Intravenous therapy or IV therapy is the giving of liquid substances directly into a vein. It can be intermittent or continuous; continuous administration is called an intravenous drip. The word intravenous simply means "within a vein", but is most commonly used to refer to IV therapy. Therapies administered intravenously are often called specialty pharmaceuticals.
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 and lethal injections, can only be given intravenously.
This is the most common method of intravenous drug use for euphoriants 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.
This is the most common intravenous access method in both hospitals and pre-hospital services. A peripheral IV line consists of a short catheter (a few centimeters long) inserted through the skin into a peripheral vein, any vein that is not in the chest or abdomen. There are times, however, when underlying physiological factors (morbid obesity, peripheral vascular disease and IV drug abuse, to name a few) make insertion into any available vein a medical necessity--particularly if the patient is exsanguinating. The adage "time is tissue" should be paramount during times like these or if the patient is at risk for a cardiac event. Arm and hand veins are typically used although leg and foot veins are occasionally used. Veins in the arm are the common site in emergency settings, commonly performed by paramedics and emergency physicians. On infants the scalp veins are sometimes used. The part of the catheter that remains outside the skin is called the connecting hub; it can be connected to a syringe or an intravenous infusion line, or capped with a bung between treatments. Ported cannulae have an injection port on the top that is often used to administer medicine. The caliber of cannula is commonly indicated in gauge, with 14 being a very large cannula (used in resuscitation settings) and 24-26 the smallest. The most common sizes are 16-gauge (midsize line used for blood donation and transfusion), 18- and 20-gauge (all-purpose line for infusions and blood draws), and 22-gauge (all-purpose pediatric line). 12- and 14-gauge peripheral lines actually deliver equivalent volumes of fluid faster than central lines, accounting for their popularity in emergency medicine; these lines are frequently called "large bores" or "trauma lines".
Blood can be drawn from a peripheral IV if necessary, but only if it is in a relatively large vein and only if the IV is newly inserted. Blood draws are typically taken with specialized IV access sets known as phlebotomy kits, and once the draw is complete, the needle is removed and the site is not used again. If a patient needs frequent venous access, the veins may scar and narrow, making any future access extremely difficult or impossible; this situation is known as a "blown vein," and the person attempting to obtain the access must find a new access site proximal to the "blown" area.
Originally, a peripheral IV was simply a needle that was taped in place and connected to tubing rather than to a syringe; this system is still used for blood donation sets, as the IV access will only be needed for a few minutes and the donor may not move while the needle is in place. 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. This method is a variation of the Seldinger technique. The external portion of the catheter, which is usually taped in place or secured with a self-adhesive dressing, consists of an inch or so of flexible tubing and a locking hub. For centrally placed IV lines, sets and flushes contain a small amount of the anticoagulant heparin to keep the line from clotting off, and frequently are called "heparin locks" or "hep-locks". However, heparin is no longer recommended as a locking solution for peripheral IVs; saline is now the solution of choice for a "vac lock".
A peripheral IV cannot be left in the vein indefinitely, because of the risk of insertion-site infection leading to phlebitis, cellulitis and sepsis. The CDC updated their guidelines and now advise the cannula need to be replaced every 96 hours. This was based on studies organised to identify causes of Methicillin-resistant Staphylococcus aureus MRSA infection in hospitals. In the United Kingdom, the UK Department of health published their finding about risk factors associated with increased MRSA infection, now include intravenous cannula, central venous catheters and urinary catheters as the main factors increasing the risk of spreading antibiotic resistant strain bacteria in hospitals.
There are several types of central IVs, depending on the route that the catheter takes from the outside of the body to the vein.
The PICC line is inserted into a peripheral vein using the Seldinger technique under ultrasound guidance, usually in the arm, and then carefully advanced upward until the catheter is in the superior vena cava or the right atrium. This is usually done by feel and estimation; an X-ray then verifies that the tip is in the right place.
A PICC may have two parallel compartments, each with its own external connector (double-lumen), or a single tube and connector (single-lumen). Triple connectors (triple-lumen) catheters and power-injectable PICCs are now available as well. From the outside, a single-lumen PICC resembles a peripheral IV, except that the tubing is slightly wider.
The insertion site must be covered by a larger sterile dressing than would be required for a peripheral IV, due to the higher risk of infection if bacteria travel up the catheter. However, a PICC poses less of a systemic infection risk than other central IVs, because bacteria would have to travel up the entire length of the narrow catheter before spreading through the bloodstream.
The chief advantage of a PICC over other types of central lines is that it is easy to insert, poses a relatively low risk of bleeding, is externally unobtrusive, and can be left in place for months to years for patients who require extended treatment. The chief disadvantage is that it must travel through a relatively small peripheral vein and is therefore limited in diameter, and also somewhat vulnerable to occlusion or damage from movement or squeezing of the arm.
In the simplest type of central venous access, a catheter is inserted into a subclavian, internal jugular, or (less commonly) a femoral vein and advanced toward the heart until it reaches the superior vena cava or right atrium. Because all of these veins are larger than peripheral veins, central lines can deliver a higher volume of fluid and can have multiple lumens.
Another type of central line, called a Hickman line or Broviac catheter, is inserted into the target vein and then "tunneled" under the skin to emerge a short distance away. This reduces the risk of infection, since bacteria from the skin surface are not able to travel directly into the vein; these catheters are also made of materials that resist infection and clotting.
The most commonly used crystalloid fluid is normal saline, a solution of sodium chloride at 0.9% concentration, which is close to the concentration in the blood (isotonic). Ringer's lactate or Ringer's acetate (ASERING, patented brandname of Otsuka Indonesia) is another isotonic solution often used for large-volume fluid replacement. A solution of 5% dextrose in water, sometimes called D5W, is often used instead if the patient is at risk for having low blood sugar or high sodium. The choice of fluids may also depend on the chemical properties of the medications being given.
Intravenous fluids must always be sterile.
|2/3D & 1/3S||3.3% Dextrose / 0.3% saline||51||51||185||3333|
|Half-normal saline||0.45% NaCl||77||77||0||0|
|Normal saline||0.9% NaCl||154||154||0||0|
|Ringer's lactate||Lactated Ringer||130||109||0||0|
Ringer's lactate also has 28 mmol/L lactate, 4 mmol/L K+ and 3 mmol/L Ca2+. Ringer's acetate (ASERING) also has 28 mmol/L acetate, 4 mmol/L K+ and 3 mmol/L Ca2+.
|Solution||Change in ECF||Change in ICF|
|D5W||333 mL||667 mL|
|2/3D & 1/3S||556 mL||444 mL|
|Half-normal saline||667 mL||333 mL|
|Normal saline||1000 mL||0 mL|
|Ringer's lactate||900 mL||100 mL|
An infusion pump allows precise control over the flow rate and total amount delivered, but in cases where a change in the flow rate would not have serious consequences, or if pumps are not available, the drip is often left to flow simply by placing the bag above the level of the patient and using the clamp to regulate the rate; this is a gravity drip.
A rapid infuser can be used if the patient requires a high flow rate and the IV access device is of a large enough diameter to accommodate it. This is either an inflatable cuff placed around the fluid bag to force the fluid into the patient or a similar electrical device that may also heat the fluid being infused.
Infection of IV sites is usually local, causing easily visible swelling, redness, and fever. If bacteria do not remain in one area but spread through the bloodstream, the infection is called septicemia and can be rapid and life-threatening. An infected central IV poses a higher risk of septicemia, as it can deliver bacteria directly into the central circulation.
Due to frequent injections and recurring phlebitis, the peripheral veins of intravenous drug addicts, and of cancer patients undergoing chemotherapy, become hardened and difficult to access over time.
Air bubbles of less than 30 milliliters are thought to dissolve into the circulation harmlessly. Small volumes do not result in readily detectable symptoms, but ongoing studies hypothesize that these "micro-bubbles" may have some pejorative effects. A larger amount of air, if delivered all at once, can cause life-threatening damage to pulmonary circulation, or, if extremely large (3-8 milliliters per kilogram of body weight), can stop the heart.
One reason veins are preferred over arteries for intravascular administration is because the flow will pass through the lungs before passing through the body. Air bubbles can leave the blood through the lungs. A patient with a heart defect causing a right-to-left shunt is vulnerable to embolism from smaller amounts of air. Fatality by air embolism is vanishingly rare, in part because it is also difficult to diagnose.