Spinal Cord Monitoring Dr. M. Fennelly Consultant Anaesthetist The Royal National Orthopaedic...
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Transcript of Spinal Cord Monitoring Dr. M. Fennelly Consultant Anaesthetist The Royal National Orthopaedic...
Spinal Cord Monitoring
Dr. M. FennellyConsultant AnaesthetistThe Royal National Orthopaedic Hospital
Why do I wantto know about
this?!!
How?
Stagnara ‘Wake up test’Ankle clonus testNeurophysiological
-Evoked potentials
Intra-operative physiological monitoring
Spinal cord (Scoliosis)Sciatic/ Femoral nerve (THR)Brachial plexusPedicle screwsVascular surgeryParotid surgery
Concept of monitoring
…….Indirect mechanical
Mechanisms of Injury ……
L4L4
L5L5
Mechanisms of Injury ……
Direct mechanical
aorta Segmental a.
Radicular a.Anteriorspinal a.
Mechanisms of injury
Ischaemic cord injuryCompression
+Distraction
+Oedema
+Hypotension
=Reduced cord perfusion
Epidural spinal somatosensory evoked potential Cortical somatosensory evoked potentialsC2 somatosensory potentials
( To posterior tibial nerve, peroneal nerve stimulation)
Somatosensory Evoked Potentials
Preoperative electrode placement
Out of surgical fieldAnterior approach surgerySpinally injuredSpondylolisthesisBrachial plexus exploration
Anaesthetic considerations for SSEP
Relatively forgivingRelaxation unimportant
Effects of local anaesthetics and opiateson S.S.E.P.
Loughnan, Fennelly et al. Anaesthesia and analgesia 1995
S.S.E.P. or M.E.P. ?
Motorend-plate
M.E.P.
WHY ?
Dissociation of SEP and MEPEarlier prediction of damageSpecific pathway monitoring
M.E.P. Problems
•Anaesthetic•Stimulus patterns
Anaesthesia
Nitrous oxideIsoflurane
Muscle relaxation
Propofol infusionFentanylAlfentanilRemifentanil
Factors affecting E.P.s
HypoxiaHypotensionCarbon dioxideTemperatureNerve integrityAnaesthetic agentsSide
Interpretation
What is a significant change?LatencyAmplitude 50%Other parameters
N.B. Must monitor minimum 20 minutes after final correction
Action
Exclude technical failureExclude anaesthetic changeRelease correction / distraction(Decompress)
How long have you got ?
Aortic cross clamp 30 minutes
Why is the S.M.E.P. more sensitive toanaesthetic agents
Than the S.S.E.P. ?
Synapses in pathway
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