Abstract
Background: Propofol may result in hypotension, bradycardia,
and loss of protective reflexes, especially in elderly patients, while
esketamine, a N-methyl-D-aspartate receptor antagonists, 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 cause more stable haemodynamic responses during gastrointestinal
endoscopy in elderly patients. Methods: Ninety elderly
patients, aged 65-89 years, undergoing gastrointestinal endoscopy were
randomly assigned into three groups: SK0.25 group (0.25 mg/kg
esketamine), SK0.5 group (0.5 mg/kg esketamine) and saline control
group. Anaesthesia was achieved by target-controlled infusion of
propofol with an initial plasma concentration of 2.5 μg/ml with
different bolus doses of esketamine during gastrointestinal endoscopy.
The EC50 of propofol for gastrointestinal endoscopy was
determined by using an up-and-down method of Dixon with an adjacent
concentration gradient at 0.5μg/mL to prohibit purposeful movements.
Cardiovascular parameters were also measured and recorded.Results: Propofol EC50 and its 95% confidence
interval for gastrointestinal endoscopy in elderly patients were 1.71
(1.15-2.27) μg/mL in SK0.5 group, 2.45 (1.85-3.05) μg/mL in SK0.25 group
and 3.69 (2.59-4.78) μg/mL in control group respectively (P <
0.05). The average percent change to baseline mean arterial pressure
(MBP) was -19.7 (7.55), -15.2 (7.14) and -10.1 (6.73) with P<0.001, in
the control group, the SK0.25 group and the SK0.5 group, respectively.Conclusions: Combination medication of propofol with esketamine
reduced the propofol EC50 during gastrointestinal
endoscopy in elderly patients and caused more stable haemodynamic
responses compared with single administration of propofol.