Infusion Pumps Tomado Web

Infusion Pumps
Accurate fluid infusion and drug administration is crucial for the optimum management
of a critically ill neonate. Continuous and controlled intravenous delivery of common
medications, such as inotropic agents, vasodilators, aminophylline, insulin, heparin etc.
via infusion pump is the preferred mode of therapy in acute care. This is especially true
for drugs with short halflives, so as to maintain a desirable constant serum concentration
and in situations when constant infusion of glucose is needed. Small babies or those with
compromised renal, cardiac or pulmonary function have limited fluid tolerance and hence
it is essential to use infusion pumps so as to prevent inadvertent volume overload. For
intensive care, more than one infusion pump is often required intiny babies where drug
dosage, concentration, interaction and fluid volume require separate infusion rates. The
use of infusion pumps has been advocated over manual flow control system on the basis
of assuring precise and accurate delivery of prescribed fluid volumes over a specified
time and to help in better nursing management.
Desirable specifications
A good infusion device should be:
1.2.
3.
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8.

reliable and electrically safe
able to deliver the infusion accurately and consistently
easy to set up and use
portable and robust
powered with battery and mains both
equipped with override rapid infusion facility
capable of alerting line occlusion and need to re-change syringe
able to display rate of infusion and volume infused clearly

Table 15.1: Typesof Infusion Pumps
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Gravity controlled
Positive displacement pumps

1

Drip rate regulators
Drip rate controllers
Drip rate pumps
Volumetric pumps
Syringe pumps
Multi-channel pumps
Ambulatory pumps

Types of infusion pumps
1. Gravity controlled devices
Drip rate regulators rely solely on gravity to regulate the rate of flow. The simplest
and cheapest systemsare dial-a-flow/ dosiflow which are supplied with standard
intravenous fluid administration sets. Infusion rate is also dependent on pressure
difference across the valve i.e. height of fluid or venous pressure/obstruction. In
addition, drip rate controller also relies on gravity to provide the infusion pressure. A
drop sensor attached to the drip chamber senses the drip rate. This feedbacksystem
can adjust the drop rate to a preset value, but, it cannot account for error incurred
because of variation in drop size.
2. Positive displacement pumps
Mechanism of action
These provide a positive displacement of fluid with the help of a motor. They are
designed so as to prevent infusion of a large volume of air or subcutaneous
infiltration. Positive displacement pumps have either aperistaltic or a piston
mechanism.
Infusion pumps utilize either linear or rotary mechanisms. Linear peristalsis consists
of finger like projections that sequentially compress the intravenous tubing against a
stationary back plate, thus moving the fluid in one direction. Rotator peristaltic pumps
have rollers on a wheel which compress the tubing and thus move fluid in the tubing
towards thepatient.
i) Drip rate pumps
These differ from gravity dependent drip rate controllers in providing a pumping
mechanism to replace gravity as the motive force. Similar to infusion controllers,
these pumps use drip sensor which are attached to administration set to count drops in
order to achieve control of infusion rate. The speed of pumping mechanism is under
feedback control from a dripsensor/counter. With pumping mechanism, occlusion
alarm pressure settings above 100 mm Hg are usual and some are over 200 mm Hg.
The high occlusion pressure can distend the administration tubing to the point of
bursting it. Hence, if there is extravasation, pump keeps on pumping fluid into the
tissues. This is a serious drawback of these pumps. Therefore, because of these
problems, volumetric...