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INTERVENTIONAL PAIN MANAGEMENT (IVPM)
DK BAHETI
Chief, Pain Management Clinic, Associate Professor, Anaesthesiology, Bombay Hospital Institute of Medical Sciences, 12, New Marine Lines, Mumbai 400 020 India.
INTRODUCTION
Relief of pain, has come long way, since WTG Morton’s, first ever, public demonstration of anaesthesia. Since then the anaesthesia as a specialty has made significant strides and the horizon of anaesthesia is widening every day.
Of late in last ten years or more the importance of pain management is on the tremendous rise and is recognized as super specialty of Anaesthesiology. Pain management provides the anaesthesiologist a much-deserved recognition, identity in the medical fraternity and in the society.
IVPM (i.e. neural blockade, ablasive procedure, electric stimulation, epiduroscopy etc.), although invasive, remains an important modality in management of acute and chronic pain. There have been many advances in understanding, usefulness and intervention at right time in selective patients produces excellent results.
ADVANTAGES OF IVPM
- It produces immediate pain relief.
- It can be performed with ease and with minimum equipment.
- Adequate duration of pain relief obtained.
- Minimum or no hospitalization is required.
- Procedure can be repeated.
- Suitable in aged and debilitated patients.
ACUTE PAIN
Postoperative Pain
These procedures can be performed adults and in children as well, however dosage required to be decided by the pain physician concerned.
-Infiltration block - infiltration of local anaesthetic agent such as Inj. Sensorcaine 0.25% or Inj. Lignocaine 1% in and around the surgical incision provides pain relief for 1-3 hours.
-Regional analgesia - Intrathecal, Epidural (caudal, lumbar, thoracic), intrapleural, intercostals, brachial plexus are well-accepted techniques used for relief of post-operative pain. The analgesic agents used are local anaesthetic agents such as sensorcaine, lignocaine and morphine, buprenorphine, fentanyl tramadol, midazolam, ketamine, neostigmine.
-Patient controlled analgesia (PCA) - The routes are intravenous, epidural with the help of infusion pump, syringe pump or pre-set drug delivery balloon pump. The drugs are morphine, fentanyl, sensorcaine, lignocaine, tramadol, and buprenorphine.
Chronic Pain
The modalities can be classified as follows.
-Neural blockade (nerve block)
-Electric stimulation
-Spinal endoscopy/epiduroscopy
-Ablative procedures
-MiscellaneousNeural blockade (nerve block)
The perineural injections of local anaesthetic have been in practice since 19th century since the introduction of cocaine by Karl Kollar in 1884. Dogliotti popularized the application of neurolytic agents for relief of pain. Pain sensation is conveyed primarily by the "A delta" and the "C" fibres. The "a delta" carries fast sharp shooting pain sensation, whereas the "C" fibres carries dull, aching, burning pains often associated with tumours.
PRIMARY LOCAL ANAESTHETIC BLOCK-WHY?
It is done for the following reasons.
1. The block confirms that it produces adequate pain relief or not.
2. The patient is aware of the side effects and complications in any, for shorter duration.
3. It prepares the patient psychologically for side effects and complications of neurolytic agent.
Recent enhancements on neurolytic blocks include the application of sophisticated techniques of radiological guidance either with C-arm fluoroscopy or CT assisted localization of particular plexus or nerve. These measures have provided much-needed boost in the relief of pain.
Neurolytic drugs : these are alcohol, phenol, glycerol and chlorocresol. The alcohol is hypo baric with respect to cerebro spinal fluid and it is used either in 100% or 50% concentration. The neurolytic action of alcohol is through a dehydration action on the nerve tissue, with the extraction of cholesterol, phospholipids and cerebrosides and the precipitation of mucoproteins. This results in sclerosis of the nerve fibers and myeline sheath destruction. The phenol is hyperbaric and prepared in water, saline or glycerin and concentration used is 5% to 10%. It acts by protein desaturation. TYPES OF NEURAL BLOCKADE
1. Peripheral Blockade - It has definite, although limited role in management of malignant pain. The paravertebral and subarachnoid blocks are commonly done especially upper intercostal nerve blocks are technically difficult to perform. However, regeneration of peripheral nerves is sometimes associated with neuritis or neuroma formation.
2. Cranial Nerve Block - Head and neck malignancy is most challenging one. In selected patients blockade of trigeminal and glossopharyngeal nerves provide excellent pain relief. As major surgical intervention may involve high risk of mortality and morbidity.
3. Sympathetic Block - It can be of diagnostic, prognostic and therapeutic purpose. Coeliac plexus block (NCPB) provides excellent pain relief in upper abdominal malignancy patients. In 50% alcohol 40-50 ml around coeliac plexus produces excellent pain relief. Stellate or cervico-thoracic ganglion is very useful in chronic regional pain syndrome (CRPS), peripheral vascular disease or ischaemic limb pain of upper extremities. Inj. Alcohol 100% 8-10 ml or Inj. Phenol 6% 10 ml around stellate ganglion produces good pain relief. Lumbar sympathetic chain L 1 to 5 with Inj. Phenol 10% 10-15 ml or Inj. Alcohol 100% 10-15 ml produces excellent pain relief in peripheral vascular diseases such as Burger’s disease.
4. Subarachnoid and Epidural Neurolytic blocks - These are useful in malignancy of lower extremities, pelvic, vagina and rectal origin. Alcohol being hypobaric the part to be blocked should be upwards. Whereas with phenol being hyper baric the affected part should be kept down, so the phenol will gravitate along the nerve roots. The each affected dermatome the dose of Inj. alcohol 1 ml and Inj. Phenol 1 ml is sufficient.The slow penalization of epidural space is very useful technique in lower abdominal malignancies. In this every day Inj. Phenol 5% 2-3 ml every day for 3-4 days is injected through epidural catheter in supine position.Saddle block - Inj. Phenol 5% 3-6 ml is injected through lumbar puncture and modified sitting position by 45 degree posterior for 15-30 minutes. This produces good pain relief in perineal and pelvic malignancies.
5. Superior Hypogastric Block - Intractable pelvic pain syndrome from rectum, vagina, cervix poses challenge to pain physician. The neurolytic superior hypo gastric plexus with Inj. Phenol 5% 10-15 ml or Inj. Absolute Alcohol 8-10 ml produces excellent pain relief.
IMPLANTABLE DEVICE
It is used for continuous intrathecal drug infusion, which blocks pain by administering small doses of morphine directly in to the spinal cord. Intrathecal drug infusion requires much smaller doses of morphine for pain relief than oral or intravenous methods. Patients will have fewer side effects and greater pain relief. It is used in patients with severe and chronic pain in broad areas of the body, either from cancer or other cause, may benefit from intrathecal drug infusion therapy.
This system consists of an electronic pump and catheter. The pump is a round metal disk about one inch thick and three inches in diameter. It weighs about six ounces. It is surgically placed just underneath the skin usually in the lower abdominal area. The spinal catheter is tunneled under the skin into the spinal canal. The pump stores and releases prescribed amounts of morphine into the spinal canal. The pump can be refilled by inserting a needle through the patient’s skin into a filling port in the centre of the pump. The catheter is a flexible tube that delivers the morphine from the pump to spinal canal.
ELECTRICAL STIMULATION
The gate control theory by Melzack and Wall, has initiated the peripheral nerve stimulation via an implanted electrode. It was the first clinical application of the basic concept of producing analgesia by activation of large, low-threshold fibre afferent systems. This principle is used for electrical stimulation of spinal cord and brain.
SPINAL CORD STIMULATION (SCS)
Many theories have been proposed to explain the pain relieving mechanisms of this technique such as gate control theory, activation of supraspinal mechanisms, neurochemical alteration in the central nervous system, blockade of spinothalamic tract and inhibition of sympathetic nervous system tone resulting in vasodilatation.
SCS stimulates the spinal cord with tiny electrical signals to interfere with the transmission of pain signals to the brain, thus reducing the sensation of pain. The affected area feels gentle tingling. SCS is reversible procedure that does not damage the spinal cord or nerves.
There are two types of SCS:
1. Fully implanted system consists of a totally implantable system with an electrode with multiple contacts, an extension and a pulse generator, which are placed under the skin. The pulse generator contains a battery pack, an antenna and computer module. It provides the power and it is inserted in the abdominal wall. It has a circuit that allows it to be programmed for individual patient. Several parameters can be programmed transdermally via a portable computer. These include pulse width, rate voltage, anode-cathode combinations, stimulation mode (continuous vs. cycling), high/low limits and magnet mode.
2. Partially implanted system consists of an electrode with multiple contacts connected to a radio frequency receiver. Both are implanted under the skin. An external radio frequency transmitter is then placed over the receiver. Which enables the system. The transmitter is programmed directly without the need for a portable computer. The transmitter is powered by a 9-V battery, which has to be changed periodically depending on the amount of voltage the patient requires for adequate coverage of his or her pain.
SCS is an effective modality in relief of pain in peripheral vascular diseases; post laminectomy pain and neuropathetic pain especially in diabetic neuropathy. BRAIN STIMULATION
One can selectively stimulate different parts of brain such as intracerebral and motor cortex area. The facility of stereotaxic procedure along with the trained, experienced medical team is mandatory to perform this specialized technique. Intracerebral stimulation can be sensory thalamic stimulation and periaqueductal periventricular stimulation. Some forms of neuropathic pain of supraspinal aetiology can be treated by sensory thalamic stimulation. Motor cortex stimulation - pain of central origin and supraspinal (post-stroke) pain may be treated with motor cortex stimulation.
EPIDUROSCOPY
The epiduroscopy helps in visualization and exact location of pathology in post laminectomy pain or failed back syndrome patients. The procedure is done in operating room and under fluoroscopic control. The presence of anaesthesiologist is necessary to provide light sedation and monitoring of vital signs during the procedure.
A 17 gauge Toughy needle is passed in to caudal epidural route and position of needle is confirmed under fluoroscopy. An epidurogram is done with Inj. Omnipaque 5 to 15 ml, to know the degree and severity of epidural adhesions.
A guide wire is introduced through Tuoghy needle towards lumbar area not beyond fourth lumbar vertebra in order to avoid dural puncture. The punctur site is dilated with dilator sheath and introducer is passed over the guide wire. Now remove the guide wire. Then a steerable catheter along with a 0.9 mm fibrescope is passed through introducer sheath. A diagnostic epiduroscopy visualizes caudal epidural space and its contents. The steerable catheter is rotated side by side to perform adhesiolysis. The epidural space is irrigated intermittently with normal saline and the quantity of normal saline should not exceed 100 ml. epidurogram will confirm the extent and success of adhesiolysis. The degree of pain relief confirmed by patient also acts as a guide of adequate adhesiolysis.
At the end of the epiduroscopy Inj. Depomedrol 80 mg, along with 0.5% Lignocaine 20-40 ml plus normal saline 25 ml is injected. A total of 40-50 ml is usually adequate to cause volumetric adhesiolysis.
The epiduroscopy has dual effect : one to have adhesiolysis by steerable catheter and second to inject large volume of Inj. Depomedrol 80 mg + Inj. Lignocaine 0.5% + Inj. Normal Saline 20 to 30 ml in order to produce volumetric adhesiolysis so have maximum pain relief. Epiduroscopy is effective in the treatment of failed back syndrome or post laminectomy pain and radicular pain.
ABLATIVE PROCEDURES
Ablative neurosurgical procedures have about 100 year history in the management of pain. The following ablative procedures are performed.
Peripheral Neurectomy - Neurectomy will produce complete anaesthesia in the distribution of the nerve, although there may be considerable overlap from adjacent nerves. It can be used for body wall pain secondary to neoplastic invasion.
Sympathetic Nervous System - Surgical sympathectomy can be performed for pain originating in the limbs, the heart, the abdominal viscera and pain due to vascular spasm as seen in Raynaud’s disease or in CRPS such as cervico-thoracic, lumbar sympathectomy and presacral neurectomy.
RADIO FREQUENCY COAGULATION (RFC)
The neurolysis is produced by coagulation with the help of controlled heat generated by Radio tome. RFC is being used in treatment for trigeminal neuralgia, coeliac plexus block, Para vertebral nerve blocks and cervical plexus block.
- Dorsal Rhizotomy - It is superior to peripheral neurectomy because only sensory root is transected, leaving motor function intact. It can be performed either intradurally or extradurally.
- Spinal cord procedures - The open or percutaneous cordotomy is effective procedures in some of the cases of cancer pain. The well-known procedure is DREZ, is described by Nashold and Osdahl. They described the creation of a series of radio frequency lesions in the dorsal root entry zone performed under direct vision after laminectomy under general anaesthesia. It produces segmental band or sensory loss corresponding to the level of the lesion.
MISCELLANEOUS
Laser Discectomy - The application of laser to perform discectomy is a definitely a new procedure. Although laser has another uses such as to treat trigger points.
Laser probe is passed through spinal needle in to the disc, and disc is dissolved with the help of laser under fluroroscopic control. This procedure is done under local anaesthesia and as one-day surgery procedure.
REFERENCES
1.Textbook of Pain - by Melzack and Wall - Third edition 2000.
2.Pain 1999 - An updated review - IASP Press. 1999.
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