Serratus Anterior Plane Block: Sub-Serratus vs Supra-Serratus Plane Block for Pain Control in Patients Undergoing Mastectomy
Phase: PHASE4
Conditions: Pain, Post-operative
Sponsor: University of Texas Southwestern Medical Center

 
 
The University of Texas Southwestern Medical Center at Dallas 
Institutional Review Board 
 
PROJECT SUMMARY 
 
 
Principal Investigators:   
 
Anthony Machi, M.D., Assistant Professor 
Department of Anesthesiology and Pain Management 
 
J. Travis Edwards, M.D., Assistant Instructor 
Department of Anesthesiology and Pain Management 
 
 
Co-Investigators: 
Gloria Cheng, M.D., Assistant Professor 
Department of Anesthesiology and Pain Management 
 
Trenton Bryson, M.D. Assistant Professor 
Department of Anesthesiology and Pain Management 
 
Kanu Birdi, M.D. Assistant Professor 
Department of Anesthesiology and Pain Management 
 
Sandy Thammasithiboon, M.D. Assistant Professor 
Department of Anesthesiology and Pain Management 
 
Jose Garcia, M.D. Associate Professor 
Department of Anesthesiology and Pain Management 
 
Mitchell Lin, M.D., Associate Professor 
Department of Anesthesiology and Pain Management 
 
 
Title:   
Serratus Anterior Plane Block:  Sub-Serratus vs Supra-Serratus Plane Block for Pain Control in 
Patients Undergoing Breast Surgery  
 
Date: 02/24/2017 
NCT03154658 
 
Funding Source:  
UT Southwestern Department of Anesthesiology and Pain Management. 

 
 
 
 
 
1. Introduction and Purpose: 
 
The serratus anterior plane block (SAPB) is a relatively new approach to perioperative pain 
control in various thoracic and breast surgeries.  It was first described in November 2013 as a 
block in which local anesthetic is deposited within a fascial plane either below the serratus 
anterior muscle at the mid-axillary line (sub-serratus) or above the serratus anterior muscle in 
the mid-axillary line (supraserratus).  The SAPB inhibits the lateral cutaneous branches of the 
intercostal nerves, which supply sensation to the anterior and lateral chest wall2,5.  It has been 
thought that the block is a viable alternative to other regional anesthetic techniques, such as 
neuraxial, paravertebral and intercostal blocks, while maintaining a more favorable risk and 
side-effect profile comparatively2,4.  It can be particularly useful in patients undergoing 
mastectomy, which is associated with significant post-operative acute pain, which can progress 
to a chronic pain state in 25-60% of patients1.  In the initial description of the procedure, it was 
shown that deposition of local anesthetic in the sub-serratus and supra-serratus locations 
provided effective sensory blockade, but it has yet to be determined if one approach is more 
effective than the other.   
 
Specific Aim 1: To assess the difference in the intraoperative and postoperative opioid 
consumption in patients receiving a supra-serratus versus a sub-serratus approach to the SAPB. 
 
Specific Aim 2: To compare post-operative Visual Analog Scale (VAS) scores relative to baseline 
preoperative VAS scores, patient postoperative pain satisfaction scores, presence of nausea or 
vomiting, hospital length of stay, sleep duration in first 24 hours post-operation and block 
performance times in the two serratus anterior plane techniques. 
 
 
Primary Endpoint: 
• Opioid consumption during the 24 hours following placement of the serratus anterior 
plane block    
 
Secondary Endpoints: 
1. Change in immediate post-operative pain scores from their pre-operative baseline, 
stratified to type of surgery 
2. Pain scores during the first 24 hours after placement of the block, stratified to type of 
surgery 
3. Patient satisfaction with regards to their perioperative pain control during the first 24 
hours after placement of the block, stratified to type of surgery  
4. Presence of nausea or vomiting  
5. Length of stay 
6. Duration of sleep during the first post-operative night 
7. Block performance time 

 
 
 
 
 
2. Background: 
 
The serratus anterior plane block is used for postoperative pain controls in surgeries involving 
the anterolateral chest wall, including breast surgeries and thoracic surgeries located on the 
anterior or lateral portions of the chest wall2,5.  These include breast surgeries, anterolateral 
thoracotomies, pain control in multiple rib fractures, and even as an adjunct to control upper 
thoracic pain in shoulder surgeries4,6-8.  The initial description of the block by Blanco et al. 
included two possible techniques that were both effective at producing sensory blockade to the 
anterolateral chest wall.  While both were effective in volunteer patients, it was not 
determined if one approach was more effective than the other at post-operative pain control.  
The two methods, the supra-serratus approach and the sub-serratus approach to the serratus 
anterior plane block, are described below.   
 
Supra-Serratus Anterior Plane Block, adapted from Blanco et al.: 
 
The patient should be placed in the lateral position with block site facing up and the patient’s 
non-dependent arm should rest comfortably above their head to expose their lateral chest wall.  
Identify the fourth and fifth rib in the mid-axillary line.  To help identify the fourth rib, one may 
place the ultrasound probe in a sagittal plane in mid-clavicular line of the anterior chest wall 
and count down from the top.  The fourth rib may then be traced laterally to the mid-axillary 
line.  Alternatively, one can place the ultrasound probe in a sagittal plane as high in the axilla as 
possible and identify the first rib that becomes superficial.  This is generally the fourth rib.  With 
the probe still oriented in a sagittal plane at the mid-axillary line identify the ribs with 
intercostal muscles in between.  Identify the serratus anterior muscle superficial to the ribs, and 
the latissimus dorsi muscle superficial to the serratus anterior muscle.  The thoracodorsal artery 
may be used as an additional anatomical landmark to identify the plane superficial to the 
serratus anterior muscle.  This plane is usually identified at a depth of 1-2 cm in patients with 
average body habitus.   Under continuous ultrasound guidance, advance a block needle tip into 
the plane between the serratus anterior inferiorly and the latissimus dorsi superiorly.  Once in 
position, the local anesthetic may be deposited and should be visualized spreading easily across 
the superficial surface of the serratus anterior muscle.   
 
Sub-Serratus Anterior Plane Block, adapted from Blanco et al.: 
 
The patient should be placed in the lateral position with block site facing up and the patient’s 
non-dependent arm should rest comfortably above their head to expose their lateral chest wall.  
Identify the fourth rib in the mid-axillary line.  To help identify the fourth rib, one may place the 
ultrasound probe in a sagittal plane in mid-clavicular line of the anterior chest wall and count 
down from the top.  The fourth rib may then be traced laterally to the mid-axillary line.  
Alternatively, one can place the ultrasound probe in a sagittal plane as high in the axilla as 
possible and identify the first rib that becomes superficial.  This is generally the fourth rib.  With 

 
 
the probe still oriented in a sagittal plane at the mid-axillary line identify the ribs with 
intercostal muscles in between.  Identify the serratus anterior muscle superficial to the ribs, and 
the latissimus dorsi muscle superficial to the serratus anterior muscle.   Under continuous 
ultrasound guidance, advance a block needle tip into the plane below the serratus anterior and 
above the 5th rib. Once in position, the local anesthetic may be deposited and should be 
visualized spreading easily across the posterior surface of the serratus anterior muscle.   
 
3. Concise Summary of Project: 
 
This investigation will be a randomized interventional prospective study. Patients undergoing 
breast surgeries (n=66) will be randomized to evaluate two approaches to the serratus anterior 
plane block, the supra-serratus approach or the sub-serratus approach. Patients who are 
potential study candidates will be identified ahead of time by reviewing the operating room 
daily schedule using the electronic medical record (Epic).  Once potential candidates are 
identified, charts will be reviewed for initial data collection and to determine if the patient 
meets inclusion criteria and is free of exclusion criteria.  Eligible individuals may be introduced 
to the study ahead of time via phone, in the anesthesia preoperative clinic or in the Day Surgery 
Unit by anesthesiology staff or an anesthesiology research coordinator.  Early introduction of 
the research study may allow potential candidates to fully weigh their option to participate.  
Those individuals interested in participation will be contacted by study personnel to explain the 
study, discuss the risks, benefits, and alternatives of the procedures in the study and answer 
any questions they might have.   
 
Females of childbearing age who are eligible and agreeable to study participation will be 
screened for pregnancy with a urine or blood pregnancy screen the morning of surgery per 
Clements University Hospital perioperative protocols.  Exceptions to receiving the pregnancy 
test include medically confirmed menopause, or history of surgical sterilization.  Any females 
with a positive urine or blood pregnancy screen will be excluded from the study.  
 
The patient will undergo a standard anesthesia pre-operative history and physical exam, and 
the risks, benefits and alternatives of general and regional anesthesia will be discussed with the 
patient.  An informed written consent for clinical care will be obtained from the patient.  If 
SAPB is an appropriate component of the patient’s anesthetic, and the patient has consented to 
receive a SAPB, the patient will then be introduced to the study.  After discussing the study 
procedure, its risks, benefits, and alternatives, and answering all questions with the study 
candidate, an informed written consent for study participation will be obtained.   
 
Once enrolled, a patient will be randomized to one of two groups: the supra-serratus anterior 
plane block (depositing local anesthetic superficial to the serratus anterior muscle) or the sub-
serratus anterior plane block (depositing local anesthetic deep to the serratus anterior muscle).  
Randomization will be performed using a computer generated randomization program.  The 
results of the randomization will be revealed to the physician performing the block just prior to 
its performance.  The site of the block will be marked and a safety timeout will be performed 
with the block nurse, regional anesthesiologist, and patient present and participating.   

 
 
 
Once the above is completed, patients will receive a preoperative ultrasound-guided single-
injection serratus anterior plane block using either the supra-serratus or sub-serratus 
techniques according to their randomization.  The block nurse, who is blinded to the approach, 
will record the time when the timeout is performed, the “needle insertion” time when the 
block needle enters the skin, and the “block complete” time when the needle exists the skin.  If 
the block is bilateral, the block nurse will record the time when the timeout is performed, then 
will record two sets of “needle in” times and “needle out” times, one for each side.  In the case 
of a bilateral block, the same method of serratus anterior plane block will be utilized for both 
sides.   
 
After the block, the patient will proceed to surgery.  The operating room anesthesiology team 
will be notified that the patient received a serratus anterior plane block.  An appropriate 
multimodal general anesthetic targeted towards patient safety and patient comfort will be 
employed at the operating room anesthesiologist’s discretion.  Upon completion of the surgery 
and emergence from general anesthesia, the patient will be seen by study personnel in the 
Post-Anesthesia Care Unit and pain will be evaluated using a 0-10 Likert scale (0=no pain, 10= 
worst imaginable pain) about 1 hour post-operatively.  Pain will be evaluated again by study 
personnel using the same scale on post-operative day #1, about 24 hours after initial block 
placement.  If the patient is discharged home prior to the post-operative day #1 assessment, a 
phone interview will be performed 24 hours following the block to evaluate the post-operative 
day #1 scores and monitor for adverse events.  Additional pain scores will be documented in 
the electronic medical record by nursing staff per protocol, and will be available for evaluation 
by study personnel.   
 
During the intraoperative and post-operative period, the patient will continue to receive an 
appropriate multimodal analgesic regimen as necessary to adequately control their pain.  No 
pain control method will be withheld from the patient as a result of participating in the study.  
 
Patient satisfaction scores will also be used as a measure to evaluate quality of perioperative 
pain management.  These scores will be assessed on post-operative day #1 on a scale of 1 to 5 
(Poor=1, Fair=2, Good=3 Very good=4, Excellent=5). 
 
During a routine visit on post-operative day #1, the patients will also be asked for an estimate 
on duration and quality of sleep to help assess their general comfort level during their first 
post-operative night.  
 
During the routine post-operative visit, an assessment of post-operative nausea and vomiting 
will be made by asking the patient directly.  Chart review looking for post-operative antiemetic 
usage will also be evaluated to assess the presence of post-operative nausea and vomiting. 
 
The study duration will last 24 hours.  Since both types of SAPBs are performed routinely in 
clinical practice, and both have been shown to be effective, there will be no deviation from 
standard practices in the care each patient will receive.  Additionally, the decision as to whether 

 
 
or not to perform a SAPB will be made independent from the introduction of the patient to the 
study.  Therefore, the patient’s choice to receive a SAPB will not be effected by the introduction 
of the study or their desire to participate in a clinical investigation.  A multimodal intraoperative 
anesthetic technique will be employed for all patients, and post-operative pain control will be 
managed by the patient’s primary surgical team in a manner that strives for safe, yet effective, 
multimodal pain control.   
 
Billing will occur in accordance with standard practice as all procedures are in accordance with 
standard of care and best practices.  Patients will not be reimbursed for participation in the 
study.  
 
Recorded Measures: 
1. Pain scores on a 0-10 Likert scale preoperatively, in the PACU (1 hour after the surgery), 
and at post-operative day #1 (about 24 hours after the surgery).  
2. Nursing pain scores throughout the first 24 hours after block placement, rated on a 0-10 
Likert scale. 
3. Patient satisfaction with regards to post-operative pain management within the first 24 
hours. 
4. Block performance time.  For unilateral blocks, block time is equal to needle in skin to 
needle out of skin.  For bilateral blocks, block time is equal to needle in skin on first side 
to needle out of skin on second side.   
5. Opioid consumption intraoperatively, in PACU, and on the post-surgical ward for 24 
hours following completion of the block. 
6. Duration of sleep for the first post-operative night, as assessed on patient interview on 
post-operative day #1. 
7. Presence of post-operative nausea or vomiting, as assess on patient interview on post-
operative day #1. 
8. Post-operative anti-emetic usage in the first 24 hours after surgery 
9. Length of stay assessed by chart review after patient discharge 
 
Recorded personal health information includes the patient’s name, date of birth, MRN number, 
and contact number.  Demographic information such as age, height, weight, BMI, 
race/ethnicity, and gender will be recorded. Medical and surgical history including allergies, 
pre-existing medical conditions, home and inpatient medication lists, ASA classification, type of 
anesthesia, 
laboratory 
results, 
regional 
anesthesia 
techniques, 
postoperative 
pain 
management, postoperative pain scores, post-operative pain satisfaction scores and type of 
surgery will also be recorded.  
 
4. Study Procedures: 
 
• Potential subjects will be identified by reviewing the operating room daily schedule via 
the electronic medical record (EPIC) or in the anesthesia preoperative clinic.  The EMR 
will be used to prescreen potential study candidates.   

 
 
• Recruitment and consent will occur in the Anesthesia preoperative clinics or the Day 
Surgery Unit at William P. Clements Jr. University Hospital. 
• Randomization will be performed using a computer generated randomization list. 
 
• Serratus Anterior Plane Blockade: 
o The serratus anterior plane block will be performed using a linear HFL38xp 
ultrasound probe (x-Porte; SonoSite; Bothell, Washington).  The patient will be 
positioned in the lateral decubitus position with the side to be blocked facing up.  
The patient will be positioned with their arm resting comfortably above their 
head to expose their axilla and lateral chest wall.  Using the ultrasound probe 
and anatomical landmarks, the 4th and 5th ribs will be identified at the mid to 
posterior axillary line.  Superficial to the ribs at this location, the serratus 
anterior muscle will be identified.  The latissimus dorsi muscle will be identified 
in the same plane superficial to the serratus anterior.  The skin at the needle 
insertion site will be sterilized with chlorhexidine gluconate 2% an 70% isopropyl 
alcohol prep.  A skin weal of lidocaine 1% (2-5mL) will be delivered.  A short-
beveled, non-stimulated block needle (SonoTap, 21 guage), will be inserted 
through the skin wheel under continuous ultrasound guidance towards the 
target plane location (either above or below the serratus anterior muscle, 
determined by randomization).  Local anesthetic will be injected into the tissue 
plane described above.   30 mL Ropivacaine 0.35% will be used on each side for 
patients weighing over 60 kg, and 20 mL Ropivacaine 0.35% will be used on each 
side for patients weighing less than 60 kg.  The weight-adjusted difference in 
volume is employed to maintain a safe total dose of local anesthetic, while 
controlling for drug concentration.  Adequate spread of the local anesthetic will 
be confirmed with direct ultrasound visualization.   
o The decision to receive the SAPB will be made in consultation with the patient’s 
regional anesthesiology team in accordance with standard practice.  This 
decision will be made prior to and separately from the patient’s decision to 
enroll in the study.  The patient will be offered a SAPB even if they choose not to 
participate in the study.  The option to participate in the study will not be 
discussed if the patient initially declines a SAPB.  
• Follow-up visit: 
o A follow-up visit will be performed in person for inpatients or via phone for 
outpatients within 24 hours from discharge to assess for pain control, patient 
satisfaction of pain control, presence of post-operative nausea or vomiting, 
duration of sleep on the first post-operative night, and to monitor for potential 
side effects.  The follow-up interview will take approximately 10 minutes.  
• Monitoring of Adverse Events  
o Adverse events will be monitored during the 24 hour study period according to 
standard practices.  In addition to a follow-up interview 24 hours after the block 
placement, a physician will be on call during the entire 24 hour study duration to 
address any concerns.   
 

 
 
5. Sub-Study Procedures: 
N/A 
 
 
6. Criteria for Inclusion of Subjects: 
1. Adult patients age ≥ 18 years 
2. Individuals undergoing breast surgery for which the anesthetic plan includes a serratus 
anterior plane block for a mastectomy or mastectomy with tissue expander procedure .   
 
Selection for inclusion will not be based on gender, race, or socioeconomic status.  The study 
population of interest includes men and women of all races and socioeconomic status.  There 
will be no participants from vulnerable populations, such as pregnant women, children or 
prisoners.   
 
Patients can decline enrollment.  If they do so, they will still receive a peripheral nerve block for 
postoperative analgesia according to the plan determined by the anesthesia provider at the 
time of service in accordance with the patient’s wishes. 
 
7. Criteria for Exclusion of Subjects: 
1. Any known sensory deficit of the anterolateral chest wall.   
2. Any local disorder of the skin or otherwise where blockade is to be performed which 
would prevent safe performance of the block 
3. Pregnancy 
4. ASA classification greater than 3 
5. Allergy to amide local anesthetic medications  
6. Chronic pain conditions 
7. Preoperative opioid use greater than 20 oral morphine equivalents per day  
8. Any coagulation abnormality which would be a contraindication for block placement 
9. Preoperative chronic renal dysfunction requiring renal replacement therapy or a serum 
creatinine greater than 1.4 mg/dL 
10. Body mass index >50 
11. Incarceration 
12. Inability to understand study procedures including inability to understand the English 
language 
13. Inability to provide adequate informed consent 
14. Refusal to participate in the study 
 
 
8. Sources of Research Material: 
 
• Patients undergoing breast surgery   
• Information from medical records including PHI, preoperative anesthesia report, 
intraoperative anesthesia report, post-operative notes, progress notes, vital signs 

 
 
accordion, surgery transcript, medication administration record, and Acute Pain Service 
documentation. 
• Performance of serratus anterior plane block for the purpose of postoperative pain 
• Evaluation of efficacy of postoperative analgesia  
 
9. Recruitment Methods and Consenting Process: 
 
Subjects eligible for the study are all patients undergoing breast surgery in which the anesthetic 
plan includes a SAPB.  The patients who will potentially receive a SAPB will be identified in the 
preoperative anesthesia clinic or by reviewing the daily operating room schedule in EPIC.  Once 
a potential candidate is identified, the patient’s chart will be reviewed in compliance with 
HIPAA regulations to ensure they are safe candidates to receive regional anesthesia.  A member 
of the anesthesia service or the research coordinator will contact the patient during their 
preoperative anesthesia clinic appointment time, during their routine preoperative assessment 
on the day of surgery, or by phone the night before surgery to ensure that regional anesthesia 
is appropriate for their anesthetic plan and to explain the risks, benefits, and alternatives to 
receiving the SAPB.     
 
Once it has been determined that the patient is an appropriate candidate for a serratus anterior 
plane block and the patient consents to the procedure, the patient will then be introduced to 
the study.  The purpose of this study and the potential risks and benefits of the study will be 
explained to the patient.  The option to receive the SAPB without participating in the study will 
be fully explained to the patient.  The patient will be provided a copy of the consent form and 
will be provided adequate time to read the form and have any and all questions answered 
before consenting to participate in the study.  If the patient agrees to participate in the study, 
they will sign a written informed consent form using the UTSW IRB-approved informed consent 
form prior to any study procedures.  This form will be provided and signed during the patient’s 
preoperative anesthesia clinic appointment or during the pre-operative period on the day of 
surgery. 
 
10. Potential Risks: 
 
There is minimal risk to subjects by participating in this study outside of potential for loss of 
confidentiality.  Patients will have determined their desire for receiving SAPB as part of their 
anesthetic prior to enrolling in the study and as such, the patient’s do not incur increased 
medical risk by participating in the study.   
 
• Risks of serratus anterior plane blockade: 
There is a risk of bleeding or infection as a needle will enter the skin of the patient.  Although 
very rare, there is a risk of injury or damage to any surrounding tissues, including muscles and 
nerves.  There is a less than 1% risk of pneumothorax.  There is a less than 1% risk of local 
anesthetic toxicity or allergic reaction to local anesthetic.  There is a risk that the block will not 
adequately control the patient’s pain. 
 

 
 
• Risks to an Embryo, or Fetus 
Females of childbearing age will be screened for pregnancy with a urine or qualitative blood 
pregnancy screen prior to enrollment in the study.  Pregnant females will not be eligible to 
participate in the study.   
 
• Loss of Confidentiality 
While every effort will be made to maintain confidentiality of patient information, there is a risk 
of loss of confidentiality of patient information.  
 
11. Subject Safety and Data Monitoring: 
 
The patient’s vital signs will be monitored before, during and after placement of the SAPB.  Any 
adverse reaction would be quickly detected by anesthesiology staff or perioperative nurses. 
Adverse reactions will be appropriately treated immediately and placement of the block will be 
discontinued if not yet finished.  Serious adverse events will be reported to the IRB.   
 
The primary investigator will supervise all data collected.  
 
12. Procedures to Maintain Confidentiality: 
 
A numerical code will be used to refer to each patient case and all data gathered for that case 
will be associated with the numerical code.  Direct patient identifiers will not be used during 
data analysis.  A key, linking the numerical code with specific patients will be employed in order 
to review patient charts for additional study information (such as pain scores, opioid usage, 
antiemetic usage, and length of stay).  Only de-identified study data will be recorded in a 
database on an encrypted, password protected, secure server.  Once the study data has been 
gathered and analyzed, the key to the numerical coding system will be destroyed.   
 
All protected health information will be kept in a secure location with access limited to study 
investigators only. 
 
13. Potential Benefits: 
 
The study may help the medical community by determining if there are notable differences in 
the analgesic efficacy between two potential locations of the serratus anterior plane block.  This 
has the potential to improve patient pain scores and satisfaction while reducing perioperative 
opioid usage and potentially shortening length of hospital stay by avoiding adverse side effects 
of opioid consumption (such as ileus, nausea, vomiting, and confusion).  Improvement in pain 
control may also lead to improved sleep duration on the first post-operative night, which may 
further improve patient satisfaction and decrease potential for delirium or confusion.  
 
14. Biostatistics: 
 

 
 
Assuming a standard deviation of 32 units, the study will need a total sample size of 58 
(29/group) to detect a 20% difference in mean opioid consumption during the 24 hours (an 
effect size of 0.75) following placement of the serratus anterior plane block between the two 
groups.  Accepting loss of follow-up data on 10% patients, the study will randomize a total of 66 
patients on a 1:1 ratio between supra-serratus and sub-serratus block group.   
 
Continuous data will be summarized as mean ± standard deviation or median (inter-quartile 
range).  Categorical data will be summarized as frequency and percentages.  The mean levels of 
opioid consumption (in morphine-equivalent units) between the two groups will be compared 
using a two sample Student’s t-test or a Wilcoxon-Mann-Whitney (WMW) test based on 
viability of the normality assumption for the sample data.  Normality will be assessed 
graphically using normal quantile plot. Post-operative pain scores (VAS), patient satisfaction 
score, sleep duration, length of stay, and block performance times in the two groups will be 
compared similarly using either Student’s t tests or WMW tests. Proportions of incidence of 
nausea and vomiting will be compared using Fisher’s exact test.  All analyses will be done using 
SAS 9.3 (SAS Inc., Cary, NC) and statistical significance will be assessed at p < 0.05.   
 
 
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