Comprehensive Osteopathic Medical Licensing Examination (COMLEX-USA) Surgery, Emergency Medicine, and Musculoskeletal Care Syllabus

What is the lethal triad of trauma that worsens hemorrhage?

Hypothermia, acidosis, and coagulopathy — a self-perpetuating cycle that increases mortality and is addressed by damage control resuscitation.

What two life threats does eFAST/chest exam look for that present as obstructive shock in trauma, and how are they distinguished?

Tension pneumothorax (hyperresonance, absent breath sounds, tracheal deviation away — treat with needle decompression/chest tube) and cardiac tamponade (Beck's triad: hypotension, distended neck veins, muffled heart sounds — treat with pericardiocentesis).

What ECG rhythms are shockable versus non-shockable in cardiac arrest?

Shockable: ventricular fibrillation and pulseless ventricular tachycardia (defibrillate). Non-shockable: pulseless electrical activity (PEA) and asystole (CPR + epinephrine, treat reversible causes).

List the reversible causes of cardiac arrest — the Hs and Ts.

Hs: Hypoxia, Hypovolemia, Hydrogen ion (acidosis), Hypo/Hyperkalemia, Hypothermia. Ts: Tension pneumothorax, Tamponade (cardiac), Toxins, Thrombosis (pulmonary), Thrombosis (coronary).

What is the dose and route of epinephrine in adult cardiac arrest?

1 mg of 1:10,000 IV/IO every 3-5 minutes during CPR.

What is the classic ECG finding and immediate management of a STEMI?

ST-segment elevation in contiguous leads (with reciprocal depression). Management: aspirin, anticoagulation, and emergent reperfusion — primary PCI within 90 minutes, or fibrinolytics if PCI is unavailable within 120 minutes.

What is the antidote for acetaminophen overdose, and what nomogram guides treatment?

N-acetylcysteine (NAC); the Rumack-Matthew nomogram guides treatment based on serum acetaminophen level plotted against time since ingestion (≥4 hours).

Match these toxidromes to their antidotes: opioids, benzodiazepines, organophosphates, and beta-blockers.

Opioids → naloxone; benzodiazepines → flumazenil; organophosphates (cholinergic) → atropine + pralidoxime; beta-blockers → glucagon.

What is the antidote for ethylene glycol/methanol poisoning and the classic acid-base disturbance?

Fomepizole (alcohol dehydrogenase inhibitor), or ethanol; consider hemodialysis. They cause a high anion-gap metabolic acidosis (ethylene glycol also causes calcium oxalate crystalluria/renal failure).

How is carbon monoxide poisoning diagnosed and treated, and why is standard pulse oximetry misleading?

Diagnose with carboxyhemoglobin level via co-oximetry. Treat with 100% oxygen (hyperbaric oxygen for severe cases). Standard pulse oximetry is falsely normal because it cannot distinguish carboxyhemoglobin from oxyhemoglobin.

Describe the classification of burn depth: superficial, partial-thickness, and full-thickness.

Superficial (1st degree): epidermis only, red and painful, no blisters. Partial-thickness (2nd degree): into dermis, blisters, painful. Full-thickness (3rd degree): entire dermis, white/leathery/insensate. Fourth-degree extends to muscle/bone.

State the Parkland formula for burn fluid resuscitation.

4 mL × body weight (kg) × % total body surface area burned = total lactated Ringer's over 24 hours; give half in the first 8 hours (from time of burn) and the remaining half over the next 16 hours.

What are the tetanus prophylaxis guidelines for a contaminated (tetanus-prone) wound?

If <3 prior doses or unknown: give Tdap/Td AND tetanus immune globulin (TIG). If fully vaccinated: give Td/Tdap only if the last dose was >5 years ago; TIG is not needed.

What is the Salter-Harris classification used for, and what does the mnemonic SALTR represent?

It classifies pediatric physeal (growth plate) fractures. SALTR: I = Slipped (through physis), II = Above (metaphysis, most common), III = Lower (epiphysis), IV = Through/Transverse (epiphysis + metaphysis), V = Ruined/cRush (compression, worst prognosis).

What complication must be excluded in any fracture or crush injury with severe pain out of proportion, and what is the diagnostic pressure threshold?

Acute compartment syndrome. The 6 Ps: Pain (out of proportion, worse with passive stretch), Pallor, Paresthesia, Paralysis, Pulselessness (late), Poikilothermia. Compartment pressure >30 mmHg (or delta <30) indicates emergent fasciotomy.

Which carpal bone is most commonly fractured, and what is the major complication?

The scaphoid (snuffbox tenderness). Risk of avascular necrosis because its blood supply enters distally (retrograde flow). Immobilize even with a normal initial X-ray.

In which direction do shoulder dislocations most commonly occur, and what nerve is at risk?

Anterior dislocation is most common; the axillary nerve is at risk (test sensation over the deltoid 'regimental badge' area and deltoid function).

What is a hip fracture's classic presentation, and why is femoral neck fracture concerning?

The affected leg is shortened and externally rotated. Femoral neck (intracapsular) fractures risk avascular necrosis of the femoral head due to disruption of the medial femoral circumflex artery.

What is the Ottawa Ankle Rules' purpose, and when is an ankle X-ray indicated?

They reduce unnecessary radiographs. X-ray the ankle if there is pain in the malleolar zone PLUS bony tenderness at the posterior edge/tip of either malleolus OR inability to bear weight (4 steps) both immediately and in the ED.

What is the most commonly injured ligament of the ankle, and the typical mechanism?

The anterior talofibular ligament (ATFL), injured by inversion (plantarflexion + inversion) of the ankle.

Describe the unhappy triad of the knee.

Injury to the anterior cruciate ligament (ACL), medial collateral ligament (MCL), and medial meniscus, classically from a lateral blow to a planted knee.

What physical exam tests assess ACL integrity, and what symptom suggests a meniscal tear?

Lachman test (most sensitive) and anterior drawer test assess the ACL. A meniscal tear causes joint-line tenderness, locking/catching, and a positive McMurray test.

Differentiate the joint fluid and presentation of osteoarthritis versus rheumatoid arthritis.

OA: non-inflammatory (WBC <2,000), asymmetric, weight-bearing joints, worse with use/end of day, brief morning stiffness (<30 min), Heberden/Bouchard nodes, osteophytes. RA: inflammatory (WBC 2,000-50,000), symmetric small joints (MCP/PIP, spares DIP), morning stiffness >1 hour, pannus/erosions, positive RF/anti-CCP.

How do you distinguish gout from pseudogout on joint aspirate crystal analysis?

Gout: needle-shaped, negatively birefringent monosodium urate crystals (yellow when parallel to the polarizer). Pseudogout (CPPD): rhomboid-shaped, positively birefringent calcium pyrophosphate crystals (blue when parallel).

What synovial fluid WBC count and findings suggest septic arthritis, and what is the most common organism?

Synovial WBC typically >50,000 (often >100,000) with neutrophil predominance and positive Gram stain/culture. Staphylococcus aureus is the most common organism; in young sexually active adults consider Neisseria gonorrhoeae.

What is cauda equina syndrome, and what are its red-flag features requiring emergent imaging/surgery?

Compression of the lumbosacral nerve roots. Red flags: saddle anesthesia, bowel/bladder dysfunction (urinary retention with overflow incontinence), bilateral leg weakness/sciatica, and decreased rectal tone. Requires emergent MRI and decompression.

List the red-flag features in low back pain that warrant further workup rather than conservative care.

Age >50 or <18, history of cancer, unexplained weight loss, fever/IV drug use (infection), trauma, night pain/pain at rest, progressive neurologic deficit, saddle anesthesia, and bowel/bladder dysfunction.

What nerve roots are tested by the straight leg raise, and what does a positive test indicate?

The straight leg raise tests the L5-S1 roots (sciatic nerve). Reproduction of radicular pain down the leg at 30-70 degrees of elevation suggests lumbar disc herniation with nerve root irritation.

What is the classic triad of nephrolithiasis, the most common stone type, and first-line imaging?

Acute colicky flank pain radiating to the groin, hematuria, and nausea/vomiting. Calcium oxalate is the most common stone. Non-contrast helical CT of the abdomen/pelvis is the imaging of choice.

Differentiate testicular torsion from epididymitis, including the key physical exam sign.

Torsion: sudden severe pain, high-riding testis with horizontal lie, absent cremasteric reflex, NO pain relief with elevation (negative Prehn sign) — a surgical emergency (detorse within ~6 hours). Epididymitis: gradual onset, fever, pain relief with elevation (positive Prehn sign), intact cremasteric reflex.

What is the next step for a man with painless gross hematuria, and what malignancy must be excluded?

Cystoscopy plus CT urography to evaluate for urothelial (bladder) carcinoma; painless gross hematuria is bladder cancer until proven otherwise. Smoking is the major risk factor.

How do you distinguish a peritonsillar abscess from simple pharyngitis, and what is the treatment?

Peritonsillar abscess: severe unilateral sore throat, 'hot potato'/muffled voice, trismus, uvular deviation to the contralateral side. Treatment is needle aspiration or incision and drainage plus antibiotics.

What is the most common cause of unilateral epistaxis and the usual anterior source, and the initial management?

Anterior bleeds from Kiesselbach's plexus (Little's area) are most common. Initial management: direct pressure by pinching the soft part of the nose for 10-15 minutes with the patient leaning forward; escalate to topical vasoconstrictors, cautery, or packing.

Differentiate acute angle-closure glaucoma from other red eye, and why is it an emergency?

Angle-closure glaucoma: acute severe eye pain, headache, nausea/vomiting, a fixed mid-dilated pupil, halos around lights, and a hard 'rock' eye with markedly elevated intraocular pressure. It is a sight-threatening emergency requiring immediate IOP-lowering therapy.

How does central retinal artery occlusion present on funduscopy, and how is it managed?

Sudden painless monocular vision loss with a pale retina and a 'cherry-red spot' at the macula. It is an ophthalmic emergency (a stroke equivalent) — attempt ocular massage, IOP-lowering measures, and urgent ophthalmology/stroke workup.

What is the classic triad of a ruptured abdominal aortic aneurysm, and the size threshold for elective repair?

Triad: hypotension, pulsatile abdominal mass, and abdominal/flank/back pain. Elective repair is generally indicated at a diameter ≥5.5 cm, rapid expansion (>0.5 cm/6 months), or when symptomatic.

Differentiate acute arterial occlusion (the 6 Ps) from chronic peripheral arterial disease.

Acute arterial occlusion (often embolic): sudden onset of the 6 Ps — Pain, Pallor, Pulselessness, Paresthesia, Paralysis, Poikilothermia. Chronic PAD: gradual intermittent claudication, diminished pulses, hair loss, and a low ankle-brachial index (ABI <0.9).

What are the classic chest X-ray findings of aortic dissection, and the diagnostic imaging of choice?

Widened mediastinum (and possibly a left pleural effusion). CT angiography of the chest is the diagnostic test of choice (TEE if unstable). Type A (ascending) requires surgery; Type B (descending) is often managed medically with blood-pressure control.

Describe the four stages of general anesthesia (Guedel's stages).

Stage I: analgesia/induction (awake to loss of consciousness). Stage II: excitement/delirium (irregular breathing, risk of laryngospasm). Stage III: surgical anesthesia (regular breathing, target plane). Stage IV: medullary depression/overdose (apnea, cardiovascular collapse).

What is malignant hyperthermia, its triggers, and its treatment?

A rare autosomal dominant pharmacogenetic disorder (ryanodine receptor mutation) triggered by volatile anesthetics and succinylcholine. Presents with hypercarbia, rigidity (often masseter), tachycardia, and rising temperature. Treatment: stop the trigger, give dantrolene, and provide cooling/supportive care.

Define the ASA Physical Status Classification levels I through V.

ASA I: normal healthy patient. II: mild systemic disease. III: severe systemic disease (not incapacitating). IV: severe systemic disease that is a constant threat to life. V: moribund, not expected to survive without the operation. (An 'E' suffix denotes emergency.)