# A nurse is monitoring a 58-year-old client receiving total parenteral nutrition (TPN) through a central line for severe malnutrition (BMI 14.2). Day 2 labs show: serum phosphorus 1.4 mg/dL (low), magnesium 1.3 mEq/L (low), potassium 2.9 mEq/L (low), glucose 268 mg/dL. The TPN has been infusing at the prescribed rate. Which actions are appropriate? Select all that apply.

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=368105&lang=en  
> language: en  
> subject: Adverse Effects/Contraindications/Interactions  
> category: PPT

## Question

A nurse is monitoring a 58-year-old client receiving total parenteral nutrition (TPN) through a central line for severe malnutrition (BMI 14.2). Day 2 labs show: serum phosphorus 1.4 mg/dL (low), magnesium 1.3 mEq/L (low), potassium 2.9 mEq/L (low), glucose 268 mg/dL. The TPN has been infusing at the prescribed rate. Which actions are appropriate? Select all that apply.

1

Discontinue the TPN infusion and advance the diet to regular oral intake as tolerated due to the electrolyte derangements

2

Inspect the central line entry site every shift for redness, drainage, or tenderness suggestive of CLABSI

3

Initiate sliding-scale insulin coverage and reassess glucose every 4 hours, considering thiamine supplementation

4

Increase the TPN infusion rate by 25 percent to correct the severe malnutrition and provide additional calories for healing

5

Notify the provider about the electrolyte derangements consistent with refeeding syndrome and request decreased TPN infusion rate

6

Replace phosphorus, magnesium, and potassium per protocol while continuing close cardiac monitoring

## Explanation

Severely malnourished clients (BMI 14.2) starting TPN are at high risk for refeeding syndrome — life-threatening intracellular shifts of phosphorus, magnesium, and potassium driven by a carbohydrate-induced insulin surge, causing cardiac arrhythmias, respiratory failure, and rhabdomyolysis. Required actions: (1) notify the provider and decrease TPN rate (severely malnourished clients should start at 25 to 50 percent of goal calories); (2) aggressive electrolyte replacement with cardiac monitoring; (3) glucose management with sliding-scale insulin and thiamine supplementation (which prevents Wernicke encephalopathy during the high carbohydrate load); (5) routine CLABSI surveillance every shift. Increasing the TPN rate (option 4) worsens refeeding. Discontinuing TPN abruptly and switching to oral ad lib (option 1) does not address electrolyte deficits and may not meet caloric needs.

## In-depth explanation

Refeeding Syndrome — Lethal Shifts
Starvation depletes intracellular phos, Mg, and K. Carbohydrate refeeding triggers an insulin surge, driving phos, Mg, and K into cells, with low serum levels causing arrhythmia, respiratory failure, and rhabdomyolysis.

Risk Factors
BMI under 16, weight loss greater than 15 percent, NPO greater than 5 days, alcohol use disorder, anorexia, prolonged fasting.

Management Bundle
1. Slow start (25 to 50 percent of goal calories for the first 48 hours)
2. Replace phos, Mg, and K aggressively, with cardiac monitoring
3. Thiamine 100 mg before or with the first carbohydrate dose (Wernicke prevention)
4. Glucose monitoring with insulin coverage
5. CLABSI surveillance

Wrong Answers
4: Increasing rate accelerates refeeding.
6: Abrupt stop without electrolyte fix is unsafe.

NCSBN Theme
PPT — TPN / Adverse effects.

## Clinical scenario

Scenario
58-year-old, severe malnutrition BMI 14.2, central line TPN started on Day 1.

Day 2 Labs
- Phosphorus 1.4 mg/dL (low)
- Magnesium 1.3 mEq/L (low)
- Potassium 2.9 mEq/L (low)
- Glucose 268 mg/dL (high)

Pattern
Low phos plus low Mg plus low K plus hyperglycemia plus malnutrition plus recent carbohydrate load equals refeeding syndrome.

Concurrent Risks
- CLABSI from central line
- Hyperglycemia from TPN dextrose

## Key concepts

- **Refeeding syndrome** — Life-threatening metabolic shift triggered by reintroduction of nutrition (especially carbohydrate) in malnourished individuals. An insulin surge moves phosphorus, magnesium, and potassium intracellularly, causing severe hypophosphatemia, arrhythmias, respiratory muscle weakness, and Wernicke encephalopathy if thiamine is depleted. Prevention: start at 25 to 50 percent of goal calories, replace electrolytes aggressively, give thiamine 100 mg before refeeding.
- **TPN (Total Parenteral Nutrition)** — IV nutrition delivering complete macro and micronutrients via a central line — used when the GI tract cannot meet needs. Typical components: dextrose, amino acids, lipids, electrolytes, vitamins, trace elements. Major risks: refeeding syndrome, hyperglycemia, CLABSI, liver dysfunction, electrolyte imbalance. Requires daily metabolic monitoring.
- **CLABSI** — Central Line-Associated Bloodstream Infection — bloodstream infection developing 48 hours or more after central line placement, attributable to the line. Hallmarks: fever, line-site erythema, drainage, or tenderness, and positive blood cultures from peripheral and line. Prevention bundle: hand hygiene, full barrier insertion, chlorhexidine skin prep, daily necessity review, sterile dressing changes.

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