Anesthesia, Conduction

Surgery to remove plaque from the carotid artery in the neck requires the artery to be clamped for a period of time. In some patients this reduces blood flow to the brain enough to cause temporary symptoms, and a temporary plastic tube called a shunt has to be inserted to restore flow. When the operation is performed with the patient awake under a local anaesthetic block, doctors decide whether a shunt is needed by talking to the patient and testing the strength of the hand on the opposite side during clamping. This is called the awake neurological test. A device called a cerebral oximeter can measure the oxygen level in the front part of the brain continuously and without needles, using light shone through the forehead. It has been suggested as a way of detecting reduced brain blood flow during this operation, and would be particularly useful for patients who are asleep under general anaesthesia and cannot be tested. However, previous studies have often chosen their alarm level after looking at their own results, and have often allowed the operating team to see the oximeter readings, which makes the results appear better than they really are. In this study, 150 adults having planned carotid surgery under a local anaesthetic block will have a cerebral oximeter attached to the forehead throughout the operation. The screen will be covered so that neither the anaesthetist nor the surgeon can see the readings, and the decision to insert a shunt will be based only on the awake neurological test, exactly as it is now. The oxygen readings will be stored inside the device and examined only after the operation. The main question is how accurately a fall of 20% or more in brain oxygen level, a level chosen in advance from previous published research, identifies the patients whose awake test becomes abnormal during clamping. The second question is whether the total amount of low brain oxygen during clamping is related to confusion or stroke in the first three days after surgery, and to memory change one month later. Participants complete a short memory test before the operation and again at one month, using different versions of the test on each occasion.

Continuous adductor canal block (CACB) is becoming increasingly popular for providing postoperative analgesia following knee arthroplasties. These continuous blocks are provided through inserted nerve catheters and effectively extend the duration of analgesia, thereby reducing opioid consumption. This, in turn, helps minimize opioid-related side effects, promotes early ambulation, and supports earlier discharge. However, catheter migration remains a significant concern, as the catheter tip can become displaced from the adductor canal due to movements associated with ambulation or physiotherapy. In this study, the investigators compare the migration rates of two different techniques for CACB catheters insertion: the Interfascial plane between SArtorious muscle and FEmoral artery (ISAFE) and the Out Of Plane parallel to Saphenous nerve (OOPS) techniques. Pain scores and opioid consumption on postoperative day 1 (POD1) will also be assessed as secondary outcomes. The hypothesis is that both techniques will result in similar migration rates of CACB catheter.