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Morphine and remifentanil and their effects on dreams, nightmares and hallucinations in critically ill patients


Dreaming, nightmares and hallucinations are common in the critically ill and have many causes. These may lead to serious adverse psychological sequelae such as post-traumatic stress disorder. The type of sedation and analgesia used to make patients comfortable may influence this. Morphine causes dreams because of its μ-agonist effects. It is unknown if the new highly lipophilic and potent opioid remifentanil is different.


We studied the influence of sedative practice on many variables over an 8 month period in 2002. During the first period of 12 weeks, 'conventional' sedative and analgesic techniques were used where midazolam and propofol were titrated to make the patient comfortable and analgesics added. Over the next 2 months we developed guidelines for the use of remifentanil relieving pain first and adding hypnotics only if needed. The final 12 weeks involved using remifentanil as the major sedative agent in the ICU, as part of an analgesia-based regimen. As part of the followup in the first 4 days after discharge all patients are asked whether they had any dreams, nightmares or hallucinations and, if so, were they distressing?


In the first 12 weeks, 47 patients were followed up and 20 (42%) of them experienced dreams or hallucinations, 13 (65%) did find the experience distressing. These patients all received morphine in combination with midazolam and propofol. In the final 12 weeks, 57 patients were seen and 28 (49%) of them experienced dreams or hallucinations and 16 patients (57%) found them unpleasant or distressing. Morphine (12), remifentanil (12), propofol (9) and midazolam (2) were given to 26/28. Two patients received no sedative or analgesic drugs.


This study shows that the use of potent opioids, such as remifentanil, does not increase the risk of dreaming. Some patients have distressing dreams despite having had no hypnotic or analgesic drugs.

Conflict of interest statement

This study was sponsored by Elan Pharma Ltd and GSK Ltd.


We thank the medical and nursing staff of the ICU for their invaluable contribution to this study.

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Lane, M., Serrano, A., Walters, S. et al. Morphine and remifentanil and their effects on dreams, nightmares and hallucinations in critically ill patients. Crit Care 7, P097 (2003).

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  • Morphine
  • Emergency Medicine
  • Midazolam
  • Stress Disorder
  • Remifentanil