11.2 Core Workflows and Decision Points

Heat and Cold: Temperature-Driven Decisions

For heat stroke, the single most important intervention is rapid cooling, and the major determinant of outcome is how fast and how completely you lower the core temperature. Cold-water immersion is the most effective method for exertional heat stroke; evaporative cooling (misting plus fans) is used for classic heat stroke in older adults. Cooling is stopped at roughly 38.5-39 C to prevent overshoot hypothermia. Antipyretics are ineffective and are a classic distractor.

Hypothermia is staged by core temperature: mild 32-35 C, moderate 28-32 C, severe below 28 C. Mild patients still shiver; shivering is lost by the moderate stage. Severe hypothermia demands gentle handling (rough movement can trigger ventricular fibrillation) and core rewarming before peripheral rewarming to avoid afterdrop - the paradoxical fall in core temperature when cold, vasodilated peripheral blood returns to the heart. The aphorism 'not dead until warm and dead' means CPR continues during rewarming because cold-protected patients can recover after prolonged arrest.

Burns: Estimate, Resuscitate, Titrate

Burn care follows a fixed sequence. First estimate the burn size using the Rule of Nines: in an adult, the head is 9%, each arm 9%, the anterior trunk 18%, the posterior trunk 18%, each leg 18%, and the perineum 1%. Then calculate fluid with the Parkland formula.

Parkland: total mL of Lactated Ringer's in the first 24 h = 4 mL x body weight (kg) x %TBSA burned. Give half in the first 8 hours measured from the time of the burn, and the remaining half over the next 16 hours.

Worked example: an 80 kg adult with 25% TBSA needs 4 x 80 x 25 = 8,000 mL over 24 h, so 4,000 mL in the first 8 hours (about 500 mL/h) and 4,000 mL over the next 16 hours. Titrate the rate to urine output of 0.5-1 mL/kg/h in adults, the single best marker of adequate resuscitation. Suspect inhalation injury with facial burns, singed nasal hair, carbonaceous sputum, or hoarseness, and secure the airway early before edema closes it.

Toxicology: A Universal Order of Operations

Every poisoning follows the same skeleton: supportive care (ABCs), then decontamination, then antidote. Supportive care - airway protection, supplemental oxygen, IV access, cardiac monitoring, and treating hypoglycemia and seizures - keeps the patient alive while the toxin is cleared.

Decontamination options:

• Activated charcoal (1 g/kg) for many oral ingestions within about an hour, if the airway is protected; it does not bind iron, lithium, alcohols, or hydrocarbons.
• Whole-bowel irrigation for sustained-release products, iron, or body packers.
• Skin and eye irrigation for dermal/chemical exposures.

Only after this do you reach for a specific antidote. The classic worked pairing is organophosphate poisoning: the cholinergic SLUDGE toxidrome (salivation, lacrimation, urination, defecation, GI distress, emesis) is reversed with atropine to dry secretions and reverse muscarinic effects, plus pralidoxime (2-PAM) to reactivate acetylcholinesterase at the nicotinic neuromuscular junction before the enzyme 'ages.'

Submersion and Bite/Sting Decision Points

Submersion (drowning) flips the usual arrest sequence. Because the lethal problem is hypoxemia, the drowning algorithm prioritizes early rescue breaths and oxygenation over the chest-compressions-first approach used in cardiac arrest. Give five initial rescue breaths, then proceed with ventilation-focused resuscitation. Anticipate bronchospasm and delayed pulmonary edema, keep the patient under observation for several hours even if initially asymptomatic, and treat coexisting hypothermia simultaneously.

For envenomation, the decision tree turns on the species. Pit-viper (Crotalid) bites call for limb immobilization at heart level, serial marking of the swelling, and CroFab antivenom - never ice, incision, suction, or tourniquets. Marine envenomation divides by toxin type: vinegar deactivates the nematocysts of many jellyfish, while hot-water immersion (about 45 C) denatures the heat-labile venom of stingrays, lionfish, and stonefish. Recognizing which decontamination matches which creature is the tested skill.

Building the Mental Algorithm

The unifying lesson is that every emergency in this domain has a first action that is almost never the antidote. Cool before you medicate the hyperthermic patient. Secure the airway before you worry about burn fluid totals. Oxygenate the drowning victim before compressions. Decontaminate and support the poisoned patient before reaching for a reversal agent. The CEN exam rewards this discipline relentlessly, and the most common error is jumping to the 'interesting' specific treatment while skipping the life-saving basic.

A practical way to encode this is the phrase 'stop the insult, support the ABCs, then reverse.' Each stem gives you a threshold (a temperature, a TBSA, a toxidrome) that tells you what the insult is; your answer should remove that insult and protect the airway, breathing, and circulation before any drug. When two options both sound clinically reasonable, choose the one earlier in this sequence - it is almost always the keyed answer. Internalizing this ordering converts a sprawling list of conditions into a single, repeatable decision pattern you can apply even to an unfamiliar presentation.

Two final workflow refinements round out the core decision points. For burns, after the airway and Parkland fluids, remember escharotomy for circumferential full-thickness burns that compromise circulation or chest-wall expansion, and early transfer for burns meeting American Burn Association referral criteria (for example, burns over 10% TBSA, any full-thickness burn, or burns to the face, hands, feet, genitalia, or major joints).

For hypothermic cardiac arrest, withhold repeated epinephrine and defibrillation attempts until the core temperature rises above roughly 30 C, because the cold myocardium responds poorly to drugs and shocks - another reason CPR simply continues during active rewarming.