When is intravenous protein therapy indicated, and what are the available preparations, dosing regimens, and contraindications?

Intravenous Protein Therapy: Indications, Preparations, and Dosing

Primary Indication and Preparations

Intravenous protein therapy is indicated when parenteral nutrition (PN) is required in critically ill or hospitalized patients who cannot meet protein requirements through oral or enteral routes, using balanced amino acid solutions at 1.3-1.5 g/kg ideal body weight per day. 1

The available IV protein preparations include:

• Balanced amino acid solutions (standard formulation with essential amino acids in physiological proportions) 1
• Glutamine-enriched amino acid solutions (0.2-0.4 g/kg/day of L-glutamine, typically as 0.3-0.6 g/kg/day alanyl-glutamine dipeptide) 1
• Human albumin solutions (5%, 20%, and 25% concentrations) 2, 3

Specific Clinical Indications

Parenteral Nutrition in Critical Illness

Amino acid infusions are indicated when:

• Patients cannot achieve at least 70% of protein requirements through oral or enteral nutrition 1
• Severe trauma or sepsis patients requiring total parenteral nutrition 1
• Acute renal failure patients on continuous renal replacement therapy (requiring 0.4 g nitrogen/kg/day, approximately 2.5 g protein/kg/day) 1
• Malnourished critically ill patients (protein requirements increased by 25-30%) 1

Albumin Administration

Albumin is indicated for:

• Hypovolemic shock (dose and rate adapted to individual response) 2
• Burns beyond 24 hours (target plasma albumin 2.5 ± 0.5 g/100 mL, plasma oncotic pressure 20 mmHg) 2
• Severe hypoproteinemia with edema (usual adult dose 50-75 g daily, children 25 g daily) 2
• Intradialytic hypotension in dialysis patients with low serum albumin (20-25% albumin solution) 4, 5

Dosing Regimens

Amino Acid Solutions

Standard dosing protocol:

• Initial dose: 1.3-1.5 g/kg ideal body weight per day with adequate energy supply 1
• Trauma patients: Mean rate of 1.3 g/kg/day for optimal protein-sparing effects 1
• Septic patients: Mean rate of 1.5 g/kg/day 1
• Anuric/oliguric acute renal failure: Up to 0.4 g nitrogen/kg/day (approximately 2.5 g protein/kg/day) with continuous renal replacement therapy 1
• Hypocaloric feeding: Nitrogen requirements increased by 25-30% 1

Administration considerations:

• Must be given with adequate energy supply (glucose and lipids) for optimal anabolic effects 1
• Combined insulin, glucose, and amino acid administration produces greater anabolic effects than amino acids alone 1

Glutamine Supplementation

When PN is indicated in ICU patients, add:

• 0.2-0.4 g/kg/day of L-glutamine (as 0.3-0.6 g/kg/day alanyl-glutamine dipeptide) 1
• Doses of 10-30 g glutamine/24 hours are safely tolerated and restore plasma levels 1

Albumin Solutions

Dosing by indication:

• Hypovolemic shock: Volume and speed adapted to patient response 2
• Burns: Maintain plasma albumin 2.5 ± 0.5 g/100 mL using 25% albumin 2
• Hypoproteinemia:
  • Adults: 50-75 g daily 2
  • Children: 25 g daily 2
  • Rate should not exceed 2 mL/minute in hypoproteinemic patients to avoid circulatory embarrassment and pulmonary edema 2

Route of Administration

Peripheral vs. Central Access

Peripheral administration:

• Appropriate for short-term PN (less than 10-14 days) 4
• Can provide up to 60 g amino acids per day 4
• Osmolarity must not exceed 850-900 mOsm/L to minimize phlebitis risk 4

Central access:

• Required for long-term PN (>10-14 days) 4
• Allows higher osmolarity solutions 4

Albumin Administration

• Always administered by intravenous infusion 2
• May be given undiluted or diluted in 0.9% sodium chloride or 5% dextrose 2
• For sodium restriction: use undiluted or dilute in sodium-free solutions (5% dextrose) 2
• Use only 16-gauge needles or dispensing pins for 20 mL vials and larger 2

Contraindications and Precautions

Absolute Contraindications

• Ileus (contraindication for enteral protein, not parenteral) 1
• Severe hyperammonemia with risk of cerebral edema (defer protein for 24-48 hours until controlled) 1

Relative Contraindications and Cautions

For amino acid solutions:

• Monitor nitrogen balance in patients with impaired renal function 1
• In acute liver failure with severe hepatic encephalopathy, protein can be deferred 24-48 hours until hyperammonemia is controlled 1
• Monitor arterial ammonia when protein administration is commenced in these patients 1

For albumin:

• Hypoproteinemic patients with normal blood volumes require slower infusion rates (≤2 mL/minute) to prevent circulatory embarrassment and pulmonary edema 2
• 5% albumin should not be used for routine volume replacement due to economic reasons 6
• 20% albumin use in intensive care is limited to situations where capillary leak is unlikely and dose limits of synthetic colloids are reached 6

Monitoring Requirements

Essential monitoring parameters:

• Nitrogen balance (though not reliable for assessing adequate protein synthesis in liver, gut, and immune system) 1
• Plasma triglycerides when lipids are co-administered 4
• Arterial ammonia in patients with hepatic encephalopathy receiving protein 1
• Serum albumin levels in hypoproteinemic patients 2
• Renal function in patients receiving high protein loads 1
• Electrolytes (phosphate, potassium, magnesium) to prevent refeeding syndrome in malnourished patients 4

Common Pitfalls to Avoid

Critical errors in IV protein therapy:

1. Providing amino acids without adequate energy supply - insulin, glucose, and amino acids together produce greater anabolic effects than amino acids alone 1

2. Exceeding optimal amino acid doses - no additional benefit observed beyond 1.3-1.5 g/kg/day in trauma or sepsis patients 1

3. Using 5% albumin for routine volume replacement - not cost-effective; synthetic colloids are preferred 6

4. Rapid infusion of albumin in hypoproteinemic patients - rates >2 mL/minute risk circulatory embarrassment and pulmonary edema 2

5. Continuing aggressive protein support in severe trauma/sepsis expecting to prevent lean tissue loss - lean tissue loss is unavoidable despite aggressive nutritional support due to stress hormones and inflammatory mediators 1

6. Using albumin as a long-term protein source - oral or parenteral feeding with amino acids should be initiated; albumin administration is symptomatic/supportive only 2