Infusion therapy (Latin infundere, infusus: to pour into) or fluid therapy refers to the parenteral (Greek para: next to; enteron: intestine; “bypassing the digestive tract“) continuous administration of fluids for medical purposes. An infusion of blood is called a transfusion. Parenteral nutrition (artificial feeding by special infusion solutions) is also a form of infusion therapy, but it describes a broad field of its own.
Indications (areas of application)
- Drug infusion therapy: administration of drugs when the patient is unable to do so himself or when precise, direct continuous administration of the drugs is required for them to have their best possible effect.
- Volume replacement therapy: this infusion therapy is necessary when there is an absolute volume deficiency (blood loss from the vascular system, e.g., injuries) or a relative volume deficiency (relatively lower blood volume due to vasodilatation).
- Fluid intake: therapy for dehydration (lack of fluid), e.g., vomiting, diarrhea (diarrhea), or decreased water intake.
- Electrolyte therapy: when electrolyte balance is disturbed, e.g., hypokalemia (potassium deficiency), this condition can be life-threatening depending on its severity.
- Macro- and micronutrient therapy (vital substance therapy): Prevention and therapy with macro- and micronutrients (nutrients, vital substances) – usually based on a nutritional analysis or a vital substance analysis.
The procedure
Infusion therapy is used for drug administration, macro- and micronutrient supplementation (nutrients, vital substances) and fluid substitution (support of fluid balance). It is necessary when oral (fluid intake by mouth) or enteral (fluid intake via the digestive system) absorption of fluids is disturbed or not possible to the extent that the patient is no longer adequately supplied or the necessary dosage is not possible by oral intake.Objectives of infusion therapy:
- Drug administration or administration of diagnostic agents (eg, contrast media): precisely dosed administration of drugs directly into the bloodstream.
- Volume replacement therapy or fluid supplementation: compensation for fluid loss (e.g., due to diarrhea (diarrhea), vomiting, or blood loss). The goal is to maintain and normalize the volume of fluid or blood to stabilize the circulation.
- Electrolyte therapy: correction and maintenance of vital electrolyte concentrations and their composition.
- Macro and micronutrient therapy (vital substance therapy): prevention and therapy with macro and micronutrients (nutrients, vital substances).
Infusion therapy can be short-term or long-term and applied (lat. applicare: connect) through various routes:
- Intravenous infusion: this is the most common method. The infusion is administered via a vein, either peripherally (on the limbs, e.g., dorsum of the hand, forearm, crook of the elbow, dorsum of the foot), via an indwelling venous cannula, or centrally via a central venous catheter into a large vein near the heart (into the superior or inferior great vena cava). The latter can also be done via a port catheter: A central venous port is a subcutaneous (under the skin), fully implanted access system connected to a central vein (right jugular or subclavian vein). Large volumes of fluid can be injected long-term through a membrane that can be punctured multiple times.
- Intra-arterial infusion: this is a less common method. The infusion is done through an artery, this has the effect that the fluid is distributed quickly through the circulation. An example of this is the administration of contrast medium into the coronary vessels (arteries that surround the heart in a coronary shape and supply the heart muscle with blood) as part of a coronary angiography (radiological procedure that uses contrast media to visualize the lumen (interior) of the coronary arteries (coronary vessels)).
- Subcutaneous infusion: in this case, an infusion is given just under the skin. Because absorption (uptake) of the fluid is slow, it is a method that is gentle on the circulation.
- Intraosseous infusion: In this infusion, fluid is injected into the bone marrow (eg, lower leg bone).This method is often used in children during an emergency when intravenous access is not available.
- Epidural infusion: here, fluid is infused into the epidural space (synonym: peridural space; space in the spinal canal that lies between the bone surface and the dura mater (hard meninges), surrounding the spinal cord; usually used for administration of a local anesthetic or injected for pain therapy, for example, as part of an epidural anesthesia (synonym: peridural anesthesia; form of central line anesthesia, which means that large nerve tracts are anesthetized directly at their root within the spine).
The following types of infusion are possible:
- Gravity infusion: this is the most common type of infusion. Fluid is administered by gravity through an elevated infusion container.
- Pneumatic pressure infusion: In this infusion, a plastic infusion container is compressed. The increased pressure allows large amounts of fluids to be administered in a short time, for example in emergency situations.
- Infusion pump / syringe pump: via a timed apparative system, the fluid to be injected is administered with the most precise dosage. The main area of application is in the administration of small amounts of fluid in intensive care and emergency medicine, in postoperative pain therapy and anesthesia (anesthesiology).
The composition of the infusion solution determines the goal of infusion therapy:
- Crystalloid infusion solutions: Full electrolyte solutions; this solution is used for dehydration (lack of fluid) due to diarrhea or vomiting.
- Two-thirds electrolyte solution: infusion of this solution is used to meet basic fluid needs during or shortly after surgery.
- Half-electrolyte solution: for dehydration.
- Colloidal infusion solution: contains hydroxyethyl starch (“HES”, from vegetable starch) and is used for volume replacement in case of blood loss or low blood volume[The German Society for Internal Intensive Care and Emergency Medicine (DGIIN) recommends, based on current data (due totherapy-resistant pruritus; increased rate of renal replacement than under treatment with Ringer’s acetate), to refrain from administering hydroxyethyl starch (HES) as part of fluid substitution in internal intensive care patients).Note! HES 130 is associated with increased mortality, increased need for renal replacement procedures, and increased transfusion requirements in ICU and sepsis patients.
Further notes
- Restrictive intravenous volume replacement therapy or fluid supplementation to avoid postoperative weight gain may be more likely to result in renal injury (8.6 versus 5.0%), surgical wound infections (16.5 versus 13.6%), and postoperative renal replacement therapy (0.9 versus 0.3%). This finding argues for more liberal volume therapy. However, in accordance with guidelines, infuse only enough fluid to prevent patients from gaining weight, if possible.
Benefit
Infusion therapy has become an indispensable part of everyday clinical practice. Both in emergency medicine, as well as in the doctor’s office, it is used. It helps patients get well or stay well.