Parenteral Nutrition Flashcards
What is TPN?
- Nutritional support given IV when enteral not safe/effective (macro+micronutrients)
- Not disease-specific, but provision of calories/energy used to prevent malnutrition
TPN General Problems
Expensive with risk of serious ADEs (appropriate use is essential)
- Must recognize when and when not to use
- Tailor to patient
- Monitor and adjust as needed
- Transition to enteral ASAP
TPN Adult Indications
Healthy adult unable to receive significant EN: Initiate after 7 days
Nutritionally-at-risk patients unlikely to achieve goal: Initiate within 3-5 days
Baseline moderate-severe malnutrition (EN not feasible): Initiate ASAP
Delay in metabolically unstable patients until condition improves
“Nutritionally-at-risk” criteria
One or more:
- Involuntary weight loss: 10% <6mo, 10lbs <6mo, 5% <1mo
- BMI < 18.5 kg/m^2
- Increased metabolic requirements
- Altered diet and/or diet schedule
TPN Pediatric Indications
Limited data (can delay up to 7 days in a self-resolving illness situation)
If unlikely to tolerate EN for extended time:
Infants (1mo-1y): Initiate within 1-3 days
Children/adolescents: Initiate within 4-5 days
Why do we initiate TPN sooner in pediatrics?
They have
- Decreased metabolic stores/reserves available
- Higher energy requirements
TPN Neonate Indications (0-1mo)
Very-low birth weight (<1.5kg): Initiate promptly after birth
Preterm and critically ill term neonates: Initiate when EN unable to meet energy requirements for growth
Concern when holding fat in neonate diet for 3 days?
Essential fatty acid deficiency
(impacts brain development)
TPN Indications Any Age
- Impaired absorption (short bowel, high output intestinal fistula, gastroschisis)
- Mechanical/motility issues (obstruction, ileus, inflammatory disease)
- “Bowel rest” required (pancreatitis, ischemic bowel, pre/post-operative)
- Inability to utilize EN (VLBW infant, hemodynamic instability, severe GI bleeding)
TPN Types of Complications
Metabolic
Mechanical
Infectious
TPN Metabolic Complications
- Hypo/hyperglycemia (target 140-180 mg/dL)
- Electrolyte imbalances, refeeding syndrome (hypoK, hypophos, hypoMg)
- Hypertriglyceridemia
- Liver function abnormalities acute (AST/ALT elevations) and chronic (Alkaline Phos/Bilirubin > weeks)
TPN Mechanical Complications
- Pneumothorax
- Catheter occlusion
- Thrombus
- Phlebitis (extravasation of TPN)
TPN Administration: Peripheral line
- Bedside insertion into veins of forearm/hand
- Use for short-term duration
BUT
- Increased phlebitis risk
- Upper osmolarity limit of 900 mOsm/L
- Not suitable for home TPN or long term
TPN Infectious Complications
- Central line associated infections, bacteremia
TPN Administration: Central line (PICC)
- Bedside insertion into basilic, cephalic, or brachial veins (tip in superior vena cava)
- Suitable for short to medium duration of TPN
BUT
- May require radiologist
- Increased DVT risk
- Site: limits pt activity, easily removed, easily infected
TPN Administration: Tunneled catheter (Broviac, Hickman)
- Suitable for long term TPN, cuffed to minimize contamination/dislodgement
- Minimal restrictions to activity
- Easier for self-care/hidden
BUT
- Surgical/radiology guided insertion
TPN Monitoring
- Electrolytes
- Glucose
- Liver functions
Long term: conjugated bilirubin, triglycerides
Individualized, others may require different levels of trace elements, nitrogen balance, etc…
What is refeeding syndrome?
Occurrence of electrolyte abnormalities (rapid depletion) in severely malnourished patients during rapid initiation of nutrition
- Can lead to fluid overload (monitor fluid status carefully)
- Start slow and advance over 3 days, initiate TPN at 1/2 of goal rate
Which electrolytes do we pay attention to specifically in refeeding syndrome?
Monitor and aggressively supplement: Potassium, phosphate, magnesium
TPN approaches
Standard approach: Commercial premade TPN bags, NOT for pediatrics
Individualized approach: Compounded prescription TPN, used in NICU/pediatric patients
Cycled TPN: Provided over a rate that is not the usual 24h, used in long term to allow “off time” and minimize risk of IFALD, ramp up and down rate, avoid drastic glucose shifts.
Calculating fluid goals
Neonates: Initial 60-80mL/kg/day, titrated to 120-150mL/kg/day
Pediatrics: 4-2-1 method
1. 0-10kg: 4mL/kg/hr
2. 10-20kg: 2mL/kg/hr
3. any kg>20: 1mL/kg/hr
Adults*: 30-40mL/kg/day
Critically ill adults: minimal mL/kg/day to achieve adequate nutrition
Amino acids (protein)
- 4kcal/gram
- 10mOsm per g/L or 100mOsm/%
- Various solutions available
Nitrogen balance
We want positive (anabolic state, energy in > energy out)
Nitrogen IN: Grams of protein / 6.25 = grams of nitrogen
Nitrogen OUT: UUN (g) + 4
Formula = IN - OUT
UUN = urine urea nitrogen, collected over 12-24 hours
+4 for insensible losses
Increase protein if nitrogen balance is negative
Dextrose (carbohydrates)
- 3.4kcal/gram
- 5mOsm per g/L or 50mOsm/%
- Peripheral limit D10-12.5%
- Product = D70W
Lipid emulsions (fat)
- 9kcal/gram
- Various products with different fat concentration
- Maximum rate of infusion** = 0.15g/kg/hr in pediatrics, 0.11g/kg/hr in adults
- Must administer with a 1.2 micron filter (3-in-1s)
- Maximum hang time of 12 hours
- Certain emulsions may be contraindicated in egg/soybean/fish allergies
Monitoring pearls for lipids
IFALD: liver function tests and bilirubin
Hypertriglyceridemia: TG > 200 mg/dL (neo./ped.), TG > 400 mg/dL (adults)
EFAD: essential fatty acid profiles in malnourished neo./ped. patients or any patient using lipid minimization strategies.
Calcium-Phosphate Precipitation
Concentration dependent reaction leading to in-solution precipitates to form
Affected by:
- Dose of Ca/Phos
- pH
- Temperature
- Time
- Salt form (calcium gluconate preferred)
Separate addition to minimize risk - PHOS FIRST***
Multivitamins
- MUST be included for standard dosing TPN
- Essential for various organ systems and physiological function
- Some patients may need more (individualize) - long term TPN
- Monitor patients on warfarin - contains vitamin K
Trace elements
- Zinc
- Copper
- Manganese
- Chromium
- Selenium
Anion balance
Positive cations MUST be with negative anion
- Ordered based on mEq of cations in TPN
- Acetate or chloride, 1:1, 2:1, 1:2, maximum one or the other
Metabolic ACIDOSIS = increase acetate, decrease chloride
Metabolic ALKALOSIS = decrease acetate, increase chloride
Lipid compatibility problems in TPN (3-in-1)
Creaming: safe to use, reversible
Cracking: UNSAFE to use, irreversible separation
Minimum concentrations for stability:
AA 4%, Dextrose 10%, ILE 2%
Medications in TPN
(insulin, levocarnitine, heparin, famotidine)
- Check compatibility
- Determine risk or clinical utility provided over 24h
Filter requirements
Dextrose-AA: 0.22 micron filter
Lipids/3-in-1: 1.2 micron filter
TPN Use in Special Populations
Hepatic failure/disease: higher branch amino acid, lower aromatic
Diabetes: lower carbs, higher fat
COPD/lung disease: lower carbs, higher fat (less CO2)
Trauma/burns: increased metabolic needs, higher calories, more protein
TPN order steps for adult
- Evaluate fluid and energy requirements
- Calculate kcal/day, g/day, and mL for each macronutrient
- Determine final concentrations of dextrose, AA, and lipids
- Calculate electrolyte doses (consider special circumstances)
- Select appropriate anion balance
- Perform “safety checks”
- Max lipid rate 0.11 g/kg/hr
- Glucose infusion rate close (less than) 4 mg/kg/min
- Estimate osmolarity (AA + dextrose)
- Check line/access (central vs. peripheral)
- if TNA (3-in-1), ensure appropriate macronutrient % for lipid stability
TPN order steps for pediatrics (2-in-1)
- Evaluate fluid and energy requirements
- Calculate kcal/day, g/day, and mL for each macronutrient
- Determine final concentrations of dextrose, AA
- Calculate infusion rates (mL/hr) for 2-in-1 and lipid infusion
- Calculate electrolyte doses (consider special circumstances)
- Select appropriate anion balance
- Perform “safety checks”
- Max lipid rate 0.15 g/kg/hr
- Glucose infusion rate (mg/kg/min)
- Estimate osmolarity (AA + dextrose)
- Check line/access (central vs. peripheral)
