Electrolytes LH

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Anonymous
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45363
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Electrolytes LH
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2010-10-27 01:21:37
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Electrolytes Na Cl Hyponatremia Hypernatremia
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Electrolytes LH
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  1. Atrial Natriuretic Peptide (ANP)
    • DIURETIC (Na+ and Water)
    • released by the heart in response to stretch of atria (i.e. high BP)
    • causes a decrease in Na and water reabsorption and overall drop in BP
  2. aldosterone
    • ANTIDIURETIC
    • increases Na retention and increases potassium excretion
  3. ADH, Antidiuretic hormone/ AVP arginine vasopressin
    • ANTIDIURETIC
    • promotes water reabsorption in the tubules by increasing number of aquaporins
  4. What is the physiological response to fluid depletion
  5. apparent ECF osmolality formula & when is it valid
    2[Na+] + 2[k+] + [glucose] + [urea]

    is only valid if the patient doesnt have hyperproteinureia or hyperlipidemia
  6. Major electrolytes of ICF and ECT and app. volumes
    • ICF: 28L, K+, phosphate, Proteins
    • ECF: 14L, Na, Cl, HCO3-
  7. response to dehydration
    • post. pit. to secrete ADH --> water reabsorption
    • adrenal glands secrete aldosterone --> Na reabsorption
  8. what happens when you lose ECF pure water only + symptoms
    pure water is lost , Na+ content is the same, thus [Na+] increases --> changes osmolality of ECF --> ICF water travels to the ECF to balance osmolality. loss of ICF

    • SYMPTOMS:
    • cell dysfunction, muscular cell dysfunction --> lethargy, CNS cell dysfunction --> confusion, coma
  9. what happens when you lose isotonic Water + Na+
    changes the ECF only because there is no osmolality difference, osmolality of both compartments remain the same. There is no net water movement. Only the ECF loses volume.i.e. hypovolemia

    • SYMPTOMS
    • circulatory collapse, renal shutdown, shock
  10. 3 types of dehydration
    • Hypertonic, >water loss than Na+
    • isotonic water=na+ loss
    • hypotonic >Na loss than water
  11. Presentation of dehydration and causes
    presentation: hypernatremia, hyperosmolality, decrease volume in ECF and ICF

    • CAUSES:
    • Inadequate intake:
    • Abnormal loss:
    • - lungs, skin, gut (diarrhea)
    • - renal tract (diabestes insipidus which is a deficiency of ADH)
    • - Li therapy, increase in osmotic load (alot of glucose, needs a lot of water to be excreted), DM, diuretics
    • - third space losses
  12. causes of water excess
    • excessive intake (polydispia)
    • - oral or parenteral (e.g. hypotonic IV infusion)
    • renal retention
    • - XS ADH secretion - SIADH
    • - hypoadrenalism
    • - hypothyroidism
  13. water intoxication
    • - dilutional hyponatremia and hyposmolality of the ECF
    • - expansion of both ICF and ECF
    • - Na+ falls ~ 120-125mmol/L --> nausea, vomiting, abdominal cramps
    • - seizures & coma result from the changes in water content of brain, i.e. cerebral oedema
  14. The three types of hyponatremia
    • 1. hypovolemic hyponatremia
    • - low TBW & Na with a relatively greater decrease in Na & therefore decreased ECF.
    • - due to renal or extra renal Na+ loss
    • - renal: urine [Na+] > 20mmol/L
    • - extra renal:urine [Na+]<20mmol/L
    • - no oedema

    • 2. Euvolemic hyponatremia (dilutional)
    • - high TBW with near normal total body Na therefore normal ECF
    • - due to excessive water retention
    • causes:
    • - acute: post-op water admin
    • - chronic: antiduiretic drugs, opiates, SIADH


    • 3. hypervolemic hyponatremia
    • - high total body Na (therefore high ECF) with a relatively greater increase in TBW.
  15. SIADH
    • syndrome of innappropriate ADH secretion --> hyponatremia
    • - secretion of ADH without hypernatremia or fluid depletion due to failure of the neg. feedback system that regulates ADH release

    • signs:
    • - low plasma Na
    • - high urine osmolality
  16. hyperosmolar hyponatremia
    • due to other substances into the plasma and causing a shift of water from ICF to ECF.
    • e.g. hyperglycemia in uncontrolled DM
    • - assessed by calculating osmolal gap
  17. pseudohyponatremia

    * CLARIFY**
    • fake hyponatremia due to hyperlipidemia and hyperproteinemia occupying plasma volume
  18. causes of hypernatremia
    • oral intake (sea water near-drowning, salt tablets, hypertonic NaCl (rare)
    • parenteral
    • renal retention: renal failure, cushings syndrome (XS aldosterone), 2ndary hyperaldosteronism
    • pregnancy

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