By SAMIA I. SHARAF M.D . Professor Of Anaesthesia Ain Shams University

1. Cardiopulmonary Bypass In Pediatric Cardiac Surgery By SAMIA I. SHARAF M.D . Professor Of Anaesthesia Ain Shams University

2. Cardiopulmonary Bypass For Pediatric Cardiac Surgery Rational for use of cardiopulmonary bypass in cardiac surgery ** Provides clear surgical field for cardiac manipulations during open heart surgery** Provides enough flow to maintain sufficient tissue perfusion

3. Components Of Cardiopulmonary Bypass

4. Cardiopulmonary Bypass Circuit PATIENT Arterial cannula • Main pump • Roller • Centrifuge Venous cannula Venous reservoir Cardiotomy circuit for blood suction • oxygenator • Membrane • Flow rate • 0-200ml • HCT 15-40% • Temp. 10-38c • Heat exchange Accessory pump filter Left vent Accessory pump

5. Arterial cannulae Pediatric straight tip with ¼ inch connection site vented Non vented Curved tip cannulae

6. Venous Cannulae Right angle metal tip cannulae

7. Thus, cannulation for cardiopulmonary bypass should provide: • Adequate flow. • Unobstructed drainage. • Perfusion and drainage of all organs. • Unobstructed field.

8. Venting : Left ventricular venting is necessary in infants and neonates because of their greater bronchial collateral flow ( up to 30% of neonatal circulating blood volume may be held within suction system ) . Pediatric Left Heart Catheter

9. Child Nomogram

13. Physiology Of Cardiopulmonary Bypass PRIMING : NEONATES : Large prime/ blood volume ratio > 200 – 300 % of blood volume PEDIATRIC : Total prime volume 500 – 1200 ml Priming Should Be A Balanced Electrolyte Solution

14. Constituents Of Prime For Pediatric Extracorporeal Circuit

15. Hemodilution : • Due to priming volume • Priming volume depends on size of venous reservoir , oxygenator and tubing • Degree of hemodilution (predicted HCT on bypass ) is a matter of prime volume , patient blood volume and HCT • HCT below < 20-25% on bypass consider addition of blood to bypass circuit

16. N.B: PHCT = PtBV x PtHCT PtBV + PrimeBV PHCT= Predicted Pump HCT PT. BV = Patient Calculated Blood Volume PT.HCT = Patient HCT PRIME BV = Total Priming Volume The Amount Of Blood Required To Be Added To The Prime Is Calculated As : Prime RBC Volume = ( On Bypass HCT) X ( Pt.BV + Prime BV ) – ( Pt. RBC Volume )

17. Effect Of Hemodilution • systemic vascular resistance improve blood flow through microcirculation in presence of hypothermia • Loss of oncotic activity tissue oedema • Hemodilution of coagulation factors • Exageratesrelease of stress hormones, complement and white cell and platelet activation

18. Pump Flow RateBased on body weight and maintenance efficient organ perfusion *Venous saturation *Arterial blood gases *Acid base base balance Pump Flow Rate >

19. Determinants of optimum flow rate is based on systemic oxygenation & acid base balance.These data are less useful during deep hypothermia in which metabolism is severely reduced and cerebral autoregulation is lost

20. * Heparin : 300 – 400 u/kg* ACT 480 seconds* Plasma Heparin concentration Anticoagulation : >

21. HypothermiaNecessary to tolerate reduction of flow rate on CPB

22. (1) metabolic rate & O2 consumption lead to tolearance of low flow rate of CPB without affecting global oxygenation (2) Preserve high energy phosphate(3) calcium entery into cell & decrease cell membrane permeability Protective effect of hypothermia :

23. 25-30c Older children Repair of VSD, F4,SAM Low flow rate Neonate Temp. below 18c Complex surgery Low flow rate Neonate Cannulae off field Complex surgery ( aortic arch ) Excellent surgical condition Older children Simple cases Need high flow rate and HCT

25. Is Anesthetist Presence Is Required During CPBIs It Lunch Break For Us ?

26. 1. Traditional anaesthesia goals2. Monitoring 3. Participation in risk management4. Weaning from CPB Role Of Anaesthetist During CPB

27. I. Traditional anaesthetic goals • Hypnosis • Analgesia • Amensia • Muscle relaxation

28. Effects of CPB on anaesthetic agents Pharmacokinetics of drugs change due to : • Hemodilution • perfusion to peripheral tissue • Hypothermia

29. Pharmacokinetic changes during CPB

30. Effects Of CPB On Specific Anaesthetic Agents Opioids : • High dose opioids : * Showed flat plasma drug level during CPB opioidtisue level is constant at onset of bypass * Need no opioid supplement during CPB • Opioid infusion : Drug level along course of CPB and during rewarming • Fast track technique & warm CPB: • Normothermia , high flow rate , low doses of opioids have dilutional effect on drug level • Require opioid supplementation

31. Amensic Agents • Rewarming period after hypothermia is time of recall • Recall is uncommon at teperature below 30 c • Supplement of benzodiazepines ( midazolam ) is required • Dose of 0.1 – 0.15 mg/kg during rewarming

32. Neuromuscular Blocking Agents • Drug level is affected by hemodilution at onset of CPB because of : • Water soluble drugs • Ionized • Not bound to plasma proteins • Require addition doses at onset of CPB

33. Inhalational agents • Lesser influence of CPB on uptake, distribution & elimination

34. Check List For Initiation Of CPB ACT adequately elevated Observe face and neck for colour and venous engorgement Ventilation continued till stable flow rate Turn off ventilation vaporizers and I.V infusion when stable flow rate

36. MONITORING OF PATIENT Blood pressure Urine output ECG BIS Cerebral monitoring Blood glucose level Anticoagulation

37. Participation In Risk Management During CPB Patient movement during CPB Help in urgent seinarioe.g pump circuit failure and o2 failure which requires immediate separation of CPB Acute dissection of aorta from cannulation Massive air embolism

38. Weaning From CPB • When to wean ?? • Surgical repair is complete • Patient temperature is 37c • Balance of physiologic parameters • ** Correct acidosis • ** K+ • ** Correct ca++ • ** HCT 25-30 % OR preop. Level

39. How To Wean From CPB Ask perfusionist about fluid balance i.ehow much blood is left in CPB Ask perfusionist about venous oxygen saturation Start lung ventilation Reduce flow rate of CPB gradually Fill the heart Off bypass Observe and optimize hemodynamics Reverse Heparin & remove the cannulae Start the hemostasis

40. Factors That May Result In Failure To Wean From CPB

41. PATHOPHYSIOLOGIC EFFECT OF CPB ON BODY ORGANS

42. Myocardial effect Renal Dysfunction Systemic & pul. Hypertension Pulmonary endothelial damage (Pul.Dysfunction) Postop. Bleeding Pul.Vascular reactivity

43. Strategies For Optimizing The Use Of CPB In Neonates , Infants & Pediatrics • (1) Identification of patients at risk of mortality from bypass • Patients requiring surgery in the 1st. Month are at risk • Small size infant (1800 grams) • Infants with reduced LV function • Multiple congenital anomalies with CHD

44. (2) Use of methyl predinsolone(3) Leukocyte depleted blood in the circuit and leukocyticblood filter(4) Minimize CPB circuit : low volume oxygenator, short tubes , and small diameter tubes.(5) Vaccum assisted venous drainage(6) Bicompatible coated circuit (Heparin coated circuit)

45. ULTRAFILTRATION It is a hemofiltration technique that passes blood through a semipermeable membrane filter and using a transmembrane pressure gradient , remove water , electrolytes and other substances of small molecular size .

46. Types Of Ultrafiltration • Conventional ultrafiltration • Removal of fluids during bypass • Difficult in neonates because of small circuit • Modified ultrafiltration ( MUF) • Effective method in neonates and sick infants • Performed after CPB completion • Remove fluid rich in inflammatory mediators.

47. Presence of anesthetist is essential during CPB It is not a lunch break Someone has to be there