Near-occlusion

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... 

Fox AJ, Eliasziw M, Rothwell PMC et al. (2005). Identification prognosis and management of patients with carotid artery near occlusion. American Journal of Neuroradiology 26 2086-2094... 

Fig. 27.1. Selective arterial angiograms of both carotid circulations in a patient with a recently symptomatic carotid "near occlusion" (lower left), and a mild stenosis at the contralateral carotid bifurcation (lower right).

Fig. 27.3. The effect of endarterectomy on the five-year risks of each of the main trial outcomes in patients with varying degrees of stenosis (< 30%, 30-49%, > 70% without near occlusion, and near occlusion) in an analysis of pooled data from the three main randomized trials of endarterectomy versus medical treatment for recently symptomatic carotid stenosis (Rothwell et al. 2003b).

Near occlusions (Fig. 27.1) as a group were identified in the NASCET because it is not possible to measure the degree of stenosis using the NASCET method in situations where the post-stenotic internal carotid artery is narrowed or collapsed as a result of markedly... 

TIA, transient ischemic attack Ml, myocardial infarction PVD, peripheral vascular disease Cl, confidence interval. Hazard ratios derived from the model are used for the scoring system. The score for the 5-year risk of stroke is the product of the individual scores for each of the risk factors present. The score is converted into a risk using Fig. 27.6. °ln cases of near occlusion, enter degree of stenosis as 85%. 

Morgenstern LB, Fox AJ, Sharpe BL et al. for the North American Symptomatic Carotid Endarterectomy Trial (NASCET) Group (1997). The risks and benefits of carotid endarterectomy in patients with near occlusion of the carotid artery. Neurology 48 911-915... 

Chen CJ, Lee TH, Hsu HL et al (2004) Multi-Slice CT angiography in diagnosing total versus near occlusions of the internal carotid artery comparison with catheter angiography. Stroke 35 83-85. 

Bartlett ES, Walters TD, Symons SP, Fox AJ (2006) Diagnosing carotid stenosis near-occlusion by using CT angiography. Am J Neuroradiol 27 632-637. 

D Phase contrast (2D PC MRA) Can show direction and magnitude of flow No artifact from T1 hypeiintense lesions Can show very slowly moving blood. Can be obtained after contrast Can be repeated if suboptimal Low spatial resolution More susceptible to turbulent dephasing than TOF MRA Can have abasing artifact 2D PC of neck is longer than 2D TOF of neck Can determine collateral flow around COW Can detect subclavian steal and abnormal flow direction in neck Can detect slow flow if near-occlusion is suspected... 

TOE MRA combined, to identify ICA occlusion and sensitivity of 99% and specificity of 100% for CE MRA to identify ICA occlnsion [49]. Other stndies, however, do not report such high accuracies [50], and CTA is generally used more frequently than MRA because of demonstrated greater accnracy, availability, and efficiency of scanning. Additionally, most practices still use DSA to definitively differentiate occlusion from near-occlusion. 

William Eugene Parham, Treasurer and member of the Board of Directors and of the Advisory Board of Organic Syntheses, died May 21, 1976 of a coronary occlusion near his summer home on Deer Lake, near Deer River, Minnesota, at the age of 53. Dr. Parham joined the Board of Editors on September 7, 1958 and served as Editor-in-Chief of Volume 44 of Organic Syntheses in 1964. He became a member of the Advisory Board and was elected to the Board of Directors in 1966, and served as Vice President from 1969 to 1974, at. which time he succeeded Richard S. Schreiber as Treasurer. As Treasurer, Dr. Parham was very effective in securing competent legal counsel for Organic Syntheses and in clarifying its foundation tax status with the Internal Revenue Service. 

Since the extent of radical occlusion varies from one precipitation polymerization to the next, it is nearly impossible to develop a generalized polymerization rate equation. As a result, rate expressions are most often determined from experi-... 

In another study of 19 patients with complete or near-complete (TIMI grade 0 or 1) middle cerebral artery (MCA) occlusion, combination therapy with reduced-dose rt-PA and tirofiban infusion was associated with recanalization in 68% of patients, significant reductions of MRI ischemic lesion volumes, and substantial clinical improvement (median NIHSS change from 17 at baseline to 2 after treatment, p = 0.002). No cases of sICH occurred. 

One eritical factor that has been neglected in considering mechanisms of cardiac fatalities is the timeframe for various types of toxicities. For example, a majority of cocaine-related fatalities and near fatalities reported from emergency rooms are attributed to one or more types of cardiac ischemic or hypertensive episodes (Isner et al. 1986). Thus, these studies may discount the cocaine-induced arrhythmias and conduction defects as important direct causes of fatalities. Yet, if coroner reports are used as data sources (Virmani et al. 1988 Wetli and Wright 1979 Mittleman and Wetli 1984), there are great numbers of deaths in which pulmonary effusion and lack of evidence for coronary occlusion, acute myocardial infarction, or... 

Micro-Thromboses Platelets and leucocytes, like other cells, are known to carry surplus negative charge, and can be electrophoretically deposited at (or around) the anode10 owing to the positive electrode potential. These microthromboses in capillaries in or near the treatment site will result in decreased blood flow and may contribute to a local dystrophy of the tissue. A more pronounced version of this effect can be seen sometimes as electrocoagulation and vascular occlusion (i.e., shut, closed or obstructed vasculature) of the tumor tissue. In other words, ECT cuts off the blood supply to the tumor and causes the tumor cell necrosis. 

Finally, PILC, REY-PILC, and a commercial equilibrium catalyst were evaluated at near constant conversion using a heavier feed, hydrotreated resid. The product yields are shown in Table III. Steam deactivated (D), REY-PILC, produced the same gasoline selectivity, LCO/HCO ratio, and coke yield as calcined PILC. The equilibrium catalyst which represents a more severely deactivated (E) sample had higher gasoline selectivity, lower coke yield, and lower HCO/LCO ratio. The higher coke yield of REY-PILC could be due to occlusion of high molecular weight hydrocarbons in the microstructure of the pillared clay. 

Production rates of melt crystallization of organic materials usually are low enough to warrant the use of scraped surface crystallizers like that of Figure 16.10(a). A major difficulty in the production of crystals is the occlusion of residual liquor on them which cuts the overall purity of the product, especially so because of low temperatures near the eutectic and the consequent high viscosities. Completeness of removal of occluded liquor by centrifugation or filtration often is limited because of the fragility and fineness of the organic crystals. 

Overall rates of polymerization are generally rather insensitive to the presence of diluent. Das, Chatterjee and Palit (50) compared rates at 50 mole percent concentration in a variety of liquids. In the range of their experiments, polymerization rate was nearly independent of the choice of diluent. Bamford, Jenkins and White (22) point out that transfer agents reduce the mean degree of occlusion. Since the termination rate is increased under these conditions, the overall polymerization rate is reduced. The extent of polymer swelling will vary from one liquid to another (32, 130), and this obscures the interpretation to be made from limited data. 

Another very practical and useful method for evaluating skin moisturizers is by the direct measurement of TEWL on human skin.23 Not surprisingly, several studies that incorporate this test method have proven that petrolatum is an excellent moisturizer.24"26 It should be noted that in many studies on TEWL, petrolatum is used as a positive standard when evaluating other cosmetic emollients, since petrolatum is nearly always the most occlusive TEWL barrier material tested. It is often the standard by which other ingredients and formulations are judged. 

Fig. 4.7. Coronal measurements of diffusion, proton density (RHO), T1 and T2 relaxation times 30 min after occlusion of the middle cerebral artery in a rat. Note the clear-cut striatal signal increase in the diffusion-weighted image (DWI) compared to nearly unchanged images of the other MR modalities...

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