How to Write TPN

1. Start by determining energy needs2. Determine calories from protein 3. Determine calories from fat4. Make up the remainder of energy needs from carbohydrates5. Calculate the amount of fluid the patient needs6. Add electrolytes, vitamins, trace elements

CALCULATING TPN

1. START BY DETERMINING ENERGY NEEDSUse Kcal/Kg based on the following scale:

• Normal need: 25-30 Kcal/kg/day• Elective surgery: 28-30 kcal/kg/day• Severe injury: 30-40 kcal/kg/day• Extensive trauma/burn: 45-55 kcal/kg/day

Example:

70 Kg male with elective surgery X 30 Kcal/Kg = 2,100 Kcal/day

• May use Harris-Benedict + activity + infection/fever factor + etc = Energy (Kcal)

2. DETERMINE CALORIES FROM PROTEIN

• Usually start with 0.83 gm/Kg and add stress and other factors as needed

• May need up to 2.5 g/Kg due to loss and other factors

For example:Malnourished 70 Kg man X 1.2 gm/kg/day = 84 gm protein per day

Calories from protein:

84 gm protein * 4 Kcal/gm protein = 336 Kcal

3. DETERMINE CALORIES FROM FAT

At LVH 0.6 gm fat/kg/day is used:

Example:0.6 gm fat/kg/day * 70 kg = 42 gm fat/day

Calories from fat:

42 gm fat * 9 Kcal/gm fat = 378 Kcal

4. MAKE UP THE REST OF CALORIES FROM CARBOHYDRATES

Energy needed in 1 day for a 70 kg pt. = 2100 Kcal/day

2100 Kcal/day – 336 Kcal from protein – 378 Kcal from fat = 1386 Kcal

Dextrose = 3.4 Kcal/gram; available in 50 to 70% solution (D50W, D70W)

To calculate the amount of Dextrose needed in grams:

1386 Kcal * (1 gm Dextrose/3.4 Kcal) = 408 gm Dextrose

5. NEXT CALCULATE THE AMOUNT OF FLUIDS THE PATIENT NEEDS:

100 cc/Kg for first 10 Kg + 50 cc/Kg for the second 10 Kg + 20 cc/Kg for each additional Kg:Example for 70 kg pt.:

100 cc/Kg X 10 Kg = 1000 cc 50 cc/Kg X 10 Kg = 500 cc20 cc/Kg X 50 Kg = 1000 cc

total: 1000 + 500 + 1500 = 2,500 cc/day

Determine how much volume will be taken up by protein in the TPN solution:85 gm of protein using a 10% amino acid solution; 10% solution = 10 gm protein/100 cc Example:

85 gm / X mL = 10 gm/100 mLX mL * 10 gm = 8500 gm mlX = 8500 gm ml/10 gm = 850 ml 10% protein solution

Determine how much volume will be taken up by fat: 42 gm of fat using a 15% amino acid solution; 15% solution = 15 gm fat/100 ccExample:

42 gm / X mL = 15 mg/100 mLX mL * 15 gm = 4200 gm mLX = 4200 gm mL/15 gm = 280 mL 15% fat solution

Determine how much volume will be taken up by carbohydrates:408 mg Dextrose using a D50W solution; 50% solution = 50 gm Dextrose/100 ccExample:

408 gm / X mL = 50 gm/100 mLX mL * 50 gm = 40800 gm mLX = 40800 gm mL/50 gm = 816 mL D50W

Total cc/day for 70 kg pt. = 2500 cc/day

850 cc 10% protein solution + 280 cc 15% protein solution + 816 cc D50W = 1946 cc TPN

2500 cc/day – 1946 cc TPN = 554 cc

Need to add 554 cc of fluid for electrolytes, vitamins, and trace elements (or drips that pt. is already on)

Calculate rate/hr:

2500 ml/24 hr = 105 ml/hr

6. ADD ELECTROLYTES, VITAMINS, AND TRACE ELEMENTS (ASPEN GUIDELINES)

Electrolytes

Sodium: 1–2 mEq/kgPotassium: 1–2 mEq/kg Phosphorus: 20–40 mmol Magnesium: 8–20 mEq Calcium: 10-15 mEqChloride and Acetate: adjusted by acid-base balance

Trace Elements

Zinc: 2.5 – 5.0 mgCopper: 0.3 – 0.5 mgChromium: 10 – 15 mcgManganese: 60 – 100 mcgSelenium: 20 – 60 mcg

Vitamins

Vitamin A: 3300 IUVitamin D: 200 IUVitamin E: 10 IUVitamin K: 150 mcgThiamine (B1): 6 mgPyridoxine (B6): 6 mgCyanocobalamin (B12): 5 mcgPantothenic acid: 15 mgBiotin: 60 mcgVitamin C: 200 mgFolic Acid: 600 mcgNiacin: 40 mgRiboflavin (B2): 3.6mg