Is Anesthetic Loss of Consciousness a Top Down or Bottom up Phenomenon. What Does the Neurologic Examination Say?.

Anesthesia; Functional

propofol, pharmacology, anesthesic induction, drug titration

Using very slow or fast propofol intravenous injection, monitored using standard American Society of Anesthesiology (ASA) standard and SEDLine EEG (Med Tech), the patient was evaluate by a neurologist every 30 sec using the FOUR coma scale.

Clinical experimental randomized study, approved by the Ethic Committee, with informed consent, included ASA I- II adults, without neurological illness and normal physical exam. The patient randomized in two groups, rapid induction (GR) with propofol in target controlled infusion (TCI) effect site mode using the phamacokinetic (PK) model from Marsh ke0 1,21 min-1 using a calculated target of 5.4 ug/ml (loss of counsciousness EC95) and slow induction (GL) 10 mg/kg/h with calculated effect site concentrations (CeCALC) same PK model. The same neurologist, blind to the correspondent group, evaluated all the patients every 30 sec using the coma FOUR scale until loss of counsciousness (LOC), defined as a FOUR (E0 no eyes opening response and /or M0 no motor response). At LOC the existance of brainstem reflex was evaluated (B no pupil and corneal reflex), respiratory pattern (R apnoea), CeCALC and patient state index (PSI) SEDline™ was recorded during all the examination. After LOC in both groups we maintain in GR the initial target (5.3 ug/ml) and the LOC CeCALC during 10 min without intervention, except respiratory support if it was required. Frontal EEG 4 channel and spectrogram from SEDline monitor was extracted for each case and posterior analysis. Fisher exact test was used to describe primary outcome and difference between B and R for each group. The difference in time to reach LOC LOC, Ce and PSI was analysed with T- Student.

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