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Spinal Cord Monitoring

Spinal Cord Monitoring. Dr. M. Fennelly Consultant Anaesthetist The Royal National Orthopaedic Hospital. Why do I want to know about this?!!. How?. Stagnara ‘Wake up test’ Ankle clonus test Neurophysiological -Evoked potentials. Intra-operative physiological monitoring.

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Spinal Cord Monitoring

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  1. Spinal Cord Monitoring Dr. M. Fennelly Consultant Anaesthetist The Royal National Orthopaedic Hospital

  2. Why do I want to know about this?!!

  3. How? Stagnara ‘Wake up test’ Ankle clonus test Neurophysiological -Evoked potentials

  4. Intra-operative physiological monitoring Spinal cord (Scoliosis) Sciatic/ Femoral nerve (THR) Brachial plexus Pedicle screws Vascular surgery Parotid surgery

  5. Concept of monitoring

  6. Mechanisms of Injury …… …….Indirect mechanical

  7. L4 L5 Mechanisms of Injury …… Direct mechanical

  8. Segmental a. Anterior spinal a. Radicular a. aorta

  9. Mechanisms of injury Ischaemic cord injury Compression + Distraction + Oedema + Hypotension = Reduced cord perfusion

  10. Somatosensory Evoked Potentials Epidural spinal somatosensory evoked potential Cortical somatosensory evoked potentials C2 somatosensory potentials ( To posterior tibial nerve, peroneal nerve stimulation)

  11. Preoperative electrode placement Out of surgical field Anterior approach surgery Spinally injured Spondylolisthesis Brachial plexus exploration

  12. Anaesthetic considerations for SSEP Relatively forgiving Relaxation unimportant

  13. Effects of local anaesthetics and opiates on S.S.E.P. Loughnan, Fennelly et al. Anaesthesia and analgesia 1995

  14. S.S.E.P. or M.E.P. ?

  15. Motor end-plate M.E.P.

  16. WHY ? Dissociation of SEP and MEP Earlier prediction of damage Specific pathway monitoring

  17. M.E.P. Problems • Anaesthetic • Stimulus patterns

  18. Anaesthesia Nitrous oxide Isoflurane Muscle relaxation Propofol infusion Fentanyl Alfentanil Remifentanil

  19. Factors affecting E.P.s Hypoxia Hypotension Carbon dioxide Temperature Nerve integrity Anaesthetic agents Side

  20. Interpretation What is a significant change? Latency Amplitude  50% Other parameters N.B. Must monitor minimum 20 minutes after final correction

  21. Action Exclude technical failure Exclude anaesthetic change Release correction / distraction (Decompress)

  22. How long have you got ? Aortic cross clamp 30 minutes

  23. Why is the S.M.E.P. more sensitive to anaesthetic agents Than the S.S.E.P. ?  Synapses in pathway 

  24. History at RNOH... Sensory nerve conduction in the human spinal cord: epidural recordings made during scoliosis surgery. Jones SJ. Edgar MA. Ransford AO. Journal of Neurology, Neurosurgery & Psychiatry. 45(5):446-51, 1982 May. Spinal cord monitoring in scoliosis surgery. Experience with 1168 cases. Forbes HJ.Allen PW. Waller CS.Jones SJ.Edgar MA.Webb PJ.Ransford AO. Journal of Bone & Joint Surgery - British Volume. 73(3):487-91, 1991 May. Temporal summation--the key to motor evoked potential spinal cord monitoring in humans. Taylor BA. Fennelly ME. Taylor A. Farrell J. Journal of Neurology, Neurosurgery & Psychiatry. 56(1):104-6, 1993

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