ELECTROLYTES & SODIUM Flashcards
Total body water volume =
40 L, 60% body weight
Intracellular fluid volume =
Extracellular fluid volume =
25 L, 40% body weight
15 L, 20% body weight
Interstitial fluid volume =
Plasma volume =
12 L, 80% of ECF
3 L, 20% of ECF
• requires energy to move ions across cellular membranes
• e.g.: ATPase-dependent Na+-K+ ion pumps
Active transport
passive movement of ions across a membrane depends on size and charge of ion
• may be altered by physiologic and hormonal processes
Diffusion
• physical property of a solution that is based on the concentration of solutes (expressed as millimoles)
per kilogram of solvent (w/w)
OSMOLALITY
w/v
• inaccurate
> in cases of hyperlipidemia / hyperproteinemia for urine specimen
• presence of osmotically active substances (alcohol/mannitol)
Osmolarity
Normal plasma osmolality
_______ of plasma H20
•osmoreceptors respond to small changes
•regulated by AVP and thirst
> 275 - 295 mOsm/kg
URINE OSMOLALITY
• vary widely depending on water intake and collection circumstances
• decreased in:
• increased in:
• diabetes insipidus
• polydipsia
• SIADH
• hypovolemia
ELECTROLYTES
•Sodium
•Potassium
•Chloride
•Calcium
•Magnesium
•Lactate
•Phosphate
•Bicarbonate
• carry electric charge
• (+)
• (-)
• Exist in solid, liquid or gaseous environments
Ions
(Na, Cl, K)
Volume and osmotic regulation
(K, Mg, Ca)
• Myocardial rhythm and contractility
(Mg, Ca, Zn)
• Cofactors in enzyme activation
(Mg)
• Regulation of ATPase ion pumps
(HCO3, K, CI)
• Acid-base balance
(Ca, Mg)
• Blood coagulation
(K, Ca, Mg)
• Neuromuscular excitability
(Mg, PO4)
• Production and use of ATP from glucose
‹ Monovalent cation
SODIUM ION
• Most abundant cation in
the ECF
SODIUM ION
SODIUM
• Accounts ___of all the ECF cations
• Large determinant of____
90%
plasma osmolality
SODIUM ION REGULATION:
a) Intake of water in response to thirst
b) Excretion of water (affected by ADH in response to changes in either blood volume or osmolality)
c) Blood volume status (affects sodium excretion through aldosterone, angiotensin Il, and atrial natriuretic peptide)
SODIUM ION REGULATION:
Primary active transport
• Na-K adenosine triphosphatase pump
• Na-K leak channels
REFERENCE RANGES FOR
TABLE 16-6
SODIUM
Serum, plasma
Urine (24 h)
Cerebrospinal fluid
136-145 mmol/L
40-220 mmol/d, varies with diet
136-150 mmol/L
Clinical Significance
HYPONATREMIA
• ____mmol/L
• One of the most common electrolyte disorders
<135 mmol/L
Hyponatremia
• Probable cause
• ^ sodium loss
• 1 water retention
• Water imbalance
Hypernatremia
• Probable cause:
• Excess water loss
• Decrease water intake
• ^ sodium intake or retention
HYPERNATREMIA
•_______ mmol/L
• Less common
> 142 or >145
CAUSES OF HYPONATREMIA
INCREASED SODIUM LOSS
Hypoadrenalism
Potassium deficiency
Diuretic use
Ketonuria
Salt-losing nephropathy
Prolonged vomiting or diarrhea
Severe burns
CAUSES OF HYPONATREMIA
INCREASED WATER RETENTION
Renal failure
Nephrotic syndrome
Hepatic cirrhosis
Congestive heart failure
CAUSES OF HYPONATREMIA
WATER IMBALANCE
Excess water intake
SIADH
Pseudohyponatremia
SIADH, syndrome of inappropriate arginine vasopressin hormone secretion.
WITH LOW OSMOLALITY
Increased sodium loss
Increased water retention
CLASSIFICATION OF HYPO-NATREMIA BY OSMOLALITY
WITH NORMAL OSMOLALITY
Increased nonsodium cations
Lithium excess
Increased y-globulins-cationic (multiple myeloma)
Severe hyperkalemia
Severe hypermagnesemia
Severe hypercalcemia
Pseudohyponatremia
Hyperlipidemia
Hyperproteinemia
Pseudohyperkalemia as a result of in vitro hemolysis
WITH HIGH OSMOLALITY
Hyperglycemia
Mannitol infusion
HYPONATREMIA
Treatment
o Directed at correction of the condition that caused either water loss or sodium loss in excess of water loss
o fluid restriction and providing hypertonic saline and/ or other pharmacologic agents
HYPONATREMIA
Treatment
• Correcting severe hyponatremia too rapidly can cause cerebral myelinolysis and too slowly can cause cerebral edema
CAUSES OF HYPERNATREMIA
EXCESS WATER LOSS
Diabetes insipidus
Renal tubular disorder
Prolonged diarrhea
Profuse sweating
Severe burns
CAUSES OF HYPERNATREMIA
DECREASED WATER INTAKE
Older persons
Infants
Mental impairment
CAUSES OF HYPERNATREMIA
INCREASED INTAKE OR RETENTION
Hyperaldosteronism
Sodium bicarbonate excess
Dialysis fluid excess
• Excess loss of water relative to sodium loss
HYPERNATREMIA
HYPERNATREMIA
• Diabetes Insipidus
• Neurogenic:
• Nephrogenic:
Deficiency of ADH
Renal Tubules cannot respond to ADH
• Patient drink large volumes of water, hypernatremia usually does not occur unless the thirst mechanism is also impaired
Huoernatremia
• Decreased water intake
• Commonly occurs in those persons Who may be thirsty out who are unable to ask for or obtain water (adults with altered mental status and infants)
HYPERNATREMIA
HYPERNATREMIA
•
•
•
•
Increased sodium intake or retention
Administration of hypertonic solutions of sodium
Sodium bicarbonate
Hypertonic dialysis solutions
Treatment
• Directed at correction of the underlying condition that caused the water depletion or sodium retention
• Rapid correction can induce cerebral edema and death
HYPERNATREMIA
URINE OSMOLALITY
Diabetes insipidus (impaired secretion of AVP or kidneys cannot respond to AVP)
<300 mOsm/kg
URINE OSMOLALITY
Partial defect in AVP release or response to AVP
Osmotic diuresis
300-700 mOsm/kg
URINE OSMOLALITY
Loss of thirst
Insensible loss of water (breathing, skin)
Gastrointestinal loss of hypotonic fluid
Excess intake of sodium
AVP, arginine vasopressin hormone.
> 700 mOsm/kg
• Neuropsychiatric
HYPONATREMIA
• Nausea
• Vomitting
• Lethargy
• Seizure
• Coma
• Respiratory depression
• Muscular weakness
• Headache
• ataxia
HYPONATREMIA
• Lethargy o Irritability
• Restlessness
• Seizures
• Muscle twitching
• Hyperreflexes
• Difficult respiration
• Increased thirst
• Nausea
HYPERNATREMIA
• Altered mental status
HYPERNATREMIA
Less than 125
<120
HYPONATREMIA
Above 160
HYPERNATREMIA
