Assessment of the C8 Dermatomal Block with Photoplethysmographic Amplitude After Interscalene Brachial Plexus Block

Objective Assessment of Extent of Anesthesia in the 8th Cervical Dermatome Using Photoplethysmographic Amplitude in Patients Undergoing Interscalene Brachial Plexus Block

The goal of this clinical trial is to investigate the effectiveness of photoplethysmographic amplitude in assessing the extent of anesthesia in the 8th cervical dermatome in patients undergoing interscalene brachial plexus block (ISBPB). The main question it aims to answer is

• Is there any difference in the post-block changes in photoplethysmographic amplitude measured from the ipsilateral 5th finger (supplied by the 8th cervical nerve root) between ISBPBs targeting the C5-to-C6 nerve roots and the C5-to-C8 nerve roots?
• Do the changes in photoplethysmographic amplitude represent the extent of anesthesia in the 8th cervical dermatome? Participants will receive either ISBPB targeting the C5-to-C6 nerve roots or the C5-to-C8 nerve roots, and then the changes in photoplethysmographic amplitude will be measured from the 5th finger ipsilateral to ISBPB.

Inclusion Criteria:

• American Society of Anesthesiologists physical status 1 or 2
• Schedule to receive interscalene brachial plexus block for arthroscopic shoulder surgery

Exclusion Criteria:

• Coagulopathy
• Peripheral vascular diseases
• Arrhythmias
• Cardiac conduction abnormalities
• A history of medication affecting cardiac conduction
• Ischemic heart disease
• Hypertension
• Diabetes mellitus
• Thyroid dysfunction
• Other medical conditions affecting autonomic nervous activity
• Infection at the skin area for interscalene brachial plexus block
• Peripheral neuropathy or neurologic sequelae in the upper limb ipsilateral to the surgery
• Allergy to local anesthetics or a history of allergic shock
• Contralateral vocal cord palsy, hemidiaphragmatic paresis/paralysis or pneumo/hemo thorax
• Severe restrictive pulmonary disorder
• Electrolyte imbalance
• Difficulty in communicating with medical personnel
• Patients refusal