- Paper Report
- Open Access
Comparison of five sedation scoring systems by means of auditory evoked potentials
- Richard Venn
© Current Science Ltd 1999
- Published: 7 May 1999
- Evoked potentials
- intensive care therapy
- monitoring of sedation
- sedation score
Auditory evoked responses (AEP) have been used as a means of monitoring awareness during anaesthesia. Attention has focused on the latency of the early cortical response Nb which indicates light anaesthesia and potential awareness when decreased to less than 44.5 ms. On the intensive care unit (ICU) sedation and analgesia is necessary to prevent ventilator dysynchrony and allow unpleasant procedures to take place. Sedation scoring systems are usually used to assess the level of sedation but unfortunately they are subjective and poor indicators of oversedation.
The authors have compared an objective measure (AER) with various subjective scoring systems.
The study investigated 95 consecutive patients requiring sedation for ventilation on the ICU. Midazolam and fentanyl were given for sedation and analgesia respectively, but additional agents could be used if sedation proved inadequate (propofol, methohexitone, gamma-hydroxybutyrate, ketamine or clonidine). The AER (midlatency Nbpeak) and corresponding level of sedation was recorded using five scoring systems [Ramsay, Cohen, Cambridge, Bloomsbury and Newcastle (Cook) Sedation Scores]. Kendall's correlation coefficients were calculated and regression analysis performed.
Coefficient of determination(r2)
However scatterplots showed a large variation of Nb latencies with deeper levels of sedation; ie these scoring systems are poor discriminators at deeper sedation levels.
Derived electrophysiological measurements and evoked potentials have all been used to measure depth of sedation/anaesthesia but require training and experience to develop competency. However, since clinical scoring systems are poor discriminators at deeper sedation levels, the authors suggest that AERs may have a role where deeper levels of sedation are required for prolonged periods. It is postulated that the Ramsay score showed the best correlation since it includes a primitive reflex (glabellar tap) to discriminate asleep states.