What is the most likely intervention to help a patient with severe hypotension and bradycardia unresponsive to atropine (anticholinergic medication)?

Transcutaneous Pacing

This patient requires immediate transcutaneous pacing (TCP). She has symptomatic bradycardia with severe hypotension (72/40 mm Hg) and signs of shock (diaphoresis, lightheadedness) that has failed to respond to atropine, making TCP the next critical intervention to prevent cardiovascular collapse and death. 1, 2

Clinical Reasoning

This 55-year-old woman presents with hemodynamically unstable bradycardia manifesting as:

• Severe hypotension (systolic BP 72 mm Hg, well below the 80 mm Hg threshold for instability) 1
• Signs of shock including diaphoresis and lightheadedness 2
• Palpable pulses indicating she still has perfusion, but is critically compromised
• Failed atropine response after receiving 1 mg IV 1

Why Transcutaneous Pacing is the Answer

The American Heart Association guidelines explicitly recommend TCP for unstable patients who do not respond to atropine (Class IIa, Level of Evidence B). 1, 2 The guidelines state that "it is reasonable for healthcare providers to initiate TCP in unstable patients who do not respond to atropine." 1

Key Supporting Evidence:

• ACC/AHA guidelines classify symptomatic bradycardia with hypotension unresponsive to atropine as a Class II indication for transcutaneous pacing 1
• TCP can be applied rapidly without the delays and complications associated with transvenous pacing, which is critical in this deteriorating patient 1
• TCP serves as an urgent expedient while preparing for definitive therapy if needed 1

Why NOT the Other Options

Synchronized/Unsynchronized Cardioversion

• Cardioversion is for tachyarrhythmias, not bradycardia 1
• This patient has bradycardia causing hypotension, not a tachyarrhythmia requiring electrical conversion
• Cardioversion would be inappropriate and potentially harmful

Endotracheal Intubation

• Intubation does not address the primary problem of inadequate heart rate and cardiac output 2
• While airway management may eventually be needed if the patient deteriorates further, it does not treat the underlying bradycardia
• The immediate life-threatening issue is hemodynamic instability from bradycardia, not respiratory failure

Clinical Algorithm for Symptomatic Bradycardia

1. First-line: Atropine 0.5-1 mg IV, repeat every 3-5 minutes up to maximum 3 mg 1, 2
2. If atropine fails: Transcutaneous pacing (this patient is here) 1, 2
3. Alternative/adjunct: β-adrenergic agonists (dopamine 5-10 mcg/kg/min or epinephrine 2-10 mcg/min) 1, 2
4. If TCP fails: Transvenous pacing 1

Important Caveats

TCP Limitations:

• TCP is painful in conscious patients and may require sedation/analgesia 1
• TCP is a temporizing measure only - prepare for transvenous pacing if the patient doesn't stabilize 1
• Verify electrical and mechanical capture - ensure the pacing spikes are followed by QRS complexes and that there is actual pulse generation 2

Atropine Considerations:

• This patient received only 1 mg - technically could receive up to 3 mg total, but given her severe hypotension and deterioration, waiting for additional atropine doses would be dangerous 1
• Atropine may be ineffective in certain types of AV block (Mobitz II, third-degree with wide QRS) where the block is infranodal 1
• Without seeing the rhythm strip, we cannot definitively determine the type of block, but the failure to respond to 1 mg atropine suggests either infranodal block or severe nodal dysfunction 1

Common Pitfalls:

• Don't delay TCP while giving additional atropine doses in a patient this unstable 1, 2
• Don't confuse bradycardia management with tachycardia management - cardioversion has no role here 1
• Don't focus on airway management when the primary problem is cardiac output 2