Neuromuscular Blockade Improves Surgical Conditions (NISCO)

Muscle relaxants are part of a balanced anesthesia regimen. So far, evidence is given that a neuromuscular block improves intubating conditions and protects against laryngeal morbidity. The doctrine, however, that a neuromuscular block improves surgical conditions and consequently patient care, is lacking any evidence based on clinical trials.

This study, therefore, is designed to test the clinically hypothesis that a neuromuscular block improves surgical conditions. One major problem in such a setting, however, is that it is difficult to measure what "good" or "better" surgical conditions are. We therefore suggest surrogates to test the hypothesis. The primary endpoint is the postoperative patient-controlled analgesic demand for adequate pain control. The secondary endpoints are the incidence of intraoperative events reflecting muscle relaxation during anesthesia, defined as movements of limbs or the abdominal wall, or as breathing, bucking or coughing against the ventilator, the incision-to-suture-time, the surgeon's and the anesthesiologist's opinion about the operating conditions assessed by a visual analogue scale (VAS), and the postoperative pulmonary function.

We will investigate patients scheduled for elective laparoscopic cholecystectomy under general anesthesia. The study is designed to allow optimal conditions to test the hypothesis. This results in two experimental groups representing two established anesthesia regimen (n = 25 per group). Patients of the group "no NMB" are anesthetized without any muscle relaxant. Patients of the group "NMB" are anesthetized using the same drugs as the "no NMB" group but additionally receive a neuromuscular blocking agent to induce a deep neuromuscular block from induction of anesthesia until skin suture.

Anesthesia will be induced with propofol and fentanyl. Airway will be managed using a ProSeal® Laryngeal mask which allows insertion of a gastric tube. Anesthesia will be maintained with desflurane inhalation and remifentanil infusion under BIS control. The group NMB will receive rocuronium to maintain a deep neuromuscular block (T2 < 2) until the fascia is sutured. Neuromuscular block will be reversed with sugammadex. Saline boli will be applied to the patients of the group "no NMB" every 25-35 min in order to keep the anesthesiologist blinded.

Post-operatively, in 15 min intervals during their stay and before discharge from the recovery room patients' level of consciousness will be assessed, and the updated Aldrete score will be obtained. In co-operative patients a 5-s head lift test, a 5-s arm lift test, swallowing of 20 ml water, and 5-s eye opening test will be performed. To achieve pain control, a microprocessor-controlled PCA system will be used.

The patients' respiratory function will be assessed before induction of anesthesia, 5 minutes after tracheal extubation, 30 minutes later in the postanesthesia care unit, and six hours later on the ward using a portable using spirometry device.