Infusion pumps

Question 1

what are the different methods for setting up an infusion?

Answer 1

electrical vs non electrical methods

non electrical
* single drip count via IV giving set - the droplet size is a set amount and can alter rate by adjustable roller. relies on gravity
* elastomeric pumps

electrical
* volumetric devices - disposable cassette and reservoir system
* peristatilc pumps
* syringe driver - PCA, TCI

Question 2

what is an elastomeric pump?

Answer 2

balloon filled with infusion fluid
as elastic of balloon recoils, the fluid is infused
energy comes from stored elastic energy within ballon
downstream flow restrictor to limit the flow
hence rate of fluid is dependant on upstream emptying and downstream restriction

usually around 300ml in balloon

also a compressible resevoir for PCA functon

Question 3

what are the pros and cons of elastomeric pumps?

Answer 3

pros - low cost, can be used with PCA, no electricity

however less accurate and single use

Question 4

how does the PCA function work on an elastomeric pump?

Answer 4

downstream of flow restrictor so fills
can be pressed to give bolus
automatic lock out because needs time to refill

Question 5

what is a volumetric pump?

Answer 5

this is an electrical method for setting up an infusion. it may either be via a disposable cassette and reservoir system OR peristatic pump.

both have a microprocessor and pumps whcih control the volume of fluid being delivered

Question 6

how does a dispossbale cassette and reservoir system volumetric infusion work?

Answer 6

theres a small reservoir e.g. 5 ml. the valve is switched such that the infusate fills this reservoir and then the microprocessor causes valve to switch to empty into patient end. this is emptied via a cam driver.

Question 7

how does a peristatic pump work?

Answer 7

this is a volumetric pump
infusate from a reservoir goes through compressible tubing to a patient.
there is a series of cam followers which compress the tubing in a wave i.e. peristalsis to push the fluid along.

the tubing needs to be hard wearing and not remain compressed

Question 8

how does a syringe driver work?

Answer 8

syringe full of infusion fluid
plunger on the end
a screw is turned to push the plunger and empty the infusion at a set rate

microprocesor allows rate to be set
most accurate form
good for controlled drugs
but more expensive.

Question 9

what type of infusion device will a PCA use and how does this work?

Answer 9

PCAs can use elastomeric, volumetric or syringe driver.
there is a control button that delivers a set bolus and lock out period.

Question 10

what are the key components of any electrical infusion pump?

Answer 10

A motor / driving mechanism p e.g. screw of a syringe driver, cams of a peristaltic pump

microprocessor - controls pumps and rate - some contain drug libraries and PCA functions and some TCI algorithms.

Question 11

what is a TCI pump?

Answer 11

TCI = Target controlled infusion
a user sets a target for either the plasma or effect site.
a syringe driver will have a microprocessor that use algorithms based on height, weight, age to set up an accurate infusion to reach that target.

incoorporates pharmokinetic models.

Question 12

what is Diprifusor?

Answer 12

first TCI model created for propofol - used the marsh model

diprivan was the brand name for propofol
prefilled syringers with a chip on them recognised by diprofusor pump
this tag ensured safety but also buisiness scheme

now open label

Question 13

do you know any names of syringe drivers using TCIs?

Answer 13

Braun, alaris

Question 14

what are the safety features of an infusion device..

Answer 14

Alarms:
* low pressure - dissoconnection
* high pressure - occlusion or tissued - by pressure transducer
* air in line

multiple confirmatory keys - e.g. if you want to give a bolus - prevents accidental.

drug libraries - algorithms to calculate doses and rates of a drug to prevent user error.

antisyphoning and anti reflux valves - sphyphoning is extra fluid by effect of gravity, reflux is pressure downstream causes backflow into line.

Question 15

how is a pressure change within infusion device detected?

Answer 15

inline pressure monitors within tubing.

OR the force needed by the pump is measured - as the pump pushes the synringe, a steel plate is also pushed, this will distort the place and cause a change in resistance whcih is proportional to the pressure exerted.

Question 16

does an infusion pump alarm at any increase in pressure?

Answer 16

balance between safety and unnecessary regular disruption of flow
so usually set at a threshol
e.g. small kinks will increase pressure but are no problem or having small cannula.

Question 17

what errors may occur with IV infusion devices?

Answer 17

reflux
siphoning
incorrect drug entered to library so incorrect doses given e.g. 2% propofol but pump thinks its 1%
multiple infusions - have common space, so if you stop one but continue the other, a small amount will still be delivered.
electromagnetic interference of the microprocessor

Question 18

what are the limitations of TCI pumps?

Answer 18

limited in obesity - algorithms are validated

children - not all manufactures have paediatric algoirthms - kataria is only but over 3yrs and 15kg

potential for electrical interference and microprocessor errors.

Question 19

how are epidural infusions set up?

Answer 19

also use syringe drivers but yellow tubing and yellow labels to indicate it is an epidural connection.

user needs to tell microprocessor it is an epidural to get correct dosings.

Question 20

what is this..

Answer 20

anti reflux valve

Question 21

what is this..

Answer 21

anti syphoning valve

Question 22

what is this…

Answer 22

Syringe driver

Question 23

what is this

Answer 23

TCI pump
works as a syringe driver with pharmokinetic models to target an infusion

Question 24

what is this..

Answer 24

shows the ultrasonic sensor which detects air bubbles in a syringe driver

Question 25

what is this..

Answer 25

volumetric infusion device