Basic principles of infusion therapy: fundamentals of fluid and electrolyte balance
Authors: Maliutina N.V. 
Published: July 2021

Background. Infusion therapy (IT) is a method of managing the functions of the organism by influencing purposefully the morphological composition and physiological properties of blood through parenteral administration of organic and inorganic solutions. The main feature of IT is that the drug completely enters the bloodstream.
Objective. To describe the main characteristics of fluid and electrolyte balance and the IT principles.
Materials and methods. Analysis of the literature sources on this topic.
Results and discussion. Fluid comprises about 60 % of the human body (in children – 70-80 %, in adults – 60 %, in elderly – 50-55 %). Total fluid includes intracellular and extracellular. The latter, in turn, is divided into intravascular, interstitial and transcellular. Water balance involves the balance of fluid entering the body and the fluid being excreted. The main sources of water are beverages and food, however, about 300 ml per day is formed endogenously during oxidation processes. The main ways of the fluid excretion are its excretion in urine and stool, and perspiration losses. To calculate the physiological need of water for an adult, the body weight should be multiplied by the coefficient of 30 (up to 65 years), 25 (65-75 years) or 20 (more than 75 years). IT should also take into account the pathological losses of water from fever, vomiting, diarrhea, the presence of large wounds or burns, as well as reduction of the need in water in renal or heart failure. Thus, physiological needs, fluid deficiency, fluid volume as a result of pathological loss should be added, and the oral rehydration subtracted from this sum to calculate IT volume. There are 3 degrees of dehydration severity: I degree – deficiency of 1-2 liters, thirst, oliguria; II degree – deficiency of 4-5 liters, thirst, oliguria, dry skin, mucous membranes and tongue, general weakness; III degree – deficiency of 7-8 liters, consciousness disorders, decrease in arterial pressure, shock. The first degree can be overcome by oral rehydration, the second degree – by 50 % of oral rehydration and 50 % of IT, the third degree – by 70-100 % of IT. IT solutions are divided into crystalloids, colloids, polyatomic alcohols and special drugs. Preparations of polyatomic alcohols include, in particular, Reosorbilact, Sorbilact, Xylate (“Yuria-Pharm”). Complications of IT are divided into complications associated with the violation of the technique of entering the bloodstream (injuries of blood vessels and adjacent organs, hematomas, foreign bodies in the vessels and heart, the solution misplacement out of the vascular space); complications associated with the violation of the technique of drug administration (thromboembolism, air and fat embolism); complications associated with the wrong rate of solutions’ administration (heart overload, hypervolemia, pulmonary edema, cerebral edema); complications associated with the characteristics of infusion solutions (partial hemolysis of blood cells, acid-base imbalance, disorders of blood osmolarity, local cooling of the heart); complications associated with the IT method; complications due to individual intolerance; infectious complications in case of violation of asepsis and antiseptics; infectious diseases. Criteria for IT security include the knowledge of the drug composition and understanding of the instructions for its use; multicomponentity; use of the minimum effective doses; monitoring of the excreted urine and other fluids and infused solutions; strict control of fluid balance and blood circulation parameters.
Conclusions. 1. IT is an important tool in treatment of many diseases, which performs a wide range of tasks. 2. The IT solution should be chosen depending on the individual needs of the patient. 3. Criteria for IT safety include the knowledge of drug composition and instructions for its use; multicomponentity; use of the minimum effective doses; monitoring of excreted urine and infused solutions; control of fluid balance and blood circulation parameters.