The objective of this study was to examine the association of delusional and real memories for events with both the pre-operative and early post-operative clinical condition and to examine interventional, supportive and therapeutic factors. Its design was retrospective, using a questionnaire and review of clinical records. The study was carried out in a university teaching hospital cardiothoracic intensive care unit (ICU) on 161 patients without professional experience of intensive care, who had received four days or more in intensive care after cardiac surgery.
Its main outcome measures were the prevalence of delusional memory persisting after recovery and the recall of real events whilst in intensive care. Seventy-eight (48%) patients recalled events apparently occurring whilst in intensive care, which were delusional or hallucination-like (‘dreamers’). This group recalled a mean of 2.6 of a possible 10 normal intensive care events compared with 1.0 of 10 for those who were not able to recall delusions or hallucinations (‘non-dreamers’). Dreamers were younger at the time of surgery (mean age 63.6 vs. 68.9 years, p=0.003). Dreaming was more common in patients who received intravenous glucose (to treat hypoglycaemia), midazolam, steroids and in those with episode(s) of sepsis.
We concluded vivid memory of unreal events is common after discharge from intensive care. The aetiology is probably multifactorial. The retrospective nature and the inexact methods preclude confirming that midazolam is a direct, much less a causal, risk factor. However, the association is strong enough to warrant prospective studies.
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