British Journal of Radiology (2008) 81, e23-e25
© 2008 British Institute of Radiology
doi: 10.1259/bjr/61546726
Thoracic paravertebral block for analgesia following liver mass radiofrequency ablation
W C Culp, MD1,
M N Payne, MD, MBA1 and
M L Montgomery, MD2
Departments of 1 Anaesthesiology and 2 Radiology, Texas A&M University System Health Science Centre College of Medicine, Scott & White Hospital, 2401 South 31st Street, Temple, TX 76508, USA
Correspondence: William C Culp, Jr, Assistant Professor, Scott & White Hospital, Department of Anesthesiology, Texas A&M University System Health Science College of Medicine, 2401 South 31st Street, Temple, TX 76508, USA. E-mail: wculpjr{at}mac.com
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Abstract
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A 66-year-old man presented for a second attempt of radiofrequency ablation of a metastatic carcinoid liver lesion. The first attempt using intravenous sedation was unsuccessful because of inadequate pain control and subsequent patient combativeness. Despite fentanyl being given during general anaesthesia, the patient complained of severe right flank pain after emergence. A thoracic paravertebral block was performed without complication and the patient's pain decreased to "3 out of 10" on a standard 10-point scale after 10 min, and "0 out of 10" after 30 min. The patient's pain score remained 0 throughout the following day, and no further analgesics were required. Thoracic paravertebral block can provide complete and lasting analgesia following hepatic radiofrequency ablation, and warrants further study for patients undergoing hepatic radiological interventions.
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Introduction
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Hepatic radiofrequency ablation (RFA) is a painful procedure that is most commonly performed under deep intravenous sedation or general anaesthesia. Patients often have pain during and/or following the procedure even with these techniques [1]. Thoracic paravertebral block (PVB), which anaesthetizes the spinal nerve roots and sympathetic chain in the paravertebral space, has long been used to provide unilateral chest and abdominal wall analgesia with a high safety profile [2]. More recently, the block has been used to control pain specifically of hepatic origin during percutaneous transhepatic biliary drainage [3, 4] or after liver trauma [5]. We report a case in which post-procedure thoracic paravertebral blockade provided complete analgesia in a patient with a prior unsuccessful attempt at hepatic RFA with intravenous sedation.
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Case report
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A 66-year-old man presented for a second attempt of RFA of a metastatic carcinoid lesion in the inferior right hepatic lobe measuring 2.6x2.8x3.2 cm. The patient had a medical history significant for carcinoid tumours, hypertension and diabetes. The first attempt of RFA successfully ablated a 4.0x4.1x3.6 cm left hepatic lobe lesion and a 4.3x3.8x2.8 cm lesion at the dome of the right hepatic lobe. The procedure was aborted, however, because of patient pain and combativeness despite administration of midazolam (7 mg), fentanyl (350 µg), ketorolac (50 mg) and 1% lidocaine (10 ml) infiltrated percutaneously along the path of the ablation device. After the procedure was aborted, the patient required naloxone for hypoventilation caused by over-sedation. The patient was rescheduled for ablation of the third lesion to be performed under general anaesthesia.
For the second attempt, general endotracheal anaesthesia was induced with propofol and succinylcholine and maintained with sevoflurane in oxygen. Fentanyl (100 µg) was given intravenously, and 10 ml of 1% lidocaine with epinephrine was injected percutaneously along the path of the ablation device. The multi-tined 17-gauge electrode was inserted and therapeutic burn delivered for 12 min with power maintained at >200 W (Cool-Tip® RF Ablation System; Valleylab, Boulder, CO). This second attempt of ablation was successful (Figure 1
). After the 30 min procedure was completed, the patient emerged from anaesthesia and immediately complained of severe right sided abdominal pain located at the site of the RFA. The patient rated the pain a "10" on a standard 10-point pain scale, with "0" being no pain, and "10" being the worst pain imaginable.
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Figure 1. Computed axial tomography demonstrates the multi-tined ablation needle deep in the right lobe of the liver and well-centred within the lesion.
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At the bedside, a thoracic PVB was placed by two of the authors (WCC, MNP). With the patient in a sitting position and in standard sterile fashion, paravertebral blocks were placed at T6–7 and T8–9 with nerve stimulation guidance. An area 2.5 cm to the right of the superior aspect of the T7 spinous process was anaesthetized with 1% lidocaine. A 100 mm 21-gauge insulated needle (Stimuplex; B Braun Medical, Inc., Bethlehem, PA) was then inserted at this point and advanced to the transverse process. The needle was "walked off" the transverse process cranially and advanced approximately 1.5 cm until a subtle loss of resistance was appreciated and a right abdominal wall twitch was elicited. The twitch disappeared at 0.3 mA. After negative aspiration, 15 ml of 0.25% bupivacaine with epinephrine (1:200 000) was injected incrementally. This process was then repeated at a site lateral to the T9 spinous process, for a total injected volume of 30 ml.
The patient noted immediate improvement in his pain, reporting a pain score of "3" after 10 min and "0" after 30 min. The patient had sensory blockade of the T4–T12 dermatomes and stated "my liver feels numb". No opiates or other analgesics were given. No complications from the block were noted or suspected, and vital signs were stable throughout. The following day the patient reported a pain score of "0" throughout the night and that day, and did not take any analgesics. The patient strongly preferred PVB for analgesia compared with the intravenous opiates he had received for his prior RFA procedure.
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Discussion
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Interventional radiologists often employ deep sedation techniques with midazolam and fentanyl, coupled with instillation of local anaesthetic, to provide procedural sedation and analgesia for hepatic and biliary interventions. Despite this technique, "a substantial majority" of patients experience significant pain for several days, and occasionally for 1–2 weeks, following an ablation procedure [6]. Other hepatic procedures such as percutaneous transhepatic biliary interventions and liver biopsies also cause significant pain. Many, if not most, patients undergoing biliary drainage report suboptimal analgesia [7], and as many as 20% of patients undergoing liver biopsy report severe procedural pain [8]. There exists a real need for improved pain control for this group of procedures and, in a recent editorial, the radiology community has acknowledged this, requesting more inter-specialty collaboration to help solve the problem [9].
Our patient clearly demonstrated this need for improved analgesia. Not only was his sedation inadequate, thus requiring the initial procedure to be aborted, but hypoventilation complicated the patient's recovery. Radiologists often struggle with balancing complex interventions while trying to simultaneously direct sedation in demanding patients, with inadequate analgesia perhaps being preferred to hypotension and respiratory depression [9]. Furthermore, despite general anaesthesia, our patient reported severe pain after the procedure was completed.
Pain from hepatic procedures is mediated predominantly from afferent somatic and sympathetic nerve fibres, with contributions from parasympathetic fibres derived from the vagus nerve [10]. The fibres of the hepatic plexus course through the portal triads to innervate the liver and its capsule, and their presence here may explain the clinical observation of patient pain when ablating tumours in contact with large hepatic vessels or the hepatic capsule [1, 11].
PVB allows these somatic and sympathetic nerve fibres to be anaesthetized, providing superb analgesia or even surgical anaesthesia unilaterally to the chest or abdominal wall. This block was described a century ago by Hugo Sellheim and has experienced a recent resurgence, being commonly used during thoracic, breast and gallbladder surgeries. The block is typically placed by the anatomic landmarks of the spinous and transverse processes with or without nerve stimulator guidance, or alternatively with the aid of fluoroscopy. The paravertebral space is found approximately 1.5 cm deep to the transverse process at a point 2–3 cm lateral to the midline. A loss of resistance is often, but not always, felt as the needle passes through the superior costotransverse ligament [2]. The number of affected dermatomes is a function of the volume of injection. A single 15 ml injection of 0.5% bupivicaine provides a mean unilateral somatic blockade of 5 dermatomes and a mean sympathetic block of 8 dermatomes [12]. A single injection of 15–20 ml of 0.375–0.5% bupivicaine has been shown to be as effective as a multiple-site injection of 0.5% bupivicaine (3–4 ml per site) for unilateral anaesthesia over four to five thoracic dermatomes [2]. Recent evidence suggests that a multiple injection technique may provide a denser block [13]. Complications of the block are uncommon and are easily treated, with pneumothorax occurring in 0.5% of patients and hypotension in fewer than 5% [14]. Of note, the parasympathetic fibres are not targeted with this block, and so total visceral nerve blockade may not be achievable with this technique and is its greatest drawback. Coeliac plexus blockade could provide additional analgesia by addressing this component of pain, although its effectiveness in percutaneous transhepatic biliary drainage is unreliable, and its combined use with PVB is unreported [15]. Epidural anaesthesia could also be used, but carries with it a much higher incidence of hypotension (owing to bilateral sympathectomy) and urinary retention [16], as well as a theoretical higher chance of epidural haematoma, an important consideration in a patient subgroup that often has thrombocytopenia and/or coagulopathy. This risk of haematoma and subsequent spinal cord compression is likely to be higher because of the much larger needle routinely used for epidural placement (typically a 17-gauge Touhy needle compared with a 22-gauge spinal needle), the presence of an indwelling catheter (routinely used for epidural anaesthesia), and the more central location of the epidural space in comparison with the paravertebral space. Epidural anaesthesia also has a greater risk of dural puncture headache and inadvertent spinal anaesthesia. Furthermore, RFA pain is usually right-sided, thereby not requiring bilateral anaesthesia. Anaesthetizing the non-operative, non-painful side has no potential benefit.
Although with this case we have only demonstrated post-procedural analgesia, the implications for providing better pain control for a host of interventional radiological procedures are noteworthy. Pre-procedure PVB may substantially reduce the need for heavy sedation or general anaesthesia for hepatic RFA and biliary interventions. Decreased sedation requirements could improve patient safety by avoidance of respiratory depression and hypotension. Patient satisfaction may be improved by reducing the large number of patients who experience severe intra- and post-procedural pain. Pre-emptive analgesia may further improve patient comfort.
In conclusion, we report a patient who experienced severe post-procedural pain after undergoing hepatic RFA of a carcinoid tumour under general anaesthesia. This pain was quickly and completely eliminated by the placement of a thoracic PVB without complication. Thoracic PVB may be useful for treating patients undergoing hepatic RFA and other similar procedures, such as liver biopsy and biliary interventions, and further research in this area is indicated.
Received for publication July 11, 2006.
Revision received September 2, 2006.
Accepted for publication September 22, 2006.
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References
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Abstract
Introduction
