PARACENTESIS AND PERICARDIOCENTESIS The need for these procedures is uncommon in pediatrics, but ultrasound can be helpful in identifying the location of fluid and in avoiding injury to solid organs A phased array or curvilinear probe should be used for identifying fluid and for dynamic ultrasound guidance For paracentesis, the transducer should be placed in different parts of the abdomen in order to identify the deepest pocket of fluid For pericardiocentesis, a small footprint probe will allow better visualization between the ribs Sonographic guidance allows a transthoracic approach rather than the subxyphoid approach, which reduces the risk of injury to the liver EVALUATION OF JOINTS Ultrasound can help with the detection or exclusion of joint effusion and can also be used to guide arthrocentesis The high-frequency linear probe is used Evaluation of the hip is discussed above Ultrasound has also been used for the knee, elbow, and shoulder NERVE BLOCKS Nerve blocks may obviate the need for sedation for painful procedures, and may decrease the amount of locally injected anesthetic Ultrasound guidance for nerve blocks can help prevent accidental puncture of neighboring vasculature and can direct the needle tip to within close proximity of the desired nerve structures A linear high-frequency probe should be used Ultrasound has been used to assist with nerve blocks for the femoral nerve and the nerves of the forearm