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2017 PNLE REVIEW MATERIALS FOR SALE

Sunday, May 20, 2012

Water and Electrolyte Solutions


Selected Water and Electrolyte Solutions

Solution

Comments
Isotonic Solutions

0.9% NaCl (isotonic, also called NSS)
Na+ 154 mEq/L
Cl- 154 mEq/L
(308 mOsm/L)
Also available with varying concentrations of dextrose (the most frequent used is a 5% dextrose concentration

·   An isotonic solution that expands the ECF volume, used in hypovolemic states, resuscitative efforts, shock, diabetic ketoacidosis, metabolic alkalosis, hypercalcemia, mild Na deficit
·   Supplies an excess of Na and Cl; can cause fluid volume excess and hyperchloremic acidosis if used in excessive volumes, particularly in patients with compromised renal function, heart failure or edema
·   Not desirable as a routine maintenance solution, as it provides only Na and Cl (and these are provided in excessive amounts)
·   When mixed with 5% dextrose, the resulting solution becomes hypertonic in relation to plasma, and in addition to the above described electrolytes, provides 170cal/L
·   Only solution that may be administered with blood products


Lactated Ringer’s solution (Hartmann’s solution)
Na+ 130 mEq/L
K+ 4 mEq/L
Ca++ 3 mEq/L
Cl- 109 mEq/L
Lactate (metabolized to bicarbonate) 28 mEq/L (274 mOsm/L)
Also available with varying concentration of dextrose (the most common is 5% dextrose)

·   An isotonic solution that contains multiple electrolytes in roughly the same concentration as found in plasma (note that solution is lacking in Mg++) provides 9 cal/L
·   Used in the tx of hypovolemia, burns, fluid lost as bile or diarrhea, and for acute blood loss replacement
·   Lactate is rapidly metabolized into HCO3- in the body. Lactated Ringer’s solution should not be used in lactic acidosis because the ability to convert lactate into HCO3- is impaired in this disorder.
·   Not to be given with a pH > 7.5 because bicarbonates is formed as lactate breaks down causing alkalosis
·   Should not be used in renal failure because it contains potassium and can cause hyperkalemia
·   Similar to plasma

Selected Water and Electrolyte Solutions

Solution

Comments
Isotonic Solutions

5% Dextrose in Water (D5W)
No electrolytes
50 g of glucose

·   An isotonic solution that supplies 170 cal/L and free water to aid in renal excretion of solutes
·   Used in treatment of hypernatremia, fluid loss and dehydration
·   Should not be used in excessive volumes in the early post-op period (when ADH secretion is increased due to stress reaction)
·   Should not be used solely in tx of fluid volume deficit, because it dilutes plasma electrolyte concentrations
·   Contraindicated in head injury because it may cause increased intracranial pressure
·   Should not be used for fluid resuscitation because it can cause hyperglycemia
·   Should be used with caution in patients with renal or cardiac dse because of risk of fluid overload
·   Electrolyte-free solutions may cause peripheral circulatory collapse, anuria in pt. with sodium deficiency and increased body fluid loss
·   Converts to hypotonic solution as dextrose is metabolized by body. Overtime D5W without NaCl can cause water intoxication (ICF vol. excess bec. solution is hypotonic)

Hypotonic Solutions

0.45% NaCl
half-strength saline)
Na+ 77 mEq/L
Cl- 77 mEq/L
(154 mOsm/L)
Also available with varying concentration of dextrose (the most common is 5% dextrose)

·   Provides Na, Cl and free water
·   Free water is desirable to aid the kidneys in elimination of solute
·   Lacking in electrolytes other than Na and Cl
·   When mixed with 5% dextrose, the solution becomes slightly hypertonic to plasma and in addition to the above-described electrolytes provides 170 cal/L
·   Used in the tx of hypertonic dehydration, Na and Cl depletion and gastric fluid loss
·   Not indicated for third-space fluid shifts or increased intracranial pressure
·   Administer cautiously, because it can cause fluid shifts from vascular system into cells, resulting in cardiovascular collapse and increased intracranial pressure
Selected Water and Electrolyte Solutions

Solution

Comments
Hypertonic Solutions

3% NaCl (hypertonic saline)
Na+ 513 mEq/L
Cl- 513 mEq/L
(1026 mOsm/L)


·   Used to increase ECF volume, decrease cellular swelling
·   Highly hypertonic solution used only in critical situations to treat hyponatremia
·   Must be administered slowly and cautiously, because it can cause intravascular volume overload and pulmonary edema
·   Supplies no calories
·   Assists in removing ICF excess


5% NaCl (hypertonic solution)
Na+ 855 mEq/L
Cl- 855 mEq/L
(1710 mOsm/L)

·   Highly hypertonic solution used to treat symptomatic hyponatremia
·   Administered slowly and cautiously, because it can cause intravascular volume overload and pulmonary edema
·   Supplies no calories

Colloid Solutions

Dextran in NS or 5% D5W
Available in low-molecular-weight (Dextran 40) and high-molecular-weight (Dextran 70) forms

·   Colloid solution used as volume/plasma expander for intravascular part of ECF
·   Affects clotting by coating platelets and decreasing ability to clot
·   Remains in circulatory system up to 24 hours
·   Used to treat hypovolemia in early shock to increase pulse pressure, CO, and arterial BP
·   Improves microcirculation by decreasing RBC aggregation
·   Contraindicated in hemorrhage, thrombocytopenia, renal dse and severe dehydration
·   Not a substitute for blood or blood products

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