Anaesthetic Management of a Patient with a Pacemaker Undergoing Exploratory Laparotomy

1. Introduction and Significance

2. Preoperative Assessment

2.1 History and Records

• Identify the type of device: pacemaker, ICD, or CRT. Each has a different perioperative risk profile and management goal.
• Obtain the CIED identification card (device model, manufacturer, date of implantation). If unavailable, a chest radiograph can identify the device type and manufacturer from the generator silhouette and lead configuration. Contacting the manufacturer's 1-800 number is another option.
• Establish the indication for pacemaker insertion: sick sinus syndrome, complete heart block, AV nodal ablation, etc.
• Determine if the patient is pacemaker-dependent - defined as absence of a perfusing rhythm without pacing. Patients with AV nodal ablation or complete heart block are invariably pacemaker-dependent and are highest risk.

2.2 CIED Interrogation

• Should have been performed within the last 12 months for a pacemaker.
• Review the battery life - at least 3 months remaining is recommended. Perioperative stressors (opioids, beta blockers, calcium channel blockers) can increase pacing requirements.
• Note the pacing mode (e.g., VVI, DDD), programmed lower rate, and whether rate response is enabled.
• Note the pacing threshold - ideally set several times higher for safety.
• Identify the magnet response - this differs by manufacturer and battery life.

2.3 Pacemaker Code (NASPE/BPEG)

2.4 Risk Assessment and Communication

• Type and anatomic site of surgery
• Patient position (supine for laparotomy)
• Whether monopolar electrocautery will be used
• Likelihood of large blood loss or proximity to the generator

• Device type and indication
• Whether the patient is pacemaker-dependent
• Magnet response and pacing rate
• Any need for reprogramming

2.5 Preoperative Investigations

• ECG: identify pacing spikes, QRS morphology, and underlying rhythm
• Chest X-ray: lead positions, generator location, any lead displacement
• Electrolytes: hypokalemia and hyperkalemia alter pacing threshold
• CBC, coagulation: standard pre-laparotomy workup
• Echo if indicated: assess LV function (important for anaesthetic drug selection)

3. Key Perioperative Problem - Electromagnetic Interference (EMI)

EMI Risk Stratification for Laparotomy

• EMI risk is high if monopolar cautery is used within 15 cm of the generator
• For laparotomy, the generator (usually left pectoral region) is typically >15 cm from the operative field if confined to the lower abdomen, but <15 cm for upper abdominal procedures

4. Intraoperative Management

4.1 Reprogramming vs. Magnet Application

• Preferred for pacemaker-dependent patients
• Eliminates the possibility of oversensing
• Requires a CIED programmer and a trained electrophysiologist
• Rate responsive function must be disabled - especially if the sensor is a minute ventilation (transthoracic impedance) sensor, which can falsely increase the pacing rate in response to mechanical ventilation or electrocautery

• Forces asynchronous (fixed-rate) pacing in pacemakers
• Rate varies by manufacturer: Medtronic 85 bpm, Biotronik 90 bpm, Abbott/St. Jude 98.6-100 bpm, Boston Scientific 100 bpm
• Does NOT require a CIED programmer
• BUT - magnet response may be unpredictable in some devices; must be confirmed preoperatively
• Important: magnets placed over ICDs suspend antitachyarrhythmia therapy but do NOT force pacemakers within ICDs to pace asynchronously - reprogramming is mandatory in ICD patients with pacemaker dependence

4.2 Practical Measures to Reduce EMI

• Use bipolar cautery whenever possible, especially when electrocautery is close to the generator
• If monopolar cautery must be used:
  • Place the return (grounding) pad as far from the pacemaker generator as possible - preferably on the thigh or buttock, so current does not traverse the chest
  • Use short, intermittent bursts of cautery (<1 second)
  • Use lowest effective power settings
• Have a magnet immediately available at the operative field
• Disable rate response features preoperatively

4.3 Monitoring

• Standard ASA monitoring: ECG, SpO2, ETCO2, NIBP/IBP, temperature
• Pulse oximetry plethysmograph is the most reliable continuous indicator of pacemaker capture during electrocautery, as the ECG can be obscured by cautery artifact - it confirms that each pacemaker output is generating mechanical cardiac output
• Continuous arterial line monitoring (mandatory for exploratory laparotomy independent of pacemaker) provides beat-to-beat confirmation of perfusion
• Temporary external pacing pads should be applied prophylactically in pacemaker-dependent patients, in case the permanent device fails

4.4 Choice of Anaesthesia

• General anaesthesia with endotracheal intubation is the standard for exploratory laparotomy
• All anaesthetic agents (volatile agents, propofol, opioids, muscle relaxants) have been safely used in patients with pacemakers - none affect pacing electrode thresholds directly
• However:
  • Succinylcholine causes fasciculations that may generate myopotentials and cause pacemaker inhibition - use rocuronium as the preferred muscle relaxant when possible
  • Volatile agents (sevoflurane, isoflurane) are safe but do not alter pacing thresholds
  • Opioids and beta blockers can suppress SA and AV nodal function, potentially increasing pacing requirements - particularly important if battery life is marginal
• Avoid hypothermia (increases pacing threshold) and maintain normothermia
• Avoid severe electrolyte disturbances (hypo/hyperkalaemia) which alter pacing threshold

4.5 Venous Access and Positioning

• Avoid placing central lines via the subclavian or internal jugular vein on the same side as the pacemaker - risk of lead displacement
• Avoid direct pressure on the pacemaker generator during positioning
• For transesophageal echocardiography (TEE): generally safe, used routinely during major laparotomy

4.6 Pacemaker Malfunction - Recognition and Management

• Absence of pacing spikes when expected
• Pacing spikes not followed by QRS complexes (failure to capture)
• Haemodynamic instability (hypotension, bradycardia)

1. Immediately remove or stop the source of EMI (cautery)
2. Apply a magnet to convert to asynchronous mode
3. Check the patient's underlying escape rhythm - if adequate, may proceed with monitoring
4. If haemodynamically compromised: transcutaneous pacing (pads should already be in place), followed by transvenous pacing if needed
5. Pharmacological: atropine (0.5-1 mg IV), isoproterenol, or adrenaline as a bridge
6. Request CIED team/electrophysiology consultation
7. CPR if cardiac output is lost while pacing is restored

5. Emergency Laparotomy - Special Considerations

• Apply a magnet to the device while monitoring the patient; if the heart rate changes abruptly, it is a pacemaker (identify manufacturer by rate - see above)
• If no heart rate change, device is most likely an ICD
• Use the ECG and rhythm strip to assess pacemaker dependence
• Place external pacing/defibrillation pads before incision
• Proceed with above EMI-reduction measures
• Call the device manufacturer's emergency line (24-hour service available from all major manufacturers)

6. Postoperative Management

• Continuous ECG monitoring in PACU/HDU is mandatory
• Patients whose tachyarrhythmia therapy was disabled must have it re-enabled before leaving a monitored setting
• Patients who experienced large fluid shifts, defibrillation/cardioversion, or therapeutic radiation must have device interrogation before discharge
• Routine CIED interrogation is recommended within 1 month postoperatively on an outpatient basis
• Monitor for device reset (manifests as reversion to a safety VVI mode at 65-70 bpm) - this requires urgent CIED team review
• Correct electrolyte abnormalities promptly
• Avoid hypothermia and ensure haemodynamic stability

7. Summary Table

• Miller's Anesthesia, 10th Edition, Chapter 34 (CIEDs), pp. 5155-5185
• Morgan & Mikhail's Clinical Anesthesiology, 7th Edition, Chapter 21, pp. 800-803
• HRS/ASA Expert Consensus Statement on Perioperative Management of Patients with Implantable Defibrillators, Pacemakers and Implantable Monitors (2011)
• ASA Practice Advisory for CIEDs (2020)