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Encyclopedia > Intravenous fluid
An intravenous drip in a hospital


Compared with other routes of administration, the intravenous route is the fastest way to deliver fluids and medications throughout the body. Some medications, as well as blood transfusions, can only be given intravenously.


Intravenous access devices

Needle and syringe

The simplest form of intravenous access is a syringe with an attached hollow needle. The needle is inserted through the skin into a vein, and the contents of the syringe are injected through the needle into the bloodstream. This is most easily done with an arm vein, especially the antecubital vein. Usually it is necessary to use a tourniquet first to make the vein bulge; once the needle is in place, it is common to draw back slightly on the syringe to see a blood return, thus verifying that the needle is really in a vein; then the tourniquet is removed before injecting.

This is the most common method of intravenous drug use for illegal substances such as heroin, or in any case where a person must self-administer intravenous medication at home. It is also a convenient way to deliver life-saving medications in an emergency. However, in a controlled health-care setting, direct injection is rarely used since it only allows delivery of a single dose of medication.

Peripheral IV lines

This is the most common intravenous access method in both hospitals and paramedic services. A peripheral IV line consists of a short catheter (a few centimeters long) inserted through the skin into a peripheral vein. A peripheral vein is any vein that is not in the chest or abdomen. Arm and hand veins are typically used although legs and feet veins are occasionally used. Pediatricians sometimes use the scalp veins of infants. Part of the catheter remains outside the skin, with a hub that can be connected to a syringe or an intravenous infusion line, or capped with a bung between treatments.


Originally, a peripheral IV was simply a needle that was taped in place and connected to tubing rather than to a syringe. Today, hospitals use a safer system in which the catheter is a flexible plastic tube that originally contains a needle to allow it to pierce the skin; the needle is then removed and discarded, while the soft catheter stays in the vein.

A peripheral IV cannot be left in the vein indefinitely, because of the risk of insertion-site infection leading to bacteremia. Hospital policies usually dictate that every peripheral IV be replaced (at a different location) every three days to avoid this complication.

Central IV lines

Central IV lines flow through a catheter with its tip within a large vein, usually the superior vena cava, or within the right atrium of the heart. This has several advantages over a peripheral IV:

  • There is room for multiple parallel compartments (lumens) within the catheter, so that multiple medications can be delivered at once even if they would not be chemically compatible within a single tube.
  • Carers can measure central venous pressure and other physiological variables through the line.

Central IV lines also carry higher risks of bleeding, bacteremia, and gas embolism (see Risks below).


Peripherally inserted central catheter (PICC)





Central venous lines




Implantable ports

A port (often referred to by brand names such as Port-A-Cath or MediPort) is a central venous line that does not have an external connector; instead, it has a small reservoir implanted under the skin. Medication is administered intermittently by placing a small needle through the skin into the reservoir. Ports cause less inconvenience and have a lower risk of infection than PICCs, and are therefore commonly used for patients on long-term intermittent treatment.

Forms of intravenous therapy

Intravenous drip


IV fluids

There are two types of fluids that are used for intravenous drips: crystalloids and colloids. Crystalloids are aqueous solutions of mineral salts or other water-soluble molecules. Colloids contain larger insoluble molecules, such as gelatin; blood itself is a colloid.


Intravenous fluids must always be sterile.

Infusion equipment



In the absence of a pump, if the patient requires a high flow rate and the IV access device is of a large enough diameter to accommodate it, an inflatable cuff can be placed around the fluid bag to force the fluid into the patient.

Intermittent infusion


Risks of intravenous therapy



Any break in the skin carries a risk of infection. Although IV insertion is a sterile procedure, skin-dwelling organisms such as Staphylococcus aureus or Candida albicans may enter through the insertion site around the catheter, or bacteria may be accidentally introduced inside the catheter from contaminated equipment.



Phlebitis is irritation of a vein that is not caused by infection, but from the mere presence of a foreign body (the IV catheter) or the fluids or medication being given. Symptoms are swelling, pain, and redness around the vein. It does not necessarily mean the IV device must be removed; warmth, elevation of the affected limb, or a change in the rate of flow may resolve the symptoms.



This occurs when the tip of the IV catheter withdraws from the vein or pokes through the vein into surrounding tissue, or when the vein's wall becomes permeable and leaks fluid. It occurs frequently with peripheral IVs, and requires replacement of the IV at a different location. The symptoms of pain and swelling are temporary and not dangerous, unless a highly irritating medication was being given.

Fluid overload


Electrolyte imbalance

Administering a too-dilute or too-concentrated solution can disrupt the patient's balance of sodium, potassium, and other electrolytes. Hospital patients usually receive blood tests to monitor these levels.




See also

  Results from FactBites:
Intravenous therapy - Wikipedia, the free encyclopedia (2423 words)
Intravenous therapy or IV therapy is the administration of liquid substances directly into a vein.
  More results at FactBites »



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