1. Supportive Care Integration with Parenteral Nutrition

Effective parenteral nutrition is not delivered in a vacuum. Respiratory and circulatory support must be carefully tailored to preserve gastrointestinal (splanchnic) blood flow, which is essential for preventing gut ischemia and facilitating nutrient utilization by the body.

Mechanical Ventilation Considerations

• Lung-Protective Strategy: Utilize low tidal volumes (4–8 mL/kg of predicted body weight) and maintain a plateau pressure of ≤30 cm H₂O to prevent barotrauma.
• PEEP Optimization: A PEEP of 5–10 cm H₂O can balance alveolar recruitment against potential reductions in venous return and cardiac output.
• Patient Positioning: Elevate the head of the bed to 30–45° to minimize the risk of ventilator-associated pneumonia and aspiration.
• Sedation Management: Coordinate sedation levels to ensure patient-ventilator synchrony while avoiding deep sedation, which can impair gut motility.

Hemodynamic Support and Fluid Management

• First-Line Vasopressor: Norepinephrine (0.01–0.3 µg/kg/min) is preferred to maintain a MAP ≥65 mm Hg, as it has minimal vasoconstrictive effects on the mesenteric artery compared to other agents.
• Adjunctive Vasopressor: Low-dose vasopressin (≤0.04 U/min) can be added to norepinephrine as a splanchnic-sparing adjunct to raise MAP.
• Fluid Choice: Use balanced crystalloids for fluid resuscitation. Avoid large-volume boluses of normal saline, which can worsen metabolic acidosis and exacerbate electrolyte shifts common in patients on PN.

2. Pharmacotherapy: Prophylactic and Supportive Agents

Prophylactic pharmacotherapy is critical for reducing the incidence of major ICU complications, such as VTE and stress ulcers, in vulnerable patients dependent on PN.

Insulin Therapy for Glycemic Control

Hyperglycemia is a common and serious complication of PN. A continuous intravenous insulin infusion is the standard of care for maintaining glycemic control.

• Initiation and Titration: Start a continuous IV insulin infusion via a dedicated line at 0.05–0.1 U/kg/h when blood glucose exceeds 150 mg/dL. Adjust the rate based on a validated protocol.
• Target Range: Aim for a blood glucose level of 110–150 mg/dL. This range balances the benefits of glycemic control (reduced infection risk) with the danger of hypoglycemia.
• Hypoglycemia Management: If glucose drops below 80 mg/dL, hold the insulin infusion, administer 50 mL of D10W as a bolus, and recheck glucose in 15 minutes.

Antimicrobial Lock Therapies

Antimicrobial lock therapies are a salvage strategy, not a routine preventive measure. They are considered for patients with a history of recurrent catheter-related bloodstream infections (CLABSIs) despite proper line care.

• Agents: Common protocols involve instilling Taurolidine 2% or Ethanol 70% into the catheter lumen for a dwell time of 2-4 hours.
• Indication: Reserved for patients with recurrent CLABSIs to salvage a long-term central line.
• Safety: Always verify catheter material compatibility, as ethanol can damage certain types of polyurethane catheters.

3. Prevention of Catheter-Related Complications

The central venous catheter required for PN is a major source of morbidity. Strict adherence to evidence-based insertion and maintenance bundles is the cornerstone of preventing mechanical and infectious complications.

Insertion Bundle

• Asepsis: Perform meticulous hand hygiene before donning a cap, mask, sterile gown, and sterile gloves. Use a full-body sterile drape for the patient.
• Antisepsis: Prep the insertion site with a >0.5% chlorhexidine with alcohol solution, allowing it to air dry completely.
• Site Selection: Use real-time ultrasound guidance for all internal jugular and femoral insertions to reduce mechanical complications. Avoid the femoral site in adults when possible.

Maintenance Practices

• Dressing Care: Use a transparent, semipermeable dressing. Change every 7 days or immediately if it becomes damp, loose, or visibly soiled. Chlorhexidine-impregnated dressings can further reduce risk.
• Hub Care: Vigorously “scrub the hub” with an alcohol or chlorhexidine pad for at least 15 seconds before every access.
• Line Necessity: Perform a daily, formal assessment of the need for the central line. Remove the catheter as soon as it is no longer essential.

4. Management of Metabolic Complications

Parenteral nutrition can cause significant metabolic derangements. Early risk stratification, vigilant monitoring, and proactive interventions are essential to prevent severe complications like refeeding syndrome and liver dysfunction.

Refeeding Syndrome

This is a life-threatening condition caused by rapid shifts in fluids and electrolytes when nutrition is reintroduced in a malnourished patient. Prevention is key.

Parenteral Nutrition-Associated Liver Dysfunction (PNALD)

This complication can range from simple steatosis to cholestasis and fibrosis. It is often multifactorial, but nutritional strategies can mitigate the risk.

• Monitoring: Check liver function tests (ALT, AST, ALP, bilirubin) twice weekly.
• Prevention: The most important step is to avoid overfeeding calories (target 20–25 kcal/kg/day) and dextrose (<5 mg/kg/min).
• Intervention: If LFTs rise, consider switching from a pure soybean oil-based lipid emulsion to a mixed-oil or fish-oil-based formulation, which may have anti-inflammatory properties. Limit lipids to 1 g/kg administered 3 times per week.

5. Multidisciplinary Goals-of-Care and Ethical Considerations

Parenteral nutrition is a form of life support, and its application must align with the patient’s prognosis, quality of life, and expressed wishes. Open and recurrent communication is essential.

Initiation vs. Withholding

The decision to start PN requires a careful assessment of its potential benefits versus its burdens. In cases of refractory multi-organ failure, terminal illness, or when a patient’s prognosis is measured in days, PN may not offer meaningful benefit and can increase complications and suffering.

Shared Decision-Making

These complex decisions should not be made in isolation. Early involvement of a multidisciplinary team including palliative care specialists, ethics consultants, and most importantly, the patient or their surrogate decision-makers is crucial. All discussions, advance directives, and decisions regarding the goals and potential limitations of PN should be clearly documented.

Communication and De-escalation

The goals of care can change as a patient’s clinical condition evolves. Hold weekly interdisciplinary rounds to formally revisit the goals of PN. This creates a structured opportunity to discuss if the therapy is still meeting its intended purpose or if de-escalation or withdrawal is more appropriate.