Can general anaesthesia provide similar results in the population in terms of pain after a total knee replacement surgery when compared to spinal anaesthesia?

Common anaesthetic techniques used for total knee arthroplasty (TKA) include general anaesthesia (GA) and neuraxial anaesthesia (NA - Spinal anaesthesia). NA is the technique of choice in many centers since many consider it provides better analgesia compared to GA. However, this is debatable in the era of modern anaesthesia. In a number of recent studies, both GA and NA techniques have shown to be equally effective, providing similar outcomes in terms of mortality and complications. Today, anaesthetists have been performing regional blocks to promote better pain relief for knee replacements. Most commonly, the adductor canal block (ACB) is performed. Local infiltrative analgesia (LIA) by the surgeons also decreases pain. We believe that the addition on ACB to both GA or NA will provide great pain relief for patients and the choice of anaesthesia (GA or NA) does not influence the outcomes. Participants: patients with osteoarthritis undergoing TKA. Patients can go either to NA or GA group depending on the randomization. Both will receive ACB and LIA and we will measure opioid consumption in the postoperative period, patients satisfaction, pain scores, nausea and vomiting episodes and anaesthetic time for each technique. Intervention Anaesthesia and operative care PREOPERATIVE Assessment: All patients will be assessed prior to the anaesthetic procedure as per normal standard in our institution. This may happen at the pre-assessment clinic or prior to the procedure. The research will be explained to the patient and informed consent obtained if his/her decision is to be involved in the study. Premedication: We usually do not give pre-medication to the patients in our institution. Anxiolytics may be given at the discretion of the anaesthetist. Midazolam as a 0.5mg incremental intravenous bolus doses will be accepted for this purpose. INTRAOPERATIVE Group NA: After inserting an intravenous cannula, patients will be positioned for the neuraxial procedure. Patients will be fully monitored according to the ANZCA (Australian and New Zealand College of Anaesthetists) recommendations. Anxiolytics may be given at the discretion of the anaesthetist. Midazolam as a 0.5mg incremental intravenous bolus doses will be accepted for this purpose. Technique: Aseptic. The spinal needle will be inserted at the interspinal level 3 to 4 or 4 to 5 (L3-L4 or L4-L5 levels). A dose of 12.5 to 15 mg (3.0 mL) of Hyperbaric Bupivacaine 0.5% will be given in the intrathecal space. After the procedure is done and tested if working properly, ACB will be performed (explained below). During the procedure, patients will receive light sedation with target-controlled infusion (TCI) of propofol 10mg.mL (Alaris® PK syringe pump) intravenously titrated to effect (with initial target effect site concentration set at 0.5 µg ml-1, gradually altered by increments to a maximum of 3.0 µg ml-1) with supplemental oxygen. Group GA: After inserting an intravenous cannula, patients will be positioned for GA. Patients will be fully monitored according to the ANZCA (Australian and New Zealand College of Anaesthetists) recommendations. TCI of propofol (using Marsh or Schnider pharmacokinetic models depending on the anaesthetist preference with a minimum target effect site concentration set at 2.5 µg ml-1, gradually altered by increments to achieve a Bispectral index below 60) and remifentanil target control intravenously (Minto pharmacokinetic model) with maximum plasma concentration of 8 mcg/ml to avoid acute tolerance to opioids (Kim D. J Anesth. 2018 Dec;32(6):886-892).The depth of anaesthesia will be monitored using BIS (Bispectral index). This will be used for both induction and maintenance of anaesthesia. The airway device used during the procedure will be defined by the anaesthetist preference. Possibilities include Laryngeal Mask Airway (LMA) or endotracheal tubes. ACB will be performed after the airway is secured. The use of muscle relaxant will be by the discretion of the anaesthetist. Local infiltration anaesthesia (LIA) by surgeons Towards the end of surgery, all subjects will receive up to 150 ml of ropivacaine (0.2%) (Depending on patient’s weight) with ketorolac 30 mg and 0.5 mg of epinephrine infiltration of local anaesthetic in the perisurgical area. The mixture will be injected after insertion of the prosthesis using a systematic technique to ensure uniform delivery of local anaesthetic to all tissues incised, handled or instrumented during the procedure. 1/2 of the volume will be injected into the posterior joint capsule and both collateral ligaments. Infiltration sites included the posterior capsule and the intercondylar area, the anterior capsule, the collateral ligaments and along the femur and tibia. The remaining volume will 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 soft tissues surrounding the joint and into the subcutaneous tissues before wound closure. Only surgeons with experience in LIA will be doing the injections. For Both NA and GA groups: All patients will receive in the surgical theatre by the intravenous route: - Cephazolin 2 grams – Prior to the surgical incision - Tranexamic acid 1g at the beginning of the operation. Another 1 g will be given in 2 hours after the first dose or it will be given by the surgeons depending on their preference - Dexamethasone 8mg IV within 1 hour after the incision - Ondasentron 4mg IV at the end of the procedure - Paracetamol 2g for males and 1.5gr for females within 1 hour after the incision - Parecoxib 40mg within 1 hour after the incision - 10 mg of oxycodone at the end of the procedure (skin sutures) Adductor Canal Block This will be performed for all the patients in the research prior to the surgery starts. For the NA group, this will be done after the spinal procedure and for the GA group, this will be done after the patient is anaesthetized. Procedure: At the midthigh level, approximately halfway between the superior anterior iliac spine and the patella, a dynamic scan with a high-frequency linear array transducer will used to identify the superficial femoral artery (SFA) deep to the medial third of the sartorius muscle in a transverse cross-sectional view. After identification of the appropriate location, experienced anaesthetists will inject local anaesthetic (20 mL of Ropivacaine 0.375% ) with a 22- gauge spinal needle using an in-plane ultrasound technique. Local Anaesthetic Toxicity A maximum dose of 3mg.Kg of Ropivacaine will be allowed to be used in a patient. This will be calculated by the sum of the doses given by surgeons and anaesthetists. In all procedures, surgeons will be informed the maximum volume they can use in the patient. A recent research showed that serum concentration of ropivacaine after LIA using 270 mg ropivacaine with and without an additional 100 mg perineural ropivacaine (ACB) remained well below the toxicity threshold of 3.0 µg/mL at all time points (Koniuch KL. Regional Anesthesia & Pain Medicine Published Online First: 11 January 2019. doi: 10.1136/rapm-2018-100043). C. Postoperative In the postoperative unit, ACB will be tested by an experienced anaesthetist for loss of sensation to cold in the saphenous area. Post-operative prescribed analgesia and follow up: - All patients are followed by the acute pain service (APS) in our hospital after any regional block. Therefore, all the participants in the research will have a similar treatment as any other patient would. The APS team follow up patients until they have adequate pain control with oral medications and the block has regressed completely. To assess our primary outcome, participants will have intravenous opioids for a minimum of 36 hours and therefore, the APS service will follow them all for a minimum period of 36 hours. Since the research follow up is only for 36h, the continuation of the APS for the participant will depend on the APS decision based on the above criteria. Regular medications prescribed for all the patients during their entire length of stay in the hospital - Oral ibuprofen 400 mg 8 hourly (First dose 12h after parecoxib) - Oral acetaminophen 1g 6-hourly (First dose 6h after first dose) Pro Re Nata (PRN) medications: - Morphine PCA intravenously Settings - Bolus: 1 mg; Lockout: 5 minutes Maximum dose per hour: 12 mg. Morphine PCA can be removed only after 36h after the patient arrives in the post-anaesthetic care unit (PACU). The maintenance of this medication or the decision to stop it and prescribe another one will be by the discretion of the APS team. - Oral ondasentron 4 mg every 8 hours. This will be prescribed for all the patients during their entire length of stay in the hospital Monitoring fidelity of intervention All the intervention done in the perioperative period in our patients will be charted in their anaesthetic record as per usual practice. This will make easy to find if the intervention was followed properly during the patient’s study period.