title: Gravitational shunt units may cause under-drainage in bedridden patients.
abstract: OBJECTIVE
  Implantation of a shunt in a hydrocephalic patient still carries a risk of complications such as over-drainage and under-drainage. Gravitational shunt units are especially designed to minimize the problem of over-drainage. Nevertheless, these valves carry a risk of under-drainage. The best choice of valve for a patient is still challenging. The purpose of this survey was to identify in which patients a gravitational shunt valve is liable to lead to under-drainage.
  
  
  METHODS
  Patients with hydrocephalus entered prospectively into a data base were reviewed retrospectively. The patients were treated between January 2006 to the end of Feb 2007 and those experiencing under- or over-drainage were identified.
  
  
  RESULTS
  Thirty-five ventriculo-peritoneal shunt systems were implanted in adult patients. The cause of the hydrocephalus was: normal pressure hydrocephalus in 18 patients, post-haemorrhagic following subarachnoid or intracerebral haemorrhage in 11, associated with a tumour in four and followed a head injury in two patients. Three different valves were used: an adjustable shunt valve with gravitational unit (Pro-GAV 0-20/25 in 21 patients), a gravitational shunt valve with fixed opening pressure (GAV 5/30 in nine patients) and an adjustable differential valve (Hakim medos in five patients). Four patients developed severe, valve-related under-drainage. Each had received a gravitational shunt valve and all were bedridden. In two of these patients it was necessary to change the valve. One patient who had received a differential valve, after regaining mobility developed severe over-drainage with bilateral subdural haematomas. Over-drainage was not seen in long-term bedridden patients with a differential shunt valve.
  
  
  CONCLUSIONS
  If a bedridden patient with a gravitational shunt valve system lies with a slightly elevated head, this leads to activation of the gravitational unit and this may cause under drainage. As a result, we advise not using an anti-siphon devices in a patient who is bedridden for a long period.
authors.affiliation: Department of Neurosurgery, Klinikum Kassel, Kassel, Germany. stefaniekaestner@aol.com
authors.forename: S
authors.initials: S
authors.lastname: Kaestner
authors.forename: T
authors.initials: T
authors.lastname: Kruschat
authors.forename: N
authors.initials: N
authors.lastname: Nitzsche
authors.forename: W
authors.initials: W
authors.lastname: Deinsberger
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015170:Cerebrospinal Fluid Pressure / Q000502:physiology; D005260:Female; D006112:Gravitation; D006801:Humans; D006849:Hydrocephalus / Q000503:physiopathology* / Q000601:surgery*; D006874:Hydrostatic Pressure; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D019095:Point-of-Care Systems; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D011187:Posture / Q000502:physiology; D011446:Prospective Studies; D012189:Retrospective Studies; D013525:Surgical Instruments / Q000009:adverse effects / Q000592:standards; D016896:Treatment Outcome; D017287:Ventriculoperitoneal Shunt / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D055815:Young Adult