ECOM-CR Medical Licensure cheat sheet

Osmolarity = 2[Na+] + [glucose]/18 + [BUN]/2.8 (all mg/dL); effective osmolarity (tonicity) omits urea.

Henderson-Hasselbalch: pH = 6.1 + log([HCO3-]/(0.03 x PaCO2)); acute respiratory change of 10 mmHg PaCO2 shifts pH about 0.08.

Enzyme kinetics: Km is substrate concentration at half Vmax; competitive inhibitors raise Km with unchanged Vmax, noncompetitive lower Vmax.

Cardiac output = heart rate x stroke volume; stroke volume depends on preload, afterload, and contractility (Frank-Starling).

Renal clearance Cx = (Ux x V)/Px; inulin clearance approximates GFR, PAH clearance approximates renal plasma flow.

Autosomal recessive disease requires two carrier parents; recurrence risk 25% per pregnancy, with 2/3 of unaffected siblings being carriers.

Mitochondrial inheritance is maternal; both sexes affected, but only daughters transmit the trait.

Nernst equation: E = (61.5/z) log([ion]out/[ion]in) mV at 37 C; resting membrane potential is set mainly by K+ permeability.

Acute coronary syndrome: ST-elevation STEMI triggers immediate reperfusion; NSTEMI/unstable angina uses risk stratification (TIMI/GRACE) before invasive strategy.

Diabetic ketoacidosis: anion-gap metabolic acidosis with ketones; treat with isotonic saline, insulin infusion, and potassium replacement once K+ is below 5.2 mEq/L.

Heart failure with reduced ejection fraction (EF <40%) benefits from ARNI/ACEi, beta-blocker, MRA, and SGLT2 inhibitor (four pillars).

Hyperkalemia with ECG changes: IV calcium gluconate first for membrane stabilization, then insulin/glucose and beta-agonist to shift K+ intracellularly.

Community-acquired pneumonia: CURB-65 (confusion, urea >7 mmol/L, respiratory rate >=30, BP low, age >=65) guides site of care.

Thyroid storm: high fever, tachycardia, agitation, and altered mentation; treat with beta-blocker, thionamide, iodine (after thionamide), and steroids.

Nephrotic syndrome: proteinuria >3.5 g/day, hypoalbuminemia, edema, hyperlipidemia; minimal change disease is the commonest cause in children.

ATLS primary survey sequence: airway with cervical spine protection, breathing, circulation with hemorrhage control, disability, exposure/environment.

Shock index = heart rate / systolic BP; a value above 0.9 suggests occult hemorrhage in trauma.

Acute appendicitis: migration of periumbilical pain to right lower quadrant with McBurney point tenderness and rebound; Alvarado score aids diagnosis.

Bowel obstruction: air-fluid levels on upright radiograph; initial management is IV fluids, nasogastric decompression, and serial abdominal exams.

Perioperative VTE prophylaxis: Caprini score risk-stratifies; use mechanical prophylaxis plus low-molecular-weight heparin for high-risk patients.

Malignant hyperthermia: hypercarbia, rigidity, and rising temperature after volatile anesthetics or succinylcholine; treat with dantrolene.

Anastomotic leak presents with tachycardia, fever, and peritonitis; CT with contrast and early re-exploration may be required.

Surgical site infection prevention: timely prophylactic antibiotics within 60 minutes of incision, normothermia, and glycemic control.

APGAR: Appearance, Pulse, Grimace, Activity, Respiration scored 0-2 each at 1 and 5 minutes; score >=7 is generally reassuring.

Pediatric maintenance fluids (Holliday-Segar): 4 mL/kg/h for first 10 kg, 2 mL/kg/h for next 10 kg, 1 mL/kg/h for each kg above 20.

Normal pediatric heart rate declines with age: newborn 100-160, infant 100-150, school-age 70-110 beats/min.

Kawasaki disease: fever >=5 days plus 4 of 5 criteria (rash, conjunctivitis, mucosal changes, extremity changes, cervical lymphadenopathy); treat with IVIG and aspirin.

Croup: barking cough and inspiratory stridor; treat with dexamethasone and nebulized epinephrine for moderate to severe cases.

Neonatal jaundice: phototherapy threshold depends on age in hours and risk factors; exchange transfusion for severe hyperbilirubinemia.

Intussusception: colicky pain, currant-jelly stool, and sausage-shaped mass; air or contrast enema is diagnostic and therapeutic.

Naegele rule: estimated due date = first day of last menstrual period + 7 days - 3 months (280 days from LMP).

Preeclampsia: hypertension after 20 weeks plus proteinuria or end-organ dysfunction; delivery is the definitive treatment.

Ectopic pregnancy: positive hCG with no intrauterine pregnancy on ultrasound; treat with methotrexate if stable, surgery if ruptured.

Postpartum hemorrhage: uterine atony is the commonest cause; give oxytocin, then uterotonics, and perform uterine massage.

Group B streptococcus prophylaxis: IV penicillin at least 4 hours before delivery for colonized or high-risk women.

Cervical cancer screening: cytology every 3 years from age 21, or co-testing with HPV every 5 years from age 30.

Gestational diabetes screening: 50-g glucose challenge at 24-28 weeks, followed by 100-g 3-hour oral glucose tolerance test if abnormal.

Major depressive disorder requires >=5 symptoms for >=2 weeks, including depressed mood or anhedonia, with functional impairment.

Serotonin syndrome: clonus, hyperreflexia, and agitation after serotonergic agents; treat by stopping the agent and giving benzodiazepines.

Neuroleptic malignant syndrome: rigidity, hyperthermia, autonomic instability, and elevated CK after dopamine antagonists; treat with dantrolene or bromocriptine.

First-line treatment for schizophrenia is a second-generation antipsychotic; monitor for metabolic syndrome and extrapyramidal symptoms.

Delirium: acute fluctuating attention and awareness with altered level of consciousness; identify and treat the underlying cause.

Alcohol withdrawal: benzodiazepines are first-line; monitor for seizures and delirium tremens, which carries significant mortality.

Lithium toxicity: tremor, ataxia, confusion, and vomiting; levels above 1.5 mEq/L require discontinuation and possibly dialysis.

Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); positive predictive value depends on disease prevalence.

Relative risk = incidence in exposed / incidence in unexposed; odds ratio approximates RR when disease is rare.

Number needed to treat = 1/absolute risk reduction; attributable risk = incidence in exposed - incidence in unexposed.

Herd immunity threshold = 1 - 1/R0; higher R0 requires higher vaccination coverage.

Informed consent requires capacity, adequate disclosure, understanding, and voluntariness; emergency exceptions apply when life-threatening.

Confidentiality may be breached when required by law (reportable diseases) or to prevent serious imminent harm to a third party.

Screening test criteria include high prevalence, detectable preclinical phase, acceptable treatment, and favorable test performance.

ABCDE approach: airway, breathing, circulation, disability, exposure; reassess after every intervention.

Anaphylaxis: IM epinephrine 0.3-0.5 mg (1:1000) into the anterolateral thigh; repeat every 5-15 minutes as needed.

Cardiac arrest: high-quality CPR at 100-120 compressions/min, depth 5-6 cm, with minimal interruptions; defibrillate shockable rhythms.

Glasgow Coma Scale: eye 1-4, verbal 1-5, motor 1-6; score <=8 generally indicates need for airway protection.

Stroke: activate stroke pathway; IV thrombolysis within 4.5 hours of onset for eligible patients, with CT to exclude hemorrhage.

Sepsis bundle: measure lactate, obtain cultures, give broad-spectrum antibiotics and 30 mL/kg crystalloid for hypotension or lactate >=4.

Opioid overdose: give naloxone and support ventilation; titrate to restore adequate breathing rather than full wakefulness.