Clinical Research Directory

Inclusion Criteria: * Age ≥18 years old; * Non-mechanical ventilation patients with expected ICU stay time \>24h * People with moderate to severe pain who need immediate analgesic treatment (NRS ≥ 4 or BPS ≥ 5 points, CPOT ≥ 3); Exclusion Criteria: * During pregnancy or breastfeeding； * Confirmed acute severe intracranial or spinal nerve disease caused by vascular, infection, intracranial dilation or injury; * Non-compensatory acute circulatory failure (severe hypotension with MAP\<55 mmHg even if sufficient fluid resuscitation and vascular compression therapy); * Severe bradycardia (heart rate\<55 beats/min) or heart block of degree II-III (excluding those with pacemakers installed); * Unable to obtain pain scores or any other conditions that may seriously interfere with the collection of research data; * Have used analgesics other than remifentanil during mechanical ventilation in the ICU; * Having a history of long-term use of opioid drugs or opioid addiction; * Known allergy history of experimental drugs; * Suffering from severe or acute asthma, or respiratory depression caused by severe carbon dioxide retention, head injury, and intracranial damage; * Danger period intestinal obstruction (present or at risk of progression to gastrointestinal obstruction, especially in patients with paralytic intestinal obstruction); * Having participated in this study or any other intervention studies (any study that assigns patients to different treatment groups); * Unsuitable to participate in this experiment according to the judgment of the researchers.