The Royal Marsden Hospital Manual of Clinical Nursing Procedures - Lisa Dougherty [579]
Pumps alarm at ‘occlusion alarm pressure’ and many pumps allow the user to set the pressure within a range (MHRA 2010b). Therefore, the time it takes to alarm depends on the rate of flow: high rates alarm more quickly. When the alarm is activated, a certain amount of stored medication will be present and it is important that what could be a potentially large bolus is not released into the vein. The release of the stored bolus could lead to rupture of the vein or constitute overinfusion, which may be detrimental to the patient, particularly if it is a critical medication (Amoore and Adamson 2003, MHRA 2010b). With a syringe pump, to prevent a bolus being delivered to the patient, the clamp should not be opened as this will release the bolus: the first action is to remove the pressure by opening the syringe plunger clamp and then deal with the occlusion.
While pressure occlusion may not prevent extravasation, it may minimize the risk of resulting complications (Quinn and Upton 2006). Single-unit variable pressure pump settings which allow an earlier alarm alert are used in neonatal and paediatric units (Quinn 2008).
Air in line
Air-in-line detectors are designed to detect only visible or microscopic ‘champagne’ bubbles. They should not create anxiety over small particles of air but alert the nurse to the integrity of the system. Most air bubbles detected are too small to have a harmful effect but the nurse should clarify the cause of any alarms (MHRA 2010b).
Antisyphonage
Uncontrolled flow from a syringe is called siphonage; this is a result of gravity or leakage of air into the syringe and administration set. Siphonage can occur whether or not the syringe is fixed into an infusion device (Quinn 2008). It has been reported that ‘in practice, a 50 mL syringe attached to a length of administration set with an internal diameter of 3 mm has been shown to empty by siphonage in less than 1 minute’ (Pickstone 1999, p.57).
To minimize the risk of siphonage, the following safe practice should be undertaken.
The syringe (plunger and barrel) should be correctly located and secured.
Intravenous administration extension sets should always be micro/narrow bore in diameter to increase the resistance to flow; wide-bore extension sets should be avoided.
Position of the syringe pump should always be the same level as the infusion site (MHRA 2010b).
Extension sets with an integral antisiphonage/antireflux valve should be used (MHRA 2010b, MHRA 2007, Quinn 2008).
Safety software
Smart pumps contain safety software also known as dose error reduction systems (Hertzel and Sousa 2009). There is an internal drug library, meaning that pumps are programmed to contain information on medications with upper and lower dosing limits (Hadaway 2010). A number of studies have evaluated the effectiveness of using smart pumps to prevent medication errors, showing the success of these systems (Dennison 2007, Fields and Peterson 2005, Larson et al. 2005, Rothschild et al. 2005).
Volumetric pumps
Volumetric pumps (Figure 13.29) pump fluid from an infusion bag or bottle via an administration set and work by calculating the volume delivered (Quinn 2008). This is achieved when the pump measures the volume displaced in a ‘reservoir’. The reservoir is an integral component of the administration set (Hadaway 2010). The mechanism of action may be piston or peristaltic (Hadaway 2010). The indications for use are all large-volume infusions, both venous and arterial.
Figure 13.29 Volumetric pump.
All are mains and battery powered, with the rate