Effects of mild hypoalbuminemia on the pharmacokinetics and pharmacodynamics of dexmedetomidine in patients after major abdominal or thoracic surgery

• This study indicated that maximum plasma concentration of dexmedetomidine decreased by 21.2% in patients with mild hypoalbuminemia, compared with patients with normoalbuminemia. Its volume of distribution at steady state increased by 40.5%; elimination half-life decreased by 33.5%. However, heart rates, arterial pressures, and Ramsay sedation scores did not differ significantly between the 2 groups. No serious adverse events occurred in either patients with normoalbuminemia or hypoalbuminemia.
• These results suggest that dexmedetomidine infusion can safely be used in mild hypoalbuminemia patients after major abdominal or thoracic surgery.

Study ObjectiveTo explore the effects of mild hypoalbuminemia on pharmacokinetics and pharmacodynamics of dexmedetomidine in patients after major abdominal or thoracic surgery.DesignA prospective cohort study.SettingUniversity-affiliated teaching hospital.PatientsThe study was performed in 30 consecutive patients undergoing major abdominal or thoracic surgery. They were aged 18 to 65 years and graded as American Society of Anesthesiologists physical status I and II. All patients were scheduled to require more than 6 hours of postoperative sedation and mechanical ventilation. Nine of the patients had low plasma albumin levels (< 35 g/L but > 24 g/L; male/female, 6/3) after the operation, who were assigned to hypoalbuminemia group, and the remainder with normoalbuminemia (> 35 g/L; male/female, 15/6) were assigned to normoalbuminemia group.InterventionsAll patients were administered a loading dose of dexmedetomidine 1.0 μg/kg infused over 10 minutes after admitted into intensive care unit and a maintenance dose of 0.4 μg/kg per hour followed for 6 hours.MeasurementsPlasma dexmedetomidine levels were determined by high performance liquid chromatography – mass spectrum. Sedation was evaluated using Ramsay sedation score. Heart rate and arterial pressures were monitored. Adverse events were recorded.Main ResultsCompared with patients with normoalbuminemia, maximum plasma concentration of dexmedetomidine decreased by 21.2% in patients with hypoalbuminemia (P < .01). Its volume of distribution at steady state increased by 40.5%; elimination half-life decreased by 33.5% (P < .01). However, heart rates, arterial pressures, and Ramsay sedation scores did not differ significantly between the 2 groups. No serious adverse events occurred in either the patients with hypoalbuminemia or normoalbuminemia.ConclusionsSedation and adverse reactions of dexmedetomidine infusion did not differ significantly between patients with mild hypoalbuminemia and normoalbuminemia, although its volume of distribution at steady state increased and elimination half-life shortened in patients with hypoalbuminemia. This suggests that dexmedetomidine infusion can safely be used in mild hypoalbuminemia patients after major abdominal or thoracic surgery.