Can a patient undergoing spinal decompression from T6 to L1 with intraoperative neuromonitoring (intraoperative neurophysiological monitoring) be given a combination of total intravenous anesthesia (TIVA) and epidural anesthesia?

Combining TIVA with Epidural Anesthesia for Spinal Decompression T6-L1 with Neuromonitoring

Yes, you can combine TIVA with epidural anesthesia for this procedure, but epidural placement should be avoided at or near the surgical levels (T6-L1) due to risk of epidural hematoma and interference with surgical access. 1

Key Considerations for Anesthetic Technique

Neuromonitoring Requirements

• TIVA is the preferred anesthetic technique when using intraoperative neurophysiological monitoring (IONM) with neuromuscular blockade. 1 The 2021 Association of Anaesthetists guidelines explicitly recommend processed EEG monitoring when TIVA is administered together with neuromuscular blocking drugs, starting before induction and continuing until full recovery from neuromuscular blockade is confirmed. 1

• Multimodality monitoring combining motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs) is appropriate for thoracolumbar decompression procedures. 2, 3 While the evidence for IONM benefit is strongest in cervical myelopathy cases, the extensive surgical levels (T6-L1) and proximity to the conus medullaris justify monitoring. 4

• Volatile anesthetics significantly suppress MEP and SSEP signals more than intravenous agents. 5, 6 Even at 0.5 MAC (3% desflurane), halogenated agents cause greater signal depression than TIVA, though some centers successfully use this approach in select patients. 5

Epidural Anesthesia Considerations

The epidural catheter must be placed remote from the surgical site - ideally in the lumbar region below L1 if the surgical field extends to L1, or in the high thoracic region (T1-T4) if technically feasible and the surgical field starts at T6. 1

Rationale for remote placement:

• Epidural placement at surgical levels risks epidural hematoma formation, particularly with surgical manipulation and potential bleeding. 1
• The catheter would interfere with surgical access and decompression at T6-L1 levels. 1
• Epidural anesthesia/analgesia has demonstrated benefits including lower opioid requirements, better ablation of catecholamine response, and reduced hypercoagulable state. 1

Hemodynamic Management

• High thoracic epidural levels (required to cover T6-L1 dermatomes) can cause significant sympathetic blockade, resulting in hypotension and bradycardia. 1 This is particularly concerning as the cardioaccelerator fibers (T1-T4) may be blocked. 1

• Prepare vasopressors and intravenous fluids before epidural dosing. 1 The ACC/AHA guidelines note that epidural techniques for thoracoabdominal procedures require high dermatomal levels and may be associated with significant hemodynamic effects. 1

• Monitor blood pressure continuously during epidural top-ups, assessing block height at least every 5 minutes until no further extension is observed. 1 Increasing agitation, significant hypotension, bradycardia, upper limb weakness, or dyspnea may indicate excessive cephalad spread. 1

Practical Implementation Algorithm

Step 1: Preoperative Assessment

• Verify coagulation status and platelet count before epidural placement. 1
• Identify patient comorbidities: hypertension and diabetes are independent predictors of IONM signal failure and are preferentially sensitive to inhalational agents. 6

Step 2: Epidural Placement

• Place epidural catheter in lumbar region (L2-L4) if surgical field extends to L1, OR in high thoracic region (T1-T4) if technically feasible. 1
• Never place epidural at T6-L1 levels where surgery will occur. 1
• Test dose with 3 mL of local anesthetic to confirm epidural (not intrathecal) placement. 1

Step 3: IONM Baseline Acquisition

• Obtain baseline SSEPs and MEPs before intubation and positioning. 7 This is the most frequent error in IONM - failure to obtain adequate preoperative baselines. 7
• Use TIVA with propofol (100-150 μg/kg/min) and remifentanil or fentanyl. 5, 8
• Avoid or minimize neuromuscular blockade after baseline acquisition to preserve MEP monitoring. 1

Step 4: Epidural Dosing Strategy

• Use incremental dosing: start with 3-5 mL boluses of dilute local anesthetic (e.g., 0.125-0.25% bupivacaine). 1
• Assess block height every 5 minutes after each dose. 1
• Target sensory level to T4-T6 for adequate analgesia without excessive sympathetic blockade. 1
• Avoid epidural opioids that could cause respiratory depression postoperatively. 1

Step 5: Intraoperative Monitoring

• Maintain TIVA throughout procedure - propofol 100-150 μg/kg/min with opioid infusion. 5, 8
• If MEP/SSEP signals deteriorate, first check: blood pressure (maintain MAP >65 mmHg), temperature, electrode placement, and limb positioning. 7
• Consider reducing epidural infusion rate if hypotension contributes to signal loss. 7

Common Pitfalls to Avoid

• Never assume an epidural catheter is in the epidural space based on inability to aspirate CSF. 1 Failure to aspirate CSF does not exclude subarachnoid positioning. 1

• Do not give epidural doses through a catheter that may have migrated intrathecally. 1 This has resulted in high or total spinal blocks, hypotension, and even cardiac arrest. 1

• Avoid volatile anesthetics entirely if baseline MEPs are difficult to obtain or patient has diabetes/hypertension. 6 These patient characteristics predict monitoring failure and are preferentially sensitive to inhalational agents. 6

• The combination of high thoracic epidural and TIVA-induced vasodilation can cause profound hypotension. 1 Have phenylephrine or norepinephrine infusion prepared before starting. 1

Postoperative Considerations

• Continue epidural analgesia postoperatively with dilute local anesthetic ± low-dose opioid. 1
• While epidural analgesia did not reduce delirium incidence in some studies, post-hoc analysis showed reduced overall delirium episodes during hospital stay. 1
• Monitor respiratory function closely if epidural opioids are used, as respiratory depression has been reported. 1
• Maintain processed EEG monitoring until neuromuscular blockade is fully reversed (train-of-four ratio >0.9). 1