Preparations for Cardiopulmonary
Oxygenation and Carbon dioxide elimination
Circulation of blood
Diversion of blood from the heart to provide a bloodless
Venous blood drained by gravity from the right side of the
heart into the reservoir
Most commonly single venous cannulation followed.
Returns oxygenated blood from pump to aorta
Usually placed in ascending aorta/ femoral artery
When all venous blood draining toward the
heart is diverted into the pump oxygenator.
When only a portion of systemic venous
blood drains to the pump oxygenator while
passes through the right heart and lungs
and ejected by the left ventricle.
Generally adequate heparinisation requires a
activated coagulation time > 480 seconds.
ACT accurately measured within two minutes of
Concentration of drugs in the blood diluted by the
Supplemental medication necessary
Anesthesia,Analgesics and Amnesics
Position within the lumen of the aorta should be checked
Aortic pressure should be pulsatile and correlate with radial
Check Carotid pulsation
IV lines closed on heparinisation to prevent further
Check the zero and calibration of the arterial pressure
Insert nasopharyngeal temp. probe prior to
Foley’s catheter to check urine output.
Maintenance Of Bypass
ACT > 480 seconds
ACT checked every 30-60 mins
Perfusion pressure on CPB
Lower flow and pressure during CPB may optimise
revascularisation while higher flow and pressure may
minimise patient complication.
Cerebral Autoregulation: Mean ABP of 50-150mm Hg.
Higher perfusion pressure needed in severe
atheromatous states,advanced age, systemic
hypertension and diabetes
Pump flow on CPB
Careful balance between surgical visualization and
adequate oxygen delivery must be maintained
perfuses most of the microcirculation when
Hct is 22% and hypothermic CPB is used.
Mixed Venous saturation is 70%
Blood gas and acid base status
Should be checked soon after intitiation of CPB
Every 30-60 min
Arterial oxygenation maintained at 100 - 300mm Hg
Alpha Stat Vs. pH Stat
Uncorrected (37°C) pH is kept at 7.40
with PCO2 at 40 mm Hg creating a
relative alkalosis at the patient arterial
Maintains a pH of 7.40 and PCO2 of 40 mm
Hg when corrected for body temperature,
typically requiring the addition of CO2 during
Potent vasodilatory effect increased
cerebral blood flow.
May be advantageous in paediatric patients
Should be sufficient to
Suppress hypertensive or tachycardic responses to surgical
Prevent unconsciousness movement and respiration
because hypothermia reduces the anesthetic requirement
they are most commonly used during the rewarming periods.
Should cease during total CPB
During partial Bypass occasional ventilation wth
100% O2 may be needed.
Sign of renal perfusion
As a guide for fluid management
>1ml/kg/hr should be maintained
Lowers the blood viscosity counteracting the deleterious
viscosity changes caused by hypothermia
Organ blood flow improved
Optimal hematocrit > 20
Usually a clear priming(non-blood containing)
solution is utilised.
Fluid replacement during CPB
Based on Hb, < 5g/dl – Blood, otherwise usually colloids
If adequate diuresis cannot be produced an
ultrafiltration device added to CPB circuit t remove
Heparin may be removed during ultrafiltration, so
anticoagulation must be monitored frequently.
Systemic hypothermia is widely used during
CPB,therefore patient must be rewarmed
Core temp (nasopharnygeal / tympanic/bladder)
> 36°C prior to terminating CPB.
Order of rewarming: Vessel Rich> Muscle> Fat
Excessive perfusate heating not advisable
Denaturation of plasma proteins
Rewarming may be enhanced
By increasing blood flow
Use of arterial vasodilators(SNP)
Analysis and correlation of electrolyte , Acid
base balance and Oxygen transport status
Acid base status must be optimised
Increased Pulmonary hypertension
Metabolic acidosis due to inadequate tissue perfusion
Inadequate perfusion flow
A low hemoglobin level
Inadequate oxygenation of blood
NaHCO3 can be used to treat the primary cause
Serum K+ >4.0 meq/l to reduce the incidence f
- to treat hypocalcemia and hyperkalemia
Dose- 5-15 ml/kg,
can cause coronary spasm, augmentation of
Must be adequate to provide oxyge carrying capacity
HCt > 20% or greater is appropriate for termination of
Additional heparin may be needed because rewarming
accelerates heparin a metabolism
Blood products should be readily available to use if
needed(Platelets /FFP / fibrinogen)
Blood products can be used after termination of CPB
Re-establish adequate ventilation
Once ventricular ejection(pulsatile arterial waveform)
is seen, ventilation is started (4 - 6 breaths/min)
Also help to eliminate air from the pulmonary veins
Adequate oxygenation and ventilation amust be
nesured while pt is on CPB.
Lungs should be re-expanded with 2-3 sustained
breaths(15-20 seconds) with visualisation of bilateral
lung expansion and resolution of atelectasis
tracheal suction done
Prevent LIMA graft damage caused by lung
Inspired oxygen fraction should be 1.0
Other Drugs / Infusions
Vasopressors and inotropes
Because of the potential for hemodynamic instability during
and shortly after weaning from CPB, it is better to avoid
additional anesthetic adminstration.
Supplemental medications are best given during
Post ACC removal
Atleast 10-15 min should elapse after the removal of
the ACC before attempting sepertion from CPB.
Myocardial injury and edema are reduced by avoiding
myoacrdial perfusion pressures in excess of 60 mm
Hg in the first 10-15 mins after reperfusion.
Thereafter sustaining coronary perfusion pressure
above above 70 mmHG for the last 5-10 min of CPB
Final Checklist for Terminating
Ventilation – lungs ventilated with 100%
The patient is sufficiently rewarmed.
Complete de-airing done from heart/ grafts/
Optimal metabolic condition.
All equipment and drugs are ready.
Sequence Of events
Step1: Retarding the venous return to the pump
Slowly the venous line is partially occluded
Blood flow through RV increased - the Heart begins to
Preload- the amount of venous line occlusion is adjusted
carefully and maintain a certain optimal pre-
load(adequate cardiac output).
Step 2: Lowering pump flow into aorta
Attaining partial bypass
The rise in preload causes the heart to begin to contribute to
the cardiac output.
Reduced Pump outflow requirement
The amount of arterial blood returned from the pump to the
patient can be reduced
Cardiac function And hemodynamics carefully monitored
Readjusting venous line resistance
To maintain the constant filling resistance.
Step 3: Terminating Bypass
If the heart is generating adequate systolic pressure (90-
100 mm Hg) at an acceptable preload with a pump flow
of 1L/min or less the patient is ready for termination of
The pump is stopped and both pump cannulas are
Immediately After Terminating
Infusing blood from the pump
In adult patients, volume is infused at 50-100ml
increments from the venous pump reservoir to the
patient through aortic cannula
Should be watched for air bubbles in aortic cannula
W/F blood pressure/ filling pressures/ heart
Measuring cardiac function
Cardiac Index > 2.0 L/min/M2
Measuring patient perfusion
Adequate tissue perfusion –ABG/ pH after 5 min after CPB
U/O – normally rise after CPB.
Removing the venous cannulae
Removing the aortic cannula