The Optimal Dose of Sevoflurane Via Anaconda® in Post-operative Patient Underwent Head & Neck Surgery

When patients, who need mechanical ventilation for several days after head & neck surgery, enters the ICU, the investigators induce moderate sedation (RASS -2~-3). End-tidal sevoflurane (etSEVO) concentration is adjusted to 0.5Vol% within 30 minutes. Sedation level is evaluated every 5 minutes. After 30 minutes, the investigators check that the sedation goal is achieved.

Following the up & down method, if the moderate sedation (RASS -2~-3) or the deep sedation (RASS -4~-5) is achieved at the etSEVO concentration of 0.5vol% after 30 minutes of sedation, the next patient's target etSEVO concentration is reduced to 0.4vol%. On the contrary to this, if only light sedation (RASS above -1) is achieved, the next patient's target etSEVO is increased to 0.6vol%. This process is repeated to find the appropriate etSEVO concentration at the beginning of sedation, which induces sedation of RASS -2~-3.

In retrospective analysis, the investigators compared the prospective study group with propofol intravenous sedation group.

• RASS: Richmond Agitation-Sedation Scale

Inclusion criteria

• Patients who needs sedation in the ICU for several days after head & neck surgery
• ASA class I~III
• Adult patients over 20 years old
• Patients who can read and understand the informed consent

Exclusion criteria

• Patients who do not agree to participate in the study
• Past history or Family history of malignant hyperthermia
• End stage renal disease (eGFR<30 or dialysis)
• Moderate to severe liver disease (AST, ALT > 200IU/L)
• Pregnant women
• Patients who cannot read and understand the informed consent