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A troubleshooting guide to the subcutaneous epidural implantable reservoir
lbl. I No. 4 Fall 1986
Journal of Pain and Symptom Management
217
Special Article
A Troubleshooting Guide to the Subcutaneous Epidural Implantable Reservoir Steven D. W a l d m a n , G a r y S. Feldstein, a n d M a r k L. Allen
Kansas City Pain Consortium, University of Missouri-Kansas City
Abstract The use of intraspinal narcotics to relieve pain of malignant origin represents a great advance in cancer pain management, hnplantation of subcutaneous intraspinal narcotic delivery systems for pain relief has been used with minimal complications. Occasionally problems arise. The purpose of this article is to review the various causes of reservior failure, their, diagnosis, amt the methods to correct them. J Pain Sympt Manag 1986;1:217-222. Key Words Intraspinal narcotics, implantable delivery systems, complications.intraspinal narcotics, complications-implantable delivery systems
T h e use o f intraspinal narcotics to relieve pain o f malignant origin represents a great advance in c a n c e r pain m a n a g e m e n t . For patients with a relatively short life expectancy, delivery of intraspinal narcotics may be carried out using an as-needed single-shot technique or via a s i m p l e p e r c u t a n e o u s catheter. 1 For patients with a longer life expectancy, implantation o f subcutaneous delivery systems has been advocated to avoid complications including infection and catheter breakage. 2-5 For the most part these implantable resen'oirs functi'on without problems; however occasional difficulties arise. T h e purpose o f this article is to review the various causes o f reservoir failure, their diagnosis, and the methods used to correct them. The recomendations presented are intended primarily for silastic dome/catheter combinations such as the Radovan (Fig 1) and Omaya resen'oirs. However, comments regarding distal catheter failure may be applicable to the implantable continuous infusion pump.
Address reprint requests to: Steven D. Waldman, MD, Director, Kansas City Pain Consortium, 8301 State Line, Kansas Cit); MO 64114 Acceptedfor publication: April 7, 1986
Fig. 1. Radovan Implantable Reservoir and Catheter for delivery of epidural morphine sulfate.
Tile various causes o f reselwoir failure will be divided into categories based on the patient's perception of the problem rather than on the physician's perception because, as with all areas 9o f pain management, success or failure must be defined in terms o f the patient's perception o f the adequacy o f pain relief. When the patient complains that his reservoir "doesn't work" the first step is to ascertain whether or not the reser~'oir is functioning (Fig 2). This is accomplished by the injection o f a
218
Waldman, et al.
Journal of Pain and Symptom Management
providing pain relief. This differential diagnosis can be most easily accomplished by dividing the patient's c o m p l a i n t regarding the reservoir into one o f the categories listed in Table 2 a n d discussed belong:
Table 2 Categories of Reservoir Failure from the Patient's Perspective Fig. 2. Normal metrizamide injection of subcutaneous epidural implantable reservoir.
local anesthetic c a p a b l e ' o f p r o d u c i n g a dense m o t o r and sensory block through the reservior. A suggested protocol is outlined in Table 1. It is i m p o r t a n t to note that because o f previous chemotherapy, venous access may be a problem. An IV site should be secured a n d a fluid load carefully administered p r i o r to injection o f local anesthetic via the reservoir. T h e r e may be pre-existing cardiac c o m p r o m i s e f r o m p r i o r c h e m o t h e r a p y or o t h e r systemic diseases (renal insufficiency, adrenal suppression, etc). T h e s e problems must be considered in the administration o f a fluid load and in the use o f vasopressors. Obviously, o n e must observe the same precautions a n d vigilance used when administering an anesthetic in the o p e r a t i n g suite. A total lack o f m o t o r and sensory deficits in a p p r o p r i a t e d e r m a t o m a l distribution indicates that in fact the reser~'oir is not functioning properly. T h e next step is to d e t e r m i n e the specific reason why the injection o f the rese~'oir is not
Table 1 Protocol for Injection of Subcutaneous Implanted Reservoirs with Local Anesthestics Step 1. The reservoir site is prepped with Betadine. Step 2. A local anesthetic suitable for epidural anesthesia and capable of producing dense motor and sensory block is selected: Step 3. A volume of local anesthetic necessary to produce sensory and motor blockade in the painful area is the given via the reservoir. Step 4. The patient is then observed for motor and sensory block in the appropriate dermatomes for the volume of local anesthetic given. The onset of observed motor and sensory deficit should occur in the amount of time appropriate for a given local anesthetic and last for an appropriate duration.
Category#1
"The reservoir never worked:'
Category #2
"The reservoir works intermittently:'
Category #3 "The reservoir worked perfectly and suddenly stopped working" Category #4 "The reservoir doesn't work as well as it used to:' Category#5 injected:'
"It hurts when the reservoir is
Category "The Reservoir Never Worked" I f p r o p e r patient selection a n d pre-implantation trials o f intraspinal narcotics are carried out, this c o m p l a i n t should rarely be encountered by the clinician. 6 In the patient who voices this complain, the following p r o b l e m s may exist: 9 T h e reservoir was i m p r o p e r l y injected. 9 T h e r e is proximal c o m p o n e n t failure. 9 T h e distal c o m p o n e n t is not in the p r o p e r place. 9 T h e patient is unable to accurately assess pain relief. T h e p r o b l e m o f i m p r o p e r injection should be limited to those unfamiliar with the technique (Fig 3). P r o p e r injection may be m a d e " m o r e difficult by p o o r p l a c e m e n t o f the reservoir dome, (ie, too m u c h tissue overlying the dome), generalized e d e m a o f s u r r o u n d i n g tissue or h e m a t o m a f r o m surgical trauma. Simple inspection o f the reservoir d o m e site will reveal if the reservoir has b e e n missed. The following checklist should be considered: 9 Is the needle p u n c t u r e site n e a r the palpated dome? 9 Was there i m m e d i a t e resistance to the injection? 9 Was there pain locally as the injection progressed? 9 Is there a collection o f fluid around the d o m e that was not there p r i o r to injection?
Ibl. I No. 4 Fall 1986
Subcutaneous Epidural Implantable Reservoir
Fig. 3. Improper reservoir injection technique. Metrazamide inadvertently injected outside of reservoir with extravasation around reservoir dome and filling of pocket.
m
219
9 Was there a gradual onset o f numbness at the reservoir site? I f the answer to all the above questions is yes, proximal reservoir failure should be consid9 ered. I f the answer to all the above questions is no, distal catheter malfunction should be considered to be the likely cause o f reservoir failure. T h e following checklist should be considered: 9 Was there a s u d d e n inability to inject o r m a r k e d increase in resistance after injection o f the volume necessary to fill only the reservoir a n d catheter? This varies d e p e n d i n g on reservoir type a n d catheter but is usually 1.5 to 2.0 ml. 9 Was there no accumulation of fluid a r o u n d the reservoir? 9 Was there no n u m b n e s s around the reser~'oir? I f the answer to the above is yes, failure o f the distal catheter is likely. I f distal catheter malfunction is again suspected, injection o f the reservoir and catheter with metrizamide may aid in locating the distal catheter tip.
Category #2--"The Reservoir Works Intermittently" Fig. 4. Proximal component failure. Metrizamide extravasation localized around reservoir dome with some contrast filling distal catheter.
9 Is there an area o f n u m b n e s s a r o u n d the injection site? I f the answer to any o f the above is yes, o n e should assume the reservoir was i m p r o p e r l y injected. I f the reservoir can still be palpated, a repeat injection o f local anesthetic should be carried out by s o m e o n e skilled in reservoir injection. I f the answer is no, either proximal reservoir failure o r i m p r o p e r p l a c e m e n t o f the distal catheter is likely to exist. Proximal reser~'oir failure occurs when the reservoir c o m p o n e n t a n d the proximal catheter's end either leal~s o r b e c o m e s disconnec~ted (Fig 4). T h e following checklist should be considered: 9 Did the reservoir inject easier than usual initially? 9 Was there a sudden increase in resistance to injection c o r r e s p o n d i n g to accumulation o f fluid a r o u n d the reservoir?
In patients with this complaint, the following p r o b l e m s may exist: 9 T h e reservoir was injected improperly. * T h e distal catheter may move in and out o f the epidural space as the patient's position changes. 9 T h e catheter intermittently kinks as position changes. 9 T h e r e are intercurrent behavioral or physiologic p r o b l e m s that r e n d e r the p a t i e n t unable to assess the degree of pain relief. I f the perceived reservoir failure is a relatively u n c o m m o n occurence, reassurance may be all that is required. However, if the patient perceives the intermittent failure o f pain relief as unacceptable, evaluation is indicated. Step 1. T h e local anesthetic trial injections should be p e r f o r m e d as outlined in Table 1. T h e patient should be placed in the position that he is normally placed in during his reservoir injection. O b s e r v a t i o n o f a p p r o p r i a t e m o t o r and sensory deficit assures that the reservoir is in fact functioning properly. Step 2. Ascertain the variable factors that may account for the patient's perception o f lack o f pain relief. A reservoir injection diary noting
220
IValdman, et al.
the person injecting, the time o f injection, and the patient positions may help identify the variable factor responsible for the lack o f pain relief. In examining the variable factors, the following should be considered: 9 The person injecting may not have the technical ability to successfully inject the reservoir. 9 T h e r e may be a behavioral conflict between the individual injecting the resera'oir and the p~itient. 9 The reservoir may occasionally be injected earlier than normal, and the duration .of intraspinal narcotics may not be adequate to provide pain relief. 9 T h e patient may occasionally be in a different position during injection allowing the distal catheter to move out o f the epidural space. 9 T h e patient suffers intermittent alterations in physiologic parameters such as hyperkalemia, hyponatremia, azotemia, increased intracranial pressure, etc which r e n d e r the patient unable to assess the a m o u n t o f pain relief. Obviously identification o f the variable factor responsible for the intermittent reservoir failure will allow the situation to be corrected.
Category #3--"The Reservoir Worked Perfectly and Szutdenly Stopped Working" In patients with this complaint, the following problems may exist: 9 The reservoir was injected improperly on an ongoing basis. 9 T h e r e has been proximal catheter failure. 9 T h e distal catheter has slipped out o f the epidural space. 9 A new batch o f prefilled syringes was prepared with the incorrect a m o u n t o f narcotic. 9 T h e r e has been an intercurrent change in the patient's condition. T h e first three problems in Category #3 need no explanation as the), have been discussed previously. T h e fourth problem occurs more often than it should. It is important that prescriptions for prefilled syringes be written clearly, indicating not only the mg dosage o f narcotic, but the volume o f diluent as well. Each syringe should be labeled with this information by the dispensing pharmacist.
Journal of Pain and Symptom Management
It is important to r e m e m b e r that in most patients with implanted reser~'oirs, their disease process is dynamic rather than static. Intercurrent illness such as renal colic, new vertebral compression fractures, metabolic derangements, and progression of metastatic disease may r e n d e r intraspinal narcotics inefi fective at that point in the patient's illness. It is incumbent on the specialist in pain management to assess the condition o f the patient as well as the condition o f the reservoir. Failure to do this can only result in less than optimal care.
Category #4--"The Reservoir Is
Gradually Becoming Less Effective" In patients with this complaint, the following problems may exist: 9 T h e reservoir d o m e is leaking from repeated needle puncture allowing part o f the total volume to extravasate. 9 A fibrous fistulous tract along the catheter has developed allowing part o f the volume injected to spread retrograde a r o u n d the catheter. 9 Tolerance to the injected narcotic develops. O u r experience has shown that the life o f the reservoir d o m e relative to leakage is variable. T h e following factors a p p e a r to prolong the time before replacement for leakage: 9 Use the smallest needle possible to accomplish the injection. We r e c o m m e n d nothing larger than a 23-ga. 9 Maximize the dose o f narcotic and diluant that will allow the reservoir to be injected as infrequently as possible. 9 Never use a needle that has been used to draw up medications through a r u b b e r topped vial, as this dulls the needle. Following these guidelines, it is not u n c o m m o n for the Radovan reservoir to allow over 1,000 injections before leakage necessitates replacement. It may be possible to delay reservoir d o m e replacement by increasing the total mg dosage o f narcotics as well as the total volume o f diluent. Should this b e c o m e ineffective the d o m e can be replaced u n d e r local anesthesia on an outpatient basis. Fibrous tract formation with retrograde leakage is a more serious problem to manage (Fig 5). This is especially devastating in patients with subarachnoid catheters because the CSF tracks retrograde along the catheter eventually s u r r o u n d i n g the reservoir
Vol. 1 No. 4 Fall 1986
Subcutaneous Epidural lmplantable Reservoir
dome. This makes location o f the d o m e in the CSF filled pocket next to impossible. Obvio/asly this presents an increased risk o f CNS infection. In our experience, treatment of this problem necessitates complete removal o f the entire delivery system and surgical closure o f the dural rent. Pain control may be difficult during the period necessary for healing to occur; it can usually be managed by increasing the total mg dose o f narcotic and volume o f diluant.
Fig. 5. Fibrous tract formation with retrograde leakage. Metrazamide leaking around distal catheter flowing retrograde to surround reservoir dome. Tolerance occurs to a greater or lesser extent in all patients receiving intraspinal narcotics. A gradual titration upward in the total mg dosage o f narcotic should be utilized as pain relief gradually becomes suboptimal. Increasing the frequency o f injection o f the reser~'oir should be avoided as long as possible as it will shorten the reservoir d o m e life expectancy. As small increases in the total mg dosage o f narcotics become ineffective in controlling the pain, injection o f preservative-free lidocaine and methylprednisolone acetate via the reservoir may reverse the tolerance (unpublished observation). After injection o f the lidocainelmethylprednisolone acetate combination, it may be possible to decrease the total mg dose o f narcotics needed to provide pain relief.
Category #5m"It Hurts When The Reservoir Is Injected" In patients with this complaint, the following problems may exist: * T h e surgical trauma is not healed. 9 T h e deliver)' system is infected. 9 T h e r e has been a change in compliance o f the
221
epidural or subarachnoid space. * Non preservative-free narcotic has been used. T h e patient with a newly implanted reservoir should be warned that the first few injections may be painful. They should be reassured that as the surgical site heals the pain on injection will decrease. In the i m m u n o c o m p r o m i s e d patient, the risk o f infection is ever present. T h e complaint o f pain o n injection should be taken seriously, and careful inspection o f the reservoir site is mandatory. Classical systemic signs o f infection may be masked by steroids, c h e m o t h e r a p y induced neutropenia, or the patient's debilitated condition; therefore, the index o f suspicion must be high. As tumor, vertebral compression fracture, or abscess o b l i t e r a t e the e p i d u r a l space, a decrease in compliance may result. This may produce pain as the rapid increase in epidural pressure during injection occurs. As stated earlier, the specialist in pain management must assess not only the condition of the reservoir, but the condition o f the patient as well. Some patients have complained o f pain on injection o f small amounts o f preservative containing m o r p h i n e diluted in a large volume o f preservative free saline via their reservoir. In such patients, it may be necessary to use a preservative free preparation such as D u r a m o r p h despite its greater cost to the patient. W h e t h e r the lack o f preservatives in such solutions has any practical advantage relative to the cost/benefit analysis remains to be seen. In summary, delivery o f intraspinal narcotics via a subcutaneous implanted reservoir system has been o f great value in cancer pain management. If difficulties occur, a rational approach to troubleshooting should allow an easy arid timely solution to the problem as well as provide comfort for the patient.
References 1. Zenz M, Schappler-Scheele B, Neuhaus R, Hilfrich J. Long-term peridural morphine analgesia in cancer pain. Lancet 1981;1:91. 2. Poletti CE, Cohen AM, Todd DP, Ojemann RG, Sweet WH, Zervus NT. Cancer pain relieved by long-term epidural morphine with permanent indwelling systems for self administration. J. Neurosurg 1981;55:581-584. 3. Coombs DW, Saunders RL, Schwberger CL, Pageau MG. Epidural narcotic infusion reservoir: implantation technique and efficacy. Anesthesiology 1982; 56:469-473.
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Waldman, et al.
4. Krames ES, GershowJ, Glassberg A, et al. Continuous infusion of spinally administered narcotics for the relief of pain due to malignant disorders. Cancer 1985;56:516-520. 5. Onfrio BM, Yasch TL, Arnold PR. Continuous low-dose intrathecal morphine administration in the treatment of pain of malignant origin. Mayo Clin Proc 1881;56:516-520. 6. Waldman SD, Feldstein GS, Allen ML. Selection of patients for implantable intraspinal narcotic delivery systems. Anesth Analg 1986;in press.
Journal of Pain and Symptom Management
Journal of Pain and Symptom Management
217
Special Article
A Troubleshooting Guide to the Subcutaneous Epidural Implantable Reservoir Steven D. W a l d m a n , G a r y S. Feldstein, a n d M a r k L. Allen
Kansas City Pain Consortium, University of Missouri-Kansas City
Abstract The use of intraspinal narcotics to relieve pain of malignant origin represents a great advance in cancer pain management, hnplantation of subcutaneous intraspinal narcotic delivery systems for pain relief has been used with minimal complications. Occasionally problems arise. The purpose of this article is to review the various causes of reservior failure, their, diagnosis, amt the methods to correct them. J Pain Sympt Manag 1986;1:217-222. Key Words Intraspinal narcotics, implantable delivery systems, complications.intraspinal narcotics, complications-implantable delivery systems
T h e use o f intraspinal narcotics to relieve pain o f malignant origin represents a great advance in c a n c e r pain m a n a g e m e n t . For patients with a relatively short life expectancy, delivery of intraspinal narcotics may be carried out using an as-needed single-shot technique or via a s i m p l e p e r c u t a n e o u s catheter. 1 For patients with a longer life expectancy, implantation o f subcutaneous delivery systems has been advocated to avoid complications including infection and catheter breakage. 2-5 For the most part these implantable resen'oirs functi'on without problems; however occasional difficulties arise. T h e purpose o f this article is to review the various causes o f reservoir failure, their diagnosis, and the methods used to correct them. The recomendations presented are intended primarily for silastic dome/catheter combinations such as the Radovan (Fig 1) and Omaya resen'oirs. However, comments regarding distal catheter failure may be applicable to the implantable continuous infusion pump.
Address reprint requests to: Steven D. Waldman, MD, Director, Kansas City Pain Consortium, 8301 State Line, Kansas Cit); MO 64114 Acceptedfor publication: April 7, 1986
Fig. 1. Radovan Implantable Reservoir and Catheter for delivery of epidural morphine sulfate.
Tile various causes o f reselwoir failure will be divided into categories based on the patient's perception of the problem rather than on the physician's perception because, as with all areas 9o f pain management, success or failure must be defined in terms o f the patient's perception o f the adequacy o f pain relief. When the patient complains that his reservoir "doesn't work" the first step is to ascertain whether or not the reser~'oir is functioning (Fig 2). This is accomplished by the injection o f a
218
Waldman, et al.
Journal of Pain and Symptom Management
providing pain relief. This differential diagnosis can be most easily accomplished by dividing the patient's c o m p l a i n t regarding the reservoir into one o f the categories listed in Table 2 a n d discussed belong:
Table 2 Categories of Reservoir Failure from the Patient's Perspective Fig. 2. Normal metrizamide injection of subcutaneous epidural implantable reservoir.
local anesthetic c a p a b l e ' o f p r o d u c i n g a dense m o t o r and sensory block through the reservior. A suggested protocol is outlined in Table 1. It is i m p o r t a n t to note that because o f previous chemotherapy, venous access may be a problem. An IV site should be secured a n d a fluid load carefully administered p r i o r to injection o f local anesthetic via the reservoir. T h e r e may be pre-existing cardiac c o m p r o m i s e f r o m p r i o r c h e m o t h e r a p y or o t h e r systemic diseases (renal insufficiency, adrenal suppression, etc). T h e s e problems must be considered in the administration o f a fluid load and in the use o f vasopressors. Obviously, o n e must observe the same precautions a n d vigilance used when administering an anesthetic in the o p e r a t i n g suite. A total lack o f m o t o r and sensory deficits in a p p r o p r i a t e d e r m a t o m a l distribution indicates that in fact the reser~'oir is not functioning properly. T h e next step is to d e t e r m i n e the specific reason why the injection o f the rese~'oir is not
Table 1 Protocol for Injection of Subcutaneous Implanted Reservoirs with Local Anesthestics Step 1. The reservoir site is prepped with Betadine. Step 2. A local anesthetic suitable for epidural anesthesia and capable of producing dense motor and sensory block is selected: Step 3. A volume of local anesthetic necessary to produce sensory and motor blockade in the painful area is the given via the reservoir. Step 4. The patient is then observed for motor and sensory block in the appropriate dermatomes for the volume of local anesthetic given. The onset of observed motor and sensory deficit should occur in the amount of time appropriate for a given local anesthetic and last for an appropriate duration.
Category#1
"The reservoir never worked:'
Category #2
"The reservoir works intermittently:'
Category #3 "The reservoir worked perfectly and suddenly stopped working" Category #4 "The reservoir doesn't work as well as it used to:' Category#5 injected:'
"It hurts when the reservoir is
Category "The Reservoir Never Worked" I f p r o p e r patient selection a n d pre-implantation trials o f intraspinal narcotics are carried out, this c o m p l a i n t should rarely be encountered by the clinician. 6 In the patient who voices this complain, the following p r o b l e m s may exist: 9 T h e reservoir was i m p r o p e r l y injected. 9 T h e r e is proximal c o m p o n e n t failure. 9 T h e distal c o m p o n e n t is not in the p r o p e r place. 9 T h e patient is unable to accurately assess pain relief. T h e p r o b l e m o f i m p r o p e r injection should be limited to those unfamiliar with the technique (Fig 3). P r o p e r injection may be m a d e " m o r e difficult by p o o r p l a c e m e n t o f the reservoir dome, (ie, too m u c h tissue overlying the dome), generalized e d e m a o f s u r r o u n d i n g tissue or h e m a t o m a f r o m surgical trauma. Simple inspection o f the reservoir d o m e site will reveal if the reservoir has b e e n missed. The following checklist should be considered: 9 Is the needle p u n c t u r e site n e a r the palpated dome? 9 Was there i m m e d i a t e resistance to the injection? 9 Was there pain locally as the injection progressed? 9 Is there a collection o f fluid around the d o m e that was not there p r i o r to injection?
Ibl. I No. 4 Fall 1986
Subcutaneous Epidural Implantable Reservoir
Fig. 3. Improper reservoir injection technique. Metrazamide inadvertently injected outside of reservoir with extravasation around reservoir dome and filling of pocket.
m
219
9 Was there a gradual onset o f numbness at the reservoir site? I f the answer to all the above questions is yes, proximal reservoir failure should be consid9 ered. I f the answer to all the above questions is no, distal catheter malfunction should be considered to be the likely cause o f reservoir failure. T h e following checklist should be considered: 9 Was there a s u d d e n inability to inject o r m a r k e d increase in resistance after injection o f the volume necessary to fill only the reservoir a n d catheter? This varies d e p e n d i n g on reservoir type a n d catheter but is usually 1.5 to 2.0 ml. 9 Was there no accumulation of fluid a r o u n d the reservoir? 9 Was there no n u m b n e s s around the reser~'oir? I f the answer to the above is yes, failure o f the distal catheter is likely. I f distal catheter malfunction is again suspected, injection o f the reservoir and catheter with metrizamide may aid in locating the distal catheter tip.
Category #2--"The Reservoir Works Intermittently" Fig. 4. Proximal component failure. Metrizamide extravasation localized around reservoir dome with some contrast filling distal catheter.
9 Is there an area o f n u m b n e s s a r o u n d the injection site? I f the answer to any o f the above is yes, o n e should assume the reservoir was i m p r o p e r l y injected. I f the reservoir can still be palpated, a repeat injection o f local anesthetic should be carried out by s o m e o n e skilled in reservoir injection. I f the answer is no, either proximal reservoir failure o r i m p r o p e r p l a c e m e n t o f the distal catheter is likely to exist. Proximal reser~'oir failure occurs when the reservoir c o m p o n e n t a n d the proximal catheter's end either leal~s o r b e c o m e s disconnec~ted (Fig 4). T h e following checklist should be considered: 9 Did the reservoir inject easier than usual initially? 9 Was there a sudden increase in resistance to injection c o r r e s p o n d i n g to accumulation o f fluid a r o u n d the reservoir?
In patients with this complaint, the following p r o b l e m s may exist: 9 T h e reservoir was injected improperly. * T h e distal catheter may move in and out o f the epidural space as the patient's position changes. 9 T h e catheter intermittently kinks as position changes. 9 T h e r e are intercurrent behavioral or physiologic p r o b l e m s that r e n d e r the p a t i e n t unable to assess the degree of pain relief. I f the perceived reservoir failure is a relatively u n c o m m o n occurence, reassurance may be all that is required. However, if the patient perceives the intermittent failure o f pain relief as unacceptable, evaluation is indicated. Step 1. T h e local anesthetic trial injections should be p e r f o r m e d as outlined in Table 1. T h e patient should be placed in the position that he is normally placed in during his reservoir injection. O b s e r v a t i o n o f a p p r o p r i a t e m o t o r and sensory deficit assures that the reservoir is in fact functioning properly. Step 2. Ascertain the variable factors that may account for the patient's perception o f lack o f pain relief. A reservoir injection diary noting
220
IValdman, et al.
the person injecting, the time o f injection, and the patient positions may help identify the variable factor responsible for the lack o f pain relief. In examining the variable factors, the following should be considered: 9 The person injecting may not have the technical ability to successfully inject the reservoir. 9 T h e r e may be a behavioral conflict between the individual injecting the resera'oir and the p~itient. 9 The reservoir may occasionally be injected earlier than normal, and the duration .of intraspinal narcotics may not be adequate to provide pain relief. 9 T h e patient may occasionally be in a different position during injection allowing the distal catheter to move out o f the epidural space. 9 T h e patient suffers intermittent alterations in physiologic parameters such as hyperkalemia, hyponatremia, azotemia, increased intracranial pressure, etc which r e n d e r the patient unable to assess the a m o u n t o f pain relief. Obviously identification o f the variable factor responsible for the intermittent reservoir failure will allow the situation to be corrected.
Category #3--"The Reservoir Worked Perfectly and Szutdenly Stopped Working" In patients with this complaint, the following problems may exist: 9 The reservoir was injected improperly on an ongoing basis. 9 T h e r e has been proximal catheter failure. 9 T h e distal catheter has slipped out o f the epidural space. 9 A new batch o f prefilled syringes was prepared with the incorrect a m o u n t o f narcotic. 9 T h e r e has been an intercurrent change in the patient's condition. T h e first three problems in Category #3 need no explanation as the), have been discussed previously. T h e fourth problem occurs more often than it should. It is important that prescriptions for prefilled syringes be written clearly, indicating not only the mg dosage o f narcotic, but the volume o f diluent as well. Each syringe should be labeled with this information by the dispensing pharmacist.
Journal of Pain and Symptom Management
It is important to r e m e m b e r that in most patients with implanted reser~'oirs, their disease process is dynamic rather than static. Intercurrent illness such as renal colic, new vertebral compression fractures, metabolic derangements, and progression of metastatic disease may r e n d e r intraspinal narcotics inefi fective at that point in the patient's illness. It is incumbent on the specialist in pain management to assess the condition o f the patient as well as the condition o f the reservoir. Failure to do this can only result in less than optimal care.
Category #4--"The Reservoir Is
Gradually Becoming Less Effective" In patients with this complaint, the following problems may exist: 9 T h e reservoir d o m e is leaking from repeated needle puncture allowing part o f the total volume to extravasate. 9 A fibrous fistulous tract along the catheter has developed allowing part o f the volume injected to spread retrograde a r o u n d the catheter. 9 Tolerance to the injected narcotic develops. O u r experience has shown that the life o f the reservoir d o m e relative to leakage is variable. T h e following factors a p p e a r to prolong the time before replacement for leakage: 9 Use the smallest needle possible to accomplish the injection. We r e c o m m e n d nothing larger than a 23-ga. 9 Maximize the dose o f narcotic and diluant that will allow the reservoir to be injected as infrequently as possible. 9 Never use a needle that has been used to draw up medications through a r u b b e r topped vial, as this dulls the needle. Following these guidelines, it is not u n c o m m o n for the Radovan reservoir to allow over 1,000 injections before leakage necessitates replacement. It may be possible to delay reservoir d o m e replacement by increasing the total mg dosage o f narcotics as well as the total volume o f diluent. Should this b e c o m e ineffective the d o m e can be replaced u n d e r local anesthesia on an outpatient basis. Fibrous tract formation with retrograde leakage is a more serious problem to manage (Fig 5). This is especially devastating in patients with subarachnoid catheters because the CSF tracks retrograde along the catheter eventually s u r r o u n d i n g the reservoir
Vol. 1 No. 4 Fall 1986
Subcutaneous Epidural lmplantable Reservoir
dome. This makes location o f the d o m e in the CSF filled pocket next to impossible. Obvio/asly this presents an increased risk o f CNS infection. In our experience, treatment of this problem necessitates complete removal o f the entire delivery system and surgical closure o f the dural rent. Pain control may be difficult during the period necessary for healing to occur; it can usually be managed by increasing the total mg dose o f narcotic and volume o f diluant.
Fig. 5. Fibrous tract formation with retrograde leakage. Metrazamide leaking around distal catheter flowing retrograde to surround reservoir dome. Tolerance occurs to a greater or lesser extent in all patients receiving intraspinal narcotics. A gradual titration upward in the total mg dosage o f narcotic should be utilized as pain relief gradually becomes suboptimal. Increasing the frequency o f injection o f the reser~'oir should be avoided as long as possible as it will shorten the reservoir d o m e life expectancy. As small increases in the total mg dosage o f narcotics become ineffective in controlling the pain, injection o f preservative-free lidocaine and methylprednisolone acetate via the reservoir may reverse the tolerance (unpublished observation). After injection o f the lidocainelmethylprednisolone acetate combination, it may be possible to decrease the total mg dose o f narcotics needed to provide pain relief.
Category #5m"It Hurts When The Reservoir Is Injected" In patients with this complaint, the following problems may exist: * T h e surgical trauma is not healed. 9 T h e deliver)' system is infected. 9 T h e r e has been a change in compliance o f the
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epidural or subarachnoid space. * Non preservative-free narcotic has been used. T h e patient with a newly implanted reservoir should be warned that the first few injections may be painful. They should be reassured that as the surgical site heals the pain on injection will decrease. In the i m m u n o c o m p r o m i s e d patient, the risk o f infection is ever present. T h e complaint o f pain o n injection should be taken seriously, and careful inspection o f the reservoir site is mandatory. Classical systemic signs o f infection may be masked by steroids, c h e m o t h e r a p y induced neutropenia, or the patient's debilitated condition; therefore, the index o f suspicion must be high. As tumor, vertebral compression fracture, or abscess o b l i t e r a t e the e p i d u r a l space, a decrease in compliance may result. This may produce pain as the rapid increase in epidural pressure during injection occurs. As stated earlier, the specialist in pain management must assess not only the condition of the reservoir, but the condition o f the patient as well. Some patients have complained o f pain on injection o f small amounts o f preservative containing m o r p h i n e diluted in a large volume o f preservative free saline via their reservoir. In such patients, it may be necessary to use a preservative free preparation such as D u r a m o r p h despite its greater cost to the patient. W h e t h e r the lack o f preservatives in such solutions has any practical advantage relative to the cost/benefit analysis remains to be seen. In summary, delivery o f intraspinal narcotics via a subcutaneous implanted reservoir system has been o f great value in cancer pain management. If difficulties occur, a rational approach to troubleshooting should allow an easy arid timely solution to the problem as well as provide comfort for the patient.
References 1. Zenz M, Schappler-Scheele B, Neuhaus R, Hilfrich J. Long-term peridural morphine analgesia in cancer pain. Lancet 1981;1:91. 2. Poletti CE, Cohen AM, Todd DP, Ojemann RG, Sweet WH, Zervus NT. Cancer pain relieved by long-term epidural morphine with permanent indwelling systems for self administration. J. Neurosurg 1981;55:581-584. 3. Coombs DW, Saunders RL, Schwberger CL, Pageau MG. Epidural narcotic infusion reservoir: implantation technique and efficacy. Anesthesiology 1982; 56:469-473.
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4. Krames ES, GershowJ, Glassberg A, et al. Continuous infusion of spinally administered narcotics for the relief of pain due to malignant disorders. Cancer 1985;56:516-520. 5. Onfrio BM, Yasch TL, Arnold PR. Continuous low-dose intrathecal morphine administration in the treatment of pain of malignant origin. Mayo Clin Proc 1881;56:516-520. 6. Waldman SD, Feldstein GS, Allen ML. Selection of patients for implantable intraspinal narcotic delivery systems. Anesth Analg 1986;in press.
Journal of Pain and Symptom Management