Chapter 21 - Fluids/Electrolytes Flashcards
Describe and approach to hyponatremia.
1) True/False (sOsm)
2) H2O Excretion normal/impaired (diuretic/low GFR)
3) ADH Active (Uosm > 100) or inactive (<100)
4) If inactive (appropriate) - polydipsia/beer potomania
5) If active - volume assessment
a) Hypovolemic - renal or extrarenal (FeNa)
b) Euvolemic - SIADH/endocrine/osmostat
c) Hypervolemia - CHF, cirrhosis vs renal failure (FeNa). SIADH possible.
What is the treatment of acute symptomatic hyponatremia?
3% NaCl
Dose 25-150 mL
Bolus 100-150 if sz, infusion if symptomatic
Repeat q10min
Goal to raise Na 6-8mmol/L
Fluid restrict
Principles:
Defend Intravascular Volume
Don’t Allow Worsening of Na
Avoid Overcorrection
Correct Underlying Cause
DDAVP 1-2mcg q8h iv/sc to avoid massive shifts
What is the major complication of overcorrection of hyponatremia and how is it managed?
Osmotic demyelination syndrome
May present up to 7 days post event.
Symptoms: ataxia, quadrapelegia, cranial nerve palsies, locked in syndrome
Risk factors: elderly, malnourished, chronic low Na, hypokalemia
Treat with relowering of Na and supportive measures.
What are some symptoms of hyponatremia?
Twitching, weakness, hemiparesis, ataxia, coma, seizures.
What are symptoms of hypernatremia?
Irritability, seizure, increased tone, coma
Describe the urine findings for diabetes insipidus
Low urine osmolality (200-300)
Urine sodium 60-100
Inability to concentrate urine due to ADH deficiency (central - reduced production from pituitary, nephrogenic - ADH resistance)
Central will respond to ADH stimulation (Vasopressin challenge; 5U subcut will cause urine osm to increase to > 800 under water deprivation)
What are the causes of hypernatremia?
Decreased intake, increased Na intake, hormone (cushing/aldostromism), water loss, drug effects
What is the formula for free water deficit?
H2O def = (mNa/nNa) - 1
m = measured
n = normal
Generally 1L deficit will raise Na by 3-5mmol/L
How does acidosis affect potassium?
For every 0.1 increase in pH potassium decreases by 0.5
Each 1 mmol/L of potassium serum change is equivalent to body deficit/surplus of 100-200 meq
List EKG findings in hyperkalemia
- 5-7.5: Long PR, Peaked Twave, Short QTc
- 5-8: flat p, QRS prolongation
10-12: complete QRS degredation
List treatments of hyperkalemia in order of time to effect.
Calcium Chloride (1amp)/Gluc (2-3amp)
Bicarb (1-2amp)
Ventolin (5mg)
Insulin/D50W (10/1)
Lasix (40)
Sodium Polystyrene (25-50g)
*Dialysis
What are the causes of hypocalcemia?
Malabsorption: VitD Deficiency
Increased excretion: Diuretics, Renal failure, EtOH
Metabolic: Shock, Sepsis, Pancreatitis, Low Mg, Tranfusion
Endocrine: HypoPTH/PseudoPTH
Drugs (phosphates, gent/tobramycin, UFH, protamine, glucagon, steroids, Mg, Norepi)
What are causes of hypercalcemia?
Malignancy
Endocrinopathy (hyperT4, Pheo, adrenal insuff, acromegaly, hyperPTH)
Drug (TZD, Li)
Granulomatous Disease (sarcoid, TB, histo, coccidiomycosis)
Immoblization
What are clinical manifestations of hypocalcemia?
Weakness, fatigue
CNS - memory, confusion, psychosis, EPS, seizures
Derm: brittle hair, hyperpigmentation, dry skin
CV: CHF, vasoconstriction
MSK: spasms, cramps, weakness
Osteomalacia, cataracts, reduced insulin, rickets
What are clinic manifestations of hypercalcemia?
Stones (nephrolithiasis)
Bones (osteolysis)
Moans (psychosis)
Groans (PUD, pancreatitis, constipation)
