12.2 PN Infectious, Metabolic & Mechanical Complications
Key Takeaways
- PN—especially central PN—carries high CRBSI/CLABSI risk; use strict asepsis, dedicated lumen preference, hub disinfection, sterile dressing care, and prompt removal when PN is no longer indicated.
- Hyperglycemia is the most common metabolic complication; abrupt cessation of high-dextrose PN can cause rebound hypoglycemia—taper or provide dextrose replacement (e.g., D10 pathway) per protocol when interrupting therapy.
- Refeeding syndrome risks profound drops in phosphate, potassium, and magnesium in severely malnourished patients—start low, advance slowly, and monitor electrolytes closely during initiation.
- Other metabolic issues include hypertriglyceridemia, long-term hepatobiliary complications, and essential fatty acid deficiency when lipids are omitted; mechanical problems include occlusion, thrombosis, malposition, and pump failure.
- Monitor glucose, electrolytes (including Phos, K, Mg), LFTs, triglycerides, weight, and intake/output; escalate early when infection, metabolic instability, or device dysfunction appears.
Complications: the second half of Domain 3H
Knowing the bag composition is not enough. CRNI expects you to prevent, detect, and respond to PN-related harm. Complications group into infectious, metabolic, and mechanical categories—often overlapping in the same patient (for example, a thrombosed lumen that tempts staff to break asepsis while troubleshooting).
Quick Answer: Infection: PN is a CRBSI high-risk therapy—strict asepsis, dedicated line/lumen, minimize breaks. Metabolic: hyperglycemia most common; hypoglycemia if high dextrose stops abruptly; refeeding = falling Phos/K/Mg—start low, go slow; watch triglycerides, liver tests long-term, EFAD without lipids. Mechanical: occlusion, thrombosis, malposition, pump failure. Monitor glucose, electrolytes, LFTs, triglycerides, weight, I&O.
Infectious complications
Why PN elevates bloodstream infection risk
Parenteral nutrition—particularly central PN—is a classic risk factor for catheter-related bloodstream infection (CRBSI) / CLABSI. Contributing factors include:
- Central venous access with prolonged dwell
- Nutrient-rich fluid that can support microbial growth if contaminated
- Frequent hub entries for bag changes, labs, and (improperly) medication piggybacks
- Multi-lumen devices and multi-therapy patients with more manipulation
- Underlying malnutrition and critical illness impairing host defenses
Prevention is non-negotiable nursing work, not optional “extra care”:
| Prevention focus | High-yield actions |
|---|---|
| Hand hygiene | Before every line contact |
| Hub disinfection | Scrub the hub thoroughly; allow dry time; no “quick wipe” habits |
| Aseptic technique | Sterile dressing changes; clean vs sterile procedures per standard and policy |
| Dedicated lumen | Prefer PN-only lumen; reduce incompatible Y-sites and unnecessary entries |
| Dressing integrity | Change when damp, loose, or soiled; maintain CHG-compatible practices per protocol |
| Line necessity | Daily review—remove CVAD/PN when no longer indicated |
| Administration set discipline | Change sets with hang-time rules; do not leave open ports unprotected |
Recognition and response themes
Suspect line infection with new fever, chills, rigors (especially with infusion start), unexplained tachycardia, hypotension, or purulence/erythema at the exit site. Response principles:
- Assess the patient and the site; do not dismiss “low-grade” fever in a PN patient.
- Notify the provider promptly; anticipate blood cultures (peripheral and/or catheter per protocol) and possible antimicrobial therapy.
- Do not routinely “treat through” obvious source control needs without team decisions—catheter removal may be required depending on organism and clinical severity (team decision, not unilateral improvisation).
- Never culture by breaking asepsis further; use correct culture technique.
Exam trap: Drawing labs and giving meds through the PN lumen repeatedly “because it’s already there,” multiplying infection risk without clinical necessity.
Metabolic complications
Hyperglycemia (most common)
Hyperglycemia is the most frequent metabolic complication of PN. Drivers include high dextrose load, stress hormones in critical illness, steroids, infection, and diabetes. Uncontrolled hyperglycemia worsens infection risk and osmotic complications.
Nursing priorities:
- Monitor blood glucose on the ordered schedule (often more frequent during initiation and rate advances).
- Administer insulin only as ordered—PN may contain insulin, and subcutaneous/IV insulin protocols may run in parallel; avoid double-dosing errors.
- Report persistent hyperglycemia so the team can adjust dextrose, insulin, or rate.
- Do not arbitrarily increase PN rate to “finish the bag” when glucose is already uncontrolled.
Hypoglycemia with abrupt interruption
When a patient has been receiving high-dextrose PN, the pancreas (or exogenous insulin) is adapted to that carbohydrate delivery. Abruptly stopping the infusion—bag empty and not replaced, line occluded and ignored, or accidental disconnection—can cause rebound hypoglycemia.
Safe interruption principles:
| Situation | Safer approach |
|---|---|
| Planned cyclic PN | Follow ordered taper down before off-time |
| Unplanned stop / bag delay | Hang dextrose-containing replacement per protocol (commonly a D10 pathway theme on exams) until PN resumes |
| Transfer off unit | Communicate PN dependence; do not clamp high-dextrose PN without a plan |
| Insulin-containing PN stops | Reassess glucose closely; insulin effect may outlast dextrose delivery |
Exam trap: Stopping central PN cold when the pharmacy bag is delayed and “waiting” without providing ordered dextrose coverage.
Refeeding syndrome
Refeeding syndrome occurs when nutrition (enteral or parenteral) is restarted aggressively in a severely malnourished or starved patient. Insulin surges drive glucose and electrolytes intracellularly, producing dangerous drops in:
- Phosphate (hallmark concern—can cause respiratory failure, hemolysis, cardiac dysfunction)
- Potassium
- Magnesium
Clinical associations: chronic alcoholism, anorexia, prolonged starvation, oncology cachexia, long untreated malabsorption.
Prevention mantra: start low, go slow. Monitor baseline and serial electrolytes (especially Phos, K, Mg), replace aggressively as ordered, and advance calories only as labs and clinical status allow. Nursing role is vigilant monitoring and refusal to “maximize calories on day one” against the refeeding plan.
Hypertriglyceridemia
Lipid injectable emulsions and high dextrose (converted to fat) can elevate serum triglycerides. Extremely high triglycerides risk pancreatitis and may require lipid rate reduction or temporary lipid hold per protocol. Check ordered triglyceride monitoring, especially during initiation or when lipids are advanced. Visually, unstable emulsions (cracking) are a separate stability problem—do not hang broken emulsions.
Hepatobiliary and long-term metabolic issues
Long-term PN may associate with PN-associated liver disease patterns (steatosis, cholestasis) and gallbladder stasis, especially when the patient is completely NPO. Teams may use cycling, limit overfeeding, adjust lipid strategies, and push enteral trials when possible. Nursing contributes accurate intake documentation, LFT trend awareness, and infection prevention (sepsis also injures the liver picture).
Essential fatty acid deficiency (EFAD)
If lipids are omitted for prolonged periods, patients can develop essential fatty acid deficiency (dry scaly skin, hair changes, impaired wound healing, laboratory fatty-acid pattern abnormalities). When lipids are held for hypertriglyceridemia or shortage, track duration and escalate so essential fatty acid needs are not forgotten.
Other metabolic notes
- Fluid overload or dehydration from mismatched free water and losses—track weight and I&O.
- Electrolyte disorders beyond refeeding (Na, Ca, acid–base) require ordered adjustments—do not bolus random electrolytes into the PN bag.
- Azotemia / elevated BUN may reflect amino acid load, dehydration, or renal impairment—team adjusts protein.
Mechanical complications
PN depends on a patent, correctly positioned catheter and a functioning pump.
| Mechanical problem | What it looks like / risks | Nursing response themes |
|---|---|---|
| Catheter occlusion | Pump occlusion alarms, inability to aspirate/flush, delayed PN | Assess mechanical kinks first; follow occlusion protocols (thrombotic vs precipitate); never force flush; pharmacy guidance for precipitate concerns |
| Venous thrombosis | Arm/neck swelling, pain, dilated collaterals with PICC/CVC | Report promptly; do not ignore unilateral edema in a CVAD patient on PN |
| Malposition | Aspiration difficulty, infiltration-like chest/neck symptoms, arrhythmias if deep, infiltration if tip migrated | Stop infusion if malposition suspected; obtain ordered verification imaging; do not continue high-osmolarity PN into unknown tip location |
| Pump failure / free flow | Wrong rate, boluses, or stoppage | Use smart pumps, free-flow protection, anti-free-flow sets; treat rate errors as metabolic emergencies when dextrose/insulin involved |
| Filter / set occlusion | Rising pressures, frequent alarms | Inspect for precipitate/kinks; replace set/filter per policy; escalate if recurrent with Ca–PO₄ concern |
| Air embolism risk | Especially with CVAD disconnections | Clamp, secure connections, Trendelenburg/left lateral themes for suspected air embolism emergencies per training |
Exam trap: Forcing a flush against resistance on a PN lumen—risk of catheter rupture or embolizing clot/precipitate.
Monitoring framework
A practical CRNI monitoring bundle for PN patients:
| Parameter | Why it matters |
|---|---|
| Blood glucose | Hyperglycemia most common; hypoglycemia if PN stops abruptly |
| Electrolytes | Na, K, Mg, Phos, Ca—refeeding and ongoing losses |
| LFTs | Long-term hepatobiliary complications; concurrent illness |
| Triglycerides | Lipid tolerance |
| Weight | Fluid status and nutrition trend (daily in acute care when ordered) |
| Intake & output | Overload, dehydration, high GI losses |
| Vital signs & site | Infection and fluid tolerance |
| Line function | Patency, dressing, securement, pump history |
Document bag numbers, rates, interruptions, and patient response. Communicate with pharmacy, dietitians/nutrition support, and providers as a closed loop—PN is inherently multidisciplinary.
Integrated scenarios
Scenario A — Infection: A patient on day 10 of central PN develops rigors 30 minutes after a new bag starts. Assess ABCs and vitals, stop and evaluate per protocol if reaction vs infection is unclear, notify provider, prepare for cultures, and maintain aseptic technique—do not keep breaking the line for nonessential tasks.
Scenario B — Refeeding: A severely underweight patient starts PN; phosphate falls sharply by morning. Recognize refeeding physiology, report urgently, expect electrolyte repletion and possible rate hold/slow advance—do not increase calories to “catch up.”
Scenario C — Abrupt stop: Central PN tubing disconnects and is clamped for an hour while a new bag is ordered. Check glucose, follow D10/replacement dextrose protocol if indicated, and restore ordered PN with taper/rate verification—do not assume asymptomatic status equals safety.
Scenario D — Mechanical: Pump occlusion alarms repeatedly on a 3-in-1 infusion. Check clamps/kinks/filter, assess for precipitate or thrombosis patterns, and escalate—do not force flush or remove the filter to “make it run.”
High-yield exam traps (complications)
- Using a 0.22 filter with lipids (composition error that becomes a mechanical/occlusion problem)
- Running high-dextrose central PN peripherally
- Abrupt PN stop without dextrose taper or D10/replacement plan
- Aggressive calorie advance in a refeeding-risk patient
- Ignoring fever/chills as “just the hospital” in a PN patient
- Forcing flushes against resistance
- Skipping triglyceride or electrolyte monitoring during initiation
- Forgetting EFAD risk when lipids are held for weeks
- Treating pump alarms as nuisance noise while dextrose delivery silently stops
- Piggybacking meds into PN and blaming “mystery precipitates” later
Which metabolic complication is considered the most common with parenteral nutrition?
A severely malnourished patient begins PN. Which electrolyte pattern and prevention strategy best match refeeding syndrome risk?
High-dextrose central PN is interrupted unexpectedly and a replacement bag will be delayed. What is the priority safety principle?
Which statement best describes infectious risk management for a patient receiving central PN?