### 1. Diabetes Mellitus (DM)
The primary distinction lies in the mechanism of beta-cell dysfunction.
* **Type 1 DM:** Autoimmune destruction of pancreatic beta cells leading to absolute insulin deficiency.
* **Type 2 DM:** Progressive insulin resistance combined with a relative insulin secretion defect.
* **Diagnosis (Either requires two abnormal tests or one with classic symptoms):**
* Fasting Plasma Glucose (FPG) \ge 126 mg/dL
* HbA1c \ge 6.5%
* 2-hour Oral Glucose Tolerance Test (OGTT) \ge 200 mg/dL
* Random Plasma Glucose \ge 200 mg/dL with classic symptoms (polyuria, polydipsia, weight loss).
* **First-line Pharmacotherapy:** **Metformin** (for T2DM), followed by individualized additions like SGLT-2 inhibitors (excellent for heart failure/CKD patients) or GLP-1 receptor agonists (great for weight loss/ASCVD benefit).
### 2. CVA (Stroke) vs. TIA
Distinguishing between an ischemic event that causes permanent damage and one that is transient.
* **Transient Ischemic Attack (TIA):** A transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia, **without** acute infarction on imaging. Symptoms typically resolve within an hour, though the classic definition allowed up to 24 hours.
* **Cerebrovascular Accident (CVA):** Permanent tissue infarction (ischemic) or bleeding (hemorrhagic) causing persisting neurological deficits.
* **High-Yield Action:** A non-contrast head CT is the immediate first step to rule out a hemorrhagic stroke before initiating any thrombolytic therapy (like IV alteplase, which must be given within 4.5 hours of symptom onset for ischemic CVA).
### 3. DKA vs. HHS
Both are life-threatening diabetic emergencies but have distinct clinical and biochemical profiles.
| Feature | Diabetic Ketoacidosis (DKA) | Hyperosmolar Hyperglycemic State (HHS) |
|---|---|---|
| **Typical Patient** | Type 1 DM (usually younger) | Type 2 DM (usually older) |
| **Pathophysiology** | Absolute insulin deficiency \rightarrow lipolysis \rightarrow ketones | Relative insulin deficiency \rightarrow prevents lipolysis, allows extreme hyperglycemia |
| **Blood Glucose** | Usually 250 - 600 mg/dL | Usually > 600 mg/dL (often > 1000 mg/dL) |
| **Arterial pH** | Acidotic (< 7.30) | Normal (> 7.30) |
| **Ketones / Anion Gap** | Positive / Elevated | Negative (or trace) / Normal |
| **Primary Treatment** | IV Fluids, IV Regular Insulin, **Potassium repletion** | Aggressive IV Fluids, IV Regular Insulin, Potassium repletion |
### 4. Hypertensive Urgency vs. Emergency
The key is not just the blood pressure number, but the presence of **End-Organ Damage**.
* **Hypertensive Urgency:** Severe elevation in BP (typically \ge 180/120 mmHg) *without* acute, progressive target organ damage.
* *Management:* Gradually reduce BP over 24-48 hours using oral medications to prevent cerebral hypoperfusion.
* **Hypertensive Emergency:** Severe elevation in BP *with* evidence of acute target organ damage (e.g., hypertensive encephalopathy, acute myocardial infarction, aortic dissection, acute kidney injury, or pulmonary edema).
* *Management:* Admit to ICU. Administer titratable IV antihypertensives (e.g., Labetalol, Nicardipine, Nitroprusside). Reduce Mean Arterial Pressure (MAP) by 10-20% in the first hour, except in aortic dissection (rapidly lower to < 120 mmHg systolic) or acute ischemic stroke (permissive hypertension allowed).
### 5. Electrolyte Imbalances (High-Yield Focus)
* **Sodium (Na+):** Disorders of sodium are primarily disorders of *water*. Hyponatremia (evaluate volume status: hypervolemic, euvolemic, hypovolemic) must be corrected slowly to avoid **Osmotic Demyelination Syndrome**. Hypernatremia must be corrected slowly to avoid cerebral edema.
* **Potassium (K+):** Always check an ECG.
* *Hyperkalemia:* Peaked T waves, widened QRS. Stabilize cardiac membrane first with **IV Calcium Gluconate**, then shift K+ intracellularly (Insulin + Glucose, Albuterol), then eliminate (Loop diuretics, GI binders, Dialysis).
* *Hypokalemia:* U waves, flattened T waves. Check and replace Magnesium concurrently, as Mg+ deficiency prevents K+ correction.
* **Calcium (Ca2+):**
* *Hypercalcemia:* "Stones, bones, abdominal groans, and psychiatric overtones." Treat with aggressive IV fluids and bisphosphonates.
* *Hypocalcemia:* Look for Chvostek's sign (facial nerve tapping) and Trousseau's sign (carpal spasm with BP cuff).
### 6. Sepsis
* **Definition:** Life-threatening organ dysfunction caused by a dysregulated host response to infection (identified by an acute change in SOFA score \ge 2).
* **Septic Shock:** Sepsis with persisting hypotension requiring vasopressors to maintain MAP \ge 65 mmHg **and** having a serum lactate level > 2 mmol/L despite adequate volume resuscitation.
* **The 1-Hour Bundle:**
1. Measure lactate level.
2. Obtain blood cultures *prior* to antibiotic administration.
3. Administer broad-spectrum antibiotics.
4. Begin rapid administration of 30 mL/kg crystalloid for hypotension or lactate \ge 4 mmol/L.
5. Apply vasopressors if hypotensive during or after fluid resuscitation.
### 7. Tachy-Bradycardia
* **Tachycardia (HR > 100):** Determine if the patient is stable or unstable.
* *Unstable (hypotension, altered mental status, ischemic chest pain):* Requires immediate **synchronized cardioversion** (or defibrillation for pulseless VT/VF).
* *Stable:* Differentiate by QRS width. Narrow complex (SVT, AFib) is managed with vagal maneuvers, adenosine, or rate-control drugs. Wide complex (VTach) requires antiarrhythmics like Amiodarone.
* **Bradycardia (HR < 60):** If symptomatic (fatigue, syncope, hypotension), the first-line drug is **Atropine**. If ineffective, proceed to transcutaneous pacing, or a dopamine/epinephrine infusion. https://encrypted-tbn3.gstatic.com/licensed-image?q=tbn:ANd9GcT7YBWAogI77h3REHbMTE3NS00jxUKSBBydc5Mn-rI6O3QVkJdtENR2u5xW4S6-KCgGly2l5-lJ8A5FJeLoSL0qCa2XIT9blkP8zMjXi2aOFiVPWH0
### 8. Anemia
Classified efficiently by Mean Corpuscular Volume (MCV):
* **Microcytic (MCV < 80 fL):** Iron deficiency (low ferritin, high TIBC), Thalassemia, Lead poisoning, Sideroblastic anemia.
* **Normocytic (MCV 80-100 fL):** Acute blood loss, Hemolytic anemias, Anemia of chronic disease (normal/high ferritin, low TIBC).
* **Macrocytic (MCV > 100 fL):** Megaloblastic causes include Vitamin B12 deficiency (has neurological symptoms) and Folate deficiency (no neurological symptoms). Non-megaloblastic causes include alcohol abuse and liver disease.
### 9. Myocardial Infarction (MI) / Chest Pain
Chest pain requires ruling out life-threatening causes (ACS, Aortic Dissection, Pulmonary Embolism, Tension Pneumothorax).
* **STEMI:** ST-segment elevation on ECG or a new Left Bundle Branch Block (LBBB). Signifies total occlusion of a coronary artery. Requires emergent reperfusion (PCI within 90 minutes or fibrinolytics within 120 minutes). https://encrypted-tbn1.gstatic.com/licensed-image?q=tbn:ANd9GcSbT361nVHHpNBAvqjiLaIPdsApcEb83rcAYY_fZWKPOPjRK3dOFuKxOJ_Ht0e2HefUG-EXKpD7OQ8PLyrF2JM9AtEMyZlRtWhI_JjgiZsEeA4p5p0
* **NSTEMI / Unstable Angina:** ST depressions or T-wave inversions. Differentiated by cardiac biomarkers: Troponins are elevated in NSTEMI and normal in Unstable Angina.
* **Initial Medical Management:** MONA-B (Morphine - use cautiously, Oxygen - only if sat < 90%, Nitroglycerin, Aspirin, Beta-blockers) + P2Y12 inhibitor (e.g., Clopidogrel) and Anticoagulation (e.g., Heparin).
### 10. COPD vs. Asthma
Both are obstructive lung diseases, but their reversibility and pathophysiology differ.
| Feature | Asthma | COPD |
|---|---|---|
| **Onset** | Usually childhood/young adulthood | Usually > 40 years old |
| **Etiology** | Airway inflammation (often allergic/eosinophilic) | Tobacco smoke exposure, Alpha-1 antitrypsin deficiency |
| **Reversibility** | **Reversible** (FEV1 improves \ge 12% after bronchodilator) | **Irreversible** or partially reversible obstruction |
| **Primary Therapy** | Inhaled Corticosteroids (ICS) + PRN Bronchodilators | Long-Acting Bronchodilators (LAMA/LABA). ICS only for severe cases. |
### 11. Pancreatitis / Cholecystitis / Appendicitis
The classic acute abdominal pain triad. https://encrypted-tbn0.gstatic.com/licensed-image?q=tbn:ANd9GcRdVzwrSq4cm_u1Mm3u_TVSbjgy8ShlXOSvUt-CXiEl3OEA1BZm_Z2YxrouQPZDrj32FYRHv-qGgNQkQFgmnok68JMDkVIPXdlkubD8NASlKV3NGqk
* **Acute Pancreatitis:** Severe, sudden epigastric pain radiating to the back, relieved by leaning forward. Elevated serum Lipase (more specific than Amylase). Most common causes are Gallstones and Alcohol. Management is largely supportive: aggressive IV hydration, NPO (bowel rest), and pain control.
* **Acute Cholecystitis:** Right Upper Quadrant (RUQ) pain, often post-prandial (fatty meals), with a positive Murphy's sign (inspiratory arrest on palpation). Ultrasound shows gallbladder wall thickening and pericholecystic fluid. Management: NPO, IV antibiotics, and cholecystectomy.
* **Acute Appendicitis:** Periumbilical pain that migrates to the Right Lower Quadrant (McBurney's point). Accompanied by anorexia, nausea, and fever. Management: Appendectomy.
### 12. Heart Failure
* **HFrEF (Heart Failure with Reduced Ejection Fraction):** Systolic dysfunction (EF \le 40%). The heart muscle is weak and dilated. Treatment relies on guideline-directed medical therapy (GDMT) known to decrease mortality: Beta-blockers, ACEi/ARB/ARNI, Mineralocorticoid Receptor Antagonists (Spironolactone), and SGLT-2 inhibitors.
* **HFpEF (Heart Failure with Preserved Ejection Fraction):** Diastolic dysfunction (EF \ge 50%). The heart muscle is stiff and hypertrophied, unable to relax and fill properly. Management focuses on controlling blood pressure, volume overload (diuretics), and managing comorbidities.
* **Acute Decompensated Heart Failure:** Patient presents in respiratory distress with volume overload. Treat with "LMNOP" (Lasix/Loop diuretics, Morphine, Nitrates, Oxygen, Positioning).
### 13. Pyelonephritis
* An upper urinary tract infection involving the renal parenchyma.
* **Presentation:** Classic triad of fever, flank pain, and costovertebral angle (CVA) tenderness. Often accompanied by lower UTI symptoms (dysuria, frequency) and nausea/vomiting.
* **Diagnosis:** Urinalysis showing pyuria, positive leukocyte esterase, nitrites, and the pathognomonic finding of **White Blood Cell (WBC) casts**, which distinguish it from cystitis.
* **Management:** Outpatient management with oral fluoroquinolones (Ciprofloxacin) if the patient is stable and tolerating PO. Inpatient management with IV Ceftriaxone for complicated cases, pregnancy, or inability to tolerate oral intake.