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Fluids and Electrolytes (etiology and pathophysiology (5 R's for…
Fluids and Electrolytes
etiology and pathophysiology
5 R's for prescribing IV fluids
reassessment (observe pt's fluid/electrolyte needs again)
resuscitation
colloids
are very effective, but routine use is not warranted (no benefit over
crystalloids
in mortality)
caution if patient shows signs of shock
acutely expand intravascular volume in hypovolemic states and replace extracellular losses
0.9% NaCl remains as the most common resuscitation fluid in the US
routine maintenance
restrict initial Rx to 25-30 mL/kg/day and 50-100g/day of glucose to limit starvation ketosis
deliver fluids during daytime hours to promote sleep and well-being
prescribing >2.5L/day increases the risk of hyponatremia
NG fluids or enteral feeding are preferable when maintenance needs are for >3 days
replacement (patient has electrolyte deficits/excesses)
redistribution (patient experiences ongoing abnormal fluid losses or distribution)
always adjust IV fluid prescriptions for obese pts to their IBW!
total body water in men (60%) is slightly higher than that in women (50%)
adipose tissue is composed of ~10-30% water
initial assessment (ABCDE method)
assess needs from med history (previous intakes, thirst, quantity/composition of abnormal losses, comorbidities)
indicators of
hypovolemia
(low volume of circulating blood)
systolic BP <100mmHg
HR >90bpm
respiratory rate > 20 bpm
NEWS > 5
peripheries are cold to the touch
capillary refill time >2 sec
Airway, Breathing, Circulation, Disability, Exposure
types of electrolyte emergencies
sodium
hypernatremia
plasma Na+ >145 mEq/L
usually controlled via ADH release and the thirst mechanism
occurs in vulnerable pts (elderly, infants, people with limited access to water)
causes cerebral cellular dehydration (leads to permanent brain damage and stroke)
tx: slow fluid correction (over at least 48 hours)
s/sx: lethargy, AMS, restlessness, thirst, muscle spasms, seizures, coma
hyponatremia
plasma Na+ <130 mEq/L
leading cause of afebrile seizures in infants
tx: hypertonic saline in the ICU (if severe) or loop diuretics to increase water loss
s/sx: seizures, loss of consciousness, hypotension, muscle spasms, AMS
most common electrolyte disturbance in hospital population
normal range: 135-145 mEq/L
most abundant
extracellular cation
in the body
potassium
hyperkalemia
plasma K+ > 5.5 mEq/L
most deadly
electrolyte disturbance
drugs that may increase K+ include NSAIDs, ACEIs, ARBs, heparin, spironolactone, and non-selective beta blockers
s/sx: paresthesia, cramps, muscle weakness, arrhythmias
treatment options for emergencies
can cause peaked T waves in EKG
hypokalemia
most commonly caused by diuretic use and alcohol abuse
s/sx: heart palpitations, arrhythmias, fatigue, muscle pain, constipation, N/V
plasma K+ < 3.5 mEq/L (severe if < 2.5)
treatment options
avoid
dextrose-containing vehicles (may worsen low K+ by stimulating insulin release
most abundant
intracellular cation
in the body
normal range: 3.5-5 mEq/L
calcium
hypercalcemia
plasma Ca2+ > 14mg/dL
consider glucocorticoids to treat adrenal insufficiency
most cases are due to hyperparathyroidism or malignancy
hypocalcemia
s/sx: tetany, brittle and grooved nails, hair loss, dermatitis, eczema
available supplement options
normal range: 8.6-10.2 mg/dL
extracellular calcium = total serum calcium = bound + unbound calcium
calculations for correcting Ca
concentration of ionized Ca is regulated by interactions of PTH, phosphorus, VitD, and calcitonin
phosphorous
hypophosphatemia
risk factors: DKA, malnutrition, sepsis, alcohol abuse, diuretic use, antacid use
serum phosphorus <2.7 mg/dL
s/sx: acute respiratory failure, tissue hypoxia, decreased myocardial contractility, weakness, paresthesias, seizures, rhabdomyolysis
tx: administer IV potassium phosphate or sodium phosphate
normal range: 2.7-4.5 mg/dL
most abundant
intracellular anion
in the body
hyperphosphatemia
risk factors: renal failure, hemolysis, vitamin D toxicity
serum phosphorus >4.5 mg/dL
tx: administer oral phosphate binders
essential part of phospholipid cell membranes, nucleic acids, and phosphoproteins required for mitochondrial function
IV fluid distribution
