![]() ![]() Altogether 20 mL of ropivacaine was injected during IPACK. As the needle was withdrawn, the rest of the ropivacaine was injected along the femur, such that 5 mL infiltrated incrementally into the area between the artery and femur, ending at the medial end of the femur. Then 5–10 mL of ropivacaine was injected to ensure adequate spread to the lateral end of the femur. The tip was positioned at the middle of the femur, near the lateral border near the periosteum. ![]() The tibial and peroneal nerves superficial to the popliteal artery were located, and when the space between the femur and popliteal artery was located, the needle was inserted in-plane in a medial to lateral direction. The anesthesiologist identified the popliteal artery at the popliteal crease and moved cephalad just beyond the femoral condyles, to where the condyles merged with the shaft of the femur. Infiltration between the popliteal artery and capsule of the posterior knee was performed using the same ultrasonic transducer mentioned above ( Figure 2). The assessment criteria for block success were shown in the outcome section. ![]() If the block failed in a patient who received this maximum concentration, the next patient did not receive a higher concentration. The maximum concentration was set at 0.5%. If, however, the block failed in the first patient, the next patient received a 0.025% higher concentration. If the block was successful in the first patient, the next patient was randomized to receive either the same ropivacaine dose (at a probability of 0.89) or a 0.025% lower dose (at a probability of 0.11). The first patient to be recruited received 20 mL 0.2% ropivacaine (AstraZeneca, London, England) for ACB and 20 mL 0.2% ropivacaine for IPACK. Drug concentration was assigned using a biased coin up-and-down sequential design, where the concentration of local anesthetic administered to a given patient depended on the previous patient’s response. This trial was a double-blind, randomized study to estimate MEC 90 for ultrasound-guided, single-injection ACB + IPACK block in patients undergoing total knee arthroplasty. Secondary outcomes were compared between patients whose blocks succeeded with those which failed. Secondary outcomes were numerical rating scale (NRS) pain scores at postoperative 24 h and 48 h, postoperative morphine consumption, and time to hospital discharge. MEC 90 was estimated by isotonic regression, and the 95% confidence interval (CI) was calculated by bootstrapping. Block success was defined as the patient did not suffer significant pain and did not receive rescue analgesia within 6 h after surgery. The primary outcome was whether the block was successful. If the block failed, the next subject received a 0.025% higher ropivacaine concentration otherwise, the next subject received either a 0.025% smaller dose (probability of 0.11) or the same dose (probability of 0.89). Before surgery, the first patient received 20 mL of 0.2% ropivacaine for ACB and again for IPACK. This double-blind, randomized dose-finding trial was based on a biased coin up-and-down sequential design, where the concentration of ropivacaine administered to a given patient depended on the previous patient’s response. All subjects Allied Health Cardiology & Cardiovascular Medicine Dentistry Emergency Medicine & Critical Care Endocrinology & Metabolism Environmental Science General Medicine Geriatrics Infectious Diseases Medico-legal Neurology Nursing Nutrition Obstetrics & Gynecology Oncology Orthopaedics & Sports Medicine Otolaryngology Palliative Medicine & Chronic Care Pediatrics Pharmacology & Toxicology Psychiatry & Psychology Public Health Pulmonary & Respiratory Medicine Radiology Research Methods & Evaluation Rheumatology Surgery Tropical Medicine Veterinary Medicine Cell Biology Clinical Biochemistry Environmental Science Life Sciences Neuroscience Pharmacology & Toxicology Biomedical Engineering Engineering & Computing Environmental Engineering Materials Science Anthropology & Archaeology Communication & Media Studies Criminology & Criminal Justice Cultural Studies Economics & Development Education Environmental Studies Ethnic Studies Family Studies Gender Studies Geography Gerontology & Aging Group Studies History Information Science Interpersonal Violence Language & Linguistics Law Management & Organization Studies Marketing & Hospitality Music Peace Studies & Conflict Resolution Philosophy Politics & International Relations Psychoanalysis Psychology & Counseling Public Administration Regional Studies Religion Research Methods & Evaluation Science & Society Studies Social Work & Social Policy Sociology Special Education Urban Studies & Planning BROWSE JOURNALS ![]()
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