spinal anesthesia

1. SPINAL ANESTHESIA (A OVER VIEW)
Dr.A. Raj kumar

2. TOPICS
1.HISTORY OF NEURAXIAL
BLOCK
2.ANATOMY
3.PARTS OF SPINAL NEEDLE
4.MECHANISM OF ACTION
5.FACTORS INFLUENCING
SPINAL BLOCK
6.CONTRAINDICATIONS
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3. HISTORY OF NEURAXIAL BLOCK
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AUGUST BIER (1861-
1949)
James Leonard Corning (1855–1923)

4. Also in 1885, James Leonard Corning (1855–1923) injected cocaine between the spinous processes of the
lower lumbar vertebrae, first in a dog and then in a healthy man. His experiments are the first published
descriptions of the principle of neuraxial blockade.
On August 16, 1898, German surgeon August Bier (1861–1949) performed surgery under spinal anesthesia
in Kiel.Following the publication of Bier's experiments in 1899, a controversy developed about whether Bier
or Corning performed the first successful spinal anesthetic.
There is no doubt that Corning's experiments preceded those of Bier. For many years however, a controversy
centered around whether Corning's injection was a spinal or an epidural block. The dose of cocaine used by
Corning was eight times higher than that used by Bier and Tuffier. Despite this much higher dose, the onset
of analgesia in Corning's human subject was slower and the dermatomal level of ablation of sensation was
lower. Also, Corning did not describe seeing the flow of cerebrospinal fluid in his reports, whereas both Bier
and Tuffier did make these observations. Based on Corning's own description of his experiments, it is
apparent that his injections were made into the epidural space, and not the subarachnoid space. Finally,
Corning was incorrect in his theory on the mechanism of action of cocaine on the spinal nerves and spinal
cord. He proposed – mistakenly – that the cocaine was absorbed into the venous circulation and
subsequently transported to the spinal cord.
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7. ARTERIAL SUPPLY OF SPINAL CORD
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ventral
Radicular artery
(artery of Adamkiewicz)
,.._ _ Great

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9. PHYSIOLOGICAL EFFECTS OF SPINAL ANAESTHESIA
Relatively small dose and volume to achieve dense sensory blockade. Spinal nerve root contain varying
mixture of the fibers including somatic and autonomic fibers and they vary in their sensitivity to local
anesthetic blockade
 Differential block
 Order of sensitivity to local anesthetics (Sympathetic > temperature > pain > touch > motor
Most of physiological side effects of spinal anesthesia are a consequence of sympathetic blockade produce by local
anesthetic. Degree of sympathetic block is related to height of sensory anaesthesia.
The effects of sympathetic blockade also involve the actions of parasympathetic nervous system.
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10. CARDIO VASCULAR SYSTEM
• Clinically, most important effect of sympathetic block during spinal anesthesia are on the cardiovascular system.
 Vasodilation
 More marked on venous side of circulation
 Hypotension
At high level of spinal anesthesia, the cardiac accelerator fibers which exit spinal cord at T1-T4 will be
blocked
• venous pooling with profound hypotension
• Reduce organ perfusion and cardiac output.
• Unopposed vagal tone
Some times it can even lead to sudden cardiac arrest.
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11. TREATMENT OF CVS MANIFESTATIONS
• To maintain brain and cardiac perfusion, administration of oxygen, fluid infusion, manipulation of patient
position and administration of vasoactive drugs are all options.
• Patients are typically administered a bolus (10-20ml/kg) of fluid prior to the administration of spinal
anesthesia in a healthy patient to prevent some of the deleterious effect of spinal blockade.
Excessive bradycardia can be treated by atropine
Drugs used for hypotension are phenylephrine , ephedrine , mephentermine.
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12. Neuraxial block induce sympathectomy allows vagal dominance with a small contracted gut and active
peristalsis.
• Pulmonary problems will be due to intercostal muscles paralysis and will reduce patient ability to cough
and clear secretions and may produce dyspnea.
 Renal blood flow is maintained through autoregulation there is a little effects of spinal anesthesia on
kidney
 Neuraxial blockade in lumbar and sacral levels blocks both sympathetic and parasympathetic control of
bladder function. Loss of autonomic bladder control results in urinary retention until the block wears off.
 Neuaxial block can partial suppress during the major abdominal or thoracic surgery or totally block the
neuroendocrine stress response in lower extremity surgery.
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FIGURE 45–12 Sitting position for neuraxial
blockade. Note an assistant helps in obtaining
maximal spinal flexion.
FIGURE 45–13 The effect of flexion on adjacent vertebrae. A: Posterior view.
B: Lateral view.Note the target area (interlaminar foramen) for neuraxial blocks
increases in size with flexion.

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TABLE 45–2 Factors affecting the dermatomal spread of spinal
anesthesia.
Most important factors
Baricity of anesthetic solution
Position of the patient
During injection
Immediately after injection
Drug dosage
Site of injection
Other factors
Age
Cerebrospinal fluid
Curvature of the spine
Drug volume
Intraabdominal pressure
Needle direction
Patient height
Pregnancy

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Absolute
Infection at the site of injection Lack of consent
Coagulopathy or other bleeding diathesis Severe
hypovolemia
Increased intracranial pressure
Relative
Sepsis
Uncooperative patient Preexisting neurological deficits
Demyelinating lesions
Stenotic valvular heart lesions
Left ventricular outflow obstruction (hypertrophic
obstructive cardiomyopathy)
Severe spinal deformity
Controversial
Prior back surgery at the site of injection Complicated
surgery
Prolonged operation Major blood loss
Maneuvers that compromise respiration
CONTRAINDICATIONS

16. THANK YOU
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