The use of intraspinal drug delivery systems in a comprehensive,
palliative care treatment plan can be an effective means of
controlling intractable pain states.[1-4] The decision to move to an
invasive therapy should be based on a thorough understanding of the
etiology of the pain and related pain generators, the underlying
cancer, and antineoplastic therapy. The topic of complications of
neuraxial infusion devices must include these factors and address
device selection as it relates to the avoidance of potential risks.
For example, the assumption by some anesthesiologists that
intraspinal cannulation is contraindicated in all patients with known
vertebral metastatic lesions is not supported in clinical practice. A
majority of spinal metastatic lesions involve the vertebral body,
which is distant from the dorsal position of the intraspinal catheter.
In one review of 200 patients with spinal metastatic disease, only
seven had disease that obliterated the canal, whereas 26 had some
partial obstruction of the space. A strong suspicion of myelopathy
or cauda equina syndrome should prompt MRI review, radiation oncology
or surgical consultation, and a reappraisal of the likelihood of
success with neuraxial analgesia.
Other assumed contraindications to neuraxial infusion techniques
include history of septicemia, chemotherapy-related leukopenia, risk
of thrombocytopenia, etc. It is clear that patients with
cancer-related pain will undergo chemotherapy and will have
times when their immune systems are compromised by therapy. This
will result in a lowering of platelet counts, leukopenia, and
possible septicemic episodes. Will these episodes result in a direct
risk of complications related to the neuraxial infusions and be a
contraindication to those infusions? Is there a specific level of
thrombocytopenia at which implantation is contraindicated? Is the
presence of active septicemia a true contraindication, whereas a
history of septicemia only a risk factor? All of these issues require clarification.
The one area in which contraindication to implantation appears clear
is with thrombocytopenia. Cancer patients with low platelet counts
and/or anticoagulation therapy are commonly encountered. Our policy
in pain management, developed in close collaboration with medical
oncology, is to proceed if the platelet count is at least 20,000 without
any signs of subcutaneous ecchymosis. Platelet transfusion decisions
are made jointly by the pain specialist and the hematology-oncology
specialist. Reversal of anticoagulation therapy is decided on a
case-by-case basis with consultation from the oncologist.
Based on extensive experience, the only pragmatic contraindications
to neuraxial infusion device implantation are those also relevant to
surgical intervention. Psychosocial contraindications, of course,
should also be considered preoperatively.
A prerequisite to a discussion of complications is a review of side
effects. The side effects of drugs used in implantable devices,
including both externalized devices and implantable pumps and ports,
should be considered before implantation. A careful review of the
patients past drug history is critical. The clinician should
determine if the patient can tolerate the drugs available for
infusion to achieve functional analgesia. Patients who are intolerant
of opioids and are implanted may well suffer from side effects that
preclude the successful use of the implanted device for infusion of
those opioids. Although it is true that much lower doses of opioids
will be required via a neuraxial route, careful screening is
warranted. In addition, the clinician should consider the use of
synergistic drugs for infusion to lower the overall dose requirements
and hopefully to avoid the side effects seen with a single-drug
infusion. Some examples of drug synergy seen during intrathecal or
epidural infusion are opioid-clonidine; opioid, clonidine, and local
anesthetic; or clonidine-local anesthetic. When clonidine is added to
the infusion, the opioid and local anesthetic agent should be
decreased by 30%.
A complete understanding of the potential complications and side
effects associated with implantation, drug infusion, and long-term
device care and maintenance is essential before entering into a
contract for patient care. Cancer-related pain management requires a
constantly evolving care plan responsive to pain and tumor
progression, and a vigilant awareness of potential complications and
side effects. The care plan should ensure that new pain symptoms are
diagnosed and treated, complications are identified and corrected,
side effects of analgesics are identified and treated, or sequential
drug trials are initiated.
Complications related to implantable devices fall into several
categories. Infection is the most feared complication. Although
the risk is real, often the fear alone leads to implantation delays
or to discounting implantation as a clinical option. Complications
discussed in this article include infection, drug-related
complications, device failure, and complications associated with the
use of individual devices.
Infection is arguably the most significant risk in the mind of the
practitioner when the decision is made to proceed with implantation
of an infusion device. The data on the risks of infection after
implantation of either an externalized or buried device are unclear.
There is a lack of prospective epidemiological studies of infection
associated with device implantation. We are, therefore, limited
primarily to a discussion of the causes of device-related infection
based on individual experience without the benefit of those studies.
The sources of contamination include direct contamination during
implantation, hematogenous spread during septicemic episodes, a track
infection in externalized devices, contamination during access of an
implanted device, and contamination of the infusion drug. Sterile
conditions must be maintained during all operative and access procedures.
Externalized devices are considered to have the greatest risk of
contamination. The contamination of these devices is generally
considered to occur along the path of the catheter from a skin
source. Our experience with the long-term epidural catheter indicates
a 5% to 15% infection rate.[7,8] Infections related to implanted
intrathecal access devices are rare and even more rarely
reported.[9-11] These and other reports in the literature are by
individual practitioners, and lack the strength of a prospective
epidemiological study design.
Externalized Catheter Infections
Externalized catheters used to gain access to the intrathecal and
epidural space have been in general use around the world. Most
recently, the use of externalized intrathecal catheters for long-term
infusions has been reported from Sweden.[12-14] In some cases, the
devices have been used for prolonged infusions with low rates of
infection (0.5%). It is interesting to note that the technique
used for infusion included monthly tubing and filter changes. This is
markedly different from the standard in the United States, which
involves changing the pump tubing and filters every 24 to 72 hours.
The reported results suggest that the policies now in effect in most
US hospitals, which are based on infections related to IV infusions,
deserve a new evaluation. Some report the frequency of infection in
externalized catheters is based on the number of days of
implantation, thus trying to reflect the risk of long-term
implantation. If the duration of implantation has a significant role
in the frequency of epidural infections, then all the factors that
are affected by duration of use should be examined. A close
examination of epidural catheter-related infections should include an
examination of the risk factors and the specific site of infection.
Presumed risk factors include general body hygiene, septicemic
episodes, and presence of a colostomy, ileostomy, or other infection
source (eg, an abscess).
Catheter-related or device-related infections are documented as such,
but rarely is the specific site or extent of infection discussed. To
understand the cause of infection, we must first know what tissues
are involved and how the infection progressed to the point of
diagnosis. This can only be determined by obtaining cultures of the
suspected sites of infection. Cultures of the withdrawn catheter will
sample the whole length of the catheter track, without separating the
epidural space from the catheter exit site. The procedure for an
epidural aspirate culture is outlined in Table
1. The following series of cultures will allow the clinician to
diagnose the organism involved in the infections and the source of infection:
Aspiration culture of the epidural space through the catheter
Aspiration (needle) culture of inflamed track infection (avoid
Culture of the catheter exit site
Culture from distant sites of known infections
Culture of other possible areas of contamination
Colostomy or other ostomies
The culture results may indicate a specific result:
A positive culture of the epidural space with a negative culture from
the catheter exit site indicates the epidural space was contaminated
through the infusion and not along the catheter track.
A positive culture of the epidural space with the same organism
identified from the exit site might indicate the source is either the
skin organism contamination of the infusion or a tracking of the
infection along the catheter track. Physical examination should help
in this determination.
A negative culture from the epidural space, but a positive culture
from the catheter exit site and clinical findings of inflammation
along the catheter track, are consistent with an extension of the
catheter track infection, but with presumed preservation of sterility
of the epidural space. Aggressive care is mandatory to prevent extension.
All cultures are compared to determine the relationship between the
suspected area of infection and possible sources.
The standard treatment of epidural catheter-related infections
involves identification of the organism, followed by device removal,
and aggressive antibiotic therapy. After treatment, the patient can
have the device replaced for continued pain management, if desired.
However, this author  and others have successfully treated
indwelling epidural catheter infections with epidurally administered
vancomycin (Vancocin) in the very rare patient for whom catheter
salvage is the paramount concern.
The use of inline catheter filters during long-term use is generally
accepted. The use of a double-filter technique has resulted in a
marked decrease in catheter-related infections. The proximal
filter is never changed unless damaged. The outer or distal filter
and pump tubing are changed on a monthly basis. The author has
experienced only two catheter-related infections in 75 patients (3%)
in the past 2 years with this technique.
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catheterization of the spinal subarachnoid space for continuous
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or implanted catheters and infusion pumps. Clin J Pain 14(1):4-16, 1998.
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