System-Focused Emergencies on the CPEN Exam: 56 of 150 Items, Ten Body Systems

Three stem shapes cover most of what our bank holds in this domain. Recognize the shape from the options and you know which detail to hunt for in the stem.

What the outline lists. Foreign body; Congenital conditions (stenosis, malacia, cystic fibrosis); Upper airway: infections (croup, epiglottitis); trauma (inhalation injuries, tracheal disruption); Lower airway: infections (bronchiolitis, pneumonia); reactive airway disease/asthma; trauma (pneumothorax, hemothorax, pulmonary contusion); Respiratory failure and/or arrest; Oxygen administration (low-flow, high-flow); Airway adjuncts (tracheostomy, endotracheal tube, supraglottic). Seven sub-topics, tied with cardiovascular and neurological for the most of any system, and the whole ladder from a foreign body to an airway adjunct.

How it is asked. The respiratory stem gives you a child in a posture or a sound that is present or missing, and the options are either two conditions and two actions or four rungs of the oxygen ladder. The classic pairs are croup against epiglottitis (a barking cough and stridor in one, drooling, a tripod posture and a toxic look in the other), bronchiolitis against asthma (age and a first episode against a recurrent one), and distress against failure (work of breathing with a normal appearance against work of breathing with a child who is drowsy and quiet). The trauma items are the cleanest of the set: hypotension plus absent breath sounds on one side is a tension pneumothorax on the clinical picture, and the stem says prior to any diagnostic imaging because that phrase is the whole question.

On the oxygen ladder the item asks for the next rung, not the top: low-flow, then high-flow, then noninvasive support, then the tube for exhaustion or apnea. The distractor is the rung two steps up.

What the outline lists. Infections; Congenital heart defects; Rhythm disturbances; Shock; Cardiac arrest; Circulatory support (vascular access, ECMO, LVAD); Trauma (tamponade, blunt cardiac injury). Seven sub-topics; with respiratory, this is the resuscitation spine of the domain.

How it is asked. Two shapes dominate. The mechanism stem describes a maneuver and asks what it does: a knee-to-chest position during a hypercyanotic spell, and four options that all use the right vocabulary (systemic resistance, pulmonary resistance, shunt, oxygen demand). Only one is the physiology; the other three are the same words rearranged. The sequence stem says unstable and hands you the steps of synchronized cardioversion, or a small chest where the pads overlap, and asks for the immediate priority or the placement that fits.

Shock items in this system lean on one distinction: compensated (tachycardia and poor perfusion with a blood pressure still in range) against decompensated (hypotension or a change in mental status). A bradycardia that follows a long tachycardia is the stem's way of saying the arrest is next.

What the outline lists. Infections; Congenital conditions (hydrocephalus, AVM); Headache, migraine, and tumor; Shunt dysfunction; Seizure; Stroke; Trauma (TBI, spinal cord injury). Seven sub-topics; seizure, stroke and trauma carry the items our bank holds.

How it is asked. The neurological stem is nearly always a four-actions-one-moment item. A child arrives seizing with audible secretions and cyanosis and the options are a drug, the airway, a glucose, a scan: the word first makes it the airway. An infant seizes with altered mental status and the item asks which concurrent check finds a reversible cause: the bedside glucose, before the drug and before the imaging. Stroke follows the same pattern. A child with acute hemiparesis, and the options are a noncontrast CT, an MRI, an anticoagulant, a transfer; the stem says first, so it is the CT that excludes a bleed, and the transfer to a pediatric neuroscience center is the disposition item that follows in a separate stem.

Head trauma adds one twist: the stem makes the child hypotensive, then asks which agent manages intracranial pressure. Two options lower the pressure inside the skull; only one does it without dropping the blood pressure further, and the stem's hypotensive is the differentiator.

What the outline lists. Foreign body (button battery, magnets); Infections (gastroenteritis, appendicitis, pancreatitis); Obstructions (pyloric stenosis, intussusception, volvulus, constipation); Nutrition (failure to thrive, formula intolerance, obesity, TPN); Chronic conditions (IBD, GERD, congenital); Trauma (liver, spleen, bowel injury). Six sub-topics, and the obstruction line is where the four-conditions-one-finding shape lives.

How it is asked. The vomiting infant is the model item for the whole domain. Four diagnoses in the options; in the stem, an age and a vomit. Projectile and not bilious, in a hungry infant of a few weeks with a firm epigastric mass: pyloric stenosis. Bilious, at any age: malrotation with volvulus until proven otherwise. A toddler whose parents describe episodes of crying earlier and who is now quiet and sleepy, with stable vital signs: intussusception, and the test the item wants first is the ultrasound. Each stem contains exactly one word that separates the pair: nonbilious, bilious, episodes.

Foreign bodies get their own stems. A swallowed shiny coin is a button battery until the films say otherwise, so the item asks which series rules the battery out (neck, chest and abdomen, not one view). A single magnet plus any second metal object is two magnets, and the two-objects-touching film is asking for removal, not observation.

What the outline lists. Infections (UTI, STI, PID, epididymitis, pyelonephritis); GU emergencies (testicular torsion, priapism, phimosis, ovarian torsion); OB emergencies (ectopic pregnancy, emergent delivery); Trauma (abruption, straddle injury, renal contusion). Four sub-topics, and the outline puts ectopic pregnancy and emergent delivery on a pediatric emergency exam.

How it is asked. Torsion is the anchor. The stem is an adolescent with severe, intermittent pain, an ultrasound result, and four dispositions. The item is testing whether one reassuring line in the report closes the question: an enlarged ovary with peripheral follicles and preserved Doppler flow still earns the gynecology consult, because intermittent torsion untwists between images and the history outranks the flow. Testicular torsion carries the same shape with a time element in the stem; the differentiator is how long the pain has been present, and the option to rule out is the one that waits for imaging the child does not have time for.

The infection line (UTI, STI, PID, epididymitis, pyelonephritis) tends to appear as four diagnoses with an age and a sexual history as the discriminators, which means the adolescent interview matters: the pregnancy question is fair in any abdominal-pain stem about an adolescent, because the outline says so.

What the outline lists. Foreign body; Infections (peritonsillar abscess, mastoiditis, periorbital cellulitis); Hemorrhage; Trauma (dental injury, facial fracture, globe rupture). Four sub-topics, but this system produces some of the most distinctive stems on the exam, because each has one abnormal shape at its center.

How it is asked. Blunt trauma to the eye, and the finding that mandates stopping the examination: a teardrop-shaped pupil, which means a ruptured globe, a rigid shield and no further pressure on the eye. Epistaxis that anterior packing did not stop, with blood pooling in the posterior oropharynx: the item wants the posterior device, and the distractor is repeating the anterior one. A permanent incisor avulsed some minutes ago and reimplantation is not possible: the item is about the storage medium that keeps the ligament alive (milk or a balanced salt solution; never water, never dry). A fractured incisor whose fragment nobody can find: the fragment is in the airway until a chest film says it is not.

What the outline lists. Infections (osteomyelitis, septic arthritis); Congenital conditions (osteogenesis imperfecta, muscular dystrophy, spina bifida); Trauma (fractures, amputations, compartment syndrome). Three sub-topics; compartment syndrome and the open fracture are where the bank concentrates.

How it is asked. Compartment syndrome is a clinical diagnosis, and the item is built to see whether you know that. The stem gives you a forearm fracture, severe pain with passive stretch, paresthesias, and then a compartment pressure reading that is not dramatic. The options split into trust the number and trust the examination; the examination wins, and the reading in the stem is a decoy. A second version gives a child back in the department hours after casting with pain, swelling and dusky fingers, and asks for the cause: the circumferential cast, not expected swelling, not inadequate analgesia.

The open fracture is a timing item. The child is going to the operating room later; the question is when the first antibiotic dose is given, and the options are after cultures, on admission, before surgery and now, in the department. Every delay option is a distractor.

What the outline lists. Infections (cellulitis, abscess); Rash (hives, petechiae, infestations); Trauma (foreign body, avulsions, lacerations, degloving). Three sub-topics, and the rash line is deliberately mixed: hives sit beside petechiae and infestations.

How it is asked. The procedural item: a school-age child needs incision and drainage of a large, painful abscess, and the options are four levels of pain control. Cross off topical anesthetic is enough; the key is procedural sedation, and the stem's large and painful are the reasons. The disposition item: a child on a new anticonvulsant develops fever, a targetoid rash and erosions on the lips and conjunctiva. The mucosal involvement is the discriminator that moves the answer from a dermatology follow-up to a burn center transfer.

The rash line is a sorting exercise. Put hives, petechiae and infestations in one option list and the item is asking which of the three is not a skin problem at all: petechiae with a fever belong to the sepsis and bleeding stems in other domains, and the option that treats them as a rash goes first.

What the outline lists. Hematology (sickle cell disease, bleeding/clotting disorders); Oncology (fever and neutropenia, tumor lysis syndrome). Two sub-topics on paper, but the oncology half generates some of the hardest sequence items in our bank.

How it is asked. Sickle cell: an adolescent in a vaso-occlusive crisis with chest pain and a normal oxygen saturation, and the intervention that reduces the risk of acute chest syndrome. The normal saturation is there to strike the oxygen option; the key is incentive spirometry. Fever and neutropenia: the antibiotic is the priority, sooner when the child is unstable, and when peripheral access fails the item wants the antibiotic through an intraosseous line rather than another attempt at a vein. A related stem asks which febrile neutropenic patient is the safest for outpatient management, and the high-risk features (leukemia, infancy, a central line, abdominal pain) are the strikes.

Tumor lysis is a laboratory pattern (high potassium, high phosphate, high uric acid, low calcium) and one counterintuitive item: a low calcium with no seizures, no tetany, no arrhythmia, where the item keys observation rather than replacement. Hyperkalemia with ECG change is written as a three-verb sort: calcium to stabilize the membrane, insulin with dextrose and albuterol to shift potassium, binders and dialysis to remove it. The item asks which verb the moment needs.

What the outline lists. Congenital disorders (CAH, inborn errors of metabolism); Acquired disorders (diabetes). Two sub-topics, the shortest entry in the domain; the items our bank holds here are sequences and one arithmetic check.

How it is asked. Diabetic ketoacidosis is written as an order-of-operations item: the potassium is known before the insulin starts, and the option that starts the insulin on arrival is the one to cross off. The neonate with symptomatic hypoglycemia produces the one calculation stem our bank holds in this domain: a weight, a weight-based dose and a dextrose concentration, and the item wants the volume. The arithmetic is the easy part; the concentration is the trap, because the adult one appears as an option, and a separate stem asks why concentrated dextrose or calcium chloride needs a large-bore or central line (tissue necrosis).

Congenital adrenal hyperplasia and the inborn errors arrive as the neonate who was well and is now vomiting, dehydrated and shock-like, and the item asks which finding is the concerning one. The related clue from the assessment domain applies here: a fast respiratory rate with clear lungs and no work of breathing is a metabolic acidosis, not a lung problem, and the option that treats it as one is the one to rule out.