Pain Management

Introduction

There are no published satisfactory and comprehensive community surveys of the prevalence and impact of chronic pain syndromes in children and adolescents. Assisting and guiding a child with a chronic pain disorder and the parents is an exceptional challenge.

The components of a comprehensive diagnosis of a chronic pain syndrome are:

• The underlying pathology, its cause, nature and extent and whether there is associated pain, tenderness consistent with primary allodynia/hyperalgesia.

• The presence of a peripheral neuropathic disorder contributing to or causing pain.

• The clinical signs of cutaneous or/and deep tissue allodynia at sites where there is no apparent pathology that is secondary allodynia with potential implications about central sensitization of nociception.

• Interference with function

• Associated psychological factors

Representative Pediatric Disorders Characterized by Chronic Pain

Cancer Pain

In recent years, it has become evident that the appropriate assessment of a patient with cancer pain requires a multi-dimensional evaluation of the pain syndrome - the patient's clinical and psychological characteristics, and a number of specific prognostic factors that have a major impact on the treatment outcome and might help focus the care. It has also become apparent that pain should be considered in the context of other major symptom complexes that are also highly prevalent in patients with advanced cancers.

Analgesic Ladder Approach

An analgesic ladder approach to the selection of analgesic drugs for cancer pain has been developed by CANCER PAIN RELIEF AND PALLIATIVE CARE PROBLEM OF WHO (1996). Patients with mild to moderate pain are usually first treated with acetaminophen or NSAIDs. This drug is combined with one or more adjuvants if a specific indication for one exists. These adjuvants drugs include drugs selected to treat a side effect of the analgesic (e.g. laxatives) and drugs with analgesic effects.

The role of morphine in the management of chronic pain has also evolved with the recognition of its active metabolites.

Based on clinical experience, there are a few guidelines for the selection of an opioid as an alternative to morphine. Patients with severe pain, who require rapid dose titration, are generally best treated with drugs that approach steady-state after treatment is initiated or the dose is changed. Controlled - release drugs, including the long-lasting morphine and oxycodone preparations and the transdermal fentanyl system, can require up to several days to approach steady-state concentrations and are usually not preferred in this setting.

Non-opioids

NSAIDs, Acetaminophen: useful for bone pain, soft tissue pain, dysmenorrhea. May be added at step one and continued on all 3 steps of the ladder.

Opioids

Effective for most pain types, may require higher doses for neuropathic pain. Add weaker opioid or lower doses of stronger opioids (morphine) at step two of the ladder, increase the dose if pain persists or progresses to severe intensity.

Opioid Analgesics (Table 1)

Opioid analgesics used for Rx of chronic pain

Route of administration

The oral route for opioid delivery is effective, economical, and acceptable to most patients. It is preferred for chronic opioid therapy. During the course of a medical illness, however, a substantial proportion of patients require an alternative route, at least for a period of time. A large number of the alternative routes are available and in the absence of a comparative trial, the selection of one or another is based on clinical judgment and experience.

Routes of administration: (Table 2)

Adjuvant Analgesics

Tricyclics antidepressants, anticonvulsants, corticosteroids, local anesthetics. Effective for neuropathic pain, may be added at step 1 and continued on all 3 rings of the ladder.

Adjuvant analgesics: The WHO "analgesic Ladder" approach recommends co-administration of adjuvant drugs to treat opioid side-effects or symptoms associated with pain or enhance analgesia (WHO 1996). This category includes numerous drugs that have primary indications other than pain but are analgesics in specific circumstances.

Adjuvant Analgesics: (Table 3)

Newer Techniques Of Drug Delivery

Encapsulation Matrices:

Liposomes:

Iophendylate:

Transfersomes:

Microspheres:

Spinal implants:

• Percutaneously inserted epidural catheters

• Subcutaneously tunnelled epidural/intrathecal catheter

• Implanted epidural or intrathecal catheter connected to access ports

• Implanted intrathecal manual pumps

• Implanted intrathecal or epidural infusion pumps

• External pumps

During patient selection, the general and mental status, life expectancy, nature, and the origin of the pain, the skin over the implantation area, patients' environment, and support systems should be considered.

Contra-indications: Include patient refusal, cachexia, sepsis and concomitant anticoagulant therapy.

Trial of spinally administered opioid

Before implanting a drug, it is essential and a decision to implant should be made only after a positive trial response. Spinal opioid sensitivity should be tested to define the patient's probable acute response to spinal infusions and to suggest the outcome likely to be anticipated from long term administration. The daily epidural/intrathecal opioid consumption, the level of activity and sleep, subjective pain scores, the need for additional analgesics, and side effects should be recorded. During the trial time, systemically administered opioid medications are needed for breakthrough pain. During the trial, the response to spinal opioids, the need for the addition of local anesthetics or other drugs, the administered route, and the success of the method can be assessed.

"Which Delivery System?"

In general, the delivery system is selected according to life expectancy.

Temporary epidural catheter

Percutaneous or subcutaneously tunneled epidural and intrathecal catheters are selected for patients with a short life expectancy, inactive patients for whom occasional dislodgement and replacement are preferable to implantation, or patients with severe pain for whom the short-term catheter immediately provides quick access and rapid relief, with further device planning at a future date.

Permanently implanted catheters

If improved, pain control, and decreased side-effects warrant more prolonged therapy, temporary catheters are, usually replaced by permanently implanted catheters within days to weeks. These systems have advantages in terms of sterility, comfort, and freedom of movement for the patient. This requires either a port for percutaneous access or an implanted, pump-driven, percutaneously refillable reservoir system. The port system has a resealable membrane capable of withstanding percutaneous injections, and a filter to prevent the particulate matter being injected spinally. There are various injection ports available port-a-cath, Spinalgesic, Spinoplast, Periplant, celsite, and Pharmacia epidural port. Disadvantages of such systems include numerous skin punctures, blockage of the port outlet or catheter, greater expense, the risk of infection, and surgical intervention being needed for system placement or removal.

Implantable infusion device:

Indicated in patients with long life expectancy. They are initially expensive but have the advantage of low costs over time. The device is implanted within the subcutaneous tissues of the anterior abdominal wall or subpectoral, the catheter being sited in the intrathecal or epidural space. The only significant drawback of such a system is usually the low reservoir volume.

Implanted pumps consist of a reservoir system and a pump mechanism. The pump mechanism can be driven either internally (by a lithium battery), externally (by an induction device), or mechanically (being patient operated). Pumps offering continuous plus-on-demand infusion rates are preferable to those with fixed infusion rates because of greater flexibility as Tolerance develops.

Complications:

• Bleeding can occur at the surgical site - all anti-coagulants and NSAID's therapy should cease 3-7 days prior to implantation.

• Pump pocket seromas are self-limiting.

• CSF leakage may occur from accidental dural rupture during the epidural approach because of the discrepancy between size of the intrathecal catheter and that of needle.

• Post dural puncture headache - with persistent CSF leakage.

• A CSF Hygroma is mostly self-limiting with in 1-2 weeks.

• Infection can occur at catheter site, pump pocket, epidural space or intrathecal space.

• Needle placement and intrathecal catheter advancement can damage nerve roots, conus medullaris or the spinal cord itself, leading to radiculitis, myelitis, paralysis, paresis, loss of bowel and bladder control and/or myelopathic pain.

Patient Controlled Analgesia (PCA)

PCA is a relatively new route of drug administration, offering great promise in both pain control and research. Results from the management of chronic pain show that PCA can lead to significant improvements in ambulatory patients with cancer. The fundamental principle of PCA is that it allows patients to reach their own analgesic state and thereby achieve an individual balance between pain relief and the appearance of side-effects.

The point at which the patient becomes uncomfortable enough to make a demand has become known as the minimum effective (blood drug) concentration (MEC). The MEC represents that concentration which removes the distress of pain but not necessarily the sensation of pain. When using PCA, patients should load themselves to exceed their MEC and then demand to deliver the drug as needed to maintain it. This demand pattern ensures that the patient maintains satisfactory pain relief without excessive sedation. Preoperative education concerning PCA may greatly influence its post-operative use.

Transcranial Electrostimulation

A new transcranial electrostimulation device, the PULSATILLA, has now been developed for use in acute and chronic pain. Quasi-resonance produced by the pulses in the antinociceptive region of the brain induce accelerated ß-endorphin secretion. It consists of a microcontroller-based stimulus generator with a resident medical software library, and a headset with electrodes. One electrode is placed on the forehead and another on the mastoid bone behind each ear. The battery-operated generator emits pulses of a fixed and controlled frequency and shapes at a maximum of 4 mA strengths. Treatment sessions last up to 30 mins.

Contra-indications: Epilepsy, glaucoma, CNS disease, demand cardiac pacemaker, and skin damage over electrode areas.

Radiofrequency Nerve Blockade In Pain Therapy

Stereotactic radiofrequency (RF) procedures are a part of the range of nerve blocks available for relief of pain.

Principles

Advantages

• Nerve destruction is localized, controlled in extent and reversible. Control of heat is also useful to limit destruction and minimize the risk of denervation dysaesthesia.

• The technique is minimally invasive.

• Accuracy of needle placement is facilitated by X ray monitoring.

• Most procedures can be accomplished under light sedation and local anesthesia.

• There is low incidence of complications.

Disadvantages

• The RF equipment is expensive.

• Training and experience are required.

Transcutaneous Electrical Nerve Stimulator (TENS)

TENS is worth considering in patients with central pain who do not have severely reduced sensitivity for vibration and touch that is who has signs of fairly well-preserved function in the dorsal column pathways. Thus, the proportion of responding patients is small and perhaps even smaller in the other central pain syndromes.

Alternative Therapies For Pain Management

Principles that guide the use of complementary techniques in the management of chronic pain in children include:

• Recognition that the education of children and their parents about the multi-dimensional nature of pain and its treatment is crucial to the success of complementary approaches. Without the understanding of the role that complementary treatments can play and the mechanism by which they may exert their effects, children and parents may refuse them, due to concern that health care providers do not see their pain as "real".

• A rehabilitative approach that emphasizes improving the child's and families' ability to cope with the chronic condition and decreasing pain related to emotional and behavioral conditions.

• The recognition that interventions need to be tailored to the child's individual characteristics not just to his/her specific conditions.

• An orientation toward prevention where possible by anticipating and aggressively managing acute pain, pain exacerbation, and other stressors as they occur within the context of a chronic pain condition.

Complementary techniques:

Acupuncture: Ancient Chinese medical technique involving stimulation of specific skin location by a variety of methods. Example: Needle insertion at an acupuncture point.

Art therapy: Use of creative arts to modify pain and mood. Example: having children use arts and craft as a means to express feelings/concerns about their pain and its treatment.

Behavioral management: Use of operant and classical conditioning methods to manage pain-related disability. Examples: Rewarding a child's efforts to increase activities and comply with treatments; desensitizing a child to aversive aspects of medical treatment.

Breathing: Modulation of breathing to increase the sensation of relaxation and exercises to distract the child from pain. Example: Deep breaths, "blowing away pain".

Biofeedback: Provision of auditory and/or visual feedback related changes in involuntary bodily responses to assist with the modification of these responses. Examples: Heart rate, galvanic skin response (GSR), hand temperature, and electromyography (EMG).

Cold therapy: Use of cold to provide local analgesia, typically for acute pain. Examples: Ice massage, vapor coolant sprays, cold packs.

Cognitive therapy: Modification of cognitions that exacerbate pain and mood. Examples: Reducing negative, "catastrophizing cognitions", increasing the child's positive self- statements about his/her abilities to cope.

Distractions: Use of any variety of methods that absorb the child's attention methods to reduce the child's focus on pain and pain treatment. Examples: bubble blowing, singing, videogames, party blowers, pinwheels.

Education: Providing age-appropriate information to children about their pain, and the methods used to treat pain. Example: Explaining to a school-age child that they can rub the injection site "close to the pain gate" before and after the shot.

Exercise: Prescribed activities to increase the child's functional capacities and reverse any pain related deconditioning. Examples: stretching, strengthening, flexibility, aerobic, and range of motion exercises.

Heat Therapy: Use of heat to relieve muscle spasm, joint stiffness, and increase local metabolism. Example: Hot packs, hydrotherapy, ultrasound.

Hypnosis: Induction of an altered state of consciousness, wherein the child is suggestible to alterations of sensation and perception. Examples: the child with CPRS may imagine herself turning off a pain switch to reduce sensation in an affected limb.

Massage and touch: Application of touch or force to soft tissues, usually without causing movement or change in joint position. Examples: Rubbing the site of a needle injection, stroking/kneading sore muscles.

Mental Imagery: A multi-sensory representation of experience. Examples: Having children imagine themselves in a pleasant place doing something they really like to do, involving as many senses as possible in the image.

Music therapy: Use of music to modify mood and distract the child from pain. Examples: having the child sing a song or listen to favorite music.

Play therapy: Use of play to desensitize or educate a child about their plan and painful medical procedures. Examples: Play with medical props supervised by a play therapist or child specialist.

Relaxation: Techniques that reduce the stress response and produce feelings of mental calmness, usually involving a repetitive stimulus. Examples: Progressive muscle relaxation, meditation, autogenics.

TENS: Use of electrical stimulation that can be applied to the skin at different rates and intensities, to relieve pain. Examples: Positioning of TENS unit over the muscle in spasm.