Acute bradyarrhythmia management: identifying hemodynamic instability, distinguishing sinus node arrest vs high-grade AV block, medical chronotropic support (atropine, epinephrine), and emergent pacing.
New-onset bradycardia (heart rate < 50–60 bpm) in the critically ill patient can result from intrinsic cardiac conduction system disease, severe electrolyte derangements, autonomic/reflex vagal activation, drug toxicity, or life-threatening raised intracranial pressure (the Cushing reflex). The first clinical objective is identifying signs of poor perfusion and rapidly distinguishing nodal from infranodal conduction block to guide medical therapy versus emergency electrical pacing.
Caution
Dangerous Diagnosis Not to Miss: Severe Hyperkalemia (presenting with progressive bradycardia, peaked T-waves, PR prolongation, and sine wave arrest), Mobitz II or Complete (3rd-degree) Heart Block with wide QRS escape, Acute Inferior/Posterior STEMI with RCA nodal ischemia, and the Cushing Triad (bradycardia, hypertension, irregular breathing) signaling impending brain herniation.
Immediate Hemodynamic Screen: Check for hypotension (MAP < 65), altered mental status, chest pain (ischemia), acute pulmonary edema, or cold mottled extremities.
Continuous Cardiac Monitoring: Obtain an immediate 12-lead ECG to analyze P-wave morphology, PR interval, P:QRS conduction ratio, and QRS complex duration.
Sinus Bradycardia & Sinus Arrest: High vagal tone (endotracheal suctioning, vomiting), hypothermia, severe hypothyroidism (myxedema), medications (beta-blockers, CCBs, dexmedetomidine, clonidine, digoxin, amiodarone).
Atrioventricular (AV) Blocks:
Metabolic & Autonomic Triggers: Severe hyperkalemia, profound hypoxemia, severe acidemia, raised intracranial pressure (Cushing reflex).
Step 1: Atropine Sulfate 1.0 mg IV push every 3–5 minutes (maximum 3.0 mg total). Highly effective for sinus bradycardia and Mobitz I block; minimally effective in Mobitz II or 3rd-degree block with wide QRS escape.
Step 2: Chronotropic Infusions (if atropine is ineffective or pacing is being prepared):
Caution
Common Diagnostic Trap: Relying solely on electrical capture on the monitor during transcutaneous pacing without confirming mechanical capture (palpating a femoral pulse or seeing arterial line pulsatility). Electrical spikes with muscle twitching can mimic capture while the patient remains in asystolic arrest.
Arrhythmias: Conduction system taxonomy, pacing thresholds, and antiarrhythmic reversal.
Cardiac Arrest: ACLS bradycardia algorithms and pulseless electrical activity protocols.
Hyperkalemia: Membrane stabilization and emergent elimination.
Intracranial Hypertension: Cushing reflex and emergency osmotherapy.
Acute Coronary Syndromes: Inferior STEMI and right coronary artery perfusion.
Evidence status
Review metadata not yet recorded.
Status, review dates and guideline versions appear here once editorial metadata is authored for this content.
From recognizing hypoperfusion and initial crystalloid bolus to dynamic fluid responsiveness assessment and vasopressor targets.
From first-line norepinephrine titration to multi-agent vasopressor escalation and inotrope selection.
From multi-vasopressor failure to rescue non-adrenergic agents and mechanical circulatory support.
From confirming true hypotension to recognizing shock and its likely category.
Algorithmic tachy- and bradyarrhythmia management, new-onset ICU atrial fibrillation, wide-complex tachycardia differentiation, and refractory Torsades overdrive pacing protocols.
Nernst resting potential mechanics, ECG progression, the 3-step resuscitation framework (Stabilize, Shift, Eliminate), and post-dialysis rebound kinetics.
Monro-Kellie doctrine, ICP waveforms (P2>P1, Lundberg A-waves), CPP targets (60–70 mmHg), herniation syndromes, and the 4-tier BTF management protocol.
Plaque rupture, coronary thrombosis, STEMI vs NSTEMI risk stratification, emergent reperfusion, DAPT/anticoagulation, and mechanical/electrical ICU complications.
Cellular dysoxia, DO2/VO2 physiology, the 4 shock phenotypes, dynamic fluid responsiveness (PLR/PPV) vs fluid tolerance (VExUS), and vasoactive pharmacology.
Multimodal resuscitation, post-cardiac arrest syndrome management, targeted temperature control, and delayed neuroprognostication.