Beneview t5

The carotid artery was exposed via surgical cut-down and catheterized using a 24-gauge catheter (Introcan; B-Braun, Brazil); this was connected to a pressure transducer system for direct blood pressure monitoring and the collection of arterial blood to determine blood gases. Systolic, diastolic and mean arterial blood pressures (SAP, DAP and MAP, respectively) and heart rate (HR) were continuously monitored (BeneView T5, Mindray, Nanshan, China). For blood gas analysis, 0.3 mL of blood was obtained immediately before the first noxious stimulation and another one after determining the MAC (GEM Premier 3000; Instrumentation Laboratory, UK). The rectal temperature was maintained between 37°C and 38°C by means of a Convective Warming System (Equator®, SurgiVet®, Smiths Medical PM Inc., USA). The tail vein was catheterized using a 24-gauge catheter for the administration of drugs (Introcan; B-Braun, Brazil). Inspired ISO (Fi_Iso), end-tidal (Fe_Iso) concentrations, end-tidal carbon dioxide tension (PEtCO₂) and respiratory rate (RR) were continuously measured with an infrared gas analyzer (BeneView T5, mindray, Multi-gas offers, Nanshan, China) by endotracheal gas sampling (60 mL/min) obtained by means of a catheter inserted through the endotracheal tube with the tip located at the level of the carina.

The temperature of the operating room was maintained at 23–25 °C throughout the study. There were no pre-operation medications, and food access was forbidden for 6 h before surgery. All the parturients were placed under standard monitoring with BeneView T5 (MINDRAY, CHINA), received preload warmed colloid (Hydroxyethyl starch 130/0.4 10 mL•kg⁻¹), and crystalloid infusion (lactated Ringers solution 10 mL•kg⁻¹) for the prevention of hypotension. A fluid warmer (Barkey S-line, Germany) was used for perioperative fluid therapy. A thermometer was inset 7–10 cm to the rectum as the core temperature monitor before the anesthesia.
The patient was in the lateral decubitus position. SA was performed with the patient at L2–L3 or L3–L4 intervertebral space with a 25G Quincke’s spinal needle, using the needle-in-needle technique. Isobaric local anesthetic with normal temperature was used for SA in each group. 2–2.5 mL of 0.5% bupivacaine (determined at the discretion of the attending anesthesiologists) was intrathecally injected with 1 mL per 5–8 s in group B, and 2–2.5 mL of 0.5% ropivacaine was intrathecally injected with the same speed in group R. Then the epidural catheter was inset 3–5 cm to epidural space at the same intervertebral space for post-operative analgesia.

Anesthesia induction was conducted by placing each rat in the induction chamber providing 5% isoflurane (Forane; Baxter Laboratories, USA) in a continuous oxygen flow of 5 L/min. Once the animal was anesthetized, tracheal intubation was performed with the animal positioned in dorsal recumbency using a 16-gauge catheter (Introcan; B-Braun, Brazil). A flexible, blunt-tip, wire guide was inserted into the trachea with an otoscope and used to direct the endotracheal catheter. Correct placement of the catheter was confirmed by CO₂ infrared–absorption analysis (BeneView T5, mindray, Multi-gas offers, Nanshan, China). The catheter was then connected to a small T-piece breathing system with minimal dead space and a fresh gas flow of 1 L/min of oxygen. The isoflurane concentration was adjusted as necessary based on assessment of the palpebral reflex and hemodynamic responses during instrumentation. During the study, the rats were breathing spontaneously.