Infusion pump

Infusion pumps can adminster fluids in ways that would be impractically expensive or unreliable if performed by nursing staff. For example, they can adminster 1ml/hour injections (too small for a drip), injections every minute, injections with boli (boluses) requested by the patient, up to maximum number per hour, or fluids whose volumes vary by the time of day.

Because they can also produce quite high but controlled pressures, they can inject controlled amounts of fluids subcutaneously (beneath the skin), or epidurally (just within the surface of the central nervous system- a very popular local spinal anesthesia for childbirth).

There are two basic classes of pumps. Large volume pumps can pump nutrient solutions large enough to support a patient. Small-volume pumps infuse hormones, such as insulin, or other medicines, such as opiates.

Large-volume pumps usually use some form of peristaltic pump. Classically, they use rollers compressing a silicone-rubber tube through which the medicine flows. Another common form is a set of fingers that press on the tube in sequence, a "peristaltic" pump.

Small-volume pumps usually use a screw that pushes the plunger on a syringe. A new design uses osmotic pressure to push fluids into patients, usually from very small pumps.

Almost all modern infusion pumps are controlled by a small embedded system. They are carefully designed so that no single cause of failure can harm the patient. For example, most have batteries in case the wall-socket power fails. Additional hazards are uncontrolled flow causing an overdone, uncontrolled lack of flow, causing an underdose, reverse flow, whcih can siphone blood from a patient, and air in the line, which can starve a patient's tissues of oxygen of it floats to some part of a patient's body.

Infusion pumps are used to perform sterile medical procedures that should only be performed by trained personnel under medical supervision, with proper equipment.

See also intravenous drip, life support, total parenteral nutrition and medicine