MALPOSITION OF ARTERIAL CANNULAE
Carotid or innominate artery
hyperperfusion
·
Aetiology
1) Oxygenator related
a) Break in integrity of connections
b) Detachment of oxygenator from holder
c) Non venting of oxygenator eg occluded gas port
d) Bumping of oxygenator during operation
2) Pump related
a) Runaway arterial pump
b) Reversal of main pump
c) Reversal of vent pump
d) Cardioplegia pump flow rate exceeds arterial pump flow rate
e) Pump boot rupture
f) Inappropriate venting
i) Aortic root venting with open left atrium/ventricles
ii) Cardiac venting while aortic arch is opened (without aortic X-clamp)
3) Venous reservoir related
a) Inattention to level
b) Failure of level sensing devices/ air sensing devices
4) Cardiotomy related
a) Production of positive pressure at the input to the reservoir with air forced retrogradely up purge lines/ impair venous drainage
i) High vent/cardiotomy flow rates
ii) Plugging of filters due to clotting
5) Surgical
a) Reversal of cannula
b) Insertion of left ventricular vents
c) Open heart procedures
d) Unexpected resumption of heart beat
(1) Eg mitral valve surgery on fibrillating heart without X-clamp
·
Prevention
1) Adherence to checklist
2) Attention to venous level
3) Attention to pump flows
4) Adequate heparinisation
·
Diagnosis
1) Visual presence of bubbles in circuit
2) Air emboli detector activation
3) Raised S-T segments, poor cardiac output, dysrhythmias
·
Management
1) Management of massive systemic air
embolism
a) Stop CPB
b) Place patient in steep Trendelenburg’s position [Head down]
c) Clamp venous line & open recirculation line - allow bubbles in arterial line to passively retrogradely drain by gravity [several hundred mls max]
d) Reprime pump circuitry
i) Small quantity bubbles in arterial line
(1) Surgeon removes A-line/cannula, flush blood
ii) Large quantity bubbles in circuit
(1) Surgeon joins a-line to v-line, recirculate/prime circuit
e) Reestablish antegrade CPB
f) Hypothermia 20°C
i) Increased gas bubble solubility
ii) Minimise organ damage due to hypoperfusion while bubbles are being resorbed by increased gas solubility
g) Induce hypertension
i) Vasoconstrictors
ii) Hydrostatic pressure shrinks bubbles
h) Express coronary air by massage & needle venting
i) Drugs?
i) Steroids
ii) Mannitol
iii) Barbiturate coma (especially if embolism occurred while normothermic)
j) Perfuse for 45 min
k) Wean from CPB
l) Continue ventilating with 100% O2 for at least 6 hours to displace N2
m) Options:
i) Retrograde cerebral perfusion
(a) Options
(i) Connect arterial line to SVC cannula with tourniquet
1. Perfuse 20°C blood at 1 l/min into SVC
2. Measure cerebral pressure from IJ (< 25 mm Hg)
(ii) Coronary sinus cannula in SVC (preferable)
1. Perfuse 20°C blood at 600 ml/min via coronary sinus
2. Measure cerebral pressure from IJ or coronary sinus (< 25 mm Hg)
(b) 100% O2
(c) Air + blood drains from the aortic cannula hole in aortic root
(d) Carotid compression is performed intermittently to retrogradely purge vertebral arteries
(e) Continue for 1-2 minutes after air is seen exiting aorta (usually < 5 min total)
ii) Retrograde IVC perfusion
(1) Rarely done
(2) Performed after SVC perfusion
(3) To prevent reembolisation of brain:
(a) Carotid arteries are clamped
(4) Continue for 1-2 minutes after air is seen exiting aorta (approx < 5 min total)
iii) ?Hyperbaric chamber
(1) Good results
(2) Difficult to organise
2) Management of Localised myocardial
air embolism
a) During X-clamping
i) Surgeon initiated cardiac deairing techniques (needle aspiration, ballotment etc)
ii) Appropriate venting
iii) Retrograde cardioplegia
b) Post removal X-clamp
i) Dissipate bubbles
(1) Raised coronary perfusion pressures
(2) 100% oxygen
(3) Hypothermia usually not applicable
ii) Reduce ischaemia
(1) Raised coronary perfusion pressures
(2) Minimal ventricular distention
(3) Sinus rhythm
(4) Minimal inotropes (increases myocardial workload)
iii) Anticipate inotropes, pacing, IABP to wean
[Reduced blood flow draining into pump]
·
Aetiology
1) Air enters venous line via cannula in right atrium
a) Coronary sinus cannulae
b) Venous cannula
2) Excessive exsanguination (eg during circulatory arrest)
·
Prevention
1) Maintain adequate right atrial filling during insertion right atrial cannula
·
Diagnosis
1) Rapidly falling venous reservoir level
·
Management
1) Source of air entry must be closed
2) ‘Milk’ air into reservoir
3) Temporarily reduce pump flow rate, add fluid to reservoir
Mechanical
·
Aetiology
1) Lifting heart impairs venous drainage
2) Kinked venous cannulae
3) Malpositioned venous cannula
4) Too small venous cannula
5) Presence of thrombus or tumour
·
Prevention
1) Observe for high regional venous pressures
2) Adequate heparinisation
·
Diagnosis
1) Rapidly falling venous reservoir level
2) Increased CVP (note if CVP monitored within RA may still remain low)
Note: Difficult to ascertain an IVC obstruction
·
Management
1) Reduce pump flow until cause identified
Aortic dissection (or
femoral dissection)
·
Aetiology
1. Cannula orifice is located within aortic wall not lumen
·
Prevention
1. Degree of damage ie extension of false lumen can be minimised by diagnosing problem before commencing CPB
2. Monitor for pulsatile waveform of a mean pressure correlating with radial line (after correcting for height difference between CPB & patient)
·
Diagnosis
1. Inappropriate high arterial line pressures
2. Inappropriate very low radial pressures
3. Loss of volume
4. TOE
5. Organ hypoperfusion (pupil dilation, anuria)
·
Management
1. Discontinue CPB
2. Surgical reposition of cannulae
3. Surgical repair of aorta
·
Complications of
aortic dissection
1. Global hypoperfusion
2. Occlusion origin of arteries from aorta
3. Occlusion of aorta
4. Aortic rupture
5. Aortic regurgitation
· Aetiology
1. Preferential direction of perfusion into brachiocephalic artery
· Prevention
1. Surgical vigilance
2. Use of short aortic cannula with flange
·
Diagnosis
1. Ipsilateral
a) Blanching of face (not seen if blood in prime)
b) Pupil dilation
c) conjunctival oedema
2. Low left radial BP
3. Low femoral BP
4. High right radial BP (if innominate hyperperfused)
· Management
1. Reposition aortic cannulae
2. Reduce cerebral oedema (mannitol; head up)
·
Complications
1. Cerebral oedema
2. Arterial rupture
·
Aetiology
1. Blood is drained from aorta
2. Blood is pumped into vena cava
·
Prevention
1. Monitor for pulsatile waveform of a mean pressure correlating with radial line
·
Diagnosis
1. Severe arterial hypotension
2. High CVP
3. Facial oedema
·
Management
1. Discontinue CPB
2. Place patient in steep Trendelenburg’s
3. Disconnect cannulae & observe for air (if air is present follow gas embolism protocol)
4. Resume CPB
5. Consider mannitol, steroids, barbiturates to reduce cerebral oedema
·
Complications
1. High venous pressures may rupture veins
2. Bubble formation in aorta which may be reinfused when problem is corrected
·
Aetiology
1. Cannulae lumen against wall of aorta
2. Long thin cannulae
3. Small lumen cannulae
·
Prevention
1. Monitor for pulsatile waveform of a mean pressure correlating with radial line
2. Use as large an orifice as possible
3. Avoid long narrow cannulae
·
Diagnosis
1. High aortic line pressures
·
Management
1. Reposition cannula
2. Replace cannula
·
Complications
1. Hypoperfusion
2. Haemolysis
3. ‘Sand blasting” effect of artery intima
·
Aetiology
1. Inadequate gas flow
2. Hypoxic gas mixture
3. Leaks in O2 supply line
·
Prevention
1. Use of O2 analyser on gas inflow line
2. Observe rise of flowmeter bobbin
3. Ensure tightness of fit in all fresh gas delivery components
4. Observe fall and then brisk rise of bobbin when momentarily clamping fresh gas supply line
5. Feel hot oxygenator effluent gas
6. Effluent gas (CO2) monitoring
·
Diagnosis
1. Dark blood in arterial line (same colour as venous)
2. Dropping SvO2
3. Blood gases
4. Severe vasodilation
·
Management
1. Connect portable O2 tank to oxygenator
2. Urgently contact maintenance engineers (dial 33) and medical gas fitters
3. Exhale down gas inflow line
4. Cool patient maximally
·
Aetiology
1. Electrical failure
2. Mechanical failure
3. Runaway pump
·
Prevention
1. Availability of backup equipment
2. Frequent servicing of equipment
3. Battery backup
·
Diagnosis
1. Pump unresponsive to RPM control
·
Management
1. The patient should be maintained in one of the following states
a) Normothermic with cardiac output and ventilation
b) Enough volume in patient to enable internal cardiac massage and ventilation
c) Deep hypothermic arrest
2. If pump stops — isolate source of power loss:
3. Pump module failure:
a) Clamp patient off CPB
b) Replace module
a) Adjacent module (eg sucker)
b) Replacement module
4. Total mains AC failure
a) Hand crank main pump to maintain SvO2 > 60%; ensure correct direction of rotation
b) Use torch to monitor venous reservoir level
5. If total mains AC failure, air compressor will be off
6. Disconnect gas line from blender and reconnect to O2 out
7. Automatic take over of emergency generator should occur within 5 sec
8. Urgently contact maintenance engineers (dial ??: switch board)
·
Aetiology
1. Pump module circuitry failure
·
Prevention
1. Availability of backup equipment
2. Frequent servicing of equipment
·
Diagnosis
1. Unable to manipulate rpm of pump
·
Management
1. Switch off module
2. Hand crank main pump to maintain SvO2 > 60%
3. The patient should be maintained in one of the following states while replacing module:
a) Normothermic with cardiac output and ventilation
b) Enough volume in patient to enable internal cardiac massage and ventilation
c) Deep hypothermic arrest
4. Replace module
·
Aetiology
1. Heat exchange loss of integrity within oxygenator
2. Note: small leaks may be difficult to diagnose
·
Prevention
1. Test heat exchanger by subjecting to very cold water prior to priming, observing for a raising fluid level within oxygenator
·
Diagnosis
1. Rising venous reservoir level
2. haemoglobinuria
·
Management
1. Exchange oxygenator [see oxygenator exchange protocol]
2. To remove excess blood water:
a) Haemoconcentrator
b) Cell saver
3. Drugs:
a) Diuretics; mannitol
b) Antibiotics
·
Aetiology
1. Manufacturing defect
2. Clogging due to clot
3. Disruption of shell (trauma, spill of Isoflurane)
·
Prevention
1. Availability of backup equipment
·
Diagnosis
1. Dark blood in arterial line (same colour as venous)
2. Dropping SvO2
3. Blood gases
· Management
1. If failure is partial but deteriorating, cooling (or rewarming?) may be instituted to render the patient in one of the following states:
a) Normothermic with cardiac output and ventilation
b) Enough volume in patient to enable internal cardiac massage and ventilation
c) Deep hypothermic arrest
2. Remove from failing oxygenator:
a) Water lines
b) Gas outlet line
c) Temperature probe
3. Turn off pump
4. Clamp patient ‘off CPB’; clamp arterial and venous lines
5. Double clamp (leaving 1 inch between clamps) adjacent to connectors at oxygenator:
a) Arterial outlet
b) Venous inlet
c) Cardioplegia outlet
6. Cut [close to clamp nearest oxygenator]
a) Arterial outlet
b) Venous inlet
c) Cardioplegia outlet
d) Gas line
7. Remove defective oxygenator (and keep)
8. Install new oxygenator into holder : ensure is tilted with recirculation port on top
9. Attach cut tubing to
a) Arterial outlet
b) Venous inlet
c) Cardioplegia outlet
d) Gas port
10. Remove all 4 clamps
11. Add additional prime to venous reservoir
12. Prime oxygenator via recirculation line
13. Reestablish CPB with bleed line from arterial filter open
·
Aetiology
1. Worn tubing 2° overocclusion
2. Foreign object in pump head
3. Faulty tubing or connector
·
Prevention
1. Correct occlusion
2. Assess pump boot:
a) Visually
b) Observe for leaks when priming
3. Keep pump head covered
·
Diagnosis
1. Leakage of blood from pump boot
·
Management
1. The patient should be maintained in one of the following states while replacing pump boot:
a) Normothermic with cardiac output and ventilation
b) Enough volume in patient to enable internal cardiac massage and ventilation
c) Deep hypothermic arrest
2. Collect and assemble spare pump boot with 1/2-1/2 inch connectors at both ends
3. Clamp patient ‘off CPB’
4. Double clamp (leaving 1 inch between clamps) adjacent to connectors at oxygenator:
a) Arterial outlet
b) Venous reservoir outlet
5. Cut [close to clamp nearest oxygenator]
a) Arterial outlet
b) Venous reservoir outlet
6. Attach new pump boot to venous outlet
7. Prime new pump boot antegradely by removing venous reservoir outlet clamp and clamping distal end when primed
8. Attach distal end of pump boot to arterial inlet
9. Install pump boot into pump head
10. Remove remaining clamp
11. Debubble via recirculation line
12. Reestablish CPB with bleed line from arterial filter open
·
Aetiology
1. Inadequate heparinisation
2. Direct administration of FFP to reservoir during CPB
·
Prevention
1. Appropriate and frequent assessment of ACT:
a) Prior to commencement of CPB
b) 1/2 - 1 hourly interval whilst on CPB
c) Whilst rewarming
d) More vigilance when heparin resistant
2. FFP should be heparinised in bag (1000 u per bag) prior to administration
·
Diagnosis
1. Elevated arterial line pressures [indicating clotting arterial filter]
2. Elevated pre oxygenator pressures [indicating clotting within oxygenator]
·
Management
1. Stop CPB
2. Replace oxygenator & circuit
3. The patient should be maintained in one of the following states while replacing circuit & oxygenator:
a) Normothermic with cardiac output and ventilation
b) Enough volume in patient to enable internal cardiac massage and ventilation
c) Deep hypothermic arrest
4. Reheparinise patient & circuit using a different batch of heparin
<