A Randomized, Parallel-group, Safety-assessor-blinded Phase IV Study to Estimate the Influence of Mild Hypothermia on Reversal of Rocuronium-induced Neuromuscular Block With Sugammadex

This randomized, parallel-group, safety-assessor-blinded phase IV study will be conducted. The study is conducted in accordance with principles of Good Clinical Practice and is approved by the appropriate Institutional Review Boards and regulatory agencies. Written informed consent is obtained from all patients.

In total, 60 patients, aged from 20 to 65 years, with an American Society of Anesthesiologists physical status of I or II and undergoing elective abdominal surgery with a general anesthesia in the supine position will be studied. Patients are excluded if they are expected to have a difficult airway, known neuromuscular disease, significant hepatic or renal dysfunction, family history of malignant hyperthermia, known allergy to one of the drugs used in this protocol, intake of any medication that might interact with muscle relaxants, pregnant, or breast feeding.

The anesthetized patients are randomly assigned to 2 groups as normal thermal condition with core temperatures between 36.5°C and 37°C (C group) and mild hypothermia with core temperatures between 34.5°C and 35°C (H group) in deep block state (1-2 twitches post-tetanic count). The randomization is performed by using computer-generated sealed envelopes to determine which condition (normal thermal condition or mild hypothermia) the patients are performed during deep block state (1-2 twitches post-tetanic count). The anesthesiologist remains blinded to the C group or H group during deep block state (1-2 twitches post-tetanic count) given throughout the remaining course of anesthesia. No premedication is given. After arrival to the operating room, electrocardiography, non-invasive measurement of blood pressure and oxygen saturation are performed. All patients are connected to a bispectral index (BIS) monitor (Model A 2000, Aspect Medical Systems, Natick, MA, USA). Anesthesia is induced with remifentanil 0.5 μg/kg/min injected intravenously over 120 seconds (s) followed by propofol 2 - 2.5 mg/kg injected intravenously over 30 s. After loss of consciousness and ventilation via facemask with a fresh gas flow at 4 L/min (50% nitrous oxide in oxygen) control manually to maintain the end-tidal carbon dioxide (CO2) at 30 to 35 mmHg. Maintenance of anesthesia is with 1 - 1.5 minimum alveolar concentration (MAC) of sevoflurane in a gas mixture of 50% nitrous oxide in oxygen to maintain a BIS between 40 and 50 and infusion doses of remifentanil 0.05 - 0.2 μg/kg/min throughout surgery.

Core body temperature is measured by a thermocouple placed in the distal esophagus (DeRoyal®, DeRoyal Industries Inc., Powell, TN, USA). Core temperature is manipulated in core temperature ranges: 36.5°C and 37°C in C group and 34.5°C and 35°C in H group by surface cooling with wet towels and a fan of air conditioner. The target temperature, once achieved and stabilized, is maintained within ± 0.1°C throughout the remainder of the study. The peripheral skin temperature on the wrist is maintained more than 32°C in both groups.

Neuromuscular function is assessed using acceleromyography of the adductor pollicis muscle (TOF-Watch SX®, Organon Ltd., Dublin, Ireland). Before placing the surface electrodes, the skin overlying the ulnar nerve of the dominant hands is cleansed with isopropyl alcohol. Two electrodes (CleartrodeTM, Ref 1720-003, ConMed®, Utica, NY, USA) are placed over the prepared skin on the wrist. A force displacement transducer is attached to the thumb. No special arm board is used and no preload is applied to the thumb during the entire study procedure.