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SU12.1-3 | Nutrition, Fluids and Electrolytes — Practice Quiz
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Using the Holliday-Segar (4-2-1) rule, what is the hourly maintenance fluid requirement for a 25 kg child?
Correct. The 4-2-1 rule gives 4 mL/kg/h for the first 10 kg (40 mL), 2 mL/kg/h for the next 10 kg (20 mL), and 1 mL/kg/h for each kilogram beyond 20 kg (5 mL for the final 5 kg). 40 + 20 + 5 = 65 mL/hour.
Holliday-Segar maintenance: 4 mL/kg/h for first 10 kg, 2 mL/kg/h for next 10 kg, 1 mL/kg/h thereafter. For a 25 kg child = 40 + 20 + 5 = 65 mL/h.
Apply 4-2-1: first 10 kg = 40 mL/h, next 10 kg = 20 mL/h, remaining 5 kg = 5 mL/h, totalling 65 mL/hour. The other answers misapply or skip the tiered calculation.
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A surgical patient needs crystalloid resuscitation. Which statement comparing 0.9% sodium chloride (normal saline) with Ringer's lactate (RL/Hartmann's) is correct?
Correct. Normal saline contains only sodium and chloride at 154 mmol/L each; large volumes deliver a supraphysiological chloride load and can cause hyperchloraemic metabolic acidosis. Ringer's lactate is more balanced, containing sodium, chloride, potassium, calcium and lactate (metabolised to bicarbonate).
0.9% saline = Na 154, Cl 154 mmol/L → hyperchloraemic acidosis in large volumes. Ringer's lactate is balanced (Na, Cl, K, Ca, lactate→bicarbonate) and more physiological.
Normal saline is sodium chloride only (154/154 mmol/L) and large volumes cause hyperchloraemic acidosis. Ringer's lactate is the more physiological, balanced fluid containing potassium, calcium and lactate.
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A surgical patient has a functioning, accessible gastrointestinal tract but is unable to meet nutritional needs orally. According to the governing principle of nutritional support, which route should be chosen?
Correct. The principle is 'if the gut works, use it'. Enteral nutrition maintains gut integrity, is more physiological, cheaper, and avoids the line-related and metabolic complications of parenteral nutrition. Parenteral feeding is reserved for when the gut cannot be used.
'If the gut works, use it.' Enteral > parenteral nutrition: more physiological, maintains gut integrity, cheaper, fewer serious complications. Reserve TPN for when the gut cannot be used.
When the gut is functional and accessible, enteral nutrition is preferred — it is more physiological, cheaper and safer than parenteral nutrition. TPN is reserved for an unusable gut.
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A malnourished man who has eaten almost nothing for ten days is started on aggressive feeding. Two days later he develops weakness, confusion and a cardiac arrhythmia, and his bloods show a markedly low phosphate. What is the diagnosis, and what two measures most directly prevent it?
Correct. Refeeding syndrome occurs when a starved patient is fed too quickly: the carbohydrate surge drives potassium, magnesium and especially phosphate into cells, causing hypophosphataemia with cardiac and neurological consequences. Prevention is to give thiamine first, start the feed slowly, and monitor and replace electrolytes.
Refeeding syndrome: starved patient fed too fast → hypophosphataemia (also low K and Mg) with cardiac/neuro harm. Prevent with thiamine first, slow feed introduction, and electrolyte monitoring/replacement.
Weakness, confusion, arrhythmia and a low phosphate after refeeding a starved patient is refeeding syndrome. The two key preventive measures are giving thiamine before feeding and starting the feed slowly with electrolyte monitoring and replacement.
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A resident wants to use the serum albumin to confirm whether a surgical inpatient is malnourished. Why is a single albumin level an unreliable test for this purpose?
Correct. Albumin is a negative acute-phase reactant with a roughly 20-day half-life: it falls with inflammation, sepsis and surgery regardless of nutrition, and its long half-life means it lags real changes. A normal albumin does not exclude malnutrition, and a low one does not prove starvation.
Don't use albumin to diagnose malnutrition: it is a negative acute-phase reactant (~20-day half-life) that falls with inflammation/sepsis/surgery. Assess malnutrition clinically — weight loss, BMI, intake history, examination.
Albumin is a negative acute-phase reactant with a long (~20-day) half-life, so inflammation and surgery lower it independently of nutrition, and it changes slowly. Never use a single albumin to confirm or exclude malnutrition.
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When enumerating the causes of malnutrition in the surgical patient, the mechanisms are best grouped to point toward a remedy. Which option correctly pairs a mechanistic group with an example?
Correct. Reduced intake is one of the mechanistic groups, exemplified by the anorexia of malignancy and chronic disease or a painful, obstructing upper-GI lesion. The other options invert the real mechanisms (sepsis is hypermetabolic; fistulae increase losses).
Causes of surgical malnutrition (each points to a remedy): reduced intake, impaired digestion/absorption, increased losses (fistulae/diarrhoea), and increased demand (sepsis/trauma = hypermetabolic, not hypometabolic).
The causes of surgical malnutrition group into reduced intake (e.g. anorexia, obstructing lesions), impaired digestion/absorption, increased losses (fistulae, diarrhoea), and increased demand (sepsis, trauma — hypermetabolic). Only the 'reduced intake' pairing here is correct.
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