conduct of regional anaesthesia
TRANSCRIPT
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CONDUCT OF REGIONAL ANAESTHESIA
Dr.Charulatha.R MDAssistant ProfessorMGMCRI
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August Bier 1885
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SPINAL CORD
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Flow of CSF
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Where Spinal Cord Ends
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Cauda Equina
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BLOOD SUPPLY TO SPINAL CORD
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100% Sterile
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Spinal Anaesthesia
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Holding for Spinal
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Sitting Position
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Flexion
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Structures Pierced
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Spinal Needle
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Factors Influence The Level Of Anaesthesia The level of
Injection The volume of
drug Tilt of Table Speed of
Injection
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Advantages of spinal anaesthesia
• Full and complete anaesthesia• Prolonged block: Pain free postoperatively• Alternative to GA for certain poor risk patients esp.:- Difficult airway- Respiratory disease• Contracted bowel• Good muscle relaxation• Suitable for certain surgical procedures:-
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Caesarian section (awake patient, bonding)
-Lower limb surgery
-Lower abdominal surgery
- Urological & gyneacological procedures.
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SITTING / LYING
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Reason For the Patho physiological Changes
Blockade of the Sympathetic Systems
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Cardivascular Changes Hypotension
Tachycardia
Bradycardia
Sympathetic Blockade
Marys law/Mayos Reflex
Bainbridge Reflex
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Drug for Spinal Anaesthesia Lignocaine Bupivacaine
Hyperbaric Stay in the
lowest area as per gravity
5% with Glucose
0.5% with Glucose
Does not mix up with CSF
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Complications On Table
Delayed
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On Table Complication Hypotension IV Isotonic
Fluids Vasopressors Oxygen by
mask Atropine-
Bradycardia
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Pregnancy & Spinal Aortocaval
Occlusion Pre loading
with IV Fluids Left lateral
Position Vasopressors Oxygen therapy
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Delayed Complication Head ache Sixth Cranial
nerve palsy Infection
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How to prevent Delayed Complication
Use Thin Spinal needles
Sterile Precaution
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Indication Economical Pulmonary Diseases Full Stomach Lower Abdominal Surgery Ischemic Heart Diseases for Lower
Abdominal Surgery
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Relative Contraindication Hypotensive Patients Cardiac failure Raised ICT Spinal Deformity Refusing Patients Bleeding Diathesis Skin Infection
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Introduction to Epidural Anesthesia Epidural anesthesia produces a reversible
loss of sensation and motor function much like a spinal with the exception that local anesthetic is placed within the epidural space.
Larger doses of local anesthetic are required to produce anesthesia when compared to a spinal anesthetic.
Doses must be monitored to avoid toxicity.
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Introduction to Epidural Anesthesia An epidural catheter allows the
versatility to extend the duration of anesthesia beyond the original dose by the administration of additional local anesthetic.
Epidural catheters may be left in place for postoperative analgesia.
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Epidural Anesthesia Indications Cesarean section Procedures of the uterus, perineum* Hernia repairs Genitourinary procedures Lower extremity orthopedic procedures Excellent choice for elderly or those who
may not tolerate a general anesthetic
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Epidural Anesthesia Should NOT be used in patients who are
hypovolemic or severely dehydrated. Patients should be pre-hydrated with .5 –
1 liter of crystalloid solutions (i.e. ringers lactate) immediately prior to the block.
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Epidural Anesthesia Higher failure rate for procedures of the
perineum. Lower lumbar and sacral nerve roots are
large and there is an increased amount of epidural fat which may affect local anesthetic penetration and blockade.
This is known as sacral sparing.
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Epidural Anesthesia Advantages Easy to perform (though it takes a bit
more practice than spinal anesthesia) Reliable form of anesthesia Provides excellent operating conditions The ability to administer additional local
anesthetics increasing duration The ability to use the epidural catheter
for postoperative analgesia
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Epidural Anesthesia Advantages Return of gastrointestinal function
generally occurs faster than with general anesthesia
Patent airway Fewer pulmonary complications compared
to general anesthesia Decreased incidence of deep vein
thrombosis and pulmonary emboli formation compared to general anesthesia
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Epidural Anesthesia Disadvantages Risk of block failure. The rate of failure is
slightly higher than with a spinal anesthetic. Always be prepared to induce general anesthesia if block failure occurs.
Onset is slower than with spinal anesthesia. May not be a good technique if the surgeon is impatient or there is little time to properly perform the procedure.
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Epidural Anesthesia Disadvantages Normal alteration in the patient’s blood pressure
and potentially heart rate (generally slower onset with less alteration in blood pressure and heart rate than with a spinal anesthetic). It is essential to place the epidural block in the operating room/preoperative area with monitoring of an ECG, blood pressure, and pulse oximetry. Resuscitation medications/equipment should be available.
Risk of complications as outlined in Introduction to Neuraxial Blockade chapter. There is an increase in the complication rate compared to spinal anesthesia.
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Epidural Anesthesia Disadvantages Continuous epidural catheters should not
be used on the ward if the patient’s vital signs are NOT closely monitored.
Risk for infection, resulting in serious complications.
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Absolute Contraindications Epidural Patient refusal Infection at the site of injection Coagulopathy Severe hypovolemia Increased Intracranial pressure Severe Aortic Stenosis Severe Mitral Stenosis Ischemic Hypertrophic Sub-aortic
Stenosis
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Relative Contraindications Sepsis Uncooperative patients Pre-existing neuro deficits/neurological
deficits Demylenating lesions Stenotic valuvular heart lesions (mild to
moderate Aortic Stenosis/Ischemic Hypertrophic Sub-aortic Stenosis)
Severe spinal deformities
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Controversial Prior back surgery Inability to communicate with the patient Complicated surgeries that may involved
prolonged periods of time to perform, major blood loss, maneuvers that may complicate respiration
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Mechanism/Site of Action Administered at a physiologic distance
when compared to spinal anesthesia. The intended targets are the spinal nerves and associated nerve roots.
Several barriers to the spread of local anesthetic to the intended site of action results in the requirement of larger volumes of local anesthetic when compared to spinal anesthesia.
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Barriers Dura mater between the epidural space
and spinal nerve and nerve roots act as a modest barrier.
The majority of the solutions is absorbed systemically through the venous rich epidural space.
Epidural fatty tissue acts as a reservoir. The remainder reaches the spinal nerve
and nerve roots.
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Spread of Local Anesthetic in the Epidural Space Local anesthetic injected into the
epidural space moves in a horizontal and longitudinal manner.
Theoretically the longitudinal spread could reach the foramen magnum and sacral foramina if enough volume was injected.
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Spread of Local Anesthetics- Longitudinal
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Spread of Local Anesthetics- Horizontal Horizontally the local anesthetic spreads
through the intervertebral foramina to the dural cuff.
Local anesthetics spread through the dural cuff via the arachnoid villa and into the CSF.
Blockade occurs at the mixed spinal nerves, dorsal root ganglia, and to a small extent the spinal cord.
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Spread of Local Anesthetics- Horizontal
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Spread of Local Anesthetics- Local anesthetics gain access to CSF via arachnoid granules
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Distribution, Uptake & Elimination Takes 6-8 times the dose of a spinal
anesthetic to create a comparable block.
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This is due to: Larger mixed nerves are found in the
epidural space when compared to the subarachnoid space.
Local anesthetics must penetrate arachnoid and dura mater.
Local anesthetics are lipid soluble and will be absorbed by tissue and epidural fat.
Epidural veins absorb a significant amount of local anesthetic with blood concentrations peaking in 10-30 minutes after a bolus.
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Distribution, Uptake & Elimination Local anesthetics absorbed in the
epidural veins will be diluted in the blood.
The pulmonary systems acts as a temporary buffer and protects other organs from the toxic effects of local anesthetics.
Distribution occurs to the vessel rich organs, muscle, and fat.
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Distribution, Uptake & Elimination Long acting amides will bind to alpha-1
globulins which have a high affinity to local anesthetics but become rapidly saturated.
Amides are metabolized in the liver and excreted by the kidneys.
Esters are metabolized by pseudocholinesterase so rapidly that there are rarely significant plasma levels.
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Factors Affecting Height of Epidural Blockade Volume of local anesthetic Age Height of the patient Gravity
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Volume Can be variable General rule: 1-2 ml of local anesthetic
per dermatome i.e. epidural placed at L4-L5; you want a
T4 block for a C-sec. You have 4 lumbar dermatomes and 8 thoracic dermatomes. 12 dermatomes X 1-2 ml = 12-24 ml
Big range! Stresses importance of incremental dosing!
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Volume If you require only segmental anesthesia
than the dose would be less. Volume of local anesthetic plays a
critical role in block height. Dose of local anesthetics administered in
thoracic area should be decreased by 30-50% due to decrease in compliance and volume.
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Age As age increases the amount of local
anesthetic to achieve the same level of anesthesia decreases. A 20 year old vs 80 year old
This is due to changes in size and compliance of the epidural space
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Height The shorter the patient the less local
anesthetic required. A patient that is only 5’3” may require 1
ml per dermatome while someone who is 6’3” may require the full 2 ml per dermatome
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Gravity Position of patient does affect spread and
height of local anesthetic BUT not to the point of spinal anesthesia.
i.e. lateral decubitus position will “concentrate” more local anesthetic to the dependent side will a weaker block will occur in the non-dependent area.
A sitting patient will have more local anesthetic delivered to the lower lumbar and sacral dermatomes
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Gravity L5-S2 sometimes will have ‘patchy’
anesthesia due to sparing. By having the patient “sitting” or in a semifowlers position one can concentrate local anesthetic to this area.
Trendelenberg or reverse trendelenberg may help spread local anesthetic cephalad or alternatively limit the spread.
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Local Anesthetics used for Epidural Anesthesia
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Considerations in choosing Understanding of local anesthetic
potency & duration Surgical requirements and duration of
surgery Postoperative analgesic requirements
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Local Anesthetics for Epidural Anesthesia Use only preservative free solutions Read the labels, ensure that it is
preservative free or prepared for epidural/caudal anesthesia/analgesia
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Categories according to duration of action Short Acting: 2-chloroprocaine Intermediate Acting: lidocaine and
mepivacaine Long Acting: bupivacaine, etidocaine,
ropivacaine, levobupivacaine
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Intermediate Acting Lidocaine Prototypical amide local anesthetic 1.5-2% concentrations used for surgical
anesthesia Epinephrine will prolong the duration of
action by 50% Addition of fentanyl will accelerate the
onset of analgesia and create a more potent/complete block
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Intermediate Acting Lidocaine
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Lignocaine Dose 3mg /kg
7mg/kg with adrenaline
Prolong action/reduces the toxicity
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Long Acting Bupivacaine Long acting amide local anesthetic 0.5-0.75% concentrations used for
surgical anesthesia 0.125-.25% used for epidural analgesia Epinephrine will prolong duration of
action but not to the extent of lidocaine, mepivacaine, and 2-chloroprocaine
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Long Acting Bupivacaine 0.75% concentration should not be used in OB In 1983 the FDA came out with this
recommendation There were several cardiac arrests due to
inadvertent intravascular injection in OB patients
Bupivacaine (as well as etidocaine) are more likely to impair the myocardium and conduction system with toxic doses than other local anesthetics
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Long Acting Bupivacaine Bupivacaine has a high degree of protein
binding and lipid solubility which accumulate in the cardiac conduction system and results in the advent of refractory reentrant arrhythmias
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Long Acting Bupivacaine
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Bupivacaine Longacting 4-6 hours Deferential blockers
-Sensory more than Motor-Dose- 1-1.5 mg/kg-Cardiac Toxic-No Tachyphylaxis- Repeat drug
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Long Acting Levobupivacaine S isomer of bupivacaine Used in the same concentrations Clinically acts just like bupivacaine with
the exception that it is less cardiac toxic
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Long Acting Levobupivacaine
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Long Acting Ropivacaine Long acting amide local anesthetic Mepivacaine analogue Used in concentrations of 0.5-1% for surgical
anesthetic Used in concentrations of 0.1-0.3% for
analgesia Ropivacaine is unique among local
anesthetics since it exhibits a vasoconstrictive effect at clinically relevant doses
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Long Acting Ropivacaine Similar to bupivacaine in onset, duration,
and quality of anesthesia Key differences include: in doses for
analgesia there is excellent sensory blockade with low motor blockade and it is less cardiotoxic than bupivacaine
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Long Acting Ropivacaine
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Local anaesthetic systemic toxicity Tingling sensation around mouth Drowsiness Hypotension seizures Treatment ABC Midazolam /thiopentone intralipid
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Epidural Additives Epinephrine will increase the duration of action
of all epidurally administered local anesthetics. There is a large variability among local
anesthetics as to the degree of increase The greatest effect is found with lidocaine,
mepivacaine, 2-chloroprocaine. Lesser effects found with bupivacaine,
levobupivacaine, etidocaine Minimal effects have been found with
ropivacaine
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Epidural Additives Epi vs phenylephrine Epi is more effective in reducing peak
blood levels Phenylephrine does not appear to
reduce the peak blood levels
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Epidural Additives Carbonation of local anesthetics has been
touted to improve the quality of epidural blocks due to increased penetration of connective tissue and intraneural diffusion
Studies are ambivalent Carbonation may not improve quality or
onset; may lead to increased blood levels of local anesthetic; result in a higher incidence of hypotension when compared to non carbonated local anesthetics
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Epidural Additives Sodium bicarbonate can be added to
lidocaine, mepivacaine, and 2-chloroprocaine
Addition will increase the amount of free base which increases rate of diffusion and speeds onset
Studies have found that when added to 1.5% lidocaine speeds onset of blockade and results in a more solid block
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Epidural Additives Generally 1 meq of bicarbonate is added
to 10 ml of local anesthetic (i.e. lidocaine, mepivacaine, 2-chloroprocaine)
The addition of bicarbonate to bupivacaine is not as popular. Usually 0.1 ml of bicarbonate is added to 10 ml of bupivacaine
Bupivacaine precipitates occurs at a pH > 6.8
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Epidural Additives Mixing long acting and short acting local
anesthetics may not have much advantage for epidural anesthesia
Many choices for local anesthetics and additives
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Thank you