A Clinical Evaluation of the Camino Subdural Screw and Ventricular Monitoring Kits

The aim of this study was to compare readings of intracranial pressure from a ventricular catheter with those obtained from a Camino catheter-tipped transducer. The Camino transducer was evaluated in two ways: firstly, when it was inserted by a subdural screw, and secondly, when it was inserted into a ventricular catheter using a ventricular monitoring kit. Data were recorded for 376 hours for the subdural screw method and for 486 hours for the ventricular monitoring kit. Average pressure readings were calculated every 5 minutes (10 half-minute values), and regression analysis was performed. For the subdural screw method, the correlation coefficient was 0.945 (gradient, 1.04; intercept, − 5.51. The results from the ventricular monitoring kit showed that the correlation coefficient was 0.901 (gradient, 0.93; intercept, −0.92. The correlation between recordings of ventricular fluid pressure and the Camino recordings obtained from both subdural screw insertions and ventricular monitoring kits was good, with the subdural screw method proving more accurate and reliable in clinical use.

The Relationship between Ventricular Fluid Pressure and Body Position in Normal Subjects and Subjects with Shunts: A Telemetric Study

Using a chronically implanted telemetric pressure sensor, we have determined the quantitative relationship between changes in body position and ventricular fluid pressure in normal subjects and subjects with shunts. The method allows accurate, reliable measurement of negative as well as positive pressures. We describe the derangement of postural intraventricular pressure regulation caused by placement of a shunt, as well as the influence of various shunt systems and the antisiphon device on this problem. Ventriculoatrial, ventriculoperitoneal, and ventriculopleural shunts all caused similar severely abnormal postural intracranial pressure relationships. The antisiphon device was generally effective in restoring normal pressures in patients in the upright position. We discuss the implications of our findings for understanding the mechanisms of postural intracranial pressure regulation in patients without hydrocephalus.

Cortical Tissue Pressure Gradients in Early Ischemic Brain Edema

We examined the role of ischemic brain edema, tissue pressure gradients, and regional CBF (rCBF) in adjacent regions of cerebral cortex in cats with middle cerebral artery (MCA) occlusion (MCAO). Tissue pressure, rCBF, and water content were measured from gray matter in the central core and the peripheral margin of the MCA territory over 6 h after MCAO. Ventricular fluid pressure and CSF pressure were recorded. Tissue pressure in the ischemic core, with a flow of ∼5 ml/100 g/min, increased more than that in the periphery where flow was ∼19 ml/100 g/min. Tissue pressure rose progressively to 14.8 ± 1.0 mm Hg in the core over 6 h after MCAO, establishing a significant pressure gradient between that tissue and the lateral ventricle nearby or the subarachnoid space in the middle fossa within the first 3 h. The increase in tissue pressure was linearly related to the amount of edema fluid that developed until the edema reached a severe degree. This study shows that a hydrostatic tissue pressure gradient within ischemic cortex is associated with ischemic brain edema. The magnitude of the gradient that develops is related to the severity of ischemic edema in that tissue.

Intracranial volume-pressure relationship in man

✓ Pressure-volume indices (PVI's) were determined for a heterogeneous group of 40 patients who underwent continuous monitoring of ventricular fluid pressure (VFP). The main purpose was to investigate the relationship between VFP and PVI and to establish the significance of the measured PVI values. Determinations of PVI appear to be useful only when baseline VFP is under 20 mm Hg, maximum VFP is under 30 mm Hg, A-waves are absent, and B-waves do not occur numerously. The authors advocate starting with 1-ml bolus infusions, and then, when the resulting pressure rise exceeds 4 mm Hg, additional bolus infusions can be omitted. Results indicate that 13 ml and 10 ml are the key values for the PVI. A PVI of less than 13 ml indicates the need for either reduction of VFP and improvement of compliance or intensive monitoring of both the VFP and the volume-pressure relationship; if the PVI is below 10 ml, anti-hypertensive treatment is almost always necessary. Values of PVI's between 13 and 18 ml, although pathological, usually have no therapeutic consequences.

Effects of intravenous nitroglycerin on the intracranial pressure and volume pressure response

✓ Ventricular fluid pressure (VFP) and volume-pressure response were measured during nitroglycerin (NTG) infusion in nine patients anesthetized with N2O and fentanyl. The patients' ventilation was controlled, and PaCO2 was kept at 32 ± 4 mm Hg. When an infusion of 0.01% NTG was given intravenously to decrease the mean blood pressure to 95.1%, 84.7%, and 78.2% of control, the VFP increased from control levels of 9.94 ± 2.14 mm Hg to 12.89 ± 2.25, 15.6 ± 2.85, and 14.43 ± 3.45 mm Hg, respectively. The volume-pressure response showed a significant increase when blood pressure decreased to 84.7% and 78.2% of control. These results suggest that intravenous NTG caused an increase in the intracranial pressure and a decrease in the intracranial compliance.