ALBUMIN
Advantages in cardiac surgery
In surgical patients , fluid overload , as often caused by crystalloids , has been demonstrated to be an independent risk factor for morbidity and mortality and the benefits of the use of human albumin in cardiac surgery are discussed here
Alexey Schramko MD PhD Associate Professor of Anaesthesiology and Intensive Care , Department of Anaesthesiology and Intensive Care Medicine , Helsinki University Hospital , Finland
During cardiac surgery , large fluid transfers , priming of the cardiopulmonary bypass ( CPB ) circuit and blood and blood product transfusions , as well as long surgery durations , almost always lead to fluid overload . Despite the large amount of fluids administered , patients who have had CPB often have blood volume deficit because of fluid shift from the intra- to extravascular space due to systemic inflammatory response and damage of the endothelial glycocalix . 1 The fluid ‘ leakage ’ after cardiac surgery lasts for between several hours and several days . 2 Conversely , haemodynamics are often affected after cardiac surgery . The phenomenon of myocardial stunning is described widely and , in the early postoperative period , a significant number of patients need inotropic support and / or vasopressors because of the reversible acute heart failure . Additionally , the majority of postoperative patients need more intravascular volume for cardiac output optimisation .
Coagulation disturbances CPB impairs blood coagulation and , in some cases , renal function . There are several mechanisms of coagulation disturbance during CPB . The contact pathway is triggered when Factor XII , prekallikrein and high-molecular weight kininogen interface with the non-biological surfaces of the CPB circuit . 3 The extrinsic coagulation pathway is triggered when Factor VIIa complexes with tissue factor being expressed on leucocytes , platelets or exposed subendothelium within the vessel wall . Therefore , thrombin generation increases strongly . 4 By contrast , CPB initiation leads to the decrease of coagulation factors ( partially , due to haemodilution ) and increases the fibrinolytic activity . 5 The incidence of severe bleeding in cardiac surgery exceeds 10 %, and approximately 5 – 7 % of these patients experience blood loss in excess of 2l within the initial 24h following surgery . 6
After CPB , patients are predisposed to different complications , and finding optimal recovery conditions is challenging . The optimal volume resuscitation after CPB should be performed using small amounts of fluid , which remain for at least several hours intravascularly without undesirable side effects .
Benefits of albumin during cardiac surgery Different solutions , both crystalloids and colloids , have been used for volume replacement after cardiac surgery . A Cochrane systematic review did not find any difference in major outcomes when colloids were compared with crystalloids . 7 Crystalloids do not have significant side-effects , apart from haemodilution , but their volume effect is low ( about 20 %) and they remain in the intravascular space for a very short time , before shifting to the extravascular space . 8 This leads to the repetitive administration of crystalloids , which causes fluid overload and oedema . In surgical patients , fluid overload has been demonstrated to be an independent risk factor for morbidity and mortality , and the restriction of intraand postoperative fluids lead to dramatic outcome improvements . 9
Colloids stay longer ( for up to six hours ) in the intravascular space , and their volume effect is higher than those of crystalloids ( 80 – 300 %). However , the majority of colloid solutions with non-biological origin have been shown to have undesirable side effects . They could impair blood coagulation and renal function , which are already compromised after cardiac surgery .
Albumin is a colloid solution which does not have any clinically significant effect on blood coagulation apart from haemodilution . The volume effect of albumin solution is 80 – 100 % ( in the case of 4 % or 5 % solution ), but for hyperoncotic solutions it rises to up to 300 %. Therefore , using these solutions , it is possible to increase intravascular volume with small amounts ( 100 – 200ml ) of fluid . In critically ill patients , significantly less volume of 20 % albumin was effective for haemodynamics compared with 4 %– 5 % solution ; 10 additionally , patients who received 20 % albumin had less Na and Cl overload . The volume effect of albumin lasts for up to four hours , which is also desirable during and after cardiac surgery .
There are no large randomised controlled trials in cardiac surgery patients comparing albumin with any other fluid . The results from the ALBICS study in which 1250 patients will be randomised , are anticipated in 2020 . 11 Engelman et al reported that pre-operative hypoalbuminaemia (< 25g / l ) is an independent risk factor for multiple poor outcomes after cardiac surgery . 12 However , Fritz et al demonstrated that hypoalbuminemia predicts mortality after cardiac surgery even better than EUROscore . 13 In this study , cut-off for hypoalbuminaemia was 18g / l . Several studies have investigated the use of albumin for CPB priming . In a retrospective cohort of 19,578 patients undergoing CABG procedure , Sedrakyan et al demonstrated that albumin use was associated with reduced mortality ( OR = 0.8 , CI 0.67 – 0.96 ) compared with older generation colloids with non-biological origin . 14 Compared with crystalloids , less volume of priming is required in groups receiving albumin . Additionally , the use of albumin solution as prime fluid decreased the amount of postoperative
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