Spinal,epidural and caudal anesthesia

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Cousins & Bridenbaugh, 3rd Edition

HISTORY1885 Corning - First attempt with epidural cocaine

1891 Quincke - Describes the lumbar puncture technique1901 use of cocaine as an epidural agent for humans and dogs reported

Alternative to general anesthesia1921 Pagis - First lumbar anesthesia for surgery

1927 E.R. Frank describes use of procaine as a successful alternative1947 Lidocaine commercially available

1949 Curbelo - First continuous lumbar analgesia with Touhy needle1963 Bupivicaine commercially available

1979 Cousins - Epidural opioids provide analgesia1983 Yaksh - Different spinal receptor systems mediating pain

1985 University of Kiel, Germany, Anesthesiology managed acute post-operative pain service

Interest wanes as inhalant anesthesia gains favor

Current Role

• Significant role in modern veterinary and human anesthesia and analgesia

• Important aspect of “balanced anesthesia” concept

Indications• Surgery caudal to the umbilicus– Up to and including thoracic limb if

using morphine• Peritonitis• Severe pancreatitis• Caudal trauma• High risk anesthetic candidates–Dystocia

• Preemptive analgesia

Contraindications

• Absolute– Patient refusal.– Localized infection at skin puncture site.– Generalized sepsis (e.g., septicemia, bacteremia).– Coagulopathy– Increased intracranial pressure.

Contraindications

• Relative– Localized infection peripheral to regional

technique site.– Hypovolemia.– Central nervous system disease.– Chronic back pain.– Inexperience of operator

Segmental level required for surgery

Segmental level required for surgery

Operative Site -----------------------------Level• Lower extremities T-12• Hip T-10• Vagina, uterus T-10• Bladder, prostate T-10• Lower extremities with tourniquet T-8• Testis, ovaries T-8• Lower intraabdominal T-6• Other intraabdominal T-4

Local Anesthetics

Aminoamide-linked drugs: Bupivicaine, lidocaine Aminoester-linked drugs: procaine , tetracaine• Agents reversibly bind to neuronal voltage-gated

sodium channels and block nerve impulse conduction

• Affect segmental nerve roots• Individual pharmacodynamics of agents depend on

lipid solubility, dissociation constant, protein-binding characteristics

Local Anesthetics

• Effects based on myelination and size• Smaller sensory and ANS fibers affected 1st • Sensation disappears in following order:– Pain– Cold– Warmth– Touch– Joint– Deep pressure

• Recovery in reverse order

Local Anesthetics

• surface anaesthesia——tetracaine• infiltration anaesthesia——procaine,

lidcaine etidocaine, ropivacaine, • conduction anaesthesia——lidcaine,

procaine, bupivacaine , etidocaine• spinal(subarachnoidal) anaesthesia——

lidcaine, tetracaine, procaine• epidural anaesthesia ——lidcaine,

tetracaine, procaine, bupivacaine ,ropivacaine, etidocaine

Spinal anesthesia

• Spinal anesthesia involves administering local anesthetic into the subarachnoid space.

• The spinal canal extends from the foramen magnum to the sacral hiatus. The boundaries of the bony canal are the vertebral body anteriorly, the pedicles laterally, and the spinous processes and laminae posteriorly

Spinal anesthesia

Three interlaminar ligaments• supraspinous ligament• interspinous ligament• ligamentum flavum

Spinal anesthesia

The spinal cord is invested in three meninges

The pia mater The dura mater The arachnoid

Spinal anesthesia

subarachnoid space Extends from the attachment of the dura at

S-2 to the cerebral ventricles above. The space contains the spinal cord, nerves, cerebrospinal fluid (CSF), and blood vessels that supply the cord.

Spinal anesthesia

Physiological changes• Neural blockade• Cardiovascular. Hypotension • Respiratory• Visceral effects• Neuroendocrine• Thermoregulation• Central nervous system effects

Spinal anesthesia• Determinants of spread

Major factors Baricity of solution Position of patients (except isobaric solution) Dose and volume of drug injected (except isobaric) Minor factors Level of injection Speed of injection/barbotage Size of needle Physical status of patients Intra-abdominal pressure

• Determinants of duration Drug used Dose injected Presence of vasoconstrictors Total spread of blockade

Spinal anesthesia

ComplicationsNeurologic Transient paresthesias ， Spinal hematoma ， back pain ， Bloody tap ， Transient

neurologic syndrome ， Postdural puncture headache

Cardiovascular Hypotension,Bradycardia

Respiratory Apnea, Dyspnea

VisceralNausea and vomiting, Urinary retention

Infection

Spinal anesthesia

• 16ga=1.191mm• 18ga=1.024mm• 20ga=0.812mm

Epidural anesthesia

Needle selection– Shorter bevels– Steel stylet– Longer length– Duller tip

Correct placement of needle• Hanging drop technique• Air leakage• Loss of resistance• Whoosh test

Epidural anesthesia

Epidural anesthesia is achieved by introducing local anesthetics into the epidural space

Physiology• Neural blockade• Cardiovascular• Respiratory• Coagulation• Gastrointestinal

Epidural anesthesiaDeterminants of the level of epidural blockade• Volume of local anesthetic• Age. • Pregnancy• Speed of injection.• Position• Spread of epidural blockade.Determinants of onset and duration of epidural blockade Selection of drug.• Addition of epinephrine• Addition of opioid. • pH adjustment of solution.

Epidural anesthesiaComplications

1. Dural puncture 2. Bloody tap3. Catheter complications ： The catheter can be inserted into

an epiduralvein ， Inability to thread the epidural catheter ， Catheters can break off or become knotted ， Cannulation of the subdural space

4. Intravascular injection5. Unintentional subarachnoid injection6. Local anesthetic overdose.7. Epidural hematoma8. Postdural puncture headache. 9. Epidural abscess10.Direct spinal cord injury

Caudal anesthesia

Caudal anesthesia is obtained by placing local anesthetic into the epidural space in the sacral region

Complications The complications of caudal anesthesia are similar to those of epidural anesthesia

Caudal anesthesia

Caudal anesthesia

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