Forced diuresis

Forced diuresis as a method of detoxification is based on the use of drugs that promote a sharp increase in diuresis; this is the most common method of conservative treatment of poisoning, in which the elimination of hydrophilic toxicants is carried out primarily by the kidneys.

These purposes are best met by osmotic diuretics (mannitol), the clinical use of which was initiated by the Danish physician Lassen in 1960. An osmotic diuretic is distributed only in the extracellular sector, is not subject to metabolic transformations, is completely filtered through the glomerular basal membrane, and is not reabsorbed in the renal tubular apparatus. Mannitol is a widely used osmotic diuretic. It is distributed only in the extracellular environment, is not metabolized, and is not reabsorbed by the renal tubules. The volume of distribution of mannitol in the body is about 14-16 liters. Mannitol solutions do not irritate the intima of the veins, do not cause necrosis when administered under the skin, and are administered intravenously as a 15-20% solution of 1.0-1.5 g / kg. The daily dose is no more than 180 g.

Furosemide is a strong diuretic (saluretic) agent, the action of which is associated with the inhibition of reabsorption of Na+ and Cl, and to a lesser extent K+ ions. The effectiveness of the diuretic action of the drug, used in a single dose of 100-150 mg, is comparable to the action of osmotic diuretics, but with repeated administration, more significant losses of electrolytes, especially potassium, are possible.

The method of forced diuresis is considered to be a fairly universal method of accelerated removal of various toxic substances from the body, including barbiturates, morphine, organophosphorus insecticides (OPI), quinine and pachycarpine hydroiodide, dichloroethane, heavy metals and other drugs excreted from the body by the kidneys. The effectiveness of diuretic therapy is significantly reduced as a result of the formation of a strong bond between many chemicals that have entered the body and proteins and lipids in the blood, as is noted, for example, in poisoning with phenothiazines, clozapine, etc. In case of poisoning with toxicants that give an acidic reaction in an aqueous solution (barbiturates, salicylates, etc.), the blood is first alkalized by intravenous administration of sodium bicarbonate (4% solution, 500 ml).

Forced diuresis is always performed in three stages: preliminary water loading, rapid administration of a diuretic, and replacement infusion of electrolyte solutions.

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The following forced diuresis technique is recommended:

First, hypovolemia developing in severe poisoning is compensated for by intravenous administration of plasma-substituting solutions. At the same time, the concentration of the toxic substance in the blood and urine, hematocrit are determined, and a permanent urinary catheter is inserted to measure hourly diuresis. Mannitol (15-20% solution) is administered intravenously by jet stream in the amount of 1.0-1.5 g per 1 kg of the patient's body weight for 10-15 minutes, then an electrolyte solution at a rate equal to the diuresis rate. The high diuretic effect (500-800 ml/h) is maintained for 3-4 hours, after which the osmotic balance is restored. If necessary, the entire cycle is repeated, but not more than twice to avoid the development of osmotic nephropathy. The combined use of osmotic diuretics with saluretics (furosemide) provides an additional opportunity to increase the diuretic effect by 1.5 times, however, the high speed and large volume of forced diuresis, reaching 10-20 l/day, pose a potential danger of rapid leaching of plasma electrolytes from the body.

To correct possible disturbances in the salt balance, an electrolyte solution is administered.

The method of forced diuresis is sometimes called blood washing, since the associated water-electrolyte load places increased demands on the cardiovascular system and kidneys. Strict accounting of the introduced and excreted fluid, determination of hematocrit and CVP allow easy control of the body's water balance during treatment, despite the high rate of diuresis.

Complications of the forced diuresis method (hyperhydration, hypokalemia, hypochloremia) are associated only with a violation of the technique of its use. To avoid thrombophlebitis at the site of administration of solutions, catheterization of the central vein is recommended. With prolonged use of osmotic diuretics (over 3 days), osmotic nephrosis and acute renal failure may develop. Therefore, the duration of forced diuresis is usually limited to these periods, and osmotic diuretics are combined with saluretics.

The forced diuresis method is contraindicated in cases of intoxication complicated by acute cardiovascular failure, as well as in cases of renal dysfunction (oliguria, azotemia, increased blood creatinine levels over 221 mmol/l, which is associated with low filtration volume). In patients over 50 years of age, the effectiveness of the forced diuresis method is significantly reduced for the same reason.