Complications of Parenteral Nutrition

Question 1

Which one of the following factors is most likely to contribute to metabolic bone disease in PN-dependent patients?

1: Aluminum toxicity
2: Calcium supplementation
3: Moderate amino acid intake in PN
4: Balanced acetate load in PN

Answer 1

1: Aluminum toxicity

Metabolic bone disease including osteomalacia, osteoporosis and osteopenia has been reported in PN-dependent patients. Aluminum contaminants can be mainly found in parenteral calcium and phosphate salts, trace minerals and vitamins used in making PN solutions. Patients with renal insufficiency are at higher risk for aluminum toxicity due to impaired kidney aluminum excretion. Aluminum toxicity causes osteomalacia by impairing calcium bone fixation, inhibiting the conversion of 25-hydroxyvitamin D to the active 1, 25-dihydroxyvitamin D or reducing parathyroid hormone secretion. In 2000, the FDA issued a rule specifying acceptable aluminum concentrations in large volume parenterals and defined a possible safe upper limit for parenteral aluminum intake at less than 4-5 mcg/kg/day.

Question 2

Which of the following is a risk factor for the development of PN-associated liver complications in PN-dependent patients?

1: Prolonged use of soybean-based lipid injectable emulsion (ILE)
2: Cyclic infusion of PN
3: Supplemental trophic enteral feeding
4: Medication therapy with ursodiol

Answer 2

1: Prolonged use of soybean-based lipid injectable emulsion (ILE)

Omega-6 polyunsatrated fatty acid soybean-based ILE are thought to be proinflammatory and potentially contain toxic phytosterols, which may impair bile flow. Parenteral nutrition associated liver disease risk is decreased by cycling PN, supplementing with enteral feeding, adding ursodiol or increasing the omega 3:omega 6 ratio.

Question 3

A 70-kg adult patient receiving PN providing 3000 kcal/day presents with mild to moderate elevations of serum aminotransferases and mild elevations of bilirubin and serum alkaline phosphatase. This patient is most likely exhibiting what type of PN-associated liver disease (PNALD)?

1: Hepatic steatosis
2: Cholestasis
3: Gallbladder sludging
4: Fulminant hepatic failure

Answer 3

1: Hepatic steatosis

Although the relationship between PN and liver disease has been established, its prevention and treatment remain a relevant clinical dilemma. Often, the etiology of PNALD is multifactorial and diligence is required to identify and treat causative factors. There are 3 basic types of hepatobiliary disorders associated with PN: steatosis, cholestasis, and gallbladder sludging (stones). Hepatic steatosis generally occurs in adults and presents with mild elevations in aminotransferases, serum alkaline phosphatase, and bilirubin concentrations. This particular type of hepatobiliary disorder is most often a complication of overfeeding. Cholestasis, occurring primarily in children, is characterized by impaired biliary secretion. Elevated conjugated bilirubin levels are the most common laboratory manifestation in this population. Finally, gallbladder sludging or stones is thought to result from the lack of enteral stimulation in the GI tract and occurs with long-term PN use. In this question, this adult patient is receiving an inappropriately high amount of calories (overfeeding) and has the accompanying lab values consistent with hepatic steatosis.

Question 4

A 55-year-old male is admitted with an undesired weight loss of 20 pounds during the past month secondary to an ongoing Crohn’s flare up. The patient is found to be at high risk for refeeding syndrome. Which micronutrient should be supplemented?

1: Vitamin A
2: Vitamin K
3: Thiamin
4: Ascorbic acid

Answer 4

3: Thiamin

Thiamin is a water-soluble vitamin and body stores can be easily depleted by malnutrition, weight loss and chronic alcoholism. Carbohydrate intake increases the demand for thiamin, as it is an essential coenzyme in carbohydrate metabolism. Supplementation of thiamin may be indicated in patients at risk for refeeding syndrome due to possible deficiency.

Question 5

Hyperglycemia in a patient receiving PN is associated primarily with what type of sodium/fluid imbalance?

1: Hypertonic hyponatremia
2: Hypotonic hyponatremia
3: Isotonic hypernatremia
4: Hypertonic hypernatremia

Answer 5

1: Hypertonic hyponatremia

Hypertonic hyponatremia may result from hyperglycemia or administration of hypertonic sodium free solutions. Hyperglycemia causes a shift of water out of cells into the extracellular space, resulting in dilution of serum sodium. For every 100 mg/dL increase in serum glucose concentration above 100 mg/dL, the serum sodium would be expected to decrease by approximately 1.6 mEq/L. Treatment should consist of correction of the underlying hyperglycemia, not changes in sodium and water administration, as this is not a true sodium or water imbalance.

Question 6

A long-term PN patient presents with involuntary movements, tremor, and rigidity. Which of the following etiologies may explain these symptoms?

1: Manganese deficiency
2: Manganese toxicity
3: Selenium deficiency
4: Selenium toxicity

Answer 6

2: Manganese toxicity

The early phase of manganese toxicity is characterized by weakness, anorexia, headache, and apathy followed by Parkinson-like features including muscle rigidity, mask-like face, staggered gait, and fine tremor. Toxicity may occur in patients on long-term therapy supplemented with a combination multiple trace element preparation. Cholestasis and biliary obstruction may also increase the risk of toxicity as greater than 90% of manganese excretion is via the bile into the feces, but these abnormalities are not always present. Manganese deficiency in humans is not well-documented. In animals, manganese deficiency manifests in skeletal abnormalities, ataxia, low fertility, low HDL cholesterol levels, abnormal lipid and carbohydrate metabolism, and low insulin production. Selenium deficiency is associated with Keshan disease (a type of cardiomyopathy) and increased oxidative injury. Selenium toxicity is characterized by loss of hair and nails, skin lesions, tooth decay, and peripheral neuropathy.

Question 7

In order to prevent rebound hypoglycemia upon discontinuation of parenteral nutrition (PN), it is recommended the PN infusion rate be reduced over what time span?

1: 0 hours
2: 1-2 hours
3: 2-3 hours
4: 3-4 hours

Answer 7

2: 1-2 hours

Rebound hypoglycemia upon discontinuation of PN may occur, especially in individuals with underlying conditions that affect glucose regulation or those patients requiring large doses of insulin. To reduce the risk of hypoglycemia with cessation of PN, a 1-2 hour taper (e.g. 50% rate reduction) prior to discontinuation is recommended, especially when the patient is unable to take adequate oral or EN feeding. Ordering a point-of-care glucose 30-60 minutes after cessation of PN is recommended to identify and treat rebound hypoglycemia.

Question 8

Which of the following would be the most serious complication of hypertriglyceridemia in a patient receiving parenteral nutrition (PN)?

1: Azotemia
2: Pancreatitis
3: Polyuria
4: Peripheral neuropathy

Answer 8

2: Pancreatitis

Hypertriglyceridemia may occur in some patients receiving lipid injectable emulsion (ILE). If unnoticed and untreated, it may lead to the development of pancreatitis and altered pulmonary function. These complications can be avoided by prudent monitoring of serum triglyceride levels during the administration of PN formulations including ILE. Safe Practices for Parenteral Nutrition (2004) include recommendations to infuse ILE at rates to avoid serum triglyceride levels greater than 400 mg/dL in adults and greater than 200 mg/dL in neonates. If serum triglycerides are elevated, withholding ILE may be indicated.

Question 9

All of the following are potential causes of hyperglycemia in a patient receiving PN EXCEPT

1: carbohydrate administration > 5 mg/kg/min.
2: obesity.
3: sepsis.
4: renal failure.

Answer 9

4: renal failure.

Excess carbohydrate administration has been associated with hyperglycemia, hepatic steatosis and increased carbon dioxide production. Parenteral carbohydrate administration should not exceed 5 mg/kg/min or 20-25 kcal/kg/day. Stress-associated hyperglycemia can develop in patients with sepsis as a result of insulin resistance, increased gluconeogenesis and glycogenolysis and suppressed insulin secretion. Insulin resistance may be exacerbated in obese patients during times of stress. Patients with renal failure demonstrate a prolonged insulin half-life as the kidney accounts for ~40-50% of its clearance from systemic circulation. Research studies with a higher incidence of renal failure have also shown a higher incidence of severe hypoglycemia. Insulin therapy should be altered for these individuals.

Question 10

All of the following are risk factors for the development of rebound hypoglycemia after cessation of PN EXCEPT

1: malnutrition.
2: hepatic dysfunction.
3: hypertension.
4: renal insufficiency.

Answer 10

3: hypertension.

Rebound hypoglycemia occurs when elevated endogenous insulin levels do not adjust to the reduced dextrose infusion following cessation of PN. Although rebound hypoglycemia is not a universal occurrence, some patients may be at higher risk because of underlying conditions that affect glucose regulation. These patients include those with malnutrition and renal or liver disease however hypertension alone should not predispose one to hypoglycemia. A one to two hours taper at the end of PN infusion, cutting the rate in half may benefit in reducing the risk of rebound hypoglycemia.

Question 11

The preferred site for placement of a central venous acces device (CVAD) for adult patients to reduce the risk of infection is

1: subclavian.
2: internal jugular.
3: femoral.
4: external jugular.

Answer 11

1: subclavian.

The density of skin flora at the catheter site is a major contributing factor for catheter-related blood stream infections (CRBSI). Guidelines recommend that CVADs be placed in a subclavian site instead of a jugular or femoral site to reduce the risk of infection. The external jugular is not a preferred location for a CVAD for parenteral nutrition.

Question 12

Catheter related thrombosis caused by fibrin build up within blood vessels adhering to a central venous catheter is called

1: fibrin sheath.
2: fibrin tail.
3: intraluminal thrombus.
4: mural thrombus.

Answer 12

4: mural thrombus.

A mural thrombus develops when fibrin builds up inside the vein and causes the vascular access device to adhere to the vessel wall. A fibrin sheath is a layer of fibrin that develops around the outside of a central venous catheter (CVC) secondary to aggregation of fibrin from the presence of a central venous catheter within a vein. A fibrin tail or flap is fibrin build up on the CVC tip that will allow for infusion through the CVC, but will inhibit withdrawal of blood. Intraluminal thrombus is a clot within the catheter lumen and is caused by inadequate flushing and blood reflux.

Question 13

The use of 0.1N hydrochloric acid is most effective for clearing catheter occlusions due to precipitation of

1: calcium-phosphate.
2: tobramycin.
3: phenytoin.
4: lipid residue.

Answer 13

1: calcium-phosphate.

The use of 0.1N hydrochloric acid has been reported effective in clearing catheters with crystalline occlusions because its acidic pH is favorable for calcium and phosphate solubility. Clinicians should be aware, however, that direct infusion of hydrochloric acid into the venous system can be associated with fever, phlebitis, and sepsis. For catheter occlusions due to precipitates associated with medications in the high pH range such as tobramycin and phenytoin, sodium bicarbonate 1 mEq/mL has been anecdotally reported to be effective. Seventy percent ethanol is the most effective solvent to dissolve lipid residue.

Question 14

A 40-year-old male receiving chronic PN therapy (initiated 15 years ago) secondary to massive bowel resection develops metabolic bone disease. His current 12-hour cyclic PN formula provides 5 g/kg/day dextrose, 2 g/kg/day protein and 1 g/kg/day of fat. What is the most appropriate intervention to reduce hypercalciuria?

1: Increase calcium gluconate
2: Decrease phosphorus supplementation
3: Shorten PN infusion time to 10 hours
4: Decrease amino acid content of PN solution

Answer 14

4: Decrease amino acid content of PN solution

The most important contributor to metabolic bone disease is a negative calcium balance. Hypocalcemia occurs as a result of decreased calcium intake and/or increased calcium urinary excretion. Factors that cause hypercalciuria include: excessive calcium and inadequate phosphorus supplementation, excessive protein in PN solutions, cyclic PN infusions, and chronic metabolic acidosis. The most appropriate intervention for this patient is protein reduction. Ideally, protein doses for long-term PN provision should not exceed 1.5 g/kg/day. Although the exact mechanism of protein-induced hypercalciuria is unknown, it could be related to an increased glomerular filtration rate or increased excretion of sulfates, ammonia, and urinary titratable acidity that decreases renal calcium reabsorption.

Question 15

The best approach to prevent PN-induced cholelithiasis is administration of

1: choline.
2: cholecystokinin-octapeptide (CCK-OP).
3: ursodiol.
4: oral or enteral feeding.

Answer 15

4: oral or enteral feeding.

The best approach to preventing cholelithiasis is early initiation of oral or enteral feeding, even in small amounts, to stimulate cholecystokinin secretion, bowel motility and gallbladder emptying. Injections of CCK-OP to induce gall bladder contractions and reduce biliary sludge have yielded mixed results and caused gastrointestinal intolerance in some patients. Although ursodiol has been shown to improve bile flow, doses of 6-15 mg/kg/day have yielded mixed and limited results. In addition, ursodiol is only available in an oral dosage form and its absorption may be limited in patients with intestinal resection. The role of choline in the pathogenesis of cholelithiasis has not been determined.

Question 16

All of the following are considered as short-term complications of home parenteral nutrition EXCEPT

1: dehydration.
2: metabolic bone disease.
3: refeeding syndrome.
4: catheter malposition.

Answer 16

2: metabolic bone disease.

Electrolyte abnormalities, dehydration and catheter malposition are more common short-term complications of home parenteral nutrition. Metabolic bone disease has been recognized as a concern in long-term home parenteral nutrition patients. The contribution of the PN formulation to the development of bone disease is unclear.

Question 17

Which of the following is most likely responsible for elevated serum bicarbonate levels in a home parenteral nutrition (PN) patient?

1: Excess chloride salts in the PN
2: Diarrhea
3: Excess acetate salts in the PN
4: Acute renal failure

Answer 17

3: Excess acetate salts in the PN

An elevated serum bicarbonate level is one of the markers of metabolic alkalosis. Metabolic alkalosis may be caused by nasogastric suctioning, volume depletion and diuretic use. In a PN patient, excess use of acetate, which is metabolized to bicarbonate, may precipitate a metabolic alkalosis. Excess chloride, diarrhea and acute renal failure are common causes of metabolic acidosis.

Question 18

The clinical presentation of refeeding syndrome includes all of the following EXCEPT

1: respiratory failure.
2: seizures.
3: cardiac arrythmias.
4: dehydration.

Answer 18

4: dehydration.

Electrolyte abnormalities that may occur with refeeding syndrome include sodium retention, hypophosphatemia, hypokalemia, and hypomagnesemia. Sodium retention usually occurs in the early phase of the refeeding syndrome and is exacerbated by excessive sodium and fluid intake. This may lead to fluid overload, pulmonary edema, and cardiac decompensation. Severe hypophosphatemia has been reported to cause respiratory failure and seizures. Severe hypokalemia and hypomagnesemia predispose patients to cardiac arrhythmias and neuromuscular adverse effects such as weakness and muscle cramps

Question 19

A 75-year-old female with moderate malnutrition is status-post radical cystectomy with ileal conduit. She weighs 50kg, and she has a 20-gauge IV access in the left cephalic vein. She is initiated on a PPN solution at 125mL/h. This formula contains 210 grams of dextrose, 75 grams of amino acids, and 45 grams of fat. Which of the following complications is she at greatest risk for developing?

1: Fluid overload
2: Hypertriglyceridemia
3: Azotemia
4: Hyperglycemia

Answer 19

1: Fluid overload

Current guidelines for adults recommend the following maximum amounts for PN components: 30-40 mL/kg/day of fluid, 7 g/kg/day of carbohydrates, 2.5 g/kg/day of fat, and 2 g/kg/day of protein. This formula provides 60 mL/kg/day which exceeds recommended maximum daily fluid intake. PPN has to be administered in larger volumes to provide beneficial calories while avoiding venous access compromise (phlebitis, thrombosis, thrombophlebitis, extravasation). Patients that receive PPN must have good peripheral access, the ability to tolerate large volumes of fluid, and a contraindication to central venous access. PPN should be administered for at least five days with no more than two weeks of total therapy. Contraindications for PPN include significant malnutrition, severe metabolic stress, large nutrient or electrolyte needs, fluid restriction, greater than two week need for PN support, and renal and liver compromise.

Question 20

A 68-year-old female with normal liver function and a lactate of 1 mmol/L is in acute kidney injury status-post colon resection and is receiving PN. She has the following arterial blood gas (ABG) results: pH=7.31, PCO2=36 mm Hg, and serum bicarbonate=20 mEq/L. What is the most appropriate PN intervention?

1: Maintain current chloride:acetate ratio
2: Increase chloride:acetate ratio
3: Decrease chloride:acetate ratio
4: Decrease calorie content of PN

Answer 20

3: Decrease chloride:acetate ratio

This patient is experiencing a metabolic acidosis, likely related to acute kidney failure, as evidenced by a decrease in pH (7.35-7.45), a normal PCO2 (35-45 mm Hg), and a decreased serum bicarbonate (22-26 mEq/L). The most appropriate nutrition intervention is to decrease the chloride:acetate ratio in the PN solution. Acetate is converted to bicarbonate by the liver which should correct the metabolic acidosis.

Question 21

What feature of a Groshong® Central Venous Catheter reduces the risk of catheter occlusion?

1: Pressure sensitive three-way valve
2: Large lumen(s) size
3: Heparin coated tip
4: Soft grade medical silicon tubing

Answer 21

1: Pressure sensitive three-way valve

A Groshong CVC has a three-position, pressure-sensitive valve that restricts blood backflow and air embolism by remaining closed when not in use. This reduces the need for catheter clamping. When the valve is closed it prevents blood from entering the CVC and clotting. This eliminates the need for heparin flushes to maintain catheter patency, but the CVC should be flushed with normal saline after medication administration or blood aspiration to ensure the valve is in the closed position.

Question 22

A patient receiving chronic PN therapy develops an intraluminal clot in his (or her) central venous access device. What is the most appropriate pharmacological intervention to clear this access device?

1: Heparin 100 units/mL
2: Alteplase 2mg/2mL
3: Argatroban 350 mcg/kg
4: Streptokinase 10,000 units

Answer 22

2: Alteplase 2mg/2mL

Conventional therapy for an occluded central venous access device (CVAD) due to an intraluminal clot or fibrin sheath is local thrombolytic therapy with a low dose agent in a single or repeated bolus. Cathflow (Alteplase) is the only FDA-approved thrombolytic agent for CVAD occlusions. A dose of 2 mL, or 110% of the volume of the catheter lumen if less than 2 mL (maximum dose 2 mg), is placed in the catheter lumen. Alteplase catalyzes the conversion of clot-bound plasminogen to plasmin and initiates fibrinolysis. In clinical trials, one 2 mg/2 mL dose of alteplase restored function in 67-74% of occluded CVADs and was found to be more effective than urokinase 500 IU. Use of heparin 100 units/mL is appropriate for catheter flushing not for treatment of CVAD occlusions. Neither argatroban nor stepretokinase is approved for clearance of catheter thrombosis.

Question 23

A patient is receiving PN through a tunneled catheter in the IJ. He has a low grade fever 38.1 and is mildly tachycardic (HR 110), but blood cultures are negative. There is some mild redness and tenderness but no purulence at the catheter exit site. How is this exit site infection best managed?

1: Remove central venous access device (CVAD)
2: Exchange catheter over a guidewire
3: Initiate systemic antimicrobial therapy
4: Apply topical antibiotic ointment

Answer 23

3: Initiate systemic antimicrobial therapy

A clinical exit site infection is defined as erythema, tenderness or purulence within 2 cm of the catheter exit site. Management of catheter exit site infection includes culture of any drainage from the catheter exit site in addition to blood cultures. Topical antimicrobial agent on the basis of the exit site culture can be used if there is no purulence from the catheter exit site and no clinical signs of sepsis. If other IV access is unavailable or if the patient is at increased risk for bleeding due to hypocoagulability in the setting of CVAD infection, then it is recommended to exchange the catheter over guide wire. Systemic antimicrobial treatment is used in the presence of purulent drainage from the catheter exit site or if topical treatment is unsuccessful. The catheter should be removed if systemic antimicrobial treatment fails or if the patient has clinical signs of sepsis.

Question 24

A PN-dependent patient with an average daily ileostomy output of 3L presents with BUN/serum creatinine ratio of 30:1 and mild hyponatremia. What is the most appropriate PN intervention for this patient?

1: Increase sodium, restrict protein
2: Increase sodium, increase fluid
3: Increase fluid, restrict protein
4: Decrease sodium, increase fluid

Answer 24

2: Increase sodium, increase fluid

Patients with ileostomy or small bowel fistula output are at risk for loss of water and electrolytes. Sodium content of ileostomy output can be as high as 100 mEq/L. A high BUN/Cr ratio of 20:1 indicates volume depletion. Hyponatremia can result when fluid replacement does not contain adequate sodium to account for ileostomy losses.

Question 25

The use of 70% ethyl alcohol is most effective for clearing catheter occlusions due to precipitation of

1: calcium-phosphate.
2: lipid residue.
3: phenytoin.
4: tobramycin.

Answer 25

2: lipid residue.

The treatment for catheter occlusion depends on what precipitate is occluding the catheter. Patients receiving TPN who have poor flushing habits may encounter lipid sludge and deposits leading to catheter occlusion. 70% ethyl alcohol assists with lipid deposits as lipids are soluble in alcohol. Precipitation from acidic medications (i.e., vancomycin) or from calcium-phosphorous precipitation can be cleared with 0.1-N hydrochloric acid (HCl). Occulsion from basic medications (i.e., phenytoin, oxacillin) can be cleared with 8.4% sodium bicarbonate or 0.1-N NaOH.

Question 26

The most common route of infection for a tunneled central venous access device (CVAD) is

1: extraluminal colonization of the catheter.
2: contamination of the catheter hub.
3: contamination of the infusate.
4: hematogenous seeding from another focus of infection.

Answer 26

2: contamination of the catheter hub.

Contamination of the catheter hub and intraluminal infection is the most common route of infection for tunneled CVADs or implantable devices. In contrast, the pathogenesis of nontunneled CVAD infection is often related to extraluminal colonization of the catheter or intraluminal colonization of the hub and lumen of the CVAD. Occasionally, catheters might become hematogenously seeded from another focus of infection. Rarely, infusate contamination leads to catheter-related bloodstream infection.

Question 27

A patient arrives in your clinic complaining of intermittent catheter malfunction. You identify that the catheter malfunction is relieved by raising the patient’s arm where the catheter is located. Which condition should be suspected?

1: Fibrin sheath
2: Pinch-off syndrome
3: Superior vena cava syndrome
4: Catheter migration

Answer 27

2: Pinch-off syndrome

Pinch-off syndrome occurs when the catheter is being compressed between the first rib and the clavicle, causing intermittent compression and pinching. This can lead to intermittent occlusion of infusion and aspiration and an increased risk of catheter fracture. Changes in the patient’s position can widen or narrow the angle between the rib and clavicle, usually by raising or lowering the arm, which can relieve occlusion of the catheter. This is the hallmark sign of the syndrome. The external portion of the catheter may frequently tear, requiring repair as a result of the increased pressure required to overcome the compressed catheter. The treatment is removal of the catheter and reinsertion in a more lateral position in the subclavian vein or placement in the internal jugular vein.

Question 28

All of the following conditions predispose a patient to the refeeding syndrome EXCEPT

1: chronic alcoholism.
2: malabsorptive syndromes.
3: weight loss after bariatric surgery.
4: poor oral intake for 3 days.

Answer 28

4: poor oral intake for 3 days.

Conditions that predispose patients to the refeeding syndrome include chronic starvation, prolonged fasting or minimal oral intake (>7 days), chronic alcoholism, anorexia nervosa, malabsorption syndromes, morbid obesity followed by significant weight loss, and wasting diseases such as cancer and AIDS.

Question 29

Which of the following illustrates the most common electrolyte imbalances observed in patients with refeeding syndrome?

1: Hypokalemia, hyperphosphatemia, hypocalcemia
2: Hyperkalemia, hyperphosphatemia, hypocalcemia
3: Hypokalemia, hypophosphatemia, hypermagnesemia
4: Hypokalemia, hypophosphatemia, and hypomagnesemia

Answer 29

4: Hypokalemia, hypophosphatemia, and hypomagnesemia

Refeeding syndrome is a potentially lethal condition that can result from fluid and electrolyte shifts in malnourished patients undergoing refeeding of oral, enteral, or parenteral nutrition. The syndrome is characterized by alterations in electrolytes and vitamins. Hypokalemia, hypophosphatemia, and hypomagnesemia commonly occur and are associated with significant morbidity and mortality. Identification of patients at high risk for refeeding syndrome is essential in providing nutrition support to malnourished patients.

Question 30

A patient with refractory hypokalemia should be assessed for what related electrolyte disorder?

1: Hypernatremia
2: Hyponatremia
3: Hyperphosphatemia
4: Hypomagnesemia

Answer 30

4: Hypomagnesemia

Magnesium is important in the regulation of intracellular potassium. Hypomagnesemia may result in refractory hypokalemia, likely due to accelerated renal potassium loss or impairment of sodium-potassium pump activity. When hypokalemia and hypomagnesemia coexist, magnesium deficiency should be corrected to facilitate the correction of hypokalemia.

Question 31

Manganese toxicity is a concern for long-term parenteral nutrition (PN) patients due to its presence in trace element mixtures and as a contaminant from other PN solution components. Symptoms of manganese toxicity are associated most commonly with accumulation of the mineral in which organ?

1: Kidney
2: Brain
3: Muscle
4: Heart

Answer 31

2: Brain

Manganese absorption from the gastrointestinal tract is normally 6-16% of dietary intake. When manganese is provided by the parenteral route there is 100% bioavailability because the gastrointestinal tract is bypassed. Manganese is primarily excreted in the feces via bile. Therefore patients with impaired biliary excretion or those who receive amounts in excess of needs are at risk for brain tissue accumulation and subsequent affects on the central nervous system. Manganese toxicity can be monitored by MRI brain imaging or erythrocyte or whole-blood assessment since 60-80% of manganese is contained in red blood cells.

Question 32

A critically ill 75-year-old male with pneumonia and sepsis who weighs 63 kg is receiving PN containing 2800 kcal and 100 g amino acids per day. He has the following arterial blood gas (ABG) results: pH=7.32, PCO2=49 mm Hg, and serum bicarbonate=25 mEq/L. What is the most appropriate PN intervention?

1: Increase calorie content of PN
2: Increase chloride:acetate ratio
3: Decrease chloride:acetate ratio
4: Decrease calorie content of PN

Answer 32

4: Decrease calorie content of PN

This patient is experiencing a respiratory acidosis as evidenced by a decrease in pH (7.35-7.45), an elevated PCO2 (35-45 mm Hg), and a normal serum bicarbonate (22-26 mEq/L). It is noted that normal lab ranges will vary with different laboratories. He is currently receiving ~45 kcal/kg/day. The most appropriate nutritional intervention is to decrease the total calorie content of the PN regimen. Overfeeding should be avoided as excessive calorie supplementation can lead to hypercapnia due to excessive carbon dioxide production relative to oxygen consumption.

Question 33

The most accurate method of diagnosing PN-associated metabolic bone disease is to measure

1: bone mineral density.
2: urinary calcium concentrations.
3: serum vitamin D concentration.
4: serum parathyroid hormone concentrations.

Answer 33

1: bone mineral density.

It is unclear how often PN-associated metabolic bone disease occurs. It is often asymptomatic and occurs in the face of normal biochemical parameters. The risk for metabolic bone disease is greatest for patients receiving long-term PN and corticosteroid therapy. Fortunately, bone mineral density can be assessed accurately and metabolic bone disease can be diagnosed early so that appropriate treatment can be instituted.

Question 34

Which one of the following co-morbidities is NOT a risk factor for the development of metabolic bone disease for a patient on long-term parenteral nutrition?

1: Crohn’s disease
2: Ovarian cancer
3: Short bowel syndrome
4: Hypothyroidism

Answer 34

4: Hypothyroidism

Nearly every condition requiring long-term PN can predispose a patient to metabolic bone disease (MBD). Patients with Crohn’s disease are at risk for MBD if they have malabsorption of calcium and vitamin D or use corticosteroids to control their disease. Patients with cancer may have decreased food intake and altered calcium and vitamin D metabolism associated with surgery or chemoradiation. MBD may also develop in cancer patients as a result of therapy-induced amenorrhea or the elevation of cytokines or parathyroid-like peptides. There is also evidence that renal wasting of calcium may occur in individuals with short bowel syndrome. Hyperthyroidism (not hypothyroidism) is a secondary cause of osteoporosis.

Question 35

A rise in which of the following laboratory values would most likely indicate cholestasis?

1: Prothrombin time
2: Asparate aminotransferase/Alanine aminotransferase ratio
3: Cholesterol
4: Conjugated (direct) bilirubin

Answer 35

4: Conjugated (direct) bilirubin

Elevations of alkaline phosphatase, gamma glutamyltransferase and conjugated (direct) bilirubin most likely represent cholestasis or biliary obstruction. Elevated serum conjugated bilirubin, typically defined as >2 mg/dL, is considered a prime indicator of cholestasis. Prothrombin time is an important marker of synthetic function, but is not specific for cholestasis. Abnormalities in aminotransferases are indicative of hepatocellular injury. Cholesterol is not a marker of cholestasis.

Question 36

During long-term PN administration, hepatobiliary complications can best be prevented by

1: adding carnitine to the PN formula.
2: discontinuing lipid injectable emulsion (ILE).
3: converting to cyclic administration.
4: reducing magnesium.

Answer 36

3: converting to cyclic administration.

Hepatic dysfunction can result from long-term administration of PN. Conversion to cyclic administration allows the body to oxidize fat and results in lower insulin levels as well as improved liver enzymes. It is important to avoid excess calories as excess calorie administration will result in steatosis. In addition, initiation of enteral feeding stimulates bile flow and may protect against gut bacterial translocation. If hepatic dysfunction occurs, serum concentrations of trace elements such as manganese and copper should be monitored on a regular basis. These elements may need to be removed from the PN solution if serum levels are elevated. Carnitine is not present in any PN formulation. Carnitine may be added to PN in patients with a documented deficiency or those who are susceptible to a deficiency. The role of carnitine remains to be established. Long-term discontinuation of ILE will put the patient at risk of deficiency.

Question 37

A patient has been receiving PN through a central venous catheter (CVC) for the past week while in the hospital. They now present with shortness of breath, cough, and cyanosis of the face, neck, shoulder, and arms. What type of device complication is characterized by this patient’s symptoms?

1: Tunnel infection
2: Pinch-off syndrome
3: Superior vena cava syndrome
4: Thrombosis

Answer 37

3: Superior vena cava syndrome

Tunnel infection can be characterized by pain, swelling, erythema, or induration along the subcutaneous tract of a tunneled catheter. Pinch-off syndrome is a complication of subclavian tunneled central catheters with intermittent or permanent occlusion which are related to postural changes. Thrombosis often presents with chest pain, earache, jaw pain, swelling of the arm, shoulder, neck, or face on ipsilateral catheter side, or leaking at the exit or insertion site. Superior vena cava syndrome is characterized by shortness of breath, dyspnea, cough, cyanosis of face, neck, shoulder and arms, and distended chest or neck veins.

Question 38

Your patient develops sudden chest pain and shortness of breath following placement of a central line for parenteral nutrition support. A pneumothorax is suspected and radiographically confirmed. This situation should be viewed as a

1: sentinel event.
2: process measure.
3: clinical measure event.
4: accountability measure.

Answer 38

1: sentinel event.

A sentinel event is a patient safety event of an unexpected occurrence involving death or serious physical or psychological injury, or the risk thereof. Serious injury specifically includes loss of limb or function. Such events are called “sentinel” because they signal the need for immediate investigation and response. The Joint Commission’s sentinel event policy is designed to help organizations identify sentinel events and take action to prevent their recurrence. Examples of sentinel events include medication errors, wrong site surgery, restraint-related deaths, blood transfusion errors, and operative or postoperative complications. A process measure has a scientific basis which focuses on a process that leads to a certain outcome. Clinical measure events evaluate the processes or outcomes of care associated with the delivery of clinical services. Accountability measures are quality measures that emphasize research, proximity, accuracy, and adverse effects in order to result in positive patient outcomes.

Question 39

Which of the following is an etiology of a thrombotic catheter occlusion?

1: catheter migration during use.
2: formation of lipid deposits.
3: calcium-phosphate precipitate.
4: fibrin sheath formation.

Answer 39

4: fibrin sheath formation.

A fibrin sheath, or fibrin sleeve, is a thrombotic catheter occlusion and develops when fibrin adheres to the external surfaces of the catheter. Nonthrombotic catheter occlusions can result from mechanical obstructions, drug or mineral precipitates, or lipid deposits. Mechanical obstruction may reflect catheter migration or malposition that occurs during insertion or use. Precipitates that form due to drug crystallization, drug-drug incompatibilities, or drug-solution incompatibilities can produce catheter occlusion

Question 40

The most effective strategy to decrease the risk of catheter-associated sepsis is use of

1: povidone-iodine as a skin preparation.
2: antibiotic ointment at catheter exit site.
3: antibiotic prophylaxis during catheter insertion.
4: full-barrier precautions during catheter insertion.

Answer 40

4: full-barrier precautions during catheter insertion.

Several strategies have been investigated to decrease the risk of catheter-associated sepsis. Use of full-barrier precautions during catheter insertion (mask, cap, sterile gloves, long-sleeve gowns, and sheet drapes) reduces the incidence of catheter-related infections more than the use of only sterile gloves and drapes alone. Skin preparation with chlorhexidine results in lower incidence of microbial colonization than povidone-iodine. Prophylactic use of antibiotic ointment at the catheter exit site encourages the development of resistant flora and should be avoided. Antibiotic prophylaxis during catheter insertion has not been demonstrated to reduce the incidence of catheter-associated sepsis.

Question 41

A patient in an acute care hospital has undergone placement of a central venous access device (CVAD) for PN infusion. Which evidence-based intervention should be implemented to reduce the risk of CVAD-related infection?

1: Administration of antibiotics prior to CVAD insertion
2: Use standard contact barrier precautions during CVAD insertion
3: Cleansing of CVAD insertion site with 2% alcohol preparation
4: Training of nursing staff to maintain CVAD

Answer 41

4: Training of nursing staff to maintain CVAD

According to the Centers for Disease Control and Prevention, research supports the following recommendations as primary interventions for reducing risks of central venous access device-related infections: (1) using maximal barrier technique during catheter insertion, (2) cleansing insertion sites with 2% chlorhexidine preparation, and (3) education and training of health care personnel. Administering antibiotics prior to inserting central venous catheters has not been shown to be effective in reducing the rates of central venous access device-related infections.

Question 42

A patient receiving PN that has chills, fever, positive blood cultures, but no redness or purulence at the catheter exit site probably has which of the following types of catheter infection?

1: Tunnel infection
2: Exit site infection
3: Catheter-related phlebitis
4: Catheter-related bloodstream infection

Answer 42

4: Catheter-related bloodstream infection

Catheter-related infections have been defined to allow for more accurate identification of the type of infection. A catheter-related bloodstream infection includes bacteremia/fungemia in a patient with an intravascular device with at least one positive blood culture, clinical manifestations of infection such as fever, and no apparent source except the catheter. Catheter-related blood stream infections often present without redness or purulence at the catheter site.

Question 43

A critically ill patient has been receiving parenteral nutrition providing 45 kcals/kg. The consequences of providing excessive calories to a critically ill patient include all of the following EXCEPT

1: Fatty infiltration of the liver.
2: Ventilator weaning failure.
3: Elevated phosphate.
4: Elevated blood sugar.

Answer 43

3: Elevated phosphate.

Overfeeding can contribute to adverse consequences, especially in mechanically ventilated patients. Providing calories in excess of 25-30 kcals/kg, unless indirect calorimetry results show an REE above this range, has been associated with hepatic steatosis, failure to wean from the ventilator with hypercapnia, and hyperglycemia. Elevated phosphate would be expected only if the amount in parenteral nutrition solution exceeded renal excretion.

Question 44

A patient presents to clinic with a suspected catheter occlusion. All of the following are appropriate initial actions EXCEPT to

1: determine if the occlusion is relieved with postural changes.
2: remove the dressing and check for kinks in the tubing.
3: replace the catheter over a guidewire.
4: review recent flushing techniques with the patient.

Answer 44

3: replace the catheter over a guidewire

When a patient presents with a suspected catheter occlusion, a systematic approach should be taken to prevent unnecessary catheter removals and/or unnecessary instillations of compounds to relieve the catheter occlusion. Steps to insure this include: (1) obtain thorough history of signs/symptoms of catheter malfunction from the patient; (2) double-check catheter function for patency and blood aspiration; (3) check for mechanical causes of occlusions (clamps, kinked tubing, tight sutures, replace needle if implanted vascular access port) and assess if occlusion is related to postural changes (rolling of shoulder or raising or lowering of arm on the side of the catheter); (4) obtain thorough history of recent flushing techniques, medication infusions, and blood aspiration; and (5) assess for physical signs of edema, redness, pain, or dilated vessels. From these steps, a clinician can determine if further diagnostic tests are needed, the catheter requires removal, or if compounds should be instilled to clear a clot or precipitate within the catheter.

Question 45

A 60-year-old female (height 152 cm, weight 45 kg) is receiving PN for a rectovaginal fistula. The PN formula consists of the following components: 70 grams protein, 400 grams dextrose, and 25 grams fat in a total volume of 1.5 liters, including all electrolytes and additives, which is infused continuously over 24 hours daily. Which one of the following complications is she at greatest risk for developing?

1: Hypertriglyceridemia
2: Azotemia
3: Hyperglycemia
4: Pulmonary edema

Answer 45

3: Hyperglycemia

Current guidelines for adults recommend the following maximum amounts for PN components: 7 g carbohydrates/kg/day and 2.5 g fat/kg/day. Protein and fluid requirements for adults are estimated at 0.8 - 2 g-protein /kg/day and 30-40 mL fluid/kg/day. Hyperglycemia from dextrose is the most likely complication this patient will develop because she is receiving more than the recommended daily amount of carbohydrate (10.9 g carbohydrates/kg/day). The other components in this PN formula are within recommended ranges (1.56 g protein/kg/day, 0.56 g fat/kg/day, and 33 mL fluid/kg/day).

Question 46

Discontinuation of lipid injectable emulsion (ILE) is recommended treatment for catheter-related bloodstream infection due to

1: Escherichia coli.
2: Staphylococcus aureus.
3: Pseudomonas aeruginosa.
4: Malassezia furfur.

Answer 46

4: Malassezia furfur.

Malassezia furfur is classically associated with superficial infections of the skin and associated structures. This yeast has been reported as a cause of catheter-related blood stream infections. This occurs most commonly in premature infants and patients receiving PN containing ILE. The ILE presumably provides growth factors required for replication of the organism. Appropriate treatment of patients requires administration of antifungal therapy, discontinuation of ILE, and removal of the intravascular catheter, especially with nontunneled catheter infections.

Question 47

Excess carbohydrate administration in PN has been associated with

1: hypercalcemia.
2: hepatic steatosis.
3: decreased CO2 production.
4: metabolic bone disease.

Answer 47

2: hepatic steatosis.

Excess carbohydrate administration has been associated with hepatic steatosis as excess carbohydrates deposit in the liver as fat. Providing balanced dextrose and fat calories seems to decrease the incidence of steatosis, possibly by decreasing hepatic triglyceride uptake and promoting fatty acid oxidation. Metabolic bone disease and hypercalcemia are unrelated to carbohydrate administration. Excess carbohydrate administration has been shown to cause increased carbon dioxide production.

Question 48

Patients with diabetes who are receiving PN

1: should have blood glucose checked every 8-10 hours.
2: have an increased risk for catheter related infections.
3: have a maximum carbohydrate infusion rate of 7mg/kg/min of dextrose.
4: should have initial insulin amount of 1.0 unit of regular insulin/gm dextrose infused.

Answer 48

2: have an increased risk for catheter related infections.

The standard for glucose checks in a diabetic patient on PN is every 2-6 hours, depending on facility protocol, insulin requirements, and general clinical condition. Diabetic patients receiving PN should receive a maximum infusion rate of 5 mg/kg/min, starting at a 100-150gms dextrose/day to avoid hyperglycemia and refeeding. The estimated initial amount of insulin to add to PN for a diabetic is 0.05-0.1 unit insulin/gm dextrose, increased daily to achieve glycemic goals by adding 2/3 of previous days sliding scale insulin. The increase in blood glucose levels seen in diabetic and critically ill patients is associated with higher frequency of infection. The intense counter-regulatory hormone and cytokine responses to severe disease and the excessive administration of glucose, usually as PN, could contribute to hyperglycemia and the associated infectious complications.

Question 49

A critically ill 42 year old male status post small bowel resection for Crohn’s disease is receiving PN for severe post-operative ileus with NG tube output of 2.5-3 liters per day. He has the following arterial blood gas (ABG) results: pH=7.49, PCO2= 45 mm Hg, and serum bicarbonate=34 mEq/L. What is the most appropriate PN intervention?

1: Maintain current chloride:acetate ratio
2: Increase chloride:acetate ratio
3: Decrease chloride:acetate ratio
4: Decrease calorie content of PN

Answer 49

2: Increase chloride:acetate ratio

This patient is experiencing a metabolic alkalosis, likely related to large gastric acid losses through his NG tube output, as evidenced by an increase in pH (7.35-7.45), a normal PCO2 (35-45 mm Hg), and an increased serum bicarbonate (22-26 mEq/L). The most appropriate nutrition intervention is to increase the chloride:acetate ratio in the PN solution.

Question 50

A home PN dependent patient with a peripherally inserted central catheter (PICC) presents with arm, shoulder and neck swelling. Which of the following is the most likely cause?

1: Pinch off syndrome
2: Catheter related central venous thrombosis
3: Fibrin sheath occlusion
4: Parenteral nutrition associated infection

Answer 50

2: Catheter related central venous thrombosis

Arm, shoulder, or neck swelling, limb, jaw, or ear pain, and dilated collateral veins over the arm, neck or chest are hallmark symptoms of catheter related central venous thrombosis. Central venous catheters cause endothelial trauma and inflammation which can lead to venous thrombosis. Inflammation of the vessel wall can cause pain and tenderness along the course of the vein. Obstruction of blood flow may cause collateral vein congestion and edema on the affected side.

Question 51

A 75-year-old female with moderate malnutrition is status-post radical cystectomy with ileal conduit. She is initiated on a peripheral parenteral nutrition (PPN) solution at 125mL/h. This formula contains 210 grams of dextrose, 75 grams of amino acids, and 45 grams of fat. In the patient case above, what is the osmolarity of the daily PPN formula?

1: 600mOsm/L
2: 1200 mOsm/L
3: 1800 mOsm/L
4: 2400 mOsm/L

Answer 51

1: 600mOsm/L

PPN formulations are hyperosmolar solutions that can possibly cause pheblitis or extravasation. Therefore, these solutions are usually limited to an osmolarity of 600-900 mOsm/L. Fat can be used to increase caloric density of the formulation without increasing the osmolarity. The following formula can be used to estimate the osmolarity of a PPN. Amino acid 1g = 10 mOsm Dextrose 1g = 5 mOsm In our case: Amino acid 75g = 750 mOsm Dextrose 210g = 1050 mOsm 750 mOsm + 1050 mOsm = 1800 mOsm/3000mL = 600 mOsm/L