Interscalene Block using stimulating Catheter

Ultrasound Guided Interscalene Catheter
Interscalene block provides analgesia for surgeries at shoulder, arm and elbow. It can be used as anesthesia for shoulder surgery.

Anatomy
Brachial plexus is formed by cervical anterior primary rami C5, 6, 7, 8 and T1. The roots of the brachial plexus are in the inter scalene groove between the anterior and middle scalene muscles at the cricoid cartilage level (C6). The interscalene groove is usually found just lateral to the lateral border of the clavicular head of the sternocleidomastoid muscle.

Patient positioning
Traditional position is to lay the patient supine with the head turned 45 degrees to the contra lateral side. In our hospital we put the patient laterally lying comfortably on the side opposite to the operation. The machine will face the patient and operator standing behind the operating shoulder side. This gives a good view and support for the operator and comfortable for patients.

Equipment
A high frequency linear probe (>10MHz)
Depth 2.5-3.5 cm
50mm short beveled needle
Nerve stimulator
Sterile preparation kit, syringes and local anaesthetic

Ultrasound scanning technique
After skin and probe preparation, start scanning the neck, from medial to lateral. You can visualize the hypo echoic trachea in the mid line and when moved laterally you can see the more hyper echoic thyroid, then the round hypo echoic carotid artery, compressible round to oval shaped hypo echoic internal jugular vein lying lateral to carotid. Superficial to the vessels will be the sternocleidomastoid muscle.Lateral to The great vessels is The anterior scalene muscle The brachial plexus is visualises in The interscalene groove between the anterior and middle scalene muscle by slight angling of the probe. Nerves in the inter scalene groovr appear as distinct round to oval hypo echoic structures.

Needling technique
In plane
After skin local anesthetic infiltration, insert a 5 cm 22G insulated block needle on the outer (lateral) end of the ultrasound probe and advance it along the long axis of the probe in the same plane as the ultra-sound beam. In this way, the needle shaft and tip can be visualized in real time at the time of needle advancement towards the target nerves. Confirm the identity of the nerves by electrical stimulation. Useful endpoints for shoulder surgery are deltoid or biceps twitches for the inter scalene block.Observe the pattern of local anesthetic spread around the target nerves in real time during injection.

Out of plane
The target nerve is aligned with the midpoint of the transducer and the needle is inserted perpendicular to the probe. The tissue and needle movement is observed while advancing towards the nerve. While advancing the needle injecting small amounts of local anaesthetic helps to track the tip of needle.

Tips
If nerve roots in the interscalene region are difficult to visualize, scan inferiorly in the supraclavicular region to identify the nerves (often seen as a bunch of “grapes”). Then move the probe superiorly above the clavicle to trace it between the scalene muscles. Phrenic nerve often lies in a plane between the sternocleidomastoid and anterior scalene .To avoid blocking we can sometimes identify it between the SCM and anterior scalenus muscle.as a small 1-1.5mm hypo echoic structure or by nerve stimulation. Avoid needling from medial to lateral while doing an in-plane technique as it may cause inadvertent damage to the phrenic nerve. Vertebral artery seen as hypo echoic round structure below C6 can be misinterpreted as nerve root. Confirmation with colour Doppler will help to avoid any accidental injection.