Challenges of performing nerve block without ultrasonography in the obese patient - A case report

Regional anesthesia is now essential to orthopedic surgery. Ultrasound, in revolutionizing the practice, has made many dependent on it so that when unavailable, performing regional anesthesia proves challenging with blind (landmark), and semi-blind (peripheral nerve stimulator) techniques almost forgotten. In certain situations recourse to a combined or innovative approach may be reasonable. We encountered a 55-year-old obese female requiring total knee joint replacement under spinal anesthesia. She complained of severe pain in the recovery room despite receipt of significant amounts of analgesia. We opted to perform a rescue femoral nerve block for pain relief. The ultrasound machine being under repair, we proceeded to perform femoral nerve block guided by a peripheral nerve stimulator. The patient's morbid obesity rendered palpation of the femoral artery as a guide to needle insertion difficult, however. To minimize needle punctures, a hand-held acoustic Doppler probe was employed to locate the femoral artery and so guide insertion of the nerve block needle connected to the peripheral nerve stimulator. This modified combined approach facilitated location of the nerve at first pass, the block providing rapid as well as sustained pain relief. Combining a hand-held acoustic Doppler probe with a peripheral nerve stimulator to safely guide needle insertion to permit successful nerve block is appropriate in a morbidly obese patient where ultrasound is unavailable. In resource limited settings application of this innovative approach may be useful.