[Falsely elevated-bispectral index]

We report a case of a falsely elevated-bispectral index (BIS) during a general anaesthesia combining remifentanil TCI, desflurane and nitrous oxide for an isolated-limb chemotherapy. During surgery, BIS increased and stabilized around 70, with neither residual neuromuscular blockade nor clinical sign of awareness. These high BIS values were attributed to high-electromyographic activity and electric artefacts, such as extracorporeal-circulation machine and tourniquet. At the end of the surgery, the BIS returned to expected values around 50. The patient did not complain of intraoperative recall. This case reminds us that the BIS has some limits as being sensitive to EMG or environment artefacts that should be eliminated before deepening anesthesia. To do so, a decision algorithm is proposed that may be used for all situations of surprising high BIS, taking into account the level of neuromuscular blockade, clinical response to orders and the presence of devices likely to induce electrical or mechanical artefacts.