FLUID, ELECTROLYTES AND NUTRITION

Question 1

1. A 74-year-old woman (weight 72 kg) arrives in
   the emergency department with a 3-day history
   of cough, body temperature of 102°F (38.9°C),
   and lethargy. She has the following vital signs and
   laboratory values: blood pressure 72/40 mm Hg,
   heart rate 115 beats/minute, urine output 10 mL/
   hour, white blood cell count (WBC) 18 × 103 cells/
   mm3, hemoglobin 12.5 g/dL, and blood urea nitrogen
   (BUN)/serum creatinine (SCr) ratio of 28:1.7
   mg/dL (baseline SCr 1.2 mg/dL), and blood glucose
   82 mg/dL. After a 500-mL fluid bolus of 0.9%
   sodium chloride, her blood pressure is 80/46 mm
   Hg and her heart rate is 113 beats/minute. Her chest
   radiograph is consistent with pneumonia. Her medical
   history includes coronary artery disease and
   arthritis. Which is the most appropriate treatment
   at this time?
   A. Furosemide 40 mg intravenously.
   B. 5% albumin 500 mL infused over 4 hours plus
   norepinephrine titrated to maintain a systolic
   blood pressure of 90 mm Hg or higher.
   C. 1000-mL fluid bolus with 5% dextrose (D5W)
   and 0.9% sodium chloride.
   D. 1000-mL fluid bolus with 0.9% sodium chloride.

Answer 1

1. Answer: D
   This patient continues to have hypotension and tachycardia,
   both of which are signs of intravascular volume
   depletion. The improvement in blood pressure and
   tachycardia after a fluid bolus also indicates intravascular
   volume depletion. Fluid administration should
   continue until there is no further improvement in vital
   signs. Patients with intravascular volume depletion
   require a rapid bolus of crystalloid (either 0.9% sodium
   chloride or lactated Ringer solution) of 500–1000 mL
   (or about 30 mL/kg), followed by reassessment (Answer
   D). A rapid bolus is essential to prevent organ dysfunction
   caused by hypoperfusion. Although the patient has
   poor urine output, administering furosemide (Answer
   A) will worsen volume depletion. As volume is replaced,
   urine output will probably increase. Administering 5%
   albumin in combination with a vasopressor (Answer B)
   should not be the initial treatment as long as vital signs
   are improving with the administration of fluid boluses
   with 0.9% sodium chloride. In addition, colloids are
   more expensive, and there is no evidence of better outcomes
   for fluid resuscitation with colloids than with
   crystalloids. Furthermore, infusion of albumin over
   4 hours is incorrect because it would not restore intravascular
   volume rapidly enough to prevent organ dysfunction.
   Intravenous fluid containing D5W (Answer C)
   is not appropriate for fluid resuscitation, regardless of
   the blood glucose concentration.

Question 2

2. An order has been received for 2% sodium chloride.
   Assume no commercially available product is
   available. Using 0.9% sodium chloride and 23.4%
   sodium chloride, first determine how much of each
   is necessary to prepare 1 L of 2% sodium chloride.
   Second, calculate the osmolarity of 2% sodium
   chloride. Finally, determine whether the resultant
   solution should be administered through a central
   or peripheral intravenous infusion (molecular
   weight [MW] of sodium chloride is 58.5, osmotic
   coefficient is 0.93).
   A. Mix 951 mL of 0.9% sodium chloride plus
   49 mL of 23.4% sodium chloride; osmolarity =
   635 mOsm/L; peripheral intravenous infusion.
   B. Mix 951 mL of 0.9% sodium chloride plus
   49 mL of 23.4% sodium chloride; osmolarity
   = 954 mOsm/L; central intravenous infusion.
   C. Mix 850 mL of 0.9% sodium chloride plus
   150 mL of 23.4% sodium chloride; osmolarity
   = 954 mOsm/L; central intravenous infusion.
   D. Mix 850 mL of 0.9% sodium chloride plus
   150 mL of 23.4% sodium chloride; osmolarity
   = 513 mOsm/L; peripheral intravenous infusion.

Answer 2

2. Answer: A
   To answer this question, an alligation must first be set
   up using 0.9% and 23.4% sodium chloride. If 0.9%
   sodium chloride contains 154 mEq/L, 2% should contain
   about 342 mEq/L. After completing the alligation,
   the correct amounts can be double-checked by verifying
   the amount of sodium chloride in the prepared
   product: 951 mL of 0.9% sodium chloride contains
   146 mEq of sodium chloride, and 49 mL of 23.4%
   sodium chloride contains 196 mEq of sodium chloride;
   therefore, 146 mEq + 196 mEq = 342 mEq/L of sodium
   chloride in the final product. The osmolarity is calculated
   as (2 g/100 mL) × (1 mol/58.5 g) × (2 Osm/mol) ×
   (1000 mOsm/Osm) × (1000 mL/L) × 0.93 = 635 mOsm/L
   (Answer A is correct; Answer D is incorrect). Because
   of the osmotic coefficient (0.93), the sodium chloride
   does not completely dissociate in solution. Although
   use of the osmotic coefficient provides a more accurate osmolarity, it is probably not clinically relevant in calculating
   the osmolarity of intravenous sodium chloride.
   Therefore, it is safe to estimate the osmolarity of
   sodium chloride as either 635 or 684 mOsm/L, because
   there is no apparent clinical difference between these
   osmolarities. Because the osmolarity is less than 900
   mOsm/L, the infusion can be administered through a
   peripheral line, (Answers B and C are incorrect).

Question 3

3. A 68-year-old man is admitted to the hospital for
   worsening shortness of breath during the past 2
   weeks caused by heart failure. His serum sodium
   concentration on admission was 123 mEq/L. Other
   abnormal laboratory values include brain natriuretic
   peptide of 850 pg/mL and SCr of 1.7 mg/
   dL. Chest radiography is consistent with pulmonary
   edema. The patient weighs 85 kg on admission,
   which is up 3 kg from his baseline weight.
   The patient is not experiencing nausea, headache,
   or mental status changes. The physician orders 3%
   sodium chloride to treat the hyponatremia. Which
   recommendation is best?
   A. 3% sodium chloride is an appropriate choice
   because the hyponatremia is probably acute.
   B. A 250-mL bolus of 3% sodium chloride is
   appropriate if used in combination with furosemide
   to prevent volume overload.
   C. 3% sodium chloride is appropriate if the serum
   sodium does not increase more than 10 mEq/L
   in 24 hours.
   D. The risks of 3% sodium chloride outweigh the
   potential benefit for this patient.

Answer 3

3. Answer: D
   In this case, hyponatremia is likely because of congestive
   heart failure and has probably developed over
   a prolonged period (not acute onset). Patients with
   chronic hyponatremia because of heart failure are
   typically asymptomatic. Rapid correction of chronic
   hyponatremia is associated with permanent neurologic
   damage caused by central pontine myelinolysis.
   Furthermore, hypertonic saline can worsen volume
   overload in patients with heart failure. Although hyponatremia
   is a sign of worsening heart failure, correction
   of hyponatremia in patients with heart failure does not
   improve outcomes (Answer D). For these reasons, the
   risks of correcting the serum sodium with hypertonic
   saline (Answers A–C) outweigh the potential benefits.

Question 4

4. A 55-year-old man with diabetes and kidney disease
   has hyperkalemia. His laboratory values
   include potassium (K+) 7.2 mEq/L, calcium (Ca2+)
   9 mg/dL, albumin 3.5 g/dL, and blood glucose 302
   mg/dL. His electrocardiogram (ECG) is abnormal,
   with peaked T waves. What is the best recommendation
   for initial treatment?
   A. Regular insulin 10 units intravenously plus
   50 g of dextrose intravenously.
   B. 10% calcium gluconate 10 mL intravenously.
   C. Sodium polystyrene sulfonate (Kayexalate)
   15 g orally.
   D. Sodium bicarbonate 50 mEq intravenously
   over 5 minutes.

Answer 4

4. Answer: B
   Patients with hyperkalemia and ECG changes should be
   treated first with Ca2+ for cardiac stability (Answer B).
   After Ca2+ administration, other measures can be taken
   to shift K+ from the EC compartment to the IC compartment.
   Insulin (Answer A) can accomplish this; however,
   in this patient with hyperglycemia, insulin should
   be administered without glucose. Sodium polystyrene
   sulfonate (Kayexalate; Answer C) can be administered,
   but it is not effective immediately and is therefore
   not appropriate for first-line treatment of symptomatic
   hyperkalemia. Sodium bicarbonate (Answer D) is
   incorrect because it does not treat cardiac instability.

Question 5

5. A 68-year-old woman (weight 60 kg) is admitted
   to the hospital after a cardioembolic stroke. Her
   medical history is significant for atrial fibrillation, acute myocardial infarction, and diabetes. She has
   been unconscious for 48 hours. The medical team
   decides to start providing nutrition. All of her laboratory
   values, including glucose concentrations,
   are normal. Although she currently has no enteral
   access, she does have a peripheral intravenous
   catheter. Which nutritional regimen is best for this
   patient?
   A. Insert a central intravenous catheter and initiate
   parenteral nutrition (PN) containing 60 g
   of amino acids (AAs), 250 mL of 20% lipid
   emulsion, 300 g of dextrose, standard electrolytes,
   multivitamins, and trace elements
   in a volume of 2000 mL administered over
   24 hours.
   B. Insert a central intravenous catheter and initiate
   PN containing 40 g of AAs, 250 mL of
   20% lipid emulsion, 200 g of dextrose, standard
   electrolytes, multivitamins, and trace
   elements in a total volume of 2000 mL administered
   over 24 hours.
   C. Insert a nasogastric (NG) or nasoduodenal
   feeding tube and infuse an isotonic formula
   (1 kcal/mL) starting at 25 mL/hour and
   advance to a goal rate of 65 mL/hour.
   D. Insert a percutaneous endoscopic gastrostomy
   feeding tube and infuse an isotonic formula
   (1 kcal/mL) starting at 25 mL/hour and
   advance to a goal rate of 100 mL/hour.

Answer 5

5. Answer: C
   This patient is not receiving adequate nutritional intake
   because of her mental status. Because her GI tract is
   functional, it should be used for feeding to prevent gut
   mucosal atrophy. An NG or nasoduodenal feeding tube
   is appropriate for enteral access for short-term nutritional
   support (Answer C). A percutaneous gastrostomy
   tube (Answer D), which requires a surgical procedure, is used for long-term nutritional support. The patient
   should receive 25–35 kcal/kg/day. The PN formulas
   (Answers A and B) should not be used in a patient with
   a functional GI tract. Although Answer B would be an
   appropriate PN formula for peripheral administration,
   PN is associated with more complications than EN is.

Question 6

6. A 70-year-old man is admitted to the hospital with
   peritonitis caused by severe inflammatory bowel
   disease. The patient has received adequate fluid
   resuscitation, and he is prescribed appropriate
   antibiotics. After several days of the patient being
   unable to tolerate oral or enteral nutrition, the physician
   consults the pharmacist to recommend a PN
   formula to be administered through a central line.
   The patient is hemodynamically stable, with normal
   electrolyte concentrations. Weight is 55 kg,
   BUN/SCr is 20/1.1 mg/dL, and WBC is 17 × 103
   cells/mm3. Assuming that appropriate electrolytes,
   multivitamins, and trace elements are included,
   which PN formula, when administered over 24
   hours, will best provide this patient adequate calories,
   AAs, and lipids?
   A. AAs 10% 700 mL, dextrose 30% 325 mL, lipid 20% 500 mL.
   B. AAs 10% 450 mL, dextrose 70% 400 mL,
   lipid 20% 250 mL.
   C. AAs 10% 800 mL, dextrose 70% 350 mL,
   lipid 20% 250 mL.
   D. AAs 15% 900 mL, dextrose 50% 500 mL,
   lipid 20% 250 mL.

Answer 6

6. Answer: C
   This correct formula provides about 30 kcal/kg of calories,
   1.5 g of protein per kilogram (AA), and 30% of
   total calories as lipid (Answer C). Answer A is incorrect
   because it provides 1000 calories as lipid, which
   is about 62% of the total calories provided. Answer B
   is incorrect because it contains only 0.8 g/kg of AA,
   which is an insufficient amount considering the patient’s
   stress and apparent absence of kidney injury. Answer D
   is incorrect because it contains too much AA.

Question 7

7. A 59-year-old man has been admitted to the hospital
   after several days of vomiting and diarrhea.
   In the emergency department, he had several
   runs of nonsustained ventricular tachycardia. His
   plasma potassium on admission is 2.8 mEq/L.
   After 100 mEq of potassium chloride is infused
   over 24 hours, his repeated K+ is 3.2 mEq/L, and he
   continues to have runs of ventricular tachycardia.
   Other laboratory values include Na+ 143 mEq/L,
   magnesium 1.4 mg/dL, phosphorus 3 mg/dL, Ca2+
   9 mg/dL, and ionized Ca2+ 1.1 mmol/L. Which
   treatment would be best to give next?
   A. Administer potassium chloride 20 mEq intravenously
   over 1 hour each for 4 doses and
   recheck K+.
   B. Administer magnesium sulfate as a 2 g slow
   intravenous infusion over 2 hours.
   C. Administer potassium phosphate 15 mmol
   intravenously over 4 hours.
   D. Administer calcium gluconate 2 g intravenously
   over 5 minutes.

Answer 7

7. Answer: B
   This patient has hypomagnesemia and hypokalemia.
   Correction of hypokalemia requires correction of
   hypomagnesemia to prevent renal loss of K+ (Answer
   B). Magnesium should be administered slowly to avoid
   hypotension and increased renal excretion caused by
   rapid administration. Continued K+ should not be given
   until magnesium is administered (Answers A and C).
   Calcium correction will not have a large effect on K+
   correction (Answer D).

Question 8

8. Which nutritional strategy can best prevent
   gut mucosal atrophy and subsequent bacterial
   translocation?
   A. PN enriched with glutamine.
   B. PN enriched with branched-chain AAs.
   C. Enteral nutrition (EN).
   D. Zinc supplementation.

Answer 8

8. Answer: C
   Enteral nutrition prevents gut mucosal atrophy and subsequent
   bacterial translocation (Answer C). Bacterial
   translocation is the crossing of bacteria from the GI
   tract into the systemic circulation. Enteral nutrition is
   associated with fewer infectious complications than
   PN, which may partly be because of a reduction in bacterial
   translocation (Answers A and B). Zinc does not
   affect atrophy and bacterial translocation (Answer D).

Question 9

9. A female patient (weight 80 kg) in the intensive care
   unit has developed acute kidney injury caused by
   sepsis, and she requires intermittent hemodialysis
   daily to maintain her BUN/SCr ratio at 49:2.5 mg/
   dL. Currently, she is receiving appropriate antibiotics
   and is hemodynamically stable. She has also
   been receiving PN providing 72 g of AAs per day.
   What is the best recommendation for this patient’s
   protein intake?
   A. Reduce AAs to 40 g/day.
   B. Reduce AAs to 64 g/day.
   C. Increase AAs to 96 g/day.
   D. Increase AAs to 160 g/day.

Answer 9

9. Answer: C
   It is a common misconception that all patients with kidney
   failure need protein restriction (Answers A and B).
   This is true for chronic kidney disease patients who are
   not undergoing dialysis. Conversely, if they are undergoing
   dialysis, they do not need protein restriction and
   can receive AA at 1.2–1.5 g/kg/day (Answer C). Answer
   D is incorrect because too much protein is given.

Question 10

Questions 1 and 2 pertain to the following case.
A 65-year-old man (weight 80 kg) with a 3-day history of a body temperature of 102°F (38.9°C), lethargy, and
productive cough is hospitalized for community-acquired pneumonia. His medical history includes uncontrolled
hypertension and coronary artery disease. His vital signs include heart rate 104 beats/minute, blood pressure
112/68 mm Hg, and body temperature 101.4°F (38.6°C). His urine output is 10 mL/hour, K 4 mEq/L, BUN is 46
mg/dL, SCr is 1.7 mg/dL, and WBC is 10.4 × 103 cells/mm3. Other laboratory values are normal.
1. Which is most appropriate at this time?
A. Furosemide 40 mg intravenously.
B. Albumin 25% 100 mL intravenously over 60 minutes.
C. Lactated Ringer solution 1000 mL intravenously over 60 minutes.
D. D5W/0.45% sodium chloride plus potassium chloride 20 mEq/L to infuse at 110 mL/hour.

Answer 10

1. Answer: C
   Although this patient’s blood pressure is not necessarily
   low, it is probably low compared with his baseline,
   considering his history of hypertension. In addition to
   his low blood pressure, his other signs and symptoms
   of intravascular volume depletion include an elevated
   BUN/SCr ratio, an elevated heart rate, and a reduced
   urine output. Crystalloids or colloids are appropriate
   fluids for resuscitation, making lactated Ringer solution
   (Answer C) the best option. Furosemide (Answer
   A) may increase his urine output, but at the cost of further
   depleting the intravascular volume. Albumin 25%
   (Answer B) should be avoided for fluid resuscitation
   because it causes a shift of fluid from the IS space into
   the intravascular space, which can potentiate his dehydration.
   Answer D would be appropriate for a maintenance
   infusion; however, D5W/0.45% sodium chloride
   plus potassium chloride 20 mEq/L would not provide
   optimal replacement of the intravascular space, given
   the distribution in TBF.

Question 11

Questions 1 and 2 pertain to the following case.
A 65-year-old man (weight 80 kg) with a 3-day history of a body temperature of 102°F (38.9°C), lethargy, and
productive cough is hospitalized for community-acquired pneumonia. His medical history includes uncontrolled
hypertension and coronary artery disease. His vital signs include heart rate 104 beats/minute, blood pressure
112/68 mm Hg, and body temperature 101.4°F (38.6°C). His urine output is 10 mL/hour, K 4 mEq/L, BUN is 46
mg/dL, SCr is 1.7 mg/dL, and WBC is 10.4 × 103 cells/mm3. Other laboratory values are normal.

2. After 2 days of appropriate antibiotic treatment, the patient has a WBC of 9 × 103 cells/mm3, and he is afebrile.
   His blood pressure is 135/85 mm Hg, and his urine output is 45 mL/hour. His albumin is 3.2 g/dL, BUN is
   14 mg/dL, and SCr is 1.4 mg/dL. All other laboratory values are normal. His appetite is still poor, and he is
   not taking adequate fluids. He has peripheral intravenous access. Which option is most appropriate to initiate?
   A. Peripheral PN to infuse at 110 mL/hour.
   B. Albumin 5% 500 mL intravenously over 60 minutes.
   C. D5W/0.45% sodium chloride plus potassium chloride 20 mEq/L to infuse at 110 mL/hour.
   D. Lactated Ringer solution to infuse at 75 mL/hour.

Answer 11

2. Answer: C
   This patient has no signs or symptoms of intravascular
   volume depletion; therefore, he does not require fluid
   resuscitation. Because he is not taking adequate fluids
   by mouth, he should be given maintenance intravenous
   fluid to prevent dehydration and electrolyte imbalances.
   This is typically accomplished by a combination of free
   water and 0.45% sodium chloride with K+ (Answer C).
   The infusion rate is calculated as 1500 mL + (60 kg
   × 20 mL/kg) = 2700 mL/24 hours, or about 110 mL/
   hour. Parenteral nutrition (Answer A) is inappropriate
   because there is no evidence that the patient’s GI tract
   is nonfunctional. Albumin 5% (Answer B) or lactated
   Ringer solution (Answer D) should be reserved for fluid
   resuscitation in patients with signs or symptoms of
   intravascular volume depletion.

Question 12

A 72-year-old woman (weight 60 kg) with a history of hypertension has developed hyponatremia after starting
hydrochlorothiazide 3 weeks earlier. She experiences dizziness, fatigue, and nausea. Her serum sodium is 116 mEq/L.
Her blood pressure is 86/50 mm Hg, and heart rate is 122 beats/minute.
3. In addition to discontinuing hydrochlorothiazide, which initial treatment regimen is best?
A. Administer 0.9% sodium chloride infused at 100 mL/hour.
B. Administer 0.9% sodium chloride 500-mL bolus.
C. Administer 3% sodium chloride infused at 60 mL/hour.
D. Administer 23.4% sodium chloride 30-mL bolus as needed.

Answer 12

3. Answer: B
   Although this patient has symptomatic hyponatremia,
   she also has signs of intravascular volume depletion.
   This intravascular volume depletion is a potent stimulus
   for ADH secretion, which will potentiate hyponatremia.
   In patients with hyponatremia and intravascular
   volume depletion, it is important to restore intravascular
   volume first to prevent organ hypoperfusion and to inhibit ADH secretion. Fluid resuscitation should
   be accomplished with 0.9% sodium chloride as a fluid
   bolus, followed by a reevaluation of fluid status (Answer
   B). A slower infusion of 0.9% sodium chloride (Answer
   A) will not restore intravascular volume quickly. Once
   the intravascular volume is restored, ADH secretion
   will cease. This can be followed by a water diuresis,
   with a subsequent rise in the serum sodium concentration.
   Of importance, the patient should be monitored
   closely to prevent a rise in serum sodium greater than
   10–12 mEq/L/day. If serum sodium rises too fast, 0.45%
   sodium chloride can be infused to slow the rate of rise
   of serum sodium concentration. Hypertonic saline
   (Answers C and D) would not be advisable unless the
   patient continues to have symptoms of hyponatremia
   after appropriate fluid resuscitation.

Question 13

A 72-year-old woman (weight 60 kg) with a history of hypertension has developed hyponatremia after starting
hydrochlorothiazide 3 weeks earlier. She experiences dizziness, fatigue, and nausea. Her serum sodium is 116 mEq/L.
Her blood pressure is 86/50 mm Hg, and heart rate is 122 beats/minute.

4. Which is the best treatment goal for the first 24 hours in correcting the patient’s serum sodium from her initial
   value of 116 mEq/L?
   A. Increase Na+ concentration to 140 mEq/L.
   B. Increase Na+ concentration to 132 mEq/L.
   C. Increase Na+ concentration to 126 mEq/L.
   D. Maintain serum sodium of 116–120 mEq/L.

Answer 13

4. Answer: C
   To prevent central pontine myelinolysis in patients
   with hyponatremia, it is recommended that the serum
   sodium concentration be raised by no more than 10–12
   mEq/L in 24 hours (Answer C). Of note, the goal is not
   to achieve a normal serum sodium concentration in 24
   hours. Rapid correction of chronic hyponatremia can
   cause permanent neurologic damage (Answers A and
   B), and because this patient is symptomatic, she should
   not be maintained at her current sodium concentration
   (Answer D).

Question 14

A 72-year-old woman (weight 60 kg) with a history of hypertension has developed hyponatremia after starting
hydrochlorothiazide 3 weeks earlier. She experiences dizziness, fatigue, and nausea. Her serum sodium is 116 mEq/L.
Her blood pressure is 86/50 mm Hg, and heart rate is 122 beats/minute.

5. One day later, the patient has somewhat improved. Her blood pressure is 122/80 mm Hg, and heart rate is
   80 beats/minute. Her serum sodium is 120 mEq/L, and K+ is 3.2 mEq/L; she still feels tired. She is eating a
   regular diet. Her ECG is normal. Which is the best recommendation?
   A. D5W/0.9% sodium chloride plus potassium chloride 40 mEq/L to infuse at 100 mL/hour.
   B. 0.9% sodium chloride infused at 100 mL/hour.
   C. 3% sodium chloride infused at 60 mL/hour.
   D. Potassium chloride 20 mEq by mouth every 6 hours for 4 doses.

Answer 14

5. Answer: D
   This patient has hyponatremia and hypokalemia. In
   patients with hypokalemia, there is a reduction in IC
   K+. To maintain cellular electroneutrality, Na+ will shift
   into cells. As K+ is replaced, Na+ shifts out of cells, and
   the serum sodium concentration rises. Therefore, in this
   case, the hypokalemia should be corrected first, which
   will cause a subsequent improvement in the hyponatremia.
   Because this patient has no ECG changes related
   to the hypokalemia, oral supplementation with K+
   (Answer D) is recommended over intravenous replacement
   (Answer A). A dose of 60–80 mEq/day should
   cause an increase in the K+ concentration by 0.6–0.8
   mEq/L. Because the patient is eating a regular diet, she
   should no longer require intravenous fluids (Answer B).
   Hypertonic saline (Answer C) is incorrect because this
   patient has no serious symptoms of hyponatremia.

Question 15

6. A 74-year-old woman (weight 50 kg) has been receiving isotonic tube feedings at 60 mL/hour for the past
   8 days through her gastrostomy feeding tube. She recently had an ischemic stroke; she is responsive but is not
   able to communicate. Her serum sodium was 142 mg/dL on the day the isotonic formula was initiated, and it
   has risen steadily to 149, 156, and 159 mg/dL on days 3, 4, and 8, respectively, after the start of the tube feedings.
   What is the best treatment for her hypernatremia?
   A. Administer sterile water intravenously at 80 mL/hour.
   B. Administer D5W intravenously at 80 mL/hour.
   C. Administer D5W/0.225% sodium chloride intravenously at 80 mL/hour.
   D. Administer water by enteral feeding tube 200 mL every 6 hours.

Answer 15

6. Answer: D
   This patient has not been given enough water, and she
   cannot communicate (or feel) thirst. This can be prevented
   by administering about 1 mL of water for every
   calorie administered. It should also be prevented by
   monitoring serum sodium concentrations and adjusting
   water intake as needed. To correct the hypernatremia,
   water should be administered, preferably through the
   enteral feeding tube (Answer D). If this is not possible,
   it can be administered intravenously as D5W (Answer
   B or C), but never as sterile water (Answer A). Sterile
   water administered intravenously can cause hemolysis
   and death. The patient’s water deficit (in liters) can be
   estimated with the equation 0.4 × LBW × [(Na+/140)
   − 1]. Water should be replaced over several days, taking
   care to avoid changes in serum sodium greater than
   10–12 mEq/L in 24 hours.

Question 16

7. A 61-year-old man comes to the emergency department with shortness of breath and bilateral lower leg edema.
   Pertinent vital signs and laboratory values include heart rate 30 beats/minute, blood pressure 102/57 mm Hg,
   K+ 7.9 mEq/L, Na+ 139 mEq/L, glucose 278 mg/dL, Ca2+ 8.8 mg/dL, digoxin 2.2 ng/mL, BUN 49 mg/dL, and
   SCr 2.4 mg/dL. His ECG shows wide QRS and peaked T waves. His medical history includes heart failure,
   atrial fibrillation, coronary artery disease, peripheral arterial disease, and diabetes. The patient has peripheral
   intravenous access and an external pacemaker. Which treatment is most appropriate?
   A. Calcium gluconate 10 mL intravenously over 2 minutes.
   B. Insulin 10 units intravenously.
   C. Sodium bicarbonate 50 mEq intravenously over 10 minutes.
   D. Albuterol 10 mg nebulized over 10 minutes.

Answer 16

7. Answer: B
   This patient has ECG changes consistent with hyperkalemia.
   Insulin (Answer B) will have the fastest onset
   and most predictable action of lowering serum potassium.
   Calcium gluconate (Answer A) should only be
   used with caution in this patient because it can potentiate
   digoxin toxicity and bradycardia. The efficacy of
   sodium bicarbonate (Answer C) is not well established.
   Albuterol (Answer D) can be efficacious when added
   to insulin, but it might not be effective in about 40%
   of patients; therefore, it is not recommended as initial
   therapy or as monotherapy for hyperkalemia.

Question 17

8. A 72-year-old woman (weight 65 kg) is switched from a standard enteral formula to a concentrated tube feeding
   designed for patients with kidney disease, because of hyperkalemia. The patient’s baseline and current
   SCr is 1.7 mg/dL, and her urine output is about 50 mL/hour. The tube feeding is infusing at a goal rate of
   35 mL/hour through an NG feeding tube providing 2 kcal/mL, Na+ 41 mEq/L, and 717 mL/L of water. The
   patient’s serum sodium was 140 mEq/L when the tube feeding was initiated a few days ago, and her Na+ is now
   145 mEq/L. What is the best approach for preventing hypernatremia in this patient?
   A. Change to an EN formula with a lower concentration of Na+.
   B. Administer intravenous D5W at 45 mL/hour.
   C. Administer 200 mL of water through a feeding tube every 4 hours.
   D. Reduce the tube feeding to 30 mL/hour.

Answer 17

8. Answer: C
   This patient is receiving a calorie-dense EN formula
   that typically has less water than other enteral products.
   Therefore, although not currently hypernatremic, the
   patient is at risk of developing hypernatremia because
   of insufficient water intake. This can be prevented by
   administering additional water. The preferred route is
   enteral, if possible. The additional water needed daily
   can be estimated as 1 mL/kcal or around 30 mL/kg/day.
   Therefore, if this patient is receiving enteral feeding at
   35 mL/hour × 2 kcal/mL, she is receiving 1680 kcal/
   day. She is receiving only 717 mL of water per liter of
   enteral formula, which is 602 mL/day for the 840 mL
   of enteral feeding daily (35 mL/hour × 24 hours = 840
   mL/day). Because she is receiving 1680 kcal, she needs
   about 1680 mL of water per day. Subtracting the water
   from the feedings from the total needed, 1680 − 602 = 1078 mL is needed. This can be divided and administered
   through the gastric feeding tube at about 180
   mL/dose every 4 hours (Answer C). Of note, the patient
   should be monitored for fluid overload, especially given
   her chronic kidney disease. Given this patient’s stable
   kidney disease and her adequate urine output, she
   should be able to tolerate this amount of free water.
   The amount of free water needed daily is an estimation
   that should be adjusted on the basis of specific patient
   parameters (e.g., serum sodium, input, output, daily
   weight, edema). Free water should not be administered
   as intravenous dextrose (Answer B) unless enteral
   administration is not feasible. Answer A is incorrect
   because reducing Na+ will not prevent hypernatremia;
   the problem is related to too little water rather than too
   much Na+. Answer D is incorrect because the caloric
   goals should not be sacrificed, and they would not eliminate
   the problem of insufficient water administered.

Question 18

9. A 43-year-old male trauma patient (height 75 inches, weight 100 kg) was recently extubated and is receiving
   PN. His PN formula contains 35 kcal/kg, protein 1.2 g/kg, and dextrose infusing at 4.4 mg/kg/minute, and 25%
   of total calories as lipid. He has gradually developed symptoms of hypercapnia and has developed a respiratory
   acidosis. The medical team is considering strategies to correct this to avoid reintubation. Which change
   to the PN formula could best correct this situation?
   A. Change PN to EN and maintain current caloric goals.
   B. Reduce dextrose amount in PN to 3 mg/kg/minute and increase lipid to maintain current caloric goal.
   C. Change electrolytes to the acetate salt in the PN to correct the acid-base imbalance.
   D. Reduce the calories to 25 kcal/kg to prevent overfeeding.

Answer 18

9. Answer: D
   This patient is developing a respiratory acidosis, possibly
   because of overfeeding. Although dextrose is
   metabolized to water and CO2, it generally will not
   cause a respiratory acidosis unless the patient is being
   overfed. Reducing the total calories to 25 kcal/kg
   decreases the risk of overfeeding, and reintubation can
   be avoided (Answer D). Answer A is incorrect because
   patients can be overfed with PN or EN. Answer B is
   incorrect because, even if the dextrose in the PN is
   reduced, the patient can still develop symptoms of overfeeding.
   Answer C is incorrect because the underlying
   (overfeeding) cause should be corrected, rather than
   adjusting the acetate to treat a respiratory acidosis.

Question 19

10. A patient (weight 70 kg) receives propofol at 45 mcg/kg/minute. Propofol is available at a concentration of
    10 mg/mL and is mixed in a 10% lipid emulsion. Assuming the patient is receiving this infusion rate for
    24 hours, which best approximates the total calories provided by the propofol infusion in a 24-hour period?
    A. 200 kcal.
    B. 250 kcal.
    C. 300 kcal.
    D. 500 kcal.

Answer 19

10. Answer: D
    To determine the amount of calories provided by propofol,
    it must first be determined how many milliliters per
    day are infused. For this patient receiving propofol 45
    mcg/kg/minute and weighing 70 kg, 454 mL is infused
    daily (assuming a constant infusion rate). Next, if a 10%
    lipid emulsion provides about 1.1 kcal/mL, it can be calculated
    that 454 mL/day of propofol provides about 500
    kcal/day, making Answer D correct and Answers A–C
    incorrect.

Question 20

11. A patient (weight 65 kg) is receiving PN after abdominal surgery. The PN contains about 1600 kcal, including
    100 g of protein, 500 kcal as lipid, and 200 g of dextrose. The following additives are also included in
    a 24-hour infusion of PN: sodium chloride 50 mEq, sodium acetate 100 mEq, potassium acetate 60 mEq,
    sodium phosphate 30 mmol, magnesium sulfate 12 mEq, calcium gluconate 10 mEq/day, multivitamins
    10 mL, and trace elements 3 mL. The patient has an NG tube in place that is suctioning 400–500 mL/day,
    which is being replaced with an infusion of 0.9% sodium chloride. After 48 hours of PN, the patient has the
    following laboratory values: Na+ 140 mEq/L, K+ 3.8 mEq/L, Cl– 93 mEq/L, serum bicarbonate 35 mEq/L, pH
    7.5, PCO2 47 mm Hg, and bicarbonate 36 mEq/L. Which adjustment to the PN formula is best at this time?
    A. Increase lipids to provide 750 kcal and reduce dextrose to 130 g.
    B. Increase sodium acetate to 150 mEq/day and discontinue sodium chloride.
    C. Increase sodium chloride to 150 mEq/day and discontinue sodium acetate.
    D. Add sodium bicarbonate 50 mEq to PN.

Answer 20

11. Answer: C
    This patient has developed a metabolic alkalosis, probably
    secondary to the loss of gastric fluid through NG
    suctioning. The low serum chloride and elevated serum
    bicarbonate concentrations support this theory. In addition,
    the acid base is consistent with metabolic alkalosis
    with compensatory respiratory acidosis. The treatment
    in this circumstance is to replace the lost fluid with
    0.9% sodium chloride, which is being done. In addition,
    Na+ and K+ can be administered as the chloride
    salt rather than the acetate salt (Answer C). For this
    case, only Na+ is converted to chloride salt, and K+ is
    left as the acetate salt initially. With daily monitoring,
    the ratio of Cl– to acetate can be adjusted further if
    needed. Answer B is incorrect because it would probably
    worsen the metabolic alkalosis as the sodium acetate
    is converted to bicarbonate. Answer A is incorrect
    because hypercapnia is a compensatory response, not
    the primary acid-base disturbance. Answer D is incorrect
    for several reasons. First, it is never advisable to
    add sodium bicarbonate to PN because of incompatibility
    and the risk of calcium-phosphate precipitation.
    Second, sodium bicarbonate is the incorrect treatment
    for metabolic alkalosis because it can worsen alkalosis

Question 21

A 75-year-old woman (weight 50 kg) is receiving PN after an extensive bowel resection. She is expected to require
about 1 week of PN. She is receiving the following macronutrients in her formula: 70% dextrose 300 mL, 20%
lipid 150 mL, and 10% AA 750 mL.
12. If these macronutrients are infused over 24 hours, which choice most closely approximates the total calories
this patient is receiving daily?
A. 20 kcal/kg.
B. 26 kcal/kg.
C. 30 kcal/kg.
D. 35 kcal/kg.

Answer 21

12. Answer: B
    The total calories are calculated by adding the calories
    provided by dextrose, lipid, and AA. Dextrose provides
    714 kcal (210 g × 3.4 kcal/g), lipid provides about 300
    kcal (30 g × 10 kcal/g), and AA provides 300 kcal (75
    g × 4 kcal/g). Adding these together provides calories
    of 1314 kcal/50 kg = 26.3 kcal/kg, making Answer B
    correct and Answers A, C, and D incorrect.

Question 22

A 75-year-old woman (weight 50 kg) is receiving PN after an extensive bowel resection. She is expected to require
about 1 week of PN. She is receiving the following macronutrients in her formula: 70% dextrose 300 mL, 20%
lipid 150 mL, and 10% AA 750 mL.

13. The patient has received the PN formula for 3 days. Her blood glucose concentrations have ranged from
    220 to 280 mg/dL. She has orders for the following sliding scale of regular insulin: blood glucose 200–250
    mg/dL, give 2 units; blood glucose 251–300 mg/dL, give 4 units; and blood glucose 301–350 mg/dL, give
    6 units. She has been receiving 14–16 units of insulin daily through the sliding-scale orders. Her medical
    history is significant for hypertension, diabetes, chronic obstructive pulmonary disease, and colon cancer.
    Treatment was recently initiated with methylprednisolone 60 mg intravenously every 6 hours for a chronic
    obstructive pulmonary disease exacerbation. Today, the dose will be reduced to 40 mg intravenously every
    8 hours. What is the best recommendation for better control of this patient’s blood glucose?
    A. Add insulin glargine 10–20 units/day to PN.
    B. Change 70% dextrose in PN to D5W.
    C. Increase the sliding-scale insulin to 4 units for blood glucose 200–250 mg/dL, 8 units for blood glucose
    251–300 mg/dL, and 12 units for blood glucose 301–350 mg/dL.
    D. Add neutral protamine Hagedorn insulin (NPH) 5 units subcutaneously every 12 hours.

Answer 22

13. Answer: D
    This patient’s hyperglycemia could be attributable to
    either stress or corticosteroids. Because the corticosteroid
    dose is being tapered, the blood glucose concentrations
    will probably decrease with time. For patients
    with a fluctuating blood glucose concentration, it can
    be difficult to add insulin to PN because insulin cannot
    be adjusted in a timely manner. Regardless, Answer
    A is incorrect because long-acting insulin should not
    be added to PN. If insulin is added to PN, it should
    be regular insulin. Although some experts promote
    “permissive underfeeding,” Answer B is incorrect
    because it would provide insufficient calories for this
    patient. Sliding scales of insulin can be useful when used in conjunction with a basal amount of insulin in
    patients with a fluctuating blood glucose concentration.
    However, a sliding scale (Answer C) should not be used
    as the primary intervention for blood glucose control,
    because it is reactive and it fails to prevent hyperglycemia.
    In addition, the sliding scale described recommends
    insulin only when the blood glucose reaches
    200, which is too high. Answer D is correct because it
    provides a basal amount of insulin that can be adjusted
    in a timely manner as the blood glucose concentrations
    fluctuate according to the patient’s status.