The Study of Regional Hemodynamic Changes After Specific Brachial Plexus Block by Ultrasound Guidance
Condition: Upper Limb Nerve Block
Study type: Interventional
Phase: Phase 1

Summary: 
      Phase 1 Sympathetic block leads to vasodilatation and increases in blood flow. However,
      regional hemodynamic changes of radial and ulnar artery after specific nerve block of
      brachial plexus remains unclear. The aim of the study is to assess the effect of specific
      nerve block of brachial plexus on hemodynamics of upper extremity, and provides evidence for
      further research in patient undergoing microvascular surgery.

      Phase 2 There is no literature about dose-finding studies of sympathetic block after brachial
      plexus block. Little is known regarding the relationship between concentration of local
      anaesthetic and vasodilation of upper extremity. The aim of this randomized, double-blind,
      prospective dose-response study is to determine the ED50 and ED95 of ropivacaine in
      sympathetic block of upper extremity after supraclavicular block
    

Detailed description: 
      Phase 1 Brachial plexus block (BPB) is a widely used regional anesthetic technique for upper
      limb surgery. The effect of sympathetic block of BPB can leads to vasodilatation and increase
      blood flow and skin temperature in the ipsilateral upper limb. At the level of the axillary
      region, the sympathetic nerves innervating the radial and ulnar artery travel with the
      brachial plexus, but it is unclear which specific nerve: musculocutaneous, radial, ulnar, and
      median innervates radial or ulnar artery. Radial and ulnar artery and their branches are
      common donor or recipient vessels in the vascular reconstruction surgery and their
      hemodynamic changes may affect the blood flow of vascular anastomoses in vascular
      reconstruction. Sometimes, brachial plexus could be partially blocked intentionally or
      unintentionally, with the resultant regional hemodynamic changes unclear.

      As the use of ultrasound guided peripheral nerve block getting increasingly popular,
      peripheral nerve can be blocked visually, with good accuracy and ease. It has made specific
      nerve block in the axillary region possible. Can specific nerve block increase the blood flow
      of target artery (radial or ulnar artery) and benefit microvascular surgery, or will it
      decrease the blood flow in other arteries and have a negative impact on microvascular
      surgery? In this study, the investigators will measure the hemodynamic changes of radial and
      ulnar artery after performing specific nerve blocks of the musculocutaneous, radial, ulnar,
      or median nerves respectively in patients without vascular disease. The aim is to assess the
      effect of specific nerve block on hemodynamics of upper extremity, and provided evidence for
      further research in patients undergoing microvascular surgery.

      The subjects of study are patients undergoing upper extremity operation. All patients will be
      randomized into 4 groups according to the specific nerve block (SNB) of brachial plexus:
      group MC (musculocutaneous), group UL (ulnar), group RA (radial) and group ME (median).
      Patients are randomised to the four groups by random number(generated by computer) in sealed
      envelopes. Sample randomization will be done in four groups by random-number using sealed
      envelopes. Each patient will receive allocated SNB of brachial plexus (musculocutaneous,
      radial, ulnar, or median) followed by Axillary brachial plexus block successively using
      ultrasound guidance combined neurostimulation. All nerve blocks will be performed by a single
      dedicated anesthetist. A second investigator, who is blinded to the protocol and patient
      allocation, will perform the measurements.

      Sensory blockade will be assessed by pinprick sensation (22 G needle) and compare with the
      opposite forearm/hand for normal, hypoesthesia or no sensation. Success of SNB is defined as
      only loss of sensation in the cutaneous distribution of the specific nerve (musculocutaneous,
      ulnar, radial, or median nerves) at 30min after SNB. If hypoesthesia or no sensation is
      detected in the innervation areas of any other nerve, the patient will be excluded. Success
      of BPB is defined as the absence of sensation to in all innervation areas of above four
      nerves 30min after the BPB.

      Measurement of hemodynamic parameters The ulnar artery and radial artery is located at 1 cm
      proximal to the ulnar or radial styloid process. Specific points will be located with skin
      marker to provide consistency with all measurements taken. Hemodynamic parameters will is
      measured by Pulsed-wave Doppler (PWD) ultrasound. The probe will be placed on the ventral
      wrist parallel to the long axis of the forearm without undue pressure on the artery during
      the PWD measurements. The volume gate will be positioned in the center of the arterial lumen,
      and the size of the gate will be 1/3 lumen of the artery. The angle of insonation is adjusted
      and maintained at 50-60 degrees. Once a desired PWD spectral waveform is achieved, the
      arterial hemodynamic parameters will be recorded.

      Phase 2 The subjects of study are patients undergoing upper extremity operation under
      supraclavicular brachial plexus block. All patients will be randomly assigned to receive 30ml
      ropivacaine in concentrations of 0.125%, 0.2%, 0.25%, 0.375%, 0.5%, or 0.75%. Patients are
      randomised to the four groups by random number(generated by computer) in sealed envelopes.
      All nerve blocks were performed by a single dedicated anaesthetist who remains blinded to the
      concentration of ropivacaine.

      A second investigator, who is blinded to the protocol and patient allocation, will perform
      the measurements. Another investigator, who is not present during the conduct of the BPB and
      blinded to the concentration of ropivacaine used will assess each blockade. Patient are also
      blinded.

      The brachial plexus will be visualized using a high-frequency linear ultrasound transducer in
      the supraclavicular fossa. After skin disinfection and infiltrating with 1% lidocaine, nerve
      stimulation needle will be inserted using in-line technique,and advanced among the divisions
      of brachial plexus with electric impulses (2 Hz, 0.3mA, 0.1 ms) of nerve stimulator. If
      visible contraction of the innervated muscle is elicited, the needle will be withdrawn slowly
      until the corresponding muscle contraction disappears to avoid intrafascicular puncture. The
      local anesthetic will be injected at three locations: adjacent to the superficial divisions
      of the plexus, adjacent to the middle divisions and inferior divisions. The proportion of the
      volume injected in each area is at the discretion of the expert operator according to the
      spread of local anesthetic.

      The efficacy of the block will be assessed by pinprick sensation (22 G needle) and compared
      with the opposite arm/hand for normal, hypoesthesia or no sensation. For patients with an
      ineffective block, supplementary local anesthesia will be administered according to the
      distribution of the block and site of surgery after measurement. If the patient experienced
      any pain during surgery, supplementary analgesia, sedation, or general anesthesia will be
      administered as required.

      Patient's arm is in supination. The brachial artery will be located in 2 cm proximal to the
      antecubital fossa. Hemodynamic Parameters will be measured by Pulsed-wave Doppler(PWD)
      ultrasound. The probe will be parallel the long axis of the arm without undue pressure on the
      artery during the PWD measurements. The volume gate will be positioned in the center of the
      arterial lumen, and the size of the gate will be 1/3 lumen of the artery. The angle of
      insonation will be adjusted and maintained at 50-60 degrees. Once a desired PWD spectral
      waveform is achieved, the arterial hemodynamic parameters will be recorded. The
      cross-sectional area (CSA) of the artery will be assessed with B-mode imaging. Probe should
      be as perpendicular as possible to the long axis of the artery to obtain as round an arterial
      section as possible. The image at end diastole will be chosen and measured with the cine
      loop.
    

Intervention name(s): specific nerve block; ropivacaine
Intervention type(s): Procedure; Drug
Intervention description(s): specific nerve blocks of the musculocutaneous, radial, ulnar, or median nerves at axillary region; Different concentration of ropivacaine
Other intervention name(s): Naropin
Intervention MeSH terms: Ropivacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Basic Science
Keywords: hemodynamics; anaesthetics; brachial plexus; peripheral nerves; skin temperature; sympathetic nervous system; dose-response relationship