Infusion technology: a cause for alarm

[corrected] Volumetric infusion pumps are widely used in paediatric practice. Tissue extravasation is a hazard. The occlusion pressure limit alarm, although not intended to detect extravasation, is the only warning sign present to indicate flow faults in the infusion systems.

Extravasations were created in the subcutaneous plane of 20 limbs of five piglets with normal saline via an infusion pump. Five flow rates were used with each piglet allocated to one: 100 ml.h-1, 200 ml.h-1, 300 ml.h-1, 400 ml.h-1, 500 ml.h-1. The occlusion pressure limit was first set at low and adjusted to medium, then to high, upon alarm activation. Line pressure at 5-min intervals and upon alarm activation and volume of infusate given were measured. Limb diameters before and after infusion were measured.

Six out of 20 cases failed to activate any alarm. The low, medium and high occlusion pressure limit alarms were activated in 14, 1 and 0 instances, respectively. The incidence of alarm activation is higher in the forelimb compared with the hindlimb (P=0.001). The tissue compliance and volume infused at alarm activation are significantly lower in the former (P < 0.05). Line pressure increases with increase in flow rates for the same limb (P=0.013 Fore, P=0.005 Hind).

Occlusion pressure limit alarm cannot reliably detect extravasation especially at sites with high compliance, low flow rates, even at low occlusion limit. Line pressure depends on interplay of site (compliance) and flow rate and is independent of volume extravasated. Users must be aware of the set occlusion pressure limit. Repeated clinical assessment remains vital.