Antagonism Research Between Antiemetics Agents and Acetaminophen in Thyroidectomy's Post-operative Analgesia.

Antagonism Research Between Antiemetics Agents (Droperidol, Dexametasone, Ondansetron) and Acetaminophen in Thyroidectomy's Post-operative Analgesia.

The purpose of our study is to determine if there is an antagonism between drugs used in the prevention of postoperative nausea and vomiting (PONV) on the analgesia led by acetaminophen after thyroidectomy.

It was shown that there was an antagonism of the ondansetron on the analgesia led by acetaminophen in a model of nociception by electrical stimulation using the PainMatcher in healthy volunteers. Our study try to determinate if a such antagonism exist in clinical conditions : 66 patients with an Apfel-score II undergoing thyroidectomy were randomized in 3 equal groups. Each group received an antiemetic (ondansetron, droperidol or dexamethasone) at the begining of the intervention and paracetamol at the end of the intervention for the postoperative analgesia. During 2 hours in the postoperative unit, we raised : the electrical pain's threshold with the PainMatcher, the numeric pain intensity scale and the presence of nausea or vomiting. For each patients we determined the cytochrome P450 2D6 activity that should have been able to explain a diminution of ondansetron's efficiency. Paracetamol blood levels were also raised in the postoperative unit.

Inclusion Criteria:

• patients undergoing thyroidectomy without lymph node dissection
• American Society of Anesthesiologists physical status from I to III
• Apfel-score equal to 2
• informed consent signed

Exclusion Criteria:

• pregnant and breast-feeding women
• addictive disorders
• psychic diseases
• allergy or contra-indication to a drug used in the study
• presence of postoperative nausea or vomiting
• administration of glucocorticoid for protecting recurrent laryngeal nerve.
• protocol not respected
• protocol refused by the patient
• intellectual handicap