S108. Effect of propofol on somatosensorial evoked potentials of long latency, N70

Introduction The aim of the study was to describe the morphological changes of long-latency somatosensory evoked potentials (SEPs) N70 after administration of intravenous propofol in neurologically healthy patients. This allows us to know if the use of this drug is capable of changing its morphology. The knowledge of this fact, will avoid a misinterpretation when using it as a prognostic marker in sedated patients with propofol with postanoxic neurological damage and traumatic brain injury. Methods Observational, descriptive, follow-up study of SEPs of long latency N70 before and after the administration of propofol in neurologically healthy patients in Hospital Espanol from May to October 2017. We used a Cadwell electromyograph equipment, Sierra Wave software version 11.0.116, with registration on C3′ and C4′, reference Fz (SI 10/20), filters 1 Hz and 10 Hz, gain 10 mV, sweep 20 ms, pulse width 100 ms and repetition rate of 1.41 Hz, stimulation on both median nerves. For sedation, we calculated the target plasma concentration of 4 mcg/ml and objectified by the bisespectral index or spectral entropy, anyone available in operating room. We included subjects aged 18–70, indistinct gender, admitted to a surgical procedure that does not involve the central or peripheral nervous system between May and October 2017 with previous complete neurological examination and general laboratories without alterations. We excluded everyone who refused to sign the informed consent.The data was analyzed in the statistical package STATA version 14.1 with Student “ t ” test was used for related samples. Results We performed SEPs N70 in 11 subjects. The results of this study showed a statistically significant difference in amplitude ( p p  = 0.144) for the latency of the right side. It could be the result of a value of 70.17 ms that we given as a default, because it was so difficult to measure it as the result of a very low amplitude. We decided to give that number instead of extend it up to 130 ms as normal limit. Although it seemed a deficiency of the study, if it had been considered as a dichotomous variable, then it would have been marked as absence of potential N70 being finally significant result. Conclusion Propofol is an agonist of GABA A receptors and blocker of the NMDA receptors reducing glutamatergic activity, that affect the signals of the ascending activating reticular system and the cortico-subcortical association relays, causing statistically significant morphological changes in the replicability of the SEPs of long latency N70 of healthy subjects, mainly in their amplitudes. If we do not considered measurable the replicability of the amplitude, ideally it should be marked as absence of potential.