in blood volume and an increase in extracellular volume of 3l , which peaked 4 hours post-surgery . Moreover , post-operative capillary leakage increased by 5.4 % of body weight over the same time frame . 6
Interestingly , the use of albumin as a priming fluid has been shown to reduce postoperative bleeding . In one study , 377 patients were assigned to either 20mg / kg Ringer ’ s lactate solution with 0.75mg / kg albumin 20 % or Ringer ’ s lactate alone . The results demonstrated a significant reduction in terms of re-operations for bleeding ( p = 0.033 ) and a lower mean number of blood derivatives transferred per patient in those given albumins . 7 In addition , the use of human albumin as a priming fluid has several other advantages : it helps to preserve oncotic pressure ; prevents fibrinogen and platelet adhesion ; and exerts a protective effect on the endothelial glycocalyx . 8 All of these benefits were confirmed in a meta-analysis of trials with both adults and pediatric patients undergoing bypass grafting and in which albumin was compared to crystalloids . The analysis revealed how albumin exerted significantly favorable effects during bypass on platelet count , colloid oncotic pressure , positive fluid balance as well as postoperative oncotic pressure . 9
These observations highlight the importance of how optimal volume resuscitation after CPB should be achieved using small amounts of fluid that remain for at least several hours within the intravascular system and without undesirable side effects .
Selection of fluid after cardiac surgery : crystalloids or colloids ? Both crystalloids and colloids have been used for volume replacement after cardiac surgery although a Cochrane systematic review did not find any difference in major outcomes when colloids have been compared to crystalloids . 10 Nonetheless , while overall outcomes were found to be similar , there are some notable disadvantages from using crystalloids . For example , the hemodilution effect of crystalloids reduces intravascular oncotic pressure and the volume expansion effect of crystalloids is low ( typically 20 %) and such fluids remain within the intravascular space for a very short period time , before shifting to the extravascular space . While this can be resolved by the administration of further fluids there is a commensurate increased the risk of fluid overload and edema that in surgical patients , are both known to be associated with poor survival and a higher incidence of complications . 11 In contrast , colloids are retained within the intravascular space for up to 6 hours and have a higher volume effect hence reducing the risk of edema . For example , the natural colloid albumin , does not have any clinically significant effect on blood coagulation and the volume effect of 4 – 5 % solutions are approximately 80 % of the administered volume and this increases considerably for hyperoncotic solutions , e . g ., 210 % for a 20 % albumin and 260 % for a 25 % albumin . 12 Thus in practice , with hyper-oncotic albumin , it is possible to increase the intravascular volume with small amounts , e . g ., 100 – 200ml of fluid . This was shown in a randomized trial of critically ill patients within an intensive care setting who received either albumin 20 % or 4 – 5 %. The study revealed how those who received 20 % albumin solution required two-thirds less resuscitation fluid than the lower strength albumin and also had less sodium and chloride overload . 13
Albumin verses artificial colloids While there are potential benefits from using colloids over crystalloids , not all colloids are the same and studies have underlined important differences between albumin and non-biological colloids with the latter having a more undesirable safety profile including impairment of blood coagulation compared to albumin . 14 In a 2012 metaanalysis of the non-biological colloid , hydroxyethyl starch ( HES ) versus albumin on postoperative blood loss in adult CPB surgery , it was shown that HES increased postoperative blood loss by 33.3 % compared with albumin . 15 The analysis also revealed how in comparison with albumin , the use of HES doubled the risk of reoperation for bleeding , increased the need for red blood cell transfusion after CPB by 28.4 %, and the use of platelets by 29.8 %. The authors suggested that albumin was the most appropriate control fluid because it is the normal colloid present in the circulation and does not exhibit adverse effects on coagulation . These observations are aligned with the results of an earlier 2001 meta-analysis of 16 trials involving 653 patients which also concluded that postoperative blood loss was significantly lower in cardiopulmonary bypass patients receiving albumin compared to HES . 16
Even during the perioperative period , synthetic colloid use has been found to increase the need for renal replacement therapy . In 2013 , in a prospective cohort study involving more than 6000 patients that compared 6 % HES 130 / 0.4 ( n = 2137 ), 4 % gelatin ( n = 2324 ) and crystalloids ( n = 2017 ) in cardiac surgery , the authors examined the use of renal replacement therapy ( RRT ) as the primary endpoint . The need for RRT was significantly greater with HES ( odds ratio , OR = 2.29 , 95 % CI 1.47 – 3.60 ) and gelatin ( OR = 2.75 ) compared with crystalloids although the time to vasoactive drug withdrawal , the return to normal of both blood lactate levels , and mean arterial pressure did not differ between the three groups . 17 There are also some data to suggest that the use of albumin as a volume expander after bypass graft surgery ,
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