Venous tissues

It should be noted that these ranges might be wider if the number of individual animals were larger. It is interesting that venous tissue showed no ATPase activity. It may be pointed out that for the purpose of studying variability, dogs which are available for laboratory study are more suitable than inbred rats because, like humans, they usually have a mixed ancestry. 

The main constituents of normal human venous tissue are listed in Table B6.10. 

Table B6.10 Composition of Normal Human Venous Tissue ...

B6.4.2 Changes with age in composition of normal venous tissues... 

The tensile properties of human venous tissues are presented in Table B6.20. For the testing method and definitions of the terms in the table, please refer to Section B6.5 on Mechanical properties of arteries. 

Phlebitis is an infection of a blood vessel. Infusion-related phlebitis is characterised by pain, tenderness, erythema, induration, oedema and a local temperature increase. These circumstances may lead to thrombus formation or venous tissue destruction or both. 

There are a number of tissue adhesives currently approved as adjuncts to hemostasis. Each agent has specific properties which enhance intraoperative hemostasis in particular situations. All forms of surgical bleeding are not alike. Bleeding can be fast or slow, diffuse or punctate, arterial or venous, capillary or larger vessel. Thus one agent may be more efficacious than another in a specific clinical situation. 

Vasodilators are a group of dtugs, which relax the smooth muscle cells of the blood vessels and lead to an increased local tissue blood flow, a reduced arterial pressure and a reduced central venous pressure. Vasodilators reduce the cardiac pre-load as well as after-load and thereby reduce cardiac work. They are used in a variety of conditions including hypertension, cardiac failure and treatment/prevention of angina pectoris. Major groups are Ca2+-channel blockers (e.g. dihydropyridines), NO-donators (e.g. organic nitrates), K+-channel openers (minoxidil), phosphodiesterase inhibitors (e.g. sildenafil), Rho-kinase inhibitors (e.g. Y27632) or substances with unknown mechanism of action (e.g. hydralazine). Inhibitors of the... 

Ethanol distributes rapidly, with concentrations in body water 10 times higher than in body fat. The tissues with the greatest blood supply equdibrate most rapidly with arterial blood circulation. Shortly after alcohol ingestion, the ethanol concentration in the brain is higher than the venous concentration. 

The ammonia produced by enteric bacteria and absorbed into portal venous blood and the ammonia produced by tissues are rapidly removed from circulation by the liver and converted to urea. Only traces (10—20 Ig/dL) thus normally are present in peripheral blood. This is essential, since ammonia is toxic to the central nervous system. Should portal blood bypass the liver, systemic blood ammonia levels may rise to toxic levels. This occurs in severely impaired hepatic function or the development of collateral links between the portal and systemic veins in cirrhosis. Symptoms of ammonia intoxication include tremor, slurred speech, blurred vision, coma, and ultimately death. Ammonia may be toxic to the brain in part because it reacts with a-ketoglutarate to form glutamate. The resulting depleted levels of a-ketoglutarate then impair function of the tricarboxylic acid (TCA) cycle in neurons. 

FIGURE 7-4. Coagulation cascade. AT, antithrombin HCII, heparin cofactor II TFPI, tissue factor pathway inhibitor. (Reproduced from Haines ST, Zeolla M, Witt DM. Venous thromboembolism. In ... 

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