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Fluid, Electrolyte, and Acid-Base Disorders

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Fluid, Electrolyte, and Acid-Base Disorders Darren Dreyfus, D.O. Associates In Nephrology, P.C. St. Vincent s Health System Question 1 Question 1 A 71-year-old man ... – PowerPoint PPT presentation

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Title: Fluid, Electrolyte, and Acid-Base Disorders


1
Fluid, Electrolyte, and Acid-Base Disorders
  • Darren Dreyfus, D.O.
  • Associates In Nephrology, P.C.
  • St. Vincents Health System

2
Question 1
3
Question 1
  • A 71-year-old man is evaluated because of
    intermittent cough and increasing dyspnea on
    exertion. He has smoked one pack of cigarettes
    per day for 49 years. He has no other symptoms.
  • On physical examination, distant breath sounds
    are audible in both lungs and there are scattered
    rhonchi. Chest radiograph shows a perihilar mass.
    Abnormal laboratory results include hemoglobin of
    10.5 g/dL and a serum sodium of 127 meq/L.
    Endobronchial biopsy reveals small-cell lung
    cancer.

4
Question 1
  • Which of the following is most appropriate
    treatment for this patients hyponatremia?
  • Chemotherapy
  • Hypertonic saline
  • Fluid restriction
  • Fluid restriction and demeclocycline

5
Answer
6
Question 1 - Answer
  • Answer A
  • This patient with mild hyponatremia is newly
    diagnosed with small-cell lung cancer. He has no
    symptoms that are clearly attributed to the
    hyponatremia and there initiating non-specific
    therapy such as fluid restriction with or without
    demeclocycline therapy, or aggressively treating
    the hyponatremia with hypertonic saline is not
    warranted. The most important therapeutic
    intervention is to treat the underlying cancer
    with chemotherapy.

7
Question 2
8
Question 2
  • A 78-year-old woman with metastatic breast cancer
    involving the bones and soft tissues is evaluated
    in the emergency department because of lethargy
    and weakness, nausea, thirst, and dizziness. She
    has a history of congestive heart failure that
    has been controlled with medications. On physical
    examination she has orthostatic hypotension
    associated with dizziness and dry mucous
    membranes. Her lungs are clear and she has no
    dependent edema.
  • Blood urea nitrogen 42 mg/dL
  • Total serum calcium 11.4 mg /dL
  • Serum creatinine 1.6 mg/dL
  • Serum albumin 3.0 g/dL

9
Question 2
  • Administration of which of the following is the
    most appropriate treatment?
  • A biophosphonate, intravenously
  • Corticosteroids, intravenously
  • Half-normal saline
  • Normal saline
  • Furosemide

10
Answer
11
Question 2 - Answer
  • Answer D
  • The patient has hypercalcemia, the most common
    metabolic complication of malignancy. She is
    volume depleted as evidenced by her orthostatic
    hypotension, dizziness and dry mucous membranes.
    Despite her history of congestive heart failure,
    the most appropriate initial therapy is to
    replace vascular volume as vigorously as possible
    with normal saline.

12
Question 2 - Answer
  • Furosemide must not be given until the patient
    has first been adequately rehydrated.
    Administration of a bisphosphonate is not an
    appropriate initial therapeutic intervention in
    this patient because its delayed onset of effect
    and her more urgent need for volume repletion.
    Although corticosteroids can be considered as an
    adjunctive therapy in a patient with a
    potentially hormone-responsive tumor such as
    breast cancer, the top priority is volume
    repletion.

13
Question 3
14
Question 3
  • A 56-year-old man with a 25-pack-year smoking
    history, distant cerebrovascular accident, and a
    10-year history of hypertension treated with
    hydrochlorothiazide is evaluated because of
    generalized fatigue. Blood pressure is 110/70 mm
    Hg.
  • Serum sodium 128 meq/L
  • Serum potassium 3.3 meq/L
  • Serum chloride 79 meq/L
  • Serum biocarbonate 38 meq/L
  • Arterial blood gases on room air
  • pH 7.50 PCO2 50 mm Hg, PO2 74 mm Hg

15
Question 3
  • Which of the following best explains the
    patients acid-base disturbance?
  • Metabolic alkalosis
  • Respiratory acidosis
  • Respiratory alkalosis
  • Metabolic acidosis

16
Answer
17
Question 3 - Answer
  • Answer A
  • The low blood pressure and hypochloremia suggest
    volume-sensitive metabolic alkalosis due to
    diuretic therapy. Metabolic alkalosis is
    indicated by the high serum bicarbonate level and
    pH greater than 7.4 Respiratory compensation for
    the metabolic alkalosis is appropriate. The PCO2
    is 50 mm Hg, showing the expected 10-mm Hg
    increase that compensates for the 14-meq/L
    increase in serum bicarbonate level.

18
Question 3 - Answer
  • Metabolic acidosis is not a possible diagnosis
    since the bicarbonate level and pH are elevated.
    The normal arterial-to-alveolar oxygen gradient
    makes underlying chronic obstructive pulmonary
    disease unlikely, and blood gas values do not
    indicate concurrent respiratory acidosis.

19
Question 4
20
Question 4
  • A 65-year-old man with chronic alcoholism is
    evaluated because of a seizure 1 hour ago. In the
    emergency department, he is lethargic but
    conversant and oriented. He reports a several-day
    history of diarrhea and has muscle cramps. He has
    no history of trauma or previous seizures. He is
    taking no medication but has smoked 1 pack of
    cigarettes daily for the past 30 years.

21
Question 4
  • On physical examination, blood pressure is 11/075
    mm Hg, pulse rate is 100/min, and respiration
    rate is 18/min. The neck is supple. Carpopedal
    spasm and Chvosteks signs are present. The
    remainder of the physical examination is normal.

22
Question 4
  • Serum creatinine 1.4 mg/dL
  • Serum sodium 136 meq/L
  • Serum potassium 2.7 meq/L
  • Serum chloride 98 meq/L
  • Serum bicarbonate 23 meq/L
  • Serum calcium 7.6 mg/dL
  • Serum magnesium 0.5 mg /dL
  • Serum phosphorus 3.0 mg/dL

23
Question 4
  • Which of the following will best correct the
    underlying deficiency responsible for this
    patients electrolyte disorders?
  • Calcium
  • Magnesium sulfate
  • Magnesium sulfate and potassium chloride
  • Potassium chloride

24
Answer
25
Question 4 - Answer
  • Answer C
  • Hypomagnesemia is frequently seen in alcoholics
    and in persons with severe diarrhea. If the serum
    magnesium level is less than 1.0 mg/dL and
    carpopedal spasm, Chvosteks or Trousseaus sign,
    or seizures are present, intravenous treatment
    with magnesium is indicated.

26
Question 4 - Answer
  • The hypokalemia is due to diarrhea and volume
    depletion (volume depletion triggers aldosterone
    release causing sodium conservation at the
    expense of potassium loss) and to the renal
    potassium wasting induced by hypomagnesemia.
  • Attempts at correction of the hypokalemia will be
    ineffective unless hypomagnesemia and volume are
    also corrected.

27
Question 4 - Answer
  • The hypocalcemia is due to reduced secretion and
    peripheral effects of parathyroid hormone, which
    are caused by the hypomagnesemia.
  • When the hypomagnesemia is corrected, the
    parathyroid hormone levels will return to normal
    and the serum calcium level will normalize.

28
Question 5
29
Question 5
  • A 35-year-old man is evaluated because of
    recurrent nepholithiasis and is found to have a
    normal serum calcium concentration and
    hypercalciuria.

30
Question 5
  • Which of the following diets should this man
    avoid in order to reduce the risk of recurrent
    calcium stones?
  • Low-sodium diet
  • Low-calcium diet
  • Low-oxalate diet
  • Low-protein diet
  • Low-purine diet

31
Answer
32
Question 5 - Answer
  • Answer B
  • Risk factors for calcium nephrolithiasis include
    low daily fluid intake, high dietary sodium and
    oxalate, hyperoxaluria, hypercalciuria,
    hypocitrauria, and hyperuricosuria.
  • Several studies in men and women have shown that
    a high dietary calcium intake is associated with
    reduced risk for calcium stone disease.
  • In a recent study, men with hypercalciuric
    nephrolithiasis placed on a low-calcium versus a
    high-calcium diet had greater risk of subsequent
    stone formation.

33
Question 5 - Answer
  • Although not proven, it is believed that the risk
    for stone formation is lower with high dietary
    calcium because higher amounts of dietary calcium
    bind with dietary oxalate and lessen oxalate
    absorption and urinary excretion. For this same
    reason, oral magnesium therapy has also been
    used.
  • A low sodium diet can reduce renal calcium
    excretion and may reduce calcium stone formation.
    A diet high in animal protein increases urinary
    excretion of calcium and uric acid while it
    decreases excretion of citrate, and is associated
    with increased risk of calcium stone formation.
  • A diet low in animal protein may minimize this
    risk.

34
Question 5 - Answer
  • A low-purine diet reduces uric acid excretion
    and, since uric acid crystals may act as a nidus
    for formation of calcium stones, may lessen
    calcium stone formation as well.
  • A low oxalate diet may decrease absorption of
    oxalate and decrease urinary excretion of oxalate.

35
Question 6
36
Question 6
  • A 26-year-old woman with type 1 diabetes mellitus
    is evaluated in the emergency department because
    of a serum glucose concentration of 450 mg/DL and
    abdominal pain for the past 24 hours. Her
    temperature is 38 oC (101 oF).
  • Serum sodium 133 meq/L
  • Serum potassium 3.9 meq/L
  • Serum chloride 97 meq/L
  • Serum bicarbonate 10 meq/L
  • Arterial blood gases pH 7.2 PCO2, 23 mm Hg
  • Whole blood lactacte - 0.6 mmol/L

37
Question 6
  • Which of the following best explains the
    patients acid-base status?
  • Diabetic ketoacidosis
  • Diabetic ketoacidosis and proximal renal tubular
    acidosis
  • Diabetic ketoacidosis and respiratory acidosis
  • Diabetic ketoacidosis and metabolic alkalosis

38
Answer
39
Question 6 - Answer
  • Answer A
  • The patient has an anion gap metabolic acidosis
    with appropriate respiratory compensation
    consistent with a diabetic ketoacidosis.
    Metabolic acidosis is indicated by a low serum
    bicarbonate level and an arterial blood pH less
    than 7.4. The respiratory compensation is
    appropriate thus, there is not a concomitant
    respiratory disorder accompanying this metabolic
    acidosis.
  • The patient has an anion gap of 26. The change in
    the anion gap is 14. The change in the
    bicarbonate level is 14, calculated as the normal
    bicarbonate concentration minus the measured
    bicarbonate concentration.

40
Question 6 - Answer
  • Thus, the ration between the change in the anion
    gap and the change in the serum bicarbonate is 1,
    suggesting that a concurrent non-anion gap
    metabolic acidosis or a concurrent metabolic
    alkalosis is not present.
  • Proximal renal tubular acidosis causes a
    non-anion gap metabolic acidosis, and if it were
    present with ketoacidosis, we would expect both a
    non-anion gap and an anion gap metabolic
    acidosis. That is, the ration between the change
    in the anion gap to the change in the serum
    bicarbonate level would be less than 1.

41
Question 7
42
Question 7
  • A 23-year-old woman with type 1 diabetes mellitus
    is evaluated in the emergency department because
    of a 2-day history of dysuria and urinary
    frequency. Three years ago she had cystitis
    twice in 6 months in both occasions, she was
    treated with antibiotics. She uses insulin to
    control her diabetes and takes 1 or 2 ibuprofen
    tablets daily for headaches.

43
Question 7
  • On physical examination, the blood pressure is
    115/80 mm Hg, pulse rate is 80/min, and temp is
    37.4 oC (99.3 oF). Optic fundoscopy reveals
    microaneurysms and the neurological examination
    demonstrates diminished sensitivity to pinprick
    and light touch in the lower extremities. The
    remainder of the examination is unremarkable.

44
Question 7
  • Serum creatinine 1.8 mg/dL (1.6 a month ago)
  • Serum sodium 138 meq/L
  • Serum chloride 106 meq/L
  • Serum potassium 6.2 meq/L
  • Serum bicarbonate 21 meq/L
  • Urinalysis Specific gravity 1.020 3
    proteinuria 25 leukocytes/hpf

45
Question 7
  • On renal ultrasonography, the right kidney is
    11.0 cm and the left kidney is 10.9 cm. No
    hydronephrosis or stones are present.
  • Which of the following is the most likely cause
    of her hyperkalemia?
  • Acute renal failure
  • Diabetic ketoacidosis
  • High sodium diet
  • Hyporeninemic hypoaldosteronism

46
Answer
47
Question 7 - Answer
  • Answer D
  • The most likely cause of hyperkalemia is
    hyporeninemic hypoaldosteronism, a condition that
    occurs in 20 to 30 of diabetic persons.
  • Hyperkalemia occurs most often in diabetic
    patients who have mild to moderate renal failure
    (as in this case) superimposed on the hyporenin
    hypoaldosterone state.
  • The later condition seems to be due to
    unresponsiveness of the adrenal zona glomerulosa
    to stimulation by angiotensin II, renin, and
    hyperkalemia itself.
  • Many diabetic patients with hyperkalemia have low
    renin levels, caused by impaired conversion of
    prorenin to renin.

48
Question 7 - Answer
  • Since prostaglandins stimulate renin, use of
    ibuprofen may contribute to the hypoaldosterone
    state, but by itself rarely causes hyperkalemia.
  • Diabetic ketoacidosis is not present.
  • A change in serum creatinine concentration from
    1.6 to 1.8 would not cause hyperkalemia in a
    patient who had normal renin-aldosterone
    function.
  • A high-sodium diet does not cause hyperkalemia.

49
Question 8
50
Question 8
  • A 63-year-old man is evaluated because of upper
    and lower extremity cramps and diffuse muscle
    weakness of 2 weeks duration. He has been taking
    aspirin for 6 weeks because of low back pain. The
    physical examination is normal.
  • Serum sodium 135 meq/L
  • Serum potassium 2.6 meq/L
  • Serum chloride 117 meq/L
  • Serum bicarbonate 15 meq/L
  • Arterial blood gases pH, 7.30 PCO2, 31 mm Hg
  • Urine pH 5.0

51
Question 8
  • Which of the following best explains his
    acid-base status?
  • Ethylene glycol toxicity
  • Lactic acidosis
  • Proximal renal tubular acidosis
  • Salicylate toxicity

52
Answer
53
Question 8 - Answer
  • Answer C
  • The electrolyte and arterial blood gas patterns
    are consistent with a non-anion gap metabolic
    acidosis.
  • Metabolic acidosis is indicated by a low serum
    bicarbonate level and an arterial blood pH less
    than 7.4.
  • The anion gap, calculated as 135 (117 15)3,
    indicates a non-anion gap acidosis.
  • A low anion gap (defined as less than 7) can be
    caused by an increase in unmeasured cation such
    as calcium, magnesium, lithium, or a positively
    charged paraprotein produced by a myeloma.
  • A low anion gap can also be cause by a decrease
    in unmeasured anions such as albumin.

54
Question 8 - Answer
  • The urine pH of 5.0 is consistent with a proximal
    renal tubular acidosis in which distal tubular
    function is normal. In these patients, when the
    serum bicarbonate falls below the threshold for
    complete proximal reabsorption, the distal tubule
    is able to lower the pH normally. The low urine
    pH rules out distal renal tubular acidosis.
    Proximal renal tubular acidosis often causes
    hypokalemia and a non-anion gap metabolic
    acidosis.

55
Question 8 - Answer
  • One cause of renal tubular acidosis is the
    presence of a monoclonal light chain.
  • Proximal renal tubular acidosis due to a
    monoclonal light chain may occur before multiple
    myeloma is diagnoses.
  • Evaluation for multiple myeloma is warranted.
  • Salicylate toxicity, lactic acidosis, and
    ethylene glycol toxicity all cause an anion gap
    metabolic acidosis.

56
Question 9
57
Question 9
  • A 67-year-old woman is evaluated because of a
    6-month history of gradual-onset dementia. She
    has smoked 1 to 2 packs per day of cigarettes for
    40 years and she drinks 1 ounce of alcohol
    weekly.
  • On examination, she is disoriented to time and
    place. Her blood pressure is 142/88 mm Hg,
    without orthostatic change, pulse rate is 68/min,
    respiration rate is 12/mi, and temperature 37 oC
    (98.6 oF). There is no neck vein distention, the
    lungs are clear, the cardiac and neurological
    examinations are normal, and there is no
    peripheral edema.

58
Question 9
  • Plasma glucose 84 mg/dL
  • Blood urea nitrogen 6 mg/dL
  • Serum creatine 0.5 mg/dL
  • Serum sodium 124 meq/L
  • Serum potassium 4.2 meq/L
  • Serum chloride 89 meq/L
  • Serum bicarbonate 24 meq/L

59
Question 9
  • Serumn cholesterol 182 mg/dL
  • Serum triglyceride 60 mg/dL
  • Serum total protein 7.5 g/dL
  • Serum osmolality 255 mosmol/kg
  • Urine osmolality 400 mosmo/kg

60
Question 9
  • Which of the following is the most likely cause
    of her hyponatremia?
  • Cirrhosis
  • Pseudohyponatremia
  • Psychogenic polydipsia
  • Syndrome of inappropriate antidiuretic hormone
    secretion

61
Answer
62
Question 9 - Answer
  • Answer D
  • This patient has the syndrome of inappropriate
    antidiuretic hormone secretion. The physical
    examination normal serum potassium level and
    low concentrations of blood urea nitrogen, serum
    creatinine, and serum uric acid are consistent
    with euvolemic hyponatremia and not with
    cirrhosis which is associated with a decreased
    circulating vascular volume.
  • The normal levels of cholesterol, triglycerides,
    and total proteins rule out pseudohyponatremia.

63
Question 9 - Answer
  • In a patient with psychogenic polydipsia,
    ingestion of large amounts of water would result
    in hyponatremia. However, the appropriate
    compensatory response would be suppression of
    antidiuretic hormone, which results in a dilute
    urine (excretion of free water) this phenomenon
    is not present in this patient, as evidences by
    the inappropriately high urine osmolality.

64
Question 10
65
Question 10
  • A 39-year-old man is evaluated in the emergency
    department because of a severe left flank pain
    and hematuria after playing softball. The pain is
    sharp and radiates to the groin. He vomited eight
    times before presentation. He has nonobstructing,
    calcium-containing kidney stone in the
    uretopelvic junction on the left side.

66
Question 10
  • On initial evaluation, his blood pressure was
    130/90 mm Hg and pulse rate was 110/min.
  • Serum sodum 141 meq/L
  • Serum potassium- 4.0 meq/L
  • Serum chloride 100 meq/L
  • Serum bicarbonate 34 meq/L
  • Arterial blood gases pH, 7.61 PCO2, 36 mg Hg

67
Question 10
  • Which of the following best describes this
    patients acid-base disorder?
  • Metabolic acidosis and respiratory alkalosis
  • Metabolic alkalosis
  • Metabolic alkalosis and respiratory acidosis
  • Metabolic and respiratory alkalosis
  • Respiratory alkalosis

68
Answer
69
Question 10 - Answer
  • Answer D
  • Arterial blood gas values demonstrate a mixed
    metabolic and respiratory alkalosis. Metabolic
    alkalosis is indicated by the high serum
    bicarbonate level and a pH greater than 7.4
  • Respiratory compensation for the metabolic
    alkalosis is not appropriate the PCO2 would be
    expected to increase in compensation for the
    elevated serum bicarbonate level, but instead,
    the PCO2 has decreased to 36 mm Hg, indicated the
    presence of a respiratory alkalosis.

70
Question 10 - Answer
  • The anion gap is 7, calculated as (141 100
    34) thus, there is no hidden anion-gap
    metabolic acidosis. The respiratory alkalosis is
    most likely due to pain induced hyperventilation
    from the kidney stone, and metabolic alkalosis is
    probably a result of vomiting.

71
Question 11
72
Question 11
  • The preceding patient is given intravenous
    infusion of 0.9 normal saline at 200 mL/h. Two
    days later, his flank pain worsens dramatically,
    but nausea and vomiting have resolved. Blood
    pressure and pulse rate are unchanged.

73
Question 11
  • BUN 8 mg/dL
  • Serum creatinine 0.9 mg/dL
  • Serum sodum 138 meq/L
  • Serum sodium 138 meq/L
  • Serum potassium 4.0 meq/L
  • Serum chloride 105 meq/L
  • Serum bicarbonate 22 meq/L
  • Arterial blood gases ph, 7.48 PCO2, 30 mm Hg

74
Question 11
  • Which of the following best describes his
    acid-base status?
  • Metabolic acidosis with respiratory alkalosis
  • Metabolic alkalosis and respiratory alkalosis
  • Respiratory acidosis and metabolic alkalosis
  • Respiratory alkalosis

75
Answer
76
Question 11 - Answer
  • Answer D
  • The patient has persistent respiratory alkalosis,
    as indicate by the low PCO2, and a pH greater
    than 7.4. The condition is most likely due to
    hyperventilation in response to pain from the
    kidney stone.
  • For each 10 mm Hg drop in the PCO2, the serum
    bicarbonate will decrease by 2. to 4.5 meq/L.
    Since the serum bicarbonate level decreased by 2
    meq/L, this confirms the diagnosis of a simple,
    compensated respiratory alkalosis.

77
Question 12
78
Question 12
  • A 46-year-old man is evaluated because of a
    20-year history of difficult to control
    hypertension and hypokalemia treated with
    amlodipine. He also has irritable bowel syndrome
    and produces two semi-formed stools daily. On
    examination, the blood pressure is 150/88 mg Hg,
    and pulse rate is 74/min. The lungs are clear,
    and the heart rhythm is regular, with no gallop
    or murmur. Abdominal examination is normal.
    Pulses in the lower extremities are normal, and
    no edema is present.

79
Question 12
  • Serum sodium 142 meq/L
  • Serum potassium 2.7 meq/L
  • Serum chloride 105 meq/L
  • Serum bicarbonate 30 meq/L
  • Urinalysis pH 5.0 specific gravity 1.020
    dipstick negative for protein and blood
  • 24-hour urine results
  • Sodum 100 meq
  • Potassium 82 meq
  • Calcium 200 mg

80
Question 12
  • Which of the following is the most likely cause
    of his hypokalemia?
  • Diarrhea
  • Distal renal tubular acidosis
  • Gitelmans syndrome
  • Primary hyperaldosteronism

81
Answer
82
Question 12 - Answer
  • Answer D
  • Primary hyperaldosteronism is associated with
    hypertension, hypkalemia, and renal potassium
    wasting. It is usually associated with a 24-hour
    urinary potassium excretion greater then 30 meq
    in the setting of a serum potassium concentration
    less than 3.0 meq/L.
  • All of these features are present in this
    patient. Distal renal tubular acidosis is
    incorrect because the patient is not acidotic and
    has an acid urine pH.

83
Question 12 - Answer
  • Gitelmans syndrome is associated with
    hypokalemia, renal potassium wasting, and
    hypocalciuria (which is not present in this
    patient). And normotension.
  • Diarrhea would cause metabolic acidosis and may
    cause hypokalemia but would not be associated
    with renal potassium unless the patient is
    hypovolemic resulting in stimulation of the
    renin-angiotensin-aldosterone system.

84
Question 13
85
Question 13
  • A 60-year-old woman with a history of essential
    hypertension is admitted to the hospital after 7
    years of vomiting. On physical examination, she
    appears ill. The systolic blood pressure is 110
    mg Hg seated and 70 mg Hg standing. The pulse
    rate while seated is 120/min. The abdominal
    examination reveals rebound tenderness and no
    bowel sounds.

86
Question 13
  • Serum sodium 140 meq/L
  • Serum potassium 3.2 meq/L
  • Serum chloride 80 meq/L
  • Serum bicarbonate 11 meq/L
  • Arterial blood gases pH, 7.29 PCO2, 24 mm Hg

87
Question 13
  • Which of the following best describes her
    acid-base status?
  • Anion gap metabolic acidosis
  • Anion gap metabolic acidosis and metabolic
    alkalosis
  • Non-anion gap metabolic acidosis and metabolic
    alkalosis
  • Non-anion gap metabolic acidosis

88
Answer
89
Question 13 - Answer
  • Answer B
  • The patient has an anion gap metabolic acidosis
    and a con-current metabolic alkalosis. Metabolic
    acidosis is indicated by the low serum
    bicarbonate level and a pH less than 7.4. The
    distinctly abnormal anion gap of 49, calculated
    as 140 (80 11), suggests the presence of an
    anion gap metabolic acidosis, perhaps due to
    ischemic bowel and resultant lactic acidosis.

90
Question 13 - Answer
  • The change in the anion gap is 37, calculated as
    the anion gap (49) minus the expected normal
    anion gap (12). The change in serum bicarbonate
    level is 13, calculated as the normal serum
    bicarbonate level (24 meq/L) minus the actual
    serum bicarbonate level (11 meq/L).
  • The ratio between the change in the anion gap and
    the change in the serum bicarbonate level, or the
    delta-delta, is greater than 2, thus suggesting a
    concurrent metabolic alkalosis.

91
Question 13 - Answer
  • Vomiting causes hydrogen ion loss and is the most
    likely cause of the metabolic alkalosis.
  • Respiratory compensation for the metabolic
    acidosis is appropriate.

92
Question 14
93
Question 14
  • An 18-year-old male high school student is
    evaluated in the emergency department because of
    confusion, nausea, headache, and decreased vision
    after a camping trip. The patients friends state
    that he became ill 14 hours ago.

94
Question 14
  • BUN 14 mg/dL
  • Serum creatinine 1.0 mg/dL
  • Serum sodium 140 meq/L
  • Serum chloride 100 meq/L
  • Serum potassium 4 meq/L
  • Serum bicarbonate 12 meq/L
  • Serum glucose 108 mg/dL
  • Measured serum osmolality 326
  • Serum ketones Negative
  • Serum lactate 0.7 meq/L
  • Arterial blood gases pH, 7.29 PCO2, 26 mm Hg

95
Question 14
  • Ingestion of which of the following best explains
    the acid-base abnormalities?
  • Ethanol
  • Isopropyl alcohol
  • Methanol
  • Salicylate

96
Answer
97
Question 14 - Answer
  • Answer C
  • The patient has an anion gap metabolic acidosis.
    The differential diagnosis of an anion gap
    metabolic acidosis can be narrowed by calculating
    the osmolar gap.
  • Methanol causes both an anion gap metabolic
    acidosis an an elevated osmolar gap.

98
Question 14 - Answer
  • Ethanol ingestion increases the osmolar gap but
    does not cause this degree of metabolic acidosis
    unless it is accompanied by concomitant lactic
    acidosis or alcoholic ketoacidosis.
  • Ingestion of isopropyl alcohol also increases the
    osmolar gap but does not produce anion gap
    metabolic acidosis.
  • Use of salicylate causes anion gap metabolic
    acidosis but does not increase the osmolar gap.
  • Finally, the clinical clue of decreased vision
    strongly supports methanol and not ethanol as the
    poison methanol is toxic to the optic nerve.

99
Question 15
100
Question 15
  • A 28-year-old woman is evaluated because of
    recurrent calcium-containing kidney stones. She
    currently has no symptoms of renal colic. For
    several years, she has had dry eyes, dry mouth,
    and Raynauds phenomenon. Crohns disease was
    diagnosed 10 years ago she is currently
    asymptomatic and passes one formed stool daily.

101
Question 15
  • She takes no medications. On examination, the
    blood pressure is 115/74 mm Hg, pulse rate is
    72/min, and temperature is 37 oC (98.6 oF). The
    physical examination is unremarkable. Plain
    abdominal radiography shows multiple
    calcifications within the renal parenchyma
    bilaterally.

102
Question 15
  • Serum sodium 138 meq/L
  • Serum potassium 2.8 meq/L
  • Serum chloride 109 meq/L
  • Serum bicarbonate 19 meq/L
  • Serum calcium 9.1 mg/dL
  • Serum phosphorus 3.2 mg/dL
  • Urinalysis pH 6.0 specific gravity 1.020
    trace hematuria, no proteinuria
  • Arterial blood pH 7.29

103
Question 15
  • Which of the following is the most likely
    etiology of her renal stone disease?
  • Distal renal tubular acidosis
  • Enteric hyperoxaluria
  • Idiopathic hypercalciuria
  • Primary hyperparathyroidism

104
Answer
105
Question 15 - Answer
  • Answer A
  • This patient has renal tubular acidosis, as
    evidenced by hypokalemia and inappropriately
    alkaline urine in the presence of a metabolic
    acidosis.
  • Type I or distal renal tubular acidosis is
    associated with increased urinary calcium
    excretion and an increased incidence of
    nephrolithiasis and nephrocalcinosis.
  • Distal renal tubular acidosis can result from the
    tubulointerstitial renal disease that occurs with
    Sjogrens syndrome, which is suggested in this
    case by the patients Raynauds phenomenon and
    symptoms of dry eyes and mouth.

106
Question 15 - Answer
  • The normal calcium and phosphate values make
    hyperparathyroidism unlikely.
  • Enteric hyperoxaluria may be seen in inflammatory
    bowel diseases, but usually only in the setting
    of significant gastrointestinal malabsorption and
    diarrhea.
  • Idiopathic hypercalciuria does not cause
    metabolic acidosis or hypokalemia.

107
Question 16
108
Question 16
  • A 39-year-old man is admitted for elective right
    inguinal hernia repair. He has bipolar disorder,
    for which he takes lithium carbonate. In
    preparation for surgery, he has received nothing
    by mouth for the previous 12 hours.
  • On examination, the patient is alert and in no
    distress, but is thirsty. Blood pressure is
    110/70 mm Hg seated and standing, pulse rate
    90/min, respiratory rate 12/min, temperature 36.9
    oC (98.4 oF). No neck vein distension is present.
    Except for a right inguinal hernia, the remainder
    of the examination is normal.

109
Question 16
  • BUN 18 mg/dL
  • Serum creatinine 1.1 mg/dL
  • Serum sodium 150 meq/L
  • Serum potassium 4.5 meq/L
  • Serum chloride 112 meq/L
  • Serum bicarbonate 26 meq/L
  • Urinalysis Specific gravity 1.006

110
Question 16
  • Which of the following is the most likely cause
    of the elevated serum sodium level?
  • Fluid restriction
  • High dietary sodium intake
  • Renal concentrating defect
  • Syndrome of inappropriate antidiuretic hormone
    secretion

111
Answer
112
Question 16 - Answer
  • The patient probably has hypernatremia due to a
    renal concentrating defect caused by lithium
    therapy. The urine specific gravity is low
    despite an increased serum sodium level,
    indicating a renal concentrating defect.
  • In healthy persons, 12 or more hours of fluid
    restriction would result in renal water
    conservation and high specific gravity of the
    urine and would not result in hypernatremia.
  • High dietary sodium intake does not cause
    hypernatemia, and the syndrome of inappropriate
    antidiuretic hormone secretion results in
    hyponatremia.

113
Question 17
114
Question 17
  • A 19-year-old man with epilepsy previously well
    controlled with phenytoin therapy is brought to
    the hospital by emergency medical personnel
    because of a generalized seizure. The patient had
    stopped taking phenytoin about 3 weeks earlier. A
    second seizure occurred shortly after arrival at
    the emergency department and was successfully
    treated with lorazepam.

115
Question 17
  • On examination, he is confused but his physical
    examination is otherwise normal.
  • Serum sodium 140 meq/L
  • Serum potassium 4.0 meq/L
  • Serum chloride 104 meq/L
  • Serum bicarbonate 10 meq/L
  • Serum creatine kinase 45 U/L
  • Arterial blood gasses pH, 7.05 PCO2, 38 mm Hg

116
Question 17
  • For the acid-base disorder, which of the
    following is the most appropriate course of
    action?
  • Acetazolamide
  • Intravenous bicarbonate
  • Mechanical ventilation
  • 0.45 normal saline
  • Observe

117
Answer
118
Question 17 - Answer
  • Answer E
  • The patient has an anion gap metabolic acidosis
    with concurrent respiratory acidosis. Lactic
    acidosis associated with the seizure is the most
    likely explanation for the metabolic acidosis.
    Since this state quickly reverses with cessation
    of the seizure, observation alone is warranted.
  • Mechanical ventilation to correct the concurrent
    respiratory acidosis is not needed if the patient
    is awake and breathing normally.
  • Acetazolamide may cause a proximal renal tubular
    acidosis with bicarbonate wasting and thus worsen
    the acidosis.

119
Question 17 - Answer
  • Intravenous fluids are not contraindicated, but
    neither are they are necessary to correct the
    acid-base disturbance.
  • Although the patient has an arterial blood pH
    less than 7.2, the transient nature of the
    acidosis along with the ability to regenerate
    bicarbonate from lactate makes bicarbonate
    therapy unnecessary.

120
Question 18
121
Question 18
  • A 64-year-old man with previously diagnosed
    alcoholic cirrhosis is admitted to the hospital
    with a 5-day history of lethargy and confusion.
    Blood pressure is 110/70 mm Hg, pulse rate is
    87/min, and temperature is 36 oC (96.8 oF). The
    neck veins are not distended. The lungs are
    clear, with decreased breath sounds at both
    bases. There is no S3. Ascites and 1 ankle edema
    are present.

122
Question 18
  • BUN 15 mg/dL
  • Serum creatinine 1.0 mg/dL
  • Serum sodium 114 meq/L
  • Serum potassium 4.1 meq/L
  • Serum chloride 80 meq/L
  • Serum bicarbonate 28 meq/L
  • Serum total protein 6.9 g/dL
  • Cholesterol 186 mg/dL
  • Serum osmolality 241 mosmol/kg
  • Urine osmolaity 400 mosmol/kg
  • Spot urine sodium 10 meq/L

123
Question 18
  • What is the cause of this patients hyponatremia?
  • Nonosmotic stimulation of antidiuretic hormone
  • Hepatorenal syndrome
  • Low-sodium diet
  • Reset osmostat
  • Pseudohyponatremia

124
Answer
125
Question 18 - Answer
  • Answer A
  • This patient with hyponatremia and excess
    extracellular fluid volume has nonosmotic
    stimulation of antidiuretic hormone due to
    decreased arterial blood volume (decreased
    effective circulating volume) from splanchnic
    vasodilation.
  • Hyponatremia may be seen in the hepatorenal
    syndrome, but his renal function is normal and it
    is not the cause of the hyponatremia.

126
Question 18 - Answer
  • A low-sodium diet is almost never associated with
    hyponatremia this patients urine is
    inappropriately concentrated for the level of
    serum hypotonicity. Pseudo-hyponatremia occurs in
    patients with a normal osmolality and very high
    serum levels of either proteins or lipids.

127
Question 19
128
Question 19
  • A 48-year-old woman is found to have a serum
    calcium concentration of 10.9 mg/dL on routine
    screening.
  • Previously, a bone densitometry showed T scores
    at the lumbar spine and left proximal femur of
    2.14 and 2.64, respectively. There is no
    history or evidence of renal stones, bone
    fracture, cognitive impairment, or fatigue. The
    intact serum parathyroid hormone level is 115
    pg/mL (normal range, 10 to 65 pg/mL).

129
Question 19
  • What is the most appropriate next step in the
    treatment of this patient?
  • Biphosphonate therapy
  • Estrogen replacement therapy
  • Low-calcium diet
  • Parathyroid surgery

130
Answer
131
Question 19 - Answer
  • Answer D
  • This patient has mild hypercalcemia and
    osteoporosis of the hip. The most common cause of
    this presentation is primary hyperparathyroidism,
    which is confirmed in this patient on the basis
    of an elevated serum parathyroid hormone
    concentration.
  • According to the National Institutes of Healths
    recommendations for treatment of otherwise
    asymptomatic patients with primary
    hyperparathyroidism, this patients bone loss is
    itself an indication for surgery.

132
Question 19 - Answer
  • She should be referred to an experienced
    parathyroid surgeon for resection of what is
    likely to be a single parathyroid adenoma.
  • The calcium metabolism should normalize
    postoperatively, and bone density is like to
    improve.
  • Estrogen replacement therapy or a biphosphonate
    will reduce bone turnover and may stabilize bone
    density, but patient with a recognized secondary
    cause of bone loss, correction of the underlying
    abnormality is more logical.

133
Question 19 - Answer
  • However, if surgery were considered too risky, or
    if declined by the patient, medical
    antiresorptive therapy may have a short-term
    salutary effect on the skeleton in older women
    with hyperparathyroidism.
  • Recent studies, however, have also demonstrated a
    significant increase in the risk of breast cancer
    and cardiovascular disease in women treated with
    post-menopausal estrogen/progestin regimens.

134
Question 19 - Answer
  • A low-calcium diet will probably do little to
    correct hypercalcemia, may increase the
    parathyroid hormone concentration further, and
    may increase the risk of further bone loss.

135
Question 20
136
Question 20
  • A 44-year-old man comes to the emergency
    department with polyuria and polydipsia. He has a
    2-year history of a brain tumor involving the
    pons and middle cerebral peduncles. A bone scan
    has shown multiple areas of abnormal uptake and
    has been receiving high-dose dexamethasone. Over
    the past 2 weeks, he has noted increased
    urination with nearly constant thirst.

137
Question 20
  • Physical examination reveals orthostatic
    hypotension, cerebellar ataxia, and diffuse
    muscle weakness. Admission laboratory results
    included a serum sodium of 155 meq/L, plasma
    glucose of 150 mg/dL, and urine osmolality of 117
    mosm/kg. He has significant increase in urine
    osmolality (greater) than 50) within 1 to 2
    hours after injection of arginine vasopression.

138
Question 20
  • What is the most likely cause of the
    hypernatremia?
  • Central diabetes insipidus
  • Diabetes mellitus
  • Diabetes insipidus, type undetermined
  • Nephrogenic diabetes insipidus
  • Primary polydipsia

139
Answer
140
Question 20 - Answer
  • Answer A
  • This patient is clearly hyperosmolar, as
    estimated by multiplying the serum sodium level
    by 2. The appropriate renal response to
    hyperosmolality is to maximally concentrate the
    urine. This response is not seen in this patient.
    Thus, he has either diabetes insipidus or a
    solute diuresis. A solute diuresis is most often
    caused by hyperglycemia. This patient does have a
    plasma glucose level of 180 mg/dL however this
    degree of elevation is unlikely to cause
    significant solute diuresis because the renal
    threshold for glucose reabsorption is most
    persons is 200 to 225 mg/dL.

141
Question 20 - Answer
  • Furthermore, solute diuresis is usually
    characterized by isotonicity of the urine,
    whereas this patient has a markedly hypotonic
    urine. Consequently, diabetes mellitus is
    unlikely.
  • Hyperosmolar patients without glucosuria who have
    submaximally concentrated urine have diabetes
    insipidus by definition.
  • Given his known brain tumor, central diabetes
    insipidus is clinically more like than
    nephrogenic diabetes insipidus.

142
Question 21
143
Question 21
  • A 22-year-old woman is evaluated in the emergency
    department because of severe dizziness, weakness,
    nausea, and vomiting of 1 weeks duration. She
    has noted fatigue and moderate weight loss over
    the preceding 2 months. She has a history of
    hypothyroidism and takes levothyroxine, 100 ug/d.

144
Question 21
  • On physical examination, the patient is 168 cm
    (66 in.) tall and weighs 53 kg (116 lb.) Blood
    pressure is 90/60 mm Hg supine and 80/50 mm Hg
    standing, and pulse rate is 84/min supine and
    96/min standing. The skin is well tanned, and
    there is markedly increased pigmentation of the
    gums and palmar creases.

145
Question 21
  • Hematocrit 40
  • Serum creatinine 1.2 mg/dL
  • Blood urea nitrogen 39 mg/dL
  • Serum sodium 124 meq/L
  • Serum potassium 6.8 meq/L
  • Plasma glucose 61 mg/dL

146
Question 21
  • What is the most likely underlying cause of the
    hyponatremia?
  • Acute adrenal hemorrhage
  • Autoimmune adrenalitis (Addisons disease)
  • Fulminant meningococcemia
  • Pituitary apoplexy
  • Tuberculosis

147
Answer
148
Question 21 - Answer
  • Answer B
  • This patient presents with an acute adrenal
    crisis with volume depletion, hyponatremia, and
    hyperkalemia, all of which strongly suggest
    primary adrenal insufficiency.
  • Central adrenal insufficiency due to pituitary
    apoplexy can present with an acute crisis, but
    headaches and visual field abnormalities are
    usually prominent features and hyperkalemia does
    not generally occur.
  • Primary adrenal insufficiency can result from all
    of the other causes shown as options, but
    autoimmune adrenalitis (Addisons disease) is the
    most common of these in the United States.

149
Question 21 - Answer
  • The presence of hypothyroidism in this patient
    makes autoimmune adrenalitis even more likely,
    since these two disorders occur together in
    patients with autoimmune polyglandular syndromes.
  • Fulminent meningococcemia is an unlikely cause of
    adrenal insufficiency considering the protracted
    time course of the patients illness, dark skin,
    and the absence of a sepsis syndrome.

150
Question 22
151
Question 22
  • An 82-year-old man who is in the intensive care
    unit with multiple system failure is evaluated
    for hypocalcemia. He wad admitted 2 months ago
    with multilobar pneumococcal pneumonia dn
    respiratory failure. His course has been
    complicated by difficulty in weaning from the
    ventilator, myocardial infarction, prolonged
    ileus, line sepsis, and sacral decubiti. The
    serum calcium level has gradually decreased from
    9.2 mg/dL on admission to 7.6 mg/dL today.

152
Question 22
  • What is the first piece of information that is
    needed to evaluate the hypocalcemia?
  • Serum albumin concentration
  • Urine calcium concentration
  • Serum parathyroid hormone concentration
  • Serum phosphate concentration

153
Answer
154
Question 22 - Answer
  • Answer A
  • The measured serum calcium concentration combines
    bound and free fractions. Because calcium is
    bound to plasma proteins, chiefly albumin,
    hypoalbuminemia invariably leads to a decreased
    total serum calcium level, yet free or ionized
    calcium levels will remain normal. Therefore,
    before a diagnostic search is begun for the cause
    of the hypocalcemia, it is necessary to determine
    whether the ionized calcium level is actually
    low.

155
Question 22 - Answer
  • In this patient with severe illness and multiple
    complications affecting his nutritional status,
    substantial hypoalbuminemia would be expected.
  • The serum phosphate level is elevated in patients
    with hypoparathyroidism but is likely to be
    low-normal in this patient (unless renal failure
    coexists).
  • For unclear reasons, parathyroid hormone levels
    tend to be lower than expected in critically ill
    patients.
  • Large volume blood transfusions may decrease the
    serum calcium level by complexing with citrate,
    the anticoagulant in banked blood. This matter
    may be more pertinent if the ionized calcium
    level is low.

156
End of Lecture
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