Relative stroke

Isoflurane is a respiratory depressant (71). At concentrations which are associated with surgical levels of anesthesia, there is Htde or no depression of myocardial function. In experimental animals, isoflurane is the safest of the oral clinical agents (72). Cardiac output is maintained despite a decrease in stroke volume. This is usually because of an increase in heart rate. The decrease in blood pressure can be used to produce "deHberate hypotension" necessary for some intracranial procedures (73). This agent produces less sensitization of the human heart to epinephrine relative to the other inhaled anesthetics. Isoflurane potentiates the action of neuromuscular blockers and when used alone can produce sufficient muscle relaxation (74). Of all the inhaled agents currently in use, isoflurane is metabolized to the least extent (75). Unlike halothane, isoflurane does not appear to produce Hver injury and unlike methoxyflurane, isoflurane is not associated with renal toxicity. 

The relative reactivity of thermosetting powders can be easily deterrnined by the gel time or stroke-cure test. A small amount of powder is placed on a hot plate, usually at 200°C, and the time until the coating composition gels, or no longer forms fibers, is deterrnined. Powders are characterized by relative gel times (cure rate) as shown in Figure 1. 

Category Systolic [mm Hg] I Diastolic [mm Hg] Stroke mortality relative risk... 

At the other extreme are those acute stroke patients who have no visible arterial occlusion whatsoever, presumably because their infarcts were due to lesions in small arteries that cannot be imaged, or because an embolus in a large proximal artery has broken up spontaneously. Several smdies (again using catheter angiography rather than CTA) have shown that such patients generally enjoy relatively favorable outcomes. 

CTP is a relatively recent development in acute stroke imaging that is already in routine clinical use in many centers. CTP and MRP are similar in that both techniques are based on rapid serial image acquisition during intravenous injection of a bolus of contrast material. In both techniques, measurements of density over time (for CTP) or signal intensity over time (for MRP) are converted to contrast agent-versus-time curves, and these are processed in similar ways to yield the same perfusion measurements (most often CBV, CBF, and MTT). Example CTP images are shown in Figure 2.12. 

Sodium imaging is relatively time consuming and cannot be performed on standard clinical scanners without specialized hardware and software upgrades. Nevertheless, the unique physiologic information provided by sodium imaging may make this technique an important tool in acute stroke imaging in years to come. 

Sorensen AG, Copen WA, 0stergaard L, Buonanno FS, Gonzalez RG, Rordorf G, Rosen BR, Schwamm LH, Weisskoff RM, Koroshetz WJ. Hyperacute stroke simultaneous measurement of relative cerebral blood volume, relative cerebral blood flow, and mean tissue transit time. Radiology 1999 210 519-527. 

Parsons MW, Yang Q, Barber PA, Darby DG, Desmond PM, Gerraty RP, Tress BM, Davis SM. Perfusion magnetic resonance imaging maps in hyperacute stroke relative cerebral blood flow most accurately identifies tissue destined to infarct. Stroke 2001 32 1581-1587. 

The primary outcome of NINDS part I was early clinical improvement by 24 hours, dehned as complete resolution of the stroke symptoms or an improvement in the National Instimte of Health Stroke Scale (NIHSS) score by 4 or more points. There was no difference in early clinical improvement in the rt-PA group compared to the placebo group (relative risk 1.2, 95% Cl 0.9-1.6, p = 0.21). 

INR > 1.7 (PT > 15 if no INR available) with or without chronic oral anticoagulant use Seizure at onset of stroke (This relative contraindication is intended to prevent treatment of patients with a deficit due to postictal Todd s paralysis or with seizure due to some other CNS lesion that precludes thrombolytic therapy. If rapid diagnosis of vascular occlusion can be made, treatment may be given.)... 

The efficacy of IV thrombolysis in patients with moderate-to-severe strokes due to proximal arterial occlusions is restricted by several factors, including the relatively short therapeutic window, poor recanalization rates as the clot burden increases, restrictive eligibility criteria, and the risk of intracerebral hemorrhage. Endovascular techniques improve the rates of recanalization in this patient population, and appear to increase the likelihood of a good functional outcome. Intravenous thrombolysis... 

While early CEA is considered to be relatively safe, it may not always be necessary. For instance, early surgery can be deferred in patients who are medically unstable or for those whose cardiac or respiratory status requires optimization. In the NASCET study, the rate of ipsUateral stroke at 1 month for medically treated patients with high-grade stenoses was only 3.3% and was even lower (1.7%) in patients with near-occlusions. Even in patients with free-floating intraluminal thrombus, anticoagulant therapy is a well tolerated and reasonable first step, given... 

Relatively few data exist concerning the relative benefits of UFH, LMWH, and heparinoids in acute stroke treatment. In 2005, the Cochrane Collaboration reviewed trials comparing LMWHs or heparinoids with UFH in acute ischemic... 

The Safety of Tirofiban in Acute Ischemic Stroke (SaTIS) trial examined 250 patients 6-22 hours after stroke onset treated with tirohban infusion or placebo for 48 hours. No increase in ICH was reported in the active group. Although no beneht in early functional recovery was observed, 5-6-month mortality was lower in the tirohban-treated group (relative risk reduction (RRR) 27%, 95% Cl 0.08-0.95, p = 0.03). 

Acute Aspirin Therapy for AF-associated Stroke A combined analysis of the 1ST and CAST trials indicated a 21% RRR (95% Cl —5 to 41) in the frequency of early recurrent stroke associated with acute aspirin therapy compared to placebo in patients with AF. No difference in early mortality or sICH was found. This finding was largely driven by the relatively large (about 25% RRR) benefit observed in the unblinded 1ST, compared to the smaller benefit (5% RRR) observed in the double-blinded CAST. 

Acute Anticoagulation for AF-associated Stroke HAEST and 1ST provided valuable data on relatively large numbers (449 in HAEST, 3169 in 1ST) of patients with AF-associated ischemic stroke treated with acute anticoagulation (danaparoid in HAEST, UFH in 1ST). HAEST found no reduction in early stroke recurrence or effect on late functional outcome in the LMWH arm. In contrast, 1ST found a dose-dependent reduction in early recurrence rates, but no late functional benefit associated with UFH. However, this was offset by an increase in rates of sICH among patients with AF receiving UFH, with no net benefit in the composite outcome of recurrence stroke and sICH combined. The reasons for the discrepancy between trials is unclear. 

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