Timing of Intraoperative Dexmedetomidine Administration and Post-anaesthesia Care Unit Recovery

Background

Dexmedetomidine is increasingly used in multimodal perioperative analgesia due to its sedative, anxiolytic, and opioid-sparing properties. However, concerns remain regarding residual sedation, haemodynamic instability, and delayed post-anaesthesia care unit (PACU) discharge, particularly when administered close to the end of surgery. This audit aimed to characterise intraoperative dexmedetomidine use at a tertiary Australian hospital and evaluate the relationship between administration timing, PACU clinical recovery time, and postoperative complications.

Methods

A retrospective single-centre quality improvement audit was conducted at the Royal Brisbane and Women’s Hospital, Brisbane, Queensland, Australia. Adult surgical patients who received intraoperative dexmedetomidine between 1 January 2025 and 19 February 2025 were identified from electronic anaesthetic records. Patients were excluded if they were younger than 18 years, were admitted directly to intensive care, or did not recover in PACU. Data collected included anaesthetic technique, dexmedetomidine dose and administration method, timing of administration, PACU clinical recovery time, sedation scores, pain scores, oral morphine equivalent requirements and postoperative complications. Categorical outcomes were compared using Fisher’s exact test, while non-parametric continuous outcomes were compared using the Mann-Whitney U test.

Results

Of 230 records reviewed, 225 patients met the inclusion criteria. General anaesthesia was used in 162 (72.0%) cases, while regional anaesthesia or procedural sedation was used in 63 (28.0%). Dexmedetomidine was most commonly administered as a bolus only, occurring in 188 (83.6%) patients. Median PACU clinical recovery time was 64 minutes. Postoperative opioid requirements were low, with seven (3.1%) patients requiring more than 60 mg of oral morphine equivalents. Overall, bradycardia occurred in 53 (23.6%) patients, hypotension in 24 (10.7%), and postoperative nausea and vomiting in 20 (8.9%). Dexmedetomidine administration within 60 minutes of procedure completion was associated with shorter median PACU clinical recovery time than administration more than 60 minutes before completion (58.5 vs 83.0 minutes, Mann-Whitney U=4418, p=0.006). Bradycardia, hypotension, and postoperative nausea and vomiting were numerically more common in the within-60-minute group, although these differences were not statistically significant.

Conclusion

PACU recovery outcomes were generally favourable in this cohort of adult surgical patients who received intraoperative dexmedetomidine, with low postoperative opioid requirements. Administration within 60 minutes of procedure completion was associated with shorter median PACU clinical recovery time than earlier administration; however, this retrospective observational audit cannot determine causality, and the finding may reflect confounding by procedure duration, anaesthetic technique, dose, surgical complexity or case mix. Bradycardia, hypotension, and postoperative nausea and vomiting were numerically more common with later administration, but these differences were not statistically significant. These findings should therefore be interpreted as exploratory and hypothesis-generating, with prospective studies and adjusted analyses required to determine whether dexmedetomidine timing independently influences PACU recovery or early postoperative complications.