Six days after undergoing a left hemicolectomy for colorectal carcinoma, a 59-year-old man collapses in the hospital hallway and is unconscious for 30 seconds. Afterwards, he complains of shortness of breath and chest pain with deep inhalation. He has hypertension and hyperlipidemia. He smoked one pack of cigarettes daily for 35 years but quit prior to admission to the hospital. He does not drink alcohol. He is in distress and appears ill. His temperature is 36.5°C (97.7°F), blood pressure is 80/50 mm Hg, and pulse is 135/min and weak. Oxygen saturation is 88% on room air. Physical examination shows elevated jugular venous distention. Cardiac examination shows a regular, rapid heart rate and a holosystolic murmur that increases during inspiration. His abdomen is soft and mildly tender to palpation around the surgical site. Examination of his extremities shows pitting edema of the left leg. His skin is cold and clammy. Further examination is most likely to reveal which of the following findings?

Dilated right ventricular cavity

Reduced regional ventricular wall motion

Rapid, aberrant contractions of the atria

Stenosis of the carotid arteries

Anechoic space between pericardium and epicardium

An infant boy of unknown age and medical history is dropped off in the emergency department. The infant appears lethargic and has a large protruding tongue. Although the infant exhibits signs of neglect, he is in no apparent distress. The heart rate is 70/min, the respiratory rate is 30/min, and the temperature is 35.7°C (96.2°F). Which of the following is the most likely cause of the patient’s physical exam findings?

Congenital agenesis of an endocrine gland in the anterior neck

Autosomal dominant mutation in the SERPING1 gene

Genetic imprinting disorder affecting chromosome 11p15.5

Type I hypersensitivity reaction

Excess growth hormone secondary to pituitary gland tumor

Three days after undergoing an open cholecystectomy, a 73-year-old man has fever and abdominal pain. He has hypertension, type 2 diabetes mellitus, chronic obstructive pulmonary disease, and benign prostatic hyperplasia. He had smoked one pack of cigarettes daily for 40 years but quit 1 year ago. He does not drink alcohol. Prior to admission to the hospital, his medications included lisinopril, metformin, ipratropium, and tamsulosin. He appears acutely ill and lethargic. His temperature is 39.5°C (103.1°F), pulse is 108/min, respirations are 18/min, and blood pressure is 110/84 mm Hg. He is oriented only to person. Examination shows a 10-cm subcostal incision that appears dry and non-erythematous. Scattered expiratory wheezing is heard throughout both lung fields. His abdomen is distended with tenderness to palpation over the lower quadrants. Laboratory studies show: Hemoglobin 10.1 g/dl Leukocyte count 19,000/mm3 Serum Glucose 180 mg/dl Urea Nitrogen 25 mg/dl Creatinine 1.2 mg/dl Lactic acid 2.5 mEq/L (N = 0.5 - 2.2 mEq/L) Urine Protein 1+ RBC 1–2/hpf WBC 32–38/hpf Which of the following is the most likely underlying mechanism of this patient's current condition?

Intraabdominal abscess formation

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 complications for USMLE Step 2 CK: High-Yield Surgery Lessons

😴 Uh Oh, Asleep!

Malignant Hyperthermia (MH):
- Triggers: Succinylcholine, volatile anesthetics.
- Patho: Defective ryanodine receptor (RYR1) → massive intracellular Ca²⁺ release.
- Sx: Fever, muscle rigidity, tachycardia, ↑ETCO₂, rhabdomyolysis.
Laryngospasm: Vocal cord adduction → obstruction. Tx: Positive pressure ventilation, deepen anesthesia, succinylcholine.
Aspiration Pneumonitis: Prevent with NPO status & rapid sequence intubation.
Hypotension: Common with propofol, volatiles, neuraxial block.

⭐ Dantrolene treats MH by binding the RYR1 receptor, blocking Ca²⁺ release from the sarcoplasmic reticulum.

🎭 Pathophysiology - The Dantrolene Drama

Malignant Hyperthermia (MH): Autosomal dominant defect in ryanodine receptor (RYR1). Triggers like volatile anesthetics or succinylcholine cause massive, uncontrolled $Ca^{2+}$ release from the sarcoplasmic reticulum.
- Leads to: Hypermetabolism (↑temp, ↑ETCO₂), muscle rigidity, rhabdomyolysis (↑K⁺, ↑CK), and acidosis.
- Tx: Dantrolene, a RYR1 antagonist.
Anaphylaxis: Type I (IgE-mediated) hypersensitivity. Triggers (e.g., neuromuscular blockers, antibiotics) cause mast cell degranulation, releasing histamine.
- Leads to: Vasodilation (hypotension), bronchospasm, urticaria.
- Tx: Epinephrine.

⭐ The earliest, most sensitive sign of MH is an unexpected rise in end-tidal $CO_2$ (ETCO₂).

🚩 Clinical Manifestations - Red Flags Rising

Complication	Key Signs & Symptoms
Malignant Hyperthermia (MH)	Sudden ↑ETCO₂ (earliest), tachycardia, masseter muscle rigidity, hyperkalemia, hyperthermia (late).
Local Anesthetic Systemic Toxicity (LAST)	📌 Biphasic: CNS excitation (perioral numbness, tinnitus, seizures) followed by CNS depression (coma, respiratory arrest) & CV collapse.
Anaphylaxis	Sudden severe hypotension, bronchospasm (↑peak airway pressure), tachycardia, urticaria, angioedema.
Perioperative MI	Often silent ("painless"). May manifest as unexplained hypotension, new arrhythmia (e.g., AFib), or ST changes on ECG.

🩺 Diagnosis - Spotting the Trouble

Monitor Vitals & Capnography: The first line of detection.
Malignant Hyperthermia (MH): Unexplained ↑ ETCO2 is the earliest sign. Followed by tachycardia, muscle rigidity, and hyperthermia (late).
Anaphylaxis: Sudden ↓ BP, ↑ HR, bronchospasm, rash. Confirm with ↑ serum mast cell tryptase.
MH Susceptibility: Caffeine-halothane contracture test (gold standard); genetic testing for RYR1 mutations for at-risk families.

⭐ An abrupt, unexplained rise in end-tidal CO₂ is the most sensitive sign of Malignant Hyperthermia, often preceding fever.

🚨 Management - Code Blue Anesthesia

Malignant Hyperthermia (MH): Immediate, stepwise intervention is critical.

Local Anesthetic Systemic Toxicity (LAST):
- Manage ABCs; treat seizures with benzodiazepines.
- Administer 20% lipid emulsion therapy.
Anaphylaxis:
- Epinephrine is first-line (0.3-0.5 mg IM).
- Secure airway, IV fluids, H1/H2 blockers, corticosteroids.

⭐ Dantrolene acts by blocking ryanodine receptors (RyR1) in skeletal muscle, preventing Ca²⁺ release from the sarcoplasmic reticulum, directly treating MH pathophysiology.

⚡ High-Yield Points - Biggest Takeaways

Malignant Hyperthermia (MH): Triggered by succinylcholine/volatile anesthetics. Presents with fever, rigidity, and ↑CK. Treat with dantrolene.

Local Anesthetic Systemic Toxicity (LAST): CNS changes (seizures) and cardiovascular collapse. The antidote is intralipid emulsion.

Postoperative Fever: Early fever (<48h) is often non-infectious (atelectasis). Later fever suggests infection (UTI, wound).

Aspiration Pneumonitis: Chemical lung injury. Prevent with NPO status and rapid sequence intubation.

Succinylcholine can cause life-threatening hyperkalemia in burn, crush, or neuromuscular disease patients.

Postoperative hypothermia impairs coagulation and increases wound infection risk.

Continue reading on Oncourse

CONTINUE READING — FREE

or get the app

App Store|Google Play