AB is a 65-year-old female inpatient in the hospital you are working at. She has been placed on TPN by her physician due to a high-output intestinal fistula. She is stable and on the main unit of the hospital. She has central IV access. 

Labs:

Na 135mEq/L  Cl 105mEq/L  K 5.7mEq/L  Triglycerides 105mg/dL  Blood glucose 80mg/dL

Actual body weight: 60kg

Ideal body weight: 62kg

Allergies: fish (shortness of breath), penicillin (hives)

When verifying the order for AB’s TPN, which of the following components would be reasonable addition(s) based on her provided information, assuming 24-hour requirements? Select all that apply. 

A. 1-1.5g/kg/day amino acids 

B. 1g/kg/day SMOFlipid

C. 1.5mEq/kg/day potassium acetate

D. 1.5mEq/kg/day sodium chloride

E.  2-3 mg/kg/min glucose infusion rate initially with goal of 4-5mg/kg/min

Answers with Rationale: 

TPN or total parenteral nutrition is a critical intervention for patients not able to tolerate oral or enteral feeds. It ensures they remain adequately nourished during their time of illness. Some indications for TPN include short bowel syndrome, fistulas, intestinal obstruction, and intractable vomiting. TPN is made up of macronutrients (amino acids, lipids, and dextrose), micronutrients (sodium, chloride, potassium, calcium, magnesium, phosphorous, and acetate), trace elements (selenium, copper, manganese, and zinc), and multivitamins (B, C, A, D, E, and K). It is important to think about daily caloric requirements, fluid requirements, lab values, allergies, disease states, and organ function when dosing and adjusting TPNs. TPNs can be compounded doing 2 in 1 (dextrose plus amino acids) or 3 in 1, also known as total nutrient admixtures (TNA), which contains dextrose, amino acids, and fats. Total calories within a TPN should be approximately 25-35 kcal/kg/day, with the highest kcal/kg/day reserved for the most critically ill patients. 

Answer A is correct. Amino acids are an important component of TPN. They provide the patient with adequate protein levels. 0.8-1.5g/kg/day is an appropriate dose of amino acids in stable adults. Higher or lower doses may be required based on kidney function, BUN, and states of stress.

Answer B is incorrect. SMOFlipid is a variation of lipid used in both adult and pediatric patients. It can be useful in patients with cholestasis secondary to TPN as it contains omega-3 fatty acids which are good for the liver. In this patient, it would not be appropriate due to their fish allergy. SMOFlipid, as the abbreviation implies, is made up of soybean oil, MCT oil, olive oil, and fish oil. An alternative for this patient would be Intralipid, made of purely soybean oil. Another important thing to monitor for lipids is the triglycerides, as levels above 1000mg/dL is a contraindication to all lipids.

Answer C is incorrect. Potassium is generally an important electrolyte to add to TPNs, and this dose would be appropriate in the average adult. However, this patient has an elevated level of potassium (6mEq/L), so they would not need potassium added to their TPN until their levels declined.

Answer D is correct. Sodium chloride is an appropriate addition to this TPN, as the typical daily dose for an average stable adult patient is 1-2mEq/kg/day. This patient’s sodium and chloride levels are both within normal range as well, making this an appropriate addition.

Answer E is correct. Dextrose is another important macronutrient for TPN, as it provides daily carbohydrates. It is provided at a rate of around 4-7mg/kg/min (usually 4-5 mg/kg/min) in stable adults and 4mg/kg/min or less in critical ICU patients. You can initiate at 2-3 mg/kg/min glucose infusion rate and then progress toward goal. This patients BG level is also normal, making this an appropriate addition to her TPN. Alternatively dextrose can be calculated to be about 40-60% of total calories and place this amount within the TNA. 

NAPLEX Competencies Covered:

Area 1: Obtain, Interpret, or Assess Data, Medical, or Patient Information

1. From instruments, screening tools, laboratory, genomic or genetic information, or diagnostic findings

Area 2: Identify Drug Characteristics 

2.1 Pharmacology, mechanism of action, or therapeutic class

Area 3: Develop or Manage Treatment Plans 

3.3 Medication reconciliation; indication or therapeutic uses; lack of indication; inappropriate indication; duplication of therapy; omissions

3.4 Drug dosing or dosing adjustments; duration of therapy

3.6 Drug contraindications, allergies, or precaution

3.9 Therapeutic monitoring parameters, monitoring techniques, monitoring tools, or monitoring frequency

References:

Lipid package insert – SMOFlipid