gms | German Medical Science

Objective: The intraperitoneal pressure (IPP) is beside the intracranial pressure (ICP) essential for ventriculoperitoneal shunting, which depends on the differential pressure between the intracranial and the intraperitoneal cavity. The determination of the IPP can be therefore decisive for the choice of valve type and pressure setting.

Method: We utilized 6 female pigs (German landrace; mean body weight 59.5 ± 18.4 kg) for experiments. 2 custom made telemetric pressure probes (Fa. Raumedic, Germany) were implanted intraperitoneally in the midline with a distance of 30 cm. Results were referenced with conventional non-invasive pressure measurements (intra-vesical and intra-gastral). IPP was measured on following 3 test days under defined body positions, starting in supine position at 0° and increasing to 30°, 60° and 90° vertical body position. Radiographic control (CT) was performed post mortem in order to measure distance between probes and their placement intraperitoneal.

Results: Reproducible results for all positions were obtained. The epigastrally placed telemetric probe revealed for the supine position 0° 6.7 (± 1.8) H₂O, 6.7 (± 2.3) H₂O at 30°, 5.3 (± 1.9) H₂O for 60° and in vertical body position with 90° 3.8 (± 1.9) H₂O as the local IPP. The probe placed in the lower abdomen showed at 0° supine position 12.2 (± 2.2) H₂O, at 30° elevation 18.2 (± 2.3) H₂O, 24.1 (± 2.3) H₂O at 60° and 29.4 (± 2.6) H₂O as the local IPP. Estimated distance between probes in vertical direction (“epigastrally implanted” over “lower abdomen implanted”) was 3, 11, 18 an 21 cm for 0°, 30°, 60° and 90° position after radiographic control. Mean difference between the pressure difference of both probes in cm H₂O and the vertical distance of implantation site in cm was 2.1.

Conclusions: The IPP is able to reduce the differential pressure in ventriculoperitoneal shunted patients significantly. The IPP depends largely on the intraperitoneal acting hydrostatic pressure. Our data support the choice of (I) a low valve opening pressure for the horizontal body position and (II) adjustable gravitational units for an individualized regulation for the vertical body position in ventriculoperitoneal shunted patients.