Blood flow cutaneous

Minor increases in cutaneous blood flow, skin reddening, and skin thickening... 

Cutaneous blood flow and skin temperature have been shown to be substantially increased (assessed against tolazoline) after application of an ointment containing 10 per cent thymoxamine [240a]. 

The actual value is adjusted to the set point by means of various thermoregulatory mechanisms. Blood vessels supplying the skin penetrate the heat-insulating layer of subcutaneous adipose tissue and therefore permit controlled heat exchange with the environment as a function of vascular caliber and rate of blood flow. Cutaneous blood flow can range from - 0 to 30% of cardiac output, depending on requirements. Heat conduction via the blood from interior sites of production to the body surface provides a controllable mechanism for heat loss. 

Heat dissipation can also be achieved by increased production of sweat, because evaporation of sweat on the skin surface consumes heat (evaporative heat loss). Shivering is a mechanism to generate heat. Autonomic neural regulation of cutaneous blood flow and sweat production permit homeostatic control of body temperature (A). 

When sweating is inhibited due to poisoning with anticholinergics (e.g., atropine), cutaneous blood flow increases. If insufficient heat is dissipated through this route, overheating occurs (hyperthermia). 

The DMSO induced increased blood flow was measured using the moorLDI laser Doppler imager (Moor Instruments Ltd, Devon, UK). The instrument scans a low power laser beam in a raster pattern over the skin. Moving blood in the microvasculature causes a Doppler shift, which is processed to build up a color-coded image of cutaneous blood flow. The mean and standard deviation of the blood perfusion units in a region of interest was calculated. 

FIGURE 37.2 DMSO response of xerotic leg skin, (a) Dose dependent increase of DMSO induced cutaneous blood flow before on untreated skin, (b) After twice daily application of a water-in-oil emulsion for six weeks the response was markedly reduced. DMSO induced blood flow was measured with a laser Doppler imager. Data expressed as blood perfusion units. Statistical significance was determined using the paired r-test ( p >. 05,... 

Bioengineering of the Skin Cutaneous Blood Flow and Erythema... 

Berardesca E, Eisner P, Maibach HI (eds) (1995) Bioengineering of the skin cutaneous blood flow and erythema. CRC Press, Boca Raton... 

A comprehensive study comparing the epidermal histologic thickness and the cutaneous blood flow as assessed by LDV was conducted in nine species (mouse, rat, rabbit, cat, dog, pig, cow, horse, and monkey) at five cutaneous sites (buttocks, abdomen, skin over the humeroscapular joint, skin over the thoracolumbar junction and ear). Blood flow did not correlate to skin thickness across species and body sites but rather were independent variables, suggesting that they must be evaluated separately in pharmacology, dermatology, and toxicology studies. 

Blood. Limited serum protein binding capacity. Greater cutaneous blood flow Potential for greater amount of fi ee toxicant and greater distribution Greater percutaneous absorption... 

Skin Thinner epidermis in preterm infants Greater cutaneous blood flow Increased toxicity from percutaneous absorption of chemical agents... 

EXHIBIT A Anatomical and Physiological Considerations Unique to Children. differences in anatomy. allometric scaling factors (e.g. increased surface area-to-volume ratio) cardiovascular status permeability of the pediatric blood-brain barrier (BBB). dermatologic factors (e.g. increased cutaneous blood flow) (Fluhr et al., 2000 Simonen et al, 1997). increased skin pH (Fluhr et al., 2004 Behrendt and Green, 1958) plasma protein binding volume of distribution (V ) organ size and maturity pharmacokinetic maturity (e.g. metabolic differences) (Fairley and Rasmussen, 1983)... 

The major factors that appear to influence TDD site variation include SC structure, (epi)dermal structure, lipid content and structure, cutaneous blood flow, and skin occlusion. 

Secondary factors such as humidity, temperature, skin maturation, and diurnal rhythms, which alter SC composition, physical structure, and cutaneous blood flow, need to be considered when examining the causes of site-to-site variation in TDB. 

Resulting absorption is enhanced at sites that have greater cutaneous blood flow, and mixing a drug with another substance may improve penetration of the skin... 

Drugs are applied topically primarily for local effects however, this route can be used to administer drugs for systemic action. Few drugs readily penetrate intact skin. The absorption of drugs that do penetrate the skin is proportional to the surface area over which they are applied and to their lipid solubility. Increased cutaneous blood flow also enhances absorption. Systemic toxicity can become evident when highly lipid-soluble substances (e.g. lipid-soluble insecticides) are absorbed through the skin. Controlled-release patches are now commonly used in human medicine for transcutaneous drug administration. 

Alopecia is treated with minoxidil (Rogaine). Minoxidil causes vasodilation, increasing cutaneous blood flow, which stimulates hair follicle growth. Alopecia returns in 4 months after the patient stops taking minoxidil. 

N2. Nyfors, A., and Rothenborg, H. W., Cutaneous blood flow in psoriasis measured by xenon clearance. J. Invest Dermatol. 64, 381-385 (1970). 

Butoxyethanol acetate was used to evaluate a noninvasive human method and an in vitro cytotoxicity method as alternatives to the rabbit skin test for primary irritant effects (Jacobs et al. 1989). The human method included measurements of cutaneous blood flow values (CBFV) by laser Doppler flowmetry before and after patch application on the forearm some experiments used 100% test substances (75 mg/cm ) applied for 48 hours and measured 12 hours later, and other experiments used 10% solutions of test substances (7.5 mg/m ) applied for 3 hours and measured 1, 24, 48, and 72 hours later. Cutaneous blood flow values (CBFV) obtained in the two series of experiments (10% for 3 hours and 100% for 48 hours) resulted in a ranking of 2, which is the minimal mean erythema needed to classify substances as skin irritants. The CBFV in humans correlated very well (r=0.99) with erythema scores obtained on rabbits. 

The primary approach to assess dermal absorption is the in vitro diffusion cell. In thi,s model, skin sections (full thickness, deimatomed to a specific thickness) are placed in a two-chambered diffusion cell in which receptor fluid is placed in a reservoir (static cells) or perfused through a receiving chamber (flow-through cells) to simulate cutaneous blood flow. Chemical may either be dosed under ambient conditions neat or dissolved in a vehicle (Franz and Bronaugh cells) or in water (sLdc-by-side diffusion... 

Montciro-Riviere, N. A., Banks, Y. B., and Bimhaum, L, S. (1991), La,ser Doppler measurements of cutaneous blood flow ageing in mice. Toxicol. Lett. 57,329-338. 

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