CURES: The Effect of Deep Curarisation and Reversal With Sugammadex on Surgical Conditions and Perioperative Morbidity

Laparoscopic bariatric surgery poses special demands on the anaesthesiologist as well as the surgeon. The surgeon requires good visualisation of the operative field while the anaesthesiologist is concerned with adequate postoperative respiratory function in these morbidly obese patients. With the advent of advanced laparoscopic techniques the time span between adequate neuromuscular blockade (NMB) and adequate postoperative recovery of respiratory muscle function is growing ever shorter with an increasing risk of postoperative residual NMB.

Even minimal postoperative residual NMB with a train of four ratio (TOF) of 0.8 is associated with impaired respiratory function as witnessed in reductions of forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) in healthy volunteers. Moreover, a TOF < 0.7 correlates with increased postoperative respiratory complications due to the inability to swallow normally leading to aspiration, atelectasis and pneumonia. However, neuromuscular blocking agents not only impair respiratory function due to skeletal muscle relaxation. Also the body's response to hypoxia is impeded due to carotid body chemoreceptor suppression. Worryingly, reversal of NMB with neostigmine can lead to respiratory complications such as bronchospasm and even induce neuromuscular transmission failure in patients who already recovered from NMB.

Obese patients are at even greater risk for postoperative respiratory complications. In a recent study after bariatric surgery, 100% of patients had at least one hypoxic event (oxygen saturation <90% more then 30seconds). Restrictive ventilatory defects are clearly associated with body mass index (BMI) and obesity hypoventilation syndrome. Since respiratory failure is responsible for 11.8% of mortalities after bariatric surgery, optimal respiratory care for these patients is primordial. Optimal reversal of NMB plays an important role herein. With the advent of Sugammadex, a cyclodextrin molecule that encapsulates and inactivates rocuronium and vecuronium, rapid and dose-dependent reversal of profound NMB by high dose rocuronium is possible without the risk of impaired upper airway dilator muscle activity when given after recovery from NMB.

Furthermore, little is known about the cerebral tissue oxygen saturation (SctO2) in these morbidly obese patients during laparoscopic gastric bypass surgery. Since the unexpected finding that NMB influences hypoxic ventilatory response, more research is needed into the effect of neuromuscular blockers and their reversing agents on cerebral oxygenation. Using near infrared spectroscopy (Fore-sight®) technology absolute brain tissue oxygenation can be quantified to study these effects.

In this study we wish to investigate if a deep neuromuscular block with a continuous infusion of rocuronium titrated to a post-tetanic count (PTC) of 1-2 responses combined with reversal of NMB with sugammadex results in:

i. Improved surgical conditions for the surgeon ii. Improved post-operative respiratory function for the patients

as compared to a standard technique with an intubation dose of rocuronium and top-ups as needed to maintain a NMB with a TOF count of 1-2 and reversal of NMB with neostigmine/glycopyrrolate.

Furthermore, we wish to investigate the effect of pneumoperitoneum, and NMB with rocuronium and reversal with Sugammadex or neostigmine/glycopyrrolate on cerebral tissue oxygenation.

Inclusion criteria

• Able to give written informed consent
• American Society of Anaesthesiologists class I, II or III
• Obese or morbid obese as defined by BMI > 30 and >40 kg/m2 respectively

Exclusion criteria

• Neuromuscular disorders
• Allergies to, or contraindication for muscle relaxants, neuromuscular reversing agents, anaesthetics, narcotics
• Malignant hyperthermia
• Pregnancy or lactation
• Renal insufficiency defined as serum creatinine of 2x the upper normal limit, glomerular filtration rate < 60ml/min, urine output of < 0.5ml/kg/h for at least 6h
• Chronic obstructive pulmonary disease GOLD classification 2 or higher.
• Clinical, radiographic or laboratory findings suggesting upper or lower airway infection
• Congestive heart failure.
• Pickwick syndrome
• Psychiatric illness inhibiting cooperation with study protocol or possibly obscuring results