19.1.1 Clinical Presentation

An 80-year-old male presents to the emergency department (ED) at 8 a.m. after waking up with a dense left hemiparesis, left-sided facial droop, and a left hemisensory loss. Although moderately drowsy, he is awake and able to follow basic commands. He was last seen normal at 3 a.m. The patient’s National Institutes of Health Stroke Scale (NIHSS) score was 17.

Two days prior to admission, he presented to the ED with left-sided amaurosis fugax. Computed tomography angiography (CTA) at that time demonstrated a new occlusion of the right internal carotid artery (ICA; Fig. 19.1). He was discharged after a 24-hour observation period with a new prescription for Lovenox.

Past medical history is significant for coronary artery disease, congestive heart failure, atrial fibrillation, hypertension, hyperlipidemia, sleep apnea, and a remote history of nonaneurysmal subarachnoid hemorrhage (SAH).

19.1.2 Imaging Workup and Investigations

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  Noncontrast computed tomography (NCCT) of the head demonstrates a hyperdense clot in the right middle cerebral artery (MCA; Fig. 19.2a).

  
  
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  CTA demonstrates an occlusive clot in the right M1 (Fig. 19.2b) as well as recanalization of the right ICA consistent with an artery-to-artery embolus (Fig. 19.2c).

  
  
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  CT perfusion (CTP) demonstrates decreased cerebral blood volume (CBV) isolated to the basal ganglia (Fig. 19.2d) and markedly diminished cerebral blood flow (CBF) in the entirety of the right MCA territory consistent with a small core and large ischemic penumbra (Fig. 19.2e, f).

  

19.1.3 Diagnosis

Acute ischemic stroke secondary to right MCA M1 occlusion.

19.1.4 Treatment

19.2.1 Clinical Presentation

An 84-year-old man presented to the ED 1 hour after developing a left MCA syndrome. His initial NIHSS score was 25.

19.2.2 Imaging Workup and Investigations

Initial advanced stroke imaging demonstrated no evidence of early ischemic change and a left M1 thrombus. The patient was given intravenous (IV) tPA and brought to the angiography lab for mechanical thrombectomy. The procedure was performed with conscious sedation. Initial angiography confirmed the M1 occlusion, but the image was severely motion degraded (Fig. 19.4) due to agitation and inability to follow commands on account of global aphasia. The patient was given more sedation and was held still, while a 5-Max Ace was used to aspirate the clot with TICI 3 reperfusion achieved in 14 minutes. As seen by the completion angiography (Fig. 19.4), with increased sedation it was possible to keep the patient still; however, he was now too drowsy for reassessment during and straight after the procedure.

19.2.3 Outcome

Patient had a NIHSS score of 0 at 24 hours and only a tiny infarct in the left insula.

19.2.4 Case Discussion: Anesthesia Choices in Stroke Intervention

There are a number of challenges in the anesthetic management of patients receiving intra-arterial therapy for acute ischemic stroke. Similar to the patient in the first vignette, stroke patients are generally elderly and suffer from multiple medical comorbidities such as hypertension, coronary artery disease, cardiac arrhythmias, and congestive heart failure. Both the anesthesiologist and neurointerventionalist must consider a number of important factors in deciding how to manage these patients, including choice of anesthetic method (general endotracheal anesthesia versus conscious sedation), ability of the patient to protect his or her airway, ability of the patient to follow commands and stay still, patient volume status and blood pressure management, and intraoperative management of any medical comorbidities such as hyperglycemia or dysrhythmias. Ultimately, decisions regarding the choice of anesthetic agents in patients receiving intra-arterial therapy for acute ischemic stroke should not be taken lightly. ¹

Anesthetic choice for patients receiving endovascular recanalization procedures for treatment of acute ischemic stroke has historically been a topic of great controversy. ^{2 ,​ 3 ,​ 4} Many practitioners view general endotracheal anesthesia as advantageous when compared to conscious sedation due to perceptions that general endotracheal anesthesia eliminates intraoperative movement (seen in the supplementary case performed with conscious sedation), thereby improving procedural safety, intraoperative time, and efficacy. ²

As stroke intervention requires navigation of microcatheters and microguidewires in the cerebrovasculature, using road map images, accurate superimposition of the live fluoroscopic images on the road map image is essential in ensuring that devices are placed in the correct location. Any degree of patient movement following creation of the road map can negatively affect the ability of the neurointerventionalist to properly navigate the microcatheter and microguidewire. In addition, patient movement could limit the ability of the neurointerventionalist to identify X-ray markers of catheters, mechanical devices, and wires. ² In the worst case scenario, this could lead to vessel perforation or dissection (see Chapter 36). It is because of perceptions of increased procedural efficiency, efficacy, and safety that general endotracheal anesthesia remains widely used in the intra-arterial treatment of acute ischemic stroke. ^{5 ,​ 6}

However, recent evidence has emerged to suggest that, in many cases, the use of general endotracheal anesthesia may be associated with poorer clinical outcomes and lower recanalization rates when compared to conscious sedation or local anesthesia. One meta-analysis of nearly 2,000 patients demonstrated that patients receiving general endotracheal anesthesia encountered higher rates of death, respiratory complications, good neurological outcomes, and recanalization. ⁷ Many of the major concerns regarding the risks of conscious sedation (i.e., higher risk of wire perforation or vascular injury, risks of intraprocedural intubation, and decreased procedural efficiency) have not been borne out. To date, there is no conclusive evidence demonstrating higher rates of dissection or wire perforation among patients receiving conscious sedation or local anesthesia. ⁷ Furthermore, there is no conclusive evidence to suggest that there is any difference in procedure length or time to reperfusion among patients receiving general anesthesia or conscious sedation. Finally, while emergent intubation is associated with higher rates of airway trauma, aspiration, and death, the use of this technique among patients receiving conscious sedation for neurointerventional procedures is low. ⁸

Conscious sedation has a number of physiologic advantages when compared to general endotracheal anesthesia. First, dynamic cerebral autoregulation is generally preserved with midazolam which results in decreased volatility in intraprocedural cerebral perfusion. ⁹ Meanwhile, inhaled anesthetic agents, including N₂O and the fluorinated ethers, are associated with a higher risk of cerebral hypoperfusion and are even thought to be neurotoxic. There is evidence to suggest that such general anesthetic agents cause vasodilatation of the nonischemic territories, thus resulting in a steal phenomenon. ^{9 ,​ 10} In addition, significant hemodynamic changes are known to occur during the induction and recovery phases of general anesthesia which can compromise cerebral perfusion pressures. ¹¹ General anesthesia is also associated with higher rates of intraprocedural hypotension which can compromise cerebral perfusion pressures. ¹² Conscious sedation also allows the team to evaluate the patient while awake in order to monitor for any improvement or worsening of the patient’s clinical deficit. In this case, for example, the patient recovered some function when partial recanalization was achieved with the stent retriever, but shortly lost function secondary to reocclusion of the MCA. Finally, general endotracheal anesthesia has been shown to be associated with higher rates of respiratory complications secondary to aspiration and airway trauma. ¹³

There are still a number of unanswered questions regarding anesthesia management in patients receiving endovascular treatment for acute ischemic stroke. First, the exact reasons behind the improved outcomes associated with conscious sedation are unknown. As mentioned above, intraprocedural hypotension (defined by some as SBP < 140 mm Hg) is more likely to occur with general anesthesia than conscious sedation. ¹² Typically, the target blood pressure range for patients with acute ischemic stroke is 20 to 30% above the patient’s baseline pressure. ⁹ However, there is no evidence to date to suggest that there is any benefit in pharmacologically increasing blood pressure in patients who are hemodynamically stable. ^{1 ,​ 9} Managing intraprocedural hypertension is also difficult and typically requires the use of short acting antihypertensives such as sodium nitroprusside or esmolol. Immediate postrecanalization hypertension could result in a higher risk of postprocedure hemorrhage; so, it is important to monitor and manage this in order to avoid this complication. Ideal protocols for fluid management have also yet to be established. In general, patients presenting with acute ischemic stroke are elderly with decreased cardiac reserves, anemic, and often hypovolemic. While hypovolemia is typically thought to be associated with poorer outcomes, aggressive intravenous hydration could result in dramatic lowering of the patient’s hematocrit, thus decreasing cerebral oxygen delivery. ^{1 ,​ 9}

Ultimately, there is a growing consensus based on a growing body of evidence that conscious sedation is the anesthetic method of choice during endovascular management of acute ischemic stroke patients. However, before each procedure, communication between the neurointerventionalist and anesthesia team is essential in order to determine the ideal management strategy for each patient. There are certainly cases where general anesthesia should be considered, especially in cases where there is a high likelihood that the patient will be agitated and unable to keep still, and in cases where the patient will be unable to maintain his or her airway.