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Reducing The Hemodilutional Impact of The CPB Circuit

Reducing The Hemodilutional Impact of The CPB Circuit. By: Clint Robertson LP,CCP. Hemodilution Defined:. Medical Dictionary

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Reducing The Hemodilutional Impact of The CPB Circuit

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  1. Reducing The Hemodilutional Impact of The CPB Circuit By: Clint Robertson LP,CCP

  2. Hemodilution Defined: • Medical Dictionary • hemodilutionhe·mo·di·lu·tion (hē'mō-dī-lōō'shən, -dĭ-) n. An increase in the volume of plasma, resulting in a reduced concentration of red blood cells in blood. • Problems with excessive hemodiltion(Hct < 22%) • Increased morbidity and mortality • Contributes to an increase in acute renal injury and injury to other organs • Attributes to myocardial edema • Increase in infection rate and length of stay……due to increase in blood transfusions

  3. Role of hemodilutional anemia and transfusion during CPB in renal injury after coronary revascularization: • 1760 patients all isolated CABGS • Preoperative and post operative creatine levels were collected from two time periods (2003-2004 and 2008-2010). • Pump was always primed with plasmalyte mixed with 250ml of 20% mannitol • 17 subgroups of increasing lowest hematocrit were analyzed such that grp 1 included pts 1-352, grp 2 pts 89-440 and so on with the last subgroup being pts 1409-1760 (75% overlapping) • Measured • %^Cr=-peak post bypass percent change in creatine relative to pre CPB levels • %^Cr Cleareance= peak post CPB change relative to pre CPB in CR clearance levels • Renal injury is defined as %^Cr>50% ( includes acute renal failure pts) and ARF as per the current STS definition • Post bypass serum Cr must be both > 2 times its pre CPB value and > 2.1 mg/dl

  4. Demographics, risk factors, operative data:

  5. Cont…..

  6. Cont…. 1. Operative death occurred more frequently in ARF vs no ARF (p= .001)(ARF was significantly increased at Hct levels below 22%) 2. Increasing post CPB Cr levels were associated with systemically increasing length of hospital stay (p=.001) 3. Increase in Post CPB peak Cr levels increased(significantly greater with Hct values below 24%) both operative mortality and length of stay (p= .001). And these groups were also more likely to require hospital readmission (p=.02).

  7. Cont… • “Along with other reports highlighting hemodilutional effects on kidney and other vital organ function, our data raise further concerns regarding currently accepted CPB practice guidelines. These guidelines should be revisited with recognition that although there may be benefits to certain levels of hemodilution, evidence is gathering that the adverse effects of low hematocrits, below a certain threshold, may well outweigh its benefits”. • Robert H. Habib PhD

  8. Adverse effects of low hematocrit during CPB in the adult: Should current practice be changed? • 5000 consecutive adult cardiac surgery patients from a single institution (2000-2006) • Use of standard bypass techniques with 96% use of normothermia (body temp 35C-to 37C). • Arterial blood flow determined on the basis of cardiac index of 2.5 to 3.0 • Mean arterial pressure was maintained at greater than 60mmHg • Rolling decimal groups of 500 patients each (with 75% overlapping) of increasing lowest hematocrit values were used to determine hemodilution-outcome relationships.

  9. Demographics and risk factors: Included 3296 (66%) men and 1704 (34%) women. Of these 3800 underwent isolated CABG (76%) Lowest hematocrit on bypass (21.4+4.2%) Lowest hematocrit subgroups showed that older age, females, diabetes, history of CVA, preoperative renal failure, PVD, non CABG, reoperation, and increased time on bypass were all more frequent in more hemodiluted patients. Pre bypass hematocrit, and BSA were the main determinates of the nadir hematocrit on pump based on RBC mass balance in conjunction with a constant volume of crystalloid prime.

  10. Figure 1

  11. Cont…. • Increased operative mortality- (risk ratio: 0.863 p<.001) • Increase of prolong ICU stays- (risk ratio: 0.968 p<.001) • Greater likelihood of postoperative hospitalization of 9 or more days- (risk ratio: 0.954 p<.001)

  12. Cont… • The effects of hemodilution were similar for all CPB surgeries and isolated CABG and these increased sharply for a lowest hematocrit <22%, while they were unchanged for lowest hematocrit values >24%

  13. MYOCARDIAL EDEMA • The arterial input into the left ventricular myocardium branches into a dense microvascular exchange network (C) which in turn drains into several low resistance pathways. • Coronary sinus (CS) drains into RA and handles 75% of the total venous outflow. The remaining venous flow is by Thebesian Veins (TV) • Myocardial Fluid Balance: determined by the fluid filtration rate (Jv) out of the coronary microvasculature vessels into the cardiac interstitium and its removal rate from the interstitium.

  14. Edema cont..

  15. The effects of CPB with crystalloid and colloid hemodilution on myocardial extravascular water. • 50 mongrel dogs weighing 20-30kg separated in four groups • Median sternotomy • Cannulated through femoral artery and SVC and IVC • Biopsies taken from the left and right ventricles and the ventricular septum. • MEW- measured by Evans blue dye, tritiated method and also the thermal method • Groups 1-4 • Group 1: NO Hemodilution- pump primed with blood (Normal Hct and normal oncotic pressure) • Group 2: Effects of CPB with colloid hemodilution(Hct decreased but oncotic pressure normal) • Group 3: Normothermic crystalloid hemodilution( Both Hct and onctoic pressure decreased) Hct 18% • Group 4: CPB with crystalloid hemodilution and hypothermia to 22 C

  16. Edema cont. • Table 1 1. Grps 1 and 2: No significant difference as compared to baseline values. 2. Grps 3 and 4: Showed a significant increase in total water content as compared to baseline with a p<.001

  17. Edema cont… Grp1: The weight dry ratio was incr by only 5.7% Grp 2: (Normal Oncotic pressure with decrHct) Weight dry ratio was 5.4% Grp 3. And 4: (Crystalloid hemodilution….decrease in Hct (18%) and Oncotic pressure) resulted in a much greater and statistically significant increase in myocardial extravascular water content p <.01. The weight dry ratios were increased by 30.3% and 37.4% respectively

  18. 1. At 15mmHg LAP Grp 3 & 4 (crystalloid hemodilution with decreased Hct and Oncotic presure) generated a stroke work index 40+ 8% reduced from controls p<.05. • 2. Grp 1 (Hematocrit and oncotic pressures normal) showed a 10+ 7% reduction in stroke work index • 3. Grp2 (Oncotic pressure is nor- mal bur hematocrit decreased to 18%) resulted in only a 17+ 12% reduction of stroke work index at comparable left atrial pressures.

  19. Colloid Hemodilution HCT 18% (Grp 2) Crystalloid hemodilution HCT 18% (Grp 3 & 4)

  20. How Can We Help To Minimize The Problem of Excessive Hemodilution: • Minimizing the circuitry • Vacuum assisted venous return • Retrograde Autologous Priming • Prescriptive oxygenation • Colloid vs Crystalloid Prime • Microplegia

  21. VAVD 357 pts undergoing valve surgery separated into 3 groups Grp1: 83 pts using VAVD with conventional sized tubing (drained venous line) Grp2:150 pts using VAVD with reduction in tubing (20.4 ft and drained venous line) Grp3: 124 pts using conventional gravity drainage

  22. VAVD CONT… After adjusting for age, blood volume, full sternotomy, mitral valves, and propensity scores………. RBC’S transfusion: VAVR GRP 1 55% lower in VAVR grp 1 (with no reduction in tubing length) as compared to gravity drainage VAVR GRP 2 88% lower in VAVR grp 2 (20.4 ft reduction in tubing) as compared to gravity drainage

  23. Retrograde Autologous Priming • (23.4%+ 3.4% vs 21.2%+ 2.6%) • p = .045

  24. RAP cont… • 1. 24 hr chest tube drainage was also significantly less in the RAP grp/ as well as overall transfusion rate as compared to the groups with NO RAP

  25. Microplegia: 1980 CABG pts using standard 8:1 Blood CPG v/s 1980 pts using microplegia (Quest MPS system) 66 blood: 1 crystalloid. 90% of patients in both grps received cold intermittent antegrade CPG. Few pts received continuous retrograde CPG with intermittent antegrade infusions. These were reserved for reoperative CABG, severe left main disease, and patients with severe left ventricular dysfunction. Grps were similar in method, direction, and temperture of administered CPG.

  26. Microplegia cont… • Prevalence of LCOS was significantly lower in the microplegiagrp (2.7%) compared with standard CPG (5%) • Length of hospital stay and duration of ventilator times were also significantly less in the microplegiagrp. • Microplegia was associated with significantly-lower prevalence of post op IABP (2.5%) compared to the standard 8:1 grp (4%). • Pts with LCOS going into surgery were less likely to require an IABP (7.4%) in the microplegiagrp as compared to (22.4%) in the standard CPG grp

  27. Conclusion: • The negative effects of both hemodilutional anemia from the CPB circuit and cardiac edema are well documented. By using the previously mentioned modalities we can safely and effectively reduce these harmful effects and help to give our patients the best possible outcome.

  28. Thank You

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