Regional Anaesthesia Arun Kumar Paul
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General Considerationschapter 1

 
BRIEF HISTORY
The term ‘Regional Anaesthesia’ was first used by Harvey Cushing in 1901 to describe pain relief by nerve block. Modern local anaesthesia started with the introduction of Cocaine into medical practice in 1984. It was introduced by Koller as a topical anaesthetic for the cornea. The first synthetic local anaesthetic, procaine was introduced by Einhorn in 1904, Lofgren and Lundqvist synthesised lignocaine in 1943. Lignocaine is the prototype local anaesthetic with which all other local anaesthetics are compared and judged.
A regional anaesthesia may be considered as the anaesthesia of an anatomical part of the body, produced by the application of a chemical (local anaesthetic) agent capable to provide reversible conduction block of neural impulses associated with that part. Subsequent recovery from the effects of block is spontaneous and complete without any evidence of nerve damage.
 
CLASSIFICATION
Regional anaesthesia is usually classified according to the site of application or administration of local anaesthetic to provide regional anaesthesia.
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  1. Topical or surface anaesthesia.
  2. Local or infiltration anaesthesia.
  3. Intravenous regional anaesthesia (Bier's block).
  4. Field block anaesthesia: It involves injecting local anaesthetic into the tissues about the periphery of the operative area.
  5. Conduction anaesthesia: It is often designated as regional anaesthesia or nerve block anaesthesia. It is produced by injection of local anaesthetics along the course of nerve plexus or nerves supplying the region of the body where the loss of sensation and of motor response is needed.
    It may be of three types:
    1. Nerve blocks: It is produced by injection of local anaesthetics near specific nerves to produce anaesthesia in areas innervated by the affected nerves.
    2. Spinal analgesia: It is produced by block of nerve roots in the subarachnoid space.
    3. Epidural analgesia: It is produced by block of nerve roots in the epidural space.
 
Topical/Surface Anaesthesia
Here the local anaesthetic is applied over the skin surface or mucous membrane by spray, as in nose, mouth, or tracheobronchial tree, by spreading a local anaesthetic ointment, by instillation with syringe as into the urethra, by contact as with a saturated cotton pledget in nose or pharynx. Lignocaine (4%) spray may be applied topically on the pharynx and trachea before endotracheal intubation. Amethocaine is widely used to produce topical anaesthesia for bronchoscopy. The local anaesthetics which penetrate mucous membrane poorly (as procaine, chloroprocaine) are not suitable for topical anaesthesia.
EMLA cream (entectic mixture of lignocaine and prilocaine as an oil water emulsion) is applied to skin for at least 60 minutes to get a cutaneous anaesthesia.
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Local/Infiltration Anaesthesia
This method is designed to produce sensory anaesthesia in the particular injected area without any attempt to block the particular nerves. Here the local anaesthetic is injected subcutaneously into the tissues to be cut as for placement of an intravenous catheter, paracentesis of the pleural or peritoneal cavities, lumbar puncture or suturing of tears and wounds.
 
Plexus Blocks
Certain nerves are grouped together to form a plexus. If a plexus is blocked with the local anaesthetic, then several nerves can be blocked at the same time. Brachial plexus block is commonly employed to anaesthetize the upper extremity with a single injection of local anaesthetic.
 
ADVANTAGES
  1. The quality of analgesia and muscle relaxation are mostly satisfactory. Analgesia may continue even in early postoperative period.
  2. Duration of analgesia may be adjusted with proper selection of local anaesthetic, its concentration, its volume and site of injection. Analgesia may be extended for prolonged period using either intermediate bolus injection or a continuous infusion.
  3. Superior quality of analgesia may be provided for prolonged period with less haemodynamic disturbances.
  4. Regional anaesthesia may provide satisfactory analgesia before, during and after surgery. It improves the patient's psychological state by abolishing the pain all the while.
  5. Regional anaesthesia produces motor block causing profound muscular relaxation. It is advantageous for all surgical procedures.
  6. In addition to sensory and motor block, regional anaesthesia provides autonomic block. As a result 4vasodilation may occur. It may help in the diagnosis and treatment of peripheral vascular diseases. Blood supply of skin flaps, amputation stumps, etc. improves and aids healing. It is particularly helpful in trauma surgery.
  7. Adequate regional analgesia obviates the systemic ill effects of pain. It reduces the risk of postoperative complications and improves recovery. The systemic stress response to injury and surgery, the neuroendocrine, metabolic and immunological responses to injury are minimum with regional anaesthesia and this helps to improve the surgical outcome significantly.
  8. As the patients remain awake, the protective airway reflexes are intact all the while.
  9. It can be used in outpatient clinic. It causes less physiologic disruption. Early discharge is possible.
  10. Effective epidural analgesia protects the mother against the stress response to painful labour.
  11. Regional anaesthesia for caesarean section decreases the risk of neonatal depression and maternal complications. Mother remains awake and can share the birth experience.
  12. Regional anaesthesia needs minimal instrumentation and causes minimal physical and mental trauma.
 
DISADVANTAGES
  1. The technique needs full understanding of the topographical landmarks, nerve supply of the area, course of the related nerves, etc. It needs extra knowledge and skill regarding anatomy, physiology and pharmacology. Knowledge of surgical condition of disease is needed.
  2. It is sometimes difficult and time consuming to provide neural blockade.
  3. Drug allergy and toxicity may occur in some cases.
  4. Some patients dislike injections.
  5. Some patients dislike to remain awake during operation.
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  6. There may be failed or inadequate block.
  7. Recovery time is uncontrollable.
  8. In cases with spinal/epidural anaesthesia there may be difficulty in voiding, back pain, postdural puncture headache and so on.
  9. Decrease in blood pressure may occur due to peripheral sympathetic nervous system block by regional anaesthesia particularly in hypovolaemic patients.
  10. Noncooperative patients such as acutely intoxicated and agitated patients are not fit for regional anaesthesia.
  11. Lack of practice may increase the rate of failures of block.
 
INDICATIONS
  1. Anaesthesia
  2. Postoperative analgesia
  3. Diagnosis of chronic pain syndromes
  4. Treatment of chronic pain syndromes.
Besides the common popular indications to provide anaesthesia and postoperative analgesia, diagnosis and treatment of chronic pain syndromes are most important. Differential nerve blocks are often used to distinguish placebo, sympathetic and somatic sensory sources of pain. Pain is said to be psychogenic when relief is obtained by placebo injection in subarachnoid space. When relief is obtained with 0.2% procaine injection, the pain is due to sympathetic nervous symptom pathway. If pain persists after 1% procaine injection, pain seems to be due to more central origin or psychogenic. Stellate ganglion block or lumbar sympathetic block is also being used to detect the sympathetic nervous system origin of pain.
Therapeutic nerve blocks are also being used with local anaesthetics, neurolytic agents or neuroaxial placement of opioids.
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The other indications of regional anaesthesia may also include –
  1. Patient preference: Patient wants to remain awake during surgery. Mother may want to share the birth experience.
  2. Prolonged surgery: Many patients may feel very tiresome and uncomfortable to lie still for more than an hour or two.
  3. In some cases where general anaesthesia is contraindicated and somewhat hazardous due to physical or metabolic derangement, regional anaesthesia may confer benefits of their own. But it should be noted that regional anaesthesia is not always simply alternative to general anaesthesia and it should be judged against merits demerits ratio.
 
CONTRAINDICATIONS TO REGIONAL ANAESTHESIA
The contraindications are mostly relative. As there are so many methods, one can modify the technique and choose the site of injection and local anaesthetic for better patient care.
All patients should be prepared and well-investigated for major operations whether it is scheduled for general or regional anaesthesia. It does not mean that regional anaesthesia needs less investigations and preparation and it is easy and less demanding bypass to general anaesthesia. Pathophysiological disturbances should always be corrected prior general or regional anaesthesia.
However, the relative contraindications may be as follows:
  1. Refusal—Patient wants to loose his consciousness during operation.
  2. Patients with psychological or psychiatric disturbances.
  3. Patients with coagulation disorders.
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  4. Presence of infection at the site of injection.
  5. Trauma/injury/burns over the site of injection.
  6. Patients with metabolic disorders not adequately treated.
  7. Preexisting neurological deficit.
  8. Where sterility of the equipment is not guaranteed.
  9. Where basic resuscitative equipment and drugs are not available.
  10. Where proper valid consent is not present.
  11. Lack of knowledge and practice on the part of anaesthetist.
 
GENERAL PRINCIPLES
  1. Anaesthetist should have a knowledge of the history of the disease concerned and his pathophysiological status.
  2. Anaesthetist should be properly trained and have adequate knowledge and skill to tackle the case even when the complications arise.
  3. The patient should be well-informed about the technique and discuss all merits and demerits.
  4. Patient should give proper valid consent.
  5. Proper psychic preparation of the patient is needed. Patient should be reassured and complete confidence is essential. Adequate and complete explanation is helpful.
  6. Proper preparation for anaesthesia is always needed.
  7. Pharmacologic premedication is always beneficial.
  8. Surgical rules:
    1. Regional anaesthesia technique should be regarded as surgical procedure. Aseptic precautions are essential. Anaesthetist should scrub, be properly gowned and gloved.
    2. All instruments should be sterilised.
    3. Skin preparation on the site of injection should be adequate.
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    4. Proper ventilation, lighting arrangements, asepsis, good operating table, sterilised instrument tray should be fool proof.
    5. Emergency resuscitation equipment, drugs, defibrillator, pacemaker, etc. should be kept ready.
    6. General anaesthesia may be needed in some failed cases, thus anaesthesia machine, drugs and equipment should always be there. Oxygen supply should be available.
    7. Injection site should be aseptically drapped.
    8. Avoid injection to infected site.
  9. Anaesthetist should know the basic pharmacological aspects of the local anaesthetic drugs:
    1. Local anaesthetic vails should be sterile and kept in aseptic instrument tray.
    2. Syringe, needle, lumbar puncture needle, epidural (Tuhoy needle), catheters should be kept in sterile condition.
    3. Dose should be calculated properly and least amount of drug should be used.
    4. Least toxic drug should be used.
    5. Dose and strength and volume should be judged according to individual patient, site of operation, approximate duration of operation, etc. Safe maximum dose of the concerned drug should be kept in mind.
    6. Potentiation problems—Spread of drugs, metabolism of drugs, onset of action and duration of anaesthesia should always be considered during selection of local anaesthetics.
    7. Complications—Systemic toxicity, hypersensitivity reactions, if arise should be promptly diagnosed and tackled accordingly.
  10. Success of regional anaesthesia mostly depends on depositing the local anaesthetic solution accurately on a particular space to block the specified nerves. Techniques 9are mostly blind and depend on anatomical landmarks. Some landmarks either superficial or deep are being used. Superficial landmarks include skin measurements, bony prominences, arterial pulsations, fixed visual points, etc. Deep landmarks are sensations of the advancing needle point into fascial planes, ligaments, deep tendons, bony structures, foramina, etc.
    1. Measurements should always be accurate with the help of a ruler. Special marking pencils may be used.
    2. Deep landmarks should be identified gently and accurately with due sensation of touch of progressing the needle point. Better identification of the tissue and of depth is acquired by practice.
    3. Avoid paraesthesia deliberately. However, if paraesthesia is obtained the needle should be withdrawn a few mm before injection.
    4. Never inject directly to nerve trunk.
    5. Needle should be gently directed towards bone. Note that, the periosteum is extremely sensitive.
    6. Radiologic help is often useful for diagnosis and therapeutic nerve blocks for accurate placement of needles and/or verification of needle position at the time of injection of local anaesthetics.
    7. Use of nerve stimulation may help to locate the nerve.
  11. Techniqueal skill is most important for the outcome of the procedure.
    1. Equipment for regional anaesthesia include proper size syringes and a set of needles. These should be tested beforehand and sterilised properly. Chemical sterilisation is not recommended.
    2. Intradermal wheal is essential to make the injection painfree.
    3. Local anaesthetic solution should be fresh.
    4. Multiple puncture for injection should be avoided.
    5. Site of injection should be accurate.
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    6. Aspiration test is mandatory before actual injection of the drug. After the first aspiration test, the needle should be rotated in 180° and repeat the test.
    7. Injection should be given gently. It should not be sudden and not excessively rapid.
    8. Avoid infected or inflamed site of injection.
    9. Allow the surgeon to start operation after anaesthesia is established. Sufficient time should be given to establish the complete block.
 
CAUSES OF FAILURE OF BLOCKS
  1. Variations of nerve anatomy: Blind technique may miss the site of nerve and block.
  2. Variations of landmark anatomy: Distorted landmarks may lead to failure of block.
  3. Lack of knowledge and skill of the anaesthetist: Adequate knowledge of anatomy, physiology and pharmacology is needed. Dose, strength and volume of local anaesthetic solution should be accurately judged.
  4. Lack of practice: It may lead to error and hence failure of block.
  5. Diagnostic and therapeutic nerve blocks for chronic pain syndromes: Need careful evaluation of pain. Psychic and emotional factors should be borne in mind.
  • Some patients may need general anaesthesia along with regional anaesthesia.
    1. Children may receive regional anaesthesia after induction of general anaesthesia. Risk of neural damage becomes less.
    2. Some blocks like intercostal, interpleural, femoral, sciatic nerve blocks are usually performed after induction of general anaesthesia.
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    3. Patient intends to remain unconscious even when he prefers regional anaesthesia.
    4. Prolonged lengthy surgical procedures.
    5. To obviate tourniquet pain.
    6. If surgery causes reflex stimuli outside the area of regional anaesthesia, general anaesthesia may be helpful.
    7. If the patient becomes noncooperative during the course of surgery, general anaesthesia may have be combined.
    8. Surgical procedures like amputations, cancer surgery, etc. may need combined general and regional anaesthesia for better outcome.