A Randomized Study of Whether General or Regional Anesthesia for Patients Undergoing Elective Total Knee Arthroplasty Could Effect Length of Hospital Stay

Study design. The study design is consecutive and randomized. Patients with osteoarthritis scheduled for TKA at the department of orthopedic surgery, Hässleholm Hospital, Sweden, are eligible for participation in the study. Exclusion criteria are body mass index (BMI) > 35 m/kg2, prior major knee surgery to the ipsilateral knee, ongoing infection, known immunological deficiency or ASA physical status category > IV.

Randomization and blinding procedure Randomization is performed by an employee, not involved in the study, who prepared non-transparent, sealed envelopes each containing a slip of paper with descriptions of whether the patient should receive GA or NA. The randomization is computerized. On the study day a nurse, likewise not involved in the study, opens the appropriate envelope and prepared accordingly the procedures. From the point where anaesthesia is delivered both patients and staff in the operating theatre and in the recovery unit are, for obvious reasons, aware of the method of anaesthesia being used. However, once the patients leaves the recovery unit staff members assessing home readiness are blinded to group allocation.

Assessments All patients are familiarized with a horizontal visual analogue scale (VAS, [100 mm]) used for assessment of pain and PONV (0 = no symptom, 100 = worst symptom possible). Assessments of pain are made pre-operatively, upon arrival to the post-anesthesia care unit (PACU), every second hour the first day, twice a day during the remaining hospital stay and at follow-up visits 3 and 12 months after surgery. Plasma levels of troponin T (TNT) are measured three times during the first 24 postoperative hours in order to evaluate signs of myocardial ischemic events. The Short Portable Mental State Questionnaire (SPMSQ) is used to evaluate the cognitive function pre-operatively, at the discharge and at follow-up visits 3 and 12 months after surgery. Global satisfaction score is assessed with a VAS (0 = best possible satisfaction, 100 = least possible satisfaction) at follow-up visits 3 and 12 months after surgery.

Anesthesia Oral premedication, administered 1 hour before surgery, is with midazolam 2.5 mg, paracetamol 2 g, meclozine 10 mg, celecoxib 200 mg and oxycodone 10 mg. A low-volume fluid regimen is used with 1000 mL of Ringer's solution (Fresenius-Kabi AB, 751 74 Uppsala, Stockholm) and 1000 mL of glucose 2.5% during the first 24 hrs.

In the NA group an indwelling urethral catheter is inserted prior to surgery. Intrathecal anesthesia is with bupivacaine 12.5-15.0 mg, morphine 0.2 mg and clonidine 30 µg (total volume (3.2-3.7 mL). During surgery an infusion of propofol (0.8-2.5 mg/min) is used to induce a light level of sedation. At the end of surgery a mixture of ropivacaine 110 mg, epinephrine 0.5 mg and morphine 10 mg (total volume 21 mL) is injected into the peri-surgical area. The mixture is injected using a systematic technique ensuring uniform delivery of the local anaesthetic to all tissues incised, handled or instrumented during the procedure. The first 7 mL of the mixture are injected into the posterior joint capsule and both collateral ligaments after the bone cuts had been performed. After insertion of the prosthesis another 7 mL are to be injected along the borders of and into the capsule and cut quadriceps tendon, infra-patellar ligament, possible remnants of the fat pad, cruciate ligaments and the soft tissues surrounding the joint. The last 7 mL is infiltrated into the subcutaneous tissues before wound closure.