Evaluating our Initial Experience with Hepatic Hilar Nerve Block for Microwave Ablation of Liver Malignancies: Procedure Time, Efficacy and Duration

Percutaneous thermal ablation is a leading therapy for the treatment of select liver malignancies. However, ablation causes substantial intra-procedural pain, necessitating the support of general anesthesia.  Use of general anesthesia does have significant trade-offs including increased procedural time, use of more resources, increased risk of complications and sometimes increased difficulty of targeting the liver mass for ablation.  Recently, the hepatic hilar nerve block has been described as an adjunct to enable performing thermal ablations under conscious sedation.  The time to perform the nerve block and duration of the nerve block have not been reported.  We present our experience.



Materials and Methods:

We reviewed medical charts for microwave ablations of liver masses where CT guided hilar hepatic nerve block was attempted at a single institution from January to October 2022.  Patient demographics, medical history, procedural details, outcomes and complications were reviewed. 

Patients were treated initially with iv midazolam and fentanyl until patients were made comfortable.  Lidocaine 1% was injected into the procedural puncture sites.  Using CT guidance, a 21-gauge Chiba needle was placed adjacent to the main portal vein within 2 cm of its bifurcation.  Approximately 10 mL of dilute contrast was injected in the periportal space, which was confirmed by CT (technical success).  If appropriate spread of contrast identified, then 20 mL of bupivacaine 0.5% was injected.  Clinical success was determined if no bolus of medications was administered after ablation was started.  Patient were called up until post-procedure day 3 to determine if and when their post-procedural pain began using the visual analog scale (VAS) scores (0 = no pain, 10 = worst imaginable pain).

Results:

Eight patients underwent 9 procedures.  The mean number of tumors treated was 1.8 (range of 1 to 3) using a mean of 3.4 ablation probes (range of 2 to 6).  The mean amount of midazolam administered was 3.3 mg (range of 2 to 4.5) and mean amount of fentanyl administered was 197.2 mcg (range of 100 to 300).  The mean number of passes with a 21G needle to access hepatic plexus was 5.8 passes (range of 4 to 10) with mean additional time required of 9.7 minutes (range of 1.5 to 19).  The technical and clinical success rate was 100%.  The mean duration of the nerve block was 12.8 hours (range of 6 to 21).

Conclusion:

We had a 100% technical and clinical success with our initial 9 procedures with the hepatic hilar nerve block which added a mean of 10 minutes to ablations and provided a mean of 13 hours of pain relief.