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Abstract Background There is recent interest in the role of carotid bifurcation anatomy, geometry and hemodynamic factors in the pathogenesis of carotid artery atherosclerosis. Certain anatomical and geometric configurations at the carotid bifurcation have been linked to disturbed flow. It has been proposed that vascular dimensions are selected to minimize energy required to maintain blood flow, and that this occurs when an exponent of 3 relates the radii of parent and daughter arteries. We evaluate whether the dimensions of bifurcation of the extracranial carotid artery follow this principle of minimum work. Methods This study involved subjects who had computed tomographic angiography (CTA) at our institution between 2006 and 2007. Radii of the common, internal and external carotid arteries were determined. The exponent was determined for individual bifurcations using numerical methods and for the sample using nonlinear regression. Results Mean age for 45 participants was 56.9 ± 16.5 years with 26 males. Prevalence of vascular risk factors was: hypertension-48%, smoking-23%, diabetes-16.7%, hyperlipidemia-51%, ischemic heart disease-18.7%. The value of the exponent ranged from 1.3 to 1.6, depending on estimation methodology. Conclusions The principle of minimum work (defined by an exponent of 3) may not apply at the carotid bifurcation. Additional factors may play a role in the relationship between the radii of the parent and daughter vessels.

BACKGROUND. Modem skin resurfacing began with wire brush surgery. The short-pulse carbon dioxide (CO2) lasers provide an alternative approach for facial rejuvenation. However, the potential for the same complications exist. OBJTCTIVES. To review the more common complications, the reasons for their development, and their possible avoidance. METHODS. After pre-op evaluation and skin conditioning, a protocol for resurfacing was followed with standardized settings on the Ultrapulse CO2 laser. On the glabrous skin 300 mJ of energy and 60 W of power -were used. On the eyelid skin the settings were reduced to 250 ml and 50 W. After three passes with the Computer Pattern Generator (CPG), a semi-occlusive dressing was applied for the first 5 days after surgery. Then, a bland petrolatum ointment was applied for an additional 5 days. Finally, a moisturizer with sunscreen or a bleaching cream was used. RESULTS. It was possible at these energy fluences to avoid excessive collagen denaturation and to facilitate wound healing with occlusive dressing. However, complications still occurred. Examples of these are resented in detail. CONCLUSION. Complications can be minimized with patient education, using optimal laser settings, applying occlusive dressings, and recognizing pending problems early. [ABSTRACT FROM AUTHOR]