Effect of Protein Concentration on the Flow of Cerebrospinal Fluid Through Shunt Tubing

Abstract

BACKGROUND: Protein levels in cerebrospinal fluid (CSF) are commonly thought to be related to sterile shunt malfunction. OBJECTIVE: To investigate the relationship between protein concentration and flow through CSF shunt tubing and a shunt valve. METHODS: New and explanted shunt catheters were tested with and without a shunt valve attached at various protein concentrations. The protein concentrations used were 0.5, 2, 5, and 10 g/L. A flask with artificial CSF attached to the proximal end provided flow. The flow was allowed to stabilize over 1 hour, and then the change in pressure between the proximal and distal end of the catheter was measured and recorded. The resistance to flow was calculated for new and explanted catheters for adult shunt systems, as well as with the addition of a programmable siphon control valve. The resistance was examined after the addition of various protein concentrations to a normal CSF solution. RESULTS: Both new and explanted catheters exhibited a decrease in the resistance to flow with higher concentrations of protein. CONCLUSION: In our laboratory setting, there was decreased resistance of adult CSF shunt catheters with and without a valve as the concentration of protein in the CSF increased. The decrease in the resistance of CSF shunt catheters with the addition of protein to the CSF may be related to the lowering of surface tension. This is the first study to examine the effects of varying protein concentrations across different lengths of shunt tubing for both new and explanted catheters.