This document outlines the key steps and considerations for safely conducting cardio-pulmonary bypass (CPB). It discusses monitoring patient physiology and equipment, priming the circuit, initiating and managing bypass, and post-bypass activities. Conducting CPB requires a multidisciplinary team with effective communication. Patient temperature, blood flow rates, oxygen delivery and other variables must be carefully monitored to ensure adequate tissue perfusion. Thorough documentation in perfusion records is also important. Protocols and checklists can help standardize the process while still allowing for clinical judgment. The overall goal is to support the patient's cardiovascular and respiratory functions during surgery.

1. Conduct of cardio
pulmonary bypass

2. What constitutes safe conduct of
CPB?
 Monitoring basic physiologic functions
 Monitoring CPB devices and circuit performance
 Activities before and after bypass.
 Selection of appropriate equipment.
 Assembly and priming of the system.
 Completion of checklists.
 Resumption of normal cardiopulmonary function
 Disposition of residual perfusate
 Initiation and reversal of systemic
anticoagulation

3. Personnel involved
The conduct of CPB involves personnel
from different disciplines and background
who must function together as a team.
1) Surgery
2) Anesthesiology
3) Perfusion
4) Nursing
Effective communication is important for
successful outcome.

4. Circuit
 Chart review and selection of equipment.
 Maintenance of CPB console and heater
cooler unit.
 Preventive maintenance schedule.

5. Assembly
 Check sterile packaging for integrity
 Aseptic techniques
 Preassembled pumps
 Check for water leaks and integrity
 Some centers fallow Co2 flushing of the
circuit

6. priming
 Balanced electrolyte solution and additives
excluding blood products.
 Prebypass filter may be used(.2 to 5 Micro
m pore size)
 Warm the perfusate to 35 degree C
 Check for the integrity of the circuit
 Blood products according to requirement.

7. Setting occlusion and verifying
accuracy of pump flow
 Proper blood flow direction must be verified by
tracing the CPB circuit to the operative field and
back.
 A small gap (1/8 to 1/16”) should exist b/w the
tubing and roller pump back plate.
 Tubing should not ride up or down with pump
housing.
 The roller pump tube resembles ‘U’ shape.
 Set occlusion for arterial,suction,vent and
cardioplegia pumps.

8. Positioning the pump and
arrangement of lines
 The heart lung machine console is
positioned near the operating table.
 Parallel to operating table and opposite to
primary surgeon
 Position should be such that it minimizes
tubing length.
 Passing the tubes.
 Sufficient tubing length to enable CPB
component change out if required.

9. Pre-CPB check list
 Do list
 Done list
 Challenge and response method (two
persons required)

10. Initiation of bypass
 Fluid balance and circuit priming volume
 Retrograde autologous priming
 Vaccum assisted venous drainage
 Estimation of fluid balance

11. Check List for Going on Bypass:
HAD2SUE Remember this mnemonic. Say it often. Avoid killing patient by using it.
Heparin: Always give prior to bypass.
ACT: Always check before going on bypass (450 seconds)
Drugs: Do you need anything (Non depolarizing neuromuscular blocker).
Drips: Turn off the inotropes etc.
Swan: Pull the PA catheter back 5 cm to avoid pulmonary arterial occlusion/rupture.
Urine: Account for bypass urine
Emboli: Check the Arterial cannula for bubbles.

12. Establish extracorporeal flow
 CPB begins by removing the clamps and
activating the systemic pump speed
control.
 Start speed control first to avoid
exsanguinations in the event of pump
malfunction.
 Flow indices are 2.2 to 2.4lt/min/mtsq or
50 to 65 ml/kg/min
 Higher indices for pedeatrics.
 Open the arteial filter purge line.

13. Management of gas flow
 The gas flow to the oxygenator is started
before going on CPB (after cannulation)
 Observe the color of blood
 The gas-to-blood flow ratio is .5 to 1 :1
 Inhalational anesthetics may be delivered
to the patient through the oxygenator.
 This facilitates systemic blood pressure
control and maintaining anesthesia.

14. Placement of vents and
cardioplegia cannulae
 All vents should be tested before use.
 Perfusionist should be notified when vents
are placed
 Discontinuation should also be
communicated.

15. Monitoring during bypass
physiologic variables
Direct external control other variables
determined by pt
response

16. Monitoring during bypass contd.,
 Direct ext control
1. Systemic blood flow
2. Venous pressures
3. Hct and composition
of priming fluid
4. Arterial blood o2 and
co2 and temp of
perfusate and pt.
 Variables
determined by
patients.
1. SVR 2. total body o2
consumtion.
3. Mixed venous o2
4. Lactic acedemia and
ph.
5. Organ blood flow
and organ function.

17. Circuit variables
 Systemic blood flow
 Venous blood drainage
 Venous reservoir volume should be 25% of
systemic blood flow(15 seconds reaction time)
 Perfusionist should anticipate surgeons needs.
 Establish a pattern of continuous scanning of
cpb function and monitors.
 Develop a “Curious and suspicious” attitude
during CPB.

18. Physiologic response
 No uniformly accepted standards for either
CPB systemic blood flow rate or perfusion
pressure.
 Any discussion to be based on oxygen
consumption, blood flow distribution and
autoregulatory capability of specific
vascular beds.

19. Determinants of Vo2
 Vo2 is primarily a function age, size (bsa)
and temperature.
 In newborns Vo2 in proportion to body wt
is approx twice that of adult(8 vs
4ml/kg/min)
 It rises to 9 to 10ml/kg over first two
months.
 Than it exponentially decreases with age.

20. Determinants of Vo2
 With temperature the relation is nonlinear.
 Vo2 approaches 10 to 15% of normal
value at 15 deg C.
 Decline in Vo2 with temp is not the same
in all organs.
 The duration of “safe” circulatory arrest
time varies with organs.

21. Effective blood flow
 During CPB effective blood flow is blood flow
from oxygenator that actually results in tissue
perfusion.
 In this context all physiologic and anatomic
shunting of arterialized blood does not contribute
to effective flow.
 For ex bronchail flow (2 to 4%),collaterals.
 Vents are common source of loss of effective
flow.
 Microcirculation if not perfused homogenously
results in loss of effective flow.

22. Organ autoregulation
 Despite non pulsatile flow,hemodilution
and hypothermia autoregulation is
preserved in some organs.
 Cerebral perfusion studies have proved
this.
 The effect of cpb on autoregulation in
other organs is less documented.

23. AUTOREGULATION
 Cerebral blood auto regulated if MAP > 50
mmHg at normal temp.
 Cerebral blood flow is still auto regulated
at MAP < 50mmHg if temp is reduced.
 This is due to reduced brain metabolic
rate

24. AUTOREGULATION AND
TEMPARETURE
 In patients with moderate hypothermia if
MAP > 40 mmHg auto regulation is
preserved
 This is true only for patients with no
cerebral vascular disease
 Auto regulation is lost at temperatures
less than 22 deg C

25. Predicted minimum pump flow rates
Temperature(deg
c)
CMRO2(ml/100g
m/min)
Predicted
MPFR(ml/kg/min)
37 1.48 70
32 0.823 56
30 0.654 44
28 0.513 34
25 0.362 24
18 0.159 11
15 0.112 08

26. Monitoring perfusion adequecy
 Systemic measurements that indicates
adequecy of perfusion are
1) Svo2
2) Ph
3) lactate concentration

27. Venous Saturation
 High Svo2 does not mean adequate
perfusion
 Low Svo2 indicates inadequate tissue
perfusion.

28. Relation b/w perfusion and O2
consumption
 Oxygen consumption plateauing
 Vo2 optimization.
Disadvantage:
 Vo2 is calculated for awake or
anesthetized prebypass volume.
 During CPB with hypothermia baseline
Vo2 would yield excess perfusion during
CPB.

29. Study shows.,
 During cooling no relation b/w Vo2 and
MAP or peripheral vascular reistance.
 During rewarming these parameters are
inversley related.
Conclusion:
Higher systemic flows recommended
during rewarming phase of CPB.
 Optimization of Vo2 during CPB may
provide the best means of assessing
adequecy.

30. Flow recommendations
 What is the ideal flow during CPB?
1. In adults at normothermia acidosis and
lactate production are seen with flows
less than 1.6lt/min/mtsq or 50ml/kg/min.
2. In adult 1.8 to 2.2 lt/min/mtsq is
recommended at temp above 28 deg C
3. In infants and children a higher flows
above 2.5lt/min/mtsq is recommended.

31. Perfusion pressure and vascular
resistance
 Blood flow is given more importance than
perfusion pressure as a guide to
adequecy of perfusion during CPB
especially with hemodiltuion.
 With crystalloid prime there is a drop in
SVR at the onset of CPB due to
hemodilution.
 SVR increases over time during CPB.

32. Monitoring during CPB
 PA and LA pressure monitoring:
 Has more importance in pre and post Cpb
intervals.
 During cpb and off cpb they give information
regarding LV filling
 LA and PA should be zero during cpb.
 Monitoring prevents overdistension of LV
eg: chronic lung diseases or cyanotic chd
with increased bronchial flow can distend LV if
venting is inadequate.
Aortic valve insuffieciency.

33. CVP measurement
 CVP should be zero or negative during
CPB.
 Increased CVP indicates impaired venous
drainage
 Major adverse effect of elevated venous
pressure during CPB is reduction in
effective perfusion pressure for critical
organs.

34. Cardiovascular monitors
 TEE
 ECG
 Direct observation of heart

35. Neurological monitoring
 Transcranial doppler
 NIRS
 Reflectance spectrometry
 EEG monitoring
 Sensory Evoked potentials
 Hemodilution,hypothermia, anesthesia and
pulsatility changes makes CNS interpretation
difficult

36. Near Infrared Spectroscopy (NIRS)
 Used to monitor tissue O2 saturation in
cerebral and in mixed somatic tissues.
 Uses a noninvasive optical technique.
 A pad with a paired emitter and detector is
attached to the forehead.
 It monitors the wavelength for saturated
and desaturated Hb.
 A computerised algorithm specific to adult
or pediatric patient interprets data.

37. Contd.,
 The number thus got reflects the cerebral
venous O2 saturation at a particular depth.
 NIRS reads continuously and is more
representative of regional cerebral mixed
venous O2 saturation index (rSO2i).
 Correlates with clinical data
 In pediatric NIRS is evaluated for flank
muscle and tissue bed perfusion.

38. NIRS for splanchnic tissues
 During adequate systemic tissue O2
delivery, somatic rSO2i is 10% to 20%
higher than brain rSO2i.
 When systemic perfusion is decreased,
blood flow to the brain within limits is
protected by autoregulation,
 A reduction of tissue rSO2i difference to
less than 10% indicates desaturation of
somatic tissues.

39. Temperature monitoring
 Temperature measurement is a core
physiologic monitor during CPB.
 Temperature can be measure at
nasopharngeal,oesophagial,tracheal,mixe
d venous blood,arterial blood,bladder
urine rectal,tympanic membrane and great
toe.
 Measured during cooling and rewarming
state.

40. Temperature monitoring contd.,
 Calorie loss – 238kcal – 30deg c(cooling)
 Calorie gain – 160kcal- 37deg c (rewarm)
 Net loss 238-160 = 78kcal(1.5hrs of basal
metabolic heat output)
 Net loss results in rebound hypothermia or
after drop.
 Other factors :- a) vasodilators
b) gradient

41. Urine output and renal function
 Urine output not related to post op renal
failure.
 Normal urine output during cpb is .5 to 1
ml/kg/hr.
 Loop or osmotic diuretics (or both) are
useful during CPB.
 Catheter patency must be ensured.

42. Equipment monitoring during CPB
 Oxygenator function
 The single most important equipment in
CPB.
 Oxygenators are subjected to stringent
quality control.
 Oxygenation is the single best monitor of
oxygenator
 Adequacy of oxygenation must be
determined early and throughout cpb.
 Po2 to be maintained b/w 140 to 180
mmhg

43. Cardioplegia delivery
 Flow pressure and temperature should be
monitored.
 Aortic root pressure to be monitored.
 Coronary ostia and retrograde pressure to
be monitored to avoid tissue damage.
 Myocardial and cardioplegia temperatures
are usefull.

44. Fluid management
 Supplemental fluid administration is needed for
1) extra vascular blood loss
2) fluid shifts
3) urine output
 The choice of fluid administration is governed by
the stage of operation.
 MUf and CUF volume to be monitored.
 Blood administration to be double checked for
group and id no.

45. Circuit alarms
 Level sensor
 Air Bubble detector.
 Pressure cut off system.
 Alarms and safety devices are not a
substitute for an alert perfusionist.

46. Perfusion record
 Record keeping provides permanent
documentation.
 Should contain all relevant information reg
patient,diagnosis,surgery,equipment
used,drugs,fluids and blood products.
 Perfusion record forms a larger database.
 Important document if legal proceedings arise.
 A complete and legible record is vital.
 Entry to be made every time when a change is
made in perfusion controls.

47. Perfusion record contd.,
 Use of 24 hour time(“military time”)
entries is recommended.
 Blood gas and lab values should be
recorded at the time of drawing sample.
 All fluids added to the cpb circuit should
be recorded at the time they are added.
 Medications should be noted.

48. communication
 CPB depends on close coordination of
activities by all team members.
 Effective communication provides a
means to facilitate coordination.
 All instructions and announcement should
be fallowed by acknowledgment from the
person to whom it was directed.
 This minimizes errors of omission.

49. Post CPB activities
 Transfusion of residual perfusate
 Check arterial cannula for residual air
before transfusion.
 Pump suckers to be turned off when
protamine administration begins.
 Circuit disassembly and recovery of
residual perfusate should not be
undertaken until the patient is
heamodynamically stable.

50. Perfusion protocols,guidelines and
standards.
 Protocols and guidelines are no substitute for
commonsense and experience.
 They are useful in safe conduct of CPB.
 The institutional protocol outlines the selection of
circuit components according to pt. size and
diagnosis.
 Protocols are customised to surgeon’s needs or
procedural need.
 Protocols should be developed with inputs from
all team members and should be periodically
reviewed and updated.