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Complications of Spinal Anaesthesia

Based on Miller's Anesthesia (10th Ed.) and Morgan & Mikhail's Clinical Anesthesiology (7th Ed.)

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SPINAL NEEDLES - Types, Design, and Selection

Needle Tip Designs

• Quincke-Babcock needle: The classic cutting needle with a bevelled, sharp tip and end injection orifice. Cuts through dural fibres rather than separating them, producing a larger dural defect and a significantly higher incidence of post-dural puncture headache (PDPH).
• Pitkin needle: Another cutting tip design, now largely historical.

• Whitacre: Rounded, conical (pencil-point) tip with side injection. Separates rather than cuts dural fibres, dramatically reducing PDPH risk.
• Sprotte: Pencil-point tip with a long, oval side-injection opening. Gives vigorous CSF flow due to the large aperture - but this creates a specific risk: if only the distal part of the opening is subarachnoid (with free CSF flow) while the proximal part of the opening remains outside the dura, the full drug dose will not be delivered intrathecally, resulting in a failed block.
• Pencan: Another atraumatic pencil-point design.

Needle Gauge and PDPH Relationship

NR-Fit (Non-Luer) Connectors

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TECHNIQUE OF SPINAL ANAESTHESIA

Pre-procedure Preparation (Miller's Ch. 41)

• Obtain informed consent with documentation of risks discussed.
• Ensure resuscitation equipment is immediately available at all times.
• Minimum monitoring: pulse oximetry, NIBP, ECG.
• Establish adequate IV access.
• Preprepared packs typically contain drapes, swabs, syringes, needles, filters, spinal needles, sterilising solution, and local anaesthetic for skin infiltration.
• Match local anaesthetic duration to the surgical procedure (see drug selection below).

Sterility

• Mask, hand/forearm wash, glove.
• Most common organism in post-spinal bacterial meningitis is Streptococcus viridans (an oral commensal), emphasising the purpose of wearing a mask.
• Skin cleaning: chlorhexidine + alcohol is the most effective combination. Chlorhexidine must be allowed to dry completely before needle insertion - chlorhexidine is neurotoxic if introduced intrathecally while still wet (Miller's, p. 6067).

Patient Positioning

• Patient's back parallel to the table edge nearest the anaesthesiologist.
• Thighs flexed onto abdomen, neck flexed to bring forehead toward knees ("foetal position") to open vertebral spaces.
• More comfortable; allows sedation; less reliant on an assistant.
• In females, hips wider than shoulders cause the spine to slope downward toward the head (relevant when using hyperbaric solutions).
• In males, the opposite occurs.

• Easier midline identification, especially in obese or scoliotic patients.
• Stool footrest + pillow in lap; assistant helps maintain vertical posture and flexion.
• Hypotension may be more common.
• Do not over-sedate.

• Used when surgery is to be performed in prone position (rectal, perineal, lumbar procedures).
• Gravity opposes CSF flow; active aspiration may be needed to confirm dural puncture.

Landmark Identification

• Intercristal (Tuffier's) line between the two iliac crests traditionally corresponds to L4 vertebral body or L4-L5 interspace.
• Ultrasound studies show this landmark is unreliable; ultrasound can be used to verify the interspace.
• Spinal cord ends at L1-L2; insertion above this level should be avoided.
• Target interspaces: L3-L4 or L4-L5 (midline approach).

Midline Approach

1. Skin wheal of LA over the selected interspace.
2. Insert introducer at a 10-15 degree cephalad angle through skin, subcutaneous tissue, and supraspinous ligament.
3. Advance spinal needle through the introducer - two "pops" are felt:
   • First pop: penetration of ligamentum flavum.
   • Second pop: penetration of the dura-arachnoid membrane.
4. Remove stylet - verify free flow of CSF.
   • With needles <25-G, active aspiration may be needed.
   • If CSF flows initially but cannot be re-aspirated after syringe attachment, the needle has moved.
5. Persistent paresthesia or pain during injection: withdraw and redirect the needle before proceeding.
6. Inject drug in a controlled manner; note bevel direction with cutting needles (bevel parallel to longitudinal dural fibres reduces the defect size and lowers PDPH).

Paramedian Approach

• Useful when midline approach is difficult (mid-to-high thoracic, heavily calcified interspinous ligaments, kyphosis).
• Needle inserted 1-2 cm lateral to the inferior tip of the spinous process of the vertebra above the desired interspace.
• Advanced horizontally to hit lamina, then redirected medially and cephalad.
• Taylor approach: Modified paramedian via the L5-S1 interspace. Needle placed 1 cm medial and 1 cm inferior to the posterior superior iliac spine, angled medially and cephalad at 45-55 degrees. Useful in trauma patients who cannot sit.

Factors Affecting Block Level (Morgan & Mikhail Table 45-2)

1. Baricity of LA solution and patient position during/after injection.
2. Drug dose (volume x concentration).
3. Site of injection (more cephalad injection = more cephalad spread).

• Hyperbaric solution (heavier than CSF): settles to the dependent side.
• Hypobaric solution (lighter than CSF): rises toward the non-dependent side.
• Isobaric solution: relatively position-independent spread.

Block Monitoring (Miller's Ch. 41)

• Assess onset, extent, and quality of sensory and motor block.
• Sensory assessment: cold (C-fibers assessed first, most cephalad spread), then pinprick (Aδ-fibers), then touch (Aβ-fibers).
• Motor block: Modified Bromage Scale:
  • 0: No block
  • 1: Cannot raise extended leg; can move knees and feet
  • 2: Cannot raise extended leg or move knee; can move feet
  • 3: Complete lower limb motor block
• Block is considered adequate when cold/pinprick level is 2-3 segments above the expected surgical stimulus level.

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COMPLICATIONS OF SPINAL ANAESTHESIA

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1. HYPOTENSION

• Aortocaval compression (supine position, especially in pregnancy)
• Upright or semi-upright position
• Hypovolaemia (exaggerated response)
• Pre-existing aortic stenosis or fixed cardiac output states

• IV phenylephrine boluses (40-120 mcg) - first-line vasopressor
• IV fluid bolus (though routine crystalloid pre-loading before epidural does not reliably prevent hypotension)
• Supplemental oxygen
• Left uterine displacement in pregnant patients
• Trendelenburg position is controversial (may impair pulmonary gas exchange)
• Ephedrine (if bradycardia component is present)

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2. HIGH SPINAL / TOTAL SPINAL ANESTHESIA

• High thoracic/cervical spread: severe hypotension, bradycardia, respiratory insufficiency.
• Total spinal (extends to cranial nerves): unconsciousness, apnoea, profound hypotension.
• Apnoea is more commonly due to medullary hypoperfusion from sustained hypotension than to phrenic nerve palsy (C3-C5) per se.
• Anterior spinal artery syndrome can result from prolonged severe hypotension combined with raised intraspinal pressure.

• Nausea often precedes hypotension.
• Dyspnoea, numbness/weakness in upper extremities.

• Reassure patient.
• Supplemental oxygen; assisted ventilation; intubation + mechanical ventilation if needed.
• IV vasopressors (ephedrine, epinephrine) and rapid IV fluids.
• Atropine early for bradycardia.
• Epinephrine for cardiac arrest.

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3. CARDIAC ARREST DURING SPINAL ANAESTHESIA

• Relatively high incidence: approximately 1:1500 spinal anaesthetics.
• Many preceded by bradycardia; many occur in young, healthy patients.
• Contributing factors: oversedation, unrecognised hypoventilation, hypoxia (historical cases predated pulse oximetry), untreated hypovolaemia.
• Prevention: Prompt treatment of bradycardia and hypotension is strongly recommended.

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4. BRADYCARDIA

• From sympathetic blockade (block of cardioaccelerator fibres T1-T4 when block is high).
• Also from the Bezold-Jarisch reflex: venous pooling reduces venous return, activating intracardiac stretch receptors, producing paradoxical bradycardia.
• Treatment: atropine, ephedrine, epinephrine if severe.

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5. POST-DURAL PUNCTURE HEADACHE (PDPH)

• Bilateral, frontal, retroorbital or occipital, extending into the neck.
• Throbbing or constant; associated with photophobia and nausea.
• Hallmark: postural - aggravated by sitting/standing, relieved by lying flat.
• Onset typically 12-72 hours after dural puncture (may be delayed up to 7 days).
• May be accompanied by diplopia (CN VI palsy), tinnitus, and hearing changes.

• Large-gauge needle.
• Cutting (Quincke) tip vs. pencil-point tip.
• Female sex, younger age, obstetric patients.
• Prior history of PDPH.

• Use pencil-point needles ≥22-G (ideally 25-26-G).
• If using a cutting needle, bevel parallel to longitudinal dural fibres.
• Replacing the stylet before withdrawing the needle reduces PDPH rate.

• Conservative: bed rest, hydration, caffeine (promotes vasoconstriction), simple analgesics.
• Epidural blood patch (EBP): gold-standard treatment. Autologous blood (15-20 mL) injected into the epidural space at the level of the dural puncture. Creates a clot that seals the defect. Relief in >90% of cases. A second patch can be performed if the first is inadequate.

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6. URINARY RETENTION

• Local anaesthetic block of S2-S4 root fibres decreases bladder tone and inhibits the voiding reflex.
• Intrathecal/epidural opioids also impair voiding.
• Management: bladder catheterisation if persistent.

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7. BACKACHE

• Needle passage through skin, subcutaneous tissue, muscle, and ligaments causes varying degrees of tissue trauma, bruising, and localised inflammation.
• Usually mild and self-limited (days to weeks).
• Important: up to 25-30% of patients receiving general anaesthesia also report postoperative backache, and a large proportion of the population has pre-existing chronic back pain.
• Treatment: paracetamol or NSAIDs.
• Clinical significance: Backache may be the first sign of a serious complication (epidural haematoma or abscess). Must not be dismissed without assessment.

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8. TRANSIENT NEUROLOGICAL SYMPTOMS (TNS) / Transient Radicular Irritation (TRI)

• Tetracaine (2%)
• Bupivacaine (1%)
• Mepivacaine, prilocaine, procaine, ropivacaine

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9. CAUDA EQUINA SYNDROME

• Permanent lower motor neuron damage: saddle anaesthesia, bowel/bladder dysfunction, variable lower limb weakness.
• Most commonly associated with continuous spinal anaesthesia via microcatheters using hyperbaric 5% lidocaine - the drug pools around the cauda equina at high concentration.
• Also associated with direct trauma from needle, haematoma, or abscess.
• The 5% hyperbaric lidocaine preparation has largely been abandoned due to this risk.

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10. SPINAL / EPIDURAL HAEMATOMA

• Anticoagulant or antiplatelet therapy (see ASRA guidelines).
• Coagulopathy, thrombocytopenia.
• Traumatic needle insertion, multiple attempts.
• Underlying spinal vascular lesions.

• Urgent MRI or CT imaging.
• Neurosurgical decompression within 6-8 hours of onset of neurological deficit is the key determinant of neurological recovery.
• ASRA (American Society of Regional Anesthesia) guidelines define minimum intervals between anticoagulant administration and neuraxial procedures (see ASRA 4th edition guidelines, Horlocker et al. 2018).

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11. MENINGITIS

• Bacterial or chemical (aseptic).
• Bacterial meningitis: Most common organism - Streptococcus viridans (oral commensal) - transmitted from the operator's droplets. Full aseptic technique including mask is essential.
• Chemical/aseptic meningitis: May result from detergents, antiseptics, or preservatives introduced into the intrathecal space.
• Presentation: fever, headache, neck stiffness, photophobia. CSF analysis confirms diagnosis.
• Treatment: antibiotics, supportive care.

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12. EPIDURAL ABSCESS

1. Back pain intensified by spinal percussion.
2. Nerve root / radicular pain.
3. Motor/sensory deficits or sphincter dysfunction.
4. Paraplegia / paralysis.

• Remove catheter (if present) and culture the tip.
• Blood cultures.
• Anti-staphylococcal antibiotics.
• Urgent MRI/CT to confirm.
• Surgical decompression (laminectomy) or percutaneous drainage.
• Prognosis correlates with degree of neurological deficit at time of diagnosis.

• Minimise catheter manipulations; maintain closed system.
• Use 0.22-μm bacterial filter.
• Replace/remove epidural catheter after defined time interval (some practitioners remove after 4 days).

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13. ARACHNOIDITIS

• Inflammation of the arachnoid membrane, resulting in fibrosis and adhesion formation.
• Can be caused by intrathecal injection of: chlorhexidine (if not fully dried), blood, detergents, preservatives, or contaminated solutions.
• Presents as chronic, progressive pain and neurological dysfunction.
• Largely preventable by meticulous technique and using only preservative-free solutions intrathecally.

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14. NEURAL INJURY

• Needle insertion above L1-L2 risks direct spinal cord trauma.
• More common with thoracic spinal procedures.

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15. SUBDURAL INJECTION

• Inadvertent injection into the potential space between dura and arachnoid.
• With spinal doses: relatively less serious.
• With epidural doses: produces presentation similar to high spinal - but onset may be delayed 15-30 minutes and block may be "patchy."
• Spinal subdural space extends intracranially, so LA can ascend to very high levels.
• Treatment: supportive - intubation, mechanical ventilation, cardiovascular support.

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16. FAILED OR INADEQUATE SPINAL BLOCK

• Needle movement during injection.
• Incomplete entry of needle opening into subarachnoid space.
• Subdural injection.
• Injection into a nerve root sleeve.
• With Sprotte needle: CSF flows freely from distal end of the side aperture which is subarachnoid, while the proximal portion of the aperture has not cleared the dura - drug delivered partly extradurally.
• Insufficient drug dose.

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17. HORNER'S SYNDROME

• From ipsilateral sympathetic blockade at T1-T3 level (ptosis, miosis, anhidrosis, enophthalmos).
• Seen with high thoracic spinal or cervical extension.
• Usually transient and resolves with block regression.

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18. NAUSEA AND VOMITING

• Very common, often preceding hypotension.
• Caused by hypotension reducing cerebral perfusion, or vagal dominance from unopposed parasympathetics after sympathetic block.
• Treatment of the underlying hypotension usually resolves nausea.
• Ondansetron or metoclopramide can be used.

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19. RESPIRATORY COMPROMISE

• Results from blockade of intercostal muscles (T1-T12) and potentially phrenic nerve (C3-C5) with very high blocks.
• Most cases of apnoea during high spinal are from medullary ischaemia (due to hypotension) rather than phrenic nerve block alone.
• Management: oxygen supplementation, assisted ventilation, intubation if needed.

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20. WRONG ROUTE ADMINISTRATION

• Risk of epidural drug dosages being given intrathecally (10x overdose).
• Risk of wrong drug entirely entering the intrathecal space.
• Prevention: NR-Fit (non-Luer) connectors, careful drug labelling, independent double checks.

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INCIDENCE DATA (Morgan & Mikhail Table 45-7)

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SPECIAL POPULATIONS (Miller's Ch. 41)

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SUMMARY TABLE OF COMPLICATIONS

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• Miller's Anesthesia, 2-Volume Set, 10th Edition - Chapter 41 (Spinal, Epidural, and Caudal Anesthesia)
• Morgan and Mikhail's Clinical Anesthesiology, 7th Edition - Chapter 45 (Neuraxial Anesthesia)

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