Spinal Anaesthesia

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Spinal anaesthesia also called sub-arachnoid block (SAB)

Needles used :

• Whitacre
• Sprotte

These have pencil tip point end (therefore decrease post puncture headache)


Layers pierced :

1. Skin
2. Subcutaneus
3. Supraspinous ligament
4. Interspinous ligament
5. Ligamentum flavum (loss of ressistance felt as it is pierced)
6. Dura
7. Arachnoid - subarachnoid space

Drugs :

• Lignocaine (5%- heavy due to dextrose )
• Tetracaine (0.5% in 5% dextrose)
• Bupivacaine (0.5% in 8% dextrose)

Factors affecting height of anaesthesia :

• Dose (most important)
• Baricity of solution
• Volume of drug
• Position of patient
• Age
• Height
• Pregnancy
• Abdominal Tumors

Effects of Spinal Anaesthesia :

Blocks Sympathetic system at the concerned level (therefore Increases Parasympathetic)

Thus Hypotension with Tachycardia (Marey's law) (tachycardia because T1-T4 sympathetic is intact and so there is compensatory tachycardia)

But with High Spinal Block -- there is Hypotension with Bradycardia (as T1-T4 sympathetic also blocked)

Other points to remember :

• Autonomic block is 2 segments higher than sensory.

• Maximum breathing capacity and active exhalation decrease because of intercostal paralysis.

• Respiration is severely affected only if C3,4,5 involved (i.e very high spinal block)

• Nausea, Vomiting

• Vasodialator , therefore heat loss - shivering (T/t - Pethidine)

• Successful sign -- Flacid and engorged Penis (due to paralysis of  Nervi Ergentis )

• Most Common Complication : Hypotension 
Management for this : Prophylaxis - Preloading 1 - 1.5 L Coloid

                                 Curative : Foot end elevation

                                                Colloids , Vasopressor

                                 If Bradycardia - Atropine

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Post Spinal Headache : (Usually Occipital)

1. Low - pressure headache because of leak of CSF
    Therefore structures in brain are dragged down.

2. Presents :

• 24 - 48hrs
• Mostly > 90% in 7-10days
• Almost all by 3weeks

3. Prevention : Use pencil tip needle

4. Curative T/t :

• IV fluids
• Analgesics
• Inject 25 - 50 ml NS in epidural space
• BEST -- Inject 15 - 20 ml autologus blood in epidural space (blood patch)

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Other Complications (of Spinal Anaesthesia)

• Cauda equina syndrome
• Paraplegia
• 6th Nerve paralysis
• 1 , 9 , 10 nerve involvement
• Anterior spinal artery syndrome
• Meningitis
• Backache

Contraindications :

• Raised ICT
• Refusal of patient
• Infection at local site
• Bleeding diasthesis
• Hypotension , hypovolemia
• Spinal deformities
• Hypertension

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Saddle block anesthesia :

• A form of spinal anesthesia that produces loss of sensation in the buttocks, perineum, and inner thighs.
• If a patient is kept sitting for several minutes after the injection of a small volume of a hyperbaric solution of local anaesthetic, a classical "saddle block" affecting only the sacral nerve roots will result.

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