Cerebrospinal fluid outflow and intracranial pressure in hydrocephalic patients with external ventricular drainage

Klein O, Demoulin B, Jean Auque RT, Audibert G, Sainte-Rose C, Marchal J-C, Marchal F. Cerebrospinal fluid outflow and intracranial pressure in hydrocephalic patients with external ventricular drainage. Acta Neurol Scand: DOI: 2010: 122: 140–147. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Background and purpose –  The aim of this study was to monitor the 24 h cerebrospinal fluid (CSF) outflow and intracranial pressure (ICP) in hydrocephalic adult patients with external ventricular drainage (EVD). Patients and methods –  Twelve patients (5M/7F) aged 30–69 years suffering from acute hydrocephalus requiring EVD were admitted in the neuro-intensive care unit. The CSF collecting bag was continuously weighted using a high-precision scale, the filtered output of which was fed at 1 Hz to a computer and converted to flow (Q′extcsf). ICP was also recorded. Results –  One patient was excluded because more than 80% of the Q′extcsf data were rejected by the system. The mean ± SD Q′extcsf and ICP were respectively 7.5 ± 3.4 ml/h (range 1.6–12.1 ml/h) and 12.4 ± 2.7 mmHg. Two patterns of Q′extcsf were identified: a continuous profile and a discontinuous one with numerous bursts frequently associated with manoeuvres such as cough or chest physiotherapy. The short-term variations of Q′extcsf and ICP were usually unrelated. Conclusion –  The study stresses the important inter and intra-subject variability of Q′extcsf in patients with EVD. The mean Q′extcsf is lower than the reference production rate (21 ml/h), raising the question of persistent CSF absorption and/or depressed secretion. The independent changes of Q′extcsf and ICP on the short term is likely to be explained by the pressure–volume characteristics of the intracranial space.