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Diuresis () is the excretion of urination, especially when excessive (polyuria). The term collectively denotes the renal physiology processes underpinning increased urine production by the during maintenance of fluid balance.
In healthy people, the drinking of extra water produces mild diuresis to maintain the body water balance. Many people with health issues, such as heart failure and kidney failure, need diuretic medications to help their kidneys deal with the Hypervolemia of edema. These drugs promote water loss via urine production. The of in the blood are closely linked to fluid balance, so any action or problem involving fluid intake or output (such as polydipsia, polyuria, diarrhea, heat exhaustion, starting or changing doses of diuretics, and others) can require management of electrolytes, whether through self-care in mild cases or with help from health professionals in moderate or severe cases.
Substances in the circulation can also increase the amount of circulating fluid by increasing the osmolarity of the blood. This has the effect of pulling water from the interstitial space, making more water available in the blood, and causing the kidney to compensate by removing it as urine. In hypotension, are used often intravenously to increase circulating volume in themselves, but as they exert a certain amount of osmotic pressure, water is therefore also moved, further increasing circulating volume. As blood pressure increases, the kidney removes the excess fluid as urine. Sodium, chloride and potassium are excreted in osmotic diuresis, originating from Diabetes (DM). Osmotic diuresis results in dehydration from polyuria and the classic polydipsia (excessive thirst) associated with DM.
For forced alkaline diuresis, sodium bicarbonate is added to the infusion fluid to make blood and, in turn, urine alkaline. Potassium replacement becomes of utmost importance in this setting because potassium is usually lost in urine. If blood levels of potassium are depleted below normal levels, then hypokalemia occurs, which promotes bicarbonate ion retention and prevents bicarbonate excretion, thus interfering with alkalinization of the urine. Forced alkaline diuresis has been used to increase the excretion of acidic drugs like Salicylic acid and Phenobarbital, and is recommended for rhabdomyolysis.
For forced acid diuresis, Vitamin C (vitamin C) is sometimes used. Ammonium chloride has also been used for forced acid diuresis, but it is a Toxicity compound. Usually, however, this technique only produces a slight increase in the renal clearance of the drug. Forced acid diuresis is rarely done in practice, but can be used to enhance the elimination of cocaine, amphetamine, quinine, quinidine, atropine and strychnine when poisoning by these drugs has occurred.
The kidney's resorptive mechanisms are particularly energetic, using nearly 100% of the O2 supplied. Thus, the kidney is particularly sensitive to reduction in blood supply. This phenomenon occurs because renal flow is restored prior to the normal resorption function of the renal Nephron. As shown by the graph, urine flow recovers rapidly and subsequently overshoots the typical daily output (between 800 mL and 2L in most people). Since the kidney's resorption capacity takes longer to re-establish, there is a minor lag in function that follows recovery of flow. A good reference range for plasma creatinine is between 0.07 - 0.12 mmol/L.
The temperature component is caused by water drawing heat away from the body and causing vasoconstriction of the cutaneous within the body to conserve heat. The body detects an increase in the blood pressure and inhibits the release of vasopressin (also known as antidiuretic hormone (ADH)), causing an increase in the production of urine. The pressure component is caused by the hydrostatic pressure of the water directly increasing blood pressure. Its significance is indicated by the fact that the temperature of the water does not substantially affect the rate of diuresis. Partial immersion of only the limbs does not cause increased urination. Thus, the hand in warm water trick (immersing the hand of a sleeping person in water to make them urinate) has no support from the mechanism of immersion diuresis. On the other hand, sitting up to the neck in a pool for a few hours clearly increases the excretion of water, salts, and urea.
Cold-induced diuresis
Cold-induced diuresis, or cold diuresis, is a phenomenon that occurs in humans after exposure to a hypothermic environment, usually during mild to moderate hypothermia. It is currently thought to be caused by the redirection of blood from the extremities to the core due to peripheral vasoconstriction, which increases the fluid volume in the core. Overall, acute exposure to cold is thought to induce a diuretic response due to an increase mean arterial pressure.
The arterial cells of the kidneys sense the increase in blood pressure and signal the kidneys to excrete superfluous fluid in an attempt to stabilize the pressure. The kidneys increase urine production and fill the bladder; when the bladder fills, the individual may then feel the urge to urinate. This phenomenon usually occurs after mental function has decreased to a level significantly below normal. Cold diuresis has been observed in cases of accidental hypothermia as well as a side effect of therapeutic hypothermia, specifically during the induction phase.
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