Comparison of Licorice Versus Sugar-water Gargle for Prevention of Postoperative Sore Throat and Postextubation Coughing

Sore Throat

Thoracic surgery, double-lumen endotracheal tube, intubation, extubation, sore throat, prevention of post-extubation sore throat

The investigators propose to test the hypothesis that pre-operative gargling with licorice reduces the incidence of sore throat in rest after intubation with double-lumen endotracheal tubes compared to placebo after surgery through the first four post-extubation hours.

Patients will be premedicated with up to 7.5 mg p.o. midazolam, per routine. They will be told that the study involves two different solutions for prevention of post-extubation sore throat. Patients will be randomly assigned to gargle 5 minutes before induction of general anesthesia with: 1) licorice (0.5 g); or, 2) sugar (5 g). Randomization will be based on a computer-generated table of random numbers. Licorice or sugar (placebo) will be diluted in 30 ml water and filled in a small bottle by an independent apothecary of our university. All bottles will look similar and will not be opened until just before use. Investigator and patient will be blinded to the preparation used for gargle. Patients will be asked to gargle for two minutes, but not to swallow the solution. General anesthesia will be induced with fentanyl ≈3 µg/kg, propofol ≈1.5 mg/kg, and rocuronium ≈0.6 mg/kg. Complete muscle relaxation will be confirmed by absence of palpable twitches in response to supra-maximal train-of-four stimulation of the ulnar nerve at the wrist. The trachea will then be intubated as gentle as possible. Intubation will be attempted with a Macintosh laryngoscope, but the anesthesiologists may subsequently use any other intubation equipment as necessary. Initial tube size will be 37 cm left in women and 39 cm left for men; however, other sizes can be used if clinically necessary. Endotracheal tube cuffs will be inflated with air to 20-25 mmHg as necessary to maintain an adequate seal. General anesthesia will be primarily be maintained with sevoflurane. Patients lungs will be ventilated with O2 in air, usually with an inspired oxygen fraction (FiO2) of ≈40%. However, additional oxygen will be provided as clinically necessary, especially during one-lung ventilation. End-tidal CO2 will be maintained between 32 and 35 mmHg as clinically practical. Deep of anesthesia will be monitored by using bispectral index BIS, kept between 40 and 50. Small amounts of opioid will be permitted during surgery and in preparation for extubation. At the end of surgery, an intercostal plexus block -using up to 20 ml Ropivacaine 0.1% - will be performed by the surgeons. 1000 mg paracetamol will be given intravenously ten minutes before end of surgery. Post operative pain will be treated with fractional piritramid (Dipidolor) 3 mg IV as required.

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