Managing Parenteral Nutrition

Checkpoint A: Pre-Draft Intake (Mandatory)

1. What is the indication for PN (bowel obstruction, short bowel syndrome, severe pancreatitis, post-surgical ileus)? (Default: document indication)
2. Is enteral nutrition completely impossible, or is this supplemental PN? (Default: confirm EN trial attempted per ASPEN)
3. What is the patient's current weight (actual), height, and BMI? (Default: use measured values)
4. What is the patient's estimated caloric and protein requirement? (Default: 25-30 kcal/kg/day, 1.2-2.0 g protein/kg/day)
5. What venous access is available (central line vs. peripheral)? (Default: central for >900 mOsm/L or >14 days)
6. What are current electrolyte values (Na, K, Mg, Phos, Ca, CO2)? (Default: request comprehensive metabolic panel)
7. Is the patient at risk for refeeding syndrome (malnourished, NPO >7 days, BMI <18.5, alcoholism)? (Default: screen risk factors)
8. What is the patient's glucose control status? (Default: review recent blood glucose values and insulin orders)

Documents to Request

• Current labs: BMP, Mg, Phos, prealbumin/albumin, triglycerides, LFTs, CBC
• Current weight (measured) and height
• Fluid balance records (intake/output)
• Current IV fluid orders (to account for additional fluid and electrolytes)
• Insulin orders and blood glucose monitoring results
• Central line placement confirmation and tip position
• Prior PN orders if transitioning from another formulation
• Dietary/nutrition consult with caloric goal documentation

Step 1: Calculate Macronutrient Requirements

Caloric goals (ASPEN/SCCM guidelines):

• Non-critically ill: 25-30 kcal/kg/day (use actual body weight; use IBW if BMI >30)
• Critically ill: 12-25 kcal/kg/day (permissive underfeeding in early critical illness, days 1-7)
• Obese (BMI >30): 11-14 kcal/kg actual body weight OR 22-25 kcal/kg IBW

Protein goals:

• General adult: 1.2-1.5 g/kg/day
• Critical illness/trauma/burns: 1.5-2.0 g/kg/day
• Hepatic encephalopathy: Do NOT restrict protein (outdated practice); maintain 1.0-1.5 g/kg/day
• Renal failure (non-dialysis): 0.6-0.8 g/kg/day; on dialysis: 1.2-1.5 g/kg/day

Macronutrient distribution:

Glucose infusion rate (GIR): GIR (mg/kg/min) = [Dextrose(g) × 1000] / [weight(kg) × 1440 min/day]

• Target: ≤4-5 mg/kg/min to prevent hyperglycemia and hepatic steatosis

Step 2: Electrolyte and Micronutrient Formulation

Standard adult daily electrolyte ranges in PN:

Additives:

• MVI (adult multivitamin for injection): 10 mL daily
• Trace elements (zinc, copper, manganese, chromium, selenium): per standard formulation
• Thiamine 100 mg IV × 3 days before PN initiation in refeeding risk patients
• Vitamin K 10 mg SC/IM weekly (not added to PN due to stability concerns)

Step 3: Compatibility and Stability Assessment

Critical compatibility checks:

1. Calcium-phosphate solubility: The most dangerous incompatibility. Precipitation of calcium phosphate can cause fatal pulmonary emboli.

   • Use calcium gluconate (not chloride) in PN
   • Apply institution-specific solubility curves based on amino acid concentration, pH, and temperature
   • Calcium and phosphate inversely related: higher amino acid concentration allows more of both
   • Final calcium × phosphate product should not exceed established limits (varies by amino acid brand)

2. Lipid emulsion stability (3-in-1 admixtures):

   • Final dextrose concentration should not exceed 23% (destabilizes lipid emulsion)
   • Monovalent cation concentration ≤150 mEq/L, divalent ≤20 mEq/L
   • pH should remain >5.0; low pH cracks lipid emulsion
   • Visual inspection for creaming, oiling out, or particulate matter

3. Y-site compatibility: If lipids run separately (2-in-1 system), verify Y-site compatibility of all piggybacked medications

Osmolarity calculation: Osmolarity (mOsm/L) ≈ [Dextrose(g) × 5] + [Amino acids(g) × 10] + [Electrolytes(mEq) × 2] per liter

• Peripheral PN: ≤900 mOsm/L (risk of phlebitis above this threshold)
• Central PN: no osmolarity limit (central veins tolerate hyperosmolar solutions)

Step 4: Monitoring Protocol

Refeeding syndrome prevention:

• Start at 50% of caloric goal and advance over 3-5 days
• Supplement thiamine 100 mg IV daily × 3 days before or concurrent with PN initiation
• Aggressively replace phosphorus, potassium, and magnesium before and during PN
• Monitor electrolytes q6-12h for first 72 hours in high-risk patients

Step 5: Transitioning and Discontinuation

• Begin enteral nutrition trial as soon as clinically feasible (PN is a bridge, not a destination)
• Taper PN as enteral intake increases: reduce PN by 50% when EN provides >50% of caloric goal
• Discontinue PN when EN provides ≥60-75% of caloric requirements
• Taper dextrose-containing PN (do not stop abruptly) to prevent rebound hypoglycemia
• Monitor blood glucose q1-2h for 6-12 hours after PN discontinuation
• Document final PN day, reason for discontinuation, and transition plan

Checkpoint B: Post-Draft Alignment (Mandatory)

1. Has caloric goal been calculated using appropriate weight and ASPEN guideline targets?
2. Is the glucose infusion rate within acceptable limits (≤5 mg/kg/min)?
3. Has calcium-phosphate solubility been verified against the amino acid product curve?
4. Is the monitoring plan specific with parameters and frequencies for refeeding risk?
5. Has a transition-to-enteral plan been documented?

Quality Audit

• Indication for PN is documented and enteral nutrition trial was attempted or contraindicated
• Caloric and protein goals are calculated and documented per ASPEN guidelines
• Glucose infusion rate calculated and within ≤5 mg/kg/min
• Lipid dose does not exceed 2.5 g/kg/day and triglycerides are monitored
• Calcium-phosphate compatibility verified using institution-specific solubility curves
• Osmolarity calculated and route-appropriate (peripheral ≤900 mOsm/L)
• Refeeding risk assessed and prevention protocol initiated if high risk
• Thiamine supplemented before or concurrent with PN in malnourished patients
• Electrolyte monitoring plan specified with frequencies
• Blood glucose monitoring and insulin protocol in place
• MVI and trace elements included in daily PN formulation
• PN labeled with complete component listing, rate, and beyond-use dating
• Transition plan to enteral nutrition documented with criteria for PN discontinuation
• PN prepared under aseptic conditions with USP <797> compliance

Guidelines

• Always attempt enteral nutrition before parenteral nutrition; "if the gut works, use it" (ASPEN principle)
• Never exceed calcium-phosphate solubility limits—precipitation has caused patient deaths
• Start PN at 50% goal in malnourished patients and advance over 3-5 days to prevent refeeding syndrome
• Monitor triglycerides before and after lipid initiation; hold lipids if triglycerides >500 mg/dL
• Peripheral PN is limited to ≤900 mOsm/L and typically cannot meet full caloric requirements
• Do not restrict protein in hepatic encephalopathy—this practice is outdated and harmful
• Taper PN gradually (50% for 1-2 hours then discontinue) to prevent rebound hypoglycemia
• Review PN orders daily; nutritional needs change and static orders lead to metabolic complications