CHAPTER 09- FLUIDS AND ELECTROLYTES.txt

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CHAPTER 09- FLUIDS AND ELECTROLYTES.txt
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  1. What % of the total body weight is water?
    • 1) Roughly 2/3 of total body weight is water (men)
    • 2) infants have a little more body water
    • 3) Women have a little less
  2. What percentages are in which compartments?
    • 1) 2/3 of water weight is intracellular (mostly muscle
    • 2) 1/3 of water is extracellular
    • 1- 2/3 of extracellular water is interstitial
    • 2- 1/3 of extracellular water is plasma
  3. What determines plasma/interstial compartment osmotic pressures?
    Proteins determine plasma/interstitial compartment osmotic pressures
  4. What determines intracellular/extracellular osmotic pressure?
    Na determines intracellular/extracellular osmotic pressure
  5. Volume overload:
    • 1) most comon cause is iatrogenic
    • 2) first sign is weight gain
  6. What cellular process can release a significant amount of H20
    cellular catabolism
  7. 0.9% normal saline:
    Na 154 and Cl 154
  8. Lactate Ringer's solution:
    • 1) LR; ionic composition of plasma:
    • 2)
    • Na-130
    • K-4
    • Ca- 2.7
    • Cl- 109
    • Bicarb- 28
  9. Formula for plasma osmolarity:
    (2 x Na)+(glucose/18)+(BUN/2.8)

    Normal= 280-295
  10. Estimates of volume replacement:
    • 1) 4cc/kg/h for 1st 10kg
    • 2) 2cc/kg/h for 2nd 10kg
    • 3) 1cc/kg/hr for each kg after that
    • 4) best indicator of adequate volume replacement is urine output
  11. What is the fluid loss in open abdominal operations:
    During open abdominal operations, fluid loss is 0.5-1.0L/h unless there are measurable blood losses
  12. At what point do you need to replace blood loss?
    usually do not have to replace blood loss unless it is >500cc
  13. Insensible fluid losses:
    • 1) 10cc/kg/day
    • 1- 75% skin
    • 2- 25% respiratory
    • 3- pure water
  14. IV replacement after major adult gastrointestinal surgery:
    • 1) during operation and 1st 24 hours, use LR
    • 2) After 24 hours, switch to D5 1/2 NS with 20mEq K
    • 1- 5% dextrose will stimulate insulin release, resulting in amino acid uptake and protein synthesis (also prevents protein catabolism)
    • 2- D5 1/2NS @ 125/h provides 150g glucose per day (525kcal/day)
  15. GI fluid secretion:
    • Stomach: 1-2L/day
    • Biliary System: 500-1,000 ml/day
    • Pancreas: 500-1,000 ml/day
    • Duodenum: 500-1,000 ml/day
  16. Normal K+ requirement:
    Normal Na+ requirement:
    • Normal K+ requirement: 0.5-1 mEq/kg/day
    • Normal Na+ requirement: 1-2 mEq/kg/day
  17. Electrolyte losses:
    Sweat-
    Saliva-
    Stomach-
    Pancreas-
    Bile-
    Small Intestine-
    Large Intestine-
    • Sweat- hypotonic
    • Saliva- K+ (highest concentration of K+ in the body)
    • Stomach- H+ and Cl-
    • Pancreas: HCO3-
    • Bile- HCO3-
    • Small Intestine- HCO3-, K+
    • Large Intestine- K+
  18. What do you replace gastric losses with?
    Gastric losses- replacement is D5 1/2NS with 20mg K+
  19. What do you replace pancreatic/biliary/small intestine losses with?
    replacement is LR with HCO3-
  20. What do you replace Large intestine (diarrhea) losses with?
    replacement is LR with K+
  21. How is volume of GI losses replaced?
    GI losses- should generally be replaced cc/cc
  22. What should urine output be kept at?
    Urine output- should be kept at least 0.5cc/kg/h; should not be replaced, usually a sign of normal postoperative diuresis
  23. Potassium:
    1) Normal: 3.5-5

    • 2) Hyperkalemia- peaked T waves initial finding on EKG
    • 1- calcium gluconate (membrane stabilizer for the heart)
    • 2- sodium bicarbonate (causes alkalosis, K enters cell in exchange for H)
    • 3- 10U insulin and 1 ampule of 50% dextrose (K driven into cells along with glucose)
    • 4- kayexalate
    • 5- dialysis if refractory
    • 3) Hypokalemia- T waves disappear
    • 1- may need to replace Mg+ before you can correct K+
  24. Sodium:
    1) Normal: 135-145

    • 2) Hypernatremia- restlessness, irritability, ataxia, seizures
    • 3) Correct with D5 water slowly to avoid brain swelling
    • 4) Total free water deficit =
    • 0.6 x patient's weight (kg) x [(Na+/140)-1]
    • 5) Water Requirement:
    • [desired change in Na+ over 1 day x TBW]/
    • [desired Na+ after giving the water requirement]
    • 1- TBW (total body water)= 0.6 x patient's weight (kg)
    • 2- Change Na more than 0.7mEq/h (16mEq/day for below)
    • 3- for the equation above, if the Na was 165 for a 70kg man: (16x42)/149= 4.5L

    • 4) Hyponatremia- headaches, delirium, seizures, nausea,vomiting
    • 1- Na deficit= 0.6 x (weight in kg) x (140-Na)
    • 2- Water restriction is the first treatment of hyponatremia, then diuresis, then NaCl replacement
    • 3- Correct Na slowly to avoid central pontine myelinosis (no more than 1mEq/h)
    • 4- Hyperglycemia can cause pseudohyponatremia- for each 100 increment of glucose over normal, add 2 points to the Na value
    • 5- SIADH results in hyponatremia
  25. Calcium
    • 1) Normal: 8.5-10; Normal ionized Ca- 4.4-5.5
    • 2) Hypercalcemia (Ca usually >13 or ionized >6-7)- causes lethargic state
    • 1- breast Ca most common malignant cause
    • 2- no lactate ringer's (contains Ca2+)
    • 3- no thiazide diurectics (these retain Ca2+)
    • 4- Tx: NS at 200-300cc/h, Lasix
    • 1- for malignant disease- mithramycin, calcitonin, aledronic acid, dialysis

    • 3) Hypocalcemia (Ca usually <8 or ionized Ca <4)- 1- hyperreflexia
    • 2- Chvostek's sign (tapping on face produces twitching)
    • 3- perioral tingling and numbness
    • 4- Trousseau's sign (carpopedial spasm)
    • 5- prolonged QT interval
    • 4) may need to correct Mg before being able to correct Ca
    • 5) Protein adjustment for calcium- for every 1g decrease in protein, add 0.8 to Ca
  26. Magnesium:
    • 1) Normal: 2.0-2.7
    • 2) Hypermagnesemia- causes lethargic state; burn, trauma, and renal dialysis patients.
    • 1- Tx: calcium
    • 3) Hypomagnesemia- signs similar to hypocalcemia
  27. Metabolic Acidosis: (following slides):
  28. Anion gap:
    Anion gap = Na - (HCO3 + Cl)

    Normal <10-15
  29. Anion gap acidosis:
    "MUDPILES"

    • Methanol
    • Uremia
    • Diabetic ketoacidosis
    • Paraldehydes
    • Isoniazide
    • Lactic acidosis
    • Ethylene glycol
    • Salicylates
  30. Normal gap acidosis:
    1) usually due to loss of Na/HCO3- (ileostomies, small bowel fistulas)
  31. Treatment of metabolic acidosis:
    • 1) keep pH > 7.2 with bicarbonate
    • 2) Severely decreased pH can affect myocardial contractility
  32. Metabolic alkalosis:
    • 1) usually a contraction alkalosis
    • 2) Nasogastric suction- results in hypochloremic, hypokalemic, metabolic alkalosis, and paradoxical aciduria
    • 3) Loss of Cl- and H ion from stomach secondary to nasogastric tube (hypochloremia and alkalosis)
    • 4) Loss of water causes kidney to reabsorb Na in exachange for K (Na/K ATPase), thus losing K+ (hypokalemia)
    • 5) Na/H exchanger activated in an effort to reabsorb water along with K/H exchanger in an effort to reabsorb K--> results in paradoxical aciduria
  33. Acid-Base Balance:
    • Respiratory acidosis:
    • pH: low
    • CO2: high
    • HCO3: high

    • Respiratory alkalosis:
    • pH: high
    • CO2: low
    • HCO3: low

    • Metabolic acidosis:
    • pH: low
    • CO2: low
    • HCO3: low

    • Metabolic alkalosis:
    • pH: high
    • CO2: high
    • HCO3: high
  34. Henderson-Hesselbach equation:
    pH= pK + log [HCO3-]/[CO2]

    Ratio of base to acid (HCO3- to CO2) of 20:1 = pH of 7.4
  35. Acute renal failure:
    FeNa = (urine Na/Cr) / (plasma Na/Cr) = best test for azotemia

    • Prerenal:
    • 1- FeNa <1%
    • 2- urine Na<20
    • 3) BUN/Cr ratio >20
    • 4- Urine osmolality >500mOsm

    70% of renal mass must be damaged before theres an increase in BUN + Cr
  36. Contrast dyes-
    1) volume expansion best prevents renal damage: HCO3- and N-acetylcysteine gtt
  37. Myoglobin
    • 1) converted to ferrihemate in acidic environment, which is toxic to renal cells
    • 2) Tx: alkalinize urine
  38. Tumor lysis syndrome:
    • 1) release of purines and pyrimidines leads to increased PO4 and uric acid, decreased Ca
    • 2) Can result in:
    • 1- increased BUN and Cr
    • 2- EKG changes
    • 3) Tx:
    • 1- hydration
    • 2- diuretics
    • 3- allopurinol (decreased uric acid production)
    • 4- alkalinization of urine
  39. Vitamin D
    • cholecalciferol
    • 2) made in skin (UV sunlight) from 7-dehydrocholesterol
    • 3) goes to liver for (25-OH), then kidney for (1-OH). This creates active form of vitamin D
    • 4) active form of vitamin D- increases calcium-binding protein, leading to increased intestinal calcium absorption
  40. Chronic renal failure:
    • 1) decreased active vitamin D (decreased 1-OH hydroxylation)--> decreases Ca reabsorption from gut (decreased Ca-binding protein)
    • 2) Anemia- from low erythropoietin
  41. See image on pg 42: Multiple effects of increased angiotensin II release in response to the stimulus of decreased extracellular volume
  42. Transferrin:
    transporter of iron
  43. Ferritin
    storage form of iron

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