Dexmedetomidine Infusion for More Than 24 Hours in Critically Ill Patients: Sedative and Cardiovascular Effects

Objective: To assess the potential of dexmedetomidine for targeted sedation in complex Intensive Care (ICU) patients for >24 h.

Design: Prospective, open label, clinical trial.

Setting: Tertiary general ICU.

Patients: Twenty critically ill patients, mean APACHE II 23(+/-9).

Interventions: A continuous infusion of dexmedetomidine, median infusion time 71.5 (35-168) h, starting at 0.4 microg.kg.h without a loading dose and adjusted (0.2-0.7 microg.kg.h) to a target Ramsay Sedation Score (RSS) of 2-4. Rescue midazolam and/or morphine/fentanyl were given as clinically indicated.

Measurements And Results: Haemodynamic parameters and RSSs were collected until 24 h after cessation. An RSS 2-5 was achieved in 1,147 (83%) of observations with a reduction in RSS of 6 from 13% in the first 6 h to 3% between 18 h and 24 h. Sixteen patients needed minimal or no additional midazolam, median 4 mg/day (0.5-10) and ten required minimal or no additional analgesia, median 2 mg/day (0.5-4.5), 55 microg/day (14-63) of morphine/fentanyl.

Results: A 16% reduction in mean systolic blood pressure (SBP) and 21% reduction in heart rate (HR) occurred over the first 4 h followed by minimal (+/- 10%) changes throughout the infusion. A rise in SBP was observed in two patients. After abrupt cessation, SBP and HR monitored for 24 h rose by 7% and 11%, respectively.

Conclusions: Dexmedetomidine was an effective sedative and analgesic sparing drug in critically ill patients when used without a loading dose for longer than 24 h with predictable falls in blood pressure and HR. There was no evidence of cardiovascular rebound 24 h after abrupt cessation of infusion.