Regional Anesthesia

Regional Anesthesia

• Regional anesthesia is the use of local anesthetics to block pain sensations in a large area of the body, such as an arm, leg, or the abdomen
• A procedure can be performed on a region of the body without the patient losing consciousness under regional anesthesia
• Combining regional anesthesia with analgesia, or using it with general anesthesia, can provide excellent operating conditions in addition to prolonged postoperative pain relief
• Regional anesthesia can promote faster rehabilitation and return to normal function by enabling postoperative mobilization, as well as early feeding

Relative Indications to Use Regional Anesthesia

• To mitigate risks associated with general anesthesia, which includes difficult tracheal intubation and severe respiratory failure
• When problems are predicted with muscle relaxants or general anesthetics
• In patients who specifically request regional anesthesia
• To provide high-quality postoperative pain relief
• As a component of a postoperative rehab program that helps patients return to function sooner

Relative Contraindications for Regional Anesthesia

• Uncooperative or restless patients
• Certain psychiatric patients

Steps Before Injecting Local Anesthetic:

• Establish an indwelling intravenous cannula

• Make sure there is tilting table or trolley

• Intermittent IPPV with oxygen must be available

• Patient monitoring needs to be in place, featuring ECG, noninvasive blood pressure, pulse oximetry, and end-tidal carbon dioxide monitoring if general anesthesia is needed

• Suction equipment and catheters

• Have syringes/ampules of tranquilizers such as midazolam, induction agents like Propofol, muscle relaxants e.g. Suxamethonium, atropine, and pressor agents such as ephedrine

• Have crystalloid and colloid solutions for infusion

• All resuscitation equipment and drugs must be present, including a defibrillator

Types of Regional Anesthesia

• Peripheral nerve blocks involve injecting a local anesthetic near a specific nerve or bundle of nerves to block pain sensations
• Nerve blocks are commonly used for surgeries on the arms, hands, legs, feet, groin, or face

IV Regional Anesthesia – Bier’s Block

• A peripheral nerve block technique performed on body extremities, ideally suited for operations of the distal arm/leg like radial/ulna fracture reductions
• IVRA is suited to short surgical procedures of 40 minutes or less, length defined by tourniquet pain development, usually after 40-60 minutes
• Target region exsanguination first forces blood from the extremity before a pneumatic tourniquet is applied, inflated to 100mmHg above systolic blood pressure to safely stop blood flow
• The limb is intravenously administered an anesthetic agent, dispersing into surrounding tissue while tourniquets keep the medication in the target area
• Insertion of two IV cannulas should be done; one for venous cannulation away from the tourniquet, and one in a non-targeted arm in case access to circulation is required if complications arise
• Lidocaine or prilocaine should be administered at a dose of 3 – 4 mg/kg of 0.5% plain solution
• Bupivacaine should never be introduced given that is can lead to cardiotoxicity, potentially causing ventricular arrhythmias and death

Bier's Block Contraindications

• Crush injury to the limb, IVRA may provoke further tissue damage from hypoxia
• Reynold's disease (intermittent arteriolar vasospasm of distal limbs)
• Sickle cell anemia
• Scleroderma

Ultrasound Guided Regional Anesthesia (USGRA)

• Ultrasonography (US) to guide peripheral nerve blockade (PNB) was first explored by anesthesiologists at the University of Vienna in the mid-1990s
• Radiologists had used ultrasound for needle guidance for biopsy, application of the imaging was a novel approach for PNB
• Demonstrates utility to facilitate a range regional anesthesia techniques, namely for brachial plexus and femoral blocks
• A decade later, researchers from the University of Toronto in Canada began to embrace and demonstrate its utility describing the sonoanatomy of the brachial plexus in detail

Transversus Abdominis Plane (TAP) Block

• A local anesthetic to block analgesia for the anterior and lateral abdominal wall
• The technique described offers an anatomical landmark and shows blockade evidence down to the mid/lower thoracic and upper lumbar spinal nerves as they travel in the fascial plane between the transversus abdominis and internal oblique muscles
• Later, the TAP block was aided by an ultrasound-guided approach

TAP Block Indications

• As part of an analgesic regimen for abdominal surgery

• Initial studies were able to demonstrate blocks extending from T7-L1 with bilateral injections

• Most studies only achieve uppermost sensory levels around T9/10, conflicting with initial findings

• The lower block is supported by findings in a cadaver study, looking at spread of local anesthetic after a single posterior TAP injection

• TAP block can only reliably be used for analgesia in surgery on the lower abdomen: hernia repair, open appendicectomy, Caesarian section, total abdominal hysterectomy, radical prostatectomy

• A local anesthetic injection near the spinal cord and major nerves that enter the spinal cord to block sensations of pain from an entire region of the body, for example, the lower abdomen, hips, or legs

Caudal Block

• Local anesthetic injected into the epidural space through the sacral hiatus to obtain anesthesia of sacral and coccygeal nerve roots
• Commonly used for superficial operations such as skin grafting, perineal procedure, and lower limb surgery

Spinal (intradural) Anesthesia

• The spinal cord usually terminates at L1 in adults, and L3 in children

• Dural puncture above these levels carries a risk of spinal cord damage; avoid when possible

• A line joining the top of the iliac crests is at L4 to L4/5; an important landmark to keep in mind

• Spinal blockade provides Surgeries of lower limbs, perineum, pelvis, abdomen support

• Ideal for patients with Renal failure by two or three segments,

• Procedures involving duration shorter

• Avoidance of Cardiac and Liver disease

• Avoidance of Obstetric anesthesia

• When the patient has a Full stomach

• In people with Anatomic distortions of upper airway

• During a TURP surgery

The Level of Block

• Sympathetic paralysis, Sensory block, and Motor nerve blockade are correlated to spinal block depth

The Technique

• Involves injecting a local anesthetic using a much smaller needle in the cerebrospinal fluid around the spinal cord
• The needle is inserted between the third and fourth lumbar vertebrae, numbing the area with a local anesthetic
• Post insertion the anesthetic is injected without needing a catheter
• The body is numbed below, sometimes above, the injection site and temporary leg immobilization occurs

Factors Effecting the Distribution of Spinal Block

• Site of injection
• Shape of the spinal column
• Patient height
• Needle angulation
• Volume of CSF
• Density
• Specific gravity
• Dose
• Volume
• Patient position

Cardiovascular Effects

• Blocks preganglionic sympathetic neurons, affecting arteries and veins
• Predominant effect is venodilation which Reduces
• Venous return
• Stroke volume
• Cardiac output
• Blood pressure

Hypotension

• T1-T4 blockade causing unopposed vagal stimulation, leading to bradycardia, decreased venous return, and cardio-accelerator fiber blockade
• Decreased venous return to the right atrium diminishes stretch receptor response, contributing to hypotension
• Treatment best approached with physiologic, and not pharmacologic measures
• Primary treatment focusing on increasing cardiac preload with a large IV fluid bolus of crystalloids (minimum 1 liter), administered 30 minutes prior to spinal placement
• Secondary treatment uses pharmacologic intervention via Ephedrine (more effective than Phenylephrine)

Respiratory Effects

• Appropriate spinal blockade has minimal impact on ventilation
• High spinal blocks Decrease residual functional capacity (FRC)
• Paralysis of abdominal muscles
• Paralysis of intercostal muscles that Interferes with coughing and clearing secretions
• Apnea is due to the lack of proper perfusion of the respiratory center.

Complications

• Immediate: Hypotension, Bradycardia and cardiac arrest, High and total spinal block leading to respiratory arrest, Urinary retention, Epidural hematoma, and Bleeding
• Late term: Post Dural Puncture Headache, Backache, Nausea, focal neurological deficit, bacterial meningitis, Sixth cranial nerve palsy, and urinary retention.

Post Spinal HA

• Higher incidence with women aged 13-40, and with larger needle sizes causing increased severity
• Treatment,
• Maintained Bed rest to relieve any pain
• Administration of high volumes of Fluids to maintain bodily hydration
• Application of Simple analgesia with paracetamol, aspirin, or even codeine may also help
• Intake Caffeine containing drinks
• Application of a Blood patch in cases that resist

Blood Patch

• When applied in the space of the epidermis, CSF pressures increase
• No more than two may be administered
• First patch is effective 95% of the time
• It has to be administered at least 24 hours after the first application

Epidural(Extradural Anesthesia)

• Applies to the space between the dura mater and ligament flavum, an area Made up of vasculature, nerves, fat and lymphatic system
• Extends from foramen magnum to the sacrococcygeal ligament
• The area is segmented and lacks distribution

Spacial Bounds

• Anterior area follows the posterior longitudinal ligament, while Laterally contains the pedicles and intervertebral ligaments, then Posteriorly is defined by ligamentum flavum
• Most wide at level L2 with 5-6mm in width
• Narrowest area is seen at Level C5 with 1-1.5mm
• Ranges from the Epidural space- to a Skin distance
• In Average Adults, 4-6cm (80%) of instances
• In Overweight adults, length extends up to 8cm
• In Skinnier adults, length is 3cm
• Area is 118ml in volume

Epidural Application

• Deposit local anaesthetic in the peridural zone between the dura and periosteum with deposits lining the vertebral track
• Inject local anesthetic that leads to producing analgesia with conduction being blocked as Intradural Spinal Nerve roots carry out conduction

Epidural Technique

• Involves a hollow needle followed by catheter insertion in the cord space, epidural to allow flow
• The area is numbed by anesthetics