As infusion (for Latin infusio , infusion, pouring, sprue ', and infundere , pour penetrate') is referred to in medicine (as opposed to one-time injection ) continuous, generally parenteral administration of liquid drugs ( infusion therapy ). In addition to intravenous administration, subcutaneous, intraosseous and intra-arterial administration are also possible.
Certain therapy methods usually involve the use of infusions, e.g. B. fluid administration , volume replacement or substitution , volume and osmotherapy. The administration of blood components by infusion is known as transfusion .
In addition to pure fluid therapy, infusion solutions are still used in parenteral nutrition and as carrier solutions if the duration of administration is not to be shortened or if certain maximum drug concentrations at the infusion site are not to be exceeded (electrolyte therapy, acid-base correction, administration of antibiotics, chemotherapy, etc.). ).
Infusion solutions and indications
Different preparations are available for infusion therapy. A distinction can be made between non-specific solutions such as electrolyte solutions (“crystalloids”) or glucose solutions from those with a specific therapeutic purpose, e.g. B. colloidal solutions for volume therapy, highly concentrated glucose solutions and other nutrient solutions for nutritional therapy or buffer solutions for treating disorders of the acid-base balance.
Electrolyte solutions are used to compensate (in the case of dehydration ) or to cover fluidrequirements, as part of parenteral nutrition and to compensate for electrolyte disorders. Due to the low colloid osmotic pressure, they onlyremainin thebloodvessels for a short time and are distributed in the extracellular space , which is why they are onlysuitable to avery limited extent for compensating for large blood losses in hypovolemic shock . Because of the rapid redistribution, there is a risk of cerebral and pulmonary edema if larger amounts are administered.
To distinguish it from colloidal solutions (English colloids ), electrolyte solutions are also referred to as crystalloids based on the English term crystalloids .
Isotonic saline solution
The simplest electrolyte solution is the isotonic saline solution , which due to its unphysiological composition is mostly only used as a rinsing and dilution solution . A special indication is isotonic dehydration (general water and salt deficiency).
Full electrolyte solutions
Full electrolyte solutions (VEL) or balanced solutions such as B. the Ringer's solution contain electrolytes ( sodium , potassium , calcium , partly magnesium , chloride ) in a body-like composition. Since they lack the negatively charged proteins and the hydrogen carbonate of the plasma, organic anions such as acetate , malate or lactate are added as a substitute , which results in isotonicity . According to recent research results, lactate should no longer be used because of its considerable disadvantages. The range of applications for fully electrolyte solutions is wide; they represent the standard of crystalloid solutions.
Industrial brand products include Sterofundin , Jonosteril and Ringer's lactate .
Special forms are half, 2/3 or 1/3 electrolyte solutions (designation according to the electrolyte content of the full electrolyte solutions), the use of which has largely been abandoned. There are also combination solutions with colloids or glucose.
Colloidal infusion solutions for use as volume replacement ( plasma replacement ) or in volume therapy ( plasma expander , "blood thinning" or hemodilution ) are characterized by their macromolecule content ( carbohydrates such as hydroxyethyl starch (HÄS) or dextrans ; proteins such as gelatine or albumin ). Since these volume substitutes cannot cross the vascular wall, the colloid-osmotic pressure they increase is maintained until the molecules are eliminated via enzymatic degradation or uptake by the mononuclear phagocytosis system . In addition to the longer retention time in the vascular system compared to electrolytes, this also results in a more pronounced and longer-lasting effect on the blood volume, which is why they are used to compensate for greater volume losses in hypovolemic shock .
Possible side effects are changes in blood clotting (tendency to bleed), anaphylactic reactions and acute kidney failure . It has not been established that colloidal solutions are more suitable than electrolyte solutions for use after trauma , burns, or surgery , or that patient death rates are reduced.
Glucose solutions are available in various concentrations. They serve as an energy supplier in the context of an infusion therapy. Since they do not contain any electrolytes and spread quickly into the intracellular space (“free water”), there is a risk of cerebral and pulmonary edema if larger amounts are administered . Glucose solutions are also part of total parenteral nutrition.
Osmotherapeutics are hypertonic infusion solutions whose active ingredients ( mannitol , glycerine ) lead to an increase in the osmotic pressure in the extracellular space and thereby remove water from the surrounding tissue. Areas of application of osmotherapeutic agents are the treatment of edema and the promotion of urine flow to prevent or treat acute kidney dysfunction or to promote the excretion of toxic, urinary substances in the event of poisoning.
For parenteral nutrition , mixed bags are used which - each separately in individual chambers - contain a glucose and an amino acid solution. Before administration, the separating seam is opened by pressing or rolling up the bag so that the solutions flow into one another. By means of an injection option, suitable additives such as water-soluble vitamins or trace elements can be added to the mixture before administration . Three-chamber bags also contain a lipid emulsion; fat-soluble vitamins can be added here. Examples of mixed solutions are (trade names): Aminomix (D, A), Nutriflex (D, A), Olimel (D), SmofKabiven (A), StructoKabiven (D, A).
The intravenous standard application of infusion solutions is via a venous catheter in a peripheral vein conducted. If long-term use, parenteral nutrition or the administration of vein-irritating drugs (sodium bicarbonate, potassium solution) are intended, a central venous catheter (CVC) with the tip in a central vein is indicated. The port catheter , which is used for chemotherapy and parenteral nutrition , among other things , is a special form of the CVC.
The intraosseous puncture and infusion therapy on the bone marrow are reserved emergencies and are used especially in children for use. In human medicine, subcutaneous infusions are being carried out more and more frequently, especially in geriatrics and palliative medicine , although not all drugs are suitable for this form of administration. In veterinary medicine , subcutaneous infusion is very common.
Infusions can be administered using gravity systems or with mechanical assistance. The methods can also be combined, whereby the gravity infusion is secured with a check valve so that the pressure of the pump control does not cause backflow.
Gravity Driven Infusions
In the so-called gravity infusion , the liquid is supplied through the hydrostatic pressure gradient between the infusion container and the patient. For this purpose, the infusion solution is hung on one of the hooks of an infusion stand by means of a holder, B. is attached to the head of the bed or as a mobile device with lockable castors on the floor. The infusion container must be above the patient's heart level. The dosage of the drip speed takes place via a simple roller clamp of the infusion system .
With a pressure infusion cuff or a pressure infusion device, large amounts of an infusion solution can be infused very quickly.
Precise dosing is only possible using infusion pumps . The connection between the infusion device and the cannula is made with an infusion line, which can be extended with a Heidelberg extension if necessary . This requires a special infusion line that is compatible with the respective device and that is inserted into the pump. A special form of infusion are the so-called syringe pumps (perfusors), which administer medication at low propulsion speeds . This includes the so-called PCA pump , with which the patient can administer a preset dose of his medication himself at the push of a button.
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