title: Laboratory study on "intracranial hypotension" created by pumping the chamber of a hydrocephalus shunt.
abstract: BACKGROUND
  It has been reported that pumping a shunt in situ may precipitate a proximal occlusion, and/or lead to ventricular over-drainage, particularly in the context of small ventricles. In the laboratory we measured the effect of pumping the pre-chamber of hydrocephalus shunts on intracranial hypotension.
  
  
  METHODS
  A simple physical model of the CSF space in a hydrocephalic patient was constructed with appropriate compliance, CSF production and circulation. This was used to test eleven different hydrocephalus shunts. The lowest pressure obtained, the number of pumps needed to reach this pressure, and the maximum pressure change with a single pump, were recorded.
  
  
  RESULTS
  All models were able to produce negative pressures ranging from -11.5 mmHg (Orbis-Sigma valve) to -233.1 mmHg (Sinu-Shunt). The number of pumps required reaching these levels ranged from 21 (PS Medical LP Reservoir) to 315 (Codman Hakim-Programmable). The maximum pressure change per pump ranged from 0.39 mmHg (Orbis-Sigma valve) to 23.1 (PS Medical LP Reservoir).
  
  
  CONCLUSIONS
  Patients, carers and professionals should be warned that 'pumping' a shunt's pre-chamber may cause a large change in intracranial pressure and predispose the patient to ventricular catheter obstruction or other complications.
authors: Academic Neurosurgical Unit, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK. apb49@cam.ac.uk <apb49@cam.ac.uk>
authors: Adam
authors: A
authors: Bromby
authors: Zofia
authors: Z
authors: Czosnyka
authors: David
authors: D
authors: Allin
authors: Hugh K
authors: HK
authors: Richards
authors: John D
authors: JD
authors: Pickard
authors: Marek
authors: M
authors: Czosnyka