1. A I I M S

2. Ritu Airan, Dr.Ujjwal Chowdhury, Dr.Balram Airan, Dr. Poonam Malhotra
Which is the most appropriate criterion for size selection of membrane oxygenator for patients with cyanotic congenital heart diseases: Body weight or high hematocrit?
Ritu Airan, Dr.Ujjwal Chowdhury,
Dr.Balram Airan, Dr. Poonam Malhotra

3. AIM
The primary purpose of the cardiovascular system is to ensure effective perfusion through the capillaries, with the majority of the vessels dealing with blood distribution belonging to the microvasculature

4. The principal haemodynamic parameters in some polycythaemias have been significantly correlated with increased :
haematocrit
blood viscosity
blood volume
Cardiac output diminishes and peripheral vascular resistance increases thereby reducing organ blood flow.

5. The sustained increase in red cell production in primary polycythaemia is known to elevate both haematocrit and blood viscosity levels.
When haematocrit exceeds 50%, blood viscosity increases steeply blood volume also increases in polycythaemia.
These increases are responsible for the principal manifestations of polycythaemic patients

7. Risk factors of high hematocrit
Hypoxia:
Hypoperfusion
Hemolysis

8. Indications Assesment for hypoxia an assessment of tissue oxygenation
PaO2O2 dissolved in arterial bloodTissue Oxygenation
PaO2 LowHypoxia
Even if PaO2 Normal,
Low TissueOxygenationHypoperfusionHyperviscosity

9. Background
Polycythemia (cyanotics)- decreased microcirculatory blood flow (hypoperfusion and hypoxia)
Determinants of blood viscosity
Aggregation and dispersion of cellular elements
Flow velocity (shear rate)
Temperature
Endothelial integrity
Plasma viscosity

10. Background (contd…)
Cyanotics- RBC (Biconcave microspherocytes) rigid, resist deformation in the microcirculation that has high shear stress
Cyanotics- increased viscosity, iron deficiency, polycythemia- decreased tissue perfusion reduced cerebral blood flow (hyperviscosity)

11. Background (contd…)
Surface area of gas exchange in oxygenator is (<10m2) which is considerably less than that in the lung (70m2)
Thicker blood films- longer exposure to oxygenating membrane
Thinner blood films- high flow rates per units area of membrane

12. Background (contd…)
Oxygen transfer in the membrane oxygenator obeys “Ficks Law Of Diffusion”
Oxygen transfer vary directly :
With total surface area of the membrane
Oxygen gradient developed across the membrane
Permeability of membrane material to oxygen

13. Background (contd…)
As the driving force for oxygen across the membrane is very high, the oxygenating capacity of a particular membrane is only dependent on the thickness of the blood film

14. References Annals of Internal Medicine 1988; 109.
Anesthesiology 2000; 92.
Journal of Cardiothoracic and Vascular Anesthesia 2002
Annals of Medicine 1993; 25.

15. Factors affecting oxygenation
FiO2 / sweep gas
Hematocrit
Flows
Hypothermia

16. Standardized protocol in AIIMS
Body weight
Oxygenator
Priming volume
8-12kg
Medtronic – minimax
800ml
12-30 kg
Terumo Sx-10
1000ml
>30 kg
Terumo SX-18
1800 ml

17. Patients and methods Number of patients : 132
Tetralogy of Fallot : n=104
Bi-directional Glenn: n=20
Total cavopulmonary connection: n=8
Age: 3 years – 50 years (mean±SD ±80.1)

18. Patients and methods (contd…)
Group I (n=62)
Cyanotic patients with preoperative hematocrit > 60%
Group II (n=70)
Cyanotic patients preoperative hematocrit <60%

19. Patients and methods (contd…)
In group I
Large surface oxygenator used
Hemodilution done
Withdrawal of perfusate
In group II
Regular oxygenator used

20. Patients and methods (contd…)
Blood samples monitored for
PO2
PCO2
Hemoglobin
Saturation
Acidosis
Observation for intraoperative hematuria

21. Results
Body weight (kg)
Oxygenators
Priming volume (ml)
Flow range (LPM)
No. of patients
Group I (n=62)
Group II (n=70)
8-12
Medtronic-Minimax
800
5+15* 20
12-30
Terumo SX-10
1000
20+8+2** 40
>30
Terumo SX-18
1800 12 10
*Used Terumo SX-10 ** Terumo Sx-18
During CPB, group II patients demonstrated normal PaO2 (223.8±20.3).
Despite recommended perfusion flow and gas-to-blood flow ratio, 32 patients of group I weighing between 20-30kg and >30kg with Terumo SX-10 and SX-18 oxygenators respectively demonstrated systemic arterial desaturation (91-98%) with intraoperative hematocrit ranging >35% and intraoperative hematuria (n=20).

22. Results (contd…)
Optimal intraoperative SaO2 >99% and oxygenation was achieved by further hemodilution in patients weighing >30kg and by withdrawal of prime to promote additional hemodilution in patients weighing between 12-30kg.
With this background, Terumo SX-10 was successfully used instead of Minimax in 15 of 20 patients weighing between 8kg-12kg
Terumo SX-18 was used instead of Terumo SX-10 in patients weighing between 20kg-30kg to achieve SaO2 between % with mean PaO ±20.30

23. Group comparison for PaO2
Variables
Group I
Group II
P value
PO2
162.16±50.86
234.8±20.30
0.001

24. Results (contd…) Variables Pre Post P value Group I 162.16±50.86
220.05±37.95
0.001
Group II
234.8±20.3
249.55±18.36
0.002

25. Trend SX-10 was used instead of minimax in patients weighing 8-12 kg
SX-18 was used instead of SX-10 in patients weighing kg
Withdrawal of perfusate to promote additional hemodilution was done to achieve improved gas efficiency and decrease hemolysis and hypoperfusion

26. ADVANTAGE OF HEMODILUTION
Lowers Blood Viscosity⇒decrease in Hematocrit.
Improves Microcirculation.
Counteracts the increased Viscosity by Hypothermia

27. Conclusions
Hemoconcentration causes marked reduction in blood flow through microcirculation
Greater risk of arterial desaturation in cyanotic patients with high hematocrit
Hence larger membrane surface oxygenator and hemodilution may be done for cyanotic patients with high hematocrit to ensure effective perfusion and oxygenation during Cardiopulmonary Bypass

28. Thank You