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SU12.1-3 | Nutrition, Fluids and Electrolytes — Graded Quiz
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Total body water (TBW) is approximately 60% of body weight in an adult man. How is this water distributed between the intracellular and extracellular compartments?
Correct. Of total body water (~60% of body weight, ~42 L in a 70 kg man), about two-thirds is intracellular and one-third extracellular. The extracellular fluid is further divided, with plasma forming roughly a quarter of it and interstitial fluid the rest.
TBW ≈ 60% body weight; ICF two-thirds, ECF one-third. Within ECF, plasma ≈ a quarter and interstitial fluid the rest. This framework underpins rational fluid prescribing.
TBW is roughly two-thirds intracellular and one-third extracellular; plasma is about a quarter of the extracellular fluid. The other distributions are incorrect.
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A safe fluid prescription for a surgical patient is built by adding three separately estimated components. Which option correctly names all three?
Correct. A rational fluid prescription sums three estimates: maintenance (normal obligatory losses), the existing deficit (e.g. from vomiting, fasting or third-spacing), and ongoing losses (e.g. NG aspirate, fistula, drain output). Each is estimated separately and added.
Fluid prescription = maintenance + deficit + ongoing losses, each estimated separately. Never prescribe a fixed volume for every patient.
The three components of a fluid prescription are maintenance, deficit (existing losses), and ongoing losses. Transfusion, nutrition, antibiotics and analgesia are separate considerations, and a fixed volume for everyone is unsafe.
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As a working guide, what is the approximate daily energy (calorie) requirement of an adult surgical patient receiving nutritional support?
Correct. An adult surgical patient needs roughly 25-30 kcal/kg/day as a working estimate, with protein around 1-1.5 g/kg/day, adjusted for the clinical state. This estimate guides whichever route — enteral or parenteral — is chosen.
Working nutritional estimate: ~25-30 kcal/kg/day energy and ~1-1.5 g/kg/day protein, adjusted to the clinical state. Estimate the requirement first, then choose the safest effective route.
The working caloric estimate for an adult surgical patient is about 25-30 kcal/kg/day. The very low and very high figures, and a fixed weight-independent value, are all incorrect.
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A patient is receiving total parenteral nutrition (TPN) through a central venous catheter. Which complication is characteristically associated with this route specifically (rather than with enteral feeding)?
Correct. Parenteral nutrition is delivered through a central line, so catheter-related bloodstream infection (line sepsis) is a characteristic and serious complication, along with metabolic disturbances and line-related mechanical problems. Tube displacement, diarrhoea and aspiration are enteral-feeding complications.
Parenteral nutrition complications: line sepsis, mechanical line problems, and metabolic disturbances (including refeeding). Enteral complications are mostly mechanical/GI: tube malposition, aspiration, diarrhoea.
Line sepsis (catheter-related bloodstream infection) is the characteristic complication of central parenteral nutrition. NG tube displacement, feed-related diarrhoea and aspiration are complications of enteral feeding.
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When assessing a surgical patient for malnutrition, which finding from the history and examination is the single most useful pointer, given that biochemical markers like albumin are unreliable?
Correct. Structured malnutrition assessment begins with the history and examination, and documented unintentional weight loss is among the most useful pointers, alongside reduced intake, low BMI and physical signs of muscle/fat loss. Albumin is unreliable for this purpose.
Assess malnutrition clinically: unintentional weight loss, reduced intake, low BMI, and signs of muscle/fat loss. Don't rely on albumin — it is a negative acute-phase reactant that misleads.
The most useful clinical pointer to malnutrition is significant unintentional weight loss, supported by intake history, BMI and examination. A normal albumin does not exclude malnutrition, and glucose or an isolated tachycardia are not specific markers.
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