SU12.1-3 | Nutrition, Fluids and Electrolytes — Assignment

CLINICAL SCENARIO

Mr K is a 58-year-old man on the surgical ward, day two after an emergency laparotomy for a perforated duodenal ulcer. He weighs 70 kg but has lost about twelve kilograms over the preceding three months because of an obstructing pyloric lesion, eating almost nothing for the last five days before admission. He now has a nasogastric tube draining about one litre of aspirate per day, his urine output is falling, and he has had nothing by mouth since surgery. The intern has prescribed 'one litre of normal saline over 24 hours' and asks the consultant whether they should 'just start full feeds today'. His serum albumin is 24 g/L and the team is unsure whether this proves he is severely malnourished.

1. Nutritional assessment and the albumin question

Classify Mr K's nutritional state using the history and examination. Explain why his serum albumin of 24 g/L cannot be used to confirm or quantify malnutrition, and state what clinical findings you would rely on instead.

Guidance: Make explicit that albumin is a negative acute-phase reactant with a ~20-day half-life; weight loss, intake history, BMI and examination are the real evidence.

2. Causes and consequences of his malnutrition

Enumerate the mechanistic causes of malnutrition that apply to Mr K (reduced intake, impaired digestion/absorption, increased losses, increased demand) and map his likely consequences (impaired wound healing, immune dysfunction, muscle weakness) onto specific surgical risks.

Guidance: Tie each consequence to a complication you would be trying to prevent on the ward.

3. Fluid and electrolyte prescription

Construct a 24-hour fluid prescription by separately estimating maintenance, deficit and ongoing losses for this 70 kg man. State the volume and choice of crystalloid, justify it (normal saline vs Ringer's lactate, including the NG losses), and explain why the intern's single litre of saline is inadequate.

Guidance: Show the three-component arithmetic and account for the ~1 L/day NG aspirate as an ongoing loss; comment on hyperchloraemic acidosis risk with large-volume saline.

4. Nutritional requirement and route

Estimate Mr K's daily energy and protein requirements using working guides (kcal/kg and g/kg). Decide and justify the route of nutritional support — enteral versus parenteral — applying the 'if the gut works, use it' principle to his post-laparotomy situation.

Guidance: Quote ~25-30 kcal/kg/day and ~1-1.5 g/kg/day, then reach a clear, defended route decision.

5. Refeeding syndrome — recognition and prevention

Explain why Mr K is at high risk of refeeding syndrome, the metabolic changes involved (especially hypophosphataemia, plus hypokalaemia and hypomagnesaemia), and the specific preventive plan you would put in place before and during feeding.

Guidance: Emphasise thiamine before feeding, starting the feed slowly, and monitoring/replacing electrolytes; name the clinical dangers of getting it wrong.