Ultrasound-guided Blocks for Ambulatory Knee Arthroscopy

Ultrasound-guided Block of the Saphenous Nerve and Obturator Nerve, Posterior Branch, for Postoperative Pain Management After Ambulatory Knee Arthroscopy

In this study, we wish to investigate the effect of ultrasound (US) -guided block of the saphenous nerve (SN) and the posterior branch of the obturator nerve (ONP) on postoperative pain and the use of opioids (morphine-like pain medicine) in the first 24 hours following ambulatory knee arthroscopy. We wish to investigate the analgesic effect of these two blocks compared to placebo (injection of local anesthetic with known pain blocking properties compared with injection of a saline solution), when used as a supplement to conventional oral analgesics. We hypothesize that patients receiving the active treatment may experience less pain during the first 24 hours after their operation than patients receiving the placebo treatment, and possibly require less opioid analgesics, experience less opioid related side effects and have a higher function level in this period than patients receiving the placebo treatment.

Ultrasound guided block of the SN and ONP with 7.5 ml of Ropivacaine 7.5 mg/ml injected at each site, respectively, immediately prior to induction of general anesthesia. Standard postoperative analgesia with paracetamol 1 g every 6 hours and Morphine 5 mg as needed. Ondansetron or Metoclopramide as needed for nausea.

Ultrasound guided placebo block of the SN and ONP with 7.5 ml of isotonic saline solution injected at each site, respectively, immediately prior to induction of general anesthesia. Standard postoperative analgesia with paracetamol 1 g every 6 hours and Morphine 5 mg as needed. Ondansetron or Metoclopramide as needed for nausea.

VRS (Verbal Rating Scale) score 0-10 on active flexion of the knee to 45 degrees, measured at 0, ½, 1, 2, 3, 4, 6, 8, 12 and 24 hours postoperatively and analyzed by area under curve (AUC) analysis.

VRS (verbal rating score) 0-10 at rest, measured at 0, ½, 1, 2, 3, 4, 6, 8, 12 and 24 hours postoperatively and analyzed by area under curve (AUC) analysis.

VRS score 0-10, measured at 0, ½, 1, 2, 3, 4, 6, 8, 12 and 24 hours postoperatively and analyzed by area under curve (AUC) analysis.

Inclusion Criteria: Planned ambulatory knee arthroscopy, except cruciate ligament surgery American Society of Anesthesiologists (ASA) class 1-3 Exclusion Criteria: Cannot cooperate Do not speak or understand Danish Daily use of opioid analgesics Allergy towards any of the drugs used in the investigation Medicine abuse (at the investigators discretion) Alcohol abuse, as defined by the National Board of Health General anesthesia contraindicated, or the patient wants spinal anesthesia Visualization of necessary structures by ultrasound not possible, or block not possible for other technical reasons