Aims: Propofol may result in hypotension, bradycardia and loss of protective reflexes, especially in elderly patients, while esketamine, a N-methyl-D-aspartate receptor antagonist, has analgesic, anaesthetic and sympathomimetic properties and is known to cause less cardiorespiratory depression. We hypothesized that esketamine may reduce the median effective concentration (EC50 ) of propofol and coadministration is less likely to produce hypotension during gastrointestinal endoscopy in elderly patients.
Methods: Ninety elderly patients, aged 65-89 years, undergoing gastrointestinal endoscopy were randomly assigned into 3 groups: SK0 (control) group (0 mg/kg esketamine); SK0.25 group (0.25 mg/kg esketamine); and SK0.5 group (0.5 mg/kg esketamine). Anaesthesia was achieved by plasma target-controlled infusion of propofol with different bolus doses of esketamine. The EC50 of propofol for gastrointestinal endoscopy was determined by using the up-and-down method of Dixon. The initial plasma target concentration is 2.5 μg/mL and the adjacent concentration gradient is 0.5 μg/mL. Cardiovascular variables were also measured.
Results: Propofol EC50 s and its 95% confidence interval for gastrointestinal endoscopy in elderly patients were 3.69 (2.59-4.78), 2.45 (1.85-3.05) and 1.71 (1.15-2.27) μg/mL in the SK0, SK0.25 and SK0.5 groups, respectively (P < .05). The average percent change from baseline mean arterial pressure was -19.7 (7.55), -15.2 (7.14) and -10.1 (6.73), in the SK0, SK0.25 and SK0.5 groups, respectively (P < .001).
Conclusion: Combination medication of propofol with esketamine reduced the propofol EC50 during gastrointestinal endoscopy in elderly patients compared with administration of propofol without esketamine. Increasing doses of SK with propofol are less likely to produce hypotension with shorter recovery time.
Keywords: EC50; elderly patients; esketamine; propofol.
© 2021 British Pharmacological Society.