Choice of resuscitation fluid for critically ill patients
The management of volume status in critically ill patients is dynamic and requires frequent monitoring and high clinical acumen in selecting the best fluid for resuscitation
Jianguo Li MD Department of Critical Care Medicine , Zhongnan Hospital of Wuhan University , China
Fluid resuscitation is important in critically ill patients , and its main purpose is to correct absolute or relative blood volume deficiencies and reverse circulatory shock . In recent years , there has been a consensus on the volume of resuscitation fluid , that is , active fluid resuscitation should be carried out in the early stage , and infusions should be decreased in a timely manner to reduce fluid accumulation and avoid volume overload . 1 The choice of resuscitation fluid is also critical , and it should have the following characteristics 2 , 3 :
• It can produce stable and predictable blood volume expansion effects without increasing tissue oedema ;
• Its chemical composition is as close as possible to extracellular fluid ;
• It can be metabolised and completely eliminated by the body without accumulation in the tissues ;
• It has no metabolic or other systemic adverse effects ;
• It has a good cost – benefit ratio . As yet , no resuscitation fluid is deemed ideal .
Clinicians should consider the following aspects when selecting fluids for resuscitation .
Crystalloid or colloid ? Crystalloids are the most commonly used fluids in the ICU and are mainly ionic solutions that can penetrate capillaries . Isotonic crystalloids include physiological saline ( 0.9 % sodium chloride ), lactated Ringer ’ s solution , and acetate Ringer ’ s solution , etc ( see Table 1 ). Colloids contain macromolecular substances that cannot penetrate healthy capillary membranes , and include albumin , and also semi- synthetic molecules ( hydroxyethyl starch ( HES ), gelatins , and dextran ). According to the Starling principle , the expansion effect of crystalloids for fluid resuscitation is much lower than that of colloids . However , recent studies have confirmed that the amount of colloid required to meet the same resuscitation target is slightly less than that for crystalloids , and the ratio between the two is estimated to be approximately 1:1.5 ( 1.36 – 1.65 ). 4
Many studies have compared the effects of crystalloids and colloids on the clinical outcomes of critically ill patients . A large Cochrane review included 69 studies ( 65 randomised controlled trials ( RCTs ) and four quasi-RCTs ) involving a total of 30,020 critically ill patients requiring fluid resuscitation . In general , there were no significant differences in clinical outcomes such as mortality and side effects with colloids and crystalloids ( including semi-synthetic colloids and natural colloids ). 5
In view of the fact that colloid resuscitation has no particular advantage in improving the clinical outcome and safety of patients compared with crystalloids , and alongside cost issues , current Suviving Sepsis Campaign guidelines recommend the use of crystalloids as first-line resuscitation in septic shock . 1 , 6
Natural or semi-synthetic colloids ? Human serum albumin is a natural colloid , and hydroxyethyl starch ( HES ), gelatins , or dextran are semi-synthetic colloids . Albumin is synthesised by
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