Nursing Field Notes / GI · Med-Surg Pathophysiology

TPN & Enteral Feeding 🍽️

Two Ways to Feed a Client Who Can't Eat

NG-298 GI ADHD-friendly visual edition

TPN = complete nutrition through a vein, bypassing the gut entirely. Enteral feeding = nutrition through a tube into a working GI tract. Pick TPN when the gut doesn't work; pick enteral when it does — "if the gut works, use it." Both share the same deadly complication if you refeed too fast: refeeding syndrome.

💉 TPN = IV, no gutHyperosmolar — central line only, never peripheral.

🧃 Enteral = tube, gut intactNGT/PEG/G-tube — HOB up 30–45° to prevent aspiration.

🚫 Never stop TPN abruptly= rebound hypoglycemia. Taper, or hang D10W if a bag isn't ready.

⚠️ Refeeding syndromeMalnourished + fed too fast → ↓K⁺ ↓Mg²⁺ ↓PO₄ → cardiac arrest risk.

💉

TPN

SIDE A · FEEDING THE BLOOD, NOT THE GUT

Total Parenteral Nutrition — a bag of complete nutrition that skips digestion entirely.

🩸 What it is & why it needs a central line

TPN delivers the client's entire nutrition — dextrose, amino acids, lipids, electrolytes, vitamins — straight into the bloodstream, bypassing normal digestion in the GI tract. Because the solution is very hyperosmolar (thick), it must run through a large, high-flow central vein so it dilutes quickly instead of damaging a small peripheral vein.

🧠 “TPN is too thick for a thin vein.” Central line only — PICC, subclavian CVC, or internal jugular line, tip ending near the superior vena cava.

🎯 Indications

🔥 Severe pancreatitis (bowel rest, NPO)
🩹 Crohn's disease flare (NPO to rest the gut)
🔥 Severe burns / major trauma — hypercatabolic states
🧬 Prolonged bowel obstruction, short bowel syndrome
🎗️ Chronic malabsorption, some oncology clients

🧠 Reach for TPN when the gut is injured, obstructed, or needs total rest.

⚠️ Administration rules

Never give IV push or piggyback meds through the TPN line
⏳ Start and stop slowly — taper, don't abruptly stop
🔁 Change bag & tubing every 24 hours
⚖️ Daily weights, strict I&O
🧪 Monitor glucose regularly (often q4–6h)

🧠 “One line, one job.” The TPN lumen carries TPN only — nothing else shares that line.

🚨 TPN complications — know the direction of each swing

Complication	Signs	Priority action
🍭 Hyperglycemia	Glucose >180 mg/dL, polyuria, polydipsia, N/V, headache, abd pain	Monitor glucose, sliding-scale insulin per order

🩸 Hypoglycemia (abrupt stop)	Shaky, sweaty, confused — because the pancreas is still pumping insulin for a sugar load that suddenly stopped	Hang D10W (10% dextrose in water) immediately if a new bag isn't ready
🦠 Infection (CLABSI)	Fever, chills, redness at insertion site	Sterile dressing technique, monitor site, blood cultures if febrile
🔥 Stress ulcers	Epigastric pain, occult blood in stool	Monitor for GI bleed; prophylaxis per order

🧠 Start slow, stop slow. Every TPN complication above traces back to one rule: the pancreas needs time to catch up in both directions.

🧃

ENTERAL

SIDE B · FEEDING THE GUT DIRECTLY

Tube feeding — used whenever the GI tract still works but the client can't eat by mouth.

🧃 What it is — tube into a working gut

Enteral feeding delivers formula directly into the stomach or small intestine through a tube — the GI tract must be intact and functioning. Common access: NGT (nasogastric, short-term), PEG (percutaneous endoscopic gastrostomy), G-tube or J-tube (jejunostomy, long-term/surgical).

🧠 "Gut works → use it." Enteral is always preferred over TPN when the GI tract can absorb nutrients — it's cheaper, safer, and preserves gut mucosa.

✅ Aspiration precautions

🛏️ HOB 30–45° during feeds and 30–60 min after
🔁 Continuous feeding preferred over bolus — especially on mechanical ventilation
No bolus feeding via NG tube in a mechanically ventilated client
💧 Check gastric residual volume per protocol

🧠 "A-A" — Aspiration & Airway obstruction are the two big enteral dangers. Elevate the head, keep it that way.

⚠️ Tube complications

📍 Tube displacement/dislodgement
🎈 Abdominal distention
🧱 Clogged tube — flush with water before & after meds/feeds
🫁 Aspiration pneumonia

🧠 Key point: If a PEG tube dislodges and is less than 7 days old, the tract isn't mature — notify the HCP who inserted it before attempting to replace it.

🔀 TPN vs. Enteral — tell them apart fast

	💉 TPN	🧃 Enteral
Route	IV — central line (PICC, subclavian, internal jugular)	Tube — NGT, PEG, G-tube, J-tube
Requires a working gut?	No — bypasses the GI tract entirely	Yes — GI tract must be intact/functioning
Main risk	Infection (CLABSI), hyper/hypoglycemia	Aspiration, tube displacement/clogging
Monitoring	Glucose, daily weight, site/dressing, electrolytes	Tube placement, HOB position, residuals, bowel sounds
Shared danger	Refeeding syndrome — if either is started too fast in a malnourished client

🧠 "If the gut works, use it." Enteral is first-line whenever possible; TPN is the backup when the gut can't be used at all.

⚠️

REFEEDING SYNDROME

STEP 3 · THE SHARED KILLER COMPLICATION

Too much nutrition, too fast, in a starved body — the electrolytes crash exactly when the heart needs them most.

🚨 Mechanism — where the electrolytes actually go

In starvation, the body shifts to fat/protein metabolism and total-body electrolyte stores quietly deplete even while serum levels look normal. Reintroducing carbohydrates too quickly spikes insulin — insulin drives glucose, potassium, magnesium, and phosphate all into the cells, and serum levels of these three crash.

🧠 "Feed fast, crash hard." The very electrolytes the heart depends on get dragged out of the blood the moment nutrition restarts too quickly.

⏱️ Who & when

🍽️ Anorexia nervosa, chronic alcoholism
🚫 Anyone NPO for a prolonged period before feeding starts
⏱️ Onset: 24–48 hours after starting enteral OR parenteral nutrition

🧠 Severely malnourished + fed aggressively = the classic refeeding setup.

🧪 The 3 electrolytes to trend (adult reference ranges)

Electrolyte	Normal range
🟣 Phosphate (PO₄)	3.0–4.5 mg/dL
🟢 Potassium (K⁺)	3.5–5.0 mEq/L
🔵 Magnesium (Mg²⁺)	1.3–2.1 mEq/L

🧠 "PKM" — Phosphate, Kalemia, Magnesium — the refeeding trio, all trending down together.

🚨 Why it kills: cardiac arrhythmia

🍽️ Aggressive refeeding in a malnourished client

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📉 Hypophosphatemia + hypokalemia + hypomagnesemia

▼

💔 Torsades de Pointes → V-fib → cardiac arrest

Low magnesium is a classic trigger of Torsades de Pointes (alongside post-MI and hypoxia). Treatment: IV magnesium sulfate.

🧠 Prevention beats treatment: start nutrition low and slow, advance gradually over days, correct/replace electrolytes before and during feeding, and give thiamine supplementation for at-risk clients.

⚡

QUICK RECALL

SAY IT OUT LOUD

💉 TPN= central line, bypasses gut entirely

🧃 Enteral= tube feeding, gut must work, HOB up

🚫 Never stop TPN abruptly= hang D10W if bag delayed

⚠️ Refeeding syndrome= ↓K⁺ ↓Mg²⁺ ↓PO₄ → Torsades — feed slow

🎯 Cover & check — 4 rapid-fire questions

Q1: Why must TPN run through a central line and not a peripheral IV?

TPN is hyperosmolar/very thick — a peripheral vein can't handle it. A central line (PICC, subclavian, internal jugular) ends near the SVC, where high blood flow dilutes it immediately.

Q2: TPN bag runs empty and a new one isn't ready. What do you hang?

10% dextrose in water (D10W) — to prevent rebound hypoglycemia from abruptly stopping the insulin-stimulating TPN solution.

Q3: What's the #1 aspiration precaution for enteral feeding?

Keep the head of bed elevated 30–45° during the feed and for 30–60 minutes after; use continuous feeding (not bolus) in mechanically ventilated clients.

Q4: A severely malnourished client starts tube feeding and 36 hours later develops a dangerous arrhythmia. What happened, and what electrolytes crashed?

Refeeding syndrome — insulin surge drove potassium, magnesium, and phosphate into the cells. Low magnesium especially can trigger Torsades de Pointes; treat with IV magnesium sulfate.