What causes a severe burn from a grounding pad during a lumbar radio frequency procedure?

Grounding Pad Burns During Radiofrequency Procedures: Mechanism and Prevention

How Grounding Pad Burns Occur

Severe burns from grounding pads during radiofrequency procedures result from excessive thermal energy deposition at the pad-skin interface when the current density becomes too high, causing temperatures to exceed 47°C for second-degree burns and 52°C for third-degree burns. 1

Primary Mechanisms of Injury

The radiofrequency current must complete a circuit from the active electrode (at the treatment site) back to the generator through the grounding pad. Burns occur when:

• Inadequate pad surface area concentrates current density at the return electrode site, causing localized heating 1
• Poor pad-to-skin contact creates high-resistance areas where current concentrates, generating excessive heat 1, 2
• Improper pad placement relative to the RF electrode affects current distribution and thermal deposition 1
• High current output (1,000-2,000 mA typical for ablation procedures) increases thermal energy at all contact points 1

Critical Variables That Increase Burn Risk

Research demonstrates that temperature elevations at grounding pads are dependent on multiple factors:

• Number of pads used: Single pads carry higher risk than multiple pads distributing current 1
• Pad orientation: Horizontal placement with the longest edge facing the RF electrode reduces heating compared to vertical or diagonal orientations 1
• Distance from electrode: Pads placed <25 cm from the active electrode experience higher thermal deposition 1
• Pad material: Foil pads demonstrate significantly reduced heating compared to mesh pads (P < .001) 1
• Skin preparation: Inadequately prepared skin (moisture, oils, poor adhesion) increases contact resistance 1

The Current Path Problem

The RF current path from electrode tip to return pad must be kept as far away from sensitive structures as possible, and inadequate attention to this principle leads to concentrated current flow and thermal injury. 3

Temperature monitoring during experimental RF ablation showed elevations ≥12°C occurred in 68.2% of trials, with some reaching 45°C at the grounding pad site 1. Third-degree burns were documented when temperatures exceeded 52°C 1.

High-Risk Clinical Scenarios

Patient Factors

• Thin patients or low BMI: Minimal subcutaneous tissue between the lesion target and dermis increases burn risk 4
• Anatomic regions with minimal soft tissue: Thoracic procedures in thin patients are particularly high-risk 4
• Sedated or anesthetized patients: Cannot report unusual sensations or pain that would prompt immediate cessation 5

Procedural Factors

• Cooled radiofrequency ablation (C-RFA): Creates larger spherical lesions than conventional RFA, increasing the risk of skin injury when used near the surface 4
• High-current procedures: Ablations requiring 1,000-2,000 mA carry substantially higher burn risk 1
• Prolonged ablation times: 10-minute ablation periods allow cumulative thermal injury 1

Prevention Algorithm

Pre-Procedure Checklist

1. Pad selection and quantity:

   • Use multiple large-surface-area foil pads (minimum 100 cm² each) rather than single pads 1
   • Four foil pads placed horizontally ≥25 cm from the electrode prevented burns even at maximum generator output (2,000 mA) 1

2. Skin preparation:

   • Ensure skin is clean, dry, and free of oils or lotions 1, 2
   • Verify complete pad adhesion across entire surface area 2
   • Avoid placement over bony prominences, scar tissue, or areas of poor perfusion 2

3. Pad placement strategy:

   • Position pads with longest edge oriented horizontally toward the RF electrode 1
   • Maintain ≥25 cm distance between pads and active electrode 1
   • Distribute pads to create multiple low-resistance return pathways 1
   • Never place pads on the surgical table where patient weight can compromise contact 2

Intra-Procedure Monitoring

• Maintain patient awareness when possible: Sedation prevents patients from reporting burning sensations that signal thermal injury 5
• Visually inspect pad sites during prolonged procedures for skin blanching, which indicates thermal injury 4
• Consider temperature monitoring at pad sites for high-risk cases (thin patients, high-current procedures) 1

Critical Pitfalls to Avoid

• Placing grounding pads on the surgical table: This was the mechanism in a reported full-thickness burn case where the patient's calf rested on the pad, creating inadequate contact and pressure-related injury 2
• Using single small pads for high-current procedures: Inadequate surface area guarantees excessive current density 1
• Ignoring patient body habitus: Thin patients (BMI <22 kg/m²) require extra vigilance, especially for thoracic procedures 4
• Deep sedation during RF procedures: Eliminates the patient's ability to report pain, which is an early warning sign 5
• Improper pad orientation: Vertical or diagonal placement increases thermal deposition compared to horizontal orientation 1

When Burns Occur: Immediate Recognition

Full-thickness burns from grounding pads have been documented in cervical, thoracic, and lumbar RF procedures 5, 4. Recognition includes:

• Intra-procedural: Skin blanching (15-20 mm diameter), patient complaints of severe localized pain at pad site 4
• Post-procedural: Full-thickness skin defects that may worsen in appearance over hours, requiring 5 months to heal 4
• Delayed presentation: 3 cm × 3 cm full-thickness burns discovered after procedure completion 2

These injuries require immediate surgical consultation for debridement and possible closure, as they represent true thermal burns requiring wound management beyond simple dressings 2.