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What is Regional Anesthesia

Regional anesthesia is used when only one area of the body, like an arm or a leg, needs to be

anesthetized in order to perform an operation. There are several types of regional anesthesia namely

1. Spinal anesthesia involves injecting a local anesthetic into the fluid surrounding spinal nerves.Once injected, the medicine mixes with spinal fluid in the lower back and numbs the nerves it

contacts, effectively blocking sensation and pain.

2. Epidural anesthesia involves the placement of a catheter into a small space within the vertebralcolumn just before the spinal fluid. Depending on the nerves targeted, the epidural can be

placed in various regions of the back from the neck to the tailbone. Epidural medications can be

given through this catheter to provide numbness for the surgery, and also can be used to

provide pain relief in the post-operative period.

3. Intravenous regional anesthesia is the process of placing an IV catheter into a vein in your lowerleg or arm so that the local anesthetic can be administered. An important part of intravenous

regional anesthesia is placing a tourniquet above the area to ensure the medicine stays in the

arm or leg that is being anesthetized. Feeling will return to the area once the tourniquet is

removed.

4. Nerve Blocks Anesthesiologist can use a variety of nerve blocks to ensure comfort throughouta surgical procedure. Often a group of nerves, called a plexus or ganglion, that causes pain to a

specific organ or body region can be blocked with local anesthetics.

Trigeminal nerve blocks (face) ;

Maxillary nerve block (upper jaw) ;

Cervical epidural, thoracic epidural, and lumbar epidural block (neck and back) ;

Brachial plexus block, elbow block, and wrist block (shoulder/arm/hand, elbow, and wrist)

Femoral block - The femoral block is used for surgery involving the knee.Popliteal and saphenous nerve blocks are used for surgery involving the foot and ankle.

Sedation Anesthesia, or sedation analgesia, is generally used to supplement regional or local anesthesia

techniques in order to increase a patient's comfort and peace of mind. Can be minimal, moderate, deep.

Spinal & Epidural Anesthesia

Physiologic effects

CARDIOVASCULARSympathectomy (spinal> epidural) loss of vascular tone hypotension & reflex tachycardia.

Supra-T4 levels block cardioaccelerator fibers (T1-T4) paradoxical bradycardia decreased CO &

further hypotension; large volumes of local anesthetic used for epidurals higher systemic absorption

direct cardiac depressant effects !!

PULMONARY


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Impaired cough reflex, high blockade .J, use of accessory resp muscles (intercostals) use caution in pts

with limited pulmonary reserve.

Inspiratory fx preserved (unless respiratory centers (C3-CS) blocked).

GI

Sympathectomy hyperperistalsis (get unopposed parasympathetics)N/V

GU

Sacral blockade atonic bladder (consider catheterization); renal blood flow usually maintained

Complications of neuraxial anesthesia

Backache, Prurius.

Hypotension - Consider volume loading 500-1000 mLfluid to avoid effects of rapid sympathectomy. A

vasoconstrictor, such as ephedrine in 36 mg intravenous increments, can be given to restore normal

arterialpressure.

Accidental IV injection - minimised by aspiration of the catheter and by giving small incremental doses. If

blood is aspirated, usually the catheter is removed and the epidural resited in a different space.

Accidental dural puncture occurs when the needle or catheter is inserted into the cerebrospinal fluid. If

this is not recognised and a full epidural dose of local anaesthetic is injected into the wrong place, a

massive spinal anaesthetic will result, with apnoea, severe hypotension and total paralysis. The lungs

have to be ventilated and the circulation supported during this period. For this reason, an epidural test

dose of 23 ml of local anaesthetic is given by many anaesthetists before the full dose is injected.

Urinary Retention

Nerve Injury

Infection,

Hematoma.

Cauda Equina syndrome occurs with repeated administration of LA. CES implies, clinical manifestations

are related to injury to the nerve roots below the conus medullaris. Bowel/bladder incontinence, and/or

neurologic impairment.

Postspinal headache - commonly occurs 24 to 48 hr after dural puncture. The smaller the diameter of

the needle, the lower the incidence of headache (>24G). Pencil-tip spinal needles, such as Whitacre andSprotte, split, rather than cut, the dura and also reduce the risk of headache. Orientation of the bevel of

cutting-tip needles parallel to the long axis of the dura, which may produce a smaller rent in the dura

because of the longitudinal splitting of fibers, as opposed to direct transection (cutting). Epidural blood

patch.

High/total spinal blockade - supracervical blockadecan cause cardiovascular collapse,apnea, loss of

consciousness; supportive treatment/intubation maybe necessary.


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Spinal cord injury - can occur ifwet tap occurs at levelabove where spinal cord ends.

LA Toxicity

Adverse reactions to local anesthetics are either systemic or localized (e.g., direct neurotoxicity).

Systemic toxicity involves primarily the central nervous system (CNS) and the cardiovascular system

(CVS).

CNS - Early symptoms of local anesthetic-induced CNS toxicity include perioral numbness,

lightheadedness or dizziness, tinnitus, difficulty. focusing visually, paresthesia, disorientation, and

drowsiness. As the local anesthetics plasma concentration increases, common signs include dysarthria,

skeletal muscle twitching, and tremors; these can progress to generalized tonic-clonic seizures.With still

higher plasma concentrations, CNS toxicity may cause unconsciousness, respiratory arrest, and coma.

CVS - Local anesthetics inhibition of cardiac sodium channels reduces the action potential duration, the

effective refractory period, and the maximal depolarization rate of Purkinje fibers and ventricularmuscle. Local anesthetics also exert direct dose-dependent negative inotropic effects on the ventricular

myocardium, which may be related to the blockage of calcium channels. Further, local anesthetics are

peripheral vasodilators and exert potent inhibitory effects on sympathetic smooth muscle

vasoconstriction. CVS toxicity from local anesthetics direct actions on both myocardium and the

peripheral vasculature may present as arrhythmias (refractory ventricular arrhythmias, sinus

bradycardia or arrest), profound hypotension (due to negative inotropic effects or vasodilatation), or

cardiovascular collapse.

Methemoglobinemia is characterized by central cyanosis that is refractory to supplemental oxygen.

Management - depends on the severity of the event. Because plasma levels of local anesthetics

associated with minor reactions fall rapidly, as long as normal metabolic processes are functional, such

events can be allowed to terminate spontaneously, provided attention is paid to maintaining airway

patency and providing supplemental oxygen and hemodynamic support. Seizures can be terminated

with small doses of intravenous midazolam (0.05 to 0.1 mg/kg), sodium thiopental (1 to 2 mg/kg), or

propofol (0.5 to 1.5 mg/kg). If generalized tonic-clonic seizures are not aborted with these doses of

intravenous anesthetics, administration of succinylcholine followed by endotracheal intubation is

indicated. Cardiovascular depression should be treated by fluid resuscitation and vasopressors, if

required. Because hypotension is usually due to a combination of direct myocardial depression and

peripheral vasodilatation, agents with both b1 and a1 activity are recommended: ephedrine or

phenylephrine or both (even epinephrine or norepinephrine) in incremental doses until the desired

response is obtained.With cardiovascular collapse refractory to these drugs, vasopressin should beconsidered. Malignant ventricular arrhythmias should be managed with direct-current cardioversion and

amiodarone if needed to prevent recurrences.

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