Infusion Pump Controlled Delivery of Fluids

An infusion pump is a medical device used to deliver (or infuse ) fluids into a patient’s circulatory system in a controlled manner. It is generally used intravenously.

Infusion pumps can administer fluids in ways that would be impractically expensive or unreliable if performed manually by nursing staff or anesthetist. For example:

• They can administer as little as 0.1 mL per hour injections (too small for a drip).
• Injections every minute.
• Injections with repeated boluses requested by the patient, but controlled and up to maximum number per hour (e.g. in patient-controlled analgesia).
• Fluids whose volumes vary by the time of day (change in volume happens many times during surgery).

Infusion pumps may be capable of delivering fluids in large or small amounts, and may be used to deliver nutrients or medications, such as

• Insulin or other hormones.
• Antibiotics.
• Chemotherapy drugs.
• Pain relievers.

Infusion pumps  are occasional used as subcutaneous (beneath the skin), arterial and epidural (just within the surface of the central nervous system which is for local spinal anesthesia for childbirth) in fusions apart from the generally used intravenous infusion

Design of Infusion Pump

Infusion pumps may be powered electrically or mechanically. Different pumps have their own designs and hence operate in different ways. Some infusion pumps are designed mainly for stationary use at a patient’s bedside. Others, called ambulatory infusion pumps, are designed to be portable or wearable. Batteries are also provided in pumps, so the pump can operate if the power fails or is unplugged. Given below are some generally used infusion pumps:

• In a Syringe Pump, fluid is held in the reservoir of a syringe, and a moveable piston controls fluid delivery.

• In an Elastomeric Pump, fluid is held in a stretchable balloon reservoir, and pressure from the elastic walls of the balloon drives fluid delivery.

• In a Peristaltic pump, a set of rollers pinches down on a length of flexible tubing, pushing fluid forward.

Features in a Modern Infusion Pump:

1. Pumps available in Multi-channel form , in which fluids can be delivered from multiple reservoirs at multiple rates.
2. They are equipped with safety features:

• User-alerts that activate when there is a risk of an adverse drug interaction, or when the user sets the pump’s parameters outside of specified safety limits.
• Alarms when syringe is not attached properly or patient’s vein is blocked or line to the patient is kinked .
• Alarms when Infusion of medication is completed.
• Equipped with  air-in-line or bubble detector which is a  typical detector that use an ultrasonic transmitter and receiver to detect when air is being pumped. Some pumps actually measure the volume, and may even have configurable volumes, from 0.1 to 2 ml of air. None of these amounts can cause harm, but sometimes the air can interfere with the infusion of a low-dose medicine.
• Many pumps include an internal electronic log of the last several thousand therapy events.

References and Further reading:

1. http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/GeneralHospitalDevicesandSupplies/InfusionPumps/ucm202495.htm
2. http://en.wikipedia.org/wiki/Infusion_pump
3. http://www.adph.org/ems/assets/studentmanual_ivinfusionpumps.pdf