Infusion therapy involves the controlled delivery of fluids, medications, or nutrients directly into a patient’s body. This method is used when substances cannot be safely taken by mouth, when a rapid effect is needed, or when medication must be administered precisely and continuously. Infusions ensure therapeutic agents bypass the digestive system, where they might be destroyed or poorly absorbed, providing a reliable route for treatment. The choice of infusion type depends on the medication, the required duration of therapy, and the patient’s health condition.
Peripheral Infusions
A peripheral infusion is the most common form of intravenous access, involving placing a short, flexible catheter into a small vein, typically located in the hand or arm. This method is used for short-term therapy, usually lasting less than four days, and is common in emergency departments and hospital wards. A healthcare provider inserts and secures the catheter through the skin into the vein for slow delivery of treatment.
Common uses include short-term hydration with solutions like normal saline, routine antibiotics, or pain medication. Because the vein is small and the blood flow is relatively slower, peripheral lines have limitations on the substances they can safely handle. Highly concentrated solutions, such as certain chemotherapy drugs or total parenteral nutrition, can irritate the inner lining of these veins, potentially causing phlebitis (inflammation). Due to complication risks, the catheter site requires rotation and replacement every three to four days.
Central Infusions
A central infusion is used when a patient requires long-term access, needs large volumes of fluid, or must receive medications that are too irritating for peripheral veins. This method uses a catheter that is significantly longer than a peripheral line, with its tip positioned directly into a large vein near the heart, such as the superior vena cava. Placing the tip in this central location allows the infused substances to be immediately diluted by the body’s massive blood flow, minimizing irritation to the vessel walls. The insertion of these devices, known as Central Venous Access Devices (CVADs), requires specialized training and is often performed under sterile conditions using imaging guidance.
Central access devices include Peripherally Inserted Central Catheters (PICC lines), tunneled catheters, and implanted ports. A PICC line is inserted into a peripheral vein in the arm, but the catheter is threaded all the way to the central vein. An implanted port is a small device placed completely beneath the skin in the chest, offering long-term, discreet access for therapies like chemotherapy or total nutritional support. These central lines can remain in place for weeks, months, or even years, providing a stable route for high-risk or continuous therapies, such as specific vasopressors or caustic medications.
Subcutaneous Infusions
Subcutaneous infusion, also called hypodermoclysis, delivers fluids and medications into the fatty tissue layer just beneath the skin, rather than directly into a vein. This technique is particularly useful when venous access is difficult to obtain or when the patient is receiving care in a setting outside of a hospital. The fluid slowly creates a pocket in the subcutaneous space, where it is gradually absorbed into the bloodstream through small capillaries. Because of this slower absorption rate, the method is not suitable for treating severe dehydration or emergency situations.
Hypodermoclysis is often used in geriatric and palliative care settings for mild to moderate rehydration or pain medication administration. The advantages include the simplicity of insertion, the lower risk of serious bloodstream infection compared to central lines, and the ability to perform the procedure in a home or long-term care facility. Only non-irritating, isotonic solutions, such as normal saline, are appropriate for this route. The volume of fluid that can be administered is limited, typically to about 1.5 liters over a 24-hour period at a single site.