ENAM cheat sheet

ENAM (Examen Nacional de Aspirantes a Residencias Médicas) is a high-stakes Mexican national multiple-choice exam used to allocate residency (residencia médica) positions across specialties and institutions.

Items are single-best-answer, clinically oriented, and drawn from the full undergraduate medical curriculum; each item has one correct option and three or more distractors.

Scoring is by number of correct answers; there is no penalty for wrong answers, so every item must be answered before time expires.

The exam is norm-referenced for placement: your standing depends on the score distribution of all applicants competing for the same specialty and site, not on an absolute pass mark.

Time management rule: allocate roughly equal time per item, flag long calculation or multi-step items, and return to them after completing all single-fact recall items.

Highest-yield domains by item volume are typically internal medicine, pediatrics, gynecology-obstetrics, and surgery; public health and ethics appear in smaller but consistent proportions.

Guessing strategy: eliminate options that are internally contradictory or use absolute terms ('always', 'never') unless the stem demands a categorical rule; then choose among remaining options.

Read the final line of the stem first (the actual question) to avoid answering the wrong thing after a long clinical vignette.

Acute coronary syndrome: ST-elevation myocardial infarction requires immediate reperfusion (primary PCI within 90 minutes of first medical contact when available); aspirin is given immediately unless contraindicated.

Diabetes diagnostic thresholds: fasting plasma glucose ≥126 mg/dL, 2-hour OGTT ≥200 mg/dL, HbA1c ≥6.5%, or random glucose ≥200 mg/dL with classic symptoms; confirmation requires a repeat or second abnormal test in asymptomatic patients.

Diabetic ketoacidosis management order: isotonic saline first, then insulin infusion, then potassium replacement once K+ is below the upper normal range but above 3.3 mEq/L; bicarbonate only for pH <6.9.

Community-acquired pneumonia severity is stratified with CURB-65 (confusion, urea >7 mmol/L, respiratory rate ≥30, blood pressure low, age ≥65); 0-1 points supports outpatient care.

Heart failure with reduced ejection fraction: guideline-directed therapy combines a renin-angiotensin system blocker (ACE inhibitor/ARB/ARNI), beta-blocker, mineralocorticoid receptor antagonist, and SGLT2 inhibitor.

Hypertensive emergency is defined by severe blood pressure elevation with target-organ damage; treatment uses titratable intravenous agents and lowers pressure gradually, not to normal within minutes.

Thyroid: primary hypothyroidism shows elevated TSH with low free T4; subclinical hypothyroidism shows elevated TSH with normal free T4.

Anemia classification uses mean corpuscular volume: microcytic suggests iron deficiency, thalassemia, or chronic disease; macrocytic suggests B12/folate deficiency, alcohol, or hypothyroidism.

Neonatal resuscitation sequence: warm, dry, stimulate, clear airway if needed, assess breathing and heart rate; positive pressure ventilation begins for apnea or heart rate <100/min.

APGAR scores are assigned at 1 and 5 minutes on five components (appearance, pulse, grimace, activity, respiration), each 0-2 points; the score does not guide ongoing resuscitation decisions.

Normal infant weight doubles by about 5 months and triples by about 12 months; birth weight is regained by 10-14 days of life.

Developmental milestones: social smile at 6 weeks, head control at 3 months, sitting without support at 6-8 months, walking at 12-15 months, two-word phrases at 18-24 months.

Acute bronchiolitis in infants is usually caused by respiratory syncytial virus; management is supportive (oxygen, hydration), and routine bronchodilators or corticosteroids are not indicated.

Pediatric dehydration is classified by percentage weight loss and clinical signs; severe dehydration with shock requires isotonic crystalloid bolus of 20 mL/kg, repeated as needed.

Kawasaki disease diagnostic criteria: fever ≥5 days plus 4 of 5 (conjunctivitis, oral changes, cervical lymphadenopathy, rash, extremity changes); treatment is IV immunoglobulin plus aspirin.

Intussusception presents in infants with intermittent colicky pain, vomiting, and currant-jelly stools; air or contrast enema is both diagnostic and therapeutic in stable patients.

Estimated date of delivery uses Naegele's rule: first day of last menstrual period plus 7 days minus 3 months (plus 1 year), assuming a 28-day regular cycle.

Normal labor: the first stage extends from onset of regular contractions to full cervical dilation; the second stage runs from full dilation to delivery of the infant.

Preeclampsia is defined as blood pressure ≥140/90 mmHg after 20 weeks with proteinuria or other organ dysfunction; magnesium sulfate is the treatment for seizure prophylaxis in severe disease.

Postpartum hemorrhage is most commonly due to uterine atony; initial management is uterine massage plus uterotonics (oxytocin first line), then escalation to surgery if refractory.

Ectopic pregnancy: a positive pregnancy test with pelvic pain and no intrauterine gestational sac on ultrasound is treated as a pregnancy of unknown location until serial beta-hCG and follow-up imaging clarify it.

Cervical cancer screening uses cytology and/or HPV testing; HPV types 16 and 18 account for the majority of cervical cancers, and vaccination reduces risk.

Combined oral contraceptives are contraindicated in migraine with aura, prior venous thromboembolism, and uncontrolled hypertension due to thrombotic risk.

Ovarian torsion presents with sudden unilateral pelvic pain and nausea; it is a surgical emergency because ovarian viability depends on time to detorsion.

Advanced trauma life support sequence: primary survey of airway with cervical spine protection, breathing, circulation with hemorrhage control, disability, and exposure.

Hemorrhagic shock is classified by blood loss; class III (30-40% loss) shows tachycardia, hypotension, and altered mental status, and requires blood products rather than crystalloid alone.

Acute appendicitis classic presentation: periumbilical pain migrating to the right lower quadrant with anorexia, nausea, and rebound tenderness at McBurney's point.

Bowel obstruction presents with colicky abdominal pain, vomiting, distension, and absent flatus; initial management is nothing by mouth, intravenous fluids, and nasogastric decompression.

Acute cholecystitis is suggested by right upper quadrant pain, fever, and a positive Murphy sign; ultrasound is the first-line imaging study.

Perforated peptic ulcer causes sudden severe epigastric pain with board-like rigidity; free air on upright chest radiograph supports the diagnosis.

Surgical wound classification: clean, clean-contaminated, contaminated, and dirty; prophylactic antibiotics are indicated for most clean-contaminated and contaminated procedures.

Postoperative fever timing: within 48 hours consider atelectasis or drug reaction; days 3-5 consider urinary or wound infection; after day 5 consider abscess or deep vein thrombosis.

Sensitivity is the proportion of truly diseased people who test positive; specificity is the proportion of truly healthy people who test negative; both are properties of the test, not the population.

Positive predictive value depends on prevalence: for the same sensitivity and specificity, PPV rises as disease prevalence rises, and falls in low-prevalence screening settings.

Relative risk is used in cohort studies; odds ratio is used in case-control studies and approximates relative risk only when the outcome is rare.

Incidence counts new cases per population at risk per time period; prevalence counts all existing cases and equals incidence multiplied by average disease duration at steady state.

Randomized controlled trials with allocation concealment and blinding provide the strongest evidence for therapeutic questions; systematic reviews of such trials rank above individual trials.

Informed consent requires capacity, adequate disclosure of risks and alternatives, and voluntariness; a patient with decision-making capacity may refuse treatment even if the refusal risks death.

Confidentiality may be breached without consent only under specific legal duties, such as mandatory reporting of certain communicable diseases or suspected child abuse.

Levels of prevention: primary prevents onset (vaccination), secondary detects early disease (screening), and tertiary limits disability from established disease (rehabilitation).