parenteral nutrition calculations.ppt

Parenteral Nutrition Formula Calculations and Monitoring Protocols

Macronutrient Concentrations in PN Solutions
Macronutrient concentrations (%) = the grams of solute/100 ml of fluidD70 has 70 grams of dextrose per 100 ml. 10% amino acid solution has 10 grams amino acids/100 ml of solution20% lipids has 20 grams of lipid/100 ml of solution

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

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.

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

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

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

Calculation of Dextrose/AAwith 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.


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

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.

Example Calculation

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)
Remaining fluid needs: 2000cc - 480cc = 1520cc

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 (528 + 352) = 920 kcal

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% a.a. @ 63 cc/hr with 10% lipids piggyback @ 20 cc/hr

Re-check calculations

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

3 in 1 TNASolutions |
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.

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 proteinDetermine 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

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 acids88 g x 4 = 352 kcals from protein

Sample Calculation 3-in-1(cont)

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

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

Evaluation of a PN Order

PN 15% dextrose, 4.5% a.a., 3% lipid @ 100 cc/hour
Total volume = 2400Dextrose: 15g/100 ml * 2400 ml = 360 g360 g x 3.4 kcal/gram = 1224 kcalsLipids 3 g/100 ml x 2400 ml = 72 g lipids72 x 10 kcals/gram = 720 kcals

Evaluation of a PN Order
Amino acids: 4.5 grams/100 ml * 2400 ml = 108 grams protein108 x 4 = 432 kcals1224 + 720 + 432 = 2376 total kcalsLipid is 30% of total caloriesDextrose is 51.5% of total caloriesProtein is 18% of total calories

Calculation of Nonprotein Calories
Some clinicians discriminate between protein and nonprotein calories although this is falling out of favorThis is more commonly used in critically ill patients

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

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


Example NPC:N Calculation

80 grams protein
2250 nonprotein kcalories per day

80g protein/ 6.25 = 12.8
2250/12.8 = 176
NPC:N = 176:1


Example %NPC Fat Calculation*

2250 nonprotein kcal
550 lipid kcal

550/2250 x 100 = 24% fat kcals

*Limit is 60% NPC

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.

IV-Related Phlebitis

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 = 500 + 300 + 60 + 160 = 1020 mOsm/L

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

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.)

Is the solution compoundable?
TPN is compounded using 10% or 15% amino acids, 70% dextrose, and 20% lipidsThe TPN prescription must be compoundable using standard base solutionsThis becomes an issue if the patient is on a fluid restriction

Is the Solution Compoundable?

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 ml X ml

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

Is the solution compoundable?

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

Is this solution compoundable?

PN prescription:

AA 125 g

D 350 g

Lipid 50 g

Fluid restriction 1800 ml/day

Is this solution compoundable?

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

100 ml X 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

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

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

Acute Inpatient PN Monitoring

Adapted from K&M, p. 549
ParameterDailyFrequency3x/weekWeeklyGlucoseInitiallyElectrolytesInitiallyPhos, Mg, BUN, Cr, CaInitiallyTG Fluid/Is & OsTemperatureT. Bili, LFTsInitially

Inpatient Monitoring PN
ParameterDailyFrequencyWeeklyPRNBody WeightInitiallyNitrogen BalanceInitiallyHGB, HCTCatheter SiteLymphocyte CountClinical Status

Monitorcontd
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)

Monitoring: Nutrition

Serum Hepatic Proteins

Parameter t

Albumin 19 days

Transferrin9 days

Prealbumin2 3 days

Retinol Binding Protein~12 hours

Complications of PN
Refeeding syndromeHyperglycemiaAcid-base disordersHypertriglyceridemiaHepatobiliary complications (fatty liver, cholestasis)Metabolic bone diseaseVascular access sepsis

Refeeding Syndrome
Patients at risk are malnourished, particularly marasmic patientsCan occur with enteral or parenteral nutritionResults from intracellular electrolyte shift

Refeeding Syndrome Symptoms
Reduced serum levels of magnesium, potassium, and phosphorusHyperglycemia and hyperinsulinemiaInterstitial fluid retentionCardiac decompensation and arrest

Refeeding Syndrome Prevention/Treatment
Monitor and supplement electrolytes, vitamins and minerals prior to and during infusion of PN until levels remain stableInitiate feedings with 15-20 kcal/kg or 1000 kcals/day and 1.2-1.5 g protein/kg/dayLimit 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.

Glycemic Control in Critical Care
Until recently, BG

Glycemic Control in PN
In critically ill patients, recommendation is to keep dextrose infusion


For Patients Not Previously on Insulin
Monitor blood glucose levels prior to initiating PNWhen therapy is initiated, monitor BG q 4-6 hours and use sliding scale or insulin drip as needed Add a portion of the previous days 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 illnessDetermine amount of feedings to be givenProvide 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.

Regular Insulin in PN
Availability in TPN : 53 100%Short half-lifeDelivery coincides with nutrient infusion

Fluid Excess
Critically ill pts and those with cardiac, renal, hepatic failure may require fluid restrictionMay need to restrict total calories to reduce total volumeUse 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

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

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

Acid-Base Balance
Balance chloride and acetate to maintain/achieve equilibriumThe standard acetate/chloride ratio is 1:1Increase proportion of chloride with metabolic alkalosis; increase proportion of acetate with metabolic acidosisConsider chloride and acetate content of amino acids

Metabolic Acidosis Etiology
Increased renal or GI loss of bicarbonateAddition of strong acid or underexcretion of H+ ionKetoacidosisRenal failureLactic acidosisExcessive Cl- administration

Metabolic Acidosis Treatment
Determine and treat underlying causeProve acetate forms of electrolytes with HCO3- lossesDecrease chloride concentration in TNAConsider chloride concentration in other IV fluids

Metabolic Alkalosis Etiology
loss of H+ ion from increased gastric lossesExcessive base administration Contraction alkalosis

Metabolic Alkalosis Treatment
Determine and treat underlying causeIncrease Cl- when alkalosis is due to diuretics or NG losses

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

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

Defense Against PN Complications
Select appropriate patients to receive PNAseptic technique for insertion and site care of IV cathetersDo not overfeed
Maintain glycemic control

parenteral nutrition calculations.ppt

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