Transcutaneous Pacing

Indications

• Symptomatic bradycardia unresponsive to atropine
• Mobitz II second-degree AV block
• Third-degree (complete) AV block
• New LBBB / bifascicular block in the setting of acute MI with hemodynamic compromise
• Bradyasystolic arrest (bridge to transvenous pacing)
• Standby for high-risk conduction disease

Setup before you pace

• Apply pacer / defib pads in anterior–posterior position (preferred) or anterolateral.
• Connect ECG leads from the same monitor (the device tracks intrinsic QRS through them, not the pads).
• IV access × 2; have atropine, epinephrine, and dopamine ready.
• Prepare sedation (fentanyl + midazolam or ketamine) — pacing is painful.
• Identify a reliable pulse — femoral or right brachial preferred (left side may pick up muscle twitch).
• Place defib pads, monitor, and SpO₂ on the patient before turning the pacer on.

Step-by-step

1. Turn the monitor/defibrillator to PACER mode.
2. Set mode to DEMAND (synchronous) — pacer fires only when intrinsic rate falls below set rate. Use Asynchronous (fixed) only if no reliable QRS to sense.
3. Set rate to 60–80 bpm (start at 70).
4. Set output (mA) low and titrate up:
   • Start at 0 mA, increase by 5–10 mA every few seconds.
   • Watch monitor for a wide QRS following each pacer spike (electrical capture).
   • Continue increasing until consistent capture, then go 10 mA above the capture threshold.
   • Typical capture threshold: 40–80 mA; obese / large effusions may need higher.
5. Confirm mechanical capture — palpate a pulse that matches each paced beat (femoral or right brachial). Electrical capture without a pulse = pseudo-capture; keep escalating.
6. Reassess BP, mental status, perfusion. If still inadequate at maximum output, escalate to chronotropes / transvenous pacing.
7. Document: pacing mode, set rate, capture threshold, output set, and patient response.

Confirming capture

• Electrical capture: pacer spike followed by a wide QRS and broad T wave on the monitor.
• Mechanical capture: palpable pulse matching the paced rate; improvement in BP and mental status.
• Use a pulse oximeter waveform or arterial line to corroborate — chest wall muscle contraction can mimic a pulse over the carotid.
• If electrical capture without mechanical → treat as pulseless arrest (CPR, ACLS) and escalate output / move to transvenous pacing.

Sedation & analgesia

• Pacing causes painful skeletal muscle contractions — sedate as soon as the patient tolerates it.
• Fentanyl 25–50 mcg IV + midazolam 1–2 mg IV, titrated. Avoid hypotension.
• Ketamine 0.3 mg/kg IV (analgesic dose) is a useful alternative if BP is borderline.
• If unstable patient cannot tolerate any delay, start pacing first and sedate immediately after capture.

Troubleshooting

• No capture at max output: reposition pads (try AP), shave hair, dry skin, replace pads, check connections, exclude pericardial effusion / tension PTX / severe acidosis / hyperkalemia.
• Pacer not firing: verify PACER mode on; in DEMAND mode the device may be sensing intrinsic beats — try increasing set rate above intrinsic, or switch to Asynchronous if appropriate.
• Oversensing: motion or shivering interpreted as QRS — reposition ECG leads, sedate.
• Patient agitated: add sedation; verify capture before increasing output further.
• Persistent failure: bridge with epinephrine 2–10 mcg/min or dopamine 5–20 mcg/kg/min; arrange transvenous pacing.

Pearls

• Always palpate a pulse for mechanical capture — never trust the monitor alone.
• Atropine is generally ineffective in Mobitz II / 3° AV block with wide escape — pace early.
• Hyperkalemia masquerades as bradyarrhythmia / pacing failure — empiric calcium if any suspicion.
• Transcutaneous pacing is a bridge, not a destination — call cardiology / arrange transvenous pacing.