Pharmacokinetic Profile and Dermatomal Coverage of the Erector Spinae Plane Block: a Comparison of Bolus Dosing and Continuous Infusion
Phase: PHASE4
Conditions: Pain, Postoperative, Pain, Chest
Sponsor: Virginia Commonwealth University

 
Pharmacokinetic profile and dermatomal coverage of the erector spinae plane 
block - a comparison of bolus dosing and continuous infusion 
 
Principal investigator:  Bryant Tran, M.D., Assistant Professor, Virginia Commonwealth 
University Department of Anesthesiology 
 
NCT number:  not yet available 
IRB approval date:  March 6, 2019 
Date of document:  March 7, 2019 
 
Introduction 
 
Background 
 
Muscle plane blocks are a fairly new regional anesthesia technique and are increasing in 
popularity. The most recent muscle plane block, termed the erector spinae plane (ESP) block, 
was developed to optimize pain control for thoracic surgery while minimizing the risks 
associated with paravertebral and epidural blocks.  Numerous case reports have advocated for 
its use1-4.  
  
Significance of the research 
 
In comparison to traditional neuraxial and peripheral nerve block approaches, a successful ESP 
block requires a higher volume of local anesthetic.  Therefore, the optimal volume to produce 
analgesia from an ESP block may result in a plasma local anesthetic concentration that 
approaches toxic levels.  Pharmacokinetic studies have been performed with muscle plane 
blocks, such as the quadratus lumborum block and transversus abdominus plane block5,6; 
however, the pharmacokinetic profile of the ESP block has not yet been measured or studied.  
This study will demonstrate how quickly and closely toxic levels are reached when a routine 
dose of ropivacaine is given for the ESP block and will also assess for areas of numbness created 
by the ESP block when routine doses are administered. 
 
Specific aims of the project 
 
• Create plasma ropivacaine concentration-time curves after performance of an ESP block 
via bolus and continuous infusion into the ESP compartment.  The concentration-time 
curves will include the peak serum concentration of ropivacaine (Cmax) and the time 
required to reach maximum plasma concentration (Tmax). 
• Determine the dermatomal distribution and duration of analgesia created when ESP 
block is performed via ropivacaine bolus versus continuous ropivacaine infusion. 
 
 

 
Methods 
 
Study design 
 
This study will use clinical laboratory tests to objectively measure serum ropivacaine levels after 
an erector spinae plane (ESP) block is performed on patients undergoing cardiac surgery.  
During an ESP block, ropivacaine is typically injected into a muscle plane that is deep to the 
erector spinae muscle and superficial to the transverse process of the thoracic vertebral body; 
subsequently, the ropivacaine is absorbed into the bloodstream, at which time measurements 
can be taken.  Secondary measurements will include distribution and duration of numbness 
created by the ESP block.  
 
Description of procedures 
 
The ESP block procedure - participant consent will be performed on the day of surgery by one 
of the research investigators in the pre-operative surgical unit (PSU).  Randomization is not 
required because all participants will be undergoing the same protocol.  All participants will also 
be undergoing cardiac surgery by the same surgeon.  Routine care will be performed for the 
placement of the ESP block and is described as follows: the ESP block will be performed by the 
acute pain service, which will have members that are not involved with the research.  Adequate 
block placement will be confirmed by one of the investigators via ultrasound images that are 
captured during the procedure.  The participant, who is already in a patient gown with an 
intravenous line (IV) in place, will be positioned sitting on the side of the patient bed.  Vital sign 
monitoring with pulse oximetry and blood pressure cuff will be connected.  The participant will 
be given intravenous midazolam to reduce anxiety and enhance comfort during the ESP block 
procedure.  Full aseptic precautions will be taken with personal protective equipment and 
bactericidal preparation with chlorhexidine.  An ultrasound probe will be placed lateral to the 
patient's upper back and the ideal location of medication injection will be identified on an 
ultrasound image (which is superficial to the transverse processes of the thoracic vertebral 
bodies and deep to the erector spinae muscle).  The skin will be made numb with lidocaine 
prior to insertion of a larger needle (Tuohy needle); the proceduralist will direct the Tuohy 
needle to the desired target under ultrasound guidance and 25 cc 0.25% ropivacaine will be 
delivered through that needle.  A continuous nerve catheter will then be inserted through the 
Tuohy needle to allow for continuous delivery of medication if desired.  The Tuohy needle will 
be removed, and the nerve catheter will be secured in place with adhesive dressing.  Cardiac 
surgery will require bilateral (left and right) nerve catheter placement, and therefore, upon 
completion of one side, the ESP block will be performed on the other side.  The estimated time 
needed for a bilateral ESP block procedure is 30 minutes. After the completion of the ESP block 
procedure, the participant will undergo their planned cardiac surgery procedure, which typically 
takes many hours. 
 
Initiation of continuous nerve catheter infusions (alteration of standard care) - this component 
of care will be different than routine care.  Nerve catheter infusions are typically initiated at the 
end of the surgical procedure at a concentration and rate of 0.2% ropivacaine at 8-10 cc/hr.  

 
The study protocol will direct the nerve catheter infusions to run at 1 cc/hr; this rate will allow 
the nerve catheters to remain open and patent but will not significantly interrupt or alter the 
quality of the research data collection.  The operating room team and ICU staff will be notified 
about the patient's participation in the study and will have information available regarding the 
alterations from routine practice that would be required for this study. 
 
Research protocol, part 1 - the research protocol and data collection will begin on the 
afternoon of post-operative day 1 (the day after surgery) in the cardiac surgery intensive care 
unit (CSICU).  Typically, cardiac surgery patients will be sedated and have a breathing tube in 
place until the morning of post-operative day 1.  This delayed timing of the study will allow the 
participant to stabilize after removal of the breathing tube.  Although written consent has 
already been obtained, a research investigator will obtain a verbal reaffirmation from the 
participant and update the CSICU team before proceeding.   
 
Per routine, the participant will have vital sign monitors connected and have an arterial line in 
place that will allow for collection of blood samples for laboratory testing.  The nerve catheter 
infusions will be suspended and the research protocol will begin in the CSICU as follows:  the 
investigator will administer 25 cc 0.25% ropivacaine through each nerve catheter (totaling 50 cc 
0.25% ropivacaine) and record the time of administration on a data collection sheet.  Either the 
investigator or study assistant will collect arterial blood samples at the following intervals after 
the medication bolus:  10 minutes, 15 minutes, 30 minutes, 45 minutes, 60 minutes, 90 
minutes, 2 hours, and 4 hours.  The blood samples will be labeled with a patient ID sticker and 
will also contain the study ID number and the time interval that corresponds with the blood 
sample.   The samples will be stored in a designated ice cooler that will be delivered to the 
clinical laboratory.   
 
During this first portion of sample collection, the secondary outcome of dermatomal analgesia 
and duration will be assessed.  At the 60-minute interval, a study investigator will test areas of 
numbness performing a pinprick test and using a dermatomal map to mark the areas of 
numbness.  For the pinprick test, the investigator will use a pointed object that is sharp enough 
to elicit a sharp sensation but blunt enough that it does not cause skin damage; the participant 
will be asked to provide comparison of the sensation of the pointed object when it is applied to 
an area that is not expected to be numb (like the palm) versus an area that is expected to be 
numb (like the chest and thorax).  At the 90-minute, 2 hour, and 4 hour intervals, the 
participant will be asked if the numbness from the nerve block has gone away.  If the resolution 
of numbness occurs between the time intervals, the participant will be asked to look at the 
clock and remember the time at which the difference was felt.  It is expected that at the 4-hour 
interval, the serum ropivacaine level will be approaching or have reached the baseline level 
before the bolus was given. 
 
Research protocol, part 2 - at the 4-hour interval (4 hours after the initial bolus), both nerve 
catheter infusions will be resumed at a concentration and rate of 0.2% ropivacaine at 10 cc/hr.  
Either the investigator or study assistant will collect arterial blood samples at the following 
intervals after the start of the infusion:  60 minutes, 2 hours, 4 hours, 8 hours, 12 hours, 24 

 
hours.  Dermatomal analgesia assessment will be performed by one of the research 
investigators at the 24-hour mark.  After this assessment, the research protocol will be 
considered complete and routine care by the CSICU and acute pain service will resume.  The 
researchers will collaborate with the health care teams during the study protocol if this 
becomes necessary to maintain patient safety and comfort. 
 
The collected blood samples are viable for one week if they are refrigerated and one month if 
they are frozen.  Free and total ropivacaine levels will be determined for each sample by the 
clinical laboratory and this information will be distributed to the research investigators in a way 
that protects patient health information and will be recorded securely onto a data collection 
sheet.  The data for this sheet can then be used for statistical analysis and creation of a 
pharmacokinetic profile for the ESP block (both bolus and infusion curves). 
 
Data analysis 
 
A two-sample Kolmogorov-Smirnov test will be used to determine the difference between the 
distributions of the bolus arm and the infusion arm.  Tmax and Cmax of the two arms will be 
analyzed with an unpaired t-test.  A logrank test will be used to assess the difference between 
the duration of analgesia created by the bolus arm and the infusion arm. 
 
Institutional board approval 
 
The protocol has been approved by Virginia Commonwealth University Institutional Review 
Board (Study ID HM20014803). 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
Literature cited 
 
1. 
Forero M, Adhikary SD, Lopez H, Tsui C, Chin KJ.  The erector spinae plane block: a novel 
analgesic technique in thoracic neuropathic pain.  Reg Anesth Pain Med.  2016; 41:621–7. 
 
2. 
Chin KJ, Adhikary SD, Sarwani N, Forero M.  The analgesic efficacy of pre-operative 
bilateral erector spinae plane (ESP) blocks in patients having ventral hernia repair.  Anaesthesia.  
2017; 72(4):452-460.  
 
3. 
Adhikary SD, Prasad A, Soleimani B, Chin KJ.  Continuous Erector Spinae Plane Block as 
an Effective Analgesic Option in Anticoagulated Patients After Left Ventricular Assist Device 
Implantation: A Case Series.  J Cardiothorac Vasc Anesth. 2018 Apr 12.  [Epub ahead of print]  
 
4. 
Thiruvenkatarajan V, Adhikary S, Pruett A, Forero M.  Erector spinae plane block as an 
alternative to epidural analgesia for post-operative analgesia following video-assisted 
thoracoscopic surgery: A case study and a literature review on the spread of local anaesthetic in 
the erector spinae plane.  Indian J Anaesth.  2018; 62(1):75-78. 
 
5. 
Murouchi T, Iwasaki S, Yamakage M.  Quadratus Lumborum Block: Analgesic Effects and 
Chronological Ropivacaine Concentrations After Laparoscopic Surgery.  Reg Anesth Pain Med. 
2016; 41(2):146-50. 
 
6. 
Griffiths J, Barron F, Grant S, Bjorksten A, Hebbard P, Royse C.  Plasma Ropivacaine 
Concentrations After Ultrasound-guided Transversus Abdominis Plane Block.  Br J Anaesth.  
2010; 105(6):853-6.