Tizanidine and Pain After Herniorrhaphy

Age, body mass index (BMI), concomitant diseases, and the ASA physiologic state will be recorded.

Simple randomization will be accomplished with a computer-generated sequence of numbers and sealed envelopes will be used to allocate patients into 2 groups.

Patients in GroupTizanidine will receive 4 mg tizanidine per oral twice a day during the postoperative first week and the first dose will be administered 1 hour before surgery, patients in Group Placebo will receive the same treatment with a placebo pill concurrently with a standard analgesic treatment: dexketoprofen trometamol; 25 mg intravenous (iv) before the induction of anesthesia and 25 mg per oral 3 times a day-1 week and acetaminophen; 1 g iv at the end of surgery. All patients will be instructed to use acetaminophen 500 mg up to 4 times a day for rescue analgesia and to contact the hospital if they have pain despite all three medications.

Heart rate (HR), peripheral oxygen saturation (SpO2), systolic arterial pressure (SAP), diastolic arterial pressure (DAP) and mean arterial pressure (MAP), end tidal CO2 pressure (EtCO2). Baseline values will recorded.

Anesthesia induction and muscle relaxation will be standardized with 2 mg kg-1 propofol, 0.6 mg kg-1 rocuronium and 50 µg fentanyl. Anesthesia will be maintained with oxygen in nitrous oxide and desflurane. The desflurane concentration will be titrated to keep BIS between 40-60. The patients will receive 50 µg fentanyl boluses in case hemodynamic variables changed ≥30% from baseline values. Hypotension will be defined as ≥20% decrease in MAP from baseline values and will be treated with fluid boluses and/or ephedrine. Bradycardia will be defined as a heart rate <50 beat min and will be treated with atropine. All treatments will be recorded. At the end of surgery volatile anesthesia will be discontinued and the patients will be extubated according to clinical extubation criteria. The time elapsed from discontinuation of volatile anesthesia to eye opening with verbal commands will be recorded as time to emergence. The patients will be transferred to the post anesthesia care unit (PACU). The modified Aldrete score will be used to evaluate recovery in the PACU and the patients will be discharged from the PACU when the Aldrete score is ≥9 ( ). Post operative pain will be evaluated with a Visual Analogue Scale (VAS) score of 0-10 (0= no pain and 10= worst imaginable pain) at 1, 6, 12 and 24 hours postoperatively.

During the control visit 1 week after surgery total analgesic consumption and analgesic related adverse events (nausea, vomiting, dizziness…) will be evaluated. Difficulty with normal daily activity will also be evaluated during this visit with the Likert score (1. no difficulty, 2. mild difficulty, 3. difficulty, 4. severe difficulty, 5. unable to perform daily activity due to pain). Health related quality of life will also be evaluated 1 month after surgery; the Short Form (SF)-36 will be used for this purpose.

Inclusion criteria

• American Society of Anesthesiologist's physiologic state I-III patients undergoing unilateral inguinal herniorrhaphy

Exclusion criteria

• chronic pain
• bleeding disorders
• renal or hepatic insufficiency
• patients on chronic non-steroidal anti-inflammatory medications
• recurrent hernias
• emergency cases