placement Children with gram-negative infections are more often bacteremic, if not septic appearing A wound infection overlying any portion of the shunt mechanism can manifest as erythema and tenderness or swelling along the shunt tract or over the reservoir A reddened tract of skin paralleling the shunt tubing from the head to chest is often detected and is virtually diagnostic of shunt infection In the absence of overlying infection, aspiration of a small amount of CSF from the shunt system should be performed to identify the presence of a bacteriologic cause of shunt infection This procedure is usually performed by a neurosurgeon, if possible The results of this procedure are sometimes helpful but not always determinate; the white blood cell (WBC) count can range from to 2,600 if the shunt is infected, and patients without infection can have up to 500 WBCs/mm3 In the absence of a positive culture result, many clinicians use more than 50 WBCs/mm3 in the presence of fever, shunt malfunction, and neurologic or abdominal symptoms to arrive at the diagnosis Gram stain of the fluid may be helpful in broadening antibiotic coverage if gram-negative organisms are present However, the Gram stain should not be used to narrow the usual antibiotic coverage until the culture and sensitivities of the causative organisms are obtained Most neurosurgeons are reluctant to perform shunt taps in patients with subtle neurologic complaints and vague infectious signs because of the purported risk of “seeding” the shunt with skin flora This risk has never been clearly defined prospectively, but in a neurologically normal child, it is prudent to perform a thorough fever workup for common infectious sources to avoid even a small risk of causing a shunt infection Patients with ventriculoperitoneal shunt (VPS) who complain of abdominal pain, with or without fever, may benefit from abdominal radiographs and ultrasound to search for a loculated CSF collection or pseudocyst, or visceral perforation Various permutations of medical and surgical therapy have been suggested for the treatment of proximal CSF shunt infections Medical therapy alone has been found to have a relatively low success rate compared with a combined medical– surgical approach Potential surgical interventions include immediate shunt replacement or the insertion of an extraventricular drainage (EVD) catheter, followed by delayed shunt revision The latter method improves the bacteriologic cure rate significantly, although it must be performed in an institution that is facile in managing and preventing infection of EVD catheters Distal shunt infections are treated with antibiotics and temporary externalization of the distal shunt catheter Medical therapy provided in the ED for children with suspected CSF shunt infections is limited to the administration of broad-spectrum IV antibiotics The antibiotics should be effective against S epidermidis, S aureus , and gramnegative organisms, as well as any organisms identified from previous infections, and expanded to treat Pseudomonas aeruginosa infections in severely ill patients A reasonable choice of empiric therapy is cefepime followed by vancomycin Ciprofloxacin can be substituted for Cefepime in patients with documented allergy Eventually, antibiotic therapy may be narrowed on the basis of culture and sensitivity results of the shunt fluid Overdrainage Occasionally, children with CSF shunts experience symptoms related to the system working too well, resulting in low ICP Such overshunting is more common in infants who have had initial shunting before months of age One consequence is the slit ventricle syndrome, in which the ventricles collapse around the proximal catheter port and block further drainage The best means of diagnosing intracranial hypotension is the patient’s history rather than physical examination or radiographic analysis Young infants may exhibit sunken fontanels, microcephaly, or overriding parietal bones Older children may exhibit intermittent symptoms of headache, nausea, vomiting, and lethargy The drainage of CSF shunts increases when the patient is upright and decreases when supine In contrast to the classic timing of symptoms related to increased ICP, patients with intracranial hypotension are often worse when in the standing position or after they are awake for several hours Lying supine for a few hours tends to relieve symptoms of slit ventricle syndrome Many patients with CSF shunts have CT scans that reveal small ventricles; however, only a small proportion of these patients have slit ventricle syndrome Therefore, the CT scan is best used to differentiate between shunt malfunction and other causes of symptoms rather than to diagnose an overdrainage problem Chronic or recurrent episodes of slit ventricle syndrome can be addressed surgically by upgrading the resistance of the valve or by insertion of an antisiphon device Oral analgesics may be helpful in managing mild cases Other Complications Other complications related to CSF shunts deserve mention The most common of these complications is a benign postoperative leakage of CSF around the proximal shunt tubing into the subgaleal space around the reservoir The resulting extracranial fluid collection resolves spontaneously, so drainage of this fluid should be avoided In non-postoperative patients, a new extracranial fluid collection can suggest shunt malfunction, as the CSF takes the newest “path of least resistance.” Patients with CSF shunts have an increased risk of seizures compared with the general population These seizures often begin years after shunt placement and are caused by epileptogenic scars They are more common in patients with other abnormalities correlated with seizures, such as porencephalic cyst or intracranial hemorrhage Overdrainage can lead to shrinkage of brain tissue and concomitant subdural accumulations (hematomas or CSF effusions referred to as hygromas) Similarly, a decreased rate of head growth because of overdrainage can result in craniosynostosis in the infant Some important, albeit rare, complications are related to specific types of CSF shunts The distal portions of a VPS can migrate and cause perforation of the colon or genital tract This section of tubing can act as a fulcrum for intestinal volvulus Ascites and abdominal cysts can form as a result of drainage of excess fluid into the peritoneum Increased intra-abdominal pressure can precipitate the formation of an inguinal hernia through a patent processus vaginalis Ventricular–vascular shunts can be associated with an increased risk of bacteremia Shunt nephritis can result from complement activation and renal deposition of immune complexes Patients with ventriculoatrial shunts can experience cardiac arrhythmias or atrial perforation, usually perioperatively Bacterial endocarditis, cardiac foreign body, and mural thrombus are rare but notable complications of vascular shunts After ventriculoatrial shunt, the pleural cavity is the third most common site for distal catheter placement These can lead to pleural effusions and related complications Often, they are placed temporarily to allow “bowel rest” after peritonitis but then revised to a standard VPS when the infectious peritoneal issues have resolved Avoiding Pitfalls With New Endoscopic Technology Neurosurgeons are increasingly using endoscopic techniques in the management of pediatric hydrocephalus, particularly in obstructive hydrocephalus and the treatment of intracranial cysts Children who have previously been shuntdependent may undergo endoscopic third ventriculostomy (ETV), which is effectively an internal shunt that bypasses a stenosed aqueduct of Sylvius Parents and emergency clinicians should be cognizant that these children are still subject to the same manifestations of shunt failure; the presence of appropriate signs and symptoms of raised ICP should initiate the same evaluation and criteria for possible intervention outlined earlier in this section It should be noted that while not subject to the myriad malfunctions that befall patients with implanted hardware such as infection, erosion, disconnection, and clogging, patients with ETVs can suffer restenosis of their fenestration site, with reports of closure as late as years after the initial procedure  ... Endoscopic Technology Neurosurgeons are increasingly using endoscopic techniques in the management of pediatric hydrocephalus, particularly in obstructive hydrocephalus and the treatment of intracranial... which is effectively an internal shunt that bypasses a stenosed aqueduct of Sylvius Parents and emergency clinicians should be cognizant that these children are still subject to the same manifestations