[Clinical validity of lumbar subarachnoid pressure measurement]

To evaluate the clinical usefulness for measuring lumbar subarachnoid pressure (LSP) as an index of intracranial pressure, the relation between LSP and epidural pressure (EDP) was studied by the cisternal saline infusion and bolus injection in 12 cats at the range of pressure up to 50 mmHg. In the steady state infusion (0.238 ml/min, 0.476 ml/min), the data from LSP and EDP were correlated very well and the LSP value was at least above 80-90% of EDP value at any pressure level. In the bolus injection (0.4 ml), the degree of pressure rise and the time course of both LSP and EDP were quite similar at any pressure level. However, the compliance calculated from the pressure change of LSP and EDP revealed to have a different tendency according to the baseline pressure level at bolus injection. Below 10 mmHg of EDP, the compliance calculated from LSP was usually higher that of EDP. This was considered due to the distensibility of spinal theca. But above 10 mmHg of EDP, the compliance of both LSP and EDP became almost equal and then gradually decreased as the elevation of baseline pressure at bolus injection. This was considered to be the result of disappearance of the distensible effect of spinal theca. In this study, two polyethylene tubes of different size (I. D. 0.45 mm, 0.58 mm) were used for spinal drainage tube to compare the pressure dumping effect of tube. However, on both tubes, the pulse pressure of LSP was usually smaller than that of EDP, with each having almost constant difference.(ABSTRACT TRUNCATED AT 250 WORDS)