Lumbar puncture has been to obtain CSF fluid for analysis and to measure CSF pressure, But, it is often difficult to measure CSF pressure in children. The flow of CSF through a spinal needle is described by the equation Flow = pressure/(needle
constant
× relative vescosity). Thus, the CSF flow rate(drops/30 sec) during lumbar puncture can be used to estimate CSF pressure. The CSF viscosity was approximately the same as the viscosity of 0.9% NaCl(relative viscosity =1.02 at between 20℃and
37℃).
Based on this characterstics, normal saline was used to model CSF flow in vitro. The counting drops of CSF and 26℃ 0.9% NaCl for 30 sec through three spinal needle(22G, 21G, 20G, 3.5 inches) was measured at a given pressure (CmH20). From january
1993
to june 1993, the authers measured CSF pressure in a series of 80 children with CNS disease, leukemia, and other malignancy who admitted at dept. of pediatrics, college of medicine, Chungnam national university hospital, the summary of results
were
as
follows:
1) The needles constants(mean + SD) for the 22-gauge 3.5 inch, 21-gauge 3.5 inch, and 20-gauge 3.5inch spinal needles were 1.534 ±0.066, 0.905±0.038. 0.476±0.013 CmH20/Drop/30 sec, respectively, Above results were simply descrbed by the
equation
P22G ≒1.5 ×D, P21G≒0.9×D, P20G≒0.5×D(P=pressure CmH20, D = drops/30sec, G = gauge).
2) Dripping rate was related linearly to pressure for each size needle.
3) Bacause viscosity is temperature-dependent, flow rate through a spinal needle was increased at a high thmperature.
Bacause the drops can bo counted while fluid is being collected, this method is more convenient tham manometric pressure measurement. Eliminating the use of manometer also simplifies the proceduer, reduces supply cost and time, and may avoid the
problem
of manometric pressure measurement such as pain or air bubbles.
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