Implicit Memory and Psychological Disturbance in Intensive Care Unit Patients

Part One: Literature Review - Background: People who experience an intensive care unit admission may also experience post-traumatic stress and other forms of psychological distress. Such phenomena are only partly explained by the reason for admission. This distress can impede physical recovery and full participation in everyday life. Method: Using specified criteria, several databases were systematically searched and 279 abstracts highlighted; 215 articles were subsequently screened with a total of 104 articles being retained for specified quality criteria screening and critique. Results: Following critique, a total of 19 articles were retained for their relevance to the research question. Conclusions: The literature presented sufficient information to enable the investigator to propose a model describing the mechanism for PTSD development in ICU. Despite the extensive selection and screening process, most articles contained methodological flaws, however the investigator advocates that the information provided by the literature should not be dismissed and that future research might be directed towards replication of such research to RCT standards. Part Two: Research Report - Introduction: Despite the literature indicating that PTSD and other forms of psychological distress are significant problems for intensive care unit patients, the mechanisms involved in the development of PTSD remain largely unexplained. The investigator hypothesised that PTSD may occur as a result of implicit learning/classical conditioning/pairing of auditory stimuli to emotional distress experienced in the intensive care unit. Aim: To test the hypothesis that classical conditioning (pairing) of ICU environment sounds to patient distress or anxiety in the ICU which can then be detected after discharge as an emotional conditioned response to the presentation of a range of sounds (Train/Rain and ICU) sounds whilst monitoring skin conductance. Method: Thirty-three patients were recruited into the study and twenty participants were able to provide data to permit testing relating to the main hypothesis at 4-5 weeks post-ICU discharge. Results: A non-significant trend was noted in the relationship between presentation of ICU sounds and increased skin conductance responses, but the investigator was unable to find significant evidence of any relationship between skin conductance responses to ICU sounds and measures of psychological distress. There was significant evidence to suggest that the presence of memories as measured by the ICU Memory Tool at one-to-two weeks post-discharged from ICU were related to PTSD development. Conclusion: Patients demonstrating increased memories of feelings at one-to-two weeks, should be monitored carefully for any subsequent signs of PTSD and other forms of psychological distress. Future research should perhaps attempt to replicate the ICU sounds findings in a larger sample size with comprehensive recording of ICU sedation and memory phenomena details. Any attempts to find evidence of implicit memory using prompted recall questions should plan to capture this within 24 hours of stimuli presentation. Part Three: Critical Appraisal - Reflections regarding the research process and content are discussed.