05 Cardiovascular Emergencies and Resuscitation
A practical guide to adult prehospital cardiovascular emergencies, emphasizing perfusion, rhythm-directed treatment, resuscitation, and care after return of spontaneous circulation.
Scope and clinical approach
This guide concerns adult prehospital care. Use current local protocols, medical direction, and the receiving system’s destination criteria; pediatric patients require pediatric algorithms. The resuscitation reference used here is the 2025 AHA and ECC Guidelines.
Assess and stability
Treat the patient’s and stability, not an ECG label alone. Begin with airway, breathing, circulation, mental status, skin signs, vital signs, and a focused history. Apply the monitor, obtain a -lead ECG when indicated, establish IV/IO access as appropriate, and reassess after every intervention.
Look for reversible causes while treating immediate threats. These may include hypoxia, ischemia, medication or toxin effects, electrolyte disturbance, hypovolemia, tamponade, or pulmonary embolism.
A patient is unstable when a rhythm or cardiac condition is associated with poor , such as hypotension, altered mental status, shock, ischemic chest discomfort, syncope, or . Do not delay a lifesaving shock or cardioversion for a complete history, IV access, or a -lead ECG.
and resuscitation
Unresponsiveness with absent or abnormal breathing and no definite pulse indicates . Start high-quality , attach a monitor/defibrillator, and determine whether the rhythm is shockable—ventricular fibrillation or pulseless ventricular tachycardia—or nonshockable—asystole or pulseless electrical activity. Assign clear team roles, use closed-loop communication, and track cycles, shocks, medications, and rhythm checks.
Compression and ventilation technique
Compress at per minute to a depth of at least inches ( cm) in adults, allow full recoil, and minimize pauses. Change compressors about every minutes or sooner if fatigued.
Without an advanced airway, use a compression-to-ventilation ratio. With an advanced airway, continue compressions and ventilate once every seconds; avoid hyperventilation.
Rhythm-directed treatment
: Defibrillate promptly using the manufacturer’s recommended biphasic energy; if the recommended energy is unknown, use the maximum available. Resume immediately for minutes before the next rhythm check. Do not delay a shock for medications or airway placement. For refractory , give epinephrine mg IV/IO every minutes after initial defibrillation attempts. Amiodarone mg, then mg, or lidocaine may be considered according to protocol.
: Do not defibrillate. Resume immediately and give epinephrine mg IV/IO as soon as feasible, then every minutes. Confirm asystole in more than one lead and check for reversible causes.
Use to confirm and monitor an endotracheal tube and to follow quality. An abrupt ETCO₂ rise may signal ROSC; low ETCO₂ alone is not a reason to stop resuscitation.
Prioritize compressions and defibrillation over advanced-airway attempts. Use bag-mask ventilation or an advanced airway according to patient needs, operator skill, and system performance. Routine calcium, sodium bicarbonate, or magnesium is not recommended in undifferentiated arrest; reserve these for specific indications such as hyperkalemia, selected toxicologic emergencies, or torsades.
Reversible causes and judgment
For PEA, consider what could produce organized electrical activity without a pulse: severe hypovolemia, hypoxia, acidosis, potassium abnormality, hypothermia, tension pneumothorax, tamponade, toxins, pulmonary thrombosis, or coronary thrombosis. For , keep interruptions short, ensure effective pad contact and shock delivery, and address correctable causes.
Point-of-care ultrasound may help identify a reversible cause only when it can be performed without interrupting . Termination decisions must follow applicable EMS rules and medical direction; ETCO₂ must not be used in isolation.
include unstable angina and myocardial infarction. Suspect ACS with pressure, tightness, or discomfort in the chest, arm, jaw, back, or upper abdomen, or with dyspnea, nausea, diaphoresis, fatigue, or syncope. Older adults, women, and people with diabetes may have less typical symptoms. A normal first ECG does not exclude ACS.
Assess ABCs, vital signs, pain, history, medications, allergies, bleeding risk, and symptom onset; place the patient on cardiac monitoring.
Obtain and interpret a -lead ECG promptly, repeat it if symptoms persist or change, and transmit or report findings to the receiving facility. Activate the STEMI system and transport to the appropriate center when criteria and local pathways indicate. Do not wait for biomarkers in the field.
Give chewable aspirin mg for suspected ACS unless contraindicated or already taken at an appropriate dose. Give oxygen for hypoxemia or respiratory distress rather than routinely to every patient. Titrate treatment and reassess.
Nitroglycerin may relieve ischemic discomfort when allowed by protocol. Check blood pressure and screen for contraindications, including hypotension, suspected right-ventricular infarction, and recent phosphodiesterase-5 inhibitor use. Relief after nitroglycerin does not confirm ACS, and lack of relief does not exclude it.
Treat dysrhythmias, shock, and pulmonary edema promptly. Give early hospital notification and avoid delays in definitive reperfusion for suspected STEMI.
For example, a patient with persistent chest pressure, diaphoresis, and ST elevation in contiguous leads needs rapid STEMI-system activation and appropriate transport—not repeated nitroglycerin as a substitute for reperfusion. If the ECG is nondiagnostic but symptoms remain concerning, continue monitoring and reassessment and communicate the clinical suspicion.
Dysrhythmias with a pulse
First decide whether the rhythm plausibly explains the patient’s symptoms and whether is compromised. Obtain a -lead ECG when it will not delay treatment, assess for ischemia and heart failure, and correct underlying problems such as hypoxia or medication effects.
Tachycardia
: Perform prompt ; sedate if feasible without delaying treatment. If synchronization cannot be achieved or the rhythm is polymorphic, use an unsynchronized shock.
Stable, regular, narrow-complex tachycardia: Consider vagal maneuvers, then adenosine per protocol. Adenosine is not for irregular rhythms or unstable patients. Use AV-nodal blockers cautiously, particularly when systolic heart failure is suspected.
Wide-complex tachycardia: If uncertain, presume ventricular tachycardia. Unstable patients require ; sustained polymorphic VT requires immediate unsynchronized shock. In stable, regular, monomorphic wide-complex tachycardia, use the appropriate protocol and have a defibrillator ready. Do not give verapamil or diltiazem for an undifferentiated wide-complex rhythm; adenosine is only a consideration for stable, regular, monomorphic rhythms.
Bradycardia
Treat symptomatic bradycardia by supporting and correcting the cause—not by treating a number alone. Consider ischemia, hypoxia, medications, toxins, and metabolic disturbance. Atropine may be used for acute bradycardia with hemodynamic compromise. If ineffective, consider or an IV/IO rate-accelerating agent per protocol; prepare early for pacing when high-grade block and instability are present. Confirm mechanical capture with a pulse and improved , not ECG appearance alone.
and
may present with respiratory distress, crackles, hypoxemia, orthopnea, diaphoresis, and signs of fluid overload. Assess work of breathing, oxygenation, blood pressure, , and possible ACS. Pulmonary edema can coexist with hypotension or shock, so do not assume every patient can tolerate vasodilators.
Support oxygenation and ventilation; use CPAP when indicated and tolerated under local protocol. Nitroglycerin may be appropriate for selected patients with adequate blood pressure, especially with hypertensive pulmonary edema, but avoid it in hypotension and other contraindicated states. Reassess blood pressure and respiratory effort frequently.
Avoid indiscriminate fluid boluses in a patient with pulmonary edema. Suspected requires careful, cause-directed support and rapid transport to an appropriate facility.
Care after resuscitation
ROSC begins a new phase of care; it does not end the emergency. Recheck pulse, blood pressure, rhythm, mental status, ventilation, and oxygenation continuously. Prevent recurrent arrest and treat the likely cause.
Initially use high inspired oxygen until oxygenation can be measured reliably; then titrate to avoid both hypoxemia and hyperoxemia. The AHA target SpO₂ is .
Support blood pressure and avoid hypotension. The AHA recommends maintaining a minimum MAP of at least mm Hg. Treat the underlying cause and follow local vasopressor and fluid protocols.
Obtain a -lead ECG as soon as feasible after ROSC. Interpret it in context: early post-ROSC ECGs can be transiently abnormal, so repeat assessment may be needed. Suspected coronary occlusion still warrants timely communication and destination planning.
Use when an advanced airway is present; provide controlled ventilation and avoid excessive ventilation. Check glucose and assess for seizures or other immediately treatable problems within scope and protocol.
Patients who do not follow commands after ROSC need hospital-based, protocolized temperature control and prevention of fever. Routine rapid infusion of cold IV fluid for prehospital cooling is not recommended.
Give a structured handoff that includes downtime, witnessed status, bystander , initial and subsequent rhythms, shocks, medications, airway, ETCO₂, ROSC time, ECG findings, and response to treatment.
Across cardiovascular emergencies, rapid assessment, repeated reassessment, and treatment guided by and the underlying cause are central. In arrest, high-quality and early defibrillation for take priority. In ACS, early ECG recognition, aspirin when appropriate, system activation, and timely reperfusion matter. For dysrhythmias, instability determines whether electricity is needed; for heart failure, support breathing while protecting blood pressure. Always apply current local protocols and scope of practice.