Etiology of Hydrocephalus

The etiology of hydrocephalus as a risk factor for the development of infections has not been clearly shown. An association between the causal agent and a higher risk for shunt infection has rarely been found,^11,14 although a recent review described an association between obstructive hydrocephalus and rate of complications.¹⁵

Hydrocephalus following perinatal bleeding has been associated with a higher incidence of infection,¹⁶ but we could not establish such an association in our series of 964 operated patients.

Patient Age and Nutritional Status

Many reports stress the importance of age as a risk factor for infectious complications in patients who have a CSF shunt.^9,17 The risk of complications is mainly present in infants and elders. A multicenter study analyzing shunt complications in general found that younger children were at a higher risk of complications and malfunction; however, the study fails to specify whether these were infectious or obstructive.¹⁸

Nutritional status is yet another significant factor, as undernourished subjects seem to have a higher rate of infectious complications.¹⁹ Infant nutrition may also play an important role, and a lower incidence of infection has been described in breastfed infants.²⁰

Surgical Technique

The implantation technique of a ventriculoperitoneal or ventriculoatrial shunt is also extremely important. The absence of an appropriate strategy may turn a procedure normally representing low mortality and morbidity, and presumably requiring a short hospital stay, into a complicated procedure that eventually results in multiple reoperations, longer hospital stays, higher costs for the healthcare system, and potentially serious sequelae for the patient.

Shunt implantation is a procedure often performed by neurosurgical trainees who have inadequate experience in the technique; this factor may be critical for the development of postoperative infections.²¹

Many papers have shown that postoperative infection rates may be reduced by using a meticulous surgical technique.^7,11,22 Where possible, the procedure should be carried out in a dedicated neurosurgical operating room and be the first procedure of the day. The paramedic personnel involved in the procedure should be trained in prosthesis manipulation and instructed to maximally restrict circulation into and out of the operating room. Entrance to and exit from the operating room would only be allowed in emergency situations; where possible, the number of personnel within the operating room should be restricted to four professionals—an anesthesiologist, a nurse, a surgeon experienced in the management of hydrocephalus, and an assistant. Contaminated elements should be carefully placed away from the sterile sector of the operating room.

We recommend giving prophylactic antibiotic therapy at the time of anesthetic induction, as well as during the first 24 postoperative hours. A meta-analysis of recent reports showed the effectiveness of prophylactic antibiotic therapy in the reduction of infection rates.²³ The prophylactic antibiotic drugs scheme to be used should be designed after the bacterial flora prevailing in the healthcare site.

As far as individual patient care, the antiseptic procedure should be thorough; therefore, we recommend bathing the patient with povidone–iodine soap or a similar product 24 hours preoperatively. Immediately before the surgical procedure, the operating field must be washed three times with povidone–iodine soap using a nonsterile technique, and then the skin should be prepared another three times with povidone–iodine solution using a sterile technique. Placement of sterile fields should be meticulous and should try to expose the surgical area only, which should be covered with sterile drapes impregnated in iodoform (3M Ioban 2 Antimicrobial Incise Drapes EZ). Unnecessary surgical steps should be avoided to shorten the length of the procedure as much as possible.

The valve not only should suit the patient’s needs but also should be a device with which the surgical team is accustomed to working.

Many studies have investigated the association between antibiotic-impregnated shunt catheters and risk of infection. In vitro results²⁴ reported antibiotic-impregnated catheters afford a lower colonization risk, but reports of studies conducted in humans showed controversial results. Some authors stress the contribution of these devices to lower postoperative infection rates and thus recommend them as an effective tool.^25,26 Other reports have found no significant infection rate differences in patients who underwent the implantation of antibiotic-impregnated catheters.^23,27 This kind of devices could be used in patients with a history of previous infection or in high-risk cases, but regardless of the circumstance, the previously described perioperative care steps should be followed carefully.

Silastic exposure to room air must be minimized. For this reason, the sterile container should be opened exactly at the moment of implantation.

We recommend using forceps for implantation to avoid manipulation of the shunt system. Intraoperative preparation with povidone–iodine is useful, and some authors suggest immersing the shunt in a gentamicin solution bath.¹¹ The implementation of this kind of protocol has already been described by other authors^7,11,22 and proved to have high efficacy in preventing infection.

Presentation and Clinical Features of Shunt Infection

Presentation of shunt infections is highly variable, depending on the causal agent, the site of infection, and patient age. Many patients remain asymptomatic,²⁸ whereas others are oligosymptomatic or show signs and symptoms of increased intracranial pressure due to shunt malfunction. In neonates, clinical features of shunt malfunction include bulging fontanelle, irritability, vomiting, fever, and feeding difficulty. In older children and adults, the signs and symptoms tend to be nonspecific, though fever, headache, vomiting, meningism, and abdominal pain may suggest shunt infection. Up to 50% of shunt malfunctions may be explained by an underlying infection.²⁹

Occasionally, shunt infection signs are seen at the distal end, with abdominal symptoms that may vary from nontender focal peritoneal fluid collections to acute abdomen. The finding of abdominal fluid collections or pseudocysts is considered by many authors to be a sign suggestive of infection in patients with ventriculoperitoneal shunts,^30,31 although cystic fluid cultures often test negative.³² Early diagnosis of this complication by means of an abdomen computed tomography (CT) scan (Fig. 97-1) affords an effective management by externalizing the catheter, removing the shunt or re-placing the peritoneal catheter laparoscopically.^33,34

FIGURE 97-1 Oral and intravenous contrast-enhanced CT scan of the abdomen and pelvis. A large fluid collection (pseudocyst) is seen. Note the catheter inside the collection.

Infections associated with ventriculoatrial shunts are usually more severe and may cause bacteremia with a subsequent hemodynamic involvement on account of the close link between CSF and circulating blood flow, which could result in the formation of thrombi at the catheter tip and thus lead to endocarditis or thromboembolic events. Shunt nephritis is a glomerular disease produced by antibody deposits in the renal glomeruli and the production of complement, which is characterized by hematuria, anemia, liver and spleen enlargement, and nephrotic syndrome. Although shunt nephritis has a low incidence, it should be considered a potential diagnosis in patients who have a ventriculoatrial shunt.³⁵

Infections caused by skin organisms may present with redness and edema along the length of the shunt, wound dehiscence and shunt exposure, or purulent discharge through the wound (Fig. 97-2). This kind of infection is commonly external and occurs in neonates when CSF accumulates, particularly when CSF fistulas are present.³⁶