Acute stroke protocols

IMPLEMENTATION OF AN ACUTE STROKE TEAM AND ACUTE STROKE PROTOCOLS... 

Table 5.2 Sample acute stroke protocol for 64-section multidetector row CT (MDCT) scanner NCCT, vertex-to-arch CTA and biphasic acquisition (one cine image per second for 40 s followed by nine additional cine images obtained at 3-s intervals) CTP...

The technical considerations and interpretation of the second portion of the acute stroke protocol, CTA, is discussed in detail in Chap. 4. Importantly, however, the source images from the CTA vascular acquisition (CTA-SI) also supply clinically relevant data concerning tissue level perfusion. It has been theoretically modeled that the CTA-SI are predominantly blood volume, rather than blood flow weighted [20, 27,70], The potential utihty of the CTA-SI series in the assessment of brain perfusion is discussed in detail below. This perfused blood volume technique requires the assumption of an approximately steady state level of contrast during the period of image acquisition [27], It is for this reason - in order to approach a steady state - that protocols call for a biphasic contrast injection to achieve a better approximation of the steady state [71, 72]. More complex methods of achieving uniform contrast concentration with smaller doses have been proposed that may eventually become standard, such as exponentially decelerated injection rates [73] and biphasic boluses constructed after analysis of test bolus kinetics [72, 74]. 

Obtain Acute Stroke Protocol packet and review responsibilities as outlined on cover Document vital signs Document time patient last seen well... 

These studies raise the possibility that, one day, imaging-based treatment protocols may allow for intravenous thrombolysis in patients well outside of the now-accepted 3-hour window, provided they demonstrate substantial diffusion-perfusion mismatch. Such protocols could allow for treatment of a vastly larger number of patients than are currently treated. It has been estimated that only 1-7% of acute stroke patients currently receive thrombolytic medication, and that, in up to 95% of cases, they are ineligible because they present outside of the 3-hour time window. As many as 80% of patients who present 6 hours after stroke onset may demonstrate a significant diffusion-perfusion mismatch. "... 

Patient care areas Acute stroke teams Written care protocols Emergency medical services Emergency department Stroke unit... 

These results indicate that, provided the appropriate imaging protocol is used, MRI can replace CT as the imaging modality of choice in acute stroke patients, if SAH is excluded. 

Schwab et al. used mild hypothermia (33-34°C) in 20 patients with acute severe middle cerebral artery (MCA) infarction for 48-72 h and found mild hypothermia to be safe and feasible (38). Schwab subsequently reported a series of 25 patients with severe MCA infarction treated with the same protocol (39). Intracranial pressure (ICP) was monitored for 3-7 d, and was found to decrease with initiation of hypothermia. ICP increased during re warming in several patients, but not to the levels seen prior to induction of hypothermia. Pneumonia was seen in 40% of patients treated with hypothermia in this trial, which is within the expected range of occurrence in patients with prolonged ventilation (40). Shimizu et al. used mild hypothermia (33°C) in five patients with embolic infarctions involving the internal carotid artery and MCA territories. The hypothermia was maintained for 3-7 d (41). It was found to be safe, but the number of patients was too small to report any efficacy. Another acute stroke trial using convection air to induce mild hypothermia without anesthesia was found to be feasible (42). Temperatures in this trial were reduced only to 35.5°C, and shivering... 

Schellinger PD, Jansen O, Fiebach JB et al (1999). A standardized MRI stroke protocol comparison with CT in hyperacute intracerebral hemorrhage. Stroke 30 765-768 Schellinger PD, Thomalla G, Fiehler J et al (2007). MRI-based and CT-based thrombolytic therapy in acute stroke within and beyond established time windows an analysis of 1210 patients. 

This chapter will discuss the role of CTA in the diagnosis and triage of acute stroke patients. First, the general principles of helical CT scanning will be reviewed, including image acquisition and reconstruction techniques. The stroke CTA protocol will then be described, followed by specific issues regarding the accuracy and clinical utility of stroke CTA. 

Multislice scanners allow flexibility in designing a rapid and efficient CTA protocol for acute ischemic stroke without causing a significant delay in the institution of thrombolytic therapy. At our institution, the acute ischemic stroke protocol consists of (1) unenhanced head CT, (2) one-pass CTA of the head and neck, and (3) CTP of the head at 1-2 nonoverlapping levels with 4-8 cm of brain coverage (with a 64-slice CT scanner). Of note, using the 64-slice CT scanner, the intracranial and extracranial vasculature from arch to vertex can be imaged in one-pass in less than 15 s. 

Table 4.4 Sample Acute Stroke CTA/CTP Protocol for General Electric 64-slice scanner... 

Smith WS, Roberts HC, Chuang NA et al (2003) Safety and feasibility of a CT protocol for acute stroke combined CT, CT angiography, and CT perfusion imaging in 53 consecutive patients. Am J Neuroradiol 24 688-690. 

Because time is of the essence, it is best if a stroke team that is trained specifically for the triage and treatment of acute stroke patients is formed and appropriate protocols are established. The MGH Acute Stroke Service protocols are listed in Tables 11.1-11.6. They include recommended time targets (Table 11.1) thrombolysis pretreatment phase procedures (Table 11.2) IV-t-PA treatment procedures including inclusion and exclusion criteria (Table 11.3) posttreatment procedures (Table 11.4) details of rt-PA infusion (Table 11.5) and guidelines for blood pressure management in patients receiving this treatment (Table 11.6). 

Page the emergency neuroradiologist as soon as notified of the acute stroke patient and upon patient arrival in the scanner area Execute the standard acute stroke CT/CTA protocols in collaboration with the neuroradiologist and AST... 

MGH Protocols for Endovascular Therapy (Pharmacological and/or Mechanical) in Acute Stroke... 

Although ongoing trials may modify the following treatment algorithm, a possible role of combined PI and DWI as part of a multimodal MRI protocol in the near future for the selection of acute ischaemic stroke patient for thrombolysis is presented below. Indeed, many centres do use stroke MRI to select patients for thrombolysis beyond 3 h (Schellinger et al. 2003). At present, as the evidence is not conclusive, we prefer to randomise post-3-h patients to thrombolytic trials. 

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