6.4 Hypothermia, Drowning, Pregnancy, and Toxicology

6.4 Special Resuscitation Situations

These scenarios are tested as modifications to the core algorithms. You keep delivering high-quality CPR and following BLS/ACLS, while adding the one cause-specific intervention that changes the outcome.

Opioid overdose and toxicology

Opioid poisoning kills by respiratory depression: slow or absent breathing, pinpoint pupils, and a depressed level of consciousness. The decision hinges on the pulse.

• Has a pulse but is not breathing normally (respiratory arrest): open the airway, give rescue breaths, and administer naloxone 0.4-2 mg IV/IM/SQ or 4 mg intranasal, repeating every 4 minutes as needed. In opioid-dependent patients a small IV dose (0.04-0.1 mg) avoids precipitating withdrawal.
• Pulseless (cardiac arrest): run standard CPR and ACLS - compressions, defibrillation for shockable rhythms, and epinephrine. Naloxone has no proven benefit in confirmed cardiac arrest and must never delay compressions. Other toxicologic causes have specific antidotes: sodium bicarbonate for tricyclic antidepressant overdose (QRS widening) and for hyperkalemic arrest, calcium for calcium-channel-blocker toxicity and hyperkalemia, high-dose insulin/glucose for calcium-channel and beta-blocker overdose, and intravenous lipid emulsion for local-anesthetic systemic toxicity.

Drowning

Drowning produces a primary hypoxic (asphyxial) arrest. Unlike a sudden cardiac arrest, the priority is oxygenation and ventilation first. Rescuers should deliver rescue breaths early - often 2 initial breaths as soon as it is safe (even in the water by trained rescuers) - then begin chest compressions. Use the standard 30:2 ratio for one rescuer once on land, and attach an AED. Do not assume hypothermia or spinal injury delays ventilation.

Anaphylaxis

Anaphylaxis is a rapidly progressive, multisystem allergic reaction (airway swelling, bronchospasm, hypotension, urticaria). Intramuscular epinephrine is first-line and life-saving.

• Adult dose: epinephrine 0.3-0.5 mg IM of 1:1000 (1 mg/mL) into the anterolateral thigh (vastus lateralis), which achieves faster peak levels than the deltoid or the subcutaneous route.
• Repeat every 5-15 minutes if symptoms persist; most patients need only one or two doses.
• Adjuncts (antihistamines, corticosteroids, IV fluids, bronchodilators) are secondary and never replace epinephrine. In anaphylactic cardiac arrest, give high-quality CPR with IV/IO epinephrine per ACLS plus aggressive fluids.

Hypothermia

Severe accidental hypothermia slows metabolism and can mimic death; handle gently (rough handling can trigger VF), prevent further heat loss, and rewarm. The maxim is "not dead until warm and dead." During arrest, continue CPR; if core temperature is below 30 degrees C, defibrillation and drugs may be ineffective, so many protocols limit shocks and withhold or space out medications until rewarming above 30 degrees C.

Pregnancy (maternal cardiac arrest)

The gravid uterus compresses the aorta and inferior vena cava, reducing venous return.

• Provide continuous manual left uterine displacement (LUD) during CPR to relieve aortocaval compression.
• Use standard hand position, compression rate/depth, and defibrillation energy; pads/paddles are placed normally and shocks are safe for the fetus.
• Activate the maternal/obstetric and neonatal teams immediately and prepare for resuscitative hysterotomy (perimortem cesarean delivery), to be performed by about 4 minutes of arrest (delivery by ~5 minutes) if there is no ROSC, because uterine evacuation improves maternal venous return and resuscitation.

Scenario anchor

A pregnant patient at 34 weeks arrests in the ED. The team starts compressions at standard depth/rate, a second rescuer applies continuous left uterine displacement, the AED/defibrillator delivers normal-energy shocks for VF, obstetrics is paged, and the team prepares resuscitative hysterotomy by the 4-minute mark with no ROSC.

More Special Causes and Antidotes

Hypothermia staged management

Management is driven by core temperature, and the classic rule is that resuscitation continues until the patient is rewarmed ("not dead until warm and dead").

The rationale: a profoundly cold myocardium often will not respond to defibrillation or metabolize drugs, so repeated shocks and drug stacking are futile and can cause toxic accumulation once rewarmed.

Electrocution and lightning

Electrical injury and lightning strike can cause respiratory arrest (paralysis of respiratory muscles) and cardiac arrest (VF or asystole). In a mass-casualty lightning event, reverse triage applies: treat the apparently dead first, because those in respiratory or cardiac arrest may recover with prompt ventilation and CPR while spontaneously breathing victims usually survive. Ensure scene safety (power off) before contact.

Toxicology antidote quick reference

Unifying principle

Every special situation layers a cause-specific action onto uninterrupted high-quality CPR and standard ACLS. The exam wants you to keep delivering compressions, ventilation, and defibrillation while adding the one intervention - naloxone, epinephrine IM, left uterine displacement, rewarming, or the right antidote - that addresses the reversible cause. Never stop or downgrade core resuscitation just because the etiology is unusual.