Prevention of Post Herpetic Neuralgia by Ultrasound Guided Single Nerve Block in the Emergency Department
Conditions: Pain
Sponsor: Antonios Likourezos

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Title: Prevention of Post Herpetic Neuralgia by Ultrasound Guided Single Nerve Block in the 
Emergency Department 
 
 
 
 
NCT:   
04530162 
 
 
 
 
Date:   
August 31, 2021 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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Prevention of Post Herpetic Neuralgia by Ultrasound Guided Single Nerve Block in the 
Emergency Department 
 
I. Introduction 
Herpes zoster causes significant morbidity on over 1 million Americans every year.[1]  
Although the majority of herpes zoster pain will self-resolve within one week, a significant 
proportion of patients will develop postherpetic neuralgia (PHN), which is characterized by 
debilitating pain that persists more than three months after the initial symptoms.[2,3] Nerve blocks 
have been previously studied as a method to control herpes zoster pain in outpatient pain clinics 
and inpatient settings.  This study aims to investigate whether emergency department ultrasound 
guided nerve blocks can prevent PHN and effectively treat acute herpes zoster pain. 
 
II. Background and Significance 
Varicella-zoster virus causes acute herpes zoster, which causes characteristic burning 
dermatomal pain that self resolves within two to three days for most patients.  Unfortunately for 
some, the pain can persist for months after initial symptoms.[4] Pain that persists between one 
to three months is commonly classified as subacute herpetic neuralgia. Pain that persists three 
or more months after initial symptoms is classified as postherpetic neuralgia (PHN).[5] The pain 
associated with acute herpes zoster is due to hemorrhagic inflammation and fibrosis of the 
peripheral nerve, dorsal root, and dorsal root ganglion, but the mechanism of PHN is not well 
understood. It is hypothesized that the afferent neuron activity triggered by tissue damage 
causes changes in dorsal nerve roots leading to hypersensitivity and eventually spontaneous 
activity and ectopic discharges from the inured nerves and dorsal roots regardless of tissue insult. 
[6,7,8] 
Over 200,000 cases of herpes zoster are managed in the emergency room every year in 
the United States and up to 43% of these patients may develop PHN.[2,3, 14] Of all patients with 
acute herpes zoster, 10% will require 3 or more follow-up visits for pain management causing 
significant burden on the medical system.[9] Herpes zoster pain can be chronic and intractable, 
and can significantly decrease a patient’s perceived quality of life which in some cases can lead 
to depression and even suicide.[10] Commonly, the initial presentation occurs in the emergency 
department; thus, it is paramount for an emergency room physician to adequately manage the 
acute pain of herpes zoster. However, herpes zoster pain can be difficult to control. In addition, 
it is unknown if any treatment modality can minimize the risk of PHN. Current treatment 
modalities including antivirals, anticonvulsants, oral corticosteroids, and opioids have not shown 
to be prevent postherpetic neuralgia.[11] 
In outpatient pain clinics and inpatient settings, ultrasound guided nerve blocks using 
local anesthetics and corticosteroids have been shown to effectively treat acute herpes zoster 
pain.  Several studies have found that patients who received nerve blocks for acute herpes zoster 
had a reduced incidence of PHN at 3 months.[12-16] Local anesthetics reduce afferent neuron 
activity preventing dorsal root automaticity while steroids decrease vasogenic edema reducing 
tissue damage.[14] Ultrasound guided nerve blocks have become a widespread method of pain 
management in the emergency department for various clinical scenarios. The purpose of this 
study is to investigate the efficacy of utilizing ultrasound guided nerve blocks in preventing PHN 
in the emergency department and managing acute herpes zoster pain. 

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III. Study Objectives  
The goal of this study is to evaluate the rate of PHN development in emergency 
department patients who receive ultrasound guided nerve blocks using bupivacaine and 
dexamethasone for acute herpes zoster. We will also study the effectiveness of the block in 
managing acute herpes zoster pain. The primary outcome is the percentage of patients who have 
significant herpetic pain at 1 month and 3 months after receiving the nerve block. Secondary 
outcomes measured are pain scores at 1 hour, 1 month, and 3 months post-nerve block. The 
amount of opioids used after discharge as well as the number of return visits for herpetic pain 
will also be recorded. 
 
IV. Hypothesis 
Our hypothesis is that patients who receive nerve blocks will decrease the occurrence of 
PHN development at 1 month and 3 months post-treatment. Our secondary hypothesis is that 
nerve blocks will decrease pain scores at 1 hour, 1 month, 3 months, as well as reduce the amount 
of opioids used and number of return visits for herpetic pain. 
 
V. Study Design 
This study will be a single center prospective observational study that will be conducted 
in the emergency department of an urban hospital center. A trained emergency medicine 
physician will screen and assess the patient for eligibility. Once the patient is determined to be 
eligible, informed consent will be obtained. A trained EM physician will then administer a nerve 
block using bupivacaine and dexamethasone to a patient with acute herpes zoster. The patient 
will be started on Acyclovir 800 mg five times daily for seven days. For mild to moderate 
breakthrough pain, the patient will be prescribed a 5-day course of Tylenol 650 mg and Ibuprofen 
400 mg taken up to every 8 hours together.  For severe breakthrough pain, the patients will be 
prescribed a two-day course of 7.5 mg morphine sulfate immediate release to be taken up to 
every 6 hours. The location of the nerve block and dosage of injected medications will depend on 
the distribution of the affected dermatome. The dermatomal distributions with their associated 
nerve blocks and medication dosages are shown the table below.  
 
Herpes Zoster Distribution 
Nerve Block Type 
Medication 
T2-T9 
Serratus Plane  
30 mL 0.25% bupivacaine and 8 
mg Dexamethasone 
C2-C3 
Greater Occipital Nerve  
2 mL 0.25% bupivacaine and 4 
mg dexamethasone 
C3-C4 
Superficial Cervical Plexus 
10 mL 0.25% bupivacaine and 4 
mg dexamethasone 
Anterior Abdominal Wall T6 – L1 Transversus Abdominis Plane 
30 mL 0.25% bupivacaine and 8 
mg dexamethasone 
 
A numerical verbal rating scale will be used to assess the patient’s pain pre-injection and 
at 1-hour post nerve block. We will then call the patient at the 1 week, 1 month, and 3-month 

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post-nerve block time intervals to assess the patients’ pain. We will also record the number of 
follow-up visits for herpetic pain and the amount of additional pain medications used.  
 
When called the patient will be asked a series of questions: 
1. Do you continue to have pain associated with your herpes zoster infection?  
2. If so, how would you rate your pain from a scale of 0-10? 10 being the worst pain you 
have ever had in your life. 
3. About how much pain medication have you been using since the initial nerve block? How 
many doses of Ibuprofen or Tylenol per day for how many days? How many doses of 
morphine sulfate immediate release or other opioids were taken per day for how many 
days?  
4. If you used other forms of pain controllers, what were they and how often and for how 
long did you use them? 
5. Have you seen your primary care doctor, pain clinic, emergency department, or other pain 
management follow-up visits for management of your herpes pain? If so, how many visits 
have you made? 
6. What side effects have you had since the nerve block? 
 
1. Subjects:  
The study population is Maimonides Medical Center emergency department patients older than 
18 years of age presenting with acute herpes zoster patient with characteristic dermatomal 
vesicular skin lesions within 30 days of initial symptoms. 
 
2. Eligibility Criteria: 
The inclusion criteria are patient age over 18 with herpes zoster pain onset within 30 days of 
characteristic dermatomal herpes zoster rash. The exclusion criteria are allergy to bupivacaine, 
signs of infection over herpes zoster site, greater than 30 days duration of pain, pain across more 
than one dermatome and pregnant and/or breastfeeding women.  
 
3. Design: 
The primary outcome is the percentage of patients who have significant herpetic pain at 1 month 
and 3 months after receiving the nerve block. Secondary outcomes measured are pain scores 
pre-injection, and 1 hour, 1 month, and 3 months post-nerve block. The number of tablets of 
opioids and other analgesics used after discharge as well as the number of return visits for 
herpetic pain will also be recorded. 
 
4. Data Collection Procedures: 
The numerical verbal rating scale pain score will be recorded by a research staff member at 1 
hour after administration of nerve block.  The patients will then be called at 1 week, 1 month, 
and 3 months post nerve block for assessment of NRS as well as number of follow-up visits and 
amount of analgesics used. A medication track form/log will be given to the patients to help 
record the amount of medications taken in the first week. The patients will be stratified by age: 
those under 50, 50-59, 60-69, and 70 and older as well as herpes zoster vaccination status.   
 

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5. Sample Size: 
Earlier studies show the incidence of post herpetic neuralgia to be up to 43% in patients who are 
diagnosed with acute herpes zoster.[14] We will calculate a sample size required to achieve an 
of 5 and power of 80% to detect a clinically relevant reduction in the incidence of PHN from 43% 
to 10%. We will allow for 10% loss of follow-up. 
 
6. Expected Outcomes: 
We expect that patients undergoing ultrasound guided nerve block will have decreased incidence 
of subacute herpetic neuralgia and PHN.  We also expect pain to be well controlled at 1 hour, 1 
week, 1 month, and 3 months post nerve block. 
 
7. Adverse Event Reporting: 
Side effects of local anesthetics are rare but usually target the central nervous system (numbness, 
metallic taste, anxiety, visual changes, muscle twitching, seizure, somnolence, coma, respiratory 
depression) and the cardiovascular system (hypertension or hypotension, tachycardia or 
bradycardia, ventricular arrhythmias and/or asystole). All adverse and unexpected events will be 
recorded during the calls in the 3-month follow-up period and reported to the IRB as per hospital 
policy. Adverse events will also be included in the final publication. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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