Document Detail

Overdrainage and shunt technology. A critical comparison of programmable, hydrostatic and variable-resistance valves and flow-reducing devices.
MedLine Citation:
PMID:  7621479     Owner:  NLM     Status:  MEDLINE    
When vertical body position is simulated, conventional differential pressure valves show an absolutely unphysiological flow, which is 2-170 times the normal liquor production rate. Although this is compensated in part by the resistance of the silicon tubes, which may produce up to 94% of the resistance of the complete shunt system, a negative intracranial pressure (ICP) of up to 30-44 cmH2O is an unavoidable consequence, which can be followed by subdural hematomas, slit ventricles, and other well-known complications. Modern shunt technology offers programmable, hydrostatic, and "flow-controlled" valves and anti-siphon devices; we have tested 13 different designs from 7 manufacturers (56 specimens), using the "Heidelberg Valve Test Inventory" with 16 subtests. "Programmable" valves reduce, but cannot exclude, unphysiological flow rates: even in the highest position and in combination with a standard catheter typical programmable Medos-Hakim valves allow a flow of 93-232 ml/h, Sophy SU-8-valves 86-168 ml/h with 30 cmH2O. The effect of hydrostatic valves (Hakim-Lumbar, Chhabra) can be inactivated by movements of daily life. The weight of the metal balls in most valves was too low for adequate flow reduction. Antisiphon devices are highly dependent on external, i.e. subcutaneous, pressure which has unpredictable influences on shunt function, and clinically is sometimes followed by shunt insufficiency. Two new Orbis-Sigma valves showed relatively physiological flow rates even when the vertical position (30 cmH2O) was simulated. One showed an insufficient flow (5.7 ml/h), and one was primarily obstructed. These have by far the smallest outlet of all valves. Additionally, the ruby pin tends to stick. Therefore, a high susceptibility to obliterations and blockade is unavoidable. Encouraging results obtained in pediatric patients contrast with disappointing experiences in some German and Swedish hospitals, which suggests that our laboratory findings are confirmed by clinical results. The concept of strict flow limitation seems to be inadaequate for adult patients, who need a relatively high flow during (nocturnal) ICP crises. The problem of shunt overdrainage remains unsolved.
A Aschoff; P Kremer; C Benesch; K Fruh; A Klank; S Kunze
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery     Volume:  11     ISSN:  0256-7040     ISO Abbreviation:  Childs Nerv Syst     Publication Date:  1995 Apr 
Date Detail:
Created Date:  1995-08-31     Completed Date:  1995-08-31     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8503227     Medline TA:  Childs Nerv Syst     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  193-202     Citation Subset:  IM    
Neurochirurgische Universitätsklinik, Heidelberg, Germany.
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MeSH Terms
Cerebrospinal Fluid Pressure / physiology*
Cerebrospinal Fluid Shunts / instrumentation*
Equipment Design
Equipment Failure
Intracranial Pressure
Models, Neurological
Posture / physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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