Peritoneal dialysis

Peritoneal dialysis is a safe and relatively inexpensive method of renal replacement therapy. The first attempt to replace kidney function using this method in a patient with acute kidney failure was performed by Ganter in 1923. The abdominal cavity by nature itself was created as a reserve organ of detoxification. The peritoneum serves as a semipermeable dialysis membrane, the area of which corresponds to the surface area of the patient's body, and the blood flow to the renal blood flow (1200 ml / min). The clearance of low-molecular substances in conditions of peritoneal dialysis is significantly lower than in hemodialysis. Meanwhile, the peritoneal dialysis procedure is constant (round the clock), and therefore the total clearance may be higher than with intermittent hemodialysis.

General characteristics

The process of peritoneal dialysis proceeds according to the same principles as dialysis through an artificial semi-impermeable membrane with the "artificial kidney" apparatus, the peritoneum in this case acts as a natural membrane. At the same time, the anatomical and physiological features of the peritoneum determine a number of fundamental differences in the possibilities of peritoneal dialysis from hemodialysis:

• The presence in the peritoneum of mesenteric vessels that divert blood from the intestine to the portal system of the liver increases the effectiveness of dialysis in oral poisoning with hepatotropic drugs.
• The presence of a large amount of fat in the abdominal cavity creates conditions for effective dialysis of lipotropic toxicants, rapidly concentrated in fat stores (chlorinated hydrocarbons, etc.), by directly washing them with a dialysing fluid.
• The presence of the so-called hatches in certain places allows the possibility of dialysis not only of crystalloids, but also of large-molecule proteins, thereby creating conditions for effective dialysis of toxicants that quickly and firmly come into contact with plasma proteins.

Decrease in blood pressure and the accompanying acidosis lead to an increase in the permeability of the capillary walls, which under these conditions allows to maintain the dialysis process at a sufficient level.

A purposeful change in the physico-chemical properties of dialysis solutions, in addition, allows to increase the efficiency of peritoneal dialysis taking into account similar characteristics of toxicants. Alkaline dialyzing solutions are most effective in poisoning with drugs of a weakly acidic nature (barbiturates, salicylates, etc.), acidic - poisoning with poisons with the properties of weak bases (chlorpromazine, etc.), which results in the ionization of a toxic substance that prevents its reverse absorption from dialyzing solution into the blood, neutral dialyzing solutions are most suitable for removing poisons with neutral properties (FOI, etc.). The possibility of using lipid peritoneal dialysis for poisoning with fat-soluble drugs (dichloroethane) is considered, and the addition of protein (albumin) to dialyzing liquid can increase the excretion of drugs with a pronounced ability to bind to proteins (barbiturates of short action, etc.), which depends on the sorption of toxic substance on the surface of albumin, which allows maintaining a significant concentration gradient of the substance between the blood plasma and the dialysate until it reaches saturation surface of the adsorbent.

When acute exogenous poisoning is recommended fractional method of peritoneal dialysis, which allows to achieve a high intensity of excretion of toxic substance and at the same time providing a constant control over the volume of the introduced and withdrawn dialysis liquid and its most complete contact with the peritoneum. In addition, with the fractional method, such complications of peritoneal dialysis as infection of the abdominal cavity, large protein losses and some others are most effectively prevented.

Fractional method is that a special fistula with an inflatable cuff is inserted into the abdominal cavity with the help of the lower-medial laparotomy, and a perforated catheter is inserted through the fistula between the peritoneum sheets, along which the dialysate moves in both directions. Since the amount of dialysate solution that can be simultaneously introduced into the abdominal cavity is limited (within 2 liters), the intensity of the PD is maintained by regular dialysate change at certain time intervals (exposure). Thanks to this methodical feature of peritoneal dialysis, another approach to increasing its effectiveness is the correct choice of exposure. At the same time, the exposure should be such as to ensure the greatest possible accumulation of a toxic substance in the dialysis liquid. An increase in exposure beyond the optimal period leads to resorption, the flow of a reverse transfer of toxic substance into the blood, which significantly reduces the effectiveness of the operation.

In patients with acute renal failure, the effectiveness of any method of replacement of kidney function depends on the rate of ultrafiltration. Peritoneal dialysis is influenced by permeability of the peritoneum, osmolarity and exposure time of the dialysis solution, as well as the state of hemodynamics. When using solutions with theoretical osmolarity up to 307 mosm / L, the rate of ultrafiltration does not exceed 0.02 ml / kg x min). The use of highly osmolar solutions (up to 511 mosm / l) allows it to increase to 0.06 ml / kg x min). The principle of the method of peritoneal dialysis is based on the diffusion mass transfer of the liquid and the substances dissolved in it from the vascular bed and the surrounding tissues into the dialysate through a semipermeable membrane - peritoneum. The rate of diffusion transport depends on the concentration gradient between the blood and the dialysate, the molecular weight of the substances, and the resistance of the peritoneum. Naturally, the higher the concentration gradient, the higher the rate of peritoneal transport, so frequent changes in dialysate in the abdominal cavity can maintain a high level of mass transfer during the procedure.

The rate of ultrafiltration in peritoneal dialysis depends on the state of hemodynamics and the selected therapy for circulatory insufficiency. Theoretically, the blood flow through the peritoneal vessels is maintained at a satisfactory level even with a fall in systemic blood pressure. However, severe hemodynamic disorders, centralization of blood circulation, infusion of significant doses of cardiotonics and vasopressors negatively affect peritoneal blood flow and the rate of mass transfer. That is why, despite the fact that peritoneal dialysis can be effective in patients with unstable hemodynamics, the degree of effectiveness of the procedure in patients of this category, of course, decreases.

In many clinics of the world preference is given to "acute" peritoneal dialysis as a replacement for renal therapy in newborns and infants, taking into account the minimal adverse effect of this method on the parameters of hemodynamics, the lack of the need for vascular access and the use of systemic anticoagulation. Early onset of dialysis in children with acute renal failure or polyorganic insufficiency syndrome allows to quickly correct the water-electrolyte imbalance, metabolic disturbances, provide clearance of exo-and endogenous toxins, carry out adequate volume of infusion-transfusion therapy and nutritional support during complex intensive therapy.

From a practical point of view, this method is simple and accessible to any intensive care unit, it does not require complicated and expensive equipment and large staff labor. However, with all its advantages in pediatric practice, in a number of cases a situation arises that requires a more dynamic correction of gross violations of the water-electrolyte and metabolic balances. With hypervolemia threatening edema of the lungs, critical hyperkalemia and lactic acidosis, neither technical difficulties nor the problems of adequate vascular access, nor a host of other important methodological issues can be a limitation for the use in children of extracorporeal detoxification techniques.

The method of peritoneal dialysis in acute poisoning

Equipment	Fistula with inflatable cuff, perforated catheter (silicone, rubber), dialysate tanks
System of highways	The Y-shaped, leading backbone is connected to a dialysate tank located above the body level of the patient, and the outflow line is connected to a dialysate collection vessel located below the body level of the patient
Access to the abdominal cavity	Lower-median laparotomy, puncture insertion of the catheter
Volume of dialysate solution	1700-2000 ml, with a stable tendency to fluid retention in the abdominal cavity - 850-900 ml
Temperature of the dialysate solution	38 0-38 5 C. With hypo- or hyperthermia, the temperature of the dialyzing solution can be correspondingly increased or decreased within 1-2 C
Recommended Modes	With the possibility of laboratory monitoring, peritoneal dialysis is discontinued with the disappearance of a toxic substance from the dialysate that is removed from the abdominal cavity. In the absence of laboratory monitoring, peritoneal dialysis is carried out until clear clinical signs of improvement in the patient's condition (when psychotropic and hypnotic drugs are poisoned - the onset of a superficial sopor), when poisoning with chlorinated hydrocarbons, FOI and other poisons - no less than 6-7 shifts, and when poisoning with psychotropic and hypnotics, the number of shifts can be brought to 20-30 pH dialysing fluid for poisoning phenothiazines, FOI and compounds of heavy metals and arsenic 7.1-7.2 - sl (addition of 15-25 ml of a 4% solution of sodium bicarbonate to 800 ml of the dialysing liquid), with noxiron poisonings 7.4-7.45 - neutral (25-50 ml of 4% sodium bicarbonate solution), and when poisoning with barbiturates and other poisons 8.0-8.5 - alkaline (150 ml of 4% sodium bicarbonate solution). When poisoning with heavy metals and arsenic compounds, 1 ml of a 5% solution of unithiol is added to each dialysing fluid change, unitiol is also injected intravenously at a rate of 200-250 ml of a 5% solution per day. Exposure of dialysing fluid in the abdominal cavity for poisoning with chlorinated hydrocarbons and compounds of heavy metals and arsenic - 20 min, with poisoning FOP - 25 min, in other cases - 30 min
Indications for use	Laboratory critical concentrations in the blood of dialysing poisons with a pronounced affinity for proteins Clinical detoxifications (exotoxic shock, expressed hemolysis, etc.), poisoning with chlorinated hydrocarbons aniline and other fat-soluble hepatotrophic poisons
Contraindications	Extensive adhesive process in the abdominal cavity. Foci of infection in the abdominal cavity. Pregnancy is more than 15 weeks. Tumors deforming the abdominal cavity

Contraindications for peritoneal dialysis

Conduction of peritoneal dialysis is impossible after extensive abdominal operations, with diaphragmatic or inguinal hernia, etc.

[1], [2], [3], [4], [5], [6], [7]

Complications of peritoneal dialysis

The most formidable complication of peritoneal dialysis is peritonitis. Indeed, until the middle of the last century, this complication severely limited the use of the method in clinical practice. Meanwhile, since the 70s of the last century, with the introduction of soft silicone catheters, commercial, factory-made dialysis solutions, modification of locks of dialysis lines, and with full compliance with asepsis and procedures, the threat of peritonitis has significantly decreased.

In addition, there is a risk of hypoproteinemia, since the possibility of loss of protein in peritoneal dialysis (up to 4 g / day) and hyperglycemia due to the use of dialysis solutions (high glucose concentration due to high glucose concentration) is proved.

[8], [9], [10], [11], [12], [13], [14],