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