Catheter Occlusion in External Ventricular Drainage: The “VISTA” Mnemonic

Introduction

External ventricular drains (EVDs) are common in neurocritical care for monitoring and treating intracranial pressure (ICP).[1] Despite their usefulness, occlusion is a well-known and potentially life-threatening complication. Causes of obstruction include intracranial hypotension, coagulated blood, tissue debris, and collapse of the ventricular wall around the catheter ([Table 1]). Early detection and timely intervention are paramount to keeping the catheter useful and avoiding secondary brain injury.

Table 1 Causes of cessation of CSF flow in the EVD

Mechanical

Kink/disconnection  Catheter malposition  Filter occlusion  Hypotension with collapsed ventricles

Cellular debris

Blood  Tissue fragments  Ventriculitis

Diversion

CSF leak away from the site of EVD  Over-drainage  Decompression on the contralateral side

Abbreviations: CSF, cerebrospinal fluid; EVD, external ventricular drain.

Pathophysiology of Catheter Occlusion

Catheter occlusion in EVD can be caused by a wide variety of factors, all basically leading to poor flow of cerebrospinal fluid (CSF) and hence neurological deterioration. Intracranial hypotension, as usual, due to excessive drainage of CSF, could lead the ventricle to collapse and obstruct the proper functioning of the catheter to reduce the drainage effect. The presence of thick or coagulated blood in most cases involving intraventricular hemorrhage promotes clots inside the lumen of the catheter that may obstruct the lumen. Besides, the accumulation of tissue debris, including cellular remnants from infection, inflammation, or surgical manipulation, in the system itself may further impede flow. Another critical factor is the collapse of the ventricular wall, which occurs as a result of over-drainage, leading to compression of the catheter by the surrounding brain structures and blockage of fluid outflow. Understanding these mechanisms is critical for the prompt recognition and effective management of EVD occlusion, minimizing complications, and improving patient outcomes.

The VISTA

The “VISTA” mnemonic provides a systematic approach to identifying catheter occlusion in EVD patients. First, it involves the Visual inspection of the drainage system and fluid collected for abnormalities. This is followed by Initial clinical assessment: Neurological symptoms, such as changes in consciousness, headache, and vomiting, indicative of increased ICP. Signal analysis: The ICP waveform is assessed for dampening or absence, which may indicate blockage. Tomographic imaging: A CT scan confirms catheter displacement, ventricular collapse, or clots. An action plan: This will be an implementation that may involve corrective actions such as repositioning, irrigation, and catheter replacement to reinstate normal drainage and alleviate symptoms. This holistic approach ensures the EVD occlusion is addressed in a timely and efficient manner ([Fig. 1]).

Fig. 1 The VISTA mnemonic. CT, computed tomography; ICP, intracranial pressure.

The management of EVD occlusion utilizes both conservative and interventional techniques. In cases of ventricular collapse, readjustment of the patient's head may restore normal CSF flow. Minor blockages may be flushed out with gentle saline irrigation, ensuring the patency of the catheter. If the occlusion is from small clots, careful aspiration, using sterile techniques, might resolve the issue. If the occlusion still cannot be relieved by noninvasive methods, surgical revision like catheter replacement may become necessary to restore appropriate drainage. Proactive management is required to reduce the occlusion of the EVD. The use of appropriate anticoagulants can prevent the formation of clots in high-risk patients that may occlude the catheter. Regular flushing protocols have been put in place to maintain the drainage system and minimize obstruction. Besides this, strict infection control is in place since it has also been observed that prevention of infection may reduce chances of occlusion by inflammatory debris of the catheter.

Conclusion

In summary, EVD obstruction constitutes a source of great concern for neurosurgical and neurocritical care. The VISTA mnemonic provides a systematic and practical method for the detection and treatment of occlusions that significantly improve outcomes and can further extend the life of the catheter. Ultimately, future research should be performed to establish guidelines for maintaining and troubleshooting EVD systems to optimize care and minimize complications. These developments will bring about better management strategies, adding to the total success of EVD therapy in critical patients.

Conflict of Interest

None declared.

• References

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Publication History

Article published online:
21 April 2025