Pulmonary Function and Interscalene Block
Condition: Shoulder Arthroscopy
Study type: Interventional

Summary: 
      The objective of our study is to compare the degree of phrenic nerve blockade after
      interscalene block using 0.1% ropivacaine or 0.2% ropivacaine. Our hypothesis is that using a
      lower concentration of local anesthetic will result in lesser degree of phrenic nerve block.
      40 patients will be enrolled. Half will receive the block with 0.1% ropivacaine and half with
      0.2% ropivacaine. Phrenic nerve and diaphragm function will be assessed by bedside spirometry
      and ultrasound visualization.
    

Detailed description: 
      Abstract Brief abstract (250 words or less) describing the study in language understandable
      to a lay person. Include brief description of the purpose, target disease/condition if
      applicable, key eligibility criteria, and main study interventions.

      The interscalene brachial plexus block is well-suited for surgical procedures of the shoulder
      and proximal humerus. A well-established hazard of the interscalene block is ipsilateral
      hemidiaphragm paresis in nearly 100% of patients secondary to phrenic nerve blockade. This
      side effect is well-tolerated in most patients; however, extreme caution should be employed
      in patients with pulmonary disease, who may experience acute pulmonary failure from
      unilateral phrenic nerve blockade and resulting hemidiaphragm paresis. This study seeks to
      determine if using a lower concentration of ropivacaine will result in less diaphragm
      dysfunction and reduction in pulmonary function than a higher concentration of the local
      anesthetic. Patients will be randomized to one of two groups--Group A and Group B. Group A
      will receive ultrasound-guided interscalene block with 20mL 0.1% ropivacaine in the
      preoperative holding area prior to induction of general anesthesia. Group B will receive
      ultrasound-guided interscalene block with 20mL 0.2% ropivacaine in the preoperative holding
      area prior to induction of general anesthesia. The primary outcome variable is the degree of
      phrenic nerve blockade as assessed by ultrasonographic evaluation of diaphragm function and
      bedside spirometry (lung function testing). Secondary outcome variables will be assessed at
      various time intervals. They include oxygen saturation measurements, oxygen requirements,
      motor strength and sensation of blocked extremity, pain scores, opioid requirements, PACU
      (Post-Anesthesia Care Unit)length of stay, and patient satisfaction and quality of recovery
      scores. We hypothesize that interscalene brachial plexus blocks performed with a lower
      concentration of ropivacaine will result in less pulmonary dysfunction without compromising
      analgesia.

      Objectives Overall objectives

        1. Primary Objective: Compare the degree of phrenic nerve blockade after ultrasound-guided
           interscalene block using either 0.1% ropivacaine or 0.2% ropivacaine

        2. Hypothesis: Using a lower concentration of local anesthetic will result in lesser degree
           of phrenic nerve blockade. Specifically, we hypothesize that outcome measures will be as
           follows for patients receiving lower concentrations of ropivacaine: 1. Less dysfunction
           of diaphragm movement, 2. PFT (Pulmonary Function Test) values drop less in lower
           concentration groups, 3. Less oxygen desaturation in PACU, 4. Less symptomatic shortness
           of breath post-block, 5. Less need for supplemental oxygen in PACU, 6. Less unplanned
           hospital admission

        3. Secondary Objective: Compare the analgesia efficacy as well as block duration between
           0.1% and 0.2% ropivacaine. Assess the quality of recovery as well as overall
           satisfaction of patients undergoing arthroscopic shoulder surgery under combined
           regional/ general anesthesia. Also compare and evaluate the presence of other
           complications that arise in the two groups Primary outcome variable(s) The primary
           outcome variable is the degree of phrenic nerve blockade as assessed by ultrasonographic
           evaluation of diaphragm function and bedside spirometry.

      Secondary outcome variable(s) Secondary outcome variables include oxygen saturation
      measurements and oxygen requirements before block performance, 20 minutes after block
      performance, and in the PACU; motor strength and sensation of affected extremity before block
      performance, 20 minutes after block performance, and in the PACU; pain scores and opioid
      requirements in the PACU and up to 72 hours post-operatively, PACU length of stay, patient
      satisfaction and quality of recovery scores 24 hours post-operatively.

      Background Describe succinctly and clearly the past findings which justify the plan for this
      project. A summary of the relevant literature in the area of interest and reports of previous
      studies should be included.

      The brachial plexus, formed by the anterior roots of the spinal nerves C5- T1 innervates the
      shoulder, axilla, and upper extremity. The roots each exit posterior to the vertebral artery
      and travel laterally in the troughs of the corresponding cervical transverse processes and
      finally join to form trunks in the posterior cervical triangle between the anterior and
      middle scalene muscles. C5 and C6 join to form the superior trunk. C7 forms the middle trunk,
      and C8 and T1 join to form the inferior trunk. The trunks pass over the first rib and under
      the clavicle in association with the subclavian artery and branch into anterior and posterior
      divisions. The posterior divisions join to form the posterior cord. The lateral cord is
      formed by the anterior divisions of the superior and middle trunks. The medial cord is formed
      by the anterior division of the inferior trunk. The cords descend into the axilla where each
      has one major branch in addition to several minor branches before becoming a terminal nerve
      of the upper extremity. Branches of the lateral and medial cord form the median nerve. A
      branch off the lateral cord becomes the musculocutaneous nerve. The posterior cord becomes
      the radial nerve and the axillary nerve. The medial cord forms the ulnar nerve as well as the
      medial brachial and medial antebrachial cutaneous nerves (1,2). Each peripheral nerve has its
      own predictable cutaneous innervation pattern which can be mapped along the upper extremity;
      furthermore knowledge of peripheral nerve and dermatomal innervation can help guide decisions
      on which regional anesthetic approach to employ for a given surgical intervention.

      The brachial plexus provides all of the motor and most of the sensory innervation to the
      shoulder except for the most cephalad cutaneous portion of the shoulder which receives
      sensory innervation from the supraclavicular nerves of the superficial cervical plexus, nerve
      roots C3-C4. It is therefore easy to understand that complete surgical anesthesia of the
      shoulder must employ a regional technique that blocks both the cervical and the brachial
      plexuses.

      The brachial plexus can be blocked along multiple anatomic levels depending on which area of
      the upper extremity the procedurist wishes to anesthetize. The preferred approach depends on
      the surgical site and the risk of complications. The interscalene brachial plexus block is
      well-suited for surgical procedures of the shoulder and proximal humerus as it blocks the
      cervical plexus (formed by the ventral rami of C1 through C4 spinal nerve roots) in addition
      to the brachial plexus, effectively anesthetizing the skin of the shoulder. It is less suited
      for surgery of the forearm or hand as incomplete blockade of the inferior trunk results in
      incomplete analgesia of ulnar nerve distribution. A well-established hazard of the
      interscalene block is ipsilateral hemidiaphragm paresis in nearly 100% of patients secondary
      to phrenic nerve blockade from spread of local anesthetic around anterior scalene muscle.
      This side effect is well-tolerated in the majority of patients; however extreme caution
      should be employed in patients with COPD (Chronic Obstructive Pulmonary Disease) or other
      pulmonary disease, who may experience acute pulmonary failure from unilateral phrenic nerve
      blockade and resulting hemidiaphragm paresis. Because the interscalene nerve block provides
      excellent post-operative pain control for shoulder surgery and may preclude the use of
      general endotracheal anesthesia which has its own inherent risks in patients with severe
      pulmonary disease, it would be helpful to establish variables in regional technique that
      affect phrenic nerve blockade.

      There are a few publications analyzing the degree of phrenic nerve blockade and diaphragmatic
      function after interscalene brachial plexus block. A detailed review of these studies has
      shown that both reduction in volume and concentration of local anesthetic are associated with
      decreased reduction in pulmonary function tests and diaphragmatic dysfunction (3,4). There
      are; however, still essential questions that remain unclear and improvements in study design
      that can be made. Specifically, the study done by Al-Kaisy et al. in 1999 which showed that
      lower concentrations of bupivacaine are associated with less reduction in pulmonary function
      and less diaphragmatic dysfunction looked at only 11 healthy volunteers. These volunteers did
      not have surgery after receiving blocks and therefore are not representative of a true
      clinical situation. In addition, the sample size of 11 is too small to draw a conclusion.
      Furthermore, this study used a nerve stimulator-based approach to interscalene brachial
      plexus blockade and therefore deposition of local anesthetic was not visualized. Without
      direct visualization of local anesthetic deposition, it is impossible to say that all blocks
      in this study were consistently performed. This lack of consistency between blocks could
      contribute to variance in outcomes. An ultrasound-guided block approach is more effective at
      maintaining consistency in block performance and may decrease variance in outcomes. Also
      Al-Kaisy et al. used bupivacaine and our study will be using ropivacaine (3).

      All subjects enrolled in this research study are not considered to receive suboptimal
      treatment. The standard of care for shoulder surgery is general anesthesia plus regional
      anesthesia if regional anesthesia is not contraindicated. Regional anesthetics are performed
      with different local anesthetics of different concentrations. In fact, if our study shows
      that a lower concentration of ropivacaine achieves the same analgesic effect with less
      diaphragmatic dysfunction, many more patients who were previously deemed to not be candidates
      for interscalene blockade due to pulmonary disease, may receive the block and receive
      superior post-operative pain control than they would have had without the block.

      Study Design Phase* Not applicable

      Design This study is a prospective, randomized, double blinded study with 40 patients.
      Patients will be randomized to one of two groups--Group A and Group B. Group A will receive
      interscalene block with 20mL 0.1% ropivacaine in the preoperative holding area prior to
      induction of general anesthesia and Group B will receive interscalene block with 20mL 0.2%
      ropivacaine in the preoperative holding area prior to induction of general anesthesia.
      Interscalene blocks will be performed under ultrasound guidance by attending
      anesthesiologists who are experienced in regional anesthesia or by resident physicians under
      the direct supervision of attending anesthesiologists with experience in regional anesthesia.
      They will be performed in accordance with standard procedure at Penn Presbyterian Medical
      Center and ambulatory surgery center. The syringes of both concentrations of ropivacaine will
      be supplied by the research investigational pharmacy.

      Study duration We plan to begin enrollment in March 2014. The enrollment of all subjects is
      projected to be completed in December 2014 with data analysis to follow. The study is
      expected to be completed by June 2015. The length of participation for each subject will be
      up to 72 hours in the post-operative period.
    

Intervention name(s): ropivacaine
Intervention type(s): Drug
Other intervention name(s): naropin
Intervention MeSH terms: Ropivacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Shoulder arthroscopy; Interscalene block; Drug concentration; 0.1% ropivacaine or 0.2% ropivacaine