Crystalloids : pros and cons with severe sepsis , particularly if they
10 , 11
require large amounts of fluid .
Similarly , crystalloids might not always be the best choice for volume resuscitation in cases of cardiac surgery due to the potential for fluid overload . Schramko ( also in this supplement ) has suggested that it might be advantageous to use albumin instead for volume resuscitation , particularly in patients at risk of fluid overload , bleeding or renal dysfunction .
Cons The comparative ' cons ' of crystalloids are due to their inherent pharmacological properties . As long as crystalloids are used in a considered manner , alongside colloids ( if appropriate ), then these pharmacological properties can be exploited for their clinical utility .
Potential for fluid and electrolyte overoad Crystalloids pass rapidly and freely across capillary membranes and equilibrate within the entire extracellular fluid space . Therefore , retention of a crystalloid within the intravascular space is poor . To replace a given volume of blood loss requires at least three times more crystalloid volume . As 75 – 80 % of the infused crystalloid volume will remain in the extravascular space , 12 fluid replacement with crystalloids is associated with an increased level of tissue hydration and risk of oedema : specifically , increased extravascular lung water and peripheral tissue oedema . Peripheral tissue oedema can affect wound healing and is uncomfortable for the patient , potentially making mobilisation more difficult . Oedema adversely affects the transport of oxygen and nutrients to tissue cells , potentially impairing organ function . Fluid overload with crystalloids can result in an increase in the fluid content of vital organs , including a delay in the return of normal gastrointestinal motility . In elderly patients with reduced functional respiratory and cardiovascular function , this can also result in significant morbidity and mortality . 3 In such situations , fluids with a high volume effect , such as albumin , should be considered instead for volume resuscitation . 13 If large volumes of crystalloids with high chloride content , particularly sodium chloride 0.9 %, are given in an attempt to restore the circulating volume , there is a risk of hypochloraemic acidosis . This , then , causes renal vasoconstriction and reduced glomerular filtration rate . In catabolic surgical patients , this is further compounded by increased urea production and the inflammatory response to surgery , resulting in a large proportion of sodium , chloride and water being retained within the interstitial space . Hence , there is a need for a balanced fluid replacement regimen , ensuring that an excessive quantity of neither fluid nor electrolytes are administered . Crystalloids are adequate for fluid resuscitation but lack additional beneficial properties provided by fluids such as albumin ( for example , antioxidant and anti-inflammatory effects ). 14
Potential for adverse respiratory effects If an excessive amount of dextrose is administered , particularly in critically ill , ventilator-dependent patients , an enhanced production of carbon dioxide and lactate may result . In addition , dextrose should not be used in isolation to treat hypovolaemia , as it only provides free water and does not replace electrolytes .
Lack of additional biochemical properties Crystalloids do not have any additional biochemical properties , with their action being only to provide fluid and , depending on the solution administered , electrolytes . Albumin also has antioxidant and anti-inflammatory properties and acts as a carrier molecule . 14
Conclusions Crystalloids are inexpensive , readily available intravenous solutions for the replacement and maintenance of fluid requirements . However , they should be prescribed in a considered approach tailored to individual patients ’ fluid requirements and clinical condition to avoid excessive fluid and electrolyte administration and subsequent effects on morbidity and mortality . A balanced fluid regimen should be administered incorporating a combination of different crystalloids and colloids , if indicated . Individual solution choices should reflect the current evidence-base . Education of the entire multi-disciplinary team regarding the appropriate use of crystalloids within a balanced fluid regimen is essential to ensure that practice is consistent and informed by consensus guidelines . l
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