How is acute renal failure treated?

Therapeutic measures for oliguria should begin with the introduction of a catheter to identify lower urinary tract obstruction, diagnose reflux, collect urine for analysis, and monitor urine. In the absence of intrarenal obstruction and congenital heart disease as the cause of oliguria, prerenal acute renal failure should be suspected and fluid administration should be started.

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Water stress test

If prerenal acute renal failure in children is suspected, treatment should be initiated as soon as possible, without waiting for laboratory test results. To restore the circulating blood volume, an infusion load of isotonic sodium chloride solution or 5% glucose solution in a volume of 20 ml/kg for 2 hours is recommended. Fluid loading serves both a diagnostic and therapeutic procedure. When hypovolemia is the only cause of the observed oliguria, diuresis usually normalizes within a few hours. If diuresis is absent and hypovolemia persists [central venous pressure (CVP) less than 10-20 cm H2O, arterial hypotension, tachycardia], infusion therapy should be continued with the use of FFP or starch solution in a volume of 20 ml/kg for 2 hours. An increase in diuresis indicates prerenal oliguria. The absence of diuresis upon reaching normovolemia (within 18-24 hours) indicates organic acute renal failure. Infusion therapy without proper control and in an inadequate volume against the background of organic acute renal failure can lead to fluid overload of the body (pulmonary edema, cerebral edema, arterial hypertension, heart failure).

Timely correction of prerenal disorders in acute conditions and adequate surgical tactics in postrenal causes, maintenance of normal homeostasis parameters to complete reparative processes in the kidney are necessary.

Late admission of a patient to hospital (with persistence of oliguria and azotemia for more than 24-48 hours) is more likely to indicate the development of acute renal failure in a child, especially an older child.

Renal replacement therapy

The basis of treatment of patients with organic acute renal failure is renal replacement therapy, including intermittent hemodialysis, hemofiltration, hemodiafiltration, continuous low-flow extracorporeal methods and peritoneal dialysis. The most important factors influencing the choice of the type of dialysis are the indications for dialysis and the general condition of the patient.

An absolute indication for the start of dialysis treatment is organic (renal) renal failure, the clinical sign of which is anuria.

Indications for emergency dialysis

• Anuria for more than 1 day.
• Oliguria complicated by:
  • hyperhydration with pulmonary edema and/or respiratory failure, uncontrolled arterial hypertension;
  • disorders of the central nervous system;
  • heart failure;
  • hyperkalemia more than 7.5 mmol/l;
  • decompensated metabolic acidosis (BE <12 mmol/l);
  • an increase in creatinine of more than 120 μmol/day.
• The need to ensure adequate nutrition in long-term oliguria.

Dialysis is necessary when conservative treatment is unable to correct the indicated disorders.

Therefore, the decision to initiate dialysis depends not so much on criteria such as urea or plasma creatinine, but primarily on the general condition of patients, taking into account the clinical course of acute renal failure. These symptoms not only indicate the need for renal replacement therapy, but to a greater extent serve as a signal to stop intensive infusion therapy and stimulation of diuresis, since its continuation can be life-threatening.

Basic principles of treatment and prevention of acute renal failure

• Identification of children with an increased risk of developing acute renal failure and providing them with adequate fluid intake, cardiovascular and respiratory support, creating an optimal microclimate around the child (temperature comfort and oxygenation).
• Elimination of the causes of reduced renal perfusion - normalization of the BCC, hemodynamics, and in case of congestive heart failure - ultrafiltration.
• In case of a positive fluid load test (i.e. with an increase in diuresis), continuation of measures to compensate for the existing fluid deficit with a decrease in the infusion rate under the control of the central venous pressure.
• When treating premature infants, it is necessary to take into account that the hemodynamic "interests" of the kidneys and brain are opposite. Therapeutic measures aimed at improving renal perfusion (administration of dopamine, rapid increase in BCC, transfusion of colloidal solutions) can lead to rupture of vessels in the area of the germinal matrix and hemorrhage into the cavities of the cerebral ventricles.
• The absence of an increase in urine output after fluid loading in a neonate with normal cardiac output and, therefore, normal renal perfusion indicates the presence of renal parenchymal disease, and therefore hemodialysis is necessary.
• Maintaining fluid balance is the basis of patient treatment in the pre-dialysis period and when it is impossible to perform it. The patient's weight should decrease by 0.5-1% per day (the result of caloric losses, not inadequate infusion therapy).
• When assessing the child's fluid needs, it is necessary to take into account physiological losses, metabolic needs and previous fluid balance. Infusion therapy is strictly controlled to achieve normovolemia, the criteria for which are normalization of CVP, arterial pressure, heart rate, elimination of dry skin and mucous membranes, normalization of tissue turgor and restoration of diuresis. Subsequently, the total fluid intake should be equal to unaccounted for plus measured losses (with urine, stool, through drains, etc.). Unaccounted losses normally make up 1/3 of the calculated fluid requirement; they can be determined based on energy requirements, for example, 30-35 ml per 100 kcal per day. However, patients receiving humidified air through an endotracheal tube or steam inhalations have a reduced need for unaccounted for losses. If the patient has a high temperature or is located under a heater or in an incubator, the unaccounted losses will be significantly greater than the calculated ones.
• In severe conditions, these factors in newborns change rapidly, which requires a dynamic approach to infusion therapy. After the introduction of the basic volume of fluid for 4-8 hours, depending on the nature of the pathology, the effectiveness of treatment is assessed based on diuresis indicators, urine concentration and biochemical parameters of urine and blood, the fluid balance and response to the treatment are assessed, and then the fluid load is calculated for the next 4-8 hours. With the correct appointment of the volume of administered fluid, the plasma sodium level should remain stable (130-145 mmol / l). Rapid weight loss, an increase in plasma sodium indicate inadequate infusion therapy. Weight gain in combination with a decrease in the plasma sodium level indicates an increase in hyperhydration.
• Correction of volume deficit in anuria must be carried out very carefully and with those components whose deficiency is most pronounced (erythrocyte mass in severe anemia - hemoglobin <70 g/l, FFP in DIC syndrome, etc.).
• Due to the hyperkalemia often observed in acute renal failure, it is necessary to remember that the plasma potassium level is not an accurate criterion for the potassium content in the body; interpretation of this indicator is possible only taking into account the patient's acid-base balance. Thus, a plasma potassium concentration of 7.5 mmol/l is less dangerous in metabolic acidosis (e.g., at a pH of 7.15 and a bicarbonate level of 8 mmol/l) than in alkalosis (e.g., at a pH of 7.4 and a bicarbonate level of 25 mmol/l).
• In acute renal failure, hyponatremia and metabolic acidosis may develop. A decrease in the amount of serum sodium below 130 mmol/l is usually the result of excessive sodium loss or increasing hyperhydration, so the introduction of concentrated sodium solutions is not indicated due to the possibility of increasing the intravascular volume, developing arterial hypertension and congestive heart failure. Metabolic acidosis is an inevitable consequence of renal dysfunction due to the retention of hydrogen ions, sulfates, and phosphates. Usually, respiratory mechanisms can compensate for a mild degree of acidosis. If the ability to respiratory compensation is impaired, special treatment of respiratory failure is necessary.
• Heart failure in acute renal failure develops due to overload or toxic myocarditis and causes a significant decrease in cardiac output, so inotropic support is mandatory during dialysis and in the interdialytic period (dopamine, dobutamine, adrenaline hydrochloride). Traditional diuretic administration cannot be used to treat heart failure even with hyperhydration and hypervolemia due to anuria. Cardiac glycosides can be prescribed taking into account the severity of renal dysfunction, but their effectiveness is usually low.
• Arterial hypertension often occurs in acute renal failure, especially against the background of acute glomerulonephritis and hemolytic uremic syndrome. The main drugs for the treatment of arterial hypertension are ACE inhibitors and peripheral vasodilators (hydralazine). If necessary, calcium channel blockers are added to them, and with a predominant increase in diastolic blood pressure (> 100 mm Hg), it is rational to add beta- or a-adrenergic blockers. Usually, a combination of these drugs can reduce blood pressure in the absence of edema. Failure to achieve an effect is an indication for ultrafiltration.

• The development of respiratory failure in children with mixed genesis encephalopathy (moderate and severe) with concomitant hydrocephalic-hypertensive and convulsive syndromes indicates the need for mechanical ventilation.
• Overhydration in children with acute renal failure often leads to interstitial pulmonary edema - "rigid lung" - requiring mechanical ventilation.
• In children with hemolytic uremic syndrome, microthrombosis of small branches of the pulmonary artery can lead to an imbalance in ventilation and perfusion, which requires mechanical ventilation.
• Nutrition of children with acute renal failure is an extremely important problem due to the prevalence of catabolic processes. Adequate caloric intake is necessary to enhance energy metabolism. At the same time, restriction of fluid intake in patients with severe oliguria reduces the intake of calories and nutrients. Intravenous administration of essential amino acids (aminosteril, aminoven, neframin) and glucose leads to a positive nitrogen balance, improved reparation, weight maintenance, decreased urea levels, and amelioration of uremic symptoms in patients with acute renal failure.
• The pharmacokinetics of all drugs eliminated with urine change significantly in the anuric stage of acute renal failure, which determines the need to change the dose and frequency of drug administration. In dialysis treatment, it is also necessary to adjust the dose of those drugs that are able to penetrate the dialyzer membrane.
• Antibacterial treatment for acute renal failure is used with caution, taking into account the nephrotoxicity of most antibiotics. In the case of acute renal failure against the background of septic conditions or bacterial infection, the dose of antibiotics is selected taking into account the clearance of endogenous creatinine depending on the group of the antibacterial drug. These recommendations can only be approximate and the doses should be selected individually, since elimination during hemodialysis or hemofiltration has not been sufficiently studied for all drugs, and in most cases, differences in dialysis technique are not taken into account. Preventive administration of antibiotics is permissible at the beginning of peritoneal dialysis against the background of an intestinal infection.

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Evaluation of the effectiveness of treatment of acute renal failure in children

Effective treatment of acute renal failure is indicated by restoration of diuresis, normalization of levels of nitrogen metabolism products, electrolytes in the blood and acid-base balance, absence or elimination of complications, and improvement of the general condition of patients.

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The most common mistakes and unjustified appointments

• Prescription of furosemide against the background of unfilled circulating blood volume.
• Persistent increase in the dose of furosemide in the absence of effect.
• Purpose of mannitol.
• Intensive and uncontrolled infusion therapy against the background of oliguria.
• Continuation of conservative treatment if there are indications for dialysis.
• The use of ganglionic blockers (azamethonium bromide (pentamine)) for hypotensive purposes.

Prognosis for acute renal failure in children

The outcome of acute renal failure depends on many factors. The nature of the underlying disease is of great importance. Mortality in acute renal failure is higher in children who have undergone heart surgery, with sepsis, multiple organ failure, and with late onset of treatment (reaches 50%).

High mortality in neonates with congenital heart failure or with urinary system developmental anomalies, low - in children with reversible conditions such as hypoxia or shock. Among surviving neonates with acute renal failure, more than 40% have reduced SCF and tubular dysfunction. In urological anomalies, the frequency of residual renal dysfunction increases to 80%.

Morphologists have shown that after acute renal failure, complete structural restoration of the kidney does not occur and foci of sclerotic changes are always present. The prognosis for non-oliguric acute renal failure is usually better than for acute renal failure with oliguria: complete restoration of renal function occurs in more than half of patients, while the rest develop interstitial nephritis. Non-oliguric acute renal failure apparently reflects moderate renal damage. Timely treatment with dialysis significantly improves the prognosis and reduces mortality.