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Fluid Volume and Osmolality
Good health=volume and osmolality of extra…
Fluid Volume and Osmolality
Good health=volume and osmolality of extra and intracellular fluids are WNL
KIDNEYS maintain both!
Volume contraction = decrease in total body water
Volume expansion = increase in total body water
Isotonic Contraction
Volume contraction where Na+ and H2O are lost in isotonic proportions...decrease in total volume, no increase in osmolality
-
-
Hypertonic Contraction
Loss of H2O exceeds loss of NA+
Reduced extracellular fluid volume
Increase in osmolality
Causes:
Excessive sweating
Osmotic diuresis
Concentrated food given to infants
2ndary to big burns
CNS disorders that mess with thirst
Treatment:
Hypotonic fluids (0.45% sodium chloride)
-or- Fluids that contain NO solutes (D5W)
Initial tx=DRINK WATER
Hypotonic Contraction:
Loss of Na+ exceeds water loss
BOTH volume and osmolality of extracellular fluid reduced
-
Treatment:
Mild: infuse isotonic sodium chloride for injection
Severe: Hypotonic solution (3% NaCl)
Watch for fluid overload!
Volume Expansion
Increase in total volume of body fluid
Can be isotonic, hypotonic, hypertonic
Causes:
OD on therapeutic fluids
Diseases (CHF, nephrotic syndrome, cirrhosis w/ascites)
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Acid / Base Disturbances
Maintained by multiple systems:
-bicarbonate-carbonic acid buffer system
-respiratory system (CO2 increase lowers pH)
-Kidneys (HCO3- increase raises pH)
Respiratory Alkalosis
Cause:
-hyperventilation causes decrease in CO2
Treatment:
-mild: no tx needed
-severe: rebreathe CO2 laden breath
Respiratory Acidosis
Cause:
-retain CO2 2ndary to hypoventilation
-(depression of medullary resp. center)
-(pathologic changes in lungs)
Treatment:
-correct respiratory impairment
-infuse sodium bicarbonate if severe
Metabolic Alkalosis
Causes:
-excessive loss of gastric acid
-admin. of alkalinizing salts
Treatment:
-solution of sodium chloride + potassium chloride
Metabolic Acidosis
Causes:
-chronic renal failure
-loss of bicarbonate in severe diarrhea
-metabolic disorders
-poisoning by methanol and certain meds
Treatment:
-correcting underlying cause
-alkalinizing salt if severe
Potassium
Most abundant intracellular cation
[low] in extracellular
Major roles:
-conducting nerve impulses
-maintain electrical excitability of the muscle
-regulate acid/base balance
Regulation:
-Kidneys
-Excretion increased by aldosterone
-Excretion increased by most diuretics (EXCEPT K+ SPARING!)
-Influenced by extracellular pH (alkolosis=K+ uptake enhanced, acidosis=K+ exits cells)
-Insulin (profound effect on K+ levels)
Hypokalemia
K+ levels less than 3.5 mEq/L
Most common cause: tx w/ thiazide or loop diuretics
Less common: excessive insulin or alkalosis
Has adverse effects on skeletal and smooth muscle, BP & heart
Increases risk for HTN and stroke
Treatment:
Potassium salts preferred
(chloride deficiency frequently coexists w/ hypokalemia
Mild: Oral potassium chloride
sustained release=fewer GI effects
abd. discomfort, nausea, vomiting, diarrhea
take w/meals or full glass of water
Severe: IV potassium chloride
must be diluted & infused slowly
NEVER admin. by IV push!
(above results in cardiac arrest)
IV extremely irritating to veins
Contraindications: avoid in pts. pre-disposed to hyperkalemia (severe renal impariment, use of K+ sparing diuretics, hyperaldosteronism)
Principal complication of HYPO is HYPER
-assess renal fx/ECG changes
Hyperkalemia
Excessive elevation of serum potassium
Causes:
-Severe tissue trauma
-Untreated Addison's
-Acute acidosis (draws K+ out of cells)
-Abuse of K+ sparing diuretics
-OD w/IV potassium
Adverse:
Disrupts electrical activity of the heart
Cardiac arrest can occur in severe case
May also see confusion, anxiety, dyspnea, weak/heavy legs, numb/tingling in hands, feet, lips
Treatment:
-Withhold K+ foods
-Hold meds that promote K+ accumulation (K+ sparing diuretics, K+ supps.)
-Counteract K+ induced cardiotoxicity
-Lower extracellular levels of K+ (Ca+ salt, infuse glucose+insulin, If acidosis, infuse sodium bicarbonate, etc....
Magnesium
Required for enzyme activity
Binding of MRNA to ribosomes
Helps regulate neurochemical transmission
Helps regulate muscle excitability
Hypomagnesmia
Caused by:
Diarrhea
Hemodialysis
Kidney Disease
Prolonged IV feeding
Chronic alcoholism
Hypermagnesemia
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Hypermagnesmia
-Most common in pts. w/ renal insufficiency
(esp. when pt. uses Mag. containing antacids or cathartics)
-Mild sx.= muscle weakness, hypotesion, sedation, ECG changes
-Muscle weakness/paralysis can be treated w/ IV Calcium
Also-
Respiratory paralysis @ 12-15 mEq/L
Cardiac arrest when levels exceed 25 mEq/L