4.4 Endovascular Thrombectomy & Post-Procedure Management

Endovascular Mechanical Thrombectomy

Intravenous thrombolysis, while effective for smaller clots, has a notoriously low recanalization rate for large, proximal clots. The paradigm of acute stroke care was revolutionized by the advent of Endovascular Mechanical Thrombectomy (EVT). This minimally invasive interventional procedure is now the absolute standard of care for patients suffering an acute ischemic stroke caused by a Large Vessel Occlusion (LVO)—most commonly defined as an occlusion of the Internal Carotid Artery (ICA) or the proximal (M1) segment of the Middle Cerebral Artery (MCA).

During EVT, a neuro-interventionalist accesses the arterial system (usually via the common femoral artery in the groin or the radial artery in the wrist) and navigates a microcatheter under fluoroscopic guidance up into the cerebral vasculature. The clot is then physically extracted using sophisticated devices, primarily stent retrievers (which deploy a wire mesh to enmesh and pull the clot out) or direct aspiration catheters (which use powerful suction to vacuum the clot out of the vessel), or frequently a combination of both techniques.

Extended Treatment Windows: DAWN and DEFUSE 3

Historically, the window for mechanical thrombectomy was limited to 6 hours from the Last Known Well (LKW). However, the landmark DAWN and DEFUSE 3 clinical trials conclusively demonstrated that highly selected patients could benefit from EVT up to 24 hours after their LKW.

This revolutionary paradigm shift moved the field from a strict "time-based" window to a "tissue-based" window. Eligibility for the extended 6-24 hour window is determined by advanced neuroimaging—specifically CT Perfusion (CTP) or MRI Perfusion. These scans utilize software to precisely calculate the mismatch volume: the ratio of the irreversibly damaged ischemic core compared to the critically hypoperfused but salvageable ischemic penumbra. If a patient has a very small core but a massively large penumbra (a "clinical-core mismatch"), they are a candidate for thrombectomy up to 24 hours out.

Post-Procedure Nursing Management

The post-operative care of the EVT patient requires the highest level of vigilance in a Neuro Intensive Care Unit (Neuro ICU). The patient is at extreme risk for complications related to both the brain (hemorrhage) and the arterial access site.

1. Hemodynamic and Neurological Monitoring

Just as with IV thrombolytics, strict blood pressure control is paramount. If the vessel was successfully opened (recanalized), the previously ischemic tissue is suddenly subjected to normal arterial pressures, placing it at massive risk for hemorrhage.

• BP Parameters: If the patient received IV tPA prior to thrombectomy, the BP must remain < 180/105 mmHg. If they did not receive tPA, the physician will order highly individualized, specific parameters depending on the degree of successful recanalization (TICI score). Often, BP is kept < 140 or < 160 systolic to prevent reperfusion injury.
• Neuro Checks: The frequency exactly mirrors the tPA protocol: Every 15 minutes for 2 hours, then every 30 minutes for 6 hours, then hourly up to 24 hours. The nurse must aggressively monitor the NIHSS for any sign of decline.

2. Access Site and Pulse Monitoring

The arterial puncture site (femoral or radial) must be guarded obsessively. Arterial bleeding can be catastrophic and rapidly fatal.

• Site Checks: The puncture site and the distal limb must be assessed at the exact same frequency as the neurological checks (Q15min x 2h, etc.).
• Assess For: The nurse is inspecting and palpating for expanding hematomas, active external bleeding, or a pseudoaneurysm.
• Distal Pulses: The pulse distal to the puncture (e.g., dorsalis pedis and posterior tibial for femoral access; radial and ulnar for radial access) must be palpated and graded (or assessed via Doppler). Loss of a pulse, pallor, or a cold extremity indicates a limb-threatening arterial occlusion or vasospasm.
• Positioning: For femoral access, the affected leg must remain strictly straight and immobilized for a prescribed period (typically 2 to 6 hours, depending on the closure device used) to prevent the arteriotomy from tearing open.

3. Retroperitoneal Hemorrhage

When the femoral artery is accessed, an insidious and deadly complication is a retroperitoneal hemorrhage. This occurs when the artery bleeds internally, backward into the vast retroperitoneal space of the abdomen.

• Signs and Symptoms: Because the blood is pooling internally, the groin site itself may look perfectly normal. The nurse must look for profound hypotension, sudden unexplained tachycardia, severe ipsilateral flank pain, lower back pain, or pain radiating into the groin.
• Action: This is a life-threatening medical emergency. The nurse must notify the physician stat, prepare for aggressive fluid and blood product resuscitation, and anticipate emergent surgical or interventional repair.

4. Cerebral Hyperperfusion Syndrome (CHS)

CHS is a rare but highly dangerous complication that occurs when normal arterial pressure is suddenly restored to a chronically ischemic vascular bed that has lost its normal autoregulatory capacity (the arterioles are maximally dilated and cannot constrict to handle the sudden pressure).

• Signs and Symptoms: It manifests as a severe, unilateral headache, focal neurological deficits, and frequently, violent seizures, which can rapidly culminate in massive intracerebral hemorrhage.
• Prevention: The absolute best prevention is meticulous, rigid adherence to the physician's prescribed systolic blood pressure limits post-thrombectomy.