Postoperative analgesia for elective total knee arthroplasty

Patients scheduled for TKA under spinal anesthesia enrolled during preoperative anesthesia consultation. Written informed consent obtained from all patients willing to participate in this study. All patients will receive subarachnoid anesthesia in the sitting position at L3–4 or L4–5 interspace, with a 25-gauge Whitacre needle. We administer 0.5% hyperbaric bupivacaine (Hyperbaric bupivacaine 0.5% 'Registered Trademark', Braun) according to the following formula: bupivacaine (mg) = height (cm) x 0.07, with morphine (Morphine 0.1% 'Registered Trademark',, Braun) 0.15 mg and fentanyl (Fentanest 'Registered Trademark', Kern Pharma) 15 microg. Following injection, patients are immediately kept on lateral decubitus for 6 minutes to improve analgesia. There are 10 groups: - control group (without additional blocks). - epidural analgesia group (the subarachnoid anesthesia in these patients will be performed through the epidural needle at L3-4 or L4-5, the catheter advanced 3-4 cm and levobupivacaine (Chirocane 'Registered Trademark', Abbvie) 0.1% + fentanyl 2 microg.mL-1 (infusion rate 6-10 mL.h-1, bolus volume 5 mL, lock interval 30 min). Epidural infusion is started at the end of surgery. - femoral nerve block with 20 ml of levobupivacaine 0.375%, performed 7-10 minutes after spinal anesthesia, when the patient is placed supine again. - femoral block with 20 ml of levobupivacaine 0.375% and dexamethasone (Fortecortin 'Registered Trademark', Merck) 4 mg, performed 7-10 minutes after spinal anesthesia, when the patient is placed supine again. - femoral block with 20 ml of levobupivacaine 0.375% and dexmedetomidine (Dexdor 'Registered Trademark', Orionpharma) 100 microg, performed 7-10 minutes after spinal anesthesia, when the patient is placed supine again. - femoral block with 20 ml of levobupivacaine 0.375% and buprenorphine (Buprex 'Registered Trademark', Schering-Plough) 150 microg, performed 7-10 minutes after spinal anesthesia, when the patient is placed supine again. - adductor canal block with 30 ml of levobupivacaine 0.375%, performed 7-10 minutes after spinal anesthesia, when the patient is placed supine again. - adductor canal block with 30 ml of levobupivacaine 0.375% and dexamethasone 4 mg, performed 7-10 minutes after spinal anesthesia, when the patient is placed supine again. - adductor canal block with 30 ml of levobupivacaine 0.375% and dexmedetomidine (Dexdor 'Registered Trademark', Orionpharma) 100 microg, performed 7-10 minutes after spinal anesthesia, when the patient is placed supine again. - adductor canal block with 30 ml of levobupivacaine 0.375% and buprenorphine (Buprex 'Registered Trademark', Schering-Plough) 150 microg, performed 7-10 minutes after spinal anesthesia, when the patient is placed supine again. Surgeons and anesthesiologists are blinded to the addition of dexamethasone, dexmedetomidine or buprenorphine (perineural medication is prepared by a nurse adding 4 mg of dexamethasone, 100 microg of dexmedetomidine, 150 microg of buprenorphine or 1 ml of saline according to the randomized protocol). Nerve blocks are single-shots techniques performed under both ultrasound and nerve stimulation (considered adequate at 0.2-0.5 mA) by experienced anesthesiologists. All patients receive a standardized postoperative IV treatment: metamizole magnesium 8g/24 h, dexketoprofen 50 mg/12h. Postoperative analgesia begins immediately at the end of the surgery, when the patient is admitted to the PACU. The primary outcome, pain, is measured every hour (respecting the sleep period) during 24 h using a verbal rating 11–point scale for patient self-reporting of pain (VRS-11) previously explained to the patients: from 0 (“no pain”) to 10 (“the most horrible pain you can imagine; such as being burned alive”), and they are also advised to notify their nurse if they feel pain. Rescue analgesia when needed include: 1st: paracetamol 1 g, maximum 1g/6h/IV 2nd: Morphine 2 mg/15 min, maximum 10 mg/4h/IV Rescue blocks: femoral, sciatic and epidural