Spinal Cord Monitoring — A Review of Current Techniques and Knowledge
The epidural recording of human SCP could provide extensive information on spinal cord function during anesthesia and surgery when several technical procedures are properly handled.
Three kinds of human SCPs can be recorded from the epidural space: the segmental and conductive SCPs, and the SCP produced by the descending volley. The segmental SCP consists of an initially positive spike (P1) followed by sharp negative (N1) and slow positive (P2) potentials, which are very similar in waveform to those in animals. The conductive or ascending SCP is composed usually of three spike-like potentials, sometimes followed by a negative slow wave. The SCP produced in the lumbosacral enlargement by the descending volley manifests itself as initial spikes followed by sharp negative-positive waves which are alike in waveform to the segmentally evoked SCP.
Anesthetics differentially affect each component of the segmental SCP. Hypoxia and acidosis suppress the SCP studied in the rat. The suppression is most pronounced in the P2 wave and “the heterosegmental potential.” The N1 amplitude is also decreased by hypoxia, with prolongation of its duration.
The simultaneous recording of other electrical activities along the sensory pathways, such as the SEP from the scalp, may provide a more accurate evaluation of spinal cord function during surgery.
KeywordsEpidural Space Spinal Cord Stimulation Posterior Tibial Nerve Stimulation Primary Afferent Depolarization Spinal Cord Function
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