Source / episode info
- **Episode:**175
- **Title:**Divine Intervention Episode 175 – USMLE Step 2CK Rapid Review Series 23 (Psych).
- **Published:**2019-10-23
- Source:Episode page
One-liner
This episode reviews high-yield psychiatric topics including differentiating anorexia nervosa from bulimia and binge eating disorder; managing electrolyte imbalances secondary to vomiting; recognizing neurotransmitter deficits in various syndromes (e.g., PD vs. Lewy Body Dementia); and mastering the acute management of mania, stress disorders, and drug toxicities like isoniazid seizures.
High-yield summary
- Anorexia Nervosa: Requires a BMI below normal weight AND distorted body image; must be distinguished from Bulimia (binge + compensatory behavior) and Binge Eating Disorder (binge only).
- Vomiting/Electrolytes: Chronic vomiting leads to hypochloremia, metabolic alkalosis, and volume depletion -> activation of RAAS -> hypokalemia.
- Cocaine Overdose: Presents as a hypertensive crisis due to sympathomimetic effects (_1 agonism). Treatment requires an -blocker (e.g., Phentolamine) or benzodiazepine; avoid -blockers due to unopposed -stimulation.
- Neurotransmitter Syndromes: Parkinson's disease involves low dopamine; Lewy Body Dementia is characterized by low dopamine and low acetylcholine, with dementia preceding motor symptoms.
- Myasthenia Gravis (MG): Autoantibodies against the nicotinic ACh receptor; diagnosis confirmed by improvement after an acetylcholinesterase inhibitor (e.g., Neostigmine/Tensilon).
- Isoniazid Toxicity: Requires mandatory Vitamin B6 supplementation because INH depletes pyridoxal phosphate, leading to decreased glutamate decarboxylase activity -> low GABA and high glutamate levels, predisposing to seizures.
Learning objectives
- Differentiate the diagnostic criteria for Anorexia Nervosa, Bulimia Nervosa, and Binge Eating Disorder based on weight status and compensatory behaviors.
- Predict the expected electrolyte abnormalities (hypochloremia, hypokalemia, metabolic alkalosis) following chronic vomiting.
- Outline the management of hypertensive crises related to sympathomimetic drug use or dietary triggers (MAOIs).
- Correlate specific neurotransmitter deficiencies (e.g., low ACh in MG/AD; low DA in PD/DLB) with clinical syndromes and appropriate diagnostic tests.
- Determine the acute first-line management for severe mania versus chronic bipolar disorder exacerbations.