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Nutrition in the surgical patient and refeeding syndrome
A severely malnourished patient facing major surgery benefits from 7–14 days of nutritional therapy before the operation; after surgery feed early by mouth, prefer enteral to parenteral nutrition, and in a starved patient start slowly to prevent refeeding syndrome.
Why it matters in the exam
Nutrition questions in the exam turn on three decisions. The first is who is at risk: weight loss of more than 10%–15% in six months, a BMI below 18.5 or a low albumin indicate severe malnutrition, and in such a patient major elective surgery is postponed in favour of nutritional support. The second is the route: "if the gut works, use it"; oral or tube feeding is better than parenteral nutrition, and in an ERAS programme the patient eats and drinks on the day of surgery or the day after, even after a bowel anastomosis.
The third decision, and the most often asked, is refeeding syndrome: a patient who has not eaten for many days (an alcoholic patient, a patient with an eating disorder, a neglected older person) is given full feeding, and within days low phosphate, low potassium and magnesium, heart failure, arrhythmias and confusion appear. The exam tests early recognition of at-risk patients, giving thiamine before feeding starts (to prevent Wernicke's), the slow start (about 10 kcal/kg/day, and 5 in extreme cases) and daily monitoring of electrolytes.
Key points
- Severe malnutrition (loss of 10%–15%, BMI below 18.5) — nutritional support for 7–14 days before major surgery.
- "If the gut works, use it"; parenteral nutrition only when the gut is insufficient for more than 7 days.
- ERAS: eating and drinking within 24 hours after surgery.
- Refeeding syndrome: low phosphate, potassium and magnesium, heart failure and arrhythmias.
- Prevention: thiamine first, start at 10 kcal/kg/day and increase slowly.
Summary table
| Topic | The rule | Exam note |
|---|---|---|
| Severe malnutrition before surgery | Weight loss above 10%–15% in six months, BMI below 18.5, albumin below 30 g/L without liver or kidney disease | Nutritional therapy for 7–14 days before major elective surgery |
| Route of feeding | Oral, and if not possible — tube; intravenous only when the gut is unavailable or insufficient | Enteral feeding preserves the gut barrier and reduces infections |
| After surgery (ERAS) | Eating and drinking within 24 hours, even after a bowel anastomosis; no routine nasogastric tube | Prolonged post-operative fasting does not help |
| Parenteral nutrition | When more than 50% of needs cannot be met enterally for more than 7 days | Risk of line infection and metabolic disturbances |
| Requirements | 25–30 kcal/kg/day; protein 1.5 g/kg/day | In the critically ill increase gradually |
| High risk of refeeding | BMI below 16, weight loss above 15% in 3–6 months, little intake for more than 10 days, or low potassium, phosphate and magnesium before feeding | Start at 10 kcal/kg/day, thiamine and electrolyte correction |
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Sources
- ESPEN guideline: Clinical nutrition in surgery, 2021 — Pre-operative nutritional therapy, early oral feeding and indications for parenteral nutrition
- NICE guideline CG32: Nutrition support for adults, 2006 (updated 2017) — Criteria for refeeding problems and how to start feeding
- ERAS Society guidelines for elective colorectal surgery, 2018 — Pre-operative carbohydrate loading and early post-operative feeding
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.