Perfusion Index in Detection of Ulnar Nerve Sparing During Supraclavicular Block

The aim of this study to evaluate the ability of perfusion index to detect ulnar sparing and to estimate the proper time for the perfusion index ratio to determine successful block.

On arrival to the operating room, patients will be connected to standard continuous monitoring; i.e. 5 lead electrocardiography (ECG), pulse oximetry, and automated non-invasive blood pressure monitoring (NIBP) every 5 minute. Two radical-7 (masimo set) devices will be connected the patient through two probes. The probes will be connected to both index and fifth digit to have a baseline reading before block performance. After block performance, PI will be continuously monitored for 30 minutes.

2-Anesthetic technique

Supraclavicular block:

Equipment and preparation:

* Ultrasound machine with linear transducer (8-14 MHz) (Siemens acusonx300, Korea).
* 5-cm, 22-gauge insulated block needle
* Sterile gloves, sterile sleeve, and gel (Or other coupling medium; e.g. Saline)
* 20 to 25 ml of 0.5% bupivacaine + 2% lidocaine in equal volumes

Patient position:

The block can be performed while the patient is in the supine, semi-sitting, with the Patient's head turned away from the side to be blocked with slight elevation of the head of the bed which is often more comfortable for the Patient and allows for better drainage and less prominence of the neck veins.

Technique:

After sterilization and local anaesthetic infiltration of skin, the linear transducer will be applied firmly above the clavicle in the coronal oblique plane to view the transverse section of the subclavian artery, pleura, first rib and brachial plexus (which is recognized as around or oval compact groups of hypo-echoic nerves, located lateral and superficial to the pulsatile subclavian artery and superior to the first rib). The 22-gauge needle will be inserted at the lateral side of the ultrasound probe using In-plane approach. The block needle will be advanced along the long axis of the transducer (from lateral to medial). The needle will be advanced towards the target nerves inferior, lateral and superficial to subclavian artery respectively. Local anesthetic solution is injected so as to cause hydro dissection of the planes around the plexus the volume of local Anesthetic used is usually between 20 to 25 ml.

Motor block will be assessed as inability to flex elbow and hand joints against gravity and will be tested for each nerve as follow Radial nerve = Push the arm by extending the forearm at the elbow against the resistance, musculocutaneous nerve = Resisting the pull of the forearm at the elbow, median nerve = Thumb and second digit pinch, ulnar nerve = Thumb and fifth digit pinch (15). Sensory block will be assessed by using piece of ice in the distribution of median, ulnar, radial and musculocutaneous nerves. This assessment will take place every 5 minutes till 30 minutes and the block will be considered failed if the patient reports pain at the examined dermatomes during assessment time which needs conversion to general anesthesia. If the patient reports no sensation in the whole upper limb apart from the dermatomes supplied by ulnar nerve, which is not relieved after local infiltration of skin by local anesthetic this will be considered ulnar nerve sparing.

The block assessment will be correlated with Masimo pulse oximetry readings during the first 30 minutes of the block.

Masimo reading of PI values will be recorded every minute (at both index and fifth digits) for 10 minutes then every 3 minutes for 7 readings.

Monitoring of HR, MAP and pulse oximetry will be recorded before the block and every 5 minutes for 30 minutes after the block, then every 15 minutes till the end of surgery.

Eligibility Criteria:
Inclusion Criteria:

* Age between 18 and 60 years and weight 60-90 kg.
* ASA physical status classification I- II
* Patients scheduled for elective upper limb surgery

Exclusion Criteria:

* • upper limb ischemia

  * Diabetic neuropathy
  * Known contraindications to regional anaesthetic techniques as coagulopathy.
  * ASA physical status class III-IV.
  * Hypovolemic patients.