Comparison of Amnesia Produced with Commonly Used Sedative Drugs - A Randomized Study

Abstract

Aims and Objectives: Evaluate the sedative and amnestic drugs in conscious sedation and determine the duration and extent of amnesia, to investigate duration and extend of retrograde amnesia and anterograde amnesia, and, to determine strategies to reduce intra-operative awareness.
Methods: The patients were randomly allocated to receive either Propofol, Midazolam or Ketamine via a continuous infusion in order to achieve a level of sedation (score 4: Ramsay Sedation Scale). Five minutes after the initiation of the sedative infusion, a subarachnoid block was instituted, in order to achieve an adequate block for the proposed surgery.5 minutes prior to receiving the sedative infusion, each patient was shown a picture of a commonly occurring object to assess the possibility of retrograde amnesia. Two more pictures were shown after they reached a sedation score of 4. At the end of the sedative infusion, a fourth picture was shown to the patient.30 minutes after commencing the sedative infusion, a sequence of 5 commonly used words were formed into a sentence and told to the patient, close to her/his ear, by a single observer.
Results: The hemodynamic parameters were more stable in the Ketamine group as compared to the Midazolam or Propofol groups (P=0.00). Ketamine group had the maximum number of patients who could not recognize the anesthetist (P=0.003) or the 1st picture (P=0.005), which was suggestive of retrograde amnesia. As the depth of sedation increased significant amnesia was present for Midazolam group and Propofol group.The hinted recall was maximum in Ketamine group and least in Midazolam group ( P=0.00) for both visual and auditory information