BIS Sensor Electrodes Can Cause Skin Lesions: Case Report

To the Editor: BIS monitoring has become increasingly popular over the past decade and has become more sophisticated with the introduction of the A-2000 monitoring system (Aspect Medical Systems, Newton, MA) which promised a more reliable monitoring system, designed to make artifact recognition easier and faster. In addition, several types of BIS sensors have been introduced, all based on the Zipprep® technology (Aspect Medical Systems; Compatible with Ag-AgCI electrodes printed on a polyester substrate with adhesive foam backing), which should be connected with better signal recognition. The manufacturer stresses the importance of the use of its specialized electrodes to optimize the signal quality, even if more simple electrodes provide the same results (1). We present a case where the BIS sensor (BIS standard, Aspect Medical Systems) caused reversible skin lesions in a patient undergoing surgery of 90 min to make the reader aware of potential side effects of the Zipprep® technology. A 38-year-old patient (58 kg, 160 cm) underwent partial mastectomy under general anesthesia to remove a malign lesion of the right breast. Prior to surgery, the patient received chemotherapy for several months with an apparent impairment of her general well being due to intermittent nausea and vomiting. She had lost her hair due to the chemotherapy. Her general physical status according to the ASA classification was grade 1 with no history of allergies or skin disease. Her skin status prior to surgery was normal, she did not wear any make-up, nor had she used any exfoliants prior to surgery; she was on tamoxifen solely. Anesthesia was induced using a continuous infusion of remifentanil 0.5 μ g/kg/min for 2 min, followed by propofol 2 mg/kg. After loss of consciousness, a laryngeal mask airway (size: 4, inflated with 30 mL of air, The Laryngeal Mask Company, LTD, Oxon, UK) was inserted facilitated by rocuronium 0.2 mg/kg. After induction, the BIS sensor was applied to the forehead in routine fashion: at the forehead and left temporal skin area with slight pressure applied for 5 s to ensure adequate contact. The impedance reading showed 2 kΩat all three monitoring sites. The first BIS reading, approximately 4 min after injection of propofol, was 38; the columns for signal quality and EMG activity showed optimal signal quality and no EMG activity, respectively. Anesthesia was maintained using remifentanil 0.15– 0.2 μ g/kg/min and sevoflurane administered to maintain a BIS of 40, positive pressure ventilation was set to maintain an end-tidal PETCO2 of 30–40 mm Hg. BIS levels stayed between 40 and 55 throughout 90 min of surgery without any trace of poor signal quality or artifacts. Recovery was rapid, spontaneous respiration returned within 3 min after the end of surgery at a BIS of 78, and the LMA airway was removed 5 min after the end of surgery with a cooperative, alert, and pain-free patient. The BIS sensor was removed in the operating theater. Immediately after removal of the sensor, round skin lesions were noted with tiny bleeding spots where the Zipprep® foam was applied (Fig. 1). The patient was transferred to the postoperative recovery room (PACU); after installation of routine monitoring in the PACU, a moisturizing cream was applied to the lesions. It was explained to the patient that the skin lesions were connected with the monitoring electrodes used during anesthesia, would be temporary and disappear soon. On the postoperative visit 24 h after surgery, all tiny bleeding areas had disappeared. The patient was discharged.Figure 1.: Skin lesions due to contact with BIS sensor. Sensor was applied for 90 min of surgery; a moisturizing cream was applied to the sites. Lesions disappeared completely within 24 h after surgery.The skin lesions were solely limited to the contact areas with the Zipprep® foam. Although the patient had no known skin disease, she had undergone chemotherapy probably making her skin more sensitive for irritation. Skin lesions have been described after different types of electrodes from simple ECG electrodes (2) to more sophisticated electrodes (3–6), including electrodes based on the Zipprep® technology (3). The clinical importance of these lesions is related to the increased use of BIS monitoring increasing the chances of occurrence. In addition, skin lesions due to BIS monitoring are highly visible since they occur on forehead or temporal area. Patients might be surprised or anxious when they wake up and have either erythematous areas or even bleeding sites in the face. Electrodes using Zipprep® technology might cause skin lesions; especially in patients with sensitive skin or skin disease, extra care should be used when these electrodes are used. Thomas M. Hemmerling, MD, DEAA

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