intravenous
Meaning of intravenous: Speed is the point and equally the catch, since nothing given by this route can be recalled once it has entered the bloodstream.
Definition of intravenous
Intravenous means within a vein, and describes anything placed into or delivered through one. A drug given this way enters the circulation whole, without passing through the stomach or the liver first, so the full dose is available and effects begin within seconds to minutes. Fluids, blood products, contrast agents and nutrition are also given intravenously.
Why choose a vein?
Several reasons converge. The whole dose arrives, with none lost to incomplete absorption or broken down by the liver on first pass, so the amount given and the amount delivered are the same. Onset is immediate, which matters in an emergency. The rate can be changed or stopped mid-treatment, allowing an effect to be adjusted minute by minute. Molecules that digestion would destroy, including insulin and antibody drugs, survive by this route. Large volumes of fluid can be replaced quickly. Veins are used rather than arteries because pressure in them is low, so a puncture seals easily, and blood flows toward the heart, mixing and diluting whatever is added before it reaches any organ.
What kinds of access are there?
| Type | Where it ends | Typical use |
|---|---|---|
| Peripheral cannula | A small vein in the hand or forearm | Short courses of fluid or medication, days at most |
| Longer arm line | A deeper arm vein or, for a peripherally inserted central line, a large vein near the heart | Weeks of treatment, including antibiotics at home |
| Central venous access catheter | A large vein close to the heart | Irritant drugs, concentrated nutrition, pressure monitoring |
| Implanted port | The same large vein, from a reservoir under the skin | Repeated treatment over months, such as chemotherapy |
What can go wrong?
The catheter can slip out of the vein so that fluid collects in the surrounding tissue, which is uncomfortable with a harmless solution and damaging with a drug that irritates tissue. The vein itself can become inflamed and tender, or blocked by a small clot. Any line crossing the skin is a route for bacteria into the bloodstream, and this is the main hazard of lines that stay in place for a long time. Giving fluid faster than the circulation can accommodate overloads it. Because an intravenous infusion bypasses every natural barrier, the dose, the rate and the compatibility of anything mixed together all matter more than by other routes.
Also known as
Used in a sentence
The medication was given through an intravenous line.
Good to know
An intravenous dose reaches the circulation in full and cannot be retrieved once given, so both intended effects and unwanted ones appear faster than by any other route.
Word origin
Where “intravenous” comes from
From Latin intra, meaning within, and vena, meaning vein.