This document discusses anesthetic management during cardiopulmonary bypass. It covers preparations for bypass including the circuit design and cannulations. It describes maintenance of bypass including anticoagulation, perfusion pressures, blood gas monitoring, and fluid management. The document outlines weaning from bypass including rewarming, optimizing acid-base balance and oxygen levels. It provides the sequence of events for terminating bypass including reducing pump flow and clamping cannulas. Post-bypass care including measuring cardiac function, tissue perfusion and removing cannulas is also summarized.

1. Anesthetic Management
During Cardiopulmonary
Bypass
Dr.N.Kanagarajan

2. Preparations for Cardiopulmonary
Bypass
 CPB CIRCUIT
 Function
 Oxygenation and Carbon dioxide elimination
 Circulation of blood
 Systemic Cooling
 Diversion of blood from the heart to provide a bloodless
surgical field

3.  CIRCUIT DESIGN
 Venous circuit
 Venous blood drained by gravity from the right side of the
heart into the reservoir
 Most commonly single venous cannulation followed.
 Arterial Cannula
 Returns oxygenated blood from pump to aorta
 Usually placed in ascending aorta/ femoral artery

4.  Total CPB
 When all venous blood draining toward the
heart is diverted into the pump oxygenator.
 Partial CPB
 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.

5. Anesthesiologist Pre Bypass
Check List

6.  Anticoagulation
 Generally adequate heparinisation requires a
activated coagulation time > 480 seconds.
 ACT accurately measured within two minutes of
heparin administration.
 Anesthesia
 Concentration of drugs in the blood diluted by the
prime
 Supplemental medication necessary
 Neuromuscular blockers
 Anesthesia,Analgesics and Amnesics

7.  Cannulations
 Aortic cannula
 Position within the lumen of the aorta should be checked
 Aortic pressure should be pulsatile and correlate with radial
artery pressure
 Check Carotid pulsation
 Drips
 IV lines closed on heparinisation to prevent further
hemodilution.

8.  Monitoring
 Check the zero and calibration of the arterial pressure
transducer.
 Insert nasopharyngeal temp. probe prior to
heparinisation
 Foley’s catheter to check urine output.

9. Maintenance Of Bypass
 Anticoagulation
 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

10.  Pump flow on CPB
 Careful balance between surgical visualization and
adequate oxygen delivery must be maintained
 1-2 L/min/m2
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

11.  Alpha Stat Vs. pH Stat
 Alpha Stat
Uncorrected (37°C) pH is kept at 7.40
with PCO2 at 40 mm Hg creating a
relative alkalosis at the patient arterial
body temperature.

12.  pH Stat
 Maintains a pH of 7.40 and PCO2 of 40 mm
Hg when corrected for body temperature,
typically requiring the addition of CO2 during
hypothermic CPB.
 Potent vasodilatory effect  increased
cerebral blood flow.
 May be advantageous in paediatric patients

13.  Anesthetic Depth
 Should be sufficient to
 Suppress hypertensive or tachycardic responses to surgical
stimuli
 Prevent awareness
 Prevent unconsciousness movement and respiration
 because hypothermia reduces the anesthetic requirement
they are most commonly used during the rewarming periods.

14.  Ventilation
 Should cease during total CPB
 During partial Bypass occasional ventilation wth
100% O2 may be needed.
 Urine production
 Sign of renal perfusion
 As a guide for fluid management
 >1ml/kg/hr should be maintained

15.  Fluid management
 Hemodilution
 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
used

16.  Ultrafiltration
 If adequate diuresis cannot be produced an
ultrafiltration device added to CPB circuit t remove
excess water.
 Heparin may be removed during ultrafiltration, so
anticoagulation must be monitored frequently.

17. Weaning from CPB

19.  Temperature
 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
 Cerebral hyperthermia
 Air embolism
 Rewarming may be enhanced
 By increasing blood flow
 Use of arterial vasodilators(SNP)

20.  Analysis and correlation of electrolyte , Acid
base balance and Oxygen transport status
 Acid base status must be optimised
 Acidosis
 Myocardial depressant
 Increased Pulmonary hypertension
 Metabolic acidosis due to inadequate tissue perfusion
 Inadequate perfusion flow
 A low hemoglobin level
 Inadequate oxygenation of blood

21.  Other causes
 DKA
 Renal Failure
 NaHCO3 can be used to treat the primary cause
 Serum K+ >4.0 meq/l to reduce the incidence f
arrhythmia
 Ca2
+
- to treat hypocalcemia and hyperkalemia
 Dose- 5-15 ml/kg,
can cause coronary spasm, augmentation of
reperfusion injury

22.  Hematocrit
 Must be adequate to provide oxyge carrying capacity
 HCt > 20% or greater is appropriate for termination of
bypass.
 Coagulation
 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

23.  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.

24.  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
overdistension.
 Inspired oxygen fraction should be 1.0

25.  Predictors
 Preoperative EF>40%
 Ongoing ischemia/Infarct in the pre-CPB period
 Prolonged CPB duration
 Inadequate Surgical Repair
 Incomplete coronary revascularisation
 Residual valvular regurgitation.
 Incomplete Myocardial Preservation
 Incomplete diastolic arrest
 Incomplete Cardioplegia

26.  Other Drugs / Infusions
 Volume expanders
 Vasopressors and inotropes
 Vasodilators
 Anesthetic State
 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
rewarming

27.  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
improves outcome.

28. Final Checklist for Terminating
CPB
 Confirm
 Ventilation – lungs ventilated with 100%
oxygen.
 The patient is sufficiently rewarmed.
 Complete de-airing done from heart/ grafts/
great vessels.
 Optimal metabolic condition.
 All equipment and drugs are ready.

29. 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
eject
 Preload- the amount of venous line occlusion is adjusted
carefully and maintain a certain optimal pre-
load(adequate cardiac output).

30.  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.

31.  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
CPB.
 The pump is stopped and both pump cannulas are
clamped fully

32. Immediately After Terminating
CPB
 Preload
 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

33.  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