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Electrolyte Disorders

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Electrolyte Disorders WS04111: WTD3 Water Metabolism Water intake regulated by: Thirst is the response to water loss ADH release center is close to the thirst center ... – PowerPoint PPT presentation

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Title: Electrolyte Disorders


1
Electrolyte Disorders
  • WS04111 WTD3

2
Water Metabolism
  • Water intake regulated by
  • Thirst is the response to water loss
  • ADH release center is close to the thirst center
  • Water loss regulated by
  • Proximal renal tubular absorption
  • (reabsorbs 125 L/day of the 200 L/ day
    filtered by glomerulus)
  • Loop of Henle- absorbs sodium and dilutes urine
    (only sodium is reabsorbed)
  • Collecting duct- controlled by ADH- affects the
    total amount of urine excreted

3
Sodium Imbalance Hyponatremia (Low Sodium)
(fig.21-1)
  • Hypovolemia-
  • Dehydration/ Diarrhea/Vomiting
  • Renal Salt loss-
  • Diuretics/ ACE inhibitors
  • Hypervolemic-
  • CHF/ Liver disease/
  • Nephrotic syndrome/ ESRD
  • (ESRD end stage renal disease)

4
Sodium Imbalance Hyponatremia Signs and Symptoms
  • Mild ones (130-135) usually asymptomatic
  • (125-130) Nausea and malaise
  • (115-120) Headache/ Lethargy/ Disorientation
  • Red flag seizure/ comagt cardiac arrest/ death

5
Sodium Imbalance Hyponatremia- Treatment
  • Replace fluid with iv-0.45 sodium chloride
  • (half normal saline)
  • Asymptomatic cases-
  • Water restirction
  • Fludrocortisone

6
Hypernatremia
  • Only when sodium levels are greater than 155-
    clinically significant effects are seen
  • Decreased fluid intake
  • Increased skin loss
  • Increased GI loss (due to loss of water)
  • Renal- osmotic diuresis- (hyperglycemia)/ lack
    of ADH
  • Renal- drugs- lithium

7
Hypernatremia- symptoms and signs
  • Depression, confusion, coma, convulsions
  • Therapy Free water by mouth
  • IV 5 dextrose
  • Vasopressin/ Thiazides (increase proximal
    tubular reabsorption of water- reduces water
    delivery to distal tubule and helps)

8
Sodium Metabolism
  • Primary osmotic agent (mostly ECF)
  • Distal tubule and collecting duct are major
    regulators of urinary sodium output
  • ?Hormones- Aldosterone (increases sodium
    reabsorption) controlled by Renin- Angiotensin
  • Atrial natriuretic peptide/ Dopamine/
    Prostaglandins- inhibits Na reabsorption
  • CHF-Liver-Nephrotic syndrome-CRF- Steroid- all
    lead to Na retention
  • Urine sodium excretion less than 20 mEq/L

9
Edema Therapy
  • Restrict dietary sodium (lt1 g)
  • Diuretis- loop diuretics- lasix-potassium
    sparing- aldosterone antagonists (Aldactone)

10
Electrolyte Disorders
  • Potassium Metabolism

11
Potassium Basics
  • Primarily intracellular (3000 mEq)
  • Extracellular (65 mEq)
  • Normal dietary intake 60-90 mEq/day
  • Kidney preserves potassium homeostasis
  • Potassium must be driven into the cells-
  • Insulin/ Epinephrine help the drive
  • Renal- mostly excreted in distal tubule
  • (controlled by aldosterone)
  • More sodium delivered to the tubules more
    potassium is excreted

12
Hypokalemia (low K)
  • Less than 3.5 mEq/L
  • GI causes inadequate intake (lt10mEq/day)
  • diarrhea/ vomiting (loss of volume
  • Renin-Angiotensin-Aldosterone-leads to
  • urinaryK loss)
  • K redistribution Insulin therapy/ Epinephrine/
    Folic acid/ B12 therapy/ High bicarb intake/
    Periodic paralysis in Asians thyroid related
  • defective epinephrine sensitivity

13
Hypokalemia (low K)
  • Renal causes Diuretics/ Penicillins
  • Adrenal tumors-Aldosteronism/ ectopic ACTH/
    Licorice (anise) ingestion- steroid like
    substance- low K/ HTN/ alkalosis
  • Tobacco chewing- same as above
  • Renin tumors/ Renal artery stenosis
  • CHF
  • Magnesium depletion leads to tubular K wasting

14
Hypokalemia signs and symptoms
  • Neuro-muscular- weakness/ paralysis/
    constipation/ ileus/ decreased reflexes/
    rhabdomyolysis
  • Cardiac- arrhythmias (if on digoxinlasix)/ ECG-
    low amplitude T wave/ depressed ST segment
  • Endoctine- pancreatic insulin release

15
Hypokalemia Therapy
  • Check serum K level
  • Administer potassium chloride- iv / oral
  • 20 mEq oral/day

16
Hyperkalemia
  • Serum K levels greater than 5.5 mEq/L
  • Causes- Rhabdomyolysis/ tissue trauma/ Acidosis/
  • Renal failure/
  • Aldosterone deficiency- lead nephropathy, ACEi
    therapy/ Addisons disease

17
Hyperkalemia Signs and Symptoms
  • Dangerous!
  • ECG changes happen but not diagnostic (only at
    high levels more than 6.5 mEq/L)
  • Emergency treatment Calcium/ Insulin/ beta
    stimulants/ dialysis/ Resins

18
Electrolyte Disorders
  • Calcium Metabolism

19
Hypocalcemia
  • Most common cause- advanced CRF/CKD (decreased
    vit D3 and hyperphosphatemia)
  • Magnesium depletion aggravates low calcium
    symptoms

20
Hypocalcemia
  • Affects muscles and heart
  • Muscle spasms-tetany
  • Laryngospasms/ oral numbness and tingling
  • Chvosteks sign/ Trousseaus sign
  • IV Calcium gluconate thrapy
  • Oral calcium and vit D therapy

21
Hypercalcemia More than 12 mg/dL
  • Hyperparathyroidism/ Cancer related
  • Thiazide diuretics
  • Milk-Alkali excess- Tums for calcium use
  • SS Constipation/ Vomiting/ Anorexia/ peptic
    ulcer/ renal stones/
  • CNS- drowsiness, lethargy, convulsions, coma
  • Medical emergency

22
Electrolyte Disorders
  • Phosphate Metabolism

23
Phosphate Basics
  • Dynamic requirement for cell activity (ATP)
  • Main intracellular buffer
  • Acid-base action (H and P exchange)
  • 85 in bone
  • Dietary intake 1200 mg/day-
  • 800 mg excreted in urine, 400 in feces
  • PTH regulates P excretion by proximal renal
    tubule

24
Hypophopshatemia
  • Dietary lack- rare (starvation)
  • Antacid abuse- binds phosphate in the gut
  • Respiratory alkalosis
  • Sepsis- due to impaired WBC chemotaxis
  • Renal Diabetes/
  • Excess PTH increases urine phosphate loss
  • Alcoholics- reduced renal threshold

25
Hypophopshatemia-features
  • CNS- coma, convulsions, peripheral neuritis
  • Blood- rare (hemolytic anemia)
  • Muscular- ATP deficits- muscle pain
  • (seen in alcoholics)
  • Bone- increased bone resoprtion
  • Increased urine phosphate levels
  • (more than 100 mg/L) suggests renal causes
  • Treat with oral phosphate 1500-2000 mg/day

26
Hyperphosphatemia
  • Renal failure-
  • Acute rhabdomyolysis
  • Tumor lysis
  • Hypoparathyroid

27
Hyperphosphatemia features
  • Hypocalcemia features-low BP
  • Renal osteodystrophy
  • Calcification of soft tissues
  • Increased risk of cardiovascular events
  • Therapy- dialysis/
  • Oral phosphorus binders
  • calcium carbonate 500 mg thrice daily
  • sevelamer hydrochloride 800-1600 mg thrice
    daily with meals (adv. No calcium!)
  • Lanthanum carbonate can also be used.

28
Magnesium Basics
  • Second most abundant intracellular cation (K is
    first)
  • 50 stored in bone, rest in muscles, less than
    1 in body fluids
  • Acts on myoneural junctions/
  • cardiac rhythm defects
  • Kidney conserves magnesium
  • Plasma levels 1.5-2.5 mEq/L

29
Hypomagnesemia
  • Malabsorption
  • Renal- tubular dysfunction
  • Drugs-thiazides/lasix/ antibiotics
  • Hyperaldosteronism

30
Hypomagnesemia- features
  • Muscle twitiching, tremors, weakness
  • Affects renal K reabsorption
  • leads to hypokalemia
  • Hypocalcemia and hpokalemia may be associated
    conditions
  • Therapy- oral magnesium- 250-500 mg /day in
    divided doses

31
Hypermagnesemia
  • Seen in advanced renal disease
  • Iatrogenic-laxatives/antacids
  • Therapy of toxemia of pregnancy
  • Features- muscle weakness, depressed tendon
    reflexes, ileus, urine retention, low BP
  • Lab- low serum Calcium/ ECG changes
  • Therapy- calcium- antagonist for magnesium

32
Hydrogen ion issues
  • Henderson-Hasselbalch!
  • (Normal HCO3- 24/Pco2-40)
  • pH 6.1log HCO3
  • 0.3xPco2
  • Extracellular pH- 7.4/ Intracellular- 7.0-7.2
  • Normal metabolism generates- carbonic acid and
    non-carbonic acids- acetoacetate/ ketone
    (beta-hydroxy butyric acid)/sulfuric and
    phosphoric acids
  • Carbonic acid mostly exhaled as CO2
  • Non carbonic acids excreted by kidneys
  • (1 mEq/Kg body wt.)
  • Usually require hospital referral
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