Y. Kajimoto et al., Posture-related changes in the pressure environment of the ventriculoperitoneal shunt system, J NEUROSURG, 93(4), 2000, pp. 614-617
Object. The purpose of this study is to clarify the whole pressure environm
ent of the ventriculoperitoneal (VP) shunt system in patients with successf
ully treated hydrocephalus and to determine which factor of the pressure en
vironment has a preventive effect on overdrainage.
Methods. Thirteen patients with hydrocephalus who had been treated with VP
shunt therapy by using a Codman-Hakim programmable valve without incidence
of overdrainage were examined. The authors evaluated intracranial pressure
(ICP), intraabdominal pressure (IAP), hydrostatic pressure (HP), and the pe
rfusion pressure (PP) of the shunt system with the patients both supine and
sitting.
With patients supine, ICP, LAP, and KP were 4.6 +/- 3 mm Hg, 5.7 +/- 3.3 mm
Hg, and 3.3 +/- 1 mm Hg, respectively. As a result, the PP was only 2.2 +/
- 4.9 mm Hg. When the patients sat up, the IAP increased to 14.7 +/- 4.8 mm
Hg, and ICP decreased to -14.2 +/- 4.5 mm Hg. The increased IAP and decrea
sed ICP offset 67% of the HP (42.9 +/- 3.5 mm Hg), and consequently the PP
(14 +/- 6.3 mm Hg) corresponded to only 33% of HP.
Conclusions. The results observed in patients indicated that IAP as well as
ICP play an important role in VP shunt therapy and that the increased IAP
and the decreased ICP in patients placed in the upright position allow them
to adapt to the siphoning effect and for overdrainage thereby to be avoide
d.