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Comparing the pain control outcomes for patients undergoing total knee arthroplasty (TKA) with either: 1) adductor canal single shot injection plus placebo iPACK injection or 2) adductor canal single shot injection plus bupivacaine and dexamethasone iPACK injection.

There are two surgical approaches for TKA 1) open 2) ROSA robotic assisted. Both follow the same pain management pathway. We plan to enroll patient undergoing either surgical procedure.

This will be a single-center (UCSD), randomized blinded investigation.

Enrollment. Consenting adults undergoing TKA will be offered enrollment. Study inclusion will be proposed to eligible patients prior to surgery. If a patient desires study participation, written, informed consent will be obtained using a current UCSD IRB-approved ICF.

Preoperative Procedures. Following written, informed consent, we will record baseline anthropomorphic information (age, sex, height, and weight) that is already provided by all patients having surgery. After consenting and prior to surgery, patients will be randomized (utilizing sealed envelopes with 1:1 ratio) to either single-shot adductor canal block with sham iPACK block or single-shot adductor canal block with local anesthetic + dexamethasone iPACK block. A regional anesthesia fellow, not participating in the study, will open the sealed envelope and prepare the iPACK solution to be used accordingly.

Current Standard Care: Currently, all patients undergoing TKA receive preoperative adductor canal block as well as multimodal pain regimen managed by APS. They all receive intraoperative intraarticular injections by the surgical team. Spinal vs general anesthesia is decided at the discretion of the intraoperative anesthesiologist along with patient preferences and relevant contraindications. The only difference for subjects participating in the study (vs those not participating) will be that they will be randomized to receive an additional nerve block for posterior knee pain.

Adductor canal single shot block + Sham group: In the preoperative holding area, all subjects in this cohort will have a peripheral intravenous (IV) catheter inserted, standard noninvasive monitors applied, supplemental oxygen administered via a nasal cannula or face mask, and positioned supine. Midazolam and fentanyl (IV) will be titrated for patient comfort, while ensuring that patients remain responsive to verbal cues. The area of insertion will be cleaned with chlorhexidine gluconate and isopropyl alcohol (ChloraPrep One-Step, Medi-Flex Hospital Products, Inc., Overland Park, KS, USA). A single shot adductor canal block will be performed under ultrasound guidance with 20 mls of 0.25% ropivacaine with 1:400,000 epinephrine. A sensory level to ice will be confirmed and decided to be adequate if positive based on the discretion of the attending anesthesiologist. A Sham iPACK block will then be performed under ultrasound guidance, where 20 mls of 0.9% normal saline with 1:400,000 epi (as a vascular marker) is injected between the popliteal artery and the posterior aspect of the femoral condyle. As is standard for all TKA at our institution, all patients will additionally receive an intraoperative intraarticular injection by the surgical team of 50 mls 0.25% bupivacaine + 30 mg Ketorolac + 0.25mg epinephrine, which will occur at least 60 minutes after preoperative perineural injections.

Adductor canal single shot block + iPACK group: In the preoperative holding area, all subjects in this cohort will have a peripheral intravenous (IV) catheter inserted, standard noninvasive monitors applied, supplemental oxygen administered via a nasal cannula or face mask, and positioned supine. Midazolam and fentanyl (IV) will be titrated for patient comfort, while ensuring that patients remain responsive to verbal cues. The area of insertion will be cleaned with chlorhexidine gluconate and isopropyl alcohol (ChloraPrep One-Step, Medi-Flex Hospital Products, Inc., Overland Park, KS, USA). A single shot adductor canal block will be performed under ultrasound guidance with 20 mls of 0.25% ropivacaine with 1:400,000 epinephrine. A sensory level to ice will be confirmed and decided to be adequate if positive based on the discretion of the attending anesthesiologist. An iPACK block will then be performed under ultrasound guidance, where 20 mls of 0.25% ropivacaine with 1:400,000 epinephrine and 6mg dexamethasone is injected between the popliteal artery and the posterior aspect of the femoral condyle. As is standard for all TKA at our institution, all patients will additionally receive an intraoperative intraarticular injection by the surgical team of 50 mls 0.25% bupivacaine + 30 mg Ketorolac + 0.25mg epinephrine, which will occur at least 60 minutes after preoperative perineural injections.

Additional Postoperative Pain Interventions: Intraoperatively, spinal anesthesia versus general anesthesia will be decided at the discretion of the operating room anesthesiologist. Postoperatively, both groups will be started on the same multimodal oral regimen and followed by our anesthesiology led acute pain team.

Inclusion Criteria:

• Having total knee arthroplasty at UC San Diego
• Plan to receive single shot adductor canal injection preoperatively
• Plan to receive spinal anesthetic with or without sedation for TKA surgery

Exclusion Criteria:

• Pregnancy
• Inability to communicate with anesthesia provider and/or investigators
• Severe renal, hepatic, cardiac disease
• Chronic high-dose opioid use (defined as daily use for more than 4 weeks prior to surgery of at least the equivalent of 20 mg oxycodone)
• BMI > 45 kg/m2
• Allergy to study medications (lidocaine, bupivacaine)
• Incarceration

Care provider and investigator will know if patient received SHAM or bupivacaine iPACK, but everyone else will be blinded