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A Mary Jo Kocan, RN, MSN, CNRN, CCRN, replies:
Ventriculostomy catheters are frequently used to monitor intracranial pressure (ICP) in patients with head injury, ruptured aneurysm, or hydrocephalus. Because the catheter is placed in one of the cerebral ventricles, cerebrospinal fluid (CSF) can also be drained as a method to control ICP. Debris such as tissue fragments or blood clots can obstruct the catheter and compromise the ability to accurately monitor ICP or to reliably drain CSF. Irrigation is a method used to restore patency of the ventriculostomy catheter. The major risks associated with irrigation are potentially increasing ICP and increased incidence of infection.
The Monroe-Kellie hypothesis states that because the skull is a rigid compartment, once compensatory mechanisms are exhausted, an increase in the volume of one of the intracranial components (brain, blood, CSF) must be accompanied by a reciprocal decrease in another component or pressure will rise.1 Intracranial compliance is a term used to describe the relationship between changes in intracranial volume and pressure. When compliance is low, even small increases in intracranial volume can result in large increases in ICP.1 Depending on where an individual patient falls on this volume/pressure curve, ICP may increase markedly with even a small volume of fluid injected through the ventriculostomy catheter. Patients with poor compliance are at greater risk for this disproportionate increase in ICP and subsequent secondary brain injury.2 However, if CSF drainage is necessary to control ICP in an already compromised patient, obstruction of the ventriculostomy catheter will also cause increased ICP; therefore, it is important to identify and rapidly correct the malfunction.
Observing the ICP waveform will give information on the patency of the catheter. A normal ICP waveform generally has 3 distinct components, P1, P2, and P3 (Figure 1
).1–3 If the waveform is dampened, that is, these components are not distinctly visible, the patency of the catheter or the drainage and monitoring system may be in question and the pressure values displayed may be inaccurate.3 To troubleshoot a dampened waveform, first examine the drainage tubing distal to the patient for the presence of air bubbles, clots, or tissue. If any are present, flush the tubing away from the patient to remove the debris or change the entire drainage system if necessary. If the waveform remains dampened, you can further assess patency of the catheter by observing for flow of CSF. If the patient’s ICP is higher than the height of the collection chamber, CSF should flow into the collection chamber when open to drainage. If the ICP is lower than the height of the collection chamber, you should be able to observe fluctuation of the CSF meniscus in the drainage tubing corresponding to the patient’s respirations (similar to fluctuations in central venous pressure when obtaining readings with a water manometer). Another way to evaluate the functioning of the ventriculostomy catheter is to observe the response to jugular vein compression. Compression of the jugular vein obstructs venous outflow from the brain and increases intracranial volume and ICP.4 If the ventriculostomy catheter is functioning normally, brief compression of the jugular vein will cause a transient rise in ICP. This maneuver can cause a dramatic rise in ICP in the patient with poor intracranial compliance and must be used with caution. If there is no increase in ICP with jugular vein compression, no drainage of CSF or fluctuation with respirations, and a dampened waveform, the catheter may be occluded and the accuracy of the pressure readings should be questioned.
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).2,3 Patients with poor intracranial compliance and those with P2 elevation are at risk for disproportionately large increases in ICP with any activities that influence intracranial volume, including irrigation.2 This risk must be weighed against the benefits of reestablishing reliable ICP monitoring and enabling CSF drainage to reduce ICP.
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There is little research available on which to base the decision of what level of practitioner should be able to perform ventriculostomy irrigation. Guidelines published by the American Association of Neuroscience Nurses9 state that some factors to consider include state nurse practice acts, institutional policies and procedures, infection control practices, and the ability to maintain and document competency. Any practitioner who performs ventriculostomy irrigation must be familiar with ICP dynamics and the potential adverse outcomes from both a nonfunctioning ventriculostomy and from irrigation of the catheter. Sterile technique must be maintained during the procedure to reduce the risk of infection. Based on ICP physiology, the volume of fluid used for irrigation may be one of the defining factors for who can perform irrigation. Although each individual patient’s response to a specific volume of irrigation fluid will vary on the basis of their unique intracranial dynamics, larger fluid volumes are likely to cause greater increases in ICP; therefore, limiting the volume of fluid used can minimize the ICP increase. In our institution, we have defined that nurses in the neurological intensive care unit may irrigate ventriculostomy catheters after pre-requisite experience and competency demonstration, but may use a maximum of 0.2 mL of isotonic sodium chloride solution. If unable to restore patency with this volume, the physician is notified. We chose to limit this practice to the nurses in the neurological intensive care unit because they are able to maintain competency in the procedure because of the frequency with which they care for patients with ventriculostomies (more than 1000 catheter days in the last fiscal year). The advantage of having the bedside clinician perform this procedure is that it eliminates delays in restoring patency. The nurse caregiver is also the person most familiar with the patients’ response to stimuli that are known to increase ICP, such as noxious stimuli, coughing, and fever, and is best able to predict their response to irrigation and identify those at risk for disproportionate increases in ICP.
References
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