Emergency Medicine

01 The Emergency Medicine Approach

Emergency medicine is the only specialty defined not by an organ system or patient demographic but by acuity and undifferentiated presentation. The ED physician sees every chief complaint, from cardiac arrest to laceration repair, and must risk-stratify within minutes. The central question is never "what is the complete diagnosis?" but rather "does this patient have a life-threatening condition that I must identify and treat right now?"

Triage — Emergency Severity Index (ESI)

ESI is the standard 5-level triage system used in US emergency departments. It combines acuity with expected resource utilization to prioritize patient flow.

Primary Survey — ABCDE

The primary survey is performed on every critically ill or injured patient. It is a systematic, sequential assessment that identifies and treats life threats in the order they will kill the patient fastest.

Secondary Survey

Performed only after the primary survey is complete and life threats are addressed. This is the comprehensive head-to-toe physical exam: HEENT (pupil response, TMs, oropharynx), neck (JVD, tracheal deviation, c-spine tenderness), chest (heart sounds, lung fields), abdomen (tenderness, guarding, rigidity, peritoneal signs), pelvis (stability), extremities (pulses, deformity, compartments), neuro (cranial nerves, strength, sensation, reflexes, cerebellar), skin (rashes, wounds, track marks), and a detailed history (SAMPLE: Signs/symptoms, Allergies, Medications, Past medical history, Last meal, Events preceding).

02 Resuscitation Fundamentals

ACLS — Cardiac Arrest Algorithms

The 2020 AHA Guidelines define two pathways based on initial rhythm:

The H's and T's — reversible causes of cardiac arrest: Hypovolemia, Hypoxia, Hydrogen ion (acidosis), Hypo/hyperkalemia, Hypothermia, Tension pneumothorax, Tamponade (cardiac), Toxins, Thrombosis (coronary/pulmonary). High-quality CPR is the single most important intervention: rate 100–120/min, depth 2–2.4 inches (5–6 cm), full chest recoil, minimize interruptions (< 10 sec for rhythm checks).

Airway Management Hierarchy

Airway interventions escalate in invasiveness: positioning (head tilt–chin lift, jaw thrust in trauma) → basic adjuncts (OPA in unconscious without gag, NPA if gag intact) → bag-valve-mask (BVM) → supraglottic airway (LMA, King tube — rescue device or prehospital) → endotracheal intubation (RSI is the ED standard) → surgical airway (cricothyrotomy — "can't intubate, can't oxygenate" scenario).

Shock Recognition & Classification

Hemorrhagic Shock Staging (ATLS)

03 Key Terminology & Abbreviations

Emergency medicine uses a dense layer of abbreviations across triage, resuscitation, trauma, and disposition. A comprehensive list is provided in Section 50. Below are the foundational terms every EM reference requires:

04 Acute Coronary Syndromes CV

ACS is a spectrum of acute myocardial ischemia ranging from unstable angina (UA) to non-ST-elevation MI (NSTEMI) to ST-elevation MI (STEMI). ACS is the leading cause of death worldwide and the most common high-acuity cardiac presentation in the ED. The critical ED task is rapid ECG interpretation (< 10 minutes from arrival) to identify STEMI, which requires emergent reperfusion.

ACS Spectrum

STEMI Localization by ECG

Initial ED Management of ACS

MONA (Morphine, Oxygen, Nitroglycerin, Aspirin) is the classic mnemonic but has evolved: Aspirin 325 mg chewed (non-enteric coated, immediate), Nitroglycerin 0.4 mg SL q5min × 3 (hold if SBP < 90, RV infarct, or PDE5 inhibitor within 24–48 hrs), heparin (UFH 60 U/kg bolus max 4000 U, then 12 U/kg/hr infusion; or enoxaparin 1 mg/kg SQ), P2Y12 inhibitor (clopidogrel 600 mg load or ticagrelor 180 mg load — check with interventional cardiologist before cath as some prefer to load in the lab). Oxygen only if SpO2 < 94%. Morphine with caution — may increase mortality in NSTEMI.

05 Acute Heart Failure & Pulmonary Edema CV

Acute decompensated heart failure (ADHF) presents as sudden or worsening dyspnea, orthopnea, and hypoxia from pulmonary venous congestion. The ED must rapidly distinguish cardiogenic pulmonary edema from pneumonia, COPD, and PE. BNP > 400 pg/mL (or NT-proBNP > 900 pg/mL) strongly supports HF; < 100 (< 300) makes it unlikely. CXR shows cephalization of vessels, Kerley B lines, bilateral pleural effusions, and perihilar edema ("butterfly" or "bat wing" pattern).

Acute Management

The mainstay is preload and afterload reduction, NOT fluid boluses. Nitroglycerin 400 mcg SL, then IV infusion 10–200 mcg/min (titrate to symptom relief and SBP > 100). Furosemide (Lasix) 40–80 mg IV (if on chronic diuretics, give ≥ home dose IV). BiPAP (CPAP 10–12 cmH2O or BiPAP 10/5) dramatically reduces work of breathing and intubation rates — start immediately in moderate-to-severe respiratory distress. For flash pulmonary edema with hypertension: aggressive nitroglycerin (high-dose bolus 2 mg IV followed by infusion) is highly effective.

06 Aortic Dissection & Aortic Emergencies CV

Aortic dissection is a tear in the aortic intima allowing blood to enter the media, creating a false lumen. Mortality increases 1–2% per hour if untreated. Classic presentation: sudden-onset "tearing" or "ripping" chest/back pain that is maximal at onset, radiating to the back (descending) or anterior chest (ascending). Risk factors: uncontrolled hypertension, Marfan syndrome, bicuspid aortic valve, prior cardiac surgery, cocaine use.

Stanford Classification

ED Management

Anti-impulse therapy: target HR < 60 bpm and SBP 100–120 mmHg. Start IV esmolol (500 mcg/kg bolus, then 50–200 mcg/kg/min) or labetalol (20 mg IV bolus, then 1–2 mg/min infusion). Beta-blocker FIRST — do not give vasodilators (nitroprusside, nicardipine) without beta-blockade, as reflex tachycardia increases aortic shear stress. Add nitroprusside (0.25–10 mcg/kg/min) only after HR is controlled. CTA chest/abdomen/pelvis is the gold-standard diagnostic study (sensitivity > 95%).

07 Cardiac Arrest & Post-Arrest Care CV

Cardiac arrest survival depends on the chain of survival: early recognition, early CPR, early defibrillation, and advanced resuscitation. Out-of-hospital cardiac arrest (OHCA) survival to discharge averages 10–12% nationally; in-hospital cardiac arrest (IHCA) survival is approximately 25%. Shockable rhythms (VF/pVT) carry significantly better prognosis than non-shockable (asystole/PEA).

Post-Arrest Care

After ROSC, immediate priorities: 12-lead ECG (emergent cath if STEMI or high suspicion of coronary occlusion), targeted temperature management (TTM) — the TTM2 trial (2021) found no benefit of 33°C vs. 36°C, and current guidelines recommend maintaining temperature ≤ 37.5°C and actively preventing fever. Hemodynamic optimization: MAP > 65 mmHg (vasopressors as needed), avoid hypotension and hypoxia (target SpO2 94–98%, avoid hyperoxia). Neuroprognostication should be delayed ≥ 72 hours after rewarming — never withdraw care based on exam alone within the first 72 hours.

08 Arrhythmia Management CV

Tachyarrhythmias

Bradyarrhythmias

Symptomatic bradycardia (HR < 50 with hypotension, AMS, chest pain, or acute HF): Atropine 1 mg IV q3–5 min (max 3 mg) — will not work in Mobitz II or third-degree block (infranodal). If atropine fails: transcutaneous pacing (start at 60 mA, increase until capture, then add 10 mA safety margin; sedate the patient with fentanyl/midazolam). Dopamine infusion (5–20 mcg/kg/min) or epinephrine infusion (2–10 mcg/min) as bridge to transvenous pacing.

09 Hypertensive Emergencies CV

A hypertensive emergency is severely elevated BP (often > 180/120) with acute end-organ damage: encephalopathy, acute stroke, aortic dissection, acute MI, pulmonary edema, eclampsia, acute renal failure, or retinal hemorrhage. Hypertensive urgency is severely elevated BP without end-organ damage — manage with oral agents and outpatient follow-up; aggressive IV reduction is not indicated and may cause harm.

Treatment by End-Organ

10 Pulmonary Embolism CV

PE is the third leading cause of cardiovascular death. The ED challenge is identifying PE among the high volume of patients with chest pain and dyspnea while avoiding unnecessary CT angiography. Risk stratification begins with clinical probability assessment.

Wells Score for PE

Score ≤4: PE unlikely → check D-dimer (if < 500 ng/mL, PE excluded). Score >4: PE likely → proceed to CTA. PERC rule: if clinical gestalt is "PE unlikely" AND all 8 PERC criteria are negative (age < 50, HR < 100, SpO2 ≥ 95%, no hemoptysis, no estrogen use, no prior DVT/PE, no unilateral leg swelling, no surgery/trauma requiring hospitalization in past 4 weeks), D-dimer is unnecessary — PE is effectively excluded.

Management by Severity

11 Cardiac Tamponade CV

Pericardial fluid accumulation compressing the heart, impairing diastolic filling. The physiologic consequence is obstructive shock — reduced cardiac output despite adequate volume. Causes: malignancy (most common cause of large effusions), uremia, post-MI (Dressler syndrome), trauma (hemopericardium), aortic dissection (rupture into pericardium), infection (TB, viral). Beck's triad: hypotension, muffled heart sounds, JVD. Pulsus paradoxus > 10 mmHg (SBP drop with inspiration) is a key sign. Electrical alternans on ECG (beat-to-beat alternation in QRS amplitude) is specific but not sensitive.

Bedside echo is the diagnostic study of choice — pericardial effusion with RV diastolic collapse (earliest sign of tamponade physiology) and RA systolic collapse. Treatment: emergent pericardiocentesis (subxiphoid approach, ultrasound-guided, advance 18-gauge needle at 30–45° toward the left shoulder). Even removing 20–50 mL can dramatically improve hemodynamics. IV fluid bolus (500–1000 mL) as temporizing measure to increase preload. Traumatic tamponade often requires emergent thoracotomy rather than pericardiocentesis.

12 Acute Asthma & Status Asthmaticus Resp

Asthma exacerbation severity drives treatment intensity. Mild-moderate: speaks in sentences, RR < 30, SpO2 ≥ 90%, PEF > 50% predicted. Severe: speaks in words, RR > 30, accessory muscle use, SpO2 < 90%, PEF < 50%. Status asthmaticus: severe exacerbation refractory to initial bronchodilator therapy, representing a life-threatening emergency.

Stepwise ED Management

First-line: continuous nebulized albuterol (10–15 mg/hr) + ipratropium 0.5 mg nebulized q20min × 3. Corticosteroids early: prednisone 60 mg PO or methylprednisolone 125 mg IV (onset 4–6 hrs, but give early). Magnesium sulfate 2 g IV over 20 min for severe exacerbation (NNT = 4 for preventing admission). Epinephrine 0.3–0.5 mg IM for impending respiratory failure. For patients failing NIV: intubation is dangerous in status asthmaticus (post-intubation hypotension from air trapping — use ketamine for induction, permissive hypercapnia strategy, low RR 8–10, long expiratory time, I:E 1:4–1:5).

13 COPD Exacerbation Resp

Acute worsening of respiratory symptoms (dyspnea, cough, sputum volume/purulence) beyond normal day-to-day variation requiring a change in medication. Most common triggers: viral/bacterial infection (60–80%), air pollution, PE, and pneumothorax. COPD patients live with chronic CO2 retention; their respiratory drive may be hypoxic rather than hypercarbic. Target SpO2 88–92% — excessive oxygen can worsen hypercapnia through the Haldane effect and V/Q mismatch redistribution.

Treatment

Bronchodilators: albuterol + ipratropium nebulized. Systemic corticosteroids: prednisone 40 mg PO × 5 days (or methylprednisolone IV). Antibiotics if purulent sputum or requiring mechanical ventilation: azithromycin 500 mg × 1 day then 250 mg × 4 days, or doxycycline 100 mg BID, or amoxicillin-clavulanate. BiPAP (IPAP 10–15 cmH2O, EPAP 5 cmH2O) is first-line for COPD exacerbation with respiratory acidosis (pH < 7.35, pCO2 > 45) — reduces intubation rate by 60% and mortality by 50% (Cochrane review).

14 Pneumonia (CAP, HAP, Aspiration) Resp

Community-acquired pneumonia (CAP) is the most common infectious cause of death in the US. Typical pathogens: S. pneumoniae (most common), H. influenzae, M. catarrhalis. Atypical: Mycoplasma, Chlamydophila, Legionella. Viral: influenza, RSV, SARS-CoV-2.

Severity & Disposition — CURB-65

Score 0–1: outpatient. 2: consider short hospitalization. 3–5: admit, 4–5 consider ICU.

Empiric Antibiotic Regimens

15 Pneumothorax Resp

Types

16 Acute Respiratory Failure & Mechanical Ventilation Resp

Type I (hypoxemic): PaO2 < 60 mmHg on room air. Caused by V/Q mismatch, shunt, diffusion impairment (pneumonia, ARDS, PE, pulmonary edema). Type II (hypercapnic): PaCO2 > 50 mmHg with respiratory acidosis. Caused by alveolar hypoventilation (COPD, neuromuscular disease, drug overdose, obesity hypoventilation).

Initial Ventilator Settings (Post-Intubation)

ARDSNet protocol (ARMA trial, NEJM 2000): low tidal volume ventilation (6 mL/kg IBW) reduces mortality by 22% in ARDS. Target plateau pressure < 30 cmH2O. Permissive hypercapnia acceptable (pH ≥ 7.20). Prone positioning for 16+ hrs/day in moderate-severe ARDS (P/F < 150) reduces mortality (PROSEVA trial).

17 Acute Ischemic Stroke Neuro

Stroke is a time-critical emergency — "time is brain." Approximately 1.9 million neurons are lost per minute during a large-vessel occlusion. The ED role is rapid recognition (NIHSS assessment), immediate CT to exclude hemorrhage, and initiation of reperfusion therapy within the time window.

Reperfusion Windows

18 Hemorrhagic Stroke (ICH & SAH) Neuro

Intracerebral Hemorrhage (ICH)

Spontaneous ICH accounts for 10–15% of all strokes but carries 40–50% 30-day mortality. Most common cause: hypertensive arteriopathy (deep structures: basal ganglia, thalamus, pons, cerebellum). Other causes: cerebral amyloid angiopathy (lobar hemorrhages in elderly), anticoagulant use, vascular malformations, hemorrhagic conversion of ischemic stroke. CT head shows hyperdense (bright white) intraparenchymal blood.

Management: aggressive BP control (SBP target < 140 mmHg within 1 hr — INTERACT2; use nicardipine infusion). Reverse anticoagulation immediately if applicable (warfarin → 4-factor PCC + vitamin K 10 mg IV; DOAC → idarucizumab for dabigatran, andexanet alfa for Xa inhibitors, or 4-factor PCC if specific reversal unavailable). Neurosurgery consult for cerebellar hemorrhage > 3 cm (may need emergent evacuation) or hydrocephalus (EVD placement).

Subarachnoid Hemorrhage (SAH)

85% from ruptured cerebral aneurysm. Classic presentation: "worst headache of my life," sudden onset, maximal intensity at onset ("thunderclap headache"), with or without neck stiffness, photophobia, vomiting, syncope, or coma. CT head sensitivity: 95–100% within 6 hours, drops to ~85% at 24 hours and further with time. If CT is negative and clinical suspicion remains: lumbar puncture looking for xanthochromia (yellow discoloration of CSF from bilirubin, most reliable at 12+ hours after onset) or elevated RBCs that do not clear with sequential tubes.

After SAH diagnosis: CTA to locate the aneurysm, neurosurgery/neurointerventional consult for definitive treatment (endovascular coiling preferred over surgical clipping for most aneurysms per ISAT trial). Nimodipine 60 mg PO q4h × 21 days (prevents vasospasm-related delayed cerebral ischemia — the only medication proven to improve outcomes in SAH). Keep SBP < 160 until aneurysm secured.

19 Status Epilepticus Neuro

Defined as continuous seizure activity lasting ≥ 5 minutes or ≥ 2 seizures without return to baseline. A true time-critical neurological emergency — prolonged seizure activity causes excitotoxic neuronal injury, rhabdomyolysis, hyperthermia, and systemic acidosis. Mortality approaches 20% and increases with duration of seizure.

Stepwise Treatment Protocol

20 Meningitis & Encephalitis Neuro

Bacterial meningitis carries 20–25% mortality even with treatment and requires emergent antibiotics — do not delay for LP or imaging. Classic triad: fever, nuchal rigidity, altered mental status (present in only ~44% of bacterial meningitis). Kernig's sign (pain with knee extension when hip flexed) and Brudzinski's sign (involuntary hip flexion with passive neck flexion) have low sensitivity but moderate specificity.

Empiric Antibiotics by Age

Dexamethasone 0.15 mg/kg IV q6h × 4 days — give with or just before the first antibiotic dose. Reduces mortality and neurological sequelae in pneumococcal meningitis (de Gans et al., NEJM 2002).

LP Interpretation

21 Spinal Cord Compression Neuro

Acute spinal cord compression is a neurosurgical/oncologic emergency. Most common cause: metastatic disease (breast, lung, prostate account for >50%). Other causes: epidural abscess, disk herniation, epidural hematoma. Presentation: progressive back pain (often the first symptom, present for weeks before neurological deficits), bilateral leg weakness, sensory level, urinary retention or incontinence. A sensory level (loss of sensation below a dermatomal line) is highly specific for cord compression.

Diagnosis: MRI of the entire spine (urgent, within hours). Treatment: dexamethasone 10 mg IV bolus followed by 4 mg IV q6h (reduces cord edema). Urgent neurosurgery or radiation oncology consult for surgical decompression vs. radiation therapy. Functional outcomes correlate directly with neurological status at the time of treatment — ambulatory patients have >80% chance of remaining ambulatory; paraplegic patients have <10% chance of walking again.

22 Traumatic Brain Injury Trauma

Glasgow Coma Scale (GCS)

GCS 13–15: mild TBI; 9–12: moderate; 3–8: severe (intubate for airway protection). The motor score is the single most predictive component.

Herniation Syndromes

Signs of herniation: unilateral fixed, dilated pupil (CN III compression from uncal herniation), Cushing's triad (hypertension, bradycardia, irregular respirations — a late and ominous sign), decerebrate posturing. Emergency management of herniation: elevate HOB 30°, mannitol 1–1.5 g/kg IV (osmotic diuresis) or hypertonic saline 3% 250 mL or 23.4% 30 mL IV over 15 min, hyperventilation to pCO2 30–35 mmHg (temporizing only — causes vasoconstriction reducing ICP but also reducing cerebral perfusion), emergent neurosurgery consult for decompressive craniectomy.

Canadian CT Head Rule

For minor head injury (GCS 13–15) — CT is required if ANY of the following are present:

23 Cervical Spine Injury Trauma

The ED must identify or confidently exclude c-spine injury in every trauma patient. Clinical decision rules allow safe clearance without imaging in low-risk patients.

NEXUS Criteria & Canadian C-Spine Rule

NEXUS: C-spine imaging NOT needed if ALL 5 criteria met: no posterior midline tenderness, no focal neurological deficit, normal alertness, no intoxication, no distracting injury. Canadian C-Spine Rule (more sensitive than NEXUS): Step 1 — any high-risk factor mandating imaging? (age ≥ 65, dangerous mechanism, paresthesias in extremities). If yes → image. Step 2 — any low-risk factor allowing safe ROM assessment? (simple rear-end MVC, sitting in ED, ambulatory at any time, delayed onset neck pain, no midline tenderness). If yes → Step 3: can patient actively rotate neck 45° left and right? If yes → no imaging needed.

High-Yield C-Spine Injuries

24 Chest Trauma Trauma

Chest trauma is responsible for 25% of trauma deaths. Most life-threatening injuries can be identified on primary survey and CXR. The "deadly dozen" includes tension PTX, open PTX, massive hemothorax, flail chest, cardiac tamponade, and tracheobronchial disruption (identified during primary survey), plus aortic injury, diaphragmatic rupture, esophageal perforation, pulmonary contusion, myocardial contusion, and simple PTX/hemothorax (identified during secondary survey).

Key Chest Trauma Entities

25 Abdominal Trauma & FAST Exam Trauma

Blunt abdominal trauma: spleen is the most commonly injured solid organ (left-sided mechanism), followed by liver (right-sided). In penetrating trauma, liver is most commonly injured (stab wounds), followed by small bowel (gunshot wounds). The FAST exam (Focused Assessment with Sonography for Trauma) is performed in the resuscitation bay to detect free fluid (blood) in four windows: RUQ (Morison's pouch — most sensitive for free fluid), LUQ (splenorenal recess), suprapubic (pelvis), and subxiphoid (pericardial). FAST is 85–95% sensitive for significant hemoperitoneum.

Management Algorithm

Hemodynamically unstable + positive FAST: emergent exploratory laparotomy. Hemodynamically stable + positive FAST or high-energy mechanism: CT abdomen/pelvis with IV contrast for injury grading. FAST negative + stable: serial exams; CT if clinical concern persists (FAST misses retroperitoneal, hollow viscus, and diaphragm injuries).

Splenic Injury Grading (AAST)

26 Pelvic Fracture & Hemorrhage Trauma

Unstable pelvic fractures (open-book, vertical shear) can cause massive hemorrhage from the presacral venous plexus and pelvic arterial branches, with blood loss exceeding 3–5 liters. Mechanism: high-energy (MVC, motorcycle, pedestrian struck, fall from height). Exam: pelvic instability on gentle AP compression (perform ONCE — repeated rocking worsens hemorrhage). Do NOT perform a rocking exam if instability is obvious or if a pelvic binder is already in place.

Management: pelvic binder (commercially available or bedsheet wrapped tightly at the level of the greater trochanters) to reduce pelvic volume and tamponade hemorrhage. Activate MTP. If hemodynamically unstable despite binder + MTP: angioembolization (if CTA shows arterial blush) or preperitoneal pelvic packing (direct surgical packing of the pelvic space). REBOA (Resuscitative Endovascular Balloon Occlusion of the Aorta) in Zone III (infrarenal) is an emerging temporizing measure.

27 Orthopedic Emergencies Trauma

Open Fractures — Gustilo-Anderson Classification

All open fractures need: tetanus prophylaxis, IV antibiotics within 1 hour, irrigation and debridement in the OR (ideally within 6–24 hours), and orthopedic consult.

Compartment Syndrome

Elevated pressure within a closed fascial compartment compromising perfusion. Most common after tibial fractures, crush injuries, and reperfusion after vascular repair. The 6 P's (Pain out of proportion, Pain with passive stretch — the earliest and most reliable sign, Paresthesias, Pressure/tense compartment, Pallor, Pulselessness — a LATE finding). Normal compartment pressure: 0–8 mmHg. Delta pressure (diastolic BP minus compartment pressure) < 30 mmHg = fasciotomy indicated. Treatment: emergent fasciotomy. Delay beyond 6–8 hours causes irreversible muscle necrosis and Volkmann's contracture.

High-Risk Dislocations

28 Acute Abdomen & Imaging Approach GI

The "acute abdomen" is not a diagnosis but a clinical presentation: acute abdominal pain requiring urgent evaluation and often intervention. The ED approach centers on identifying surgical emergencies (appendicitis, perforated viscus, bowel obstruction, mesenteric ischemia, ruptured AAA, ectopic pregnancy) and time-critical medical conditions (DKA, ACS with epigastric pain, adrenal crisis).

Abdominal Pain Differential by Location

29 Appendicitis & Cholecystitis GI

Appendicitis

Lifetime incidence 7–8%. Classic presentation: periumbilical pain migrating to RLQ (visceral → somatic pain as inflammation reaches the parietal peritoneum), anorexia, nausea/vomiting, low-grade fever. McBurney's point tenderness (1/3 of the distance from ASIS to umbilicus). Special signs: Rovsing's (RLQ pain with LLQ palpation), psoas sign (pain with right hip extension — retrocecal appendix), obturator sign (pain with internal rotation of flexed right hip — pelvic appendix).

Diagnosis: CT abdomen/pelvis with IV contrast is the gold standard (sensitivity 98%). Ultrasound is first-line in pregnant patients and children. Alvarado (MANTRELS) score: Migration, Anorexia, Nausea, Tenderness (RLQ), Rebound, Elevation of temperature, Leukocytosis, Shift to left; score ≥7 strongly suggests appendicitis. Treatment: appendectomy (laparoscopic preferred). Antibiotics alone are an option for uncomplicated appendicitis in selected patients (CODA trial), though recurrence rate is ~30% at 2 years.

Acute Cholecystitis

Gallstone impacted in the cystic duct causing gallbladder inflammation. Presentation: persistent RUQ pain (>4–6 hrs, distinguishing it from biliary colic which resolves), fever, Murphy's sign (inspiratory arrest during RUQ palpation). Diagnosis: RUQ ultrasound showing gallstones + gallbladder wall thickening > 3 mm + pericholecystic fluid + sonographic Murphy's sign. HIDA scan if ultrasound equivocal (non-filling of gallbladder = cystic duct obstruction). Treatment: NPO, IV fluids, antibiotics (piperacillin-tazobactam or ceftriaxone + metronidazole), surgical consult for cholecystectomy (ideally within 72 hours of admission).

30 Bowel Obstruction & Mesenteric Ischemia GI

Small Bowel Obstruction (SBO)

Causes: adhesions from prior surgery (75%), hernias (15%), malignancy, Crohn's disease, volvulus. Presentation: crampy abdominal pain, nausea/vomiting (earlier and more profuse in proximal obstruction), obstipation/constipation, distension. X-ray: dilated small bowel loops (> 3 cm), air-fluid levels, decompressed colon. CT with IV and oral contrast is the definitive study — identifies transition point, closed-loop obstruction, and signs of strangulation (mesenteric haziness, wall thickening, reduced enhancement, pneumatosis).

Treatment: NGT decompression (Salem sump), IV fluids, NPO, electrolyte correction. Surgery if: signs of strangulation/ischemia, closed-loop obstruction, peritonitis, complete obstruction without improvement in 48–72 hours, or incarcerated hernia.

Mesenteric Ischemia

Acute mesenteric ischemia is a surgical emergency with 60–80% mortality. The hallmark: "pain out of proportion to exam" — severe abdominal pain with a benign abdominal examination (early). As bowel infarction develops: peritoneal signs, bloody stool, lactic acidosis. Causes: SMA embolism (~50%), SMA thrombosis (~25%), NOMI (~15%), mesenteric venous thrombosis (~10%). CTA is diagnostic (filling defects, bowel wall changes). Treatment: heparin, emergent surgical embolectomy or revascularization, bowel resection if necrotic; second-look laparotomy at 24–48 hours.

31 GI Hemorrhage GI

Upper GI Bleeding (UGIB)

Source proximal to the ligament of Treitz. Presentation: hematemesis (bright red or coffee-ground emesis), melena (black tarry stool), or hematochezia (if massive). Most common causes: peptic ulcer disease (35–50%), esophageal/gastric varices (10–20%), Mallory-Weiss tear, erosive gastritis/esophagitis. Glasgow-Blatchford Score (GBS): BUN, hemoglobin, SBP, HR, melena, syncope, hepatic disease, heart failure. Score 0–1: safe for outpatient management. Score ≥6: high risk, needs intervention.

Management: 2 large-bore IVs, fluid resuscitation, type and cross. Restrictive transfusion (Hgb target ≥ 7 g/dL, ≥ 8 if active CAD per Villanueva et al., NEJM 2013). PPI: pantoprazole 80 mg IV bolus, then 8 mg/hr infusion for suspected ulcer bleeding. EGD within 24 hours (12 hours if high-risk features). Variceal bleed: octreotide 50 mcg IV bolus then 50 mcg/hr, antibiotics (ceftriaxone 1 g IV), urgent EGD for band ligation. If uncontrolled variceal bleeding: Blakemore/Minnesota tube or TIPS.

Lower GI Bleeding (LGIB)

Source distal to ligament of Treitz. Presentation: hematochezia (bright red blood per rectum). Common causes: diverticular bleeding (most common cause of massive LGIB), hemorrhoids, AV malformations, colitis (IBD, ischemic, infectious), colorectal cancer. Most LGIB stops spontaneously (80–85%). Hemodynamically significant LGIB: resuscitate, CTA if unstable (identifies active extravasation/source), colonoscopy within 24 hours if stabilized.

32 Pancreatitis GI

Diagnosis requires 2 of 3: (1) characteristic abdominal pain (epigastric, radiating to back, worse after eating), (2) serum lipase ≥ 3× upper limit of normal, (3) imaging findings (CT showing pancreatic edema/necrosis/peripancreatic stranding). Lipase is preferred over amylase (more sensitive and specific, stays elevated longer). Most common causes: gallstones (40%) and alcohol (30%). Other: hypertriglyceridemia (> 1000 mg/dL), post-ERCP, medications (valproic acid, azathioprine), autoimmune.

Management: aggressive IV fluid resuscitation (LR preferred, 1.5 mL/kg/hr for 24 hrs per WATERFALL trial — though subsequent evidence favors moderate resuscitation), pain control (IV opioids, NSAIDs), early enteral nutrition (within 24 hrs if tolerated — no need to wait for pain resolution). CT is NOT needed at presentation unless the diagnosis is uncertain or complications are suspected. CT should be obtained at 48–72 hours if not improving to assess for necrosis. Ranson's criteria and BISAP score predict severity. Gallstone pancreatitis requires cholecystectomy during the same admission (to prevent recurrence).

33 Sepsis & Septic Shock Infxn

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection. The Sepsis-3 (2016) definition requires suspected infection + acute change in SOFA score ≥ 2 points. qSOFA (quick bedside screen): RR ≥ 22, altered mentation, SBP ≤ 100. Two or more qSOFA criteria should prompt further evaluation. Septic shock: sepsis + vasopressor requirement to maintain MAP ≥ 65 + lactate > 2 mmol/L despite adequate fluid resuscitation. Septic shock mortality: 30–40%.

Hour-1 Bundle (Surviving Sepsis Campaign 2021)

34 Skin & Soft Tissue Infections Infxn

Spectrum of SSTIs

35 Toxidrome Recognition & General Approach Tox

A toxidrome is a constellation of signs and symptoms that suggests a particular class of poisoning. Recognizing the toxidrome narrows the differential immediately and guides empiric treatment before confirmatory labs return.

36 Acetaminophen & Salicylate Toxicity Tox

Acetaminophen (APAP) Overdose

The most common cause of acute liver failure in the US. Toxic dose: > 150 mg/kg or > 7.5 g in adults. Metabolism: at therapeutic doses, APAP is metabolized via glucuronidation/sulfation. In overdose, these pathways saturate, and CYP2E1 converts APAP to NAPQI, a toxic metabolite that depletes glutathione and causes hepatocellular necrosis. Stages: (1) 0–24 hrs: nausea, vomiting, normal labs; (2) 24–72 hrs: RUQ pain, rising AST/ALT; (3) 72–96 hrs: peak hepatotoxicity (AST/ALT > 10,000, coagulopathy, renal failure, encephalopathy); (4) Recovery or death.

Rumack-Matthew Nomogram: Plot the 4-hour post-ingestion APAP level on the nomogram. Treatment line starts at 150 mcg/mL at 4 hours. If level is above the line: N-acetylcysteine (NAC) — IV protocol: 150 mg/kg over 1 hour, then 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours (total 21 hours). Oral: 140 mg/kg load, then 70 mg/kg q4h × 17 additional doses. NAC is most effective within 8 hours but should be given at ANY time if clinical concern for toxicity. Always check an APAP level on every overdose patient regardless of reported ingestion.

Salicylate Toxicity

Acute ingestion > 150 mg/kg is toxic; > 500 mg/kg is potentially lethal. Chronic salicylism occurs at lower levels in elderly patients on aspirin. Pathophysiology: uncouples oxidative phosphorylation, stimulates respiratory center, causes metabolic acidosis. Classic ABG: mixed respiratory alkalosis + metabolic acidosis (early: respiratory alkalosis from central stimulation; late: AG metabolic acidosis predominates). Symptoms: tinnitus, nausea, vomiting, hyperpnea, diaphoresis, altered mental status, seizures.

Treatment: sodium bicarbonate infusion (150 mEq in 1 L D5W at 1.5–2× maintenance) targeting urine pH 7.5–8.0 (alkalinize the urine to trap salicylate in its ionized form for renal excretion). Monitor K+ closely (hypokalemia prevents urine alkalinization). Hemodialysis indications: salicylate level > 90 mg/dL (acute) or > 60 mg/dL (chronic), altered mental status, renal failure, pulmonary edema, refractory acidosis. Do NOT intubate salicylate patients unless absolutely necessary — their compensatory hyperventilation is maintaining acid-base balance; matching their minute ventilation post-intubation is extremely difficult, and loss of respiratory compensation leads to rapid acidemia, cardiovascular collapse, and death.

37 Alcohol Withdrawal & Sedative-Hypnotic Toxicity Tox

Alcohol withdrawal is a spectrum from mild (tremor, anxiety, insomnia, 6–24 hrs after last drink) to moderate (hallucinations, 12–48 hrs) to seizures (12–48 hrs) to delirium tremens (48–96 hrs: confusion, agitation, autonomic instability, hyperthermia, seizures — mortality 5–15% without treatment, up to 35% untreated). Use the CIWA-Ar score (Clinical Institute Withdrawal Assessment for Alcohol, Revised) to guide benzodiazepine dosing: 10 parameters scored 0–7 each (max 67). CIWA < 10: mild, monitoring. 10–18: moderate, treat. > 18: severe, aggressive treatment.

Treatment: benzodiazepines are the mainstay. Symptom-triggered dosing (CIWA-guided) is preferred over fixed-schedule. Diazepam 10–20 mg IV q10–15 min (active metabolites provide smooth taper) or lorazepam 2–4 mg IV q15–30 min (preferred in liver failure — no active metabolites). For refractory DTs: phenobarbital 130–260 mg IV, propofol infusion, or dexmedetomidine adjunct. IV thiamine 500 mg before glucose (prevent Wernicke's encephalopathy), IV magnesium, folate, multivitamins.

38 Anaphylaxis Tox

Anaphylaxis is a severe, life-threatening systemic allergic reaction involving ≥2 organ systems (skin/mucosal, respiratory, cardiovascular, GI). Triggers: foods (peanuts, tree nuts, shellfish), medications (antibiotics, NSAIDs), insect stings, latex. Can occur within seconds to minutes of exposure. Presentation: urticaria/angioedema (90%), bronchospasm/stridor, hypotension/tachycardia, nausea/vomiting/cramping.

Epinephrine is the ONLY first-line treatment: 0.3–0.5 mg IM (1:1000 concentration) in the anterolateral thigh. May repeat q5–15 min. IV epinephrine (1:10,000, 0.1 mg boluses or infusion 1–10 mcg/min) for refractory shock. Adjuncts: IV fluids (1–2 L bolus for hypotension), albuterol nebulized (bronchospasm), diphenhydramine 50 mg IV (H1 blocker), famotidine 20 mg IV (H2 blocker), methylprednisolone 125 mg IV (prevents biphasic reaction — occurs in 5–20% at 1–72 hours). Observe 4–6 hours post-treatment; prescribe EpiPen and refer to allergist on discharge.

39 Environmental Emergencies Tox

Heat Emergencies

Hypothermia

Drowning

Leading cause of unintentional death in children 1–4 years. Primary insult is hypoxia from water aspiration and laryngospasm. All drowning patients who are symptomatic or have any submersion > 1 minute require ED evaluation. Treatment is supportive: supplemental O2, positive-pressure ventilation if needed, intubation for respiratory failure. Monitor for ARDS (may develop 6–24 hours post-submersion). Hypothermia from cold-water submersion may be neuroprotective and is not a reason to terminate resuscitation early. Cervical spine precautions if diving mechanism.

40 Pediatric Emergencies Peds

Febrile Seizures

Most common seizure type in children (2–5% of children aged 6 months to 5 years). Simple febrile seizure: generalized, < 15 minutes, does not recur within 24 hours. Complex: focal, > 15 minutes, or recurrent within 24 hours. Simple febrile seizures are benign — no increased epilepsy risk, no need for LP or EEG in well-appearing children ≥ 12 months with first simple febrile seizure. Treat the fever and reassure parents.

Croup (Laryngotracheobronchitis)

Viral (parainfluenza most common), ages 6 months to 3 years. Presentation: barking "seal-like" cough, inspiratory stridor, hoarseness, worse at night. "Steeple sign" on AP neck X-ray (subglottic narrowing). Treatment: mild (stridor at rest) → dexamethasone 0.6 mg/kg PO/IM (single dose); moderate-severe → nebulized racemic epinephrine (0.5 mL of 2.25% in 3 mL NS) + dexamethasone. Observe ≥ 3–4 hours after racemic epi for rebound.

Intussusception

Telescoping of proximal bowel into distal segment. Peak incidence: 6–36 months. Most common cause of bowel obstruction in infants. Classic triad: colicky abdominal pain (intermittent, severe, with drawing up of legs), vomiting, and "currant jelly" stool (bloody mucus — a LATE sign). Palpable "sausage-shaped" mass in RUQ. Diagnosis: ultrasound showing "target sign" or "pseudokidney sign." Treatment: air-contrast or hydrostatic enema (both diagnostic and therapeutic, 80–95% success for reduction). Surgery if enema fails, peritonitis, or perforation.

Non-Accidental Trauma (NAT)

Suspect when: injury inconsistent with developmental stage, changing history, delay in seeking care, multiple injuries at different stages of healing, specific injury patterns (posterior rib fractures, metaphyseal "corner" or "bucket handle" fractures, retinal hemorrhages, patterned bruising/burns). Mandatory reporting is required in all US states when NAT is suspected. Workup: skeletal survey (children < 2 years), head CT, ophthalmologic exam, labs (CBC, CMP, coags, lipase, UA for hematuria).

41 Obstetric Emergencies OB

Ectopic Pregnancy

Implantation outside the uterine cavity (95% in fallopian tube). Risk factors: prior ectopic, PID, tubal surgery, IUD. Presentation: abdominal/pelvic pain + vaginal bleeding + positive pregnancy test. Ruptured ectopic causes acute abdomen with hemoperitoneal shock. Diagnosis: transvaginal ultrasound (absence of IUP with beta-hCG above discriminatory zone, typically ≥1500–2000 mIU/mL) + adnexal mass or free fluid. Treatment: hemodynamically stable + unruptured → methotrexate (50 mg/m² IM single dose) if criteria met (no fetal cardiac activity, mass < 4 cm, beta-hCG < 5000). Ruptured or hemodynamically unstable → emergent salpingectomy.

Eclampsia & Severe Preeclampsia

Preeclampsia: new-onset hypertension (≥140/90 after 20 weeks) + proteinuria or end-organ dysfunction. Severe features: SBP ≥ 160 or DBP ≥ 110, platelets < 100K, elevated liver enzymes (2× normal), renal insufficiency (Cr > 1.1), pulmonary edema, headache/visual disturbances. Eclampsia: seizures in preeclamptic patient. Treatment: magnesium sulfate 4–6 g IV over 20 min (seizure prophylaxis and treatment), then 1–2 g/hr maintenance; antihypertensives (IV labetalol or hydralazine); definitive treatment is delivery.

Perimortem Cesarean Delivery

If a pregnant patient (fundus at or above the umbilicus, roughly ≥ 20 weeks) suffers cardiac arrest and does not have ROSC within 4 minutes of CPR, perimortem C-section should be performed at the bedside. The goal is delivery within 5 minutes of arrest (the "4-minute rule" — decision at 4 min, delivery by 5 min). This is performed to improve maternal resuscitation (relieving aortocaval compression) as much as for fetal survival. The procedure is performed at the patient's current location — do not move to the OR.

42 Psychiatric Emergencies Psych

Suicidal Patient

Risk assessment: SAD PERSONS (Sex, Age, Depression, Previous attempt, Ethanol abuse, Rational thinking loss, Social supports lacking, Organized plan, No spouse, Sickness). High-risk features: specific plan, access to means (especially firearms), active psychosis, recent discharge from psychiatric facility, male > 45, history of prior attempts. Columbia Suicide Severity Rating Scale (C-SSRS) is the standard structured assessment. All patients with active suicidal ideation with plan or intent require psychiatric evaluation and safety precautions (1:1 observation, search for sharps, remove cords/ligatures from room).

Acute Agitation Management

43 Geriatric Emergencies Geri

Elderly patients (≥ 65 years) present atypically: MI without chest pain (dyspnea, confusion), sepsis without fever (hypothermia is a worse prognostic sign), UTI presenting as altered mental status, appendicitis without peritoneal signs. Falls are the leading cause of injury-related death in the elderly. Always consider: medication effects (polypharmacy, anticoagulants), baseline cognitive function (delirium vs. dementia), occult fractures, and disposition challenges (can the patient safely return home?).

Occult Fractures in the Elderly

44 Airway Management & RSI Procedures

Rapid Sequence Intubation (RSI)

RSI is the standard of care for emergency intubation in the ED. It involves simultaneous administration of a sedative and neuromuscular blocking agent to facilitate endotracheal intubation while minimizing aspiration risk.

Surgical Airway (Cricothyrotomy)

Indicated when intubation and ventilation both fail ("can't intubate, can't oxygenate"). Technique: identify cricothyroid membrane (between thyroid and cricoid cartilages), vertical skin incision, horizontal stab through membrane, insert bougie, railroad a 6.0 cuffed ETT or tracheostomy tube over bougie. Contraindicated in children < 8–10 years (needle cricothyrotomy with jet ventilation instead due to small anatomy).

Non-Invasive Ventilation & High-Flow Nasal Cannula

45 Vascular Access & Chest Procedures Procedures

Vascular Access Hierarchy

Chest Tube Insertion

Indications: pneumothorax (traumatic, large spontaneous), hemothorax, empyema, large symptomatic pleural effusion. Technique: safe triangle (bordered by anterior border of latissimus dorsi, lateral border of pectoralis major, line of the 5th intercostal space, apex of the axilla). Position: 4th–5th ICS, anterior to mid-axillary line. Incise skin, blunt dissect through intercostal muscles ABOVE the rib (neurovascular bundle runs below each rib), enter pleural space, finger sweep, insert tube directed posteriorly-superiorly for air or posteriorly-inferiorly for fluid. Tube size: 28–36 Fr for hemothorax, 20–24 Fr for pneumothorax. Connect to closed drainage system (Pleur-Evac) with 20 cmH2O suction. Confirm with CXR.

Needle Decompression

For tension pneumothorax when clinical diagnosis is made (do NOT wait for imaging). Site: 5th ICS, anterior axillary line (preferred over the traditional 2nd ICS midclavicular line due to greater chest wall thickness at the 2nd ICS). Use a 14-gauge angiocatheter, at least 8 cm long. Insert perpendicular to chest wall, above the rib. Rush of air confirms decompression. This is a temporizing measure — follow immediately with chest tube.

46 Wound Management & Procedural Sedation Procedures

Laceration Repair

Assessment: mechanism, contamination, depth (tendon/nerve/vessel/joint involvement?), foreign body, neurovascular status distal to wound, time since injury. Anesthesia: local infiltration with lidocaine 1% (max 4.5 mg/kg without epi, 7 mg/kg with epi) or bupivacaine 0.25% (longer duration). LET gel (lidocaine-epinephrine-tetracaine) for pediatric face/scalp lacerations. Closure: simple interrupted sutures (nylon for skin, absorbable for deep layers), running sutures (rapid closure of clean linear wounds), deep dermal sutures (Vicryl for dead space closure), wound adhesive (2-octyl cyanoacrylate / Dermabond) for clean superficial lacerations, staples for scalp. Suture removal timing: face 3–5 days, scalp 7–10 days, trunk 7–10 days, extremities 10–14 days, joints 14 days.

Procedural Sedation

47 Reduction Techniques & Bedside Ultrasound Procedures

Shoulder Dislocation Reduction

Multiple techniques exist; selection depends on patient body habitus, cooperation, and provider experience. External rotation method: patient supine, elbow at 90°, slowly externally rotate the arm (adducted) until relocates. Cunningham technique: patient seated, provider massages biceps, deltoid, and trapezius muscles (no traction). Stimson technique: patient prone, arm hanging off stretcher with 5–10 lb weight; gravity reduces. Traction-countertraction: sheet around patient's chest for countertraction, steady traction on the arm. Pre-reduction X-ray to confirm dislocation and rule out fracture. Post-reduction: neurovascular exam (check axillary nerve), X-ray to confirm reduction, sling × 2–3 weeks, orthopedic follow-up.

Emergency Bedside Ultrasound Applications

48 Clinical Decision Rules & Scoring Systems

49 Medications Master Table Meds

RSI & Airway Medications

Vasopressors & Inotropes

Antidotes

Analgesics & Sedatives

Common EM Antibiotics

50 Abbreviations Master List

General & Resuscitation

Diagnoses

Procedures & Imaging

Medications & Labs

Scoring & Decision Rules

51 Disposition Decision Framework & References

Disposition Decision Framework

Every ED patient requires a disposition decision: discharge home, observe (observation unit), admit to the floor, or admit to the ICU. This decision integrates acuity, diagnosis, clinical trajectory, and patient factors.

Consolidated References