Target‐controlled infusion of dexmedetomidine effect‐site concentration for sedation in patients undergoing spinal anaesthesia

Abstract

What is known and objective Dexmedetomidine has been a preferred sedative for patients undergoing regional anaesthesia and is mostly administered via conventional zero‐order infusion. Recently, a pharmacokinetic‐pharmacodynamic (PKPD) model of dexmedetomidine has been published, but no external validation has been reported in clinical trials. We aimed to administer target‐controlled infusion (TCI) of dexmedetomidine at the effect‐site concentration (Ce) to patients undergoing spinal anaesthesia and investigate the relationship between dexmedetomidine Ce and the sedative effects. Methods Forty‐five patients scheduled for orthopaedic surgery received spinal anaesthesia with 0.5% bupivacaine. After confirmation of sensory block level, we initiated effect‐site TCI of dexmedetomidine using Colin's model and assessed sedation levels using the Modified Observer's Assessment of Alertness/Sedation (MOAA/S) scale and bispectral index (BIS) with each stepwise increase in the dexmedetomidine Ce. We used a non‐linear mixed‐effects model to determine the PD relationships between the dexmedetomidine Ce and sedation level. Results The dexmedetomidine Ce associated with 50% probability (Ce50) of the MOAA/S scale ≤4, 3 and 2 was 0.57, 0.89 and 1.19 ng/mL, respectively. Mean dexmedetomidine Ce when BIS decreased ≤70 was 0.99 ± 0.15 ng/mL. As dexmedetomidine Ce increased, the MOAA/S scale decreased significantly (correlation coefficient [r] = −.832, P < .0001). BIS decreased significantly with increasing dexmedetomidine Ce (r = −.811, P < .0001) and decreasing MOAA/S scale (r = .838, P < .0001). The most common side effects were hypertension (26.67%) and bradycardia (20%). What is new and conclusion We applied effect‐site TCI of dexmedetomidine in patients undergoing spinal anaesthesia for the first time. Dexmedetomidine Ce correlated significantly with MOAA/S scale and BIS, and was 0.89 and 1.19 ng/mL for moderate and deep sedation, respectively.

Verification of the performance of the Bispectral Index as a hypnotic depth indicator during dexmedetomidine sedation

“…In the current study, we targeted patients who were undergoing surgery under spinal anesthesia and were treated with dexmedetomidine, which was administered as described in the pharmacopeia (a popular method). A significant correlation between the BIS value and MOAA/S score was observed, as reported in previous studies [16][17][18][19][20][21]. However, the average value of the BIS for specific sedation level showed difference.…”

“…Several studies have evaluated the performance of BIS and its correlations with clinical sedation scales (Richmond agitation-sedation scale, Ramsay sedation scale, and OAA/S) under dexmedetomidine sedation and reported that the performance of the BIS was reliable during dexmedetomidine sedation. However, most of these studies were conducted in ICU patients who were on mechanical ventilation, and one study was conducted in patients undergoing spinal anesthesia with dexmedetomidine sedation using target-controlled infusion, a method not often used in clinical practice because it requires a special infusion pump [16][17][18][19]. In the current study, we targeted patients who were undergoing surgery under spinal anesthesia and were treated with dexmedetomidine, which was administered as described in the pharmacopeia (a popular method).…”

Application of Different Doses of Dexmedetomidine Combined with General Anesthesia in Anesthesia of Patients with Traumatic Tibiofibular Fractures and Its Effect on the Incidence of Adverse Reactions

“…Propofol (5 mg/kg•h) and remifentanil (0.2 μg/ kg•min) were micropumped to maintain intraoperative general anesthesia, and cisatracurium was given according to the actual situation of the patients. Additional intravenous anesthetics were stopped at 30 min before the end of surgery, and the pumping of dexmedetomidine was stopped before suturing [11][12][13]. e secretions in the catheter and oral cavity were aspirated at the end of the surgery.…”

The role of pharmacokinetics and pharmacodynamics in clinical anaesthesia practice

“…The pharmacodynamic model is complex and describes four clinical effects: the BIS, the Modified Observer's Assessment of Alertness/Sedation (MOAA/S) score, heart rate and mean arterial pressure. Despite the complexity, use of this model for TCI enables the anaesthetist to titrate the drug to achieve a desired BIS or probability of a certain MOAA/S score [26], whereas the model also provides information about the other effects (magnitude of bradycardia and the likely change in blood pressure from baseline).…”