loca and regional anesthesia

Local & regional anesthesia

Local anesthetic agent act by reducing membrane permeability to sodiumAct on small unmyelinated C fiber before large A fibersReduce pain & temperature sensation before touch & powerWhat drugs are used ?Bupivacaine (Marcaine) is a common longer – actiner anesthetic , widely used for epidurals, spinal & other blocksLidocaine also called (Xylocaine , lignocaine) is the most common of the short acting local anesthetics, & is used in many proceduresMepivacaine is similar to lidocaineRopivacaine is a new longer acting agent which appears to be safer than BupivacaineTetracaine is used mainly for spinal Cocaine is still used as a local anesthetic in special cases Other drugs may be added to the local anestheticAdjuncts OpoidEpinephrine Clonidineothers

Lignocaine
Lignocaine is a weak base (PKa=7.8) At physiological PH mainly ionised Has a duration of action of about 1 hour With addition of adrenaline duration of action can be increased to 2 hours Main toxicity is on CNS & CVS Plain lignocaine should be used for local anesthesia in digits & appendages Adrenaline containing solutions can cause tissue ischemia Bupivacaine Effective Medium duration Tachyphylaxis rare High plasma protein bound Selective cardiotoxicity

Regional anesthesia
A general anesthesia is not always necessary or advisable.Depending on the type of operation , the anesthetist can use techniques to completely numb soecific parts of the body .Regional anesthesia is used increasingly frequently to avoid the possible side- effect of GA .It can also be useful in people who are too frail to undergo a general anesthesia .With a regional anesthesia , a small amount of an anesthetic drug is injected near to the nerves that supply a part of the body.The anesthetic temporarily prevents the nerve from sending any messages to the brain – where pain is registered –so the part of the body is completely insensitive to pain. Why choose a local or regional anesthesiaAvoids some of the risks & unpleasantness , such as nausea & vomiting , which sometimes occurs with GA .providing pain relief for several hours after the operation.Reduce blood loss .Some patients feel more (in control) when they are awake during surgery.

How it is used?
Used in addition to a general anesthetic . Provide pain relief after surgery . Nerve block are also used in the diagnosis & treatment of some painful conditions. Prevent pain during surgery . Provide pain relief during labour . Reasons to avoid a local or regional anesthesia Some surgeons are not used to operating on awake patients & may be too rough or impatient for successful regional anestheia . Some anesthetists do not have the skills required to perform the necessary procedures . Some patient cannot cope with idea of being awake during surgery .

Blocks for various parts of the body

Local infiltration for cuts & small procedures. Blocks for eye surgery . Blocks for hand & arm surgery : local infiltration , blocks of individual fingers , iv regional blocks , axillary blocks . Spinal & epidural anesthesia . Caudal anesthesia . Pain relief in labour . Maximum doses of local anesthetic (average adult) plain solution with adrenaline Lignocaine 200 mg (20 ml of 1%) 500 mg (50 ml of 1%) Bupivicaine 150 mg (30 ml of 0.5%) 200 mg (40 ml of 0.5%) Prilocaine 400 mg (80 ml of 1.5%) 600 mg (120 ml of 1.5%)

Spinal & epidural anesthesia

Spinal anesthesia – local anesthetic or opiad injected into CSF below termination of cord at L1(adult) .Used for operations below the waist or in the pelvic region .The patient completely numb from the waist down for a couple of hours .Epidural anesthesia - local anesthetic or opiad injected into fatty epidural space .An epidural uses a similar technique to spinal anesthesia, with a (catheter) narrow plastic cannula left in position near to the nerves in the backThis means that the anesthetist can give repeated doses of local anesthetics & (painkillers) without further injection .This makes it useful for longer operations .An epidural can be used for postoperative pain relief & for labour pain .Both can produce good anesthesia for up to 2hoursThe quality of block is often better with a spinal .Epidural anesthesia is technically more demanding .

Contraindications to central blockade

AbsoluteSepsis BacteremiaSkin infection at injection siteSever hypovolaemiaCoagulopathyTherapeutic anticoagulationIncrease intracranial pressureLack of consentRelative Peripheral neuropathy Mini – dose heparinPsychosis Or dementiaAspirin or other antiplatelet drugs Demyelating central nervous system diseaseCertain cardiac lesion - idiopathic hypertrophic subaortic stenosis - aortic stenosisPsychologic or emotional instabilityUncooperative patientProlong suergerySurgery of uncertain durationSurgical team resistance to awake patient


Complications
spinal Epidural Hypotension Common Less common LA toxicity Rare Occasional High blockade Occasional Occasional Urinary retention Common Less common Headache 1-5% never unless dural puncture Local infection Almost never Uncommon Meningism Uncommon very rare Epidural haematoma Almost never very rare Backache common common Common uses for spinal : Caesarean section Hernia repair Hip & knee surgery Most procedure on the foot or leg

IV Regional anesthesia 
Also known as a Bier block Used on surgery of the upper & lower extremities Patient must an IV cannula inserted in the operative extrmity After a pneumatic tourniquet is applied to extremity , Lidocaine is injected through IV Anesthesia lasts until the tourniquet is deflated at the end of the case IMPORTANT- to prevent an overdose of lidocaine it is impotant not to deflate the tourniquet quickly at the end of the procedure The anesthetist will deflate/ inflate tourniquet several times before complete deflation of tourniquet cuff Injection of local anesthetic around a peripheral nerve Can be used for anesthesia during surgery or for post-op pain relief Examples : ankle block for foot surgery , supraclavicular block for post-op pain control after shoulder surgery For operations on a small area of the body It is possible to simply inject local anesthetic at the site of the operation This technique is often performed by the surgeon or GP in minor surgery unit