Crystalloid Isotonic Solution

Aka: Crystalloid Isotonic Solution, Normal Saline, Isotonic Saline, Lactated Ringers, Ringer's Lactate, Ringer's Acetate, Acetated Ringers, Hartmann's Solution, Balanced Crystalloid, Isotonic Solutions, Intravenous Fluid Acidity, Plasma-Lyte, Plasma-lyte 148, Normosol-R

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II. Types

  1. Lactated Ringers
  2. Normal Saline

III. Advantages

  1. Inexpensive and readily available
  2. Does not result in Allergic Reactions

IV. Disadvantages

  1. Only transiently expand the intravascular volume
  2. Only 25% remains in intravascular space (75% distributes throughout the non-vascular interstitial space)
    1. See Sodium and Water Homeostasis
  3. Requires infusion of 4-5x the deficit
    1. May result in Pulmonary Edema in critically ill

V. Preparations: Normal Saline (0.9% NaCl or NS)

  1. Osmolality: 308 mOsm/L (contrast with 290 mOsm/L in extracellular fluid)
  2. Sodium: 154 mEq/L (contrast with 140 mEq/L in extracellular fluid)
  3. Chloride: 154 mEq/L (contrast with 103 mEq/L in extracellular fluid)
  4. pH: 5.7 (contrast with 7.4 in extracellular fluid)
  5. Disadvantages
    1. Differs significantly from extracellular fluid (see above)
    2. Risk of hyperchloremic Non-Anion Gap Metabolic Acidosis (worse in renal dysfunction)
      1. However Normal Saline is an ideal solution in Vomiting (acid losses)
      2. See Intravenous Fluid Acidity as below
    3. Increased Interstitial Edema
      1. Intracellular fluid increases 10% more than infused
      2. Higher osmolality drives Fluid Shifts from intracellular space
      3. Renin-Angiotensin and Aldosterone suppression results in Sodium retention
    4. Decreased renal perfusion
      1. Renal Vasoconstriction (chloride mediated)

VI. Preparations: Balanced Crystalloid (Buffered)

  1. Lactated Ringers (LR), Ringer's Lactate or Hartmann's Solution
    1. Sydney Ringer, british physician, studied NaCl solution in 1880s in frogs
      1. Alexis Hartmann buffered NaCl with Sodium lactate in the 1930s
    2. Osmolality: 272 mOsm/L (contrast with 290 mOsm/L in extracellular fluid)
    3. Sodium: 130 mEq/L (contrast with 140 mEq/L in extracellular fluid)
    4. Chloride: 109 mEq/L (contrast with 103 mEq/L in extracellular fluid)
    5. Lactate: 28 mEq/L (buffer)
      1. Ringer's Acetate, an alternative solution used in liver failure, uses acetate instead of lactate as buffer
      2. Lactate buffer does not significantly raise serum lactate level (unless large volume without lactate clearance)
      3. However, do not obtain serum lactate levels from an IV infusing LR (falsely elevated serum lactate levels)
    6. Also contains Potassium (4 mEq/L) and Calcium (3 mEq/L)
    7. pH: 6.5 (contrast with 7.4 in extracellular fluid)
      1. However, unlike NS, LR is roughly neutral pH when infused (see below)
    8. First-line scenarios
      1. Large-volume crystalloid bolus or infusion (>2 Liters)
      2. Pancreatitis
      3. Pregnancy, especially hyperemesis (add dextrose to the solution)
    9. Drug Interactions (related to Calcium content and basic pH) - Infuse in a different IV line
      1. Ceftriaxone
        1. In age under 1 month, do not use simultaneously with LR regardless of different line
      2. Ampicillin
      3. Carbapenems
      4. Potassium Phosphate
      5. Nicardipine
      6. Phenytoin
      7. Neuromuscular Blockers (e.g. Atacurium, Cisatracurium)
      8. Swaminathan, Weingart and Nordt in Herbert (2020) EM:Rap 20(5):8-9
    10. Disadvantages
      1. Hypotonic (avoid in Closed Head Injury due to Increased Intracranial Pressure risk)
      2. Drug Interactions (see above)
      3. Lactate may accumulate in a preexisting Lactic Acidosis, and cannot initially be cleared
        1. LR contribution to serum lactate is negligible and should not persist Lactic Acidosis
  2. Plasma-lyte 148 (or Normosol-R)
    1. Osmolality: 294 mOsm/L
    2. Sodium: 140 mEq/L
    3. Chloride: 98 mEq/L
    4. Buffer: 50 mEq/L (acetate and gluconate)
    5. Contains Potassium (5 mEq/L)
    6. Contains Magnesium (3 mEq/L) in place of the Calcium present in LR
    7. pH: 7.4
    8. Decreased Interstitial Edema when compared with Normal Saline
  3. References
    1. Loflin (2015) Crit Dec Emerg Med 29(9): 11-18

VII. Preparation: Other Isotonic Solutions

  1. D5W with 3 ampules Sodium Bicarbonate
    1. Isotonic alkalotic solution
    2. Indications
      1. Pre-existing non-Anion Gap, Hyperchloremic Metabolic Acidosis or RTA
    3. References
      1. Weingart and Orman in Herbert (2015) EM:Rap 15(10): 16-7

VIII. Pharmacokinetics: Intravenous Fluid Acidity

  1. Background
    1. Primary Acid-Base Homeostasis is achieved via pulmonary and renal mechanisms
    2. Intravenous Fluid Acidity only affects Blood pH with prolonged or large volume Intravenous Fluid administration
  2. Strong ions (Sodium and chloride) determine Intravenous Fluid Acidity
  3. Normal serum cation-anion difference (Strong Ion Difference): 38 meq/L
    1. Positive serum Sodium Cations (140 meq/L) minus
    2. Negative Serum Chloride anions (102 meq/L)
  4. Intravenous Fluid impacts normal serum acidity when its cation-anion difference is not 24 meq/L
    1. Accounts for 14 meq/L difference resulting from dilution of the normally acidic Serum Albumin
    2. Overall neutral Intravenous Fluid: 38 meq/L (cations-anions) - 14 meq/L (albumin dilution) = 24 meq/L
  5. Intravenous Fluid cation-anion difference or gap will impact the serum acidity based on the serum bicarbonate level
    1. Cation-Anion difference of 15 meq/L has no impact on Blood pH when serum bicarbonate is also 15 meq/L
  6. Intravenous Fluid acidities (cation-Anion Gap)
    1. Lactated Ringers: 24 meq/L
      1. Neutral (no change in acidity) - balanced solution
    2. Normal Saline (or D51/2NS or D5W): 0 meq/L
      1. Acidic (will acidify the serum) - significantly if multiple liters infused
        1. Normal Saline volumes used in Sepsis may significantly affect serum pH
        2. NS at 30 ml/kg/h over 2 hours will drop serum pH from 7.41 to 7.28
      2. Risk of hyperchloremic, Non-Anion Gap Metabolic Acidosis
      3. Risk of pro-inflammatory affects, Coagulopathy and increased infection risk
      4. Risk of decreased GFR and Acute Kidney Injury
    3. Plasmalyte: 55 meq/L
      1. Alkalotic
  7. Either NS or buffered solution (e.g. LR, Plasmalyte) are suitable for non-massive Fluid Replacement
    1. No increased Acute Kidney Injury or mortality with Normal Saline compared with buffered solution with non-massive replacement
    2. Young (2015) JAMA 314(16): 1701-10 +PMID:2644692 [PubMed]
  8. References
    1. Loflin (2015) Crit Dec Emerg Med 29(9): 11-18
    2. Weingart in Majoewsky (2013) EM:Rap 13(8): 6

IX. References

  1. Marino (2014) The ICU Book, p. 217-37
  2. Weingart and Orman in Herbert (2015) EM:Rap 15(10): 16-7

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