EditordSugammadex, a modified g-cyclodextrin, has been increasingly used for antagonising rocuronium and vecuroniuminduced neuromuscular block. 1,2 The efficacy and safety of sugammadex has been well established. 3 A recent Cochrane review noted that use of neostigmine is associated with a higher risk of adverse events compared with sugammadex (28% vs 16%, respectively). 4 The risk of significant adverse outcomes such as residual paralysis, hypersensitivity and allergic reactions, postoperative nausea and vomiting, and bradycardia was also lower with sugammadex than neostigmine. However, the incidence of serious adverse events was similar between sugammadex and neostigmine at~1%. 4 We present two cases of significant bradycardia and asystole after sugammadex administration in patients undergoing gastrointestinal endoscopic procedures with the use of carbon dioxide for bowel insufflation to highlight this significant adverse outcome. The requirement for consent was waived for both patients.The first patient was a 41-yr-old, 72 kg male with small cell carcinoma of the lung and metastases to lymph nodes, bone, lung, and peritoneum who presented with a recent onset of increasing nausea and vomiting (5 days) and difficulty in swallowing liquids more than solids. He had recently completed his chemotherapy regimen (carboplatin and pemetrexed) and palliative radiotherapy to the right scapula and spine and was started on immunotherapy (dasatinib, denosumab and nivolumab), and had been hospitalised 16 days before this admission with evidence of obstructive pneumonia; he underwent bronchoscopy, and was treated with antibiotics. He had evidence of enlarged mediastinal lymph nodes that were considered to be non-obstructive. He had severe shortness of breath on minimal exertion, and there was concern (by his primary team) about aspiration as the cause. He did not have evidence of cardiac or neurological involvement. Given his age and the absence of other cardiac risk factors, no pre-procedure cardiac tests were carried out. Computerised tomographic examination of his chest suggested non-specific patulous oesophageal dilatation in addition to consolidation of the right middle and lower lobes. Vital signs were unremarkable except for a heart rate of 108 beats min À1 . The patient was scheduled for elective endoscopic gastro-duodenoscopy. Anaesthesia was induced with propofol 100 mg, succinylcholine 70 mg, and lidocaine 50 mg i.v. After tracheal intubation, anaesthesia was maintained with sevoflurane 0.8 MAC and titrated to effect. The patient received a single dose of rocuronium 20 mg during the course of the procedure after recovery from succinylcholine. His intraoperative course was uneventful, and ventilation was adjusted to maintain normocapnia. At the end of the procedure, he had a train-offour response of 2 with stimulation of the ulnar nerve. Reversal of the neuromuscular blocking agent after reduction of sevoflurane to an expired concentration of~0.1 MAC was accomplished with sugammadex 300 mg, followed by extubation. Ap...