Review of Constant Infusion Method of Cerebrospinal Fluid Outflow Resistance Study

Park, Youn Kwan; Oh, Woo Suk; Chong, Yong Gu; Chung, Heung Seob; Suh, Jung Keun; Lee, Hoon Kap; Chu, Jeong Wha; Lee, Ki Chan

Abstract

The author has performed the experimental study to define the validity of the constant infusion technique used in determining the outflow resistance(Ro) of cerebrospinal fluid(CSF). The reduced formula of the constant infusion technique in clinical setting assume that the initial resing Ro and the post-infusion equilibrium Ro are equal, which means that the Ro value is constant regardless of CSF pressure or infusion rate. Although this assumption allows such measurement to be simply and readily applicable in clinical situation, these two Ro values are practically different. So the effect such assumption on calculated Ro data has been investigated. Using 2 different methods Ro was measured simultaneously on each of 20 adult cats;one method was clinically using reduced formula(RoFc) and the other derived from the data of CSF formation rate which was calculated by modified Masserman's method(RoFm). Constant infusion was performed with varying state of infusion(0.01 to 0.2 m/min). Mean values of resting CSF pressure and superior sagittal sinus pressure were 8.8+/-2.9 mmHg and 5.7+/-1.2 mmHg respectively. Mean calculated rate of CSF formation of integrative modifiying Massereman method was 0.0183+/-0.003 ml/min. The maximum Ro was achieved between the rate of infusion of 0.02 and 0.03 ml/min achieved between the range of CSF pressure of 14 and 18 mmHg. Either in level of low CSF pressure or in rate of low infusion, RoFc showed remarkable higher values than RoFm. But this difference did not distinguished in the higher range of CSF pressure or infusion rate. The minmum and maxmum value of RoFc differed the more and RoFm, the less. These findings suggest that in order to obtain more accurate Ro data with constant infusion technique, it must be corrected in low range of CSF pressure or the rate of infusion should be increased several times as that of CSF formation at the risk of possibility of induction of a pressure wave.