By Claire Boyd

Intravenous infusion devices relieve health careers from frequent medication administration and improve safety. Here are the most common types used in IV therapy:

  • Gravity infusion devices: Depend entirely on gravity to drive the infusion through the drip chamber, from the container/bag of fluid, through the line to the cannula. The roller clamp controls the flow, which is measured by counting the drops dripping into the chamber. The pressure to drive the flow is dependent entirely on the height of the container/bag of liquid above the infusion site, which is set at about 1 metre, to deliver the correct pressure of 70 mm Hg. These devices are simple to set up and low-cost, but they can’t be used when resistance to flow is high, such as when the liquid to be infused is very viscous.

  • Volumetric pumps: Deliver large volumes of fluid in millilitres per hour. They deliver accurate amounts of fluids and can detect air in the administration set by an alarm. Their disadvantage is that staff have to be trained to use them, because they’re quite complicated.

  • Syringe drivers (pumps): Empty syringes at a set rate. They’re used where small volumes of highly concentrated drugs are delivered at low flow rates. They deliver accurate amounts of drugs in millilitres per hour. They can be complicated to use, however, and staff need to be trained before being able to use them and to be aware of free flow and backlash. At low rates, the backlash (or mechanical slack) must be taken up before a steady flow rate is achieved, because at low flow rates some time passes before any fluid reaches the patient.

  • Patient-controlled analgesia (PCA) pumps: Allow the patient to self-administer a bolus of analgesia through a specialised volumetric or syringe pump. These devices have built-in safety systems to prevent overdosing, while running with a background infusion.

  • Ambulatory pumps: Miniature, battery-driven versions of volumetric and syringe pumps that patients can carry around with them, at home or in the hospital. They administer micro-boluses in a continual sequence.