Awareness and Dreaming during Anaesthesia : Incidence and Importance

• Main Author: Samuelsson, Peter
• Format: Doctoral Thesis
• Language: English
• Published: Linköpings universitet, Institutionen för medicin och hälsa 2008
• Subjects: Anesthesiology and Intensive Care; Anestesi och intensivvård
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-15408; http://nbn-resolving.de/urn:isbn:9789173937863

The definition of awareness used consistently in this thesis is: Explicit recall of intraoperative events during general anaesthesia. Since there is no objective method to detect awareness, the patients must be interviewed after anaesthesia. The form and timing of the interview is crucial. To rely on spontaneous disclosure of awareness episodes is not sufficient. The total number of awareness-victims is considerable although the incidence may seem modest. A number of these patients look upon the awareness experience as the worst experience in their life. Suffering can include pain, mental distress and delayed psychological symptoms. However, the experience of awareness is not uniform and not all patients suffer. A comprehensible definition for dreaming during anaesthesia is: Any recalled experience, excluding awareness, which occurred between induction of anaesthesia and the first moment of consciousness upon emergence. Some findings point in the direction that dreaming during anaesthesia may be related to light or insufficient anaesthesia, but other findings do not. Some patients find dreaming during anaesthesia distressing, but generally the overall impression is that consequences of dreaming during anaesthesia seem to be small and of minor importance to the majority of patients. In this thesis I have found the following:The incidence of awareness is approximately 0.2% when neuromuscular blocking drugs are used and awareness also exists without these drugs, albeit to a lesser extent. These findings represent standard practice in an adult population at normal risk. 50% of awareness cases may have delayed recall of awareness. Using a consecutive inclusion design we found initial awareness suffering comparable to previous studies, but a lower incidence and less pronounced severity of late psychological symptoms. The incidences found among the awareness-victims in our study were; experience of pain 46%, immediate mental distress 65%, any late psychological symptom 33%, and PTSD below 10%. A memory of an intraoperative dream after general anaesthesia is not an early interpretation of delayed awareness, indicating that no routine follow up of dreaming-only patients is indicated. Dreams reported after anesthesia are generally not related to insufficient anesthesia defined as high BIS, and should not be regarded as near awareness.