Spinal Anaesthesia

  • Spinal anesthesia is also called as spinal block or subarachnoid block (sab). 
  • SAB is a regional anesthesia involving injection of a local anesthesia into the subarachnoid space which extends from the foramen magnum to S2 in adults and S3 in children.
  • Injection of LA below LI in adults and L3 in children helps to avoid direct trauma to the spinal cord , (anesthetic agents acts on the spinal nerve and not on the substance of the cord)
  • Used both alone and in combination with either GA or sedation.
  • Lower limb orthopedic surgery on the pelvis, femur , tibia and ankle.
  • Total hip replacement.
  • Total knee replacement.
  • Lower limb vascular surgery.
  • Hernia (Ingunial or epigastric).
  • Haemorrhoidectomy , fistula , fissure.
  • Nephrectomy and cystectomy in combination with GA.
  • Transurethral resection of the prostate and transurethral resection of the bladder tumors.
  • Abdominal and vaginal hysterectomies
  • Laproscopic assisted vaginal hysterectomies(LAVH) combined with GA.
  • Caesarean sections.(LSCS)
Absolute Relative
Raised intracranial pressure
Patient refusal
Shock: Hypotension and hypovolemia
Infants and children- control of level is difficult.
Bleeding disorders
Patient's on anticoagu
lantsInfection of the local site and
Vertebral abnormalities (kyphosis, lordosis, etc.)
Aortic and mitral stenosis
Heart block
Spinal deformities
Psychiatric and CNS disorders

  1. Spinal canal should be on horizontal plane
  2. Operator should fix his or her gaze on the horizontal plane. 
  3. Flexed lateral position- back should be parallel to the edge of the table, knees are flexed on the abdomen, neck flexed.
  4. Jack knife position
  • Patient sit with their elbows resting on their thighs or bedside table or they can hug a pillow. 
  • Flexon of spine miximizes the target area between adjacent spinous processes and brings the spine closer to skin surface
  • This position is used for anorectal procedures utilising a hypobaric anasthetic solution
  • Taylor technique:
  1. Largest interspase L5-S1
  2. 12-cm needle directed upward , medially and forward at 500 , approximating forward at an angle that the dorsal aspect of the sacrum makes with the skin
  3. The needle enters the lumbosacral space between the sacrum and the last lumbar vertebra.
  4. Deposited between piamater & arachnoid 
  • The lateral position is preferred with the table tilted and the head up at 100degree to faster filling of the lumber subarachnoid space.
  • The sitting position may also be used.
  • First fibres to be blocked in spinal anaesthesia is Sympathetic preganglionic
  • The puncture at L3 –L4 vertibra interspace for children of 1-18yrs and L5 for infants.
  • The spinal needle directed perpendicular to plane of the back.
  • A standard 24-26G needle is used.
  • Dosage-Minimum vol. of 0.2ml is necessary in the preterm or newborn infant
  • 5% lignocaine is used for spinal anaesthesia.
  • Infant under 3000gm requires the largest doses because larger vol. of CSF and absorption doses upto 0.6mg/kg may be given to infant of 2-3kg of weight
  • For infant over 3kg the dose is stablised at 0.35 mg/kg upto 1yr of age.
  • T1-4 segments
  1. Bradycardia
  2. Hypotension(can be prevented by Preloading with crystalloids)
  3. Tingling or weakness in the hands or complaints of difficulty in breathing or talking.
  • C6-8: Hand paresthesia and weakness, likely to be effect on adequacy of breathing
  • C3-5: Diaphragmatic paralysis, with definite respiratory 
  • Post spinal headache 
  1. Usually begins after 48 hours and can last for 2 weeks.
  2. It can be minimised if CSF loss is minimised.
  3. Headache is usually dull in nature and is frontal to temporal in location.
  4. Occur due to CSF leak
Exam Question
  • In spinal anaesthesia drug is deposited between Piamater and arachnoid
  • First fibres to be blocked in spinal anaesthesia is Sympathetic preganglionic
  • Hypotension and Bradycardia is seen in patients given high spinal anaesthesia
  • A Lower Segment Caesarean section (LSCS) can be carried out under Spinal anaesthesia
  • The most effective method to prevent hypotension during spinal anaesthesia is Preloading with crystalloids
  • Headache after spinal anaesthesia is believed to be due to loss of CSF
  • Post spinal headache can last for 2 weeks
  • 5% lignocaine is used for spinal anaesthesia.
  • Increased intracranial pressure is the contraindications Spinal anaesthesia

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