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Crystalloids: pros and cons


with severe sepsis, particularly if they require large amounts of fluid.10,11 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, anti- oxidant 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.


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


References 1. Awad S, Allison SP, Lobo DN. The history of 0.9% saline. Clin Nutr 2008;27:179–88.


2. Lobo DN et al. Problems with solutions: drowning in the brine of an inadequate knowledge base. Clin Nutr 2001;20:125–30.


3. Callum KG et al. Extremes of Age: The 1999 Report of the National Confidential Enquiry into Perioperative Deaths: London: NCEPOD, 1999.


4. Powell-Tuck J et al. British Consensus Guidelines on Intravenous Fluid Therapy for Adult Surgical Patients (GIFTASUP). BAPEN Medical, 2011. Available at: www.bapen.org.uk/pdfs/bapen_ pubs/giftasup.pdf [accessed 14/9/13]


5. Perel P, Roberts I, Ker K. Colloids versus crystalloids for fluid resuscitation in critically ill patients. Cochrane Database Syst Rev 2013;2:CD000567. doi: 10.1002/14651858.CD000567.pub6.


6. Bisonni RS et al. Colloids versus crystalloids in fluid resuscitation: an analysis of randomized controlled trials. J Fam Pract 1991;32:387–90.


"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”


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


7. Skellett S et al. Chasing the base deficit: hyperchloraemic acidosis following 0.9% saline. Arch Dis Child 2000;83:514–6.


8. Haase N et al. Hydroxyethyl starch 130/0.38-0.45 versus crystalloid or albumin in patients with sepsis: systematic review with meta-analysis and trial sequential analysis. BMJ 2013;346:f839


9. McClelland DBM (Ed). Handbook for Transfusion Medicine (4th edition). UK Blood Services, TSO Norwich, 2007.


10. Dellinger RP et al. Surviving sepsis campaign: international guidelines for management of severe sepsis and septic shock: 2012. Crit Care Med 2013;41:580–637.


11. Reinhart K et al. Consensus statement of the ESICM task force on colloid volume therapy in critically ill patients. Intens Care Med 2012;38:368–83.


12. Halijame H. Use of fluids in trauma. Int J Intens Care 1999;6:20.


13. Jacob M et al. The intravascular effect of Ringer's lactate is below 20%: a prospective study in humans. Crit Care 2012;16:R86.


14. Quinlan GJ, Martin GS, Evans TW. Albumin: biochemical properties and therapeutic potential. Hepatology 2005; 41:1211–19.


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