J Neurosurg 49:150-151, 1978
A device for intracranial pressure regulation Technical note
BALLARD D. WRIGHT, M.D., AND BYRON YOUNG, M.D.
Department of Anesthesiology and Division of Neurosurgery, Department of Surgery, University of Kentucky Medical Center, Lexington, Kentucky v" The authors describe a device that monitors and automatically regulates intracranial pressure. KEY WORDS
9 intracranial pressure
HE clinical usefulness of intracranial pressure (ICP) monitoring has spawned a number of innovative devices and techniques. These devices measure ICP by means of sensors or transducers that are either implanted in the skull or connected to an intraventricular catheter. The calibrated output of the sensors is displayed as an electronic waveform on an oscilloscope?-4 These devices are properly referred to as monitors since they have no intrinsic regulating function. We are describing a device (invented by B.D.W.) that enables pressure monitoring as well as providing an efficient and automatic regulation of ICP. Description of the Device
The device is illustrated in Fig. 1.* Plastic flexible tubing conducts the cerebrospinal *The intracranial device is manufactured by Baxter Travenol Laboratory, Inc., Baxter Parkway, Deerfield, Illinois. 150
9 monitoring device
fluid (CSF) through an intraventricular catheter to the lower end of the indicator tube which is mounted within a vented chamber. When the lower end of the indicator tube is positioned vertically at the midpoint of the head, the length of the fluid column is a direct indicator of ventricular fluid pressure. An opening at a selected position in the indicator tube provides a maximum pressure limit by permitting fluid to escape from the indicator tube into the collecting chamber whenever the pressure is great enough for the fluid to reach the opening. The chamber is vented to prevent compression of air within the chamber which could affect the fluid pressure reading. Drainage is into a sterile calibrated chamber for volume measurement. Specimens for laboratory assay can be obtained from the collecting chamber through a stopcock. Two micropore filters provide a sterile barrier against the entry of bacteria. A flexible conduit with a stopcock between the device and patient provides access for injecting medications or attachment to a pressure transducer.
J. Neurosurg. / Volume 49 / July, 1978
A device for intraeranial pressure regulation VENT w/MICROPORE FILTER INDICATOR TUBE DRAINAGE PORE CHAMBER
ir)i il IN
DRAIN w/MICROPORE FILTER FIG. 1. Components of the intracranial pressure regulator. For a description, see text.
demands on already overburdened intensive care personnel, and may result in errors of omission and judgment. The more obvious advantage of this ICP regulator is its combination of monitoring capability with automatic regulation of fluid drainage. Other devices for continuous drainage of CSF do not have a simple device for measuring ICP. We have used this device in 52 patients for over 400 patient days. A wide variety of clinical conditions have been encountered, including stroke, neoplasms, trauma, infection, and hydrocephalus. This device has been particularly useful in hydrocephalic patients with an infected shunt. Our routine procedure has been to remove the shunt, to administer antibiotics while maintaining the intracranial pressure within a normal range with the regulating device, and then to replace the shunt when the infection is eradicated.
Acknowledgments The device is sealed top and bottom by transparent plastic end-caps attached to its barrel to form an enclosed chamber. A fluidtight seal is obtained by application of adhesive.
We are grateful to Dr. Hector James for clinical evaluation of the device, Mr. Michael McLaughlin and Mr. Gregory Gorenflo for technical assistance, and Travenol Laboratories, Inc., for support to develop the device.
References Discussion There are several drawbacks to the electronic techniques for ICP monitoring, among which are the requirement of sufficient and competent technical personnel to assure the validity of measurements, transducer characteristics such as drift and instability, and electrical shock hazards. The major technical problem with devices using intraventricular catheters is that the accuracy of measurements is greatly reduced when marked intracranial hypertension causes collapse of the lateral ventricles. In addition, withdrawal of CSF to decrease ICP increases the tendency for collapse of the ventricles. We are unaware of any reliable method to determine how much and how frequently CSF should be withdrawn in order to optimally reduce ICP without unduly risking ventricular collapse. Furthermore, these timeconsuming decisions and maneuvers make
J. Neurosurg. / Volume 49 / July, 1978
1. Dorsch NWD, Symon L: A practical technique for monitoring extradural pressure. J Neurosurg 42:249-250, 1975 2. Vries JK, Becker DP, Young HF: A subarachnoid screw for monitoring intracranial pressure. Technical note. J Neurosurg 39:416--419, 1973 3. Winn HR, Dacey RG, Jane JA: Intracranial subarachnoid pressure recording: experience with 650 patients. Snrg Neurol 8:41-47, 1977 4. Yoneda S, Matsuda M, Handa J, et ah Continuous measurement of intracranial pressure with SFT: clinical experiences. Surg Neurol 4:289-295, 1975
Address reprint requests to: Byron Young, M.D., Division of Neurosurgery, University of Kentucky Medical Center, 800 Rose Street, Lexington, Kentucky40506.