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Fluid and Electrolytes

  1. What is the normal serum osmolality?
    275-290 mOsm/kg
  2. What is the equation to calculate serum osmolality?
    2[Na] + (Glu/18) + (BUN/2.8)
  3. What is the normal serum sodium concentration?
    135-145 mEq/L
  4. What is the norma serum level of glucose?
    70-110 mg/dL
  5. What is the normal serum level for BUN?
    5-20 mg/dL
  6. What creates oncotic pressure?
    plasma proteins
  7. What function does aldosterone have?
    • secreted when plasma volume is low (perfusion pressure)
    • Enhances sodium reabsorption in the distal tubules (water follows)
    • potassium goes out as sodium comes in
  8. What is the fx of Antidiuretic Hormone (ADH)?
    • secreted when osmolality is high
    • regulates fluid and electrolyte intake (think thirst)
    • regulates reabsorption of free water in distal tubules
    • NOT part of RAAS!!!!
  9. What are sensible and insensible water gains and losses?
    • sensible:
    • food, fluids
    • urine, intestinal
    • insensible:
    • water of oxidation (Krebs cycle)
    • lungs, skin, feces
  10. What can be used to assess fluid levels?
    • I/O
    • wt
    • BP (not very good, by the time BP decreases, you have problems)
    • HR
    • heart sounds (S3 - fluid overload)
    • JVD
    • CVP
    • PCWP
    • edema/skin turgor
    • electrolytes (Na, BUN, SCr - BUN/SCr ratio)
    • Hct
    • specific gravity
  11. What BUN/SCr ratio means dehydration?
    if BUN/SCr = >20
  12. What is the normal serum level for creatinine?
    0.5-1.5 mg/dL
  13. What are the replacement solutions we use to increase fluid levels?
    • crystalloids:
    • electrolyte solutions (NS, D5W, LR)
    • contain electrolytes and/or glucose
    • used for volume expansion
    • do NOT contain plasma proteins
    • colloids:
    • plasma protein or other colloidal molecules (albumin, hetastarch)
  14. Which crystalloids are isotonic?
    • LR
    • 0.9% NS
    • D5NS
  15. Which crystalloids are hypotonic?
    0.45% NS, D5W
  16. Which crystalloids are hypertonic?
    D51/2NS, D10W
  17. What should be used for standard fluid maintenance?
    D51/2NS + 20mEq KCl @ 100cc/h
  18. What should never be given to adjust or maintain fluids?
    sterile water IV
  19. What are the sodium rules?
    • total body salt rules volume - too much volume means too much Na+, too little volume means too little Na+
    • water rules tonicity (serum sodium)
  20. What effect to diruetics have on urine?
    • lock you into urine that = 1/2NS
    • as pt loses Na, they lose free water - need to replace free water to avoid hyponatremia
    • (sweat also equals 1/2NS - all the time)
  21. If you give diretics and replace the loss with free water, what do you get?
    hyponatremia
  22. If you give diuretics and you replace the loss with NS, what do you get?
    hypernatremia
  23. What are the clinical features of hyponatremia?
    • HA
    • muscle cramps
    • N
    • lethargy
    • cerebral edema
    • agitation
    • seizures
    • coma
    • death (mortality is 5-50%)
  24. What is cerebral edema?
    not enough Na holding water outside the brain, so too much water gets inside
  25. What is hypotonic, hypovolemic hyponatremia?
    • low total sodium
    • low water (relative excess of water)
    • if urine Na < 20, it's extrarenal loss (GI, skin, third spacing
    • if urine Na > 20, it's renal loss (diruetics, osmotic diuresis, salt-losing nephropathy) (90% of cases)
  26. What is hypotonic isovolemic hyponatremia?
    • normal total sodium
    • normal water
    • Syndrome of Inappropriate ADH (SIADH)
    • drug-induced SIADH
    • too much ADH
    • high free water levels
  27. What can cause SIADH?
    • pulmonary infections, acute resp failure, COPD
    • lung carcinoma, pancreas carcinoma
    • acute psychosis, stroke, abcess/tumor of the CNS
    • antidiuretic hormones
    • SSRIs
    • TCAs
    • CBZ
    • antineoplastics
  28. How do you treat SIADH?
    • remove offending drugs
    • restrict free water:
    • < 1-1.5L/d
    • use NS for IVF (not D5W)
    • loops
    • demeclocycline (long-term tx for SIADH)
  29. What is hypotonic hypervolemic hyponatremia?
    • high total sodium
    • very high water
    • high ADH
    • heart failure = decreased renal perfusion = decreased aldosterone
    • cirrhosis = lose water to intraabdominal space = decreased renal perfusion
    • nephrotic syndrome = lose protein = lose fluid to extravascular space = decreased renal perfusion
    • renal failure = decreased perfusion
  30. What is hypertonic hyponatremia?
    • normal sodium
    • high water
    • high glucose = high water volume
    • hyperglycemia
  31. How should hyponatremia be treated?
    • symptomatic pt:
    • aggressive tx
    • loops
    • increase Na by no more than 2 mEq/L/h
    • no more than 12 mEq/L/d (can cause central pontine myelinolysis - damage to myelin sheaths)
    • target goal 120-125 mEq/L
    • assess serum Na q 2-4h
    • asymptomatic pt:
    • correct underlying cause
    • loops
    • monitor
  32. What is hypovolemic hypernatremia?
    • low total sodium
    • very low water
    • replace with NS utnil BP fixed, then 1/2NS to replace free water
  33. What is isovolemic hypernatremia?
    • normal sodium
    • low water
    • low ADH
    • low urine osmolality (peeing more water)
    • diabetes insipidous
    • avoid rapid correction b/c brain produces its own osmols to keep water there....add water too fast and it goes straight to the brain!!
    • decrease sodium by 0.5-1 mEq/L/h
  34. What causes diabetes insipidous?
    • Central DI (ADH not being secreted):
    • idiopathic
    • trauma
    • neoplasms
    • Nephrogenic DI (kidneys not responding to ADH):
    • electrolyte disorders
    • drugs (lithium, demeclocycline, thiazides)
  35. What is the normal serum level of K?
    3.5-5.0 mEq/L
  36. What causes hypokalemia?
    • Intracellular shifts:
    • insulin
    • metabolic alkalosis
    • albuterol
    • Increased exretion:
    • diuretics
    • aldosterone (sodium retention)
    • amphotericin B
    • GI losses
    • hypomagnesemia (can't correct K without treating low Mg!!!)
    • Decreased intake:
    • rare
  37. What are the sx of hypokalemia?
    • fatigue
    • leg cramps
    • N/V
    • ileus
    • arrhythmias
  38. How do you treat hypokalemia?
    • foods rich in K
    • salt substitute
    • K supplementation (required if < 3.0 mEq/L)
    • check Mg level
  39. How should K supplementation be given?
    • chloride salt - otherwise won't hang on to K very well
    • 40-100 mEq/d
    • IV - dose 10-20 mEq over at least 1h:
    • peripheral 10 mEq/h
    • central 20 mEq/h (only with monitor)
    • NEVER give IV push - burn out the vessel
    • check K levels after every 30-40 mEq
  40. What causes hyperkalemia?
    • elevated body stores:
    • increased intake
    • decreased excretion (renal failure, ACEI, ARBs, NSAIDs, K sparing diuretics)
    • extracellular shifts:
    • metabolic acidosis
    • insulin deficiency
    • BBL
  41. What are the sx of hyperkalemia?
    • peaked T wave
    • muscle weakness
    • paresthesias
    • neuromuscular abnormalities
  42. How do you treat hyperkalemia?
    • CaCl or Ca gluconate - first line
    • insulin + glucose (if needed)
    • kayexelate (could cause fluid retention d/t increased Na)
    • lasix (if fluid volume will tolerate it)
    • Steps:
    • stabilize the heart
    • drive intracellularly
    • remove from body
    • decrease intake
  43. What is the normal serum level of phosphorus (phosphate)?
    2.7-4.5 mg/dL
  44. What is considered to be mild to moderate hypophosphatemia?
    1-2 mg/dL
  45. What is considered to be severe hypophosphatemia?
    <1 mg/dL
  46. What are the causes of hypophosphatemia?
    • vitamin D deficiency
    • phosphate binders
    • diruetics
    • hyperparathyroidism
    • parenteral nutrition
    • insulin
  47. What are the sx of hypophosphatemia?
    • irritability
    • weakness
    • seizures
    • myalgia
    • hemolysis
    • respiratory distress
    • osteomalacia
    • arrhythmias
  48. How do you treat mild-moderate hypophosphatemia?
    • PO:
    • 50-60 mmol/d divided into 3-4 doses (notice dose is in mmol, not mEq)
    • K-Phos Neutral 1-2 tabs QID w/water
    • IV:
    • 0.08 - 0.15 mmol/kg
    • repeat until serum phosphorus > 2mg/dL to avoid going hyperphosphatemic
  49. How do you treat severe hypophosphatemia?
    • 0.25 - 0.5 mmol/kg IV
    • repeat until serum phosphorus > 2 mg/dL to avoid going hyperphosphatemic
  50. What are the causes of hyperphosphatemia?
    • renal failure
    • hypoparathyroidism
    • parenteral nutrition
    • phosphate enemas
    • acidosis
  51. What are the sx of hyperphosphatemia?
    • N/V
    • muscle pain/weakness
    • hyperreflexia
    • tetany
    • soft tissue calcification (keep Ca-Phosphate product < 55)
  52. How do you treat hyperphosphatemia?
    • aluminum or magnesium antacids
    • calcium (first line if Ca is not too high)
    • sevelamer (give with meals)
  53. What is the normal serum level of magnesium?
    • 1.7-2.1 mEq/L
    • 1.5-2 mg/dL
  54. What is the best choice for treating mild hypomagnesemia (1-1.5 mEq/dL) without sx?
    Mag Ox tabs (least chance of diarrhea)
  55. What is the treatment for moderate hypomagnesemia (<1 mEq/dL with no life-threatening sx)?
    • Day 1: 1 mEq/kg/d IV cont infusion of MgSO4
    • Days 2-5: 0.5 mEq/kg/d IV of MgSO4
  56. What is the treatment for severe hypomagnesemia (<1 mEq/L with life-threatening sx)
    • 2g MgSO4 IV, then
    • 0.5 mEq/kg IV over 6h, then
    • 0.5 mEq/kg IV over 18h
  57. What are the symptoms of hypomagnesemia?
    • TYPICALLY ASYMPTOMATIC
    • hyperreflexia
    • seizures
    • confusion
    • ventricular arrhythmias
    • torsades de pointes
  58. Which electrolyte is considered to be a "sedative for the CV system"?
    • Mg:
    • increases arterial dilation
    • decreases BP
    • relaxes muscles
  59. What are the SE of IV magnesium?
    • flushing
    • sweating
  60. What are the SE of oral magnesium?
    diarrhea
  61. What are the sx of hypermagnesemia?
    • hypotension
    • decreased deep tendon reflexes
    • lethargy
    • heart block
    • coma
  62. What is the treatment for hypermagnesemia?
    • avoid Mg products
    • if symptomatic:
    • CaCl IV
    • saline + loop diuretics
    • supportive care
    • Hemodialysis (HD) in pt with End Stage Renal Disease (ESRD)
  63. What is the normal serum level of Ca?
    • 8.5-10.5 mg/dL (2.1-2.7 mmol/L) total
    • 4.6-5.2 mg/dL (1.15-1.38 mmol/L) ionized (free)
  64. What is the function of potassium?
    • maintains resting potential
    • lots of other fx
  65. What is the fx of Ca?
    • bone and teeth
    • neuromuscular activity (SA node, AV node)
    • endocrine/exocrine fx
    • platelet fx
    • muscle cell contraction
  66. What is the effect of PTH on serum calcium?
    increases calcium
  67. What is the effect of calcitonin on serum calcium?
    decreases calcium
  68. How does calcitonin lower serum calcium?
    • increases deposition in bone
    • reduces absorption in the gut
    • decreases absorption in the kidneys
  69. How does PTH increase serum calcium?
    • increases absorption in the kidneys
    • increases absorption in the gut
    • increases release from bone
  70. What is the equation to calculate corrected calcium when a pt has low albumin?
    (4-alb)0.8 + Ca
  71. What are the causes of hypocalcemia?
    • hypoparathyroidism
    • vitamin D deficiency
    • hypomagnesemia
    • hyperphosphatemia (secondary hypoparthyroidism)
    • meds/chelating agents: bisphosphonates, loops, calcitonin, phenytoin
  72. How are calcium and phosphate related in the homeostasis provided by calcitonin and PTH?
    As one goes up, the other goes down
  73. What are the sx of hypocalcemia?
    • fatigue
    • irritability
    • confusion
    • seizures
    • muscle cramps
    • spasms
    • tetany
    • prolonged QT interval (chronic)
    • brittle nails (chronic)
    • hair loss (chronic)
  74. What are the treatments for acute symptomatic hypocalcemia?
    • 1g CaCl IV
    • 2-3 g Ca gluconate (not efficient in low liver fx)
  75. What are the treatments for chronic asymptomatic and corrected symptomatic hypocalcemia?
    • 1-3g/d of elemental Ca (vit D optional):
    • carbonate (Tums, OsCal, VIACTIV) 40% elemental Ca
    • Acetate (PhosLo) 25% elemental Ca used as a phos binder
  76. What are the sx of hypercalcemia?
    • N/V
    • anorexia
    • constipation
    • short QT
    • prolonged PR and QRS
    • fatigue
    • weakness
    • confusion
    • polyuria
    • nocturia
    • nephrolithiasis
  77. How do you tx hypercalcemia?
    • 200-300cc/h NS + lasix 40-80mg IV q 1-4h (first line)
    • 4 units/kg calcitonin SQ or IM q 12h
    • pamidronate 30-90mg IV over 2-24h
    • prednisone 40-60mg/d
    • monitor albumin, ECG, serum Ca q 6-12h if symptomatic (daily if mild-moderate)
Author
giddyupp
ID
42367
Card Set
Fluid and Electrolytes
Description
Fluid and Electrolytes
Updated

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