Expired Propofol in Low Back Surgery

Propofol Measurement in Expiration Air and Monitoring of EEG and Pain in Patients Undergoing Low Back Surgery

Edmon (BBraun, Germany) is a portable, commercially available device for measurement of propofol in exhaled air.

The study will aim at evaluating the sensitivity and specificity of such exhaled propofol values compared with plasma propofol and measures of anaesthetic and antinociceptive effect.

Elective low-back surgery patients will be induced for general intubation anesthesia with propofol and remifentanil.

After induction a 20 min period of stable propofol infusion only will be established before start of surgery. The patients will be monitored for exhaled propofol, plasma propofol (blood samples), continous frontal EEG, Bispectral Index (BIS), skin conductance, estimated (computer based) concentrations of plasma and effect site propofol, and skin conductance.

After start of surgery (with ongoing propofol and restart of remifentanil TCI) the monitoring will continue in order to explore these relationships further.

Inclusion Criteria:

• Elective patients scheduled for low-back surgery
• BMI between 20 -32 kg/m2
• ASA I-II
• Written informed concent

Exclusion Criteria:

• Contraindication to propofol TCI
• Use of psychopharmaco or neurologic disease
• Pregnancy or breast feeding