Comparison of the effect of dexmedetomidine intrathecal injection and intravenous infusion on subarachnoid blockade during knee arthroscopy procedures

Abstract

Abstract Background: Comparison of whether intrathecal dexmedetomidine prolongs spinal anesthesia-associated sensorimotor blockade more than intravenous infusion during knee arthroscopy procedures performed under subarachnoid block. Methods: Ninety patients aged 18-75 years, ASA class I-II, who underwent knee arthroscopy between October 2022 and April 2023 were randomized into intrathecal、intravenous and control groups.Subjects received three modes of administration: an intrathecal group (2ml of 1% ropivacaine + 5μg of dexmedetomidine，with saline pumped intravenously at a dose of 0.5μg/kg/h), an intravenous group (intrathecal 2ml of 1% ropivacaine +1ml of 0.9% saline, with dexmedetomidine pumped intravenously at a dose of 0.5μg/kg/h), and a control group (intrathecal 2ml of 1% ropivacaine + 1ml of 0.9% saline, with saline pumped intravenously at a dose of 0.5μg/kg/h). Total analgesic duration, duration of sensory and motor blockade, Ramsay sedation score, Visual Analogue Score (VAS) at different postoperative time points, and occurrence of adverse effects were recorded. Results：The total analgesia duration was significantly longer in the intrathecal group than in the intravenous and control groups (352.13±51.70min VS 273.47±62.57min VS 241.41±59.22min，P<0.001).The duration of sensory block was shorter in the intrathecal group than in the intravenous and control groups (4 [3-4]min VS 5 [4-5]min VS 5 [4-5]min；P<0.001);the duration of motor block was shorter in the intrathecal group than in the intravenous group and the control group (5 [4-5]min VS 5 [5-6]min VS 6[5.5-7]min；P<0.001).Sedation scores were higher in the intravenous group than in the intrathecal and control groups (P < 0.001). At 5 hours postoperatively, the VAS score in the intrathecal group was smaller than that in the intravenous and control groups (P<0.001). At 24 hours postoperatively, the VAS score in the intrathecal group was smaller than that in the control group (P < 0.001). In addition, the incidence of bradycardia was significantly higher in the intravenous group than in the intrathecal and control groups (30%, 6.5%, and 3.4%, respectively; P=0.018，P=0.007). Conclusions：Intrathecal administration of dexmedetomidine did prolong the total analgesia duration, as well as accelerate the onset of sensory-motor blockade compared with intravenous pumping, and did not result in any hemodynamic instability or other adverse events at the doses studied. Trial registration:This single-center, prospective, RCT has completed the registration of the Chinese Clinical Trial Center at 26/09/2023 with the registration number ChiCTR2300076170.