CEN Medical Emergencies: Sepsis, Anaphylaxis, DKA, Electrolytes and Withdrawal in 15 Items

The 9 topics in the CEN medical emergencies area

The July 2026 CEN outline gives Medical Emergencies 15 scored items, 10% of the 150 in Passy's arithmetic, one more than under the January 2022 outline. Renal failure moved out of this area to the genitourinary part of Genitourinary, Gynecology, and Obstetrical Emergencies. The 9 topics now listed:

The outline doesn't say which endocrine or hematologic conditions it means; the examples below are ones with clear emergency rules. Intentional overdose sits in Mental Health, and specific poisons such as carbon monoxide and cyanide in Toxicology. The clinical statements come from the 2026 Surviving Sepsis Campaign guidelines and from Merck Manual Professional Edition chapters, cited with their review dates; they are not BCEN statements.

Sepsis in the first hour: the 2026 guideline statements

The Surviving Sepsis Campaign published its 2026 adult guidelines on March 23, 2026. SCCM's guideline page lists these first-hours statements for adults. "Recommends" is a strong recommendation, "suggests" a conditional one:

The page also says sepsis is "a clinical diagnosis" that should not be ruled in or out by a single biomarker. Merck's sepsis chapter defines septic shock as sepsis needing vasopressors to keep MAP at 65 mm Hg or higher with a lactate above 2 mmol/L despite adequate fluids, and adds source control: draining abscesses, removing infected catheters where possible, and excising infected or dead tissue.

Hypovolemic and distributive shock on the CEN

Merck's shock chapter separates the two shock types this area names:

Merck also notes that anaphylactic and septic shock often have a hypovolemic component, and that hypotension is common in shock but not required: some patients are normotensive early on. Cardiogenic and obstructive shock are in the CEN cardiovascular guide, and neurogenic shock's warm, dry skin with bradycardia is in the CEN neurological guide.

Anaphylaxis: epinephrine first, then the adjuncts

Merck's anaphylaxis chapter:

• Epinephrine is "the cornerstone of treatment" and "should be given immediately." Absorption is greatest when it is given IM in the anterolateral thigh. Treatment should not be delayed for diagnostic testing
• Beta-blockers may blunt epinephrine's effect, but epinephrine should be used regardless
• Airway: stridor and wheezing unresponsive to epinephrine call for oxygen and intubation, and early intubation is advised because airway edema can progress
• Adjuncts: IV fluids for persistent hypotension, H1 (and sometimes H2) antihistamines, inhaled albuterol for bronchospasm that persists after epinephrine. Glucocorticoids have "no proven role" but may help prevent a late-phase reaction
• After the reaction: late-phase or biphasic reactions can occur hours later, typically within 4 to 6 hours for a biphasic reaction, so patients are observed in an acute care setting for several hours

To work through these first-drug decisions in exam-style items, 170 Medical Emergencies questions are planned for full CEN prep.

Endocrine emergencies: DKA, hypoglycemia and adrenal crisis

Diabetic ketoacidosis. Merck's chapter on acute diabetes complications describes nausea, vomiting, abdominal pain (especially in children), Kussmaul respirations and fruity breath. Treatment starts with volume restoration using 0.9% saline, then IV insulin "as long as serum potassium is ≥ 3.3 mEq/L." References differ slightly on the exact cutoff, so learn the rule rather than one number: a low potassium is replaced before insulin starts. The rule exists because total body potassium is depleted even when the first level looks normal or high, and insulin drives potassium into cells. Bicarbonate is not given routinely, because it can contribute to cerebral edema, mainly in children. Headache and a fluctuating level of consciousness can herald that complication.

Hypoglycemia. Merck's hypoglycemia chapter separates autonomic symptoms (sweating, tremor, palpitations, anxiety) from neuroglycopenic ones (confusion, seizures, coma), and notes that in older patients it can cause stroke-like aphasia or hemiparesis.

Adrenal crisis. Merck's adrenal insufficiency chapter says to suspect it in shock with hypotension resistant to fluids and vasopressors. When there is no time to test, hydrocortisone is given empirically, and confirmatory testing is deferred until the patient recovers.

Electrolytes: potassium and sodium rules on the CEN

Hyperkalemia. Merck's hyperkalemia chapter says an ECG should be done in patients with hyperkalemia. Early ECG changes include a longer PR interval and tall, symmetric, peaked T waves; above about 6.5 mEq/L, the QRS widens and P waves disappear. When the ECG shows loss of P waves or QRS widening, IV calcium is given with insulin and glucose. Calcium "antagonizes the effect of hyperkalemia on cardiac muscle," but its benefit lasts only 20 to 30 minutes; Merck calls it a temporizing measure while the other treatments take effect.

Hyponatremia. Merck's hyponatremia chapter warns that too-rapid correction can cause osmotic demyelination syndrome, so the rise in serum sodium over the first 24 hours is deliberately limited; check the exact limit in the reference you study with. Rules like these are the focus of planned CEN flashcards on ED thresholds, such as potassium before insulin.

Hematologic disorders and immunocompromise

Sickle cell disease. Merck's sickle cell chapter treats a painful vaso-occlusive crisis with liberal analgesia, usually opioids, and restoration of normal intravascular volume. Chest pain or difficulty breathing should raise acute chest syndrome, "the leading cause of death" in sickle cell disease, and calls for a chest radiograph and pulse oximetry.

Neutropenic fever. Merck's neutropenia chapter says the usual signs of infection may be muted in severe neutropenia, and fever may be the only sign. If fever is present, infection is presumed and immediate empiric broad-spectrum antibiotics are needed; at least 2 sets of blood cultures are drawn from every febrile patient.

Substance use and withdrawal syndromes

Opioid toxicity. Merck's opioid chapter describes respiratory depression and miotic pupils. Naloxone rapidly reverses unconsciousness and apnea in most patients, but it can precipitate acute withdrawal with agitation. Its half-life is shorter than that of some opioids, so respiratory depression can recur after long-acting opioids, and observation time depends on the drug involved. Opioid withdrawal itself brings signs of central nervous system hyperactivity and, after heroin, can begin within about 4 hours and peak at 48 to 72 hours.

Alcohol withdrawal. Merck's alcohol chapter gives the timeline: tremor, sweating and other mild symptoms usually begin within about 6 hours of stopping; withdrawal seizures generally occur 6 to 48 hours after; delirium tremens usually begins 48 to 72 hours after. Benzodiazepines are the mainstay of treatment, and IV thiamine is given to prevent Wernicke encephalopathy.

A Passy-written CEN medical emergencies practice item

This is an original practice item, not a BCEN question.

A patient with type 1 diabetes has vomiting, Kussmaul respirations and a glucose of 540 mg/dL. Saline is running. The first serum potassium is 3.0 mEq/L, and an insulin infusion is ordered. Which action comes FIRST?

• A. Start the insulin infusion as ordered
• B. Replace potassium and hold the insulin
• C. Give an IV sodium bicarbonate dose
• D. Stop the IV fluids to avoid cerebral edema

Preferred response: B. Merck gives IV insulin only "as long as serum potassium is ≥ 3.3 mEq/L" and says insulin should be withheld, and potassium given, while it is lower, because insulin drives potassium into cells and can cause life-threatening hypokalemia (A). Bicarbonate is not routine in DKA (C). Fluids restore volume and are the first treatment (D). The CEN priority questions guide explains the "rule that fixes the first action" pattern behind this item.

How to review the 15 CEN medical emergencies items

A practical plan, not a BCEN rule:

1. Make a one-line rule for each topic. Antimicrobials within the hour, epinephrine first, potassium before insulin, calcium for the heart, slow sodium correction, thiamine in alcohol withdrawal.
2. Compare the shock states side by side with the cardiovascular and neurological guides, so cool versus warm skin and fast versus slow pulse become automatic.
3. Know the guideline year. Review books printed before March 2026 can't include the 2026 sepsis guidelines and may follow the 2021 edition, so check their sepsis chapter against the 2026 statements in the table above.
4. Follow the study plan pairing. The CEN study plan pairs Medical with Environment and Toxicology in week 4.

Check your rules on the free CEN practice questions, and for short daily review, 54 Medical Emergencies flashcards are planned for full CEN prep; checkout isn't open yet.