Effect of postural changes on ICP in healthy and ill subjects
Morten Andresen, Amer Hadi, Lonnie G. Petersen & Marianne Juhler
This publication reports the effect of body postures on measured ICP. We show that negative ICP values in the upright position are probably normal. Patients with a normal ICP appear able to more tightly regulate ICP when switching body postures. We also show that assuming postures which are used for lumbar puncture increases ICP and warn that this could lead to erroneous measurements. It presents ideas for an “upright-first” approach to managing shunt-patients.
Background
Reference values and physiological measurements of intracranial pressure (ICP) are primarily reported in the supine position, while reports of ICP in the vertical position are surprisingly rare considering that humans maintain the vertical position for the majority of the day. In order to distinguish normal human physiology from disease entities such as idiopathic intracranial hypertension and normal pressure hydrocephalus, we investigated ICP in different body postures in both normal and ill subjects.Methods
Thirty-one patients were included: four normal patients following complete removal of a solitary clearly demarcated small brain tumour and fitted with a telemetric ICP monitoring device for long-term ICP monitoring; 27 patients requiring invasive ICP monitoring as a part of their diagnostic work-up or monitoring of shunt treatment effect. ICP was recorded in the following body positions: upright standing, sitting in a chair, supine and right lateral lumbar puncture position.Results
Linear regression of median ICP based on patient posture, group, and purpose of monitoring presented a significant model (p < 0.001), but could not distinguish between patient groups (p = 0.88). Regression of differences in median ICP between body postures and supine ICP as the baseline, presented a highly significant model (p < 0.001) and adjusted R2 = 0.86. Both body posture (p < 0.001) and patient group (p < 0.001) were highly significant factors.Conclusions
Differences in ICP between body postures enabled us to distinguish the normal group from patient groups. Normal patients appear able to more tightly regulate ICP when switching body postures.Read the full paper in Acta Neurochirurgica (click here).