CCRN Multisystem Emergencies Beyond Sepsis: Malignant Hyperthermia, Burns, Rhabdomyolysis, Temperature Extremes and Poisoning

Sepsis gets most of the attention in study guides, but the Multisystem category also holds the patients who come to the ICU because something outside the body went wrong: an anesthetic, a fire, a hot day, a bottle of pills, cold water. These emergencies share a pattern, a short window in which the first nursing action matters more than any later detail. This review covers them from MHAUS, the MSD Manual chapters and the peer-reviewed review named in each section, all opened on October 28, 2026. It gives no drug doses; MHAUS publishes its dantrolene dosing on its crisis page, and your protocol and the prescriber's orders govern the rest.

What the CCRN Multisystem list includes beyond sepsis

Multisystem is 16% of the Adult CCRN test plan for exams on and after November 12, 2025. Its 22 listed problems include acid-base, fluid and electrolyte imbalances, anoxic injury, burns, rhabdomyolysis, submersion injuries, thermoregulation and toxic ingestions, inhalations and exposures, alongside sepsis, shock states, SIRS and multi-organ dysfunction. Its testable nursing actions include recognizing and managing toxin and drug exposures, risk-factor recognition and management of malignant hyperthermia, targeted temperature management, temperature monitoring and regulation devices, ECMO, intra-abdominal pressure monitoring, organ donation, and end-of-life and palliative care.

Elsewhere in Passy's CCRN guides: the sepsis and shock guide covers sepsis and shock states, the ABG and acid-base guide the acid-base problems, the GI, renal and skin review intra-abdominal pressure, and the ethics and advocacy guide organ donation duties. This guide doesn't cover fluid and electrolyte imbalances, healthcare-associated infections, pain, sleep disruption, maternal and fetal emergencies, obesity-related complications or transplant comorbidity.

Malignant hyperthermia: the four first steps

MHAUS describes the malignant hyperthermia crisis as a chain reaction in the skeletal muscle of susceptible people, triggered by volatile anesthetics and succinylcholine. Its general signs are a rising heart rate, greatly increased metabolism, muscle rigidity and fever, with muscle breakdown and acidosis. Two points from the MHAUS FAQ matter for ICU nurses:

• It isn't only in the operating room. The hour after surgery, including the recovery room, is also a critical time, and a crisis can occur wherever triggering agents are used, intensive care units included.
• Susceptibility runs in families. It is inherited in an autosomal dominant pattern, so children and siblings of a susceptible person usually have a 50% chance of carrying it, and carriers may not know until they or a relative react during anesthesia. That is the "risk-factor recognition" half of the test plan's action.

MHAUS's crisis management page lists four things to do as soon as possible:

1. Stop the triggers. Notify the surgeon to halt the procedure and discontinue volatile agents and succinylcholine; if surgery must continue, anesthesia continues with non-triggering IV agents.
2. Get dantrolene and the MH cart, and call for help. MHAUS also offers a 24-hour hotline, 1-800-644-9737.
3. Hyperventilate with 100% oxygen at high flow to flush volatile agents and lower the end-tidal CO2.
4. Give IV dantrolene rapidly, repeated until end-tidal CO2, rigidity and heart rate improve. MHAUS calls dantrolene the only currently accepted specific treatment.

Then MHAUS adds supportive steps: cool if core temperature is above 39 °C, or lower if it is rising fast, and stop cooling below 38 °C; treat hyperkalemia; treat dysrhythmias with standard drugs but avoid calcium channel blockers; keep urine output above 1 mL/kg/h; and monitor core temperature, urine output, end-tidal CO2, blood gases, potassium, CK, urine myoglobin and coagulation. A stable patient is transferred to a recovery unit or ICU for at least 24 hours.

For the nurse, the signs MHAUS uses to judge the response to dantrolene, end-tidal CO2, rigidity and heart rate, are also the ones to watch: an end-tidal CO2 that keeps climbing although ventilation has been increased, with tachycardia and rigidity, in a patient who received a trigger. The free CCRN set includes a malignant hyperthermia scenario, and after these steps you can work the post-anesthesia rigidity item in the free CCRN set.

Malignant hyperthermia or heatstroke? Same heat, different fixes

MSD lists the organ damage heatstroke can cause: rhabdomyolysis, liver and kidney injury, ARDS, cardiac dysfunction, hyperkalemia, hypoglycemia and DIC, so patients are observed in an ICU for multi-organ dysfunction after cooling. To keep similar-looking emergencies apart under time pressure, Redemption challenges planned for CCRN prep bring back the questions you missed.

Hypothermia, rewarming and targeted temperature management

Accidental hypothermia. MSD's chapter (full review August 2026) defines hypothermia as a core temperature of 35 °C or below and makes several bedside points:

• Measure the core. Esophageal and epitympanic probes are the most accurate; rectal and bladder temperatures lag behind during rewarming, and oral and temporal thermometers are generally unreliable for the diagnosis.
• Expect hidden hypovolemia. Cold diuresis and fluid leakage cause hypovolemia that vasoconstriction can mask, so shock or arrest can appear during rewarming as the vessels dilate, which MSD calls rewarming collapse.
• Match rewarming to severity. Mild hypothermia is treated with passive rewarming in a warm environment with insulating blankets; severe hypothermia needs active external and core rewarming, up to extracorporeal blood rewarming.
• Keep going in arrest. MSD's CPR chapter says that if cardiac arrest is thought to be due to hypothermia, CPR continues until the body is rewarmed to 34 °C.

Targeted temperature management. The test plan lists TTM as a nursing action. MSD's CPR chapter (full review December 2024) says it is recommended for adults who remain unresponsive after return of spontaneous circulation, with a constant temperature selected and maintained between 32 and 37.5 °C and started as soon as circulation returns, using external devices or internal methods. The American Heart Association updated its post-cardiac arrest guideline in 2025, and a 2026 review in Intensive Care Medicine by Lavinio and colleagues reports that it recommends maintaining a temperature between 32 and 37.5 °C for at least 36 hours, while the 2025 European Resuscitation Council and European Society of Intensive Care Medicine guidelines emphasize active fever prevention below 37.5 °C. Your unit's protocol sets the target and duration you use.

Burns: airway, fluids from the time of injury, and circumferential eschar

MSD's burns chapter (full review September 2024) starts where every trauma starts, with airway, breathing and circulation, and adds burn-specific steps:

• Airway. Consider early intubation with respiratory symptoms, carbonaceous sputum, perioral burns, singed nasal hairs, or confinement in a burning space. Smoke inhalation is treated with 100% oxygen.
• Size. Only partial-thickness and full-thickness burns count toward the percentage of total body surface area (TBSA), estimated in adults by the rule of nines; for small scattered burns, the patient's whole open hand is about 1%.
• Fluids. MSD's summary says burns over 20% TBSA require fluid resuscitation, while its treatment section gives IV fluids to patients in shock or with partial- and full-thickness burns over 10% TBSA; your protocol sets the threshold. Without shock, the Parkland formula estimates the first 24 hours: 4 mL/kg × % TBSA of lactated Ringer's, half in the first 8 hours after the burn, not after arrival, and the rest over the next 16. The formula is only a starting point; the rate is adjusted to urine output, with a goal of 0.5 mL/kg/h in adults.
• Eschar. A circumferential eschar can strangle a limb or, around the chest or neck, limit ventilation, and may need escharotomy, ideally with burn center input.
• Heat loss and pain. Large volumes of cool fluid and exposed skin cause hypothermia, and opioids for burn pain are given IV.

Worked example (fictional Passy case; arithmetic is Passy's). An 80-kg man with 30% TBSA partial- and full-thickness burns, no shock, was burned at 14:00 and reaches the ICU at 16:00.

• 24-hour estimate: 4 × 80 × 30 = 9,600 mL.
• First half: 4,800 mL is due by 22:00, eight hours after the injury. Two hours have already passed with no fluid, so the remaining 4,800 mL runs over six hours: 800 mL/h.
• Second half: 4,800 mL over the next 16 hours, 300 mL/h.
• Urine target: 0.5 × 80 = 40 mL/h, the number that actually drives the rate.

Timing from the injury rather than from arrival is the trap. MSD adds that if urine output stays inadequate despite large crystalloid volumes, a burn center should be consulted, because those patients risk abdominal and extremity compartment syndromes. Rework the arithmetic with new numbers until it is automatic; for mixed practice under a streak goal, a Perfect 10 challenge planned for CCRN prep is one option.

Rhabdomyolysis: CK, urine color and the kidney

MSD's rhabdomyolysis chapter (full review February 2026) describes skeletal muscle breakdown releasing myoglobin, creatine kinase and electrolytes:

• Causes on an ICU. Crush injury, electric shock, seizures and compartment syndrome; medications and toxins such as statins, antipsychotics, cocaine, amphetamines and alcohol; and infections. Heatstroke and malignant hyperthermia can produce it too, and MSD's burns chapter addresses it in burn resuscitation.
• Diagnosis. A CK typically more than 5 times the upper limit of normal. The classic triad of weakness, myalgia and dark urine appears in fewer than 10% of patients, and because myoglobin clears quickly, clear urine doesn't exclude it. A dipstick positive for blood with no red cells on microscopy suggests myoglobinuria.
• The kidney risk. Acute kidney injury occurs in 15 to 55% of cases and is more likely with dehydration, sepsis and CK above 15,000 IU/L. Other labs can show hyperkalemia, hyperphosphatemia, hyperuricemia, low or high calcium, lactic acidosis and thrombocytopenia.
• Treatment. IV fluids to prevent kidney injury, early fasciotomy if compartment syndrome caused it, stopping causative drugs such as statins, correcting electrolytes, and sometimes dialysis.

A conflict to know about. MSD's burns chapter says urine alkalinization with bicarbonate is no longer recommended for rhabdomyolysis because there's little evidence of benefit, while MHAUS's malignant hyperthermia protocol still includes a bicarbonate infusion if CK or potassium rises. If an item turns on this, follow the context the stem gives; at the bedside, follow your protocol.

Poisoning and overdose: general priorities and the acetaminophen clock

MSD's general poisoning chapter (full review April 2025) says most poisonings are treated supportively, with specific antidotes for some substances, and recommends consulting a poison control center. Its priorities:

• Breathing first. A patient with apnea or a compromised airway gets assisted ventilation and IV naloxone; if there's no rapid response, the airway is secured with intubation.
• Activated charcoal, sometimes. It may be given particularly within 1 to 2 hours of a potentially toxic ingestion, but it carries aspiration risk in patients at risk of vomiting, and hasn't been proved to reduce overall morbidity or mortality.
• Levels only where they help. For most substances blood levels don't guide treatment; MSD names exceptions such as acetaminophen, aspirin, carbon monoxide, digoxin, ethylene glycol, iron, lithium, methanol, phenobarbital, phenytoin and theophylline.
• Always think acetaminophen. Many authorities recommend an acetaminophen level in every mixed ingestion, because early poisoning is often silent.

The acetaminophen clock. MSD's acetaminophen chapter (full review April 2025) explains why timing dominates these items:

MSD adds that if the degree of toxicity is uncertain, N-acetylcysteine is given until toxicity is ruled out, and that acetaminophen overdose should be considered in every intentional ingestion. Timing rules like these are the kind of fact the 90 Multisystem flashcards planned for CCRN prep are meant to hold. The delirium and behavioral guide covers suicide screening after an intentional overdose.

Submersion injuries: hypoxia first

MSD's drowning chapter (full review August 2026) says hypoxia is the major insult, damaging the brain, heart and other organs, with cerebral edema and metabolic acidosis possible. Cold water adds hypothermia, which can be harmful but sometimes protective. MSD notes that the old distinction between freshwater and seawater drowning isn't considered important for most patients, and that people who dive into shallow water may have cervical spine injuries, which may themselves be the cause of the drowning. On the exam, that means oxygenation and ventilation come first, and spinal precautions apply when the history includes a dive.

Your next step for CCRN Multisystem

Write the four MHAUS steps, the heatstroke cooling target and the Parkland timing rule on one card, and say them aloud before your next shift. Then rework the burn example with a different weight, TBSA and arrival time. For the neurological side of anoxic injury and brain death, see the neuro and musculoskeletal review.