Effects of Mild Hypoalbuminemia on the Pharmacokinetics and Pharmacodynamics of Dexmedetomidine in Patients After Major Abdominal or Thoracic Surgery

Study Objective: To explore the effects of mild hypoalbuminemia on pharmacokinetics and pharmacodynamics of dexmedetomidine in patients after major abdominal or thoracic surgery.

Design: A prospective cohort study.

Setting: University-affiliated teaching hospital.

Patients: The 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.

Interventions: All 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.

Measurements: Plasma 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 Results: Compared 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.

Conclusions: Sedation 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.