1. Parenteral Nutrition Formula Calculations and Monitoring Protocols

2. Macronutrient Concentrations in PN Solutions
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

3. Protein Content Calculations
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

4. Calculation of Dextrose Calories
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.

5. Sample Dextrose Calculation
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

6. Calculation of Lipid Content
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:

7. Example Lipid Calculation for 2-in-1
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:

8. Calculation of Dextrose/AA with Piggyback Lipids (2-in-1)
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:

9. Determine protein concentration
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:

10. Determine dextrose concentration.
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:

11. Example Calculation Nutrient Needs:
Kcals: Protein: 88 g. Fluid: 2000 cc
  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)
Remaining fluid needs: 2000cc - 480cc = 1520cc

12. Protein Calculations
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 – ( ) = 920 kcal

13. Dextrose Concentration
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% 63 cc/hr with 10% lipids 20 cc/hr

14. Re-check calculations
TPN recommendation: Suggest two-in-one PN 17.7% dextrose, 5.8% 63 cc/hr with 10% lipids 20 cc/hr
63 cc/hr x 24 = 1512 ml
1512 * (.177) = 268 g D X 3.4 kcals= kcals
1512 * (.058) = 88 g a.a. x 4 kcals =
20 cc/hr lipids*24 = 480*1.1 kcals/cc = 528
1791

15. 3 in 1 TNA Solutions |
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.

16. 3-in-1 TNA Solutions
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 and kcals 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

17. Sample Calculation 3-in-1
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

18. Sample Calculation 3-in-1(cont)
Dextrose: 908 kcal (1800 – )
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

19. Evaluation of a TNA Order
PN 15% dextrose, 4.5% a.a., 3% 100 cc/hour

20. Evaluation of a PN Order
PN 15% dextrose, 4.5% a.a., 3% 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

21. Evaluation of a PN Order
Amino acids: 4.5 grams/100 ml * 2400 ml = 108 grams protein
108 x 4 = 432 kcals
= 2376 total kcals
Lipid is 30% of total calories
Dextrose is 51.5% of total calories
Protein is 18% of total calories

22. Calculation of Nonprotein 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

23. Calculation of Non-Protein Calories
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) 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

24. Calculation of NPC:N Ratio |
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:

25. Example NPC:N Calculation
80 grams protein 2250 nonprotein kcalories per day
80g protein/ 6.25 = /12.8 = 176 NPC:N = 176:1
Source:

26. Example %NPC Fat Calculation*
2250 nonprotein kcal 550 lipid kcal
550/2250 x 100 = 24% fat kcals
*Limit is 60% NPC

27. Osmolarity in PPN
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.

28. IV-Related Phlebitis

29. Calculating the Osmolarity of a Parenteral Nutrition Solution
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 = = 1020 mOsm/L
Source: K&M and PN Nutrition in ADA, Nutrition in Clinical Practice. P 626

30. Osmolarity Quick Calculation
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:

31. Is the solution compoundable?
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

32. Is the Solution Compoundable?
What is the minimum volume to compound the PN prescription?
Example: g AA
350 g dextrose
50 g lipid
2000 ml fluid restriction
AA: 10 g = 75 g = 750 ml using 10% AA
100 ml X ml
OR divide 75 grams by the % base solution, 75 g/ .10

33. Is the solution compoundable?
Dextrose: 70 g = 350 g x = 500 ml
100 ml X ml
Lipid: g = 50g X = 250 ml
100 ml x ml
Total volume = 750 ml AA ml D ml lipid ml (for electrolytes/trace) = 1600 ml (minimum volume to compound solution)
Tip: Substrates should easily fit in 1 kcal/ml solutions

34. Is this solution compoundable?
PN prescription:
AA 125 g
D g
Lipid 50 g
Fluid restriction 1800 ml/day

35. Is this solution compoundable?
AA: g = g = 1250 ml 10% AA
100 ml X ml
Dextrose: 70 g = 350 g x = 500 ml (350/.70)
100 ml X ml
Lipid: g = 50g X = 250 ml (50/.20)
100 ml x ml
Total volume = 1250 ml AA ml D ml lipid 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%)

36. Parenteral Nutrition
Monitoring

37. Monitoring for Complications
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

38. Monitoring for Complications
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

39. Acute Inpatient PN Monitoring
Parameter
Daily
Frequency
3x/week
Weekly
Glucose
Initially √
Electrolytes
Phos, Mg, BUN, Cr, Ca TG
Fluid/Is & Os
Temperature
T. Bili, LFTs
Adapted from K&M, p. 549

40. Inpatient Monitoring PN
Parameter
Daily
Frequency
Weekly
PRN
Body Weight
Initially √
Nitrogen Balance
HGB, HCT
Catheter Site
Lymphocyte Count
Clinical Status

41. Monitor—cont’d
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 applicable Urinary output (daily) Activity, temperature, respiration (daily) WBC and differential (as needed) Cultures (as needed)

42. Monitoring: Nutrition
Serum Hepatic Proteins
Parameter t ½
Albumin days
Transferrin days
Prealbumin – 3 days
Retinol Binding Protein ~12 hours

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

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

45. Refeeding Syndrome Symptoms
Reduced serum levels of magnesium, potassium, and phosphorus
Hyperglycemia and hyperinsulinemia
Interstitial fluid retention
Cardiac decompensation and arrest

46. Refeeding Syndrome Prevention/Treatment
Monitor and supplement electrolytes, vitamins and minerals prior to and during infusion of PN until levels remain stable
Initiate feedings with kcal/kg or 1000 kcals/day and 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 In Sharpening your skills as a nutrition support dietitian. DNS, 2003.

47. Glycemic Control in Critical Care
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

48. Glycemic Control in PN
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

49. Glycemic Control in PN 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.

50. Glycemic Control in PN 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.

51. Regular Insulin in PN Availability in TPN : 53 – 100% Short half-life
Delivery coincides with nutrient infusion

52. Fluid Excess
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

53. Fluid Deficit
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

54. Electrolytes
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

55. Acid-Base Balance
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

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

57. Metabolic Acidosis Treatment
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

58. Metabolic Alkalosis Etiology
loss of H+ ion from increased gastric losses
Excessive base administration
Contraction alkalosis

59. Metabolic Alkalosis Treatment
Determine and treat underlying cause
Increase Cl- when alkalosis is due to diuretics or NG losses

60. Transitional Feeding
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

61. Cessation of TPN 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

62. Defense Against PN Complications
Select appropriate patients to receive PN
Aseptic technique for insertion and site care of IV catheters
Do not overfeed
Maintain glycemic control < 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