Many patients in the general intensive care unit experience pain, as a result of an injury or underlying disease, surgery or an invasive procedure.

Pain management is an integral part of the treatment of critical patients, and this is first and foremost to alleviate their suffering. Along with this, there is another therapeutic benefit in the form of relief from symptoms accompanying pain such as an increase in oxygen consumption, immune changes, hyper metabolism etc.

Currently, the pain treatment is based on a multi-modal analgesia approach in which drugs from several drug groups and different mechanisms are given, in order to relieve the pain by suppressing several nerve and inflammatory pathways. However, the treatment is still based on opioids, despite multiple adverse effects, including tolerance and withdrawal syndrome.

Opioids affect several receptors, mainly the µ receptor, in an agonistic, antagonistic or agonistic-antagonistic manner. The main opioids used for pain relief in the intensive care unit are morphine, fentanyl and remifentanil.

After prolonged treatment with opioids, a sudden cessation of their use will result in a withdrawal syndrome which will manifest itself in delirium, restlessness, hypertension, anxiety, sweating, vomiting etc. (2-3). In order to avoid the withdrawal syndrome, the dose must be tapered down gradually, often using alternative long-term opioids, such as methadone and buprenorphine (-4).

In the general intensive care unit at our institution, patients were treated with fentanyl patches in decreasing doses in order to lead the patient safely through the withdrawal syndrome, while trying to reduce the negative physiological effects as much as possible. In November 2021, we started using oral methadone instead of fentanyl patches, as a long acting opioid, as used in many ICU's worldwide, in order to avoid withdrawal syndrome in patients who received continuous infusion of short-acting opioids, such as remifentanil, for long periods of time while being intubated and ventilated. In the past year since the methadone treatment was started, 50 patients were treated in the unit with methadone with the indication of relieving the withdrawal symptoms from opioids.

We intent to investigate whether there is a difference in the incidence of delirium in patients who were treated with methadone vs patients who were treated with fentanyl patches in order to alleviate withdrawal symptoms.

Inclusion Criteria:All patients aged 18-99 who were treated with methadone in the intensive care unit from November 2021 to November 2022, as well as all patients aged 18-99 who were admitted to the intensive care unit from November 2020 to November 2021 and were treated with a fentanyl patch as a control group.

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Exclusion Criteria:None

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All patients aged 18-99 who were treated with methadone in the intensive care unit from November 2021 to November 2022, as well as all patients aged 18-99 who were admitted to the intensive care unit from November 2020 to November 2021 and were treated with a fentanyl patch as a control group.