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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 solutionProtein 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 gCalculation 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 kcalCalculation 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 x 1.1 kcal/ml = 550 kcal
500 ml 20% lipid500 ml x 2.0 kcal/ml = 1000 kcal
Or, alternatively, 500 ml of 10% lipid = 50 grams lipid x 10 kcal/g or 500 kcalSource: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html
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.
Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html
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 proteinSource: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html
Determine dextrose concentration.
Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html
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 = 1520ccProtein 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 kcalDextrose 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/hrTPN 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 100Sample Calculation 3-in-1
Nutrient Needs:Kcals: 1800 Protein: 88 g Fluid: 2000 cc
Lipid : 1800 kcal x 30% = 540 kcal540 kcal / 10 kcal per gram = 54 g
54 g / 2000 cc x 100 = 2.7% lipid
Protein: 88 g / 2000 cc x 100 =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/hourEvaluation 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 kcalsEvaluation 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 caloriesCalculation 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 patientsCalculation 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 kcalsCalculation 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: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html
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
Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html
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.)Source: http://www.csun.edu/~cjh78264/parenteral/calculation/calc07.html
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 restrictionIs 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, LFTsInitiallyInpatient Monitoring PN
ParameterDailyFrequencyWeeklyPRNBody WeightInitiallyNitrogen BalanceInitiallyHGB, HCTCatheter SiteLymphocyte CountClinical StatusMonitorcontd
Urine: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 sepsisRefeeding Syndrome
Patients at risk are malnourished, particularly marasmic patientsCan occur with enteral or parenteral nutritionResults from intracellular electrolyte shiftRefeeding Syndrome Symptoms
Reduced serum levels of magnesium, potassium, and phosphorusHyperglycemia and hyperinsulinemiaInterstitial fluid retentionCardiac decompensation and arrestRefeeding 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, BGGlycemic Control in PN
In critically ill patients, recommendation is to keep dextrose infusionGlycemic Control in PN
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 levelsCharney P. A Spoonful of Sugar: Glycemic Control in the ICU. In Sharpening your skills as a nutrition support dietitian. DNS, 2003.
Glycemic Control in PN
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 infusionFluid 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 litersFluid 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 gravityElectrolytes
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 hyperglycemiaAcid-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 acidsMetabolic Acidosis Etiology
Increased renal or GI loss of bicarbonateAddition of strong acid or underexcretion of H+ ionKetoacidosisRenal failureLactic acidosisExcessive Cl- administrationMetabolic Acidosis Treatment
Determine and treat underlying causeProve acetate forms of electrolytes with HCO3- lossesDecrease chloride concentration in TNAConsider chloride concentration in other IV fluidsMetabolic Alkalosis Etiology
loss of H+ ion from increased gastric lossesExcessive base administration Contraction alkalosisMetabolic Alkalosis Treatment
Determine and treat underlying causeIncrease Cl- when alkalosis is due to diuretics or NG lossesTransitional 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 levelsCessation 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 hypoglycemiaDefense Against PN Complications
Select appropriate patients to receive PNAseptic technique for insertion and site care of IV cathetersDo not overfeedMaintain glycemic control