Anesthetic procedure
pain
STERILE, DECUBITUS
All patients fasted for 6 h and discontinued fluid intake 2 h before cesarean section. No patient was given premedication. After an intravenous catheter was placed, the patient was transported to the operating room, where standard ASA monitors were placed and a volume of 500 mL of Ringer’s lactate solution was started. With the patient in a left lateral decubitus position, a 25-gauge pencil-point needle was introduced into the subarachnoid space at the L3-L4 or L2-L3 interspace using the single-space needle-through-needle technique in a standard sterile fashion. After the return of clear cerebrospinal fluid, a 2.5 mL freshly prepared mixed solution containing plain ropivacaine (Naropin®, AstraZeneca AB Company, Sodertalje, Sweden) 8 mg + dexmedetomidine (Dexmedetomidine Hydrochloride Injection, 200 µg per 2 mL, Jiangsu Yangzi River Pharmaceutical Co., Ltd.; preservative-free and contains no additives or chemical stabilizers) (Group RopThe mixed solutions for spinal anesthesia were previously prepared by an independent anesthesiologist not involved further in the trial. A second anesthesiologist who was blinded to the details of the mixed solutions performed the CSEA procedure and intraoperative management as well as the subsequent assessments. A 1 mL insulin syringe was used for measuring volumes ≤ 1 mL. Dexmedetomidine for the present study was prepared by withdrawing 0.1 mL (10 µg) of dexmedetomidine from an ampoule of 100 µg·mLThe dose of dexmedetomidine for the first patient in each group was 5 µg. The dose of dexmedetomidine for the following patient was determined by the response of the previous patient to the intrathecal mixed solution in the same group according to the up-down sequential allocation method. If the response of the previous patient was effective, the dose of intrathecal dexmedetomidine for the subsequent patient was decreased by 1 µg. If the response of the patient was ineffective, the dose for the subsequent patient was increased by 1 µg. In case of an effective response in 1 µg or an ineffective response in 10 µg, the dose for the subsequent patients would remain the same until an ineffective response or an effective response prompted the anesthesiologist to increase or decrease the dose, respectively. An effective intrathecal block was defined as a bilateral sensory level to pinprick of T6 or above, which was achieved within 10 min after injection of spinal solution without the requirement of additional intraoperative epidural anesthetic. The ineffective intrathecal block was defined as failure to obtain a bilateral sensory level to pinprick of T6 within 10 min of intrathecal drug administration, or additional analgesia was required to complete surgery because of either a visual analog score (VAS; 0–10; 0 = no pain and 10 = worse pain imaginable) greater than 2, or the patient’s request for additional analgesia, despite achieving T6 sensory level block. In cases of ineffective response, supplemental epidural anesthesia consisting of 2% lidocaine was administered as 5 mL bolus injections, repeated every 5 min if necessary [