Upon enrolment, the patients arriving at the operation theatre without premedication were given 8 ml kg−1 Ringer’s solution via an intraoperative maintenance infusion of 4 ml kg−1 h−1. Standard physical monitoring was performed using an automated non-invasive blood pressure (BP) monitor, 5-lead ECG and pulse oximetry. Systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP) and HR were recorded at intervals of 5 min during the entire operation. To objectively record the baseline parameters, baseline measurements were defined using the average of three readings obtained at an interval of 5 min before induction in the supine position on the operation bed.
PNB (femoral and sciatic nerve blocks) was performed under ultrasound guidance combined with a nerve stimulator (MultiStim SENSOR, PAJUNK, Geisingen, Germany). If electrical stimulation of ≤ 0.5 mA elicited a visible motor response in the quadriceps femoris for femoral nerve or in the gastrocnemius for sciatic nerve, approximately 20 ml of ropivacaine hydrochloride (3.5 mg ml−1) (Naropin, AstraZeneca AB, Sodertalje, Sweden) was injected. The block was considered satisfactory after confirming the presence of complete motor and sensory blocks. The presence of a motor block was assessed using the modified Bromage scale for the lower limb (0: normal motor function; 1: ability to only move the toes; and 2: inability to move the knee, ankle and toes), with a Bromage score of 2 indicating a complete block. The presence of a sensory block was assessed via the pin-prick method using a 26G hypodermic needle along the midline of the lower limb [15 (link)]. A successful sensory block was defined as a complete lack of pain sensation at the surgical field level. Patients who successfully achieved a complete block were randomly administered with 1.5 µg kg−1 h−1 DEX [16 (link)] (H20090248, Jiangsu Hengrui Pharmaceuticals Co., Ltd, Lianyungang, Jiangsu, China) or 50 µg kg−1 h−1MID (H10980025, Jiangsu Nhwa Pharmaceutical Co., Ltd, Xuzhou, China) [17 (link)]. The drug dosage was calculated according to the lean body weight (LBM), and the drugs were continuously administered during the procedure until wound irrigation. The parameters were recorded even after the operation was completed.
During inhalation of air, side effects such as hypotension (SBP < 90 mmHg or DBP < 60 mmHg), bradycardia (HR < 55 bpm) and hypoxemia (SpO2 level < 93%) were observed and noted. An SpO2 level of < 93% was treated with 2–4 l min−1 oxygen administration. Hypotension was treated with 6 mg of intravenous ephedrine administration. Further, sinus bradycardia was treated with 0.5 mg of intravenous atropine administration. These side effects were reported by the anaesthesiologist who was blinded to the study protocol.
PNB (femoral and sciatic nerve blocks) was performed under ultrasound guidance combined with a nerve stimulator (MultiStim SENSOR, PAJUNK, Geisingen, Germany). If electrical stimulation of ≤ 0.5 mA elicited a visible motor response in the quadriceps femoris for femoral nerve or in the gastrocnemius for sciatic nerve, approximately 20 ml of ropivacaine hydrochloride (3.5 mg ml−1) (Naropin, AstraZeneca AB, Sodertalje, Sweden) was injected. The block was considered satisfactory after confirming the presence of complete motor and sensory blocks. The presence of a motor block was assessed using the modified Bromage scale for the lower limb (0: normal motor function; 1: ability to only move the toes; and 2: inability to move the knee, ankle and toes), with a Bromage score of 2 indicating a complete block. The presence of a sensory block was assessed via the pin-prick method using a 26G hypodermic needle along the midline of the lower limb [15 (link)]. A successful sensory block was defined as a complete lack of pain sensation at the surgical field level. Patients who successfully achieved a complete block were randomly administered with 1.5 µg kg−1 h−1 DEX [16 (link)] (H20090248, Jiangsu Hengrui Pharmaceuticals Co., Ltd, Lianyungang, Jiangsu, China) or 50 µg kg−1 h−1MID (H10980025, Jiangsu Nhwa Pharmaceutical Co., Ltd, Xuzhou, China) [17 (link)]. The drug dosage was calculated according to the lean body weight (LBM), and the drugs were continuously administered during the procedure until wound irrigation. The parameters were recorded even after the operation was completed.
During inhalation of air, side effects such as hypotension (SBP < 90 mmHg or DBP < 60 mmHg), bradycardia (HR < 55 bpm) and hypoxemia (SpO2 level < 93%) were observed and noted. An SpO2 level of < 93% was treated with 2–4 l min−1 oxygen administration. Hypotension was treated with 6 mg of intravenous ephedrine administration. Further, sinus bradycardia was treated with 0.5 mg of intravenous atropine administration. These side effects were reported by the anaesthesiologist who was blinded to the study protocol.
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