8.6.7 Technical aspects about ECC

 Apart from beating heart procedures, there are various technical means to reduce the inflammatory syndrome and coagulation changes triggered by ECC, but none of them can be eliminated. The clinical significance of these improvements is generally modest [6,15].

• No ECC; beating heart surgery (OPCAB) attenuates but does not suppress the release of inflammatory markers (C3a, C5a, TNF-alpha, IL-6, IL-8), as the ischaemic heart is a major source of cytokines. As   ECC effects depend largely on balance between release of pro-inflammatory and anti-inflammatory mediators (IL-10) [5], certain populations may benefit particularly from beating heart surgery because they show a dominant pro-inflammatory response, such as the elderly or those with left ventricular dysfunction [12]. In low-risk groups, SIRS-related complication rates are identical between surgery with and without ECC [8,9].
• Aspiration restriction; recovered blood contains air, cellular debris and activators of coagulation (TNF, thrombin, plasmin) or inflammation (interleukins, C3a, C5a). Aspirations are the main source of embolism, haemolysis, thrombocytopenia, coagulopathy and SIRS stimulation [13]. Disruption of coagulatory system is markedly reduced when aspirated blood is not recycled or is filtered in a CellSaver™ system, but these manoeuvres unfortunately remove platelets, proteins and coagulation factors [14].
• Restriction of circuit size; miniaturisation of circuits and removal of the cardiotomy reservoir minimises contact of blood with foreign surfaces and eliminates contact with air, thereby reducing the release of coagulation activators and inflammatory triggers [2].
• Biocompatibility of circuits; preheparinised circuits and circuits impregnated with polymers such as poly-2-methoxy-ethyl-acrylate inhibit  complement cascade and leukocyte activation, reduce platelet adhesiveness and coagulation factor adsorption [4]. Although they reduce pulmonary, renal and neurological complications, they have little clinical impact [7].
• Haemofiltration; reduces excess fluid specific to ECC and removes water-soluble inflammatory triggers. It reduces postoperative interstitial oedema, transfusion requirements, systemic inflammatory syndrome and multi-organ failure [3,10].
• Leukocyte filters; reducing leukocyte levels is beneficial especially for gas exchange, as lungs are the main site of leukocyte sequestration during ECC. Unfortunately, these filters do not prevent postoperative respiratory failure [1].
• Normothermia; maintaining temperature ≥ 34°C avoids coagulation alterations and inflammatory flare-up triggered by rewarming, but the ideal temperature for ECC has not yet been defined [11].

These improvements are likely to have an impact on postoperative complications in high-risk or complex procedures, but have modest influence on standard procedures in low-risk patients. Given the increased cost, these new technologies do not currently have a favourable cost/benefit ratio for routine use.

© CHASSOT PG, MARCUCCI Carlo, last update November 2019.

References

1. ASIMAKOPOULOS  G. The inflammatory response to CPB: the role of leukocyte filtration. Perfusion 2002; 17:7-10
2. BIANCARI F, RIMPILAINEN R. Meta-analysis of randomised trials comparing the effectiveness of miniaturised versus conventional cardiopulmonary bypass in adult cardiac surgery. Heart 2009; 95:964-9
3. BOODHWANI M, WILLIAMS K, BABAEV A, et al. Ultrafiltration reduces blood transfusion following cardiac surgery: a meta-analysis. Eur J Cardiothorac Surg 2006; 30:892-7
4. GUNAYDIN S, FARSAK B, KOKAKULAK M, et al. Clinical performance and biocompatibility of poly(2-methoxyethylacrylate)-coated extracorporeal circuits. Ann Thorac Surg 2002; 74:819-24
5. LAFFEY JG, Boylan JF, Cheng DC. The systemic inflammatory response to cardiac surgery: implications for the anesthesiologist. Anesthesiology 2002; 97: 215-52
6. MAHARAJ C, LAFFEY JG. New strategies to control the inflammatory response in cardiac surgery. Curr Opin Anesthesiol 2004; 17:35-48
7. MANGOUSH O, PURKAYASTHA S, HAJ-YAHIA S, et al. Heparin-bonded circuits versus nonheparin-bonded circuits: an evaluation of their effect on clinical outcomes. Eur J Cardiothorac Surg 2007; 31:1058-69
8. NATHOE HM, Van Dijk D, Jansen EWL, et al. A comparison of on-pump and off-pump coronary ECC in low-risk patients. N Engl J Med 2003; 348:394-402
9. PUSKAS JD, Williams WH, Duke PG, et al. Off-pump coronary artery bypass graTFing provides complete revascularization with reduced myocardial injury, transfusion requirements, and length of stay: A prospective randomized comparison of two-hundred unselected patients undergoing off-pump versus conventional coronary artery ECC. J Thorac Cardiovasc Surg 2003; 125:797-808
10. SEARLES  B, DARLING E. Ultrafiltration in cardiac surhery. In: MONGERO LB, BECK JR (eds). On bypass. Advanced perfusion techniques. Totowa (NJ, USA): Humana Press 2010, 193-210
11. SHANN   KG, LIKOSKY DS, MURKIN JM, et al. An evidence-based review of the practice of cardiopulmonary bypass in adults: A focus on neurologic injury, glycemic control, hemodilution, and the inflammatory response. J Thorac Cardiovasc Surg 2006; 132:283-90
12. SHARONY  R, Bizekis CS, Kanchuger M, et al. Off-pump coronary artery bypass graTFing reduces mortality and stroke in patients with atheromatous aortas: A case control study. Circulation 2003; 108 (suppl II):15-20
13. SNIECINSKI  RM, CHANDLER WL. Activation of the hemostatic system during cardiopulmonary bypass. Anesth Analg 2011; 113:1319-33
14. WANG G, BAINBRIDGE D, MARTIN J, et al. The efficacy of an intraoperative cell saver during cardiac surgery: a meta-analysis of randomized trials. Anesth Analg 2009; 109:320-30
15. WARREN OJ, WATRET AL, DE WIT KL, et al. The inflammatory response to cardiopulmonary bypass: Part 2 - Anti-inflammatory therapeutic strategies. J Cardiothorac Vasc Anesth 2009; 23: 384-93