1. Regional Anesthesia
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2. Objectives To give an overview of regional anesthesia
To review the anatomy and physiology of spinal and epidural anesthesia

3. Regional Anesthesia Coined by Harvey Cushing
A localized area of the body can be rendered pain free and operated upon without losing consciousness
Involves a block of a spinal nerve with local anesthetics
The introduction of local anesthesia followed that of general anesthesia by about 40 years, starting in 1860 with the numbing effect of cocaine on the tongue. Corning described the use of cocaine in spinal anesthesia in 1885.

4. Pros and Cons of Regional Anesthesia
Simplicity, because the costs are reasonable, agents are easily injected, post-op care is lessened
Decreases the autonomic and endocrine response to stress through interference with afferent nerve conduction
Suitable in cases where patient’s cooperation is required, in patients who are risks for aspiration
Surgery itself produces a stress response. General anesthesia adds to the stress response.

5. Pros and Cons of Regional Anesthesia
Lack of patient acceptance
Impracticality of anesthesizing some body areas
Effects and complications of local anesthetics resulting in morbidities and mortalities
Fear of injections, of being awake during the procedure

6. Neuraxial Blocks Spinal, Epidural, Caudal Anesthesia
Results in sympathetic block, sensory analgesia, and motor block after insertion of a needle and delivery of drug in the plane of the centroneuraxis

7. ANATOMY Spinal column extends from foramen magnum to sacral hiatus
Vertebral column: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral and 4 coccygeal vertebrae
Spinal cord extends cephalad from the brainstem via the foramen magnum and extends distally in the conus medullaris, L3 in infants,L1 in adults.

9. Bony Landmarks

10. Anatomy of the Vertebra
Spinal canal contains spinal cord and coverings, pia, arachnoid and dura
Spinal cord extends from foramen magnum to L1 – L2
Subarachnoid space between arachnoid and pia mater, contains CSF
3 membranes that protect the spinal cord are 1. dura mater or tough mater, outermost and extends up to S2. 2. Arachnoid mater is the middle layeror cobweb mother, also ends at S2, 3. pia mater or soft mother, clings to the surface of the spinal cord and ends in the filum terminale, which helps to hold the spinal cord to the spinal column.

11. Absolute Contraindications to Spinal Anesthesia
Patient refusal
Sepsis at the site of injection
Hypovolemia
Coagulopathy
Indeterminate neurologic disease
Increased intracranial pressure

12. Spinal Anesthesia
Placement of LA solutions into the subarachnoid space, often lumbar
Landmarks: vertebral spinous processess iliac crests
Selected interspaces: L3, L4, L4-L5

13. Techniques Midline approach Lateral or paramedian approach
Taylor approach
Taylor Approach: the Taylor or lumbosacral approach is a paramedian approach directed at the L5-S1 interspace

14. Spinal Anesthesia Spinal tap: Midline Skin
Subcutaneous tissue Supraspinous ligament Interspinous ligament Ligamentum flavum Dura mater
Subdural Space
Arachnoid Mater
Subarachnoid Space
Landmark: Tuffier’s line – line between iliac crests passing through L4 – L5 interspace or L4 spinous process itself
Paramedian Approach: Skin Subcutaneous tissue, Ligamentum Flavum, Duramater, Subdural space, Arachnoid Mater, subarachnoid space

15. Level / Distribution Position during first few minutes
Baricity of LA solution:
density of LA
density of CSF
( )
Dose of the Anesthetic injected
Baricity: density of local anesthetic divided by the density of the local anesthetic at 37oC

16. LA solutions
HYPERBARIC – add glucose (dextrose) to increase density; settle to dependent region
HYPOBARIC – add sterile water; floats up to the nerves innervating surgical site
ISOBARIC – dilute with CSF; NaCL

17. Duration
Drugs used: Tetracaine/ bupivacaine> lidocaine> procaine
Vasoconstrictor – Epinephrine, Phenylephrine
Tissue vasoconstriction decreases SC blood flow and vascular absorption, prolonging the duration of the anesthetic
0.1 ml of Epinephrine in 10 ml LA =1:100,000 sol: .1 ml in 20ml = 1:200,000 solution, etc

18. Physiology
Spinal anesthesia interrupts sensory, motor and sympathetic nervous system
Classic concept: conduction blockade through small diameter, unmyelinated (sympathetic fibers) before interrupting conduction via larger myelinated (sensory and motor) fibers

19. Level and Distribution
Desired level is dependent on type of surgery
The SNS nerves are the first to be blocked, early evaluation is by temperature discrimination
Level of sensory anesthesia is evaluated by pinprick

20. Skeletal muscle power is tested by asking patient to dorsiflex foot (S1-S2), raise legs (L2-L3), or tense abdominal rectus muscles (T6-T12)

21. Physiologic Effects of Spinal Anesthesia
Cardiovascular Effects: L1 and B adrenergic blockers = decrease HR and BP
Pulmonary Effects: TV unchanged
Gastro-intestinal Effect: increased vagal activity results in inc peristalsis of GIT= nausea
High levels of motor anesthesia produces paralysis of abdominal and intercostal muscles, decreased ability to cough and expel secretions
Treatment of nausea: Atropine
Respiratory arrest 2o to hypoperfusion of respiratory centers in the brainstem

22. Physiologic Effects of Spinal Anesthesia
Renal Effects:Ureters are contracted, and ureterovesical orifice is relaxed: urinary retention
Block of afferent impulses from the surgical site leads to absence of adrenocortical response to pain
Decreased bleeding may reflect decreased BP
Increased blood flow to LE decreased thromboembolism

23. complications
Neurologic Injury – includes Cauda Equina syndrome, hematomas, abscess formation, arachnoiditis, meningitis

24. POSTSPINAL HEADACHE
Frontal/ occipital, worsened by sitting, improved by supine
Tinnitus, decreased hearing, diplopia
Due to decreased CSF pressures and resulting tension on meningeal vessels and nerves as a result of leakage of CSF thru dural hole
Diplopia is due to traction on abducens nn.
Prevalent in young females, large gauge spinal needle
Dr. august Bier first described this in 1898 after experimenting on himself. PDPH is due to loss of CSF

25. Treatment: Bed rest, analgesics
Hydration (> 3L/d) to inc CSF production
Epidural blood patch (10-20ml) to seal dura
Caffeine-sodium benzoate

26. HIGH SPINAL
excessive level of sensory and motor anesthesia associated with difficulty breathing or apnea, arterial hypoxemia or hypercarbia
Apnea reflects ischemic paralysis of medullary ventilatory centers due to profound hypotension and associated with decreased CBF

27. Treatment: support breathing and circulation
Positive pressure ventilation with face mask
IVF and sympathomimetics
Head-down to inc. venous return; head-up will jeopardize CBF medullary ischemia
Intubation of trachea in those at risk for aspiration (parturients)

28. Cardiovascular Collapse
Bradycardia precedes cardiac arrest
ACLS should be initiated early
Tx: atropine, Epinephrine, volume loading

29. Epidural Anesthesia
Similar to spinal anesthesia except local anesthetics reach blood level concentrations sufficient to cause systemic effects on their own

30. Unlike spinal, (-) zone of differential SNS block and zone of differential motor block may average 4 rather than 2 segments below sensory
Effects on breathing and GIT resemble those produced by spinal anesthesia

31. Complications 1. ACCIDENTAL DURAL PUNCTURE
Appearance of CSF (warm) at hub; at this point may opt to spinal, or attempt epidural at a different interspace
Post-spinal headache is likely due to large hole in dura

32. HIGH SPINAL
Accidental subarachnoid injection of large volumes of LA used produces rapid evidence of high spinal

33. 3.. LA TOXICITY
Due to high dose of local anesthetic used, rich venous plexuses, accidental intravascular injection may occur

34. Thank you…