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Parenteral Nutrition Formula Calculations and Monitoring Protocols

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- Macronutrient concentrations (%) = the grams of solute/100 ml of fluid
- D70 has 70 grams of dextrose per 100 ml.
- 10% amino acid solution has 10 grams amino acids/100 ml of solution
- 20% lipids has 20 grams of lipid/100 ml of solution

To calculate the grams of protein supplied by a TPN solution, multiply the total volume of amino acid solution (in ml*) supplied in a day by the amino acid concentration.

Example Protein Calculation

1000 ml of 8% amino acids:

1000 ml x 8 g/100 ml = 80g

Or 1000 x .08 = 80 g

- Calculate grams of dextrose:
- Multiply the total volume of dextrose soln (in ml) supplied in a day by the dextrose concentration. This gives you grams of dextrose supplied in a day.

- Multiply the grams of dextrose by 3.4 (there are 3.4 kcal/g dextrose) to determine kcalories supplied by dextrose in a day.

- 1000 ml of D50W (50% dextrose)
- 1000 ml x 50g / 100 ml = 500g dextrose
- OR 1000 ml x .50 = 500g dextrose

- 500g dextrose x 3.4 kcal/g = 1700 kcal

- To determine kcalories supplied by lipid*, multiply the volume of 10% lipid (in ml) by 1.1; multiply the volume of 20% lipid (in ml) by 2.0.
- If lipids are not given daily, divide total kcalories supplied by fat in one week by 7 to get an estimate of the average fat kcalories per day.
*|Lipid emulsions contain glycerol, so lipid emulsion does not have 9 kcal per gram as it would if it were pure fat. Some use 10 kcal/gm for lipid emulsions.

Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html

- 500 ml of 10% lipid
- 500 ml x 1.1 kcal/ml = 550 kcal

- 500 ml 20% lipid
- 500 ml x 2.0 kcal/ml = 1000 kcal

- Or, alternatively, 500 ml of 10% lipid = 50 grams lipid x 10 kcal/g or 500 kcal

Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html

- Determine patient's kcalorie, protein, and fluid needs.
- Determine lipid volume and rate for "piggy back" administration.
- Determine kcals to be supplied from lipid. (Usually 30% of total kcals).
- Divide lipid kcals by 1.1 kcal/cc if you are using 10% lipids; divide lipid kcals by 2 kcal/cc if you are using 20% lipids. This is the total volume.
- Divide total volume of lipid by 24 hr to determine rate in cc/hr.

Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html

- Subtract volume of lipid from total fluid requirement to determine remaining fluid needs.
- Divide protein requirement (in grams) by remaining fluid requirement and multiply by 100. This gives you the amino acid concentration in %.
- Multiply protein requirement in grams x 4 to determine calories from protein

Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html

- Subtract kcals of lipid + calories from protein from total kcals to determine remaining kcal needs.
- Divide "remaining kcals" by 3.4 kcal/g to determine grams of dextrose.
- Divide dextrose grams by remaining fluid needs (in protein calculations) and multiply by 100 to determine dextrose concentration.
- Determine rate of AA/dex solution by dividing "remaining fluid needs” by 24 hr.

Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html

Nutrient Needs:

Kcals: 1800. Protein: 88 g. Fluid: 2000 cc

1800 kcal x 30% = 540 kcal from lipid

Lipid (10%):

- 540 kcal/1.1 (kcal/cc) = 491 cc/24 hr =
20 cc/hr 10% lipid (round to 480 ml)

Protein: 88 g / 1520 cc x 100 =5.8% amino acid solution

88 g. x 4 kcal/gm =352 kcals from protein

- Remaining kcal needs: 1800 – (528 + 352) = 920 kcal

- 920 kcal/3.4 kcal/g = 270 g dextrose
- 270 g / 1520 cc x 100 = 17.7% dextrose solution
- Rate of Amino Acid / Dextrose: 1520 cc / 24hr = 63 cc/hr
TPN recommendation: Suggest two-in-one PN 17.7% dextrose, 5.8% a.a. @ 63 cc/hr with 10% lipids piggyback @ 20 cc/hr

TPN recommendation: Suggest two-in-one PN 17.7% dextrose, 5.8% a.a. @ 63 cc/hr with 10% lipids piggyback @ 20 cc/hr

63 cc/hr x 24 = 1512 ml

1512 * (.177) = 268 g D X 3.4 kcals= 911 kcals

1512 * (.058) = 88 g a.a. x 4 kcals = 352

20 cc/hr lipids*24 = 480*1.1 kcals/cc = 528

1791

- Determine patient's kcalorie, protein, and fluid needs.
- Divide daily fluid need by 24 to determine rate of administration.
- Determine lipid concentration.
- Determine kcals to be supplied from lipid. (Usually 30% of total kcals).
- Determine grams of lipid by dividing kcal lipid by 10. *
- Divide lipid grams by total daily volume (= fluid needs or final rate x 24) and multiply by 100 to determine % lipid.

- Determine protein concentration by dividing protein needs (grams) by total daily volume and multiply by 100.
- Multiply protein needs in grams x 4 kcal/gm = kcals from protein
- Determine dextrose grams.
- Subtract kcals of lipid andkcals from protein from total kcals to determine remaining kcal needs.
- Divide "remaining kcals" by 3.4 kcal/g to determine grams of dextrose.
- Determine dextrose concentration by dividing dextrose grams by total daily volume and multiply by 100

- Nutrient Needs:
- Kcals: 1800 Protein: 88 g Fluid: 2000 cc

- Lipid : 1800 kcal x 30% = 540 kcal
- 540 kcal / 10 kcal per gram = 54 g
- 54 g / 2000 cc x 100 = 2.7% lipid

- Protein: 88 g / 2000 cc x 100 =4.4% amino acids
- 88 g x 4 = 352 kcals from protein

Dextrose: 908 kcal (1800 – 540 - 352)

- 908/3.4 kcal/g = 267 g dextrose
- 267 g / 2000 cc x 100 =13.4% dextrose solution
- Rate of Amino Acid / Dextrose/Lipid: 2000 cc / 24hr = 83 cc/hr
- TPN prescription: Suggest TNA 13.4% dextrose, 4.4% amino acids, 2.7% lipids at 83 cc/hour provides 88 g. protein, 1800 kcals, 2000 ml. fluid

- PN 15% dextrose, 4.5% a.a., 3% lipid @ 100 cc/hour

PN 15% dextrose, 4.5% a.a., 3% lipid @ 100 cc/hour

- Total volume = 2400
- Dextrose: 15g/100 ml * 2400 ml = 360 g
- 360 g x 3.4 kcal/gram = 1224 kcals
- Lipids 3 g/100 ml x 2400 ml = 72 g lipids
- 72 x 10 kcals/gram = 720 kcals

- Amino acids: 4.5 grams/100 ml * 2400 ml = 108 grams protein
- 108 x 4 = 432 kcals
- 1224 + 720 + 432 = 2376 total kcals
- Lipid is 30% of total calories
- Dextrose is 51.5% of total calories
- Protein is 18% of total calories

- Some clinicians discriminate between protein and nonprotein calories although this is falling out of favor
- This is more commonly used in critically ill patients

- To determine the nonprotein kcalories (NPC) in a TPN prescription, add the dextrose calories to the lipid calories
- In the last example, 1224 kcals (dextrose) + 720 kcals (lipid) = 1944 non-protein kcals
- Dextrose is 63% of nonprotein kcals (1224/1944)
- Lipid is 37% of nonprotein calories
- In critically ill patients, some clinicians restrict lipid to 30% of nonprotein kcals

- Calculate grams of nitrogen supplied per day (1 g N = 6.25g protein)
- Divide total nonprotein calories by grams of nitrogen
- Desirable NPC:N Ratios:
- 80:1 the most severely stressed patients
- 100:1 severely stressed patients
- 150:1 unstressed patient

Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html

80 grams protein2250 nonprotein kcalories per day

80g protein/ 6.25 = 12.82250/12.8 = 176NPC:N = 176:1

Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html

2250 nonprotein kcal550 lipid kcal

550/2250 x 100 = 24% fat kcals

*Limit is 60% NPC

- When a hypertonic solution is introduced into a small vein with a low blood flow, fluid from the surrounding tissue moves into the vein due to osmosis. The area can become inflamed, and thrombosis can occur.

- Multiply the grams of dextrose per liter by 5. Example: 100 g of dextrose x 5 = 500 mOsm/L
- Multiply the grams of protein per liter by 10. Example: 30 g of protein x 10 = 300 mOsm/L
- Multiply the grams of lipid per liter by 1.5.
Example: 40 g lipid x 1.5 = 60.

- Multiply the (mEq per L sodium + potassium + calcium + magnesium) X 2
Example: 80 X 2 = 160

- Total osmolarity = 500 + 300 + 60 + 160 = 1020 mOsm/L

Source: K&M and PN Nutrition in ADA, Nutrition in Clinical Practice. P 626

To calculate solution osmolarity:

- multiply grams of dextrose per liter by 5
- multiply grams of protein per liter by 10
- add a & b
- add 300 to 400 to the answer from "c". (Vitamins and minerals contribute about 300 to 400 mOsm/L.)

Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html

- TPN is compounded using 10% or 15% amino acids, 70% dextrose, and 20% lipids
- The TPN prescription must be compoundable using standard base solutions
- This becomes an issue if the patient is on a fluid restriction

What is the minimum volume to compound the PN prescription?

Example: 75 g AA

350 g dextrose

50 g lipid

2000 ml fluid restriction

AA: 10 g = 75 g = 750 ml using 10% AA

100 mlX ml

OR divide 75 grams by the % base solution, 75 g/ .10

Dextrose: 70 g = 350 g x = 500 ml

100 ml X ml

Lipid: 20 g = 50g X = 250 ml

100 ml x ml

Total volume = 750 ml AA + 500 ml D + 250 ml lipid + 100 ml (for electrolytes/trace) = 1600 ml (minimum volume to compound solution)

Tip: Substrates should easily fit in 1 kcal/ml solutions

PN prescription:

AA 125 g

D 350 g

Lipid 50 g

Fluid restriction 1800 ml/day

AA: 10 g = 125 g = 1250 ml 10% AA

100 mlX ml

Dextrose: 70 g = 350 g x = 500 ml (350/.70)

100 ml X ml

Lipid: 20 g = 50g X = 250 ml (50/.20)

100 ml x ml

Total volume = 1250 ml AA + 500 ml D + 250 ml lipid + 100 ml (for electrolytes/trace) = 2100 ml (minimum volume to compound solution)

Verdict: not compoundable in 1800 ml.

Action: reduce dextrose content or use 15% AA base solution if available (could deliver protein in 833 ml of 15%)

Parenteral Nutrition

Monitoring

- Malnourished patients at risk for refeeding syndrome should have serum phosphorus, magnesium, potassium, and glucose levels monitored closely at initiation of SNS. (B)
- In patients with diabetes or risk factors for glucose intolerance, SNS should be initiated with a low dextrose infusion rate and blood and urine glucose monitored closely. (C)
- Blood glucose should be monitored frequently upon initiation of SNS, upon any change in insulin dose, and until measurements are stable. (B)

ASPEN BOD. Guidelines for the use of enteral and parenteral nutrition in adult and pediatric patients. JPEN 26;41SA, 2002

- Serum electrolytes (sodium, potassium, chloride, and bicarbonate) should be monitored frequently upon initiation of SNS until measurements are stable. (B)
- Patients receiving intravenous fat emulsions should have serum triglyceride levels monitored until stable and when changes are made in the amount of fat administered. (C)
- Liver function tests should be monitored periodically in patients receiving PN. (A)

ASPEN BOD. Guidelines for the use of enteral and parenteral nutrition in adult and pediatric patients. JPEN 26;41SA, 2002

Adapted from K&M, p. 549

- Urine:Glucose and ketones (4-6/day)Specific gravity or osmolarity (2-4/day)Urinary urea nitrogen (weekly)
- Other:Volume infusate (daily)Oral intake (daily) if applicableUrinary output (daily)Activity, temperature, respiration (daily)WBC and differential (as needed)Cultures (as needed)

Serum Hepatic Proteins

Parameter t ½

Albumin 19 days

Transferrin9 days

Prealbumin2 – 3 days

Retinol Binding Protein~12 hours

- Refeeding syndrome
- Hyperglycemia
- Acid-base disorders
- Hypertriglyceridemia
- Hepatobiliary complications (fatty liver, cholestasis)
- Metabolic bone disease
- Vascular access sepsis

- Patients at risk are malnourished, particularly marasmic patients
- Can occur with enteral or parenteral nutrition
- Results from intracellular electrolyte shift

- Reduced serum levels of magnesium, potassium, and phosphorus
- Hyperglycemia and hyperinsulinemia
- Interstitial fluid retention
- Cardiac decompensation and arrest

- Monitor and supplement electrolytes, vitamins and minerals prior to and during infusion of PN until levels remain stable
- Initiate feedings with 15-20 kcal/kg or 1000 kcals/day and 1.2-1.5 g protein/kg/day
- Limit fluid to 800 ml + insensible losses (adjust per patient fluid tolerance and status)

Fuhrman MP. Defensive strategies for avoiding and managing parenteral nutrition complications. P. 102. In Sharpening your skills as a nutrition support dietitian. DNS, 2003.

- Until recently, BG<200 mg/dl was tolerated in critically ill patients.
- Now greater attention is given to glycemic control due to evidence that glucose is associated with morbidity/mortality and risk of infection
- New recommendation is to keep BG<150 mg/dl or as close to normal as possible

Van den Berghe et al. NEJM, 2001

- In critically ill patients, recommendation is to keep dextrose infusion <5 mg/kg/minute or <60% of total kcals.

ASPEN Nutrition Support Practice Manual, 2005, p. 267

For Patients Not Previously on Insulin

- Monitor blood glucose levels prior to initiating PN
- When therapy is initiated, monitor BG q 4-6 hours and use sliding scale or insulin drip as needed
- Add a portion of the previous day’s insulin to TPN to maintain blood glucose levels

Charney P. A Spoonful of Sugar: Glycemic Control in the ICU. In Sharpening your skills as a nutrition support dietitian. DNS, 2003.

For Patients Previously on Insulin

- Determine amount of insulin needed prior to illness
- Determine amount of feedings to be given
- Provide a portion of daily insulin needs in first PN along with sliding scale or insulin drip to maintain glucose levels (generally insulin needs will increase while on PN)

Charney P. A Spoonful of Sugar: Glycemic Control in the ICU. In Sharpening your skills as a nutrition support dietitian. DNS, 2003.

- Availability in TPN : 53 – 100%
- Short half-life
- Deliverycoincides with nutrient infusion

- Critically ill pts and those with cardiac, renal, hepatic failure may require fluid restriction
- May need to restrict total calories to reduce total volume
- Use most concentrated source of PN components (70% dextrose = 2.38 kcal/ml; 20% lipid = 2 kcal/ml)
- PPN may be contraindicated due to fluid volume of 2-4 liters

- Patients with excessive losses may require sterile water added to the PN
- Provide consistently required fluid volume in PN
- Monitor I/O, weight, serum sodium, BUN, HCT, skin turgor, pulse rate, BP, urine specific gravity

- Electrolytes in PN should be given at a stable dose with intermittent requirements for supplementation given outside the PN
- Sodium levels often reflect fluid distribution versus sodium status
- Hypokalemia may be due to excessive GI losses, metabolic alkalosis, and refeeding
- Hyperkalemia may be due to renal failure, metabolic acidosis, potassium administration, or hyperglycemia

- Balance chloride and acetate to maintain/achieve equilibrium
- The standard acetate/chloride ratio is 1:1
- Increase proportion of chloride with metabolic alkalosis; increase proportion of acetate with metabolic acidosis
- Consider chloride and acetate content of amino acids

- Increased renal or GI loss of bicarbonate
- Addition of strong acid or underexcretion of H+ ion
- Ketoacidosis
- Renal failure
- Lactic acidosis
- Excessive Cl- administration

- Determine and treat underlying cause
- Prove acetate forms of electrolytes with HCO3- losses
- Decrease chloride concentration in TNA
- Consider chloride concentration in other IV fluids

- loss of H+ ion from increased gastric losses
- Excessive base administration
- Contraction alkalosis

- Determine and treat underlying cause
- Increase Cl- when alkalosis is due to diuretics or NG losses

- Maintain full PN support until pt is tolerating 1/3 of needs via enteral route
- Decrease TPN by 50% and continue to taper as the enteral feeding is advanced to total
- TPN can reduce appetite if >25% of calorie needs are met via PN
- TPN can be tapered when pt is consuming greater than 500 calories/d and d-c’d when meeting 60% of goal
- TPN can be rapidly d-c’d if pt is receiving enteral feeding in amount great enough to maintain blood glucose levels

- Rebound hypoglycemia is a potential complication
- Decrease the volume by 50% for 1-2 hours before discontinuing the solution to minimize risk
- PPN can be stopped without concern for hypoglycemia

- Select appropriate patients to receive PN
- Aseptic technique for insertion and site care of IV catheters
- Do not overfeed
- Maintain glycemic control <150-170 mg/dl
- Limit lipids to 1 gm/kg and monitor TG levels
- Adjust protein based on metabolic demand and organ function

- Monitor fluid/electrolyte/mineral status
- Provide standard vitamin and trace element preps daily