A 69-year-old man is brought to the emergency room by his daughter due to confusion. She reports that her father did not remember who she was yesterday, and his refrigerator was completely empty when she tried to make him lunch. She states that he was acting like himself when she visited him last week. She also notes that he has struggled with alcoholism for many years and has not seen a doctor in over two decades. She is unsure if he has any other chronic medical conditions. In the emergency room, the patient’s temperature is 101.2°F (38.4°C), pulse is 103/min, respirations are 22/min, and O2 saturation is 92% on room air. His BMI is 17.1 kg/m^2. Physical exam reveals an extremely thin and frail man who is not oriented to person, place, or time. As he is being examined, he becomes unresponsive and desaturates to 84%. He is intubated and admitted to the intensive care unit for what is found to be pneumonia, and the patient is started on total parental nutrition as he is sedated and has a history of aspiration from a prior hospitalization. Two days later, physical exam is notable for new peripheral edema. Laboratory tests at that time reveal the following: Serum: Na+: 133 mEq/L Cl-: 101 mEq/L K+: 2.4 mEq/L HCO3-: 24 mEq/L BUN: 22 mg/dL Glucose: 124 mg/dL Creatinine: 1.1 mg/dL Phosphate: 1.1 mg/dL Mg2+: 1.0 mg/dL Which of the following could have prevented the complication seen in this patient?

Slow initiation of total parenteral nutrition (TPN)

Initiation of intermittent dialysis

Four days after admission to the hospital for anorexia nervosa, a 20-year-old woman has new-onset palpitations and paresthesias in all four limbs. Prior to admission, she was found unconscious by her parents on the floor of a residential treatment center. The patient was started on a trial of nutritional rehabilitation upon arrival to the hospital. Her temperature is 36°C (96.8°F), pulse is 47/min, and blood pressure is 90/60 mmHg. She is 160 cm tall and weighs 35 kg; BMI is 14 kg/m2. The patient appears emaciated. Examination shows lower leg edema. A 2/6 holosystolic murmur is heard over the 5th intercostal space at the midclavicular line. An ECG shows intermittent supraventricular tachycardia and QTc prolongation. Serum studies show: Day 2 Day 4 Potassium (mEq/L) 3.5 2.7 Calcium (mg/dL) 8.5 7.8 Magnesium (mEq/L) 1.2 0.5 Phosphorus (mg/dL) 3.6 1.5 Which of the following is the most likely underlying cause of this patient's condition?

Uncompensated metabolic alkalosis

A 17-year-old girl is brought in by her mother due to rapid weight loss over the past month. The patient says she has been having episodes of diarrhea, which she attributes to laxatives she takes regularly to keep her weight down. She also says she has not had her period yet. The patient’s mother adds that the patient has been underperforming at school and acting very strangely at home. Her current BMI is 16.8 kg/m2. On physical examination, the skin on her limbs and around her neck is inflamed and erythematous. Her tongue is bright red and smooth. She states that over the last 2 weeks, she has been eating nothing but small portions of fruit. She is diagnosed with a vitamin deficiency. Which of the following statements is true about the vitamin most likely deficient in this patient?

Synthesis requires vitamin B2 and B6

It increases the GI absorption of iron

Synthesis requires vitamin B1 and B6

It is used to treat hypertension

A 46-year-old woman presents to her primary care physician for her annual examination. At her prior exam one year earlier, she had a Pap smear which was within normal limits. Which of the following health screenings is recommended for this patient?

Blood glucose and/or HbA1c screening

Blood pressure at least once every 3 years

A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

"Can you tell me more about the symptoms you have been experiencing?"

"Does the diarrhea typically precede the constipation, or vice-versa?"

"Is the diarrhea foul-smelling?"

"Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"

"Are the symptoms worse in the morning or at night?"

A 66-year-old man weighing 50 kg (110 lb) is admitted to the hospital because of sepsis complicated by acute respiratory distress syndrome. The physician decides to initiate total parenteral nutrition and prescribes short-term hypocaloric intake of 20 kcal/kg/day with 20% of the total energy requirement provided by proteins and 30% provided by fats. The physician calculates that a total volume of 1100 mL/day should be infused during the parenteral nutrition therapy to maintain fluid balance. A colloid containing 10 g/dL of albumin and an emulsion with a fat concentration of 33 g/dL are used to prepare parenteral nutrition modules. Which of the following is the most appropriate module to meet the carbohydrate requirement in this patient over the next 24 hours?

500 mL of 25% dextrose solution

750 mL of 25% dextrose solution

750 mL of 10% dextrose solution

500 mL of 10% dextrose solution

250 mL of 50% dextrose solution

Three days after being admitted to the hospital because of a fall from the roof of a two-story building, a 27-year-old man is being monitored in the intensive care unit. On arrival, the patient was somnolent and not oriented to person, place, or time. A CT scan of the head showed an epidural hemorrhage that was 45 cm3 in size and a midline shift of 7 mm. Emergency surgery was performed with craniotomy and hematoma evacuation on the day of admission. Perioperatively, a bleeding vessel was identified and ligated. Postoperatively, the patient was transferred to the intensive care unit and placed on a ventilator. His temperature is 37°C (98.6°F), pulse is 67/min, and blood pressure is 117/78 mm Hg. The ventilator is set at a FiO2 of 55%, tidal volume of 520 mL, and positive end-expiratory pressure of 5.0 cm H2O. In addition to intravenous administration of fluids, which of the following is the most appropriate next step in managing this patient's nutrition?

Enteral feeding via nasogastric tube

Enteral feeding using a percutaneous endoscopic gastrostomy (PEG) tube

Nutritional assessment and optimization for USMLE Step 1: High-Yield Surgery Lessons

Nutritional Screening - The First Filter

Goal: Rapidly identify patients at nutritional risk who require formal assessment.
Key Triggers:
- Unintentional weight loss > 10% in 6 months or > 5% in 3 months.
- BMI < 18.5 kg/m² or > 25 with comorbidities.
- Inadequate nutrient intake for > 7 days.

⭐ High-Yield: Involuntary weight loss of >10-15% of usual body weight over 6 months is a significant predictor of poor surgical outcomes and is a major criterion for diagnosing severe malnutrition.

Assessment Arsenal - The Deep Dive

Anthropometrics:
- BMI: < 18.5 kg/m² indicates significant risk.
- Weight Loss: Unintentional loss of >10% in 6 months or >5% in 1 month is critical.
Biochemical Markers (Visceral Proteins):
- Albumin: < 3.0 g/dL. Long half-life (~20 days), poor indicator of acute changes.
- Prealbumin (Transthyretin): < 15 mg/dL. Shorter half-life (2-3 days), better for monitoring recent nutritional status.
- Transferrin: < 200 mg/dL. Half-life ~8 days.
Nitrogen Balance: Assesses adequacy of protein provision.
- Formula: $N_{balance} = \frac{Protein\ Intake\ (g)}{6.25} - (UUN + 4g)$

⭐ Prealbumin is the most sensitive indicator for monitoring response to nutritional support due to its short half-life.

Pre-Op Power-Up - The Game Plan

Goal: Identify & correct malnutrition to ↓ post-op morbidity/mortality. Severe malnutrition is a major risk factor for poor wound healing and infection.
Key Markers of Malnutrition:
- Albumin < 3.0 g/dL (chronic)
- Prealbumin < 15 mg/dL (acute)
- Unintentional weight loss > 10-15% over 6 months
- BMI < 18.5 kg/m²
- Nutritional Risk Index (NRI): $NRI = (1.519 \times \text{Albumin}) + (41.7 \times \frac{\text{Present Wt}}{\text{Usual Wt}})$

⭐ Prealbumin (half-life ~2 days) is a more sensitive indicator of acute nutritional changes than albumin (half-life ~20 days), making it ideal for monitoring response to nutritional therapy.

High-Yield Points - ⚡ Biggest Takeaways

Severe malnutrition indicators: albumin <3 g/dL, prealbumin <5 mg/dL, or weight loss >15%.

Enteral nutrition is always preferred over parenteral if the GI tract is functional; it maintains gut integrity.

For severe malnutrition, provide 7-14 days of pre-op nutritional support to reduce postoperative morbidity.

TPN risks include catheter-related infections, hyperglycemia, cholestasis, and refeeding syndrome.

Refeeding syndrome is marked by severe electrolyte shifts (↓PO4, ↓K, ↓Mg) after feeding initiation.

Early postoperative feeding (<24h) reduces infections and hospital stay.

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