A 21-year-old man undergoes orthopedic surgery for a leg fracture that he has sustained in a motorbike accident. After induction of anesthesia with desflurane, the patient's respiratory minute ventilation decreases notably. Which of the following additional effects is most likely to occur in response to this drug?

Increased intracranial pressure

Increased skeletal muscle tonus

Increased cerebral metabolic rate

Increased glomerular filtration rate

A 5-year-old boy is brought to the emergency department by his grandmother because of difficulty breathing. Over the past two hours, the grandmother has noticed his voice getting progressively hoarser and occasionally muffled, with persistent drooling. He has not had a cough. The child recently immigrated from Africa, and the grandmother is unsure if his immunizations are up-to-date. He appears uncomfortable and is sitting up and leaning forward with his chin hyperextended. His temperature is 39.5°C (103.1°F), pulse is 110/min, and blood pressure is 90/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 95%. Pulmonary examination shows inspiratory stridor and scattered rhonchi throughout both lung fields, along with poor air movement. Which of the following is the most appropriate next step in management?

Prepare for emergency airway management in the operating room with anesthesia and ENT backup

Direct laryngoscopy and pharyngoscopy

Immediate nasotracheal intubation in the emergency department

Intravenous administration of antibiotics

A 59-year-old man presents to his primary care provider with the complaint of daytime fatigue. He often has a headache that is worse in the morning and feels tired when he awakes. He perpetually feels fatigued even when he sleeps in. The patient lives alone, drinks 2-3 beers daily, drinks coffee regularly, and has a 10 pack-year smoking history. His temperature is 99.0°F (37.2°C), blood pressure is 180/110 mm Hg, pulse is 80/min, respirations are 13/min, and oxygen saturation is 98% on room air. Physical exam is notable for a BMI of 39 kg/m^2. The rest of the patient's pulmonary and neurological exams are unremarkable. Which of the following is the best next step in management?

Alcohol avoidance in the evening

A 5-year-old is brought into the emergency department for trouble breathing. He was at a family picnic playing when his symptoms began. The patient is currently struggling to breathe and has red, warm extremities. The patient has an unknown medical history and his only medications include herbs that his parents give him. His temperature is 99.5°F (37.5°C), pulse is 112/min, blood pressure is 70/40 mmHg, respirations are 18/min, and oxygen saturation is 82% on 100% O2. Which of the following is the best initial step in management?

Albuterol, ipratropium, and magnesium

A 55-year-old man presents to the physician for the evaluation of excessive daytime sleepiness over the past six months. Despite sleeping 8–9 hours a night and taking a nap during the day, he feels drowsy and is afraid to drive. His wife complains of loud snoring and gasping during the night. His blood pressure is 155/95 mm Hg. BMI is 37 kg/m2. Oropharyngeal examination shows a small orifice and an enlarged tongue and uvula. The soft palate is low-lying. The examination of the nasal cavity shows no septal deviation or polyps. Examination of the lungs and heart shows no abnormalities. Polysomnography shows an apnea-hypopnea index of 20 episodes/h. The patient is educated about weight loss, exercise, and regular sleep hours and duration. Which of the following is the most appropriate next step in management?

Continuous positive airway pressure

A 23-year-old G1P0 woman presents to the emergency department with regular and painful contractions that occur every 3 minutes. She was at home cooking dinner when she experienced a deluge of clear fluid between her legs followed by painful contractions. The patient has a past medical history of obesity. Her pregnancy was not followed by an obstetrician, but she notes that she experienced abdominal pain and headaches frequently towards the end of her pregnancy. Her temperature is 99.5°F (37.5°C), blood pressure is 187/128 mmHg, pulse is 110/min, respirations are 17/min, and oxygen saturation is 98% on room air. The patient is started on magnesium sulfate and labetalol. The patient delivers her baby vaginally 2 hours later. On the labor and delivery floor, the patient is notably somnolent. Vitals are notable for respirations of 6 per minute. Physical exam reveals a somnolent woman who is minimally responsive. Cardiopulmonary exam is notable for hypopnea. Neurological exam reveals absent deep tendon reflexes and 3/5 strength in her upper and lower extremities. Which of the following is the next best step in management?

Discontinue current drug infusion

A 19-year-old man is brought to the emergency department 35 minutes after being involved in a high-speed motor vehicle collision. On arrival, he is alert, has mild chest pain, and minimal shortness of breath. He has one episode of vomiting in the hospital. His temperature is 37.3°C (99.1°F), pulse is 108/min, respirations are 23/min, and blood pressure is 90/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 92%. Examination shows multiple abrasions over his trunk and right upper extremity. There are coarse breath sounds over the right lung base. Cardiac examination shows no murmurs, rubs, or gallop. Infusion of 0.9% saline is begun. He subsequently develops increasing shortness of breath. Arterial blood gas analysis on 60% oxygen shows: pH 7.36 pCO2 39 mm Hg pO2 68 mm Hg HCO3- 18 mEq/L O2 saturation 81% An x-ray of the chest shows patchy, irregular infiltrates over the right lung fields. Which of the following is the most likely diagnosis?

Acute respiratory distress syndrome

Anesthesia in special populations for USMLE Step 1: High-Yield Surgery Lessons

👶 Management - Little Lungs, Big Challenges

Infant vs. Adult Airway Anatomy Comparison

Airway Anatomy:
- Large occiput & tongue, anterior/cephalad larynx (C3-C4).
- Epiglottis is long & floppy (omega-shaped).
- Narrowest point: cricoid cartilage (funnel-shaped).
Physiology:
- Respiratory: ↑ O₂ consumption, ↓ Functional Residual Capacity (FRC) → rapid O₂ desaturation.
- Cardiovascular: Cardiac output is heart rate-dependent.
- Pharmacology: ↑ Volume of distribution for hydrophilic drugs; ↑ Minimum Alveolar Concentration (MAC) for volatile anesthetics (except neonates).
Management:
- 📌 Uncuffed ETT size: $(Age/4) + 4$.
- Fluids: Use isotonic solutions (e.g., LR).

⭐ Bradycardia in a pediatric patient during anesthesia is a sign of hypoxia until proven otherwise. The primary response is to ensure adequate oxygenation and ventilation.

👐 Management - Handle With Care

Pediatrics: ↑ risk of laryngospasm. Faster inhalation induction due to ↑ alveolar ventilation/FRC ratio. Precise, weight-based dosing is critical.
Geriatrics: ↓ MAC requirements. Slower circulation time delays IV drug onset. ↑ risk of postoperative cognitive dysfunction (POCD). 📌 Start low, go slow.
Obstetrics: Aortocaval compression requires left uterine displacement. ↑ aspiration risk may necessitate rapid sequence intubation (RSI).
Obesity (BMI > 30): Anticipate difficult airway. ↑ risk of OSA and VTE. Drug dosing adjusted (ideal vs. total body weight).

⭐ In pregnant patients, aortocaval compression by the gravid uterus can cause significant hypotension, especially in the supine position. Always use left uterine displacement after 20 weeks gestation.

Aortocaval compression in pregnant patient with/without LUD

🤰 Management - Two Patients, One Plan

Maternal Changes & Implications:
- Resp: ↓FRC, ↑O₂ consumption → rapid desaturation. Airway edema → difficult intubation.
- CV: Aortocaval compression → supine hypotension. Prevent with left uterine displacement (LUD).
- GI: ↑Aspiration risk → give sodium citrate.
- Anesthetic: ↓MAC by 40%, ↑sensitivity to neuraxial block.
Anesthesia for Cesarean Delivery:
- Neuraxial (Spinal/Epidural): Preferred for most cases.
  - Pros: Awake mother, minimal fetal drug exposure.
  - Cons: Hypotension (treat with phenylephrine).
- General Anesthesia (GA): For emergent cases or contraindications.
  - Requires Rapid Sequence Intubation (RSI).

Aortocaval compression by gravid uterus and LUD relief

⭐ Most anesthetics cross the placenta. Exceptions: Glycopyrrolate, Succinylcholine, Heparin (highly ionized/large).

⚖️ Management - A Weighty Matter

Airway & Respiratory:
- High risk of difficult mask ventilation/intubation & Obstructive Sleep Apnea (OSA).
- Use ramped position ("ear-to-sternal-notch") for airway alignment.
- ↓ Functional Residual Capacity (FRC) → rapid O₂ desaturation.
Pharmacokinetics & Dosing:
- Induction (Propofol): Lean Body Weight (LBW).
- Opioids (Fentanyl): LBW.
- Neuromuscular Blockers (NMBs):
  - Succinylcholine: Total Body Weight (TBW).
  - Rocuronium/Vecuronium: Ideal Body Weight (IBW).
📌 IBW (Devine): Men: $50\text{kg} + 2.3\text{kg}$ per inch > 5 ft.

⭐ Obese patients have a significantly reduced FRC, leading to rapid desaturation during apnea. Effective pre-oxygenation and denitrogenation are critical.

Ramped position for intubation in obese patients

⚡ Biggest Takeaways

Geriatric patients: ↓ MAC, ↓ organ reserve, slower drug clearance, and ↑ risk of postoperative delirium.

Pediatric patients: ↑ MAC, faster induction/emergence, and high risk for laryngospasm and bradycardia.

Pregnant patients: ↓ MAC and ↑ aspiration risk. Prevent aortocaval compression with left uterine displacement.

Obese patients: Difficult airway, risk of OSA/hypoventilation. Dose some drugs based on lean body weight.

Malignant Hyperthermia: Triggered by volatile anesthetics/succinylcholine; treat with dantrolene.

Renal/Hepatic Disease: Requires dose adjustment due to altered drug metabolism/excretion.

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