General anesthesia for bronchial thermoplasty in patients with severe, persistent asthma - description of a protocol

Bronchial thermoplasty consists of controlled delivery of radiofrequency electrical energy to the bronchial wall which heats up the tissue thus reducing the amount of smooth muscle present in the airway. The result is a diminished potential for bronchoconstriction and long-lasting improvement of asthma symptoms. The treatment is divided into 3 sessions lasting approximately 1 hour, 3 weeks apart. In our centre bronchial thermoplasty is performed in the operating theatre by the pneumologist , with the patient under general anaesthesia irrespective of enrolement in this trial. Patients are premedicated with 0.5 mg of Alprazolam orally one hour before the procedure. Non-invasive monitoring consisting of pulse oxymetry, ECG , blood pressure and neuromuscular monitoring is placed and peripheral venous access is obtained on arrival in the operating room. General anaesthesia is induced with Remifentanyl 0.5 micrograms /kg/min for 5 min then 0.15-0.25 micrograms/kg/min, Lidocaine 1 mg/kg, Propofol TCI( Marsh model) for a target concentration above 2 micrograms/ml and Rocuronium 0.6 mg/kg. A laryngeal mask airway(LMA Ambu Registered Trademark AuraGain Trademark) is inserted under deep anaesthesia ,the gastric content is aspirated via the dedicated port and pressure controlled mechanical ventilation is initiated. A radial artery catheter is placed and a blood gas analysis is performed before the beginning of the procedure and then every 15 min during the thermoplasty session. Adjuncts to the anaesthesia are used in order to minimise bronchospasm and/or oedema related to the airway instrumentation: Magnesium sulphate 2g iv in 30 min, Methylprednisolone 125 mg iv and Adrenaline 0.5 mg subcutaneously after the induction of general anaesthesia. Once the area to treat is identified by fiberoptic bronchoscopy the thermoplasty electrode is guided into place via the LMA and the procedure begins. Curarisation is maintained by supplementary boluses of Rocuronium 0.15 mg/kg. Paracetamol iv 15 mg/kg, Tramadol 1 mg/kg and Alizapride 1 mg/kg are administered 30 min before the end of the procedure. Neuromuscular blockade is reversed with Sugammadex once the session is over ,Remifentanyl and Propofol infusions are stopped and the LMA is removed once spontaneous breathing is restored. The patient is monitored in the Post Anaesthesia Care Unit(PACU) for two hours before discharge to the ward. Bronchodilator aerosols are administered to control bronchospasm if present and Piritramide is titrated to control pain. Blood gas samples are analysed on arrival and at the end of the PACU stay.