Pain is the most common and perhaps the most dreaded symptom in terminal cancer patients. Chronic pain from cancer puts immense emotional, economical and psychological strain on both the patients and the next of kin.
Chronic pain leads to poor appetite, low morale and depression which adversely affect not just survival, but also the quality of life in cancer patients. Cancer pain not just affects the patient but also creates a sense of helplessness and despair in the family members. This article is meant for basic understanding of cancer pain and looks into the pump based drug delivery systems for managing cancer related pains.
What causes pain in cancer?
To understand how pain in these patients can be relieved, we first need to understand the basis or origin of pain in cancer. Cancer in itself is painless to start with. However, as it grow bigger, it tends to infiltrate the nearby pain sensitive structures like peritoneum in abdomen, pleural covering of lungs, periosteum of bones, nerves etc. As cancer spreads to areas other than the site of origin, pain generators become multiple. As more and more sites become involved, the severity of pain and requirements of analgesics increases.
Besides the primary disease, chemotherapy and radiotherapy for cancer can also lead to chronic pain by damaging pain sensitive structures like nerves.
How is pain in cancer patients managed?
Cancer pain is managed with multiple strategies. The pain is managed using a step ladder kind of approach, called WHO analgesic ladder, in which pain is initially managed with non-opioid analgesics like Non-steroidal anti-inflammatory drugs or NSAIDS.
Once pain becomes more severe and is not controlled with non-opioid analgesics, then mild opioid analgesics are added. But over time, most patients require strong opioid analgesics, of which Morphine is considered the gold standard for moderate to severe cancer pain, because of it’s pain relieving quality. Other potent opioids that are used in pain relief are Oxycodone, Hydromorphone and Fentanyl.
Certain drugs which are not analgesics primarily like anti-depressants, anti-epileptics, or corticosteroids may be added to these analgesics depending upon clinical judgement.
As pain is a subjective phenomenon, response to different drugs may vary from patient to patient. Therefore, adequate pain relief may require a permutations and combination approach.
What are the problems with Opioid drugs?
Opioid drugs are very good analgesics, but they also have a lot of problems. One is ‘Tolerance’ to these drugs, which means that these medications become less effective. This requires an increase in dosage or addition of a second drug. Certain side effects like sedation, dizziness, nausea, constipation and respiratory depression can be quite disabling to the patients. These side effects increase with increasing doses. Certain side effects like addiction and physical dependence are not significant in cancer patients.
What is an Intrathecal pump?
Drugs can now be directly administered into the cerebrospinal fluid(CSF, fluid surrounding spinal cord and brain). CSF is present inside the subarachnoid space or intra-thecal space. Morphine is the most common drug used through this route. This route not only provides good pain relief but also reduces the dosage of drugs, and hence the side effects. Besides Morphine many other drugs are now available for such pumps.
The assembly includes a catheter which is put into the intra-thecal space containing CSF, a connecting tube and pump with drug reservoir placed under the skin in the abdomen. The pump delivers a fixed amount of drug over time which can be adjusted externally in programmable pumps or by changing the drug concentration in mechanical pumps.
The intra-thecal catheter is put using a small incision in the lower back and the pump is put in the abdomen beneath the fatty layer through a 6-7 cm incision.
What are the advantages of Intrathecal pump?
Good pain relief
Lower dosages with less side effects
Decreased oral medication requirement
Improved functional abilities
What are complications associated with an Intrathecal pump?
Complications related to procedure: Infection is one of the most dreaded complications. Minor infections can be treated with antibiotics, and dressings. Major infections require removal of all hardware. Operative site bleeding, and injury to nerves in intra-thecal space during catheter insertion are other possible complications.
Complications related to the pump and catheters: After an initial successful implant insertion, catheters can become dislodged, kinked or get broken. Catheters may get blocked with cellular debris. Pump may fail because of battery failure or drug reservoir may dry out.
Complications related to drugs: Increased drug delivery can cause excessive sedation, and sometimes life threatening respiratory depression. To prevent these, the dosage is started at a minimum and titrated upwards to achieve good clinical results with acceptable side effects.
Who are good candidates for Intrathecal pump insertion?
Patients who responded well to oral Opioids, but developed increasing pain or side effects
Cancer patients who are likely to survive more than six months
No spinal metastasis which can prevent catheter insertion
Good response with Intrathecal dose trial
How is a trial before pump installation done?
A trial can be conducted over a period of two to three days by giving medicine into the intrathecal space through a one catheter. The catheter can be passed under local anaesthesia, and drug is given. Dosage is dependent upon the total oral dose requirements. The trial is considered positive if the patients has significant pain relief and improved pain scores over the trial period.
Intra-thecal pump assembly
How is the surgery for pump installation done?
The surgery is performed under general anaesthesia. The patient is positioned in lateral position. Skin is cleaned and surgical drapes are put in a sterile manner. A 3 cms skin incision is made over the lower back at level of fourth lumbar vertebra. A special needle(Touhy needle) is then passed into the intrathecal space and a catheter is passed into the intrathecal space. The catheter is passed for around 15 cms towards the head end of the patient under X-ray guidance.
Through a separate incision over the abdominal wall, a pocket is made in the subcutaneous tissue to place the reservoir cum pump for the drug.These two sites are connected through a tube passing beneath the skin. All the three units are connected and incisions are closed. The surgery normally takes 45 minutes.
Disclaimer- This article is for the general awareness of the patients and cannot replace expert medical advice. Patient treatments need to be individualised and that can be decided based on clinical examination and evaluation by a trained physician.
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