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Evaluation of neurolytic blocks using phenol and cryogenic block in the management of chronic pain
72
Journal
of Pain and Symptom Management
Vol. 4 No. 2 June 1989
Evaluation of Neurolytic Blocks Using Phenol and Cryogenic Block in the Management of Chronic Pain Somayaji Ramamurthy, MD, Nicolas E. Walsh, MD, Lawrence S. Schoenfeld, PhD and Joan Hoffman, RN University
of Texas Health Science Center, San Antonio,
Texas
Abstract This study compared the use of phenol and cryogenic blocksfor neurolysis in 28 patients. Patients were assigned randomly to receive peripheral nerve blocks with either phenol or cryoanalgesia. Si@ficantly more patients in the phenol group received 20% or greater relief at 2, 12, and 24 wk than patients in the cryogenic group. Only 27% of patients received signaficant relief, however, indicating that neurolytic blocks were not particularly effective even though local anesthetic blocks produced signaficant but temporary pain relief. J Pain Symptom Manage 1989;4:72-75.
Key Wonis Neurolytic nerve blocks, phenol, cryoanalgesia, chronic pain
Introduction Prolonged pain relief provided by neurolytic block is a very desirable modality in the management of chronic pain. When patients obtain temporary but significant relief of pain using local anesthetic agents, an attempt is made to provide prolonged or permanent pain relief using repeated blocks with local anesthetic agents. When this modality is not successful, various less invasive methods are tried before permanent interruption of nerve pathways using neurolytic blocks is considered. Chemical neurolysis using alcohol and phenol have been used with success, but there is a possibility of neuroma formation and neuritis. There are very few studies documenting the usefulness of
Addressreprint requests to: Somayaji Ramamurthy, MD, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78284. for publication: June 27, 1988
Accepted
0 U.S. Cancer Pain Relief Committee, 1989 Published by Elsevier, New York, New York
peripheral nerve blocks using phenol. Cryogenic block of the peripheral nerve has been reported to be useful in managing chronic pain’s* without producing neuritis or neuromas. There are no studies comparing the use of chemical neurolysis produced by phenol to a physical method of neurolytic block, such as that produced by a cryo probe. This study compares the effectiveness of neurolytic block of the peripheral somatic nerves using phenol and cryo probe block.
Methods Twenty-eight patients with chronic pain were recruited for the study. The mean age of patients in the phenol group was 59.7 yr with a range of 26-82 yr, and the mean age of the cryoanalgesia group was 53.8 yr with a range of 26-82 yr. Six were female, and 22 were male. This study was approved by the Institutional Review Board, and informed consent was obo&35-3924/891$3.50
Vol. 4 No. 2 June 1989
73
Neurolytic Blocks for Chronic Pain
tained before enrollment into the study. All patients had previously noted significant but temporary pain relief following local anesthetic blocks. Patients were randomly assigned either to the phenol group or the cryoanalgesia group. A nerve stimulator was utilized to identify the nerve. The phenol group patients received a nerve block using 6% aqueous phenol. Cryo block was performed by using a cryoseeker probe (1.6 mm x 180 mm) introduced through a 12-gauge plastic cannula. The probe was connected to the Cryo-Medic unit model MA300. Nitrous oxide was used to cool the probe, and the tissue temperatures were monitored by using a 23-gauge thermocouple connected to a temperature monitor. After the probe registered -20°C the cooling was continued for 1 min, and the probe was allowed to thaw for 1 min. This cycle was repeated three times.1p3*4 Technical adequacy of the neurolytic block was evaluated by physical findings of a corresponding area of numbness and/or weakness. Patients marked a IO-cm visual analog scale, which was used to determine pain relief, before and after the block and at 2-, 4-, 12-, and 24-wk follow-up visits.5 All patients were maintained on pretreatment medication regimens of nonsteroidal antiinflammatory drugs, tricyclic antidepressants, and other medications for systemic disease processes. Patients were monitored for side effects and complications during the study period. Four patients who did not receive pain relief with one technique received a neurolytic block with the other technique. The percentage of pain relief obtained was compared between the two groups using Fisher’s exact probability test. A P value of less than 0.05 was considered significant.
Results All patients demonstrated physical findings consistent with correct anatomical placement of the needle/probe for neurolytic block procedure. Seventeen patients were included in the phenol group, and 15 patients were included in the cryo group. Table 1 lists the various peripheral nerves that were blocked, and Table 2 shows the pain syndromes of patients receiving blocks. More patients in the phenol group experienced pain relief than the cryo group, when one is comparing 20% or greater relief (P <
Table 1 Types of Nerve Blocks Phenol Intercostal nerve* Tibia1 nerve* Neuroma* Myoneural Paravertebral somatic root block Facet* Brachial plexus Supraorbital nerve Coccygeal nerve Accessory nerve *One patient in each group received phenol block.
6 1 3 3 0 1 0 1 1 1
Cry0 3 3 3 0 3 2 1 0 0 0
both cryo and
0.05) (Table 3) at 2, 12 and 24 wk. At higher percentages of relief, results were not statistically significant. One patient in the cryo group developed neuritis following a paravertebral somatic nerve block. Two patients (13%) were lost to follow-up after 4 wk in the cryo group, and three patients (12%) were lost to follow-up in the phenol group. LliScuSSti Wood,‘j noting the lack of documented studies evaluating phenol for peripheral block, stated, “It is impossible on this information to evaluate the use of phenol in peripheral nerve blocks for pain. One can merely say that it has been done. The likelihood of benefit and percentage of risk is not known.” In this study, neurolytic blocks were not particularly effective, even though local anesthetic blocks produced significant but temporary pain relief in all patients. Hypesthesia was noted in the distribution when nerves with cutaneous innervation were blocked. Thus, we feel that the failure to relieve pain is not due to the lack of correct anatomical placement of the needle.
Table 2
Pain Syndromes Phenol Neuralgias Cancer Facet Musculoskeletal
7 5 1 4
CT 10 3 2 0
74
Ramamurthy
et nl.
Journal
oj Pain and Symptom Management
Table 3
Percent Pain Relief Following Neurolytic Block Phenol
Pain Relief (%) 2 4 12 24
wk wk wk wk
Cry0
o-19
20-39
40-79
80- 100
o- 19
6 7 8 8
5 2 1 1
2 2 1 1
4 4 4 4
12 12 12 12
Only 27% of the patients obtained significant pain relief with neurolytic blocks. This high failure rate (73%) indicates the problems of doing neurolytic blocks in chronic pain patients. All patients obtained significant pain relief for a very short period, but not long-term pain relief. Lloyd and others have reported median duration of 14-20 days of pain relief after cryogenic block. 2 In our study, after 2 wk, neither phenol nor cryo blocks produced good pain relief in a significant number of patients. The claimed advantages of cryogenic block are the lack of neuritis production because of the preservation of the connective tissue matrix and a second degree type of nerve injury with cryoneurolysis. There are significant problems associated with the use of cryo block. The large-sized probe and the needle can produce significant tissue trauma, which seemed to occur in the patient who developed neuritis. The technique takes a long time to perform and is very cumbersome because of all the equipment needed. The use of larger needles and more prolonged procedure with cryo causes more patient discomfort than when a phenol block is being done. Also, in order to produce the damage to the nerve, the ice ball produced by the cryoprobe should surround the nerve to produce the neurolysis.’ It is possible that the failures are due to the ice ball pushing the nerve away rather than enveloping it. In addition, the expense of the equipment is always a significant consideration. It is possible that the success rate could be improved by using an alternate type of cryo unit or cry0 probes. However, we feel that every possible attempt has been made to localize accurately the nerve for the neurolytic block. The needle we used was insulated by the plastic cannula, and the nerve was identified by using this insulated 12-gauge cannula and at-
20-39 0 0 0 0
40-79 1 1 1 1
80- 100 2 2 0 0
taching the nerve stimulator to the metal part of the needle to identify the nerve. Only after confirmation of the location of the tip of the needle was the needle removed and the cryo probe passed through the plastic cannula. Radiological confirmation of the location of the tip of the probe was also utilized whenever necessary. A recent double-blind, matched control study by Khiroya and Jones suggests that cryoanalgesia of the ilioinguinal nerve is ineffective in the control of pain after herniorrhaphy.4 This is in conflict with earlier results published by Wood and Lloyd using similar techniques. In our study, we have noted a lower success rate with cryoanalgesia than has been previously reported.*s6 We have no explanation for this occurrence at the present time. Phenol produces its neurolytic effect by denaturing the proteins of the axons. Phenol seems to produce equally good neurolytic block and is much simpler to use than cryoanalgesia. The solution tends to spread, and this may be helpful when accurate localization of the nerve may not be possible. There is a disadvantage when phenol is used close to the intervertebral foramen because of the possibility of the solution spreading into the epidural and subarachnoid space or even producing spinal cord damage. This may be an area where cryo block may be more beneficial because the physical damage is restricted to the site of application. In conclusion, pain relief with local anesthetic block does not consistently predict successful pain relief with neurolytic block. Neurolytic peripheral nerve blocks using the cryoseeker and/or 6% aqueous phenol were not very effective in the management of chronic pain. Further studies are needed to evaluate improved equipment for cryoanalgesia as well as increased concentration of phenol in the management of chronic pain to
Vk 4 No. 2 June 1989
Neurolytic Blocksfor Chronic Pain
improve the success rate of neurolytic peripheral nerve blocks. Both phenol and cryo blocks seem to help a limited number of patients. The phenol block is easier and less expensive to perform.
Acknowledw The authors are grateful to the Audie Murphy Veterans’ Administration Hospital and the Bexar County Hospital District for the use of their facilities to carry out this research. This research was supported by an Institutional Grant from the University of Texas Health Science Center at San Antonio.
References 1. Hannington-Kiff JG. A “cryoseeker” for percutaneous cryoanalgesia. Lancet 1978;11:816-817.
75
2. Lloyd JW, Barnard JDW, Glynn CJ. Cryoanalgesia: A new approach to pain relief. Lancet 1976;11:932. 3. Marsland AR, Ramamurthy S, Barnes J. Cryogenic damage to peripheral nerves and blood vesselsin the rat. Br J Anesth 1983;55:555-558. 4. Khiroya RC, Jones JG. Cryoanalgesia for pain after herniorrhaphy. Anesthesia 1986;41:73-76. 5. Rosen M. The measurement of pain. In: Harcus AW, Smith RB, Whittle BA, eds. Pain: New perspectives in measurement and management, Edinburgh: Churchill-Livingstone, 1977:13-20. 6. Wood KM. The use of phenol as a neurolytic agent: A review. Pain 1978;5:205-229. 7. Katz, J. Physicalmethods affecting neural activity. In: Scott, DB, McClure J, Wildsmith JAW, eds. Regional anesthesia 1884- 1984. Sodertalje, Sweden: ICM AB, 1984:82.
Journal
of Pain and Symptom Management
Vol. 4 No. 2 June 1989
Evaluation of Neurolytic Blocks Using Phenol and Cryogenic Block in the Management of Chronic Pain Somayaji Ramamurthy, MD, Nicolas E. Walsh, MD, Lawrence S. Schoenfeld, PhD and Joan Hoffman, RN University
of Texas Health Science Center, San Antonio,
Texas
Abstract This study compared the use of phenol and cryogenic blocksfor neurolysis in 28 patients. Patients were assigned randomly to receive peripheral nerve blocks with either phenol or cryoanalgesia. Si@ficantly more patients in the phenol group received 20% or greater relief at 2, 12, and 24 wk than patients in the cryogenic group. Only 27% of patients received signaficant relief, however, indicating that neurolytic blocks were not particularly effective even though local anesthetic blocks produced signaficant but temporary pain relief. J Pain Symptom Manage 1989;4:72-75.
Key Wonis Neurolytic nerve blocks, phenol, cryoanalgesia, chronic pain
Introduction Prolonged pain relief provided by neurolytic block is a very desirable modality in the management of chronic pain. When patients obtain temporary but significant relief of pain using local anesthetic agents, an attempt is made to provide prolonged or permanent pain relief using repeated blocks with local anesthetic agents. When this modality is not successful, various less invasive methods are tried before permanent interruption of nerve pathways using neurolytic blocks is considered. Chemical neurolysis using alcohol and phenol have been used with success, but there is a possibility of neuroma formation and neuritis. There are very few studies documenting the usefulness of
Addressreprint requests to: Somayaji Ramamurthy, MD, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78284. for publication: June 27, 1988
Accepted
0 U.S. Cancer Pain Relief Committee, 1989 Published by Elsevier, New York, New York
peripheral nerve blocks using phenol. Cryogenic block of the peripheral nerve has been reported to be useful in managing chronic pain’s* without producing neuritis or neuromas. There are no studies comparing the use of chemical neurolysis produced by phenol to a physical method of neurolytic block, such as that produced by a cryo probe. This study compares the effectiveness of neurolytic block of the peripheral somatic nerves using phenol and cryo probe block.
Methods Twenty-eight patients with chronic pain were recruited for the study. The mean age of patients in the phenol group was 59.7 yr with a range of 26-82 yr, and the mean age of the cryoanalgesia group was 53.8 yr with a range of 26-82 yr. Six were female, and 22 were male. This study was approved by the Institutional Review Board, and informed consent was obo&35-3924/891$3.50
Vol. 4 No. 2 June 1989
73
Neurolytic Blocks for Chronic Pain
tained before enrollment into the study. All patients had previously noted significant but temporary pain relief following local anesthetic blocks. Patients were randomly assigned either to the phenol group or the cryoanalgesia group. A nerve stimulator was utilized to identify the nerve. The phenol group patients received a nerve block using 6% aqueous phenol. Cryo block was performed by using a cryoseeker probe (1.6 mm x 180 mm) introduced through a 12-gauge plastic cannula. The probe was connected to the Cryo-Medic unit model MA300. Nitrous oxide was used to cool the probe, and the tissue temperatures were monitored by using a 23-gauge thermocouple connected to a temperature monitor. After the probe registered -20°C the cooling was continued for 1 min, and the probe was allowed to thaw for 1 min. This cycle was repeated three times.1p3*4 Technical adequacy of the neurolytic block was evaluated by physical findings of a corresponding area of numbness and/or weakness. Patients marked a IO-cm visual analog scale, which was used to determine pain relief, before and after the block and at 2-, 4-, 12-, and 24-wk follow-up visits.5 All patients were maintained on pretreatment medication regimens of nonsteroidal antiinflammatory drugs, tricyclic antidepressants, and other medications for systemic disease processes. Patients were monitored for side effects and complications during the study period. Four patients who did not receive pain relief with one technique received a neurolytic block with the other technique. The percentage of pain relief obtained was compared between the two groups using Fisher’s exact probability test. A P value of less than 0.05 was considered significant.
Results All patients demonstrated physical findings consistent with correct anatomical placement of the needle/probe for neurolytic block procedure. Seventeen patients were included in the phenol group, and 15 patients were included in the cryo group. Table 1 lists the various peripheral nerves that were blocked, and Table 2 shows the pain syndromes of patients receiving blocks. More patients in the phenol group experienced pain relief than the cryo group, when one is comparing 20% or greater relief (P <
Table 1 Types of Nerve Blocks Phenol Intercostal nerve* Tibia1 nerve* Neuroma* Myoneural Paravertebral somatic root block Facet* Brachial plexus Supraorbital nerve Coccygeal nerve Accessory nerve *One patient in each group received phenol block.
6 1 3 3 0 1 0 1 1 1
Cry0 3 3 3 0 3 2 1 0 0 0
both cryo and
0.05) (Table 3) at 2, 12 and 24 wk. At higher percentages of relief, results were not statistically significant. One patient in the cryo group developed neuritis following a paravertebral somatic nerve block. Two patients (13%) were lost to follow-up after 4 wk in the cryo group, and three patients (12%) were lost to follow-up in the phenol group. LliScuSSti Wood,‘j noting the lack of documented studies evaluating phenol for peripheral block, stated, “It is impossible on this information to evaluate the use of phenol in peripheral nerve blocks for pain. One can merely say that it has been done. The likelihood of benefit and percentage of risk is not known.” In this study, neurolytic blocks were not particularly effective, even though local anesthetic blocks produced significant but temporary pain relief in all patients. Hypesthesia was noted in the distribution when nerves with cutaneous innervation were blocked. Thus, we feel that the failure to relieve pain is not due to the lack of correct anatomical placement of the needle.
Table 2
Pain Syndromes Phenol Neuralgias Cancer Facet Musculoskeletal
7 5 1 4
CT 10 3 2 0
74
Ramamurthy
et nl.
Journal
oj Pain and Symptom Management
Table 3
Percent Pain Relief Following Neurolytic Block Phenol
Pain Relief (%) 2 4 12 24
wk wk wk wk
Cry0
o-19
20-39
40-79
80- 100
o- 19
6 7 8 8
5 2 1 1
2 2 1 1
4 4 4 4
12 12 12 12
Only 27% of the patients obtained significant pain relief with neurolytic blocks. This high failure rate (73%) indicates the problems of doing neurolytic blocks in chronic pain patients. All patients obtained significant pain relief for a very short period, but not long-term pain relief. Lloyd and others have reported median duration of 14-20 days of pain relief after cryogenic block. 2 In our study, after 2 wk, neither phenol nor cryo blocks produced good pain relief in a significant number of patients. The claimed advantages of cryogenic block are the lack of neuritis production because of the preservation of the connective tissue matrix and a second degree type of nerve injury with cryoneurolysis. There are significant problems associated with the use of cryo block. The large-sized probe and the needle can produce significant tissue trauma, which seemed to occur in the patient who developed neuritis. The technique takes a long time to perform and is very cumbersome because of all the equipment needed. The use of larger needles and more prolonged procedure with cryo causes more patient discomfort than when a phenol block is being done. Also, in order to produce the damage to the nerve, the ice ball produced by the cryoprobe should surround the nerve to produce the neurolysis.’ It is possible that the failures are due to the ice ball pushing the nerve away rather than enveloping it. In addition, the expense of the equipment is always a significant consideration. It is possible that the success rate could be improved by using an alternate type of cryo unit or cry0 probes. However, we feel that every possible attempt has been made to localize accurately the nerve for the neurolytic block. The needle we used was insulated by the plastic cannula, and the nerve was identified by using this insulated 12-gauge cannula and at-
20-39 0 0 0 0
40-79 1 1 1 1
80- 100 2 2 0 0
taching the nerve stimulator to the metal part of the needle to identify the nerve. Only after confirmation of the location of the tip of the needle was the needle removed and the cryo probe passed through the plastic cannula. Radiological confirmation of the location of the tip of the probe was also utilized whenever necessary. A recent double-blind, matched control study by Khiroya and Jones suggests that cryoanalgesia of the ilioinguinal nerve is ineffective in the control of pain after herniorrhaphy.4 This is in conflict with earlier results published by Wood and Lloyd using similar techniques. In our study, we have noted a lower success rate with cryoanalgesia than has been previously reported.*s6 We have no explanation for this occurrence at the present time. Phenol produces its neurolytic effect by denaturing the proteins of the axons. Phenol seems to produce equally good neurolytic block and is much simpler to use than cryoanalgesia. The solution tends to spread, and this may be helpful when accurate localization of the nerve may not be possible. There is a disadvantage when phenol is used close to the intervertebral foramen because of the possibility of the solution spreading into the epidural and subarachnoid space or even producing spinal cord damage. This may be an area where cryo block may be more beneficial because the physical damage is restricted to the site of application. In conclusion, pain relief with local anesthetic block does not consistently predict successful pain relief with neurolytic block. Neurolytic peripheral nerve blocks using the cryoseeker and/or 6% aqueous phenol were not very effective in the management of chronic pain. Further studies are needed to evaluate improved equipment for cryoanalgesia as well as increased concentration of phenol in the management of chronic pain to
Vk 4 No. 2 June 1989
Neurolytic Blocksfor Chronic Pain
improve the success rate of neurolytic peripheral nerve blocks. Both phenol and cryo blocks seem to help a limited number of patients. The phenol block is easier and less expensive to perform.
Acknowledw The authors are grateful to the Audie Murphy Veterans’ Administration Hospital and the Bexar County Hospital District for the use of their facilities to carry out this research. This research was supported by an Institutional Grant from the University of Texas Health Science Center at San Antonio.
References 1. Hannington-Kiff JG. A “cryoseeker” for percutaneous cryoanalgesia. Lancet 1978;11:816-817.
75
2. Lloyd JW, Barnard JDW, Glynn CJ. Cryoanalgesia: A new approach to pain relief. Lancet 1976;11:932. 3. Marsland AR, Ramamurthy S, Barnes J. Cryogenic damage to peripheral nerves and blood vesselsin the rat. Br J Anesth 1983;55:555-558. 4. Khiroya RC, Jones JG. Cryoanalgesia for pain after herniorrhaphy. Anesthesia 1986;41:73-76. 5. Rosen M. The measurement of pain. In: Harcus AW, Smith RB, Whittle BA, eds. Pain: New perspectives in measurement and management, Edinburgh: Churchill-Livingstone, 1977:13-20. 6. Wood KM. The use of phenol as a neurolytic agent: A review. Pain 1978;5:205-229. 7. Katz, J. Physicalmethods affecting neural activity. In: Scott, DB, McClure J, Wildsmith JAW, eds. Regional anesthesia 1884- 1984. Sodertalje, Sweden: ICM AB, 1984:82.