A Warm Air Blanket Causes Intraoperative Airway Obstruction

Abstract

THE safety of the anesthetized patient is facilitated by the use of many devices, such as standard monitors, eye tapes, warm air blankets, and heat moisture exchangers (HMEs). However, this myriad of ancillary devices occasionally may complicate airway management. We report a case of a foreign body causing a potentially lethal intraoperative airway obstruction.A 32-yr-old man was brought to the operating room 1 day after a 9-m fall for repair of a tile-C left hemipelvic disruption and a closed comminuted subtrochanteric fracture of the left proximal femur. History and physical examination showed that the man weighed 100 kg, had no previous medical problems, and had a class II airway. No hemodynamic or neurovascular derangements were noted. The patient was anesthetized with thiopental, fentanyl, and rocuronium and was intubated on the first attempt with an 8.0-mm ID endotracheal tube (ETT). Mechanical ventilation was initiated, and anesthesia was maintained with a mixture of N2O in oxygen and isoflurane. A warm air blanket (Bair Hugger; Augustine Medical, Eden Prairie, MN) and an HME (Humid Vent; Lous Gilbeck AB, Upplands-Vasby, Sweden) were used to help decrease heat loss during the procedure.After reduction of the hemipelvic disruption, preparations were made to transfer the patient to a fracture table for the femur repair. Fractional inspired oxygen was increased to 1.0 for several minutes before the transfer. Then, the circuit was disconnected from the HME, which remained connected to the ETT, and the patient was moved to the fracture table. The circuit was reconnected quickly, but the patient could not undergo ventilation as evidenced by the absence of chest movement and end-tidal carbon dioxide, a peak inspiratory pressure of more than 50 cm H2O, and a tidal volume of less than 100 ml. Then, ventilation was attempted vigorously with use of the reservoir bag, without success. As oxygen saturation began to decrease, the circuit was disconnected from the ETT, and a suction catheter was advanced, showing patency of the ETT lumen. While the circuit was disconnected, it was noted that the reservoir bag did not collapse. An Ambu bag was connected immediately to the ETT, the patient underwent ventilation easily, and oxygen saturation returned to 100%.Subsequent examination of the circuit showed a piece of plastic from the warm air blanket (fig. 1) lodged in the HME. The plastic head drape apparently had become trapped between the circuit and the HME, resulting in a small piece being torn off and occluding the airway. After removal of the obstructing plastic piece, the circuit was reconnected, and surgery was resumed without further incident. Many cases of intraoperative airway obstruction have been reported in the literature. 1–5Hosking et al. 1have proposed a practical algorithm for the management of airway obstruction. The first step is for the patient to undergo manual ventilation with the reservoir bag to remove the ventilator as a source of obstruction. If ventilation is performed easily, it is likely the fault lies within the ventilator. The second step, in the event of continued obstruction, should distinguish between circuit and ETT causes. ETT obstruction can be ruled out by passing a suction catheter or by successful direct ETT ventilation. If direct ETT ventilation is successful, then the circuit comes under suspicion. When the circuit and ETT have been eliminated as causes, patient sources of resistance, such as bronchospasm, pneumothorax, or pulmonary edema must be considered. In the current case, the ETT and the patient were eliminated as causes of obstruction when ventilation was restored by direct ETT ventilation.In the current patient, disconnecting and subsequent reconnecting of the circuit trapped a piece of the warm air blanket within the HME, producing total obstruction of the airway. An HME was implicated previously in airway obstruction in an infant. In that case, a small piece of paper was caught in the HME, preventing effective ventilation. 6Various causes of airway obstruction exist in the operative environment. When an obstruction is recognized, a systematic approach to diagnosis and treatment must be implemented. Because of the wide variety of adjunct devices used by anesthesiologists, we must always be aware of the possibility of an obstructing foreign body.