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A FLUID ADMINISTRATION SYSTEM FOR USE IN LARGE ANIMALS
217. A FLUID ADMINISTRATION SYSTEM FOR USE IN LARGE ANIMALS
P. Gootjes Wekgroep Anaesthesiologie, Fakulteit der Diergeneeskunde, Rijksuniversiteit Te Utrecht. The Netherlands
Introduction The department 'Veterinary Anaesthesiology' of the State University of Utrecht (Holland) has modified and adapted a fluid administration system for use in large animals (see Figure 1). This system has 3 special features: a)
an electronic device which enables the actual fluid flow to be measured
b)
an electronic air bubble detector
c)
a rotating arm which enables fluids to be administered whilst the patient is walking around in its box.
Materials and methods a)
An ordinary roller-pump (Ole Dich. Denmark) generates a
flow which can be varied stepwisely from 60 mls to 10 litres per hour.
Obviously, any type of flow inducer with sufficient
capacity can be used.
Unfortunately, a preset value of the output
of the roller-pump may vary significantly from the flow which is actually generated.
For example, the back-pressure generated
by the patient as well as the resistance to flow in the tUbing may seriously reduce the preset flow.
Therefore a device capable
of accurately measuring relatively small fluid-flows has been incorporated: the piston operated flow meter. this meter creates a
pressur~
on the pistons which in turn
generate a rotary movement of a crank-shaft. connected to both a generator.
count:i~g
The fluid-flow in
This crank-shaft is
device and an electronic pulse
An ITT/conoflow type Z-041 piston operated flow meter
218. was used having an accuracy of less than 0.5 percent of the value measured.
The pulse generator is connected to a separate
processing unit which records the actual flow in mls/hour as well as
the total amount
Of
fluid administered.
In addition, the total
amount of fluid to be administered can be preset (with a maximum of 100 litres).
Thus, if the preset amount of fluid has been
administered the flow inducer is automatically switched off. b)
Air bubbles in the tubing of the administration system
may arise from leaks in the piping or from empty fluid bottles. However,
air bubbles may also occur spontaneously when the
sOlution to be administered is prepared and stored under cool conditions whilst this sOlution is administered at an increased environmental temperature; through warming-up of the solution many small air bubbles may be generated.
It is essential, there-
fore, that the air bubble detector is built in at the distal end of the flow generating system. In the present system an electronic air bubble detector was incorporated.
This device operates on the principle that almost
all solutions for intravenous administration are electrically conductive.
Glucose-solutions are made electrically conductive
by a mixture of a small amount of normal saline.
The sOlution to
be administered flows through a vertical piece of perspex tUbing with a detecting electrode at each end.
Normally, the electrical
resistance between these two electrodes is low.
However, a small
air bubble between these two electrodes may dramatically increase the electrical resistance.
This increase in resistance is
detected and the flow inducer is subsequently switched off. the same time a loud alarm is switched on.
At
After the air bubble
has been ducted away via a tap system the flow inducer can be restarted.
219. Patient safety is a most important aspect of this kind of electronically operated system. because it should be realised that via the electrolyte solutions. the patient is indirectly connected to mains.
The I.E.C. (International Electrotechnical commission)
has suggested that the patient leak-current for medical electronic apparatus directly connected to the patient
(the so-called type
B apparatus) should not exceed 100 micro amperes.
The patient
leak-current of the present apparatus appeared to be 3 micro amperes which is well below the suggested maximum. c)
Finally. the tubing has to be connected to the patient.
In this department it appeared to be necessary to administer electrolyte solutions to patients (e.g. colic cases) in the immediate post-operative period when these animals were still in the recovery box.
Each of the padded recovery boxes has a
floor space of 6 x 6 metres.
From the flow inducer a strong
PVC-tubing is ducted to the centre of a rotating arm construction which is fixed to the ceiling of the recovery box.
The centre of
this rotating arm contains a specially designed connection mechanism for tubing: the lower part of this connector can be rotated unlimited. from the lower
p~
A reinforced. non-kinkable PVC-tubing runs of the tube connector to the horse.
The
length of this piping can be varied by means of a series of pUlleys. whereas a counterweight fixed to these pUlleys causes a slight pull on to the tubing.
As the horse moves. the relatively
heavy rotating arm will be pUlled around. thus the distal end of the tubing must be firmly fixed to the halter of the horse.
The
end of the tUbing is connected to the intravenous catheter and this connection is subsequently secured under a bandage.
220. The whole unit (i.e. pump, bubble detector and flow meter) as well as the electrolyte sOlutions are put on one trolley and thus intravenous administration of fluids can immediately be started at any time.
Whe. the rotating arm construction is not used both ends of the long tubing are sealed off.
Before use the tUbing is
disinfected with a 0.5 percent sOlution of one litre chloramine for 15 minutes, and
subsequently thoroughly flushed with 3 litres
normal saline over 30 minutes. In colic cases the total amount of fluids to be administered intravenously can be quite large, thus the trolley contains a large container in which intravenous sOlutions can be put together and thus, prolonged intravenous administration of electrolyte solutions can be carried out without having to change bottles or bags at regular intervals.
In many cases this system has been used
over a period of seveLcU days without any problems. Safety aspects If
resistance to flow is increased either in the PVC-tubing
or in the intravenous catheter the pressure inside the tubing will rapidly increase.
Therefore, a contact manometer is incorporate
which will set off an alarm and switch off the flow inducer when the pressure inside the tubing exceeds a value of 100 mm of mercury. In a Dutch hospital it was recently discovered that the electrolyte solution in the PVC-tubing contained small silicon particles (average diameter 2 mm).
It appeared that these
particles originated from the silicon tubing in the roller-pump: frequent massaging of the silicon tubing by the rOller-pump caused the release of the particles.
Therefore, it is an absolute
prerequisite that a filter distal to the roller-pump is incorporated in the system.
221.
pump
filter
flowmeter
airdetector
Pmax
o Figure 1
arm
horse
P. Gootjes Wekgroep Anaesthesiologie, Fakulteit der Diergeneeskunde, Rijksuniversiteit Te Utrecht. The Netherlands
Introduction The department 'Veterinary Anaesthesiology' of the State University of Utrecht (Holland) has modified and adapted a fluid administration system for use in large animals (see Figure 1). This system has 3 special features: a)
an electronic device which enables the actual fluid flow to be measured
b)
an electronic air bubble detector
c)
a rotating arm which enables fluids to be administered whilst the patient is walking around in its box.
Materials and methods a)
An ordinary roller-pump (Ole Dich. Denmark) generates a
flow which can be varied stepwisely from 60 mls to 10 litres per hour.
Obviously, any type of flow inducer with sufficient
capacity can be used.
Unfortunately, a preset value of the output
of the roller-pump may vary significantly from the flow which is actually generated.
For example, the back-pressure generated
by the patient as well as the resistance to flow in the tUbing may seriously reduce the preset flow.
Therefore a device capable
of accurately measuring relatively small fluid-flows has been incorporated: the piston operated flow meter. this meter creates a
pressur~
on the pistons which in turn
generate a rotary movement of a crank-shaft. connected to both a generator.
count:i~g
The fluid-flow in
This crank-shaft is
device and an electronic pulse
An ITT/conoflow type Z-041 piston operated flow meter
218. was used having an accuracy of less than 0.5 percent of the value measured.
The pulse generator is connected to a separate
processing unit which records the actual flow in mls/hour as well as
the total amount
Of
fluid administered.
In addition, the total
amount of fluid to be administered can be preset (with a maximum of 100 litres).
Thus, if the preset amount of fluid has been
administered the flow inducer is automatically switched off. b)
Air bubbles in the tubing of the administration system
may arise from leaks in the piping or from empty fluid bottles. However,
air bubbles may also occur spontaneously when the
sOlution to be administered is prepared and stored under cool conditions whilst this sOlution is administered at an increased environmental temperature; through warming-up of the solution many small air bubbles may be generated.
It is essential, there-
fore, that the air bubble detector is built in at the distal end of the flow generating system. In the present system an electronic air bubble detector was incorporated.
This device operates on the principle that almost
all solutions for intravenous administration are electrically conductive.
Glucose-solutions are made electrically conductive
by a mixture of a small amount of normal saline.
The sOlution to
be administered flows through a vertical piece of perspex tUbing with a detecting electrode at each end.
Normally, the electrical
resistance between these two electrodes is low.
However, a small
air bubble between these two electrodes may dramatically increase the electrical resistance.
This increase in resistance is
detected and the flow inducer is subsequently switched off. the same time a loud alarm is switched on.
At
After the air bubble
has been ducted away via a tap system the flow inducer can be restarted.
219. Patient safety is a most important aspect of this kind of electronically operated system. because it should be realised that via the electrolyte solutions. the patient is indirectly connected to mains.
The I.E.C. (International Electrotechnical commission)
has suggested that the patient leak-current for medical electronic apparatus directly connected to the patient
(the so-called type
B apparatus) should not exceed 100 micro amperes.
The patient
leak-current of the present apparatus appeared to be 3 micro amperes which is well below the suggested maximum. c)
Finally. the tubing has to be connected to the patient.
In this department it appeared to be necessary to administer electrolyte solutions to patients (e.g. colic cases) in the immediate post-operative period when these animals were still in the recovery box.
Each of the padded recovery boxes has a
floor space of 6 x 6 metres.
From the flow inducer a strong
PVC-tubing is ducted to the centre of a rotating arm construction which is fixed to the ceiling of the recovery box.
The centre of
this rotating arm contains a specially designed connection mechanism for tubing: the lower part of this connector can be rotated unlimited. from the lower
p~
A reinforced. non-kinkable PVC-tubing runs of the tube connector to the horse.
The
length of this piping can be varied by means of a series of pUlleys. whereas a counterweight fixed to these pUlleys causes a slight pull on to the tubing.
As the horse moves. the relatively
heavy rotating arm will be pUlled around. thus the distal end of the tubing must be firmly fixed to the halter of the horse.
The
end of the tUbing is connected to the intravenous catheter and this connection is subsequently secured under a bandage.
220. The whole unit (i.e. pump, bubble detector and flow meter) as well as the electrolyte sOlutions are put on one trolley and thus intravenous administration of fluids can immediately be started at any time.
Whe. the rotating arm construction is not used both ends of the long tubing are sealed off.
Before use the tUbing is
disinfected with a 0.5 percent sOlution of one litre chloramine for 15 minutes, and
subsequently thoroughly flushed with 3 litres
normal saline over 30 minutes. In colic cases the total amount of fluids to be administered intravenously can be quite large, thus the trolley contains a large container in which intravenous sOlutions can be put together and thus, prolonged intravenous administration of electrolyte solutions can be carried out without having to change bottles or bags at regular intervals.
In many cases this system has been used
over a period of seveLcU days without any problems. Safety aspects If
resistance to flow is increased either in the PVC-tubing
or in the intravenous catheter the pressure inside the tubing will rapidly increase.
Therefore, a contact manometer is incorporate
which will set off an alarm and switch off the flow inducer when the pressure inside the tubing exceeds a value of 100 mm of mercury. In a Dutch hospital it was recently discovered that the electrolyte solution in the PVC-tubing contained small silicon particles (average diameter 2 mm).
It appeared that these
particles originated from the silicon tubing in the roller-pump: frequent massaging of the silicon tubing by the rOller-pump caused the release of the particles.
Therefore, it is an absolute
prerequisite that a filter distal to the roller-pump is incorporated in the system.
221.
pump
filter
flowmeter
airdetector
Pmax
o Figure 1
arm
horse