At which thoracic vertebral interspace should the epidural catheter be placed for a thoracotomy?

Epidural Level for Thoracotomy

For thoracotomy, place the epidural catheter at the T5-T7 interspace, targeting the mid-thoracic region to optimize dermatomal coverage of the surgical incision.

Rationale for Mid-Thoracic Placement

The optimal epidural level for thoracotomy should correspond to the dermatomal distribution of the surgical incision. Most thoracotomies are performed through the 4th-6th intercostal spaces, making T5-T7 the ideal insertion site to achieve adequate sensory blockade of the surgical field.

Evidence-Based Considerations

While the 2022 PROSPECT guidelines 1 extensively discuss thoracic epidural analgesia for video-assisted thoracoscopic surgery (VATS), they do not specify exact vertebral levels for catheter placement. However, these guidelines demonstrate that thoracic epidural analgesia provides superior pain control at rest and with mobilization compared to IV opioids, with additional benefits including reduced nausea/vomiting and shorter postoperative ileus duration 1.

The 2021 enhanced recovery guidelines for pulmonary lobectomy 2 acknowledge thoracic epidural analgesia as effective but note higher rates of hypotension, urinary retention, and nausea compared to paravertebral blocks.

Technical Factors Affecting Catheter Placement

Approach angle matters significantly. Research demonstrates that using an obtuse approach angle (inserting one level below the target) allows longer catheter threading without coiling—7.4 cm versus 4.9 cm with an acute angle 3. This means:

• If targeting T6-T7 epidural space, insert at T7-T8 or T8-T9 skin level
• Use a paramedian approach with an obtuse angle to maximize successful catheter advancement
• Thread the catheter 4-5 cm cephalad to reach the desired dermatomal level

Critical Caveats

Catheter behavior is unpredictable beyond 2-3 cm of insertion. Studies show that while catheters typically advance straight for the first 1-1.5 vertebrae, they frequently develop curved or coiled paths thereafter 4. This unpredictability means:

• Confirm catheter position with test dosing and sensory level assessment
• Consider fluoroscopic guidance if available, particularly in complex cases
• Be aware that the catheter tip may not reach the intended level despite appropriate insertion technique

For open thoracotomy specifically, the higher failure rates (14.6%) and hypotension risk noted in the VATS literature 1 make thoracic epidural a more invasive option compared to alternatives like paravertebral blocks. However, when epidural is chosen, proper level selection remains crucial for efficacy.

Practical Algorithm

1. Identify the planned thoracotomy incision level (typically 4th-6th intercostal space)
2. Select epidural insertion site: T5-T7 interspace for most thoracotomies
3. Use obtuse approach angle: Insert skin puncture one level below epidural target
4. Thread catheter 4-5 cm cephalad to optimize coverage
5. Confirm placement with test dose and bilateral sensory assessment before surgical incision

The T5-T7 target provides the best balance of dermatomal coverage for thoracotomy incisions while minimizing the risk of excessively high blockade that could compromise respiratory mechanics or cause hemodynamic instability.