Comparison of efficacy of ultrasound guided intercostobrachial nerve block (ICBN) using two different approaches in patients posted for below elbow surgery with tourniquet under brachial plexus block a prospective observational study

The intercostobrachial nerve (ICBN) is a pure sensory nerve that arises primarily from the second intercostal nerve (T2) with occasional contribution from T3. In its extra-thoracic course, the ICBN runs parallel to the axillary vein at a distance of approximately 1.5 cm in a vertical dimension and provides sensory supply to the axilla, upper medial arm, and a small area at the upper lateral chest wall.1,2

It is not a component of the brachial plexus and hence not anesthetized by brachial plexus blockade. Clinically, ICBN blockade is necessary for any surgical procedure where the surgical incision extends into the axilla, or upper medial arm and to tolerate the tourniquet.3,4(Fig 1)

Inflation of the tourniquet by closing the tourniquet to control bleeding in the surgical field after 30 to 45 minutes can lead to relatively severe pain.5Hence ICBN block is a constant accompaniment of the brachial plexus block to control tourniquet pain in below elbow upper limb surgeries. Blocking this nerve can be done by 2 methods: (1) LA injection in the nerve pathway using superficial nerve anatomy (along the axillary vein in the midaxillary line); and (2) LA injection with US guidance and thus selective ICBN blockade.4 ICBN blockade at the axilla under USG has been more often practiced than other approaches hence has enough supporting literature. 1,2,3,4 There is relative dearth of literature regarding other approaches for ICBN blockade for example over the lateral chest wall or over T2 rib. 3,4,5

We have chosen to compare two USG techniques: the distal, more common approach at the axilla studied by various authors ( Wisotzsky et al, Magazzeni et al, Samsoudi et al) (ICBN1)and  the proximal approach over the chest wall described by Thallaj et al (ICBN2) 1-4

In addition the volume used by various authors is not consistent. Also high resolution USG has provided better visualization of the nerve compared to conventional USG. 6,7,8 Thus here we intend to compare the proximal and the distal approaches with respect to analgesic efficacy, nerve visualization using conventional USG. 9-12

Research Question:

Does the ICBN 1 technique have better analgesic efficacy compared to ICBN 2 technique?

Hypothesis:

There is no significant difference in analgesic efficacy between ICBN1 and ICBN2

 Aims: To observe difference in the efficacy of USG Guided ICBN block performed by two techniques ICBN 1 and ICBN 2 in addition in to the BPB

 1.     Primary Objective:

To observe the difference in the to observe the difference in the tourniquet tolerance (VAS 0-10)

2.     Secondary Objective:

1.     Visualization of the ICBN nerve: yes or no

2.     To observe the difference in the number of needle passes,

3.     To observe the difference in the block performance time

4.     To observe the difference in the time to complete sensory anaesthesia at the T2 dermatome

5.     Quality of sensory anaesthesia measured on a scale 0-2 at the end of 20 min between the two techniques. (tested by pin prick on the medial aspect of the upper arm)

6.     Additional sedation and opioids read to tolerate the tourniquet

7.     To observe the difference time to complete sensory recovery and

8.     To note complications (nerve injury, last, block failure)

 After institutional Ethics Committee approval this study will be conducted on 42 consenting individuals satisfying the inclusion criteria and exclusion criteria. The Routine protocol is as follows: pre anaesthetic checkup as per OT protocol, written informed consent is taken. Standard ASA monitors (non-invasive cuff blood pressure, pulse oxygen saturation, and electrocardiogram) are applied and supplemental oxygen (nasal cannula at 2 L/ min) is given. Intravenous access is secured and I.V Fluid is started. Sedation in the form of Inj fentanyl 1ug/kg and 1mg/kg Inj midazolam is administered. Ultrasound-guided suitable brachial plexus block is administered. The intercostobrachial block (ICBN) is routinely performed for tourniquet placement using subcutaneous infiltration technique or one of the ultrasound guided techniques described by various authors. For this study patients who receive USG guided ICBN block using distal (ICBN 1) or proximal approach (ICBN 2) will be included .1,2,3 This will be administered by a senior anaesthetist experienced in regional anaesthesia.

After standard skin disinfection the block is performed with a portable ultrasound machine and 50- mm short-beveled stimulating needle. Suitable BPB (Axillary, supraclavicular, infraclavicular) is performed for the below elbow surgery as per the anaesthetist (10 cc 0.75% ropivacaine and 10cc 2% lignocaine with adrenaline). This is followed by USG  guided  ICBN  block using 0.25% of  ropivacaine 5 ml.

 Technique for ICBN 1**:** The ultrasound-guided ICBN block is administered as described by Wisokstzy et al, Magazenni et al and Samsoudis et al.1,2,4 Here the high-frequency probe is placed in the axilla and slid posteriorly towards the table to visualize the axillary vein and the conjoint tendon and latissimus dorsi muscle where the ICBN and possibly the medial branchial cutaneous nerve will be visualized. (Figure 2)

Technique for ICBN 2: The ultrasound guided ICBN block will be performed in accordance to the method described by Thallaj et al.3The probe is positioned at the apex of the axillary fossa to scan the axillary vein in the short axis view. The linear probe is slid proximally toward the base of the axilla, at a distance of approximately 6 cm proximal to the medial aspect of the humeral head and the axillary vein becomes deeper on the US screen and inferior to the postero-lateral border of the pectoralis major muscle (Figure 2A). The probe is then positioned slightly oblique, and the depth on the US screen is reduced for clear identification of the nerve in the cross-sectional view. At this point, the ICBN appears as a hyper-echoic oval structure surrounded by a fascial split, superior and posterior to the axillary vein, midway on an imaginary line crossing the borders of the pectoralis major and latissimus dorsi muscles as illustrated in Figure 3. Releasing the pressure applied on the US probe frequently revealed small, hypoechoic, rounded collapsible vessels anterior or posterior to the nerve.

After assessing sensory-motor block in the BPB area using a three point scale, sensory block is assessed using pin prick in the T2 dermatome using the three point scale

(0 = No Block, 1 = Partial Anesthesia, 2 = Complete Anaesthesia).

Complete sensory block in the T2 dermatome taking more than 30 min is considered block failure. Block performance time,(time from first needle entry to completion of drug injection), number of needle passes(no of needle redirections required),time to complete sensory recovery and complications(defined as vascular puncture, nerve injury/neuropathy, block failure+, local anaesthetic systemic toxicity) if any were monitored. 12-15

 P****ARAMETERS TO BE STUDIED :

1.     Visualization of the ICBN nerve Y/N

2.     To observe difference in Block performance time

3.     To observe the difference in the number of needle passes,

4.     To observe the difference in the quality of sensory anaesthesia measured on a scale 0-2 (Fig) at the end of 20 min between the two techniques.                      (tested by pin prick on the medial aspect of the upper arm)

5.     To observe the difference in the time to complete sensory anaesthesia

6.     To observe the difference in the tourniquet tolerance (VAS 0-10 )

7.     Additional sedation and opioids read to tolerate the tourniquet

8.     To note the duration of tourniquet inflation

9.     To observe vital parameters such as SBP, DBP, HR.

10. To observe the difference in time to complete sensory recovery and motor recovery

11. To note complications (nerve injury, LAST, block failure)