What should I know?

Basic Anatomy

  • In the adult, the spinal cord ends at the level of L1-2
  • Spinal anaesthesia/lumbar puncture aims to insert the spinal needle into the subarachnoid space
  • Spinal needles will have to go through several layers
    • skin—subcutaneous tissue—supraspinous ligament—interspinous ligament—ligamentum flavum – epidural space—dura mater—subarachnoid space
  • Spinal anaesthesia for caesarean sections should at least cover the T4-T5 dermatome because visceral pain from the peritoneum could arise from the T5 dermatome

Absolute Contraindications

  • Patient refusal

Relative Contraindication

  • Bleeding diathesis
  • Active infection
  • Previous spinal surgery
  • Increased ICP due to intracranial mass

Possible adverse effects

  • Hypotension (90%)(2)
  • Infection (1:2500)
  • Spinal hematoma (1:220000)(3)
  • Post-dural puncture headache (incidence is 0-14% with non-cutting needles)(4)
  • Inefficient spinal (1%)(5)


Spinal Needles

  • Non-cutting needles(Whitacre, Sprotte, PenCan) are preferred, lower rate of Post Dural Puncture Headache(6)
  • Smaller needles(23-25G) lower rate of Post Dural Puncture Headache
  • Small diameter needles (29G) may decrease the spinal success rate
  • Sterile Gloves
  • Chlorhexidine 0.5%
  • Sterile drape
  • Sterile gown
  • Hat


  • Local anaesthetic for skin: lignocaine 1%
  • Spinal drugs: Heavy bupivacaine 0.5% ± fentanyl mcg ± intrathecal morphine (intrathecal morphine provides long post-op pain relief of 18-24 hours, while fentanyl is utilized to improve overall block quality)(7)
  • Phenylephrine (100 mcg/ml) or metaraminol (0.5 mg/ml) to counter potential hypotension from spinal anaesthesia


Sitting or lateral:

  • Identifying needle insertion site, Tuffier’s line: line that connects the highest point of the iliac crest, corresponds to either L3-4 or L4-5
  • Sitting is more common in Australia

Lateral position allows one to measure CSF pressure

Position patient:

  • Either sitting or lateral
  • Maximum flex of spine (5)


  • Clean back with chlorhexidine 0.5% + ETOH solution
  • Ensure chlorhexidine is completely dry on the skin before instrumenting the back (potential neurotoxicity)
  • Draw up local anaesthetic in either a 5 ml syringe or a 3 ml syringe
  • Draw up spinal drugs in either a 3 ml or 5 ml syringe preferably using a filter needle

Heavy bupivacaine 0.5% 1.8-2.2 ml + fentanyl 15 mcg ± intrathecal morphine 100 mcg

Spinal Insertion

  • Insert the introducer needle up to its hub midline L3-4 or L4-5 space

  • Insert the spinal needle until a pop is felt
  • Once the appropriate depth is reached, withdraw the stylet, and wait until CSF flow out

  • Inject spinal drug, but always aspirate first, ensuring good CSF flow
  • Start vasopressor if expecting hypotension


  • Slowly lie the patient down
  • A slight left lateral position must be maintained before the baby’s delivery
  • Desirable block height is to T4 dermatome to ice or T5 to light touch
  • The block usually reaches maximum effect between 5 to 10 minutes


1. Malinowski AK, Othman M. Obstetric neuraxial anaesthesia in the setting of immune thrombocytopenia and low platelet counts: call to participate in an international registry. British Journal of Anaesthesia. 2021;127(1):e12-e3. Available from: https://doi.org/10.1016/j.bja.2021.03.024. DOI: 10.1016/j.bja.2021.03.024.

2. Gibbs CP, Krischer J, Peckham BM, Sharp H, Kirschbaum TH. OBSTETRIC ANESTHESIA: A NATIONAL SURVEY. Obstetric Anesthesia Digest. 1987;7(1). Available from: https://journals.lww.com/obstetricanesthesia/Fulltext/1987/04000/OBSTETRIC_ANESTHESIA__A_NATIONAL_SURVEY.1.aspx.

3. Vela Vásquez RS, Peláez Romero R. Aspirin and spinal haematoma after neuraxial anaesthesia: Myth or reality? British Journal of Anaesthesia. 2015;115(5):688-98. Available from: https://doi.org/10.1093/bja/aev348. DOI: 10.1093/bja/aev348.

4. Turnbull DK, Shepherd DB. Post-dural puncture headache: pathogenesis, prevention and treatment. British Journal of Anaesthesia. 2003;91(5):718-29. Available from: https://doi.org/10.1093/bja/aeg231. DOI: 10.1093/bja/aeg231.

5. Fettes PD, Jansson JR, Wildsmith JA. Failed spinal anaesthesia: mechanisms, management, and prevention. Br J Anaesth. 2009;102(6):739-48. DOI: 10.1093/bja/aep096.

6. Halpern S, Preston R. Postdural puncture headache and spinal needle design. Metaanalyses. Anesthesiology. 1994;81(6):1376-83. DOI: 10.1097/00000542-199412000-00012.

7. Kestin IG. SPINAL ANAESTHESIA IN OBSTETRICS. British Journal of Anaesthesia. 1991;66(5):596-607. Available from: https://doi.org/10.1093/bja/66.5.596. DOI: 10.1093/bja/66.5.596.

8. Hocking G, Wildsmith JAW. Intrathecal drug spread. BJA: British Journal of Anaesthesia. 2004;93(4):568-78. Available from: https://doi.org/10.1093/bja/aeh204. DOI: 10.1093/bja/aeh204 %J BJA: British Journal of Anaesthesia.

9. Nor NM, Russell IF. Assessing blocks after spinal anaesthesia for elective caesarean section: how different questions affect findings from the same stimulus. International journal of obstetric anesthesia. 2013;22(4):294-7. DOI: 10.1016/j.ijoa.2013.05.010.