The installation of a ventriculoperitoneal shunt device (VPS) is one of the most common procedures in neurosurgery [1]. Dysfunction and infection of these devices are common complications, risking morbidity and mortality and increasing treatment costs. Incidence is estimated to be between 10% and 20% and varies according to case definition, period studied, and other factors [2], [3]. At our health center, incidence is 7.8% for the first installation and 23% for following installations [4].

Ventricular infection should be suspected in a VPS patient who presents with fever. This is usually associated with symptoms of valvular dysfunction, such as headache, nausea, or compromised consciousness [5]. In addition, a patient may present with focal neurological deficits, nuchal rigidity, seizures, and photophobia. In a patient with a peritoneal shunt, certain abdominal signs should raise suspicion of device infection. Demonstration of bacteremia in the absence of any another cause in a patient with a Ventriculoatrial Shunt points to infection [6].

Routine cerebrospinal fluid (CSF) cytochemical tests are moderately useful, since some alterations may be secondary to an infection or due to the shunt itself (elevated protein, hemorrhage). In turn, a CSF without alterations does not completely rule out a ventricular infection [7], [8]. There is no gold standard CSF laboratory parameter to confirm or rule out infection with certainty. A normal cell count does not rule out infection. Moreover, alterations to cell count may depend on the infectious agent present [9].

Lactate has emerged as a marker of inflammation in CSF. It allows identification of a bacterial infection of the central nervous system as opposed to a viral infection or inflammation by another cause (aseptic meningitis) [10], [11]. With infections, lactate increases due to inflammation and cerebral ischemia, which increases anaerobic metabolism [12]. Lactate can also be used for monitoring therapy [13].

For neurosurgical patients, the relationship is less clear. In adult patients, lactate has greater positive predictive value than hypoglycorrhachia or pleocytosis in the diagnosis of post-neurosurgical meningitis [14], [15]. A cut-off point close to 3.45 mmol/L lactate has a sensitivity of close to 90% and a specificity of over 85% [16] and is not altered by the presence of blood in the CSF [17]. Recent studies in ventriculostomy users have shown low sensitivity and specificity [18], but a good negative predictive value [19] (if low, bacterial infection can be ruled out).

In pediatrics, current evidence is less abundant. Regarding external ventricular drainage, one study found no significant difference (although, in the case of infection, the mean level of lactate was higher) [20].

To our knowledge, only one study has investigated the usefulness of lactate in confirming suspected infection in pediatric patients with a VPS [21]. The authors found a higher mean lactate level in patients with suspected infection of the peritoneal ventricular drainage, positive culture, and a negative predictive value of 96% with a cut-off point of 2.95 mmol/L [21]. There is a good correlation between lactate taken from a lumbar puncture and the sample obtained directly from the ventricle [22].

Current evidence of the usefulness of lactate as a marker of infection in children with a VPS is scarce. Our objective is to provide evidence of the usefulness of lactate as a marker of ventricular infection following VPS.