Bispectral Index-guided Sedation for Flexible Bronchoscopy

It is well known that patients undergoing bronchoscopy could be less suffering and the procedures could be carried on more smoothly if the patients have adequate sedation and analgesia. The preferred sedative and analgesic drugs are Midazolam and opioid, like Alfentanil or Morphine, which were titrated according to physicians' judgment on patients' clinical responsiveness. However, due to the pharmacokinetic characteristic of midazolam while used in intravenous injection (onset time 4-6 minutes, effective time 2-4 hours), the effective onset time may be too slow for repeated injection while patients already suffered from the bronchoscopic procedure. It is also noted that when over-sedation occurred the side effects like apnea/hypopnea, hypoxemia, and hypotension could last from dozen minutes to few hours. Although events mentioned above could be handled properly under experienced medical staff, it is still very difficult to predict the oncoming events as the pharmacokinetic effect is variant individually. Ideally, it will be more safe and efficient, during invasive procedure like bronchoscope, if the sedative drug could be onset or vanish fast and the drug effect could be titrated with an objective device directly monitoring the depth of sedation or anesthesia.

Propofol is a short-acting intravenous sedative agent used for the induction of general anesthesia for children and adults; maintenance of general anesthesia; and sedation in medical contexts, such as intensive care unit (ICU) sedation for intubated, mechanically ventilated adults, and in procedures such as colonoscopy. Its mechanism of action is uncertain, but it is postulated that its primary effect may be potentiation of the Gamma-Amino Butyric Acid-A receptor, possibly by slowing the channel closing time. It has a fast onset time (1~2 minutes) but a short working duration (8~10 minutes), which vanished fast after stop administration. Bispectral Index (BIS), an non-invasive neurophysiologic monitor instrument, can transform the electroencephalogram (EEG) and electromyography of the patient to a continual numeral, ranging from 0 to 99, which provides a direct and real-time sedative depth monitor. A BIS value of 0 equals EEG silence, near 100 is the expected value in a fully awake adult, and below70 indicated the patient lose explicit memory recall but still has the ability to maintain his own vital signs.

In this study, we design a sedative technique for bronchoscopy, a BIS-guided propofol administration, to compare with the traditional sedative technique, clinical-judged midazolam administration. Through the combination of the advantages of unique pharmacokinetics of propofol and real time monitor of sedative level from BIS, we hope to provide patients undergoing bronchoscopy a more satisfied and safety sedative procedure.

Inclusion criteria

• Patients (>18 years old) requiring elective flexible bronchoscopy or Real time endobronchial ultrasound with transbronchial needle aspiration.

Exclusion criteria

• American Society of Anesthesiologists classification of physical status 4 and 5, including hepatic or renal failure, severe obstructive sleep apnea and severe chronic obstructive pulmonary disease.
• Significant Central nervous system disorders or other factors contributing to access consciousness difficultly.
• Allergic history to study drugs.
• A history of glaucoma in the midazolam arm.