Necessary parameters required to
terminate bypass on a patient
Parameters that must be observed
while going on to CPB
Parameters that must be observed
while going on to CPB
Temperature regulation, gas flow,
blood flow and pressures going onto CPB
Possible problems & methods to
rectify these problems when going onto CPB
Indications of pharmacological
intervention when coming off CPB
|
|
C |
V |
P |
|
|
Cold Conduction Calcium Cardiac
output Cells
(red) Coagulation |
Ventilation Vaporiser Vol
expanders Visualisation |
Protamine Pressure Pressors Pacer Potassium Predictors |
1.
Cold
a)
>
37°C core
2.
Conduction
a)
Rate
i)
HR:
70-100 /min
b)
Rhythm
i)
Ideal
SR
3.
Calcium
a)
Hypocalcaemia
b)
Hyperkalaemia
4.
Cardiac output
a)
Equipment
should be available to assess post CPB
5.
Coagulation
a)
Additional
heparin when rewarming
b)
Platelet
(thrombocytopaenia, aspirin, CRF, redo)
c)
FFP
(factor deficiencies)
d)
DDAVP
(increase platelet aggregation for: CRF, von Willebrand)
6.
Cells (red)
a)
Hct
> 21
b)
Patients
with residual coronary stenosis or anticipated low CO require higher Hct
|
|
1.
Ventilation
a)
Physiological
ABGs on CPB
b)
Lung
reexpansion (resolution of atelectasis)
c)
Mechanical
ventilation prior to coming off CPB
2.
Vaporiser
a)
Inhalational
agents should be turned of 15-20 min prior to termination CPB (decrease
contractility)
3.
Visualisation
a)
Contractility
b)
Distension
1.
Protamine
a)
The
perfusionist, anaesthetist and surgeon must all co-ordinate the use of this
drug
2.
Pressure
a)
Calibration
& rezeroing
b)
Migration
of PA catheter (wedge position)
c)
Damping
of radial line (peripheral vasoconstriction)
3.
Pressors & Inotropes
a)
Easy
availability of at least a vasodilator and an inotrope
4.
Pacer
a)
Availability
of an external pacemaker
5.
Potassium
a)
Hyperkalaemia
(negative inotrope, heart blocks)
b)
Hypokalaemia
(dysrrhythmias)
c)
Glucose
in diabetics
6.
Predictors
a)
Risk
factors that predict difficulty for weaning off CPB:
i)
Preop
EF < 0.45
ii)
Preop
evolving infarct
iii)
Prolonged
CPB (> 2-3 hr)
iv)
Inadequate
surgical repair
a)
Non
graftable small vessels
b)
Sub
optimal valve repair
v)
Incomplete
myocardial protection
a)
ECG
activity despite plegia
b)
Prolonged
VF
c)
Warm
myocardium
(1)
Poor
LV venting
(2)
LV
hypertrophy
(3)
Severe
coronary stenosis
b)
Addition
preparations for high-risk
i)
Inotropes,
IABP
ii)
commencement
of inotropes prior to weaning
1.
Prior to cannulation
a)
All
gas bubbles expelled from prime
b)
All
tubing connected for antegrade flow
c)
All
clamps appropriately applied
d)
Oxygen
supplied to oxygenator
e)
All
safety alarms and shut off alarms functional & engaged
f)
Anticoagulation
adequate?
2.
Immediately following
cannulation
a)
Is
the aortic cannula inserted within the true lumen of the aorta?
i)
Aortic
pressure should be pulsatile
ii)
Aortic
pressure should correlate with radial pressure
b)
Any
bubbles in cannula?
c)
Surgical
tubing clamps removed?
3.
While going onto CPB
a)
Ensure
can infuse blood into patient prior to releasing venous clamp and draining
patient
b)
Oxygen
delivery
i)
Blender
on 100% O2
ii)
Flow
meter on appropriate flow
iii)
O2
analyser reading 100%
iv)
Arterial
blood bright red (compare with venous blood)
v)
SvO2
> 70%
vi)
ABG’s
c)
Pump
Flow
i)
Running
at predicted l/min
ii)
SvO2
> 70%
iii)
MAP
> 60 mmHg
iv)
Base
excess
d)
Arterial
line pressures
i)
High:
cannulation defects
e)
MAP
[low]
i)
Cannulation
of veins, false lumen
ii)
Inappropriate
clamping/unclamping
f)
Anticoagulation
i)
Repeat
ACT
g)
Anaesthetic
depth
i)
anaesthetic
gases
ii)
benzodiazepines
iii)
skeletal
muscle blockers
h)
ECG
i)
Ischaemia
(eg too low BP)
ii)
VF
( concern esp with AR)
i)
Filling
pressures
i)
CVP
a)
elevated
(impaired venous drainage)
ii)
PAP
a)
elevated
(aortic valve dx; manual manipulation of heart)
j)
Pump
prime temperature
i)
Ensure
is warm
ii)
Danger
of VF; vasoconstriction
While going onto CPB
—
Assessment of adequate flow,
drainage and oxygenation
1.
Ensure
can infuse blood into patient prior to releasing venous clamp and draining
patient
2.
Oxygen
delivery
a)
Blender
on 100% O2
b)
Flow
meter on appropriate flow
c)
O2
analyser reading 100%
d)
Arterial
blood bright red (compare with venous blood)
e)
SvO2
> 70%
f)
ABG’s
3.
Pump
Flow
a)
Running
at predicted l/min
b)
SvO2
> 70%
c)
MAP
> 60 mmHg
d)
Base
excess
4.
Arterial
line pressures
a)
High:
cannulation defects
5.
MAP
[low]
a)
Cannulation
of veins, false lumen
b)
Inappropriate
clamping/unclamping
6.
Anticoagulation
a)
Repeat
ACT
7.
Anaesthetic
depth
a)
anaesthetic
gases
b)
benzodiazepines
c)
skeletal
muscle blockers
8.
ECG
a)
Ischaemia
(eg too low BP)
b)
VF
( concern esp with AR)
9.
Filling
pressures
a)
CVP
i)
Expected
< 5
ii)
elevated
(impaired venous drainage)
b)
PAP
i)
Expected
< 15 mean
ii)
Elevated
(aortic valve dx; manual manipulation of heart)
iii)
Can
become kinked, obstructed
10.
Pump
prime temperature
a)
Ensure
is warm
b)
Danger
of VF; vasoconstriction
11.
Suction
pump flow rate
a)
Associated
with excessive haemolysis
While going onto CPB
— Perfusing a normothermic patient
1.
Gas flows
a)
Blender
on 100% O2
b)
Flow
meter on appropriate flow for normothermic patient
c)
O2
analyser reading 100%
d)
Arterial
blood bright red (compare with venous blood)
e)
SvO2
> 70%
f)
ABG’s
i)
If
taken too early will see influence of pre-CPB gas management
2.
Pump Flow
a)
Running
at predicted l/min
b)
SvO2
> 70%
3.
Pressure
[During phase of initial
total CPB; warm; aorta not clamped]
a)
If
pump flow is adequate, BP is not important in determining global perfusion during CPB but is important for maintaining regional perfusion
b)
Need
for adequate perfusion pressures:
i)
Coronary,
renovascular, carotid critical organ stenosis
a)
Autoregulation
not able to maintain perfusion when hypotensive
ii)
Chronic
hypertension
a)
Body
autoregulates at high BP
iii)
Myocardial
hypertrophy
a)
As
hypertrophy often precedes adequate coronary vascularisation, reduced ability
to autoregulate
c)
Management
i)
Lower
limit of MAP for patients with impaired autoregulation based on individualised:
a)
Severity
& location of stenoses
b)
Normal
BP
c)
Hct
d)
Myocardial
hypertrophy
e)
Aortic
regurgitation
f)
LV
drainage
ii)