USMLE Step 1 preparation

500 Mnemonics for step 1 , available for free till Oct. 25. These are packaged in one book. https://www.amazon.com/dp/B0HLGK7375

Hello, guys! If you’re planning to take the USMLE exam in the future but your English level isn’t strong enough yet, I’m starting online Medical English classes. Please let me know if you’d like to join! 🙌🏻

Sample question: An 18-year-old woman with sickle cell disease is brought to the emergency department by her parents because of a 2-hour history of severe abdominal pain and nausea. Her parents say that she had a cheeseburger, milk shake, and chocolate bar for lunch. Her temperature is 37°C (98.6°F). Physical examination shows tenderness over the right upper quadrant of the abdomen, radiating to the right shoulder. Ultrasonography of the right upper quadrant of the abdomen shows gallstones. Which of the following is the most likely underlying cause of this patient's current condition? A) Decreased hepatic secretion of lecithin B) Decreased reabsorption of bile salts C) High ratio of cholesterol to bile acids in bile D) Infestation with parasites secreting β-glucuronidase E) Overload of unconjugated bilirubin Source: https://www.usmle.org/sites/default/files/2021-10/Step_1_Sample_Items.pdf

Management of gallstones.📌📚 1. If asymptomatic: expectant management 2. If symptomatic and biliary colic is present: 📍Acute pain management: - 1st-line treatment: NSAIDs - 2nd line treatment: if NSAIDs are contraindicated, or doesn’t help → opioids can be given - For patients who present to hospital → ketorolac can be given 📍If pain stays for more than 4 hours, then patients should approach hospital. 📍If acute calculous cholecystitis is diagnosed, then laparoscopic cholecystectomy is gold standard treatment. Source: uptodate.com. Approach to the management of gallstones. Treatment of acute calculous cholecystitis.

📚Anticholinergic drugs and their toxicity. What are anticholinergic drugs? - These are drugs that block the effect of Acetylcholine. Examples of these include atropine, clidinium, belladonna alkaloids, etc. When do we use them? - For example, atropine (IM injections) can be used prior to bronchoscopy to decrease respiratory mucus secretions and promote bronchodilation. It can also be used before eye examination to dilate the pupil (atropine sulfate eye drops). What does Acetylcholine (Ach) do? - Ach is a neurotransmitter that has functions both in the peripheral nervous system and CNS. In the peripheral nervous system, Ach activates muscles and is a major neurotransmitter in the autonomic nervous system (salivary secretion, increases peristalsis, etc). In the CNS, cholinergic projections arising from the basal forebrain, and brainstem regulate cognitive functions of the brain. Anticholinergic toxicity: In PNS: - ↓Sweating → ↓heat dissipation → ↑body temperature → responsive superficial vasodilation → flushed skin. Symptoms visible: dry skin, increased body temperature, flushed skin. - ↓ Peristalsis. Symptoms: urinary retention, constipation. - Paralysis of iris sphincter & ciliary muscle, which leads to mydriasis (dilated pupils), cycloplegia (loss of accommodation) In CNS: - Affects CNS pathways, which leads to altered mental status - Vagal tone at SA node decreases, which leads to tachycardia

The correct answer: C. Linezolid. Explanation: Serotonin syndrome is characterized by a triad of autonomic instability (eg, hyperthermia, hypertension, tachycardia), altered mental status (eg, agitation, confusion), and neuromuscular irritability(eg, tremor, hyperreflexia, myoclonus), as well as GI symptoms and diaphoresis. It may develop when a monoamine oxidase inhibitor (MAOI) antidepressant or a non-antidepressant with MAOI activity (eg, linezolid) is combined with a serotonergic medication such as a selective serotonin reuptake inhibitor (eg, paroxetine), serotonin-norepinephrine reuptake inhibitor, or tricyclic antidepressant. Clindamycin, doxycycline, penicillin, and vancomycin do not have MAOI effects.

Practice question: A 52-year-old woman comes to the emergency department due to recurrent right lower extremity swelling, pain, and erythema. The patient's medical history includes type 2 diabetes mellitus and depression. Her medications include metformin, paroxetine, and a multivitamin. The patient is diagnosed with cellulitis, admitted to the hospital, and started on antibiotics. She is continued on her home medications. Three days later, the patient becomes agitated and delirious with severe abdominal cramps and diarrhea. Her temperature is 39.2 C (102.6 F), blood pressure is 180/100 mm Hg, and heart rate is 120/min and regular. On examination, the patient is diaphoretic and tremulous, and her pupils are dilated. Bilateral hyperreflexia and ankle clonus are present. She begins to have seizures. Which of the following antibiotics was the patient most likely given to treat the cellulitis? A. Clindamycin B. Doxycycline C. Linezolid D. Penicillin E. Vancomycin

This patient is likely taking a first-generation antihistamine (eg, diphenhydramine), which is commonly used for treating environmental allergies and mast cell-related disorders. First-generation antihistamines are nonspecific and act as antagonists to multiple receptors, including the muscarinic acetylcholine receptor. This leads to anticholinergic effects (eg, fever, urinary retention, decreased sweating, altered mental status). In this patient, the flushing is likely a compensatory response to dissipate excess body heat due to decreased sweating, and the pupillary dilation is due to inhibition of the iris sphincter. Although commonly described as H1 receptor antagonists, antihistamines are actually inverse agonists that stabilize the receptor in the inactive state. H1 receptors are found in the vascular endothelium and bronchial smooth muscle, where they mediate vascular permeability and bronchoconstriction, as well as in the central nervous system where they are involved in alertness. Antihistaminic effects relieve nasal congestion, rhinorrhea, sneezing, and itching. First-generation antihistamines cross the blood-brain barrier and cause sedation. By contrast, second-generation antihistamines (eg, loratadine) are more specific to the histamine H1 receptor and have less permeability through the blood-brain barrier; they are generally less effective than first-generation antihistamines but have significantly fewer side effects. (Choice A) Flushing and mydriasis are due to antagonism of the cholinergic receptor, not the H1 receptor. (Choice B) H2 receptors are found on parietal cells in the gastric mucosa. H2 antagonists block gastric acid secretion by parietal cells. (Choice D) Nicotinic cholinergic receptors are found in sympathetic and parasympathetic ganglia and on skeletal muscle cells at the neuromuscular junction. Nicotinic receptor antagonists (eg, rocuronium) are used to induce paralysis in preparation for surgery or endotracheal intubation. Adverse effects include hemodynamic instability (eg, hypotension) and respiratory insufficiency. (Choice E) Alpha-1 adrenoreceptors are located on smooth muscle and neurons. Activation of these receptors increases smooth muscle tone of the iris dilator (causing mydriasis) and blood vessels (causing vasoconstriction); alpha-1 adrenergic agonists (eg, phenylephrine, oxymetazoline) can be used in patients with allergic rhinitis because their vasoconstrictive action reduces nasal congestion. However, vasoconstriction inhibits flushing. Educational objective: First-generation antihistamines are nonspecific and interact with multiple receptors, including the muscarinic receptor. This leads to anticholinergic effects (eg, fever, flushing, mydriasis, urinary retention, tachycardia, altered mental status).

Adverse effects of muscarinic receptor antagonists include dry mouth, mydriasis (causes blurred vision), tachycardia, hot and flushed skin, agitation, urinary retention, constipation, and delirium. A mnemonic to remember these side effects is “red as a beet, dry as a bone, blind as a bat, and mad as a hatter.”

Practice question: A 52-year-old man comes to the office for an annual preventive visit. He has a history of seasonal allergies and has recently started taking a medication that has improved his runny nose, sneezing, and watery eyes. Medical history is remarkable for diet-controlled type 2 diabetes mellitus and eczema. He is not on any other medications. He does not use tobacco, alcohol, or illicit drugs. Examination shows a well-appearing man with flushed cheeks and dilated pupils. This patient's physical examination findings are best explained by which of the following mechanisms?