Devices used to prevent inadvertent
emptying of the venous reservoir
Over pressure and air detector
systems in blood lines
Value of oxygen concentration meters
in gas lines
Necessary equipment required to
maintain CPB during a power failure
Value of high temperature warning,
flow meters & pressure shut down systems in water supply systems:
Methods used to prevent foreign
bodies entering the pump heads
Protocols of safety to prevent the
reverse rotation of roller pumps used as intracardiac suckers
Validity of line pressure monitoring
1.
Low level alarms systems
a)
Can
emit an alarm &/or turn off main pump automatically
b)
Reflectance
i)
Photoelectric
[visible light]
ii)
Infrared
a)
not
reliable
c)
Capacitance
i)
reliable
d)
Ultrasonic
e)
Reservoir
weight
i)
Detects
decreasing weight in reservoir 2° decreasing reservoir blood volume
ii)
Servoregulated
to pump head:
a)
Reduced
volume results in decreased pump flow rate
iii)
Use
for soft shell?
2.
Mechanical devices
a)
In
line ball valve
i)
Invasive
device
ii)
Placed
before pump head
iii)
If
reservoir empties, ball drops and occludes tubing thereby preventing emptying
of reservoir
iv)
As
pumping still continuous
a)
vacuum
+ cavitation
v)
Does
not work with centrifugal pumps
b)
Centrifugal
pump head
c)
Soft
shell reservoir
1.
Air detectors
a)
Sensor
clamps onto the arterial tubing
i)
Infrared
signal
ii)
Ultrasound
b)
Detects
bubbles > 0.5—1.0 cc in size
c)
Automatically
turns off pump + alarm
d)
Unable
to detect foam (microbubbles)
2.
Overpressure monitors
a)
Arterial
line pressure
i)
Monitored
continuously to detect:
a)
Obstruction
to arterial line
b)
malposition
of arterial cannula
c)
Dissection
d)
Obstruction
of filter
ii)
Pressure
must be interpreted in context of:
a)
Expected
pressure drop across the arterial cannula
b)
Flow
rates
c)
Patient’s
MAP
iii)
Useful
guide to:
a)
Proper
insertion of cannula prior to CPB
b)
Aortic
BP after CPB (with inaccurate radial BP)
b)
Preoxygenator
pressure
i)
Monitor
resistance to flow (pressure drop) within oxygenator
a)
Thrombosis
of oxygenator
b)
Design
faults of oxygenator
c)
Cardioplegia
pressure
i)
Aid
in cardioplegia delivery
a)
Adequacy
of delivery
b)
Technical
problem solving
ii)
Prevents
overpressurising coronary system with subsequent trauma
1.
Monitor
% of oxygen entering oxygenator
2.
Confirms
oxygen content within gas line
3.
Setting
a low level limit alerts for scenarios of oxygen gas failure:
a)
Mains
supply
b)
?
Blender
c)
Vaporiser
fault
i)
Not
correctly positioned on pins
d)
Gas
tubing break in integrity
i)
Should
be positioned as close to oxygenator as possible
4.
Does
not indicate adequacy of gas flow
a)
Could
theoretically indicate 100% with no gas flowing due to static presence of pure
oxygen in gas delivery tubing
1.
Primary
a)
Battery
power supply
b)
Handcrank
i)
Easily
accessible; stored on CPB machine
ii)
Important
to consider direction of rotation to prevent accidental rotation of flow
a)
Ratcheted
designs obviate risk of reverse rotation
c)
Battery
operated light source
i)
To
observe venous reservoir level
ii)
To
observe colour of blood
2.
Secondary
a)
Monitoring
of adequacy of perfusion
i)
SvO2
3.
Gas
supply
a)
Air
generators may go down
i)
Connect
O2 gas line bypassing blender direct to O2 outlet
1.
High temperature warning
a)
Determines
overheating in water supply
i)
>
42°C
ii)
Damages
blood
b)
Connected
to heater cut-off
c)
Indicates
problem:
i)
Thermostat
ii)
Hot
returning water
a)
Partial
blockage in heat exchanger with subsequent shunting
(1)
Blanket
Oxygenator
2.
Flow meters
a)
Can
be a mechanical spinning device or actually indicated on a meter
b)
Indicates
adequacy of flow
c)
Inadequate
flows:
i)
Partial
or complete blockage in heat exchanger
a)
Blanket
b)
Oxygenator
ii)
Obstructed
tubing
a)
Taps
b)
Kinks
3.
Pressure shutdown systems
a)
Determines
excessive pressures within water circuitry
b)
Excessive
pressures may impair integrity of heat exchanger componentry within oxygenator
thereby allowing water to enter blood
i)
Sepsis
ii)
Haemolysis
·
Physically
prevent foreign objects entering pump head
·
Pump
can only be operated if cover is correctly positioned
1.
One
way valves
a)
Designed
to prevent air from being pumped through a suction or vent line in the wrong
direction if either the pump is operated in the reverse direction or the tubing
is loaded into the pump head incorrectly at assembly
2.
Clear
marking of direction of flow on pump head
3.
Complexity
of reversing pump head rotation
a)
Several
stage procedure
b)
Several
buttons must be simultaneously pressed
4.
Perfusionist
check list
5.
Surgeon
checks function of vent prior to usage
1.
These
in-line pressures provide information about the function of the components in
the perfusion circuit
2.
Monitor
& display mean pressures only
3.
Operating
range of 0—500 mmHg
4.
Pressure
must be interpreted in context of:
a)
Expected
pressure drop across
i)
arterial
cannula
ii)
oxygenator
iii)
coronary
plegia cannulae
b)
Flow
rates
c)
Patient’s
MAP; aortic root; ostia; sinus
d)
Length
of tubing
e)
Diameter
of tubing
f)
Viscosity
of blood
In-line
pressure gradients
|
Locations for line pressure monitoring |
Typical pressure gradient mmHg |
Excessive pressure gradients |
|
Proximal to membrane oxygenator |
100-200 |
Inadequate anticoagulation Manufacturing defect |
|
Proximal to arterial filter |
30 |
Inadequate anticoagulation |
|
Proximal to arterial cannula |
50 |
Undersized Kink Dissection Tip against artery wall |
|
Proximal to plegic cannula |
|
Kink Tip against artery wall [ostia] |
1.
Temperature
gradients between various parts of the patient body
a)
Monitor
in several different sites
2.
Blood
overheating
a)
>
42°C: blood cellular & plasma protein damage
b)
>
37°C: enters brain, exacerbates ischaemic brain injury
3.
Rewarming
times dependent on:
a)
Heat
exchange between water & blood
i)
Performance
of heat exchanger
ii)
Performance
of heater/cooler unit
b)
Heat
exchange between blood & tissues
i)
Increased
times to rewarm:
a)
High
SVR with shunting of blood away from tissues
b)
Prolonged
hypothermia
c)
Temperature
differential between blood & water
i)
>
10°C associated with GME as O2 reduces in solubility
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