Intravenous fluids

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Intravenous fluids are a critical component of modern medical therapy. For principles of maintenance see fluid balance. This is not the same as fluid resuscitation. This is both simple and complex and all too easy to get wrong because of poor understanding of physiology and appropriate monitoring. Particular recurrent issues are:

  • Fluid over or under load with failure to react to documented fluid balance or failure to monitor patients daily weight where practicable[1]
  • Induction of hyponatraemia in children[2] or the typical (elderly) patient with vasopressin excess due to pathology/drugs[3] by infusion of effectively hypotonic fluids

In basic terms they fall into three categories:

Contents

Crystalloids

The term crystalloid in chemistry refers to substances which may possess crystal-like properties in certain circumstances.

In medicine we use the term crystalloid as a convenient shorthand for intravenous infusion fluids which are composed of solutions of crystalline substances, such as sodium chloride, potassium chloride, or glucose (occasionally several different substances, as in Hartmann's solution). It is likely this term is influenced by the use of the term "colloid"; see below.

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Standard practice based on NPSA guidance is not to add potassium solutions to infusions in the routine ward environment

Such solutions may have different constituents depending on their indications for use.

Osmolarity

The amount of solute influences two related, but subtly different properties: osmolality refers to the amount of solute, whereas tonicity refers to osmotic effect of the solution in relation to another solution across a semi-permeable membrane. Osmolality is indepedent of the context, whereas tonicity is defined relative to a reference point (usually blood or intracellular osmolality) and is also dependent on whether the solute can pass freely through the cell membrane.

Tonicity

The concept of tonicity in the body is complex as cell permeability varies with cell type and circumstances. For example, in a non-diabetic, glucose is rapidly transported into cells and so exerts little persisting osmotic effect, whereas in a insulin-deficient type 1 diabetic, glucose cannot enter the cells and remains in the intravascular space where it exerts a hypertonic effect.

Most solutions aim to be iso-osmolar to reduce osmotic damage to blood cells and irritation to the veins. However, a hyperosmolar solution such as 5% glucose with 20mmol KCl can actually be effectively hypotonic as the glucose is rapidly absorbed into the cells leaving only the 20mmol KCl and electrolyte-free water (see also explanation in tonicity).

Distribution

  1. In a non diabetic patient 1 litre of a 5% glucose will reach physiological equilibrium distributed in proportion to total body water, about 650 ml intracellularly and 350ml in the extracellular compartment. Theses proportions might be helpful in dehydration but not in resuscitation of a patient with other pathologies.
  2. However predominantly sodium and chloride ion based fluids such as Hartman's or 0.9% saline will remain in the extracellular compartment. They will be distributed about 75% to the interstitial fluid and 25% to the intravascular fluid. So for each litre of iv fluid with Hartman's or 0.9% saline about 250ml goes towards rising the blood pressure while less than 100mls of 5% glucose would do so.

Composition

Composition of Intravenous Fluids (Based on 1-litre bags)
Type Na+ K+ Ca2+ Cl- HCO3- Other pH osm. tonicity Comments
Plasma 140 4.5 2.3 100 26 ++ 7.4 290 = =
Saline 0.45% 77 0 0 77 0 0 5.0 154 --- 'half' saline
Saline 0.9% 154 0 0 154 0 0 5.0 308 + 'normal' saline
Saline 0.9% + 20mmol KCl 154 20 0 174 0 0  ? 348 +
Saline 0.9% + 40mmol KCl 154 40 0 194 0 0  ? 388 ++
Glucose 5% 0 0 0 0 0 glucose 277 mM  ? 277 - 50g glucose per litre
Glucose 5% + 20mmol KCl 0 20 0 20 0 glucose 277mM  ? 317 + 50g glucose per litre
Glucose 5% + 40mmol KCl 0 40 0 40 0 glucose 277mM  ? 357 ++ 0
Glucose 10% 0 0 0 0 0 glucose 556mM  ? 556 ++ 100g glucose per litre
Glucose 50% 0 0 0 0 0 glucose 2.77M  ? 2777 +++ Usually 25g in 50ml; very irritant
Glucose 4% Saline 0.18% 31 0 0 31 0 glucose 222mM  ? 284 - 40g glucose per litre
Glucose 5% Saline 0.45% 77 0 0 77 0 glucose 277mM  ? 431 ++ 0
Hartmann's solution 131 5 2.0 111 29 lactate 29mM 7.0 278 - 0
Ringer's lactate 130 4 1.4 109 28 lactate 28mM 6.5 273[4] - 0
Plasmalyte 148 and 5% glucose 140 5 0 98 29 acetate 27mM, gluconate 23mM 5.0 294 = available with 5% glucose

Evidence Base

Some selected studies and evidenced based statements include:

  • Rapid infusion of glucose or Hartmann's is inappropriate in labour[5]
  • In routine crystalloid resuscitation and acute replacement, because of the risk of inducing hyperchloraemic acidosis balanced salt solutions ( Ringer’s or Hartmann’s) are beneficial over 0.9% saline (except hypochloraemia e.g. from vomiting or gastric drainage, liver disease)[6]
  • Typical crystalloid requirements in major surgery may be of the order of 10-15 ml/kg/h [7]
  • Solutions containing glucose (dextrose) such as 4%/0.18% glucose/saline and 5% glucose are only appropriate for resuscitation or replacement therapy where there is significant free water deficit as in diabetes insipidus[8] They are likely to be ineffective or harmful through hyponatraemia in children (where they should not be generally used[9])and can be harmful in the elderly.
  • The biochemical abnormalities induced by saline versus Hartmann's in normal adults of hyperchloraemia and lower serum bicarbonate concentration in the former[10] might actually be an advantage in chronically sick fluid deficient patients as the fluid and sodium load is not excreted so quickly.
  • In brain trauma 5% glucose likely to be ineffective or harmful compared to saline[11]
  • In brain trauma 5% glucose likely to be ineffective or harmful compared to Ringer's[12]
  • Lactated Ringers is beneficial compared to saline or colloids in acute shock from Dengue fever[13][14]
  • There is no advantage in hypertonic fluids with brain injury[15]

Colloids

A colloid is the name given to a microparticulate dispersal of one substance in another. This need not be a liquid; for example, smoke is a colloid (a dispersal of solid carbon particles in air). What differentiates a colloid from a mixture is that the dispersal is so fine that the particles are kept suspended in perpetuity by Brownian motion. What differentiates a colloid from a solution is that colloids are physically separable (they may be separated by ultrafiltration or centrifugation), whereas a solution requires chemical separation such as evaporation or chemical reaction (you cannot filter the sugar out of your tea, nor centrifuge it out).

In medicine, we use the term "colloid" as a convenient shorthand for an intravenous fluid which is formed by a colloidal suspension of large molecules in a water- or saline-based medium.

Colloids in this sense are suspensions of macromolecules, usually in a saline medium. These may be physiological (such as 4.5% albumin), semi-synthetic, such as succinylated gelatine (which in turn is solubilised bovine collagen), or synthetic, such as hydroxyethyl starch which as of 2011 as major evidence base issues. These large molecules tend to remain in the vascular compartment after infusion. Here they exert an osmotic pressure which tends to keep water in the vascular compartment, thereby helping to expand the circulating blood volume and resist redistribution.

Colloids may be overprescribed. There is conflicting evidence about their efficacy; the currently held consensus view is that, in acute volume replacement, they are no better than crystalloids, and may be harmful in some circumstances. Foreign proteins such as gelatine may provoke anaphylaxis in rare circumstances. However, there are strong adherents to their use.

Evidence Base

  • Colloids have no clinical advantage compared to crystalloids for fluid resuscitation in critically ill adults[16] or children[17]
  • Hypovolaemic patients given albumin instead of saline does not reduce mortality[18][19]
  • Albumin does not reduce mortality in critically ill patients with burns and hypoalbuminaemia[20][21]
  • In children with severe malaria, resuscitation with albumin has lower mortality than resuscitation with saline infusion or Gelofusine®[22]
  • In critical traumatic brain injury treatment with albumin compared to saline is likely to be ineffective or harmful[23]
  • In intensive care serum albumin concentration is irrelevant, outcome is the same with saline or albumin[24]

Transfusion

Blood product transplant, most commonly packed red cells


References

  1. Ferenczi E, Datta SS, Chopada A. Intravenous fluid administration in elderly patients at a London hospital: A two-part audit encompassing ward-based fluid monitoring and prescribing practice by doctors. . 2007 Jun 8.(Epub ahead of print) (Link to article – subscription may be required.)
  2. Choong K, Kho ME, Menon K, Bohn D. Hypotonic versus isotonic saline in hospitalised children: a systematic review. Archives of disease in childhood. 2006 Oct; 91(10):828-35.(Link to article – subscription may be required.)
  3. Moritz ML, Ayus JC. Hospital-acquired hyponatremia--why are hypotonic parenteral fluids still being used? Nature clinical practice. Nephrology. 2007 Jul; 3(7):374-82.(Link to article – subscription may be required.)
  4. http://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=2881
  5. Morton KE, Jackson MC, Gillmer MD. A comparison of the effects of four intravenous solutions for the treatment of ketonuria during labour. British journal of obstetrics and gynaecology. 1985 May; 92(5):473-9.
  6. British Consensus Guidelines on Intravenous Fluid Therapy for Adult Surgical Patients GIFTASUP British Intensive Care Society 2008
  7. Campbell IT, Baxter JN, Tweedie IE, Taylor GT, Keens SJ. IV fluids during surgery. British journal of anaesthesia. 1990 Nov; 65(5):726-9.
  8. British Consensus Guidelines on Intravenous Fluid Therapy for Adult Surgical Patients GIFTASUP British Intensive Care Society 2008
  9. Patient safety alert : Reducing the risk of hyponatraemia when administering intravenous infusions to children NPSA 2007
  10. Reid F, Lobo DN, Williams RN, Rowlands BJ, Allison SP. (Ab)normal saline and physiological Hartmann's solution: a randomized double-blind crossover study. Clinical science (London, England : 1979). 2003 Jan; 104(1):17-24.(Link to article – subscription may be required.)
  11. Shapira Y, Artru AA, Qassam N, Navot N, Vald U. Brain edema and neurologic status with rapid infusion of 0.9% saline or 5% dextrose after head trauma. Journal of neurosurgical anesthesiology. 1995 Jan; 7(1):17-25.
  12. Feldman Z, Zachari S, Reichenthal E, Artru AA, Shapira Y. Brain edema and neurological status with rapid infusion of lactated Ringer's or 5% dextrose solution following head trauma. Journal of neurosurgery. 1995 Dec; 83(6):1060-6.
  13. Ngo NT, Cao XT, Kneen R, Wills B, Nguyen VM, Nguyen TQ, Chu VT, Nguyen TT, Simpson JA, Solomon T, White NJ, Farrar J. Acute management of dengue shock syndrome: a randomized double-blind comparison of 4 intravenous fluid regimens in the first hour. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2001 Jan 15; 32(2):204-13.
  14. Wills BA, Nguyen MD, Ha TL, Dong TH, Tran TN, Le TT, Tran VD, Nguyen TH, Nguyen VC, Stepniewska K, White NJ, Farrar JJ. Comparison of three fluid solutions for resuscitation in dengue shock syndrome. The New England journal of medicine. 2005 Sep 1; 353(9):877-89.(Link to article – subscription may be required.)
  15. Cooper DJ, Myles PS, McDermott FT, Murray LJ, Laidlaw J, Cooper G, Tremayne AB, Bernard SS, Ponsford J. Prehospital hypertonic saline resuscitation of patients with hypotension and severe traumatic brain injury: a randomized controlled trial. JAMA : the journal of the American Medical Association. 2004 Mar 17; 291(11):1350-7.(Link to article – subscription may be required.)
  16. Roberts I, Alderson P, Bunn F, Chinnock P, Ker K, Schierhout G. Colloids versus crystalloids for fluid resuscitation in critically ill patients. Cochrane database of systematic reviews (Online). 2004; (4):CD000567.(Epub) (Link to article – subscription may be required.)
  17. Upadhyay M, Singhi S, Murlidharan J, Kaur N, Majumdar S. Randomized evaluation of fluid resuscitation with crystalloid (saline) and colloid (polymer from degraded gelatin in saline) in pediatric septic shock. Indian pediatrics. 2005 Mar; 42(3):223-31.
  18. Alderson P, Bunn F, Lefebvre C, Li WP, Li L, Roberts I, Schierhout G. Human albumin solution for resuscitation and volume expansion in critically ill patients. Cochrane database of systematic reviews (Online). 2004; (4):CD001208.(Epub) (Link to article – subscription may be required.)
  19. Liberati A, Moja L, Moschetti I, Gensini GF, Gusinu R. Human albumin solution for resuscitation and volume expansion in critically ill patients. Internal and emergency medicine. 2006; 1(3):243-5.
  20. Alderson P, Bunn F, Lefebvre C, Li WP, Li L, Roberts I, Schierhout G. Human albumin solution for resuscitation and volume expansion in critically ill patients. Cochrane database of systematic reviews (Online). 2004; (4):CD001208.(Epub) (Link to article – subscription may be required.)
  21. Liberati A, Moja L, Moschetti I, Gensini GF, Gusinu R. Human albumin solution for resuscitation and volume expansion in critically ill patients. Internal and emergency medicine. 2006; 1(3):243-5.
  22. Akech S, Gwer S, Idro R, Fegan G, Eziefula AC, Newton CR, Levin M, Maitland K. Volume expansion with albumin compared to gelofusine in children with severe malaria: results of a controlled trial. PLoS clinical trials. 2006; 1(5):e21.(Epub) (Link to article – subscription may be required.)
  23. Myburgh J, Cooper J, Finfer S, Bellomo R, Norton R, Bishop N, Kai Lo S, Vallance S. Saline or albumin for fluid resuscitation in patients with traumatic brain injury. The New England journal of medicine. 2007 Aug 30; 357(9):874-84.(Link to article – subscription may be required.)
  24. Finfer S, Bellomo R, McEvoy S, Lo SK, Myburgh J, Neal B, Norton R. Effect of baseline serum albumin concentration on outcome of resuscitation with albumin or saline in patients in intensive care units: analysis of data from the saline versus albumin fluid evaluation (SAFE) study. BMJ (Clinical research ed.). 2006 Nov 18; 333(7577):1044.(Link to article – subscription may be required.)
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