Colloids or crystalloids for fluid management : pros and cons
Satisfactory fluid management is the foundation of hemodynamic control and this can be achieved through the use of either colloids or crystalloids , both of which have their own merits
Volume expanders are a class of intravenous fluids that are administered in fluid resuscitation ( volume replacement therapy ). The immediate aim of fluid resuscitation is to swiftly replace circulating volume to restore organ perfusion and continue tissue oxygenation in cases of hypovolemia . 1 The major causes of hypovolemia are : dehydration ( through , for example , vomiting , burns ); sepsis ; hemorrhage ( such as in major surgery or trauma ); and systemic inflammatory responses to acute diseases ( e . g . pancreatitis ). 1 The fluids will eventually distribute through the body , but the longer the fluid remans within the intravascular compartment the better , as this may make fluid resuscitation easier . 1
There are two types of fluid used : broadly classified as either colloids or crystalloids . There is no single ‘ ideal ’ IV fluid for resuscitation 1 but there are advantages and disadvantages of both , which will be discussed in this article .
Colloids Colloid solutions consist of high molecular weight compounds suspended in a carrier vehicle which prolongs the time the colloid remains within the intravascular space . 2 It is believed that the oncotic gradient created by the colloids draws fluid from the interstitial fluid into the intravascular space , thereby producing a volume expansion effect . Examples of a natural colloid include human albumin , which is present in plasma and commercially available in the US as both a 5 % and 25 % solution although 4 % and 20 % solutions are used in other parts of the world . Synthetic colloids include hydroxyethyl starch ( HES ) and gelatins .
Hydroxyethyl starch Hydroxyethyl starches ( HES ) are derived from the starch of either potatoes or maize and represent a family of semi-synthetic , colloid solutions made from a large number of ethylated , polymerized amylopectin ( glucose ) molecules . 3 There are several different types of HES , each of which is identified by three key numbers . Using 10 % HES 200 / 0.5 as an example : the first number is the concentration ( 10 %); the second ( 200 ) refers to the molecular weight in kiloDaltons ( kDa ); and the third number ( 0.5 ), the molar substitution , which relates to the number of hydroxyethyl residues attached to anhydrous glucose particles within the polymer and which affect the water solubility . 4
In 1972 , the first generation of starches were approved by the FDA for medical treatment , although it has since emerged that the data used to support the license were based on uncontrolled trials and volunteers were observed for less than 24 hours . 5 Concerns over the potential for serious side-effects with HES began to emerge in the 1970s ; in particular , the negative impact on coagulation factors 6 and how HES infusions were stored within tissue . 7 Furthermore , in a 2011 metaanalysis of 56 randomized trials with HES in acute hypovolemia from the elective surgery setting , the authors reported on how studies were generally undertaken with a small number of patients and were of short-duration . They concluded that the extent of fluid load reduction achieved by HES 130 / 0.4 is overestimated and that clinicians should be aware that there is no convincing evidence that third-generation HES 130 / 0.4 is safe in surgical , emergency , or intensive care patients . 8
Evidence for an adverse effect on renal function emerged in a large trial of patients with sepsis ,
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