Spinal anesthesia

SPINAL ANESTHESIA

Presented by:Hifza begum

Objectives of presentation

• Understanding of spinal anesthesia.• Physiological effects of spinal anesthesia.• Pharmacology of spinal anesthesia.• Treatment of different manifestations that

arise during spinal anesthesia.• Complications of spinal anesthesia.• Evaluation of spinal anesthesia.

Spinal AnesthesiaSpinal anesthesia follows the injection of local anesthetics into the cerebrospinal fluid (CSF) in the lumbar space

Spinal cord

Physiological effects of spinal anesthesia

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 blockOrder of sensitivity to local anestheticsSympathetic > temperature > pain > touch > motorSympathetic block is highest than the sensory block (pain, light touch) which in turn is higher than the motor blockade.


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 anesthesia.The effects of sympathetic blockade also involve the actions of parasympathetic nervous 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 • Compensatory vasoconstriction may occur.


• At high level of spinal anesthesia, the cardiac accelerator fibers which exit spinal cord at T1-T4 will be blocked

• Blood pooling • Reduce organ perfusion and cardiac output.• Unopposed vagal tone• Cardiac arrest

Treatment of CVS manifestation

• 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 (500-1000mL) of fluid prior to the administration of spinal anesthesia in an attempt to prevent some of the deleterious effect of spinal blockade.

Treatment of CVS manifestation

• Drugs with chronotropic and venoconstrictive properties are also given. e.g. ephedrine, 5-10mg intravenously, often is the drug of choice.

• Besides ephedrine, direct acting adrenergic receptor agonist such as phenylephrine can be administered either by bolus or continuous infusion.


• Sympathetic fibers originating from T5-L1 inhibit peristalsis. This together with a flaccid abdominal musculature produce excellent operating conditions for bowel surgery

• Pulmonary problems will be due to intercostal muscles paralysis and will reduce patient ability to cough and clear secretions and may produce dyspnea. It mostly occur due to medullary ischemia secondary to hypotension.

Pharmacology of Spinal Anesthesia

• Currently used drugs for spinal anesthesia in U.S. are

• Lidocaine: for short procedures.• Tetracaine: for intermediate to long

procedures.• Bupivacaine: for long procedures.• Procaine: for diagnostic blocks

Pharmacology of Spinal Anesthesia

• Factors contributing to distribution of local anesthetics in CSF are:

• Amount of drug injected.• Speed of injection. • Temperature of injectate.• Baricity of the drug injected.• Position of patient.• Addition of vasoconstrictor.

Complications of spinal anesthesia

• Certain neurological problems may occur• Possible causes include introduction of foreign

substance in subarachnoid space, infection, hematoma, mechanical trauma.

• Treatment usually is in effective.• High concentrations of local anesthetic can

cause irreversible block.• Lumbar puncture may cause postural

headache.

• Treatment involve bed rest and analgesics.• If this approach fails, an epidural blood patch

with the injection of autologous blood can be performed.

• Intravenous caffeine (500mg as benzoate salt administered over 4 hours) is also advocated.

Spinal anesthesia

Education

Transcript of Spinal anesthesia