Effect of median nerve block on the success rate of ultrasound guided radial artery cannulation in elderly patients, a randomized controlled trial

An attending anaesthesiologist would examine the patient during the preoperative visit one day prior to surgery. Informed and written consent for participation in the study will be taken in the preoperative period.

In preoperative area,all baseline vitals will be recorded. Patients will be allocated in two groups , intervention group M and control group C by computer generated algorithm. The group allocation number will be concealed in sealed opaque envelopes and a staff member not involved with the patient at any time will open the sealed envelope.

All standard ASA monitoring will be attached to the patient in the operating room. Radial artery diameter will be measured in both the groups under ultrasound guidance before arterial cannulation. All aseptic precautions will be carried out . For the control group C, radial artery cannulation will be attempted under ultrasound guidance. For the intervention group M , median nerve block will be performed under the guidance of ultrasound in the middle of forearm which is placed in supine position using 22G stimuplex needle with 5 ml of 0.5% lidocaine. Radial artery cannulation to done under ultrasound guidance after the block. The procedure is considered a success once arterial back flow is achieved. It is considered as failure if not able to cannulate in 3 attempts. Radial artery diameter 10 minutes after the block, number of attempts, cannulation time and complications related to the procedure will be recorded. Post procedure vitals will be recorded.