9: Fluids and Electrolytes Flashcards

1
Q

What is the composition and pH of normal saline?

A
  • Na: 154 mEq
  • Cl: 154 mEq

[pH is 5.5]

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2
Q

Which body fluid has the highest concentration of K+?

A

Saliva

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3
Q

What determines the plasma/interstitial and the intracellular/extracellular osmotic pressures?

A
  • Plasma/interstitial: Protein
  • Intracellular/extracellular: Sodium
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4
Q

What are the symptoms of hypernatremia?

A
  • Restlessness
  • Irritability
  • Seizures

[Usually from dehydration. Correct with D5 water slowly to avoid brain swelling.]

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5
Q

What should be used to replace fluid loss from the following sources?

  • Stomach
  • Pancreatic/biliary/small intestine
  • Large intestine
  • Generalized dehydration
A
  • Stomach: D5 1/2 NS with 20 mEq K+
  • Pancreatic/biliary/small intestine: Lactated ringer with HCO3-
  • Large intestine: Lactated ringer with K+
  • Generalized dehydration: Normal saline

[GI losses should generally be replaced cc for cc.]

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6
Q

What is the most common malignant and most common benign causes of hypercalcemia?

A
  • Malignant: Breast cancer
  • Benign: Hyperparathyroidism
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7
Q

What should one avoid administering to a patient with hypercalcemia?

A
  • Lactated ringer solution (contains Ca)
  • Thiazide diuretics (causes retention of calcium)
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8
Q

Why does hypochloremic, hypokalemic metabolic alkalosis from vomiting or nasogastric suctioning result in paradoxical aciduria?

A
  1. Loss of Cl- and H- ions from the stomach (hypochloremia and alkalosis)
  2. Loss of water causes kidney to reabsorb Na in exchange for K+ thus losing K+ (hypokalemia)
  3. Na+/H- exchanger activated in an effort to reabsorb water along with K+/H- exchanger in an effort to reabsorb K result in paradoxical aciduria
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9
Q

What is the best indicator of adequate volume replacement?

A

Urine output

[4 cc/kg/hr for 1st 10kg, 2 cc/kg/hr for 2nd 10kg, 1 cc/kg/hr for each kg after that. During open operations, fluid loss is 0.5-1.0 L/hr unless ther are measurable blood losses. Usually unecessary to replace blood lost unless it is >500cc.]

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10
Q

What is the treatment for hypercalcemia?

A
  • Normal saline at 200-300 cc/hr
  • Lasix

[For malignant disease, mithramycin, calcitonin, alendronic acid, and dialysis.]

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11
Q

What is the normal daily requirement of Na+ and K+?

A
  • Na: 1-2 mEq/kg/day
  • K: 0.5-1.0 mEq/kg/day
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12
Q

How much insensible fluid is lost each day?

A

10 cc/kg/day

[75% is lost from skin, 25% from respiratory tract.]

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13
Q

What are the symptoms of hypocalcemia?

A
  • Hyperreflexia
  • Chvostek’s sign (tapping face produces twitching)
  • Perioral tingling and numbness
  • Trousseau’s sign (carpopedal spasm)
  • Prolonged QT interval

[Calcium usually must be <8 or ionized calcium <4 for symptoms to manifest. Mg may need to be replaced in order to correct Ca.]

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14
Q

What is the formula for plasma osmolarity?

A

Plasma osmolarity = (2 x Na) + (Glucose / 18) + (BUN / 2.8)

[Normal plasma osmolarity is 280-295.]

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15
Q

Why is myoglobin nephrotoxic and what is the treatment?

A
  • Myoglobin is converted to ferrihemate in acidic environments which is toxic to renal cells
  • Treatment is alkalinization of the urine
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16
Q

What is the protein adjustment to calcium?

A

For every 1 gram decrease in protein (IE albumin), add 0.8 to Ca

17
Q

What are the drugs that can be given to treat hyperkalemia?

A
  • Calcium gluconate: Membrane stabilizer for heart to prevent arrhythmias
  • Sodium bicarbonate: Causes alkalosis, drives K+ into cells in exchange for H+
  • Insulin (10 units) and glucose (1 ampule of 50% dextrose): K+ driven into cells with glucose
  • Kayexalate: Draws K+ into large intestine for excretion

[Can also dialyze the patient.]

18
Q

High plasma levels of what can cause pseudohyponatremia?

A

Hyperglycemia

[For each 100 increment of glucose over normal, add 2 points to the Na value.]

19
Q

What is the treatment for tumor lysis syndrome?

A
  • Hydration is the best treatment
  • Rasburicase converts uric acid into inactive metabolite allantoin
  • Allopurinol decreases uric acid production
  • Diuretics
  • Alkalinization of urine
20
Q

How is vitamin D-synthesized in the body?

A
  1. It is made in the skin (UV light converts 7-dehydroxycholesterol to cholecalciferol)
  2. Cholecalciferol goes to liver for 25-OH and then the kidney for 1-OH yielding the active form of vitamin D
  3. The active form of vitamin D increases calcium-binding protein leading to increased intestinal Ca absorption
21
Q

What is the normal sodium concentration of sweat?

A

35-65 mEq

22
Q

What are the signs of the below conditions on ECG?

  • Hyperkalemia
  • Hypokalemia
A
  • Hyperkalemia: Peaked T-waves
  • Hypokalemia: Absent T-waves

[Hyperkalemia often occurs in renal failure. Hypokalemia often occurs in setting of overdiuresis.]

23
Q

What is the composition of lactated ringer solution?

A
  • Na: 130 mEq
  • K: 4 mEq
  • Cl: 109 mEq
  • Ca: 2.7 mEq
  • Bicarb: 28 mEq

[pH is 6.5]

24
Q

Which fluid type should be used to replace fluids after major adult gastrointestinal surgery?

A
  • During operation and continued for first 24 hours: Lactated ringer solution
  • After 24 hours: Switch to D5 1/2 NS with 20 mEq K+

[5% dextrose will stimulate insulin release, resulting in amino acid uptake and protein synthesis (also prevents protein catabolism). D5 1/2 NS @ 125 cc/hr provides 150g of glucose per day (525 kcal/day).]

25
Q

What are the causes of high anion gap acidosis?

A

“MUDPILES”

  • Methanol
  • Uremia
  • Diabetic ketoacidosis
  • Paraldehydes
  • Isonazid
  • Lactic acidosis
  • Ethylene glycol
  • Salicylates
26
Q

What are the below fluid types particularly rich in?

  • Saliva
  • Gastric
  • Pancreatic
  • Bile
A
  • Saliva: K+
  • Gastric: K+ and Cl-
  • Pancreatic: HCO3-
  • Bile: HCO3-
27
Q

What are the symptoms of hyponatremia?

A
  • Headaches
  • Nausea/Vomiting
  • Seizures

[Usually from fluid overload. Water restriction is first-line treatment for hyponatremia, then diuresis. Correct Na slowly (< 1 mEq/hr) to avoid central pontine myelinosis.]

28
Q

What is the formula for anion gap?

A

Anion gap = Na - (HCO3 + Cl)

[Normal anion gap is < 10-15]

29
Q

What is the breakdown of water composition in the human body?

A
  • 2/3 of a male’s (slightly less in females) body weight is water
    • 2/3 of water weight is intracellular (mostly muscle)
    • 1/3 of water weight is extracellular
      • 2/3 of extracellular water is interstitial
      • 1/3 of extracellular water is in plasma
30
Q

What are the causes of normal anion gap acidosis?

A

Usually loss of Na and bicarb (ileostomies and small bowel fistulas)

31
Q

What are the symptoms of hypercalcemia?

A
  • Stones: Renal or biliary stones
  • Bones: Bone pain
  • Groans: Abdominal pain, nausea vomiting
  • Thrones: Polyuria leading to dehydration
  • Psychiatric overtones: Lethargy, depression