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45 Cards in this Set

  • Front
  • Back
What does total Na+ represent?
ECF volume
What does [Na+] represent?
ICF volume
What electrolyte abnormality causes edema?
Na+ retention by kidneys
What abnormality does hyponatremia represent?
Water retention by kidneys
What abnormality does hypernatremia represent?
Water deficit (decreased intake)
What are causes of reduced effective circulating blood volume? (3)
Low intravascular volume (trauma, shock etc.)
Poor heart function (Heart failure)
Inappropriate peripheral arterial dilatation (Liver failure)
What is the effect of reduced effective circulating volume on the kidneys and what is the mechanism for this?
Sodium Retention by Kidneys
Activations of Renin system -> Angiotensin causes Na+ resorption in proximal tubule and activations of aldosterone -> aldosterone causes Na+ reabsorption in the CCD
What are causes of Sodium Retention by the Kidneys? (2)
Low effective circulating volume
Kidney injury
What are signs of Sodium excess/ECF volume expansion? (6)
Weight Gain
Peripheral edema
Increased JVP (except in liver failure when albumin is decreased)
Pulmonary edema
Ascites (increased portal flow)
Pleural effusions
How is sodium excess/ECF volume expansion treated? (3)
Treat underlying cause (difficult)
Restrict dietary sodium (<1500mg/day)
Diuretics: Thiazide, Furosemide, K+ sparing (amiloride, spirnolactone)
What are common uses of spirnolactone, amiloride, thiazide and furosemide?
Spirnolactone: CHF, hypokalemia from other diuretics
Amiloride: hypokalemia from other diuretics
Thiazide: Excess sodium, hypertension, Kidney stones
Furosemide: pulmonary edema (IV), Excess sodium
What are the mechanisms of action of spirnolactone, amiloride, thiazide and furosemide?
spirnolactone: aldosterone antagonist
amiloride: blocks Na+ channels in CCD
Thiazide: prevents Na+ resorption in DCT
Furosemide: prevents Na+ resorption in LOH
What are broad categories of causes of sodium depletion/reduced ECF volume? (3)
GI losses - diarrhea, vomitting (indirect through kidney)
Urinary losses - diuretics, aldosterone deficiency, interstitial/tubular kidney disease, osmotic diuresis (hyperglycemia)
Skin losses - sweating, burns
What are signs/symptoms of sodium depletion/reduced ECF volume? (6)
Low JVP
Tachycardia, postural tachycardia
Hypotension, postural hypotension
Weight loss
Poor skin turgor
Low urine [Na+] and [Cl-]
What are treatments for sodium depletion/reduced ECF volume? (urgent/less urgent)
Urgent - IV saline
Less urgent - oral rehydration fluid, salty food, stop diuretic
What are broad categories of causes of hypokalemia? (3)
Shift in K+ into cells - Insulin, Beta 2 agonists
GI losses - diahrrea
Urine Loss - High aldosterone, diuretics, vomitting, primary hyperaldosteronism
What are signs/symptoms of hypkalemia (<3)? (3)
Muscle weakness
Cardiac arrhytmias (VPB, VF, VT)
Inhibition of insulin secretion
How do you manage hypokalemia? (Acute, Chronic)
Acute - Oral or IV KCl
Chronic/prevention: High K+ food, K+ sparing diuretics
What are broad categories of causes of hyperkalemia? (2)
Shift of K+ out of cells - insulin deficiency, muscle necrosis, hemolysis
Impaired kidney excretion - low flow to CCD (low ECFV, low GFR), low aldosterone (adrenal disease, ACEi/ARBs, K+ sparing diuretics, tubular dysfunction)
What are signs/symptoms of hyperkalemia? (3)
Muscle weakness/stiffness
ECG changes: small pwaves, broad QRS, peaked T waves
Arrhythmias: sinus bradycardia, heart block, asystole, junctional rhythms
How do you treat hyperkalemia? (3 steps)
1) Shift K+ into cells (in 15min): Insulin IV, beta 2 agonist
2) Stabilize ECG: calcium gluconate IV
3) Remove K+ from body: saline+furosemide, dialysis
At what value of K+ can hyperkalemia cause death?
>7mmol
What is the physiologic mechanism of correcting hypernatremia?
Osmoreceptors sense hypernatremia and activate ADH and thrist resulting in water retention
What is the physiologic mechanism of correcting hyponatremia?
Osmoreceptors not stiumlated so ADH is inhibited resulting in large amounts of water being excreted
What are non-osmotic factors which can stimulate release of ADH? (7)
Low BP or effective circulating volume
Pain/stress/surgery
Hormones (pregnancy, low cortisol, hypothyroid)
Drugs
Brain disease (stroke, infection, etc.)
Chest disease (vagal afferent stimulation)
Ectopic secretions by cancer (SIADH)
What are signs/symptoms of water excess (hyponatremia)? (Acute, Chronic)
Acute - brain cell swelling: headache, confusion, seizures, coma, death
Chronic - nothing
How do you treat water excess (hyponatremia)? (3)
Remove underlying cause
Restrict fluid intake
Hypertonic saline (acute=quickly, chronic=slowly)
What are causes of water depletion (hypernatremia)? (2)
Failure to drink (babies, elderly, coma)
Excess losses (hyperglycemia, diabetes insipidus)
What are signs/symptoms of water depletion (hypernatremia)? (acute, chronic)
Thirst in both
Acute - CNS changes (decreased LOC, seizures)
Chronic - none specific
What is normal pH, C02 and HC03?
7.4, 40, 25
What constitutes an "acidic" and "basic" value for pH, C02 and HC03?
pH: acidic <7.4, basic>7.4
C02: acidic >40, basic <40
HC03: acidic <25, basic >25
What changes occur in pH, C02 and HC03 in compensated 1) respiratory acidosis? 2)metabolic acidosis? 3)respiratory alkalosis? 4)metabolic alkalosis?
1) pH<7.4, C02 >40, HC03 >25
2) pH<7.4, C02<40, HC03<25
3) pH>7.4, C02<40, HCO3<25
4) pH>7.4, CO2>40, HCO3>25
What are 2 main mechanisms that produce metabolic alkalosis?
Addition of bicarbonate to ECF: vomitting, diuretics (increased NH4 excretion) exogenous (citrate, NaHCO3)
Failure of bicarbonate excretion by kidney: Hypokalemia (stimulates HCO3 resorption), Volume depletion (reduced GFR, AngII stimulated HCO3 resorption)
Why does hypokalemia cause HCO3 resorption by the kidneys?
When K+ leaves kidney cells it is replaced by H+ -> cell interprets as acidosis so increases NH4 excretion -> results in more HCO3 resorption
What are the five steps used to solve acid-base problems?
1) identify the main disturbance
2) predict compensatory response
3) Compare predicted to actual compensation
4) Calculate anion gap
5) Calculate osmolar gap (if appropriate)
What is normal compensation for an acid base disturbance?
1:1 change in HCO3:CO2 in the same direction
How do you calculate Anion Gap and what is a normal value for this?
[Na+] - ([Cl-] + [HCO3-])
Normal = 12
How do you calculate osmolar gap and what is a normal value?
Measured Gap - Calculated Gap
=Measured Gap - (2 x [Na+] + [glucose] + [urea])
Normal = <10
What are causes of anion gap acidosis?
Ketoacidosis
Aspirin
Renal failure
Methanol poisoning
Ethylene glycol poisoning
Lactic acidosis
What are causes of an increased osmolar gap?
Methanol and ethanol poisoning
What are causes of normal anion gap acidosis? (3)
Kidney disease (reduced NH4+ excretion)
Diarrhea
Massive saline infusion (dilution)
What causes lactic acidosis? (4)
Anaerobic metabolism of glucose
Shock state
Intense exercise
Liver failure (liver removes lactate normally)
What is the significance of metabolic acidosis?
Diagnosis and prognosis of life-threatening illnesses
How do you treat metabolic acidosis? (1)
HCO3 if pH <7.0
How do you treat septic shock? (3)
IV saline vigorously
Antibiotics
Inotropes if not correcting