Regional anaesthesia

Ahmed Al-MomtanAl-Khaldi, Al-Sha’alan, Hizjazi, Abbas

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Definition

• Rendering a specific area of the body insensitive to nociceptive stimulus during and after the surgical procedure.

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Regional anaesthesia

• Objectives• Describe anatomy of spinal canal• Identify anatomic landmarks for proper placement of a spinal

needle• Define appropriate steps for placement of spinal and epidural.• Distinguish level of anaesthesia after administration of regional• State factors affecting level and duration of spinal vs. epidural

block• Explain potential complications and corresponding treatments

associated with administration of regional anaesthetics

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Spinal Anatomy

• 33 Vertebrae• 7 Cervical• 12 Thoracic• 5 Lumbar• 5 Sacral• 4 Coccygeal

• High Points: C5 & L5• Low Points: T5 & S2

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Spinal Cord• Spinal Cord

• Adult• Begins: Foramen Magnum• Ends: upper border of L2

• Newborn• Begins: Foramen Magnum• Ends: upper border of L3

• Terminal End: Conus Medullaris• Filum Terminale: Anchors in sacral region• Cauda Equina: Nerve group of lower dural sac

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Saggital Sections• Supraspinous Ligament

• Outer most layer

• Intraspinous Ligament• Middle layer

• Ligamentum Flavum• Inner most layer

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Epidural Space

• Space that surrounds the spinal meninges• Potential space

• Ligamentum Flavum• Binds epidural space

posteriorly• Widest at Level L2 (5-6mm)• Narrowest at Level C5 (1-1.5mm)

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Epidural Anatomy

• Safest point of entry is midline lumbar

• Spread of epidural anaesthesia parallels spinal anaesthesia• Nerve rootlets• Nerve roots• Spinal cord

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Spinal Meninges• Dura Mater

• Outer most layer• Fibrous

• Arachnoid• Middle layer• Non-vascular

• Pia• Inner most layer• Highly vascular

• Sub Arachnoid Space• Lies between the

arachnoid and pia10

Spinal Pharmacology

• Vasoconstrictors• Prolong duration of spinal block• No increase in duration with lidocaine &

bupivacaine• Significant increase with tetracaine

(double duration)

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Spinal Pharmacology• Factors Effecting Distribution

• Site of injection• Shape of spinal column• Patient height• Angulation of needle• Volume of CSF• Characteristics of local anaesthetic

• Density• Specific gravity• Baracity

• Dose• Volume• Patient position (during & after) 12

Spinal Pharmacology

• anaesthesia level is determined by patient position• Uptake of local anaesthetic occurs by diffusion• Elimination determines duration of block

• Lipid solubility decreases vascular absorption• Vasoconstriction can decrease rate of elimination

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Patient Evaluation

• Patient selection- Age appropriate, cognitive limitations

• Risks and benefits and consent- Discussion to include common side effects and complications

• Appropriate for surgery- To include duration of surgery.

• NO contraindications?- Patient factors or medications, Relative vs abslute.

• Laboratory testing?- platelets/INR/PT/aPTT

• Combination of regional/general- Using as primary technique or as MAC reducer or for Post-op mgmt

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Positioning..• Sitting

- Visually the easiest• Lateral

- Used when sitting impractical or contraindicated

• Prone- Hyperbaric techniques, lower ext. or

rectal.

• Autonomic >> Sensory >> Motor

( Differential Blockade)

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Spinal Anaesthesia

• form of regional anaesthesia involving injection of a local anaesthetic into the Subarachnoid space (CSF)

• Easy to perform, has the potential to provide excellent operating conditions for surgeries below the umbilicus.

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Advantages of Spinal Anaesthesia• Cost.• Patient satisfaction; many patients are very happy with this technique. • Respiratory disease. few adverse effects on the respiratory system as long as

unduly high blocks are avoided.• Patent airway..• Diabetic patients. There is little risk of unrecognised hypoglycaemia in an awake

patient. Diabetic patients can usually return to their normal food and insulin regime soon after surgery as they experience less sedation, nausea and vomiting.

• Muscle relaxation..• Blood loss less• Visceral tone. The bowel is contracted during spinal anaesthesia and sphincters

are relaxed although peristalsis continues. Normal gut function rapidly returns following surgery.

• Coagulation. Post-operative deep vein thromboses and pulmonary emboli are less common following spinal anaesthesia

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• This technique is very useful in patients having an

irritable airway (bronchial asthma or allergic bronchitis), • anatomical abnormalities which make endotracheal

intubation very difficult (micrognathia), • borderline hypertensives where administration of general

anaesthesia or endotracheal intubation can further elevate the blood pressure,

• procedures in geriatric patients. • technique of choice for diabetic patients.

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Spinal Technique

• Midline Approach• Skin• Subcutaneous tissue• Supraspinous ligament• Interspinous ligament• Ligamentum flavum• Epidural space• Dura mater• Arachnoid mater

• Paramedian or Lateral Approach• Same as midline excluding supraspinous &

interspinous ligaments 19

Spinal anaesthesia Levels

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Spinal anaesthesia

• Indications & Advantages• Patient request• Full stomach• Anatomic distortions of upper airway• TURP surgery• Obstetrical surgery (T4 Level)• Decreased post-operative pain• Continuous infusion

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• Abdominal & vaginal hysterectomies • Caesarean sections • Hernia (inguinal or epigastric) • Piles fistulae & fissures • orthopaedic surgeries on the pelvis, femur, tibia and the ankle • nephrectomy • cholecystectomy • trauma surgery on the lower limbs, especially if the patient is full-stomach • Open tubectomies • Transurethral resection of the prostate

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Drugs used..

• Either hyperbaric, isobaric or hypobaric,, hyperbaric bellow the level of injection.., hypobaric is independent >> depends on the position>> lighter anaesthtic will ascend upward!

• Isobaric diffused.• bupivecaine: 0.5% hyperbaric bupivecaine

is the best to use if availble. It lasts longer than most spinal anaesthetics (2-3 hours).

• Lidocaine hyperbaric 5% lasts for 45-90 mins.

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Spinal anaesthesia• Contraindications

• Absolute:• Refusal

• Uncooperative patients “handicapped, psychiatric problems,,”

• Infection

• Coagulopathy

• Severe hypovolemia

• Increased intracranial pressure

• Severe aortic or mitral stenosis

• Relative:• Use your best judgment; anatomical deformities….

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Spinal anaesthesia• Complications

• Failed block• Hypotension >> due to sympathetic block >> give ephedrine

(selective agonist of alpha receptors)• Back pain (most common)• Spinal headache

• More common in women ages 13-40• Larger needle size increase severity• Onset typically occurs first or second day post-op• positional• Treatment:

• Bed rest

• Fluids, Fluids and Fluids..

• Caffeine

• Blood patch (clot)

• Infection25

Spinal anaesthesia

• Spread of Local anaesthetics• First to cauda equina• Laterally to nerve rootlets and nerve

roots• May defuse to spinal cord• Primary Targets:

• Rootlets• Roots• Spinal cord

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Epidural Anaesthesia

• Injection of local anaesthetic in to the epidural space at any level of the spinal column

• The aim is analgesic rather than anaesthetic..(i.e in child delivery we don’t need motor block, we just need pain reception block)

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Epidural anaesthesia

• Distances from Skin to Epidural Space• Average adult: 4-6cm• Obese adult: up to 8cm• Thin adult: 3cm

• Assessment of Sensory Blockade• Alcohol swab

• Most sensitive initial indicator to assess loss of temperature

• Pin prick• Most accurate assessment of overall

sensory block

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Indications (general)

• anaesthetic for procedures involving the lower limbs, pelvis, perineum and lower abdomen

• postoperative analgesia• maintain continuous anaesthesia after

placement of an epidural catheter

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Indications (specific)

• Hip and Knee Surgery

• Lower Extremity Vascular Surgery

• Lower Extremity Amputation

• Obstetrical – Labor & C/S

• Thoracic Surgery– Post-Op Pain Control

• Thoracic Trauma

• Abdominal Surgery – Post-Op Pain Control

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Epidural anaesthesia

• Complications• Epidural haematoma• Penetration of a blood vessel• Hypotension (nausea & vomiting)• Headache• Back pain• Intravascular catheterization• Wet tap• Infection

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Sensory vs. Motor Blockade

• Spinal Injection• Sympathetic block is 2-6 dermatomes

higher than sensory block• Motor block is 2 dermatomes lower

than sensory block

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Bier block

• IV regional anesthesia• August Bier, 1908• Modern version, 1963s by holmes.• Rapid and reasonable muscle

relaxation.

- Two conditions:1. Procedures in the arm below the

elbow or leg below the knee.

2. Completed within 40-60 mins.

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Procedure

• Exsanguination• Gravity or compression with bandage

• Tourniquet• Pneumatic cuff to 250 mm Hg in arm

or 50 mm Hg > SBP

• Medicine• Of choice is “Prilocaine” least

toxic, largest TI. • If not availble lidocaine is an

acceptable alternative.• In the arm dosage can be: 30-40 ml

of 0.5% prilocaine or 0.5 % lidocaine.• In leg, larger volumes 50-60 ml.

• Procedure after 3-6 minutes

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Post-procedure

• Deflate for a few seconds

• Re-inflate for a minute

• Rinse, lather, and repeat

• Observe for 15 minutes

• Discharge

• By no means the tourniquet can be deflated untill at least 20 mins since injection

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Bier block: Advantages

• No need for NPO status• Pt is awake during procedure.• Shorter post-procedural observation time

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Bier block: Disadvantages

• Lose pulse• Possible superficial nerve damage• Unable to splint or cast with tourniquet

inflated

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Bier block: Adverse Events

• Tourniquet pain• At IV site: blotchy erythema,

flushing, urticaria• Dizziness, metallic taste in mouth,

tingling• Tourniquet fails Lidocaine bolus:

• Headache, lethargy, slurred speech, seizure

• Hypotension, bradycardia

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Bier block: Contraindications

• if tourniquet cannot safely be used.• Sickle cell disease (homozygous) or

reynaud’s• Shock• Multiple trauma (crush injuries of relevant

limb)• Hypersensitivity to Prilocaine or lidocaine• Seizure disorder

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Bier Block: Controversies

• Dose of lidocaine• Volume of lidocaine infusion• Other meds

• Instead of lidocaine• In addition to lidocaine

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Bier block: Indications

• Closed fractures• Burn debridement• Removal of ground-in debris• Abscess I&D• Laceration repair• Foreign body removal• Limited surgical procedures

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Thank u..

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