A Randomized Controlled Trial Evaluating Three Non-invasive Analgesic Techniques in Pain Prevention During Injections
Phase: PHASE4
Conditions: Injection Pain Prevention
Sponsor: Enrique Salmeron

 
Evaluation of Three Non-invasive Analgesic Techniques in Pain Prevention 
During Injections 
 
Clinicaltrials.gov - NCT03974633 
 
Date of last Statistical Analysis Plan edition: 19/08/2019 
 Performed in order to adapt the protocol to the requirements of registration at 
clinicaltrials.gov 
Date of previous Statistical Analysis Plan: 08/06/2018 
 
Protocol version 2.0 
 
 
Person writing SAP: Enrique Salmerón-González 
 
SAP Contributors: Alberto Pérez-García 
Senior statistician: Alberto Pérez-García (blind researcher) 
Principal Investigator: Enrique Salmerón-González 
Investigators participating in the practical part of the study: 
 Enrique Salmerón-González 
 Elena García-Vilariño 
 Alberto Sánchez-García 
 Alfonso Valverde-Navarro 
 
 
 
Background 

2 
 
The application of injectable substances, whether local anesthetics, vaccines, drugs or 
cosmetics, can cause significative pain and discomfort. There exists a wide range of 
variables that may influence the subjective experience of each patient during the 
performance of an injection, like the type of substance utilized, the volume of liquid 
infiltered, the anatomic location, or whether a non-invasive anesthetic technique is utilized 
(1). 
 
As regards traditionally used non-invasive analgesic techniques for pain control during 
injections, there are a limited amount of clinical trials that provide an adequate level of 
evidence in this field (1). Some studies claim to have proven the efficacy of cold, anesthetic 
creams or vibration for pain control during injections (2). Notwithstanding, these studies 
have generally focused in comparing only the studied analgesic technique with a control 
group, instead of comparing anesthetic techniques among themselves (2). Furthermore, it is 
even scarcer the amount of studies focused in the field of cosmetic subcutaneous injections; 
whereas most of the reported studies have been performed in the context of anesthetic 
injection in odontology, intravitreal injections, or blood sample collection in pediatric 
population (3). 
 
The use of cold for pain control during injection has been traditionally utilized in different 
contexts. Notwithstanding, scientific evidence in favor of the use of cold as an analgesic 
agent in the context of injections is scarce, and has a low level of evidence (4). The 
mechanisms through which cold is considered to elevate pain threshold are: an alteration of 
nerve conduction, reduction of muscle spasms and prevention of tissue edema (4-6). 
 

3 
 
The application of topical anesthetic cream is frequently used for minimizing pain caused 
by injections (3). The main disadvantage of this method is the time required for the 
anesthetic effect to start. Different studies have shown that penetration depth of the 
anesthetic effect is of 3mm after 30-60 minutes, and 5mm after 90-120 minutes (7,8). Many 
authors reported better results in pain control with the use of this type of substances than 
with placebo (9-13). Notwithstanding, most of those studies were focused in the use of 
topical anesthetics in oral mucosa prior to anesthetic injection in odontology procedures, 
and most of them included reduced samples (lower than 50 subjects) (9,10,14-18). There is 
also a relevant amount of studies that did not find any statistically significant differences in 
terms of pain control between control and intervention groups (14-19). 
 
Vibration analgesia was first described in 1984 by Reed et al (20). It is the non-invasive 
method that has been studied less in classic literature, although in the last 10 years its 
interest has grown significantly, with the apparition of new studies in different clinical 
contexts, and with results that generally favor its use (21-25). The studies that have reported 
an improvement in pain control have been performed in the field of ondontology (21), 
infiltration of local anesthetics in children (22), keloid infiltration (23), botulinum toxin 
injection (24), and hyaluronic acid injection for lip filling (25). Notwithstanding, other 
studies have reported unfavorable results for this analgesic method, in the field of 
venipuncture in children, and anesthetic injections in odontology (26-28). All authors agree 
that the amount of studies focused in this type of anesthetic method is scarce, and that more 
studies with a higher level of evidence are required in order to evaluate its real utility (20-
31). 
 

4 
 
References 
1. Babamiri K, Nassab R. The evidence for reducing the pain of administration of 
local anesthesia and cosmetic injectables. J Cosmet Dermatol. 2010 Sep;9(3):242-5.  
2. Davoudi A, Rismanchian M, Akhavan A et al. A brief review on the efficacy of different 
possible and nonpharmacological techniques in eliminating discomfort of local anesthesia 
injection during dental procedures. Anesth Essays Res. 2016 Jan-Apr;10(1):13-6.  
3. Strazar AR, Leynes PG, Lalonde DH. Minimizing the pain of local anesthesia injection. 
Plast Reconstr Surg. 2013 Sep;132(3):675-84.  
4. Ernst E, Fialka V. Ice freezes pain? A review of the clinical effectiveness of analgesic 
cold therapy. J Pain Symptom Manage 1994; 9: 56–9.  
5. Smith KC, Comite SL, Storwick GS. Ice minimizes discomfort associated with injection 
of botulinum toxin type a for the treatment of palmar and plantar hyperhidrosis. Dermatol 
Surg 2007; 33: S88–91.  
6. Elibol O, Ozkan B, Hekimhan PK et al. Efficacy of skin cooling and EMLA cream 
application for pain relief of periocular botulinum toxin injection. Ophthal Plast Reconstr 
Surg. 2007; 23: 130–3. 
7. Simons FE, Gillespie CA, Simons KJ. Local anesthetic creams and intradermal skin 
tests. Lancet. 1992;339:1351–1352. 
8. Gajraj NM, Pennant JH, Watcha MF. Eutectic mixture of local anesthetics (EMLA) 
cream. Anesth Analg. 1994;78:574–583. 
9. Hersh EV, Houpt MI, Cooper SA, et al. Analgesic efficacy and safety of an intraoral 
lidocaine. J Am Dent Assoc 1996;127:1626–34. 

5 
 
10. Hutchins HS, Young FA, Lackland DL, Fishburne CP. The effectiveness of topical 
anesthesia and vibration in alleviating the pain of oral injections. Anesth Prog   
1997;44:87–9. 
11. Rosa AL, Sverzut CE, Xavier SP, Lavrador MA. Clinical effectiveness of lidocaine and 
benzocaine for topical anesthesia. Anesth Prog 1999;46:97–9. 
12. Rosivack RG, Koenigsberg SR, Maxwell KC. An analysis of the effectiveness of two 
topical anesthetics. Anesth Prog 1990;37:290–2 
13. Cohen JL, Gold MH. Evaluation of the efficacy and safety of a lidocaine and tetracaine 
(7%/7%) cream for induction of local dermal anesthesia for facial soft tissue augmentation 
with hyaluronic acid.  J Clin Aesthet Dermatol. 2014 Oct;7(10):32-7. 
14. Nusstein JM, Beck M. Effectiveness of 20% benzocaine as a topical anesthetic for 
intraoral injections. Anesth Prog 2003;50:159–63. 
15. Fukayama H, Suzuki N, Umino M. Comparison of topical anesthesia of 20% 
benzocaine 
and 60% lidocaine gel. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 
2002;94:157–61. 
16. Drum M, Reader A, Beck M. Long buccal nerve block injection pain in patients 
with irreversible pulpitis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 
2011;112:e51–4. 
17. de Freiras GC, Pozzobon RT, Blaya DS et al. Efficacy of benzocaine 20% topical 
anesthetic compared to placebo prior to administration of local anesthesia in the oral cavity: 
a randomized controlled trial. Anesth Prog. 2015 Summer;62(2):46-50. 

6 
 
18. Parirokh M, Sadeghi AS, Nakhaee N et al. Effect of topical anesthesia on pain during 
infiltration injection and success of anesthesia for maxillary central incisors. J Endod. 2012 
Dec;38(12):1553-6.  
19. Gupta NK, Upadhyay A, Dwivedi AK et al. Randomized controlled trial of topical 
EMLA and vapocoolant spray for reducing pain during wDPT vaccination. World J 
Pediatr. 2017 Jun;13(3):236-241.  
20. Reed ML. Mechanoanesthesia for intralesional injections. J Am Acad Dermatol 1984; 
11: 303.  
21. Nasehi A, Bhardwaj S, Kamath AT et al. Clinical pain evaluation with 
intraoral vibration device during local anesthetic injections. J Clin Exp Dent. 2015 Feb 
1;7(1):e23-7.  
22. Bagherian A, Sheikhfathollahi M. Children's behavioral pain reactions during local 
anesthetic 
injection 
using 
cotton-roll vibrationmethod 
compared 
with 
routine 
topical anesthesia: A randomized controlled trial. Dent Res J (Isfahan). 2016 May-
Jun;13(3):272-7.  
23. Park KY, Lee Y, Hong JY et al. Vibration Anesthesia for Pain Reduction During 
Intralesional Steroid Injection for Keloid Treatment. Dermatol Surg. 2017 May;43(5):724-
727. 
24. Li Y, Dong W, Wang M et al. Investigation of the Efficacy and Safety of 
Topical Vibration Anesthesia to Reduce Pain From Cosmetic Botulinum Toxin A 
Injections in Chinese Patients: A Multicenter, Randomized, Self-Controlled Study. 
Dermatol Surg. 2017 Oct 6.  

7 
 
25. Guney K, Sezgin B, Yavuzer R. The Efficacy of Vibration Anesthesia on Reducing 
Pain Levels During Lip Augmentation: Worth the Buzz? Aesthet Surg J. 2017 Oct 
1;37(9):1044-1048.  
26. Secil A, Fatih C, Gokhan A et al. Efficacy of vibration on venipuncture pain scores in a 
pediatric emergency department. Pediatr Emerg Care. 2014 Oct;30(10):686-8. 
27. Raslan N, Masri R. A randomized clinical trial to compare pain levels during three 
types of oral anesthetic injections and the effect of Dentalvibe® on injection pain in 
children. Int J Paediatr Dent. 2018 Jan;28(1):102-110. 
28. Erdogan O, Sinsawat A Pawa S et al. Utility of Vibratory Stimulation for Reducing 
Intraoral Injection Pain. Anesth Prog. 2018 Summer;65(2):95-99. 
29. Nanitsos E, Vartuli R, Forte A et al. The effect of vibration on pain during local 
anaesthesia injections. Aust Dent J 2009; 54: 94–100.  
30. Smith KC, Comite SL, Balasubramanian S et al. Vibration anaesthesia: a noninvasive 
method of reducing discomfort prior to dermatological procedures. Dermatol Online J 
2004; 10(2): 1. 
31. Taddio A, Lord A, Hogan ME et al. A randomized controlled trial of analgesia during 
vaccination in adults. Vaccine. 2010 Jul 19;28(32):5365-9. 
 
Objective 
In this clinical trial, we evaluated the effectivity of three non-invasive analgesic techniques 
(cold, anesthetic cream and vibration), including a control zone, in 100 healthy individuals, 
by performing subcutaneous forehead injections of 0,1ml physiologic saline. 
 

8 
 
Hypotheses 
Any of the analgesic methods improves pain control respect to not utilizing any of them.  
Our second aim is to evaluate if any of the analgesic methods evaluated achieves a better 
pain control than the others. 
 
Randomization details 
The sequence of infiltration zones of each subject was randomized through simple 
randomization, performed by the statistic department of the Medical Research Institute 
Hospital La Fe. 
 
 
 
 
 
 
 
 
 
 
 
 
 

9 
 
CONSORT Flow Diagram 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Assessed for eligibility (n=104  ) 
Excluded  (n=4   ) 
   Not meeting inclusion criteria (n=2  ) 
   Declined to participate (n=2  ) 
   Other reasons (n= 0 ) 
Lost to follow-up (give reasons) (n=0  ) 
Discontinued intervention (give reasons) (n=0  
)
24 possible sequences of infiltration 
ABCD, ABDC, ACBD, ACDB, ADBC, ADCB, 
BACD, BADC BCAD, BCDA, BDAC, BDCA, 
CABD, CADB, CBAD, CBDA, CDAB, CDBA, 
DABC, DACB, DBAC, DBCA, DCAB, DCBA 
- Assigned through simple randomization 
Analysed  (n=100  ) 
 Excluded from analysis (give reasons) (n=0  
) 
Allocation
Analysis
Follow-Up
Randomized (n=100  ) 
Enrollment

10 
 
Interim analysis 
Performed by: Alberto Pérez-García 
Date: 16/03/2019 
An interim analysis was performed when 50 subjects had already been recruited. A sample 
size of 46 subjects (184 interventions) was estimated, assuming a variance in the values of 
the control zone of 2,69, with a precision of 1, confidence level of 95%, and statistical 
power of 0,9. 
No modifications were performed to the protocol after the interim analysis. 
 
Guidelines for stopping study early: None 
 
Date of final analysis: 30/04/2019 
 
No protocol deviations were detected 
Intervention adherence was not necessary as no follow-up was required 
 
 
 

11 
 
Population analyzed 
From the 100 healthy subjects included in the study, 61 were females and 39 males. The 
average age was 39,71 (sd 13,22). 
 
Exclusion criteria 
 Chronic pain syndromes/conditions 
 Receiving opioid analgesics and sedatives 
 Extreme sensitivity to cold 
 Allergy to components of the anesthetic cream EMLA (eutectic mixture of 
lidocaine; 2,5% lidocaine and prilocaine 2,5%)  
 Inability to understand the visual analogic scale 
 
Inclusion criteria 
Every subject that did not meet any of the exclusion criteria, and signed the informed 
consent, was included in the study 
 
Recruitment strategy 
Adult employees and volunteers at The University and Polytechnic Hospital La Fe that 
understood the study and signed the informed consent were eligible for participation. 

12 
 
We did not have any case of withdrawal from the study 
 
Material and methods 
This study is a randomized, controlled, simple-blind clinical trial, and it has been approved 
by the Ethics Committee of the Medical Research Institute Hospital La Fe. The study 
included 100 healthy volunteers, and it was performed at the University and Polytechnic 
Hospital La Fe, Valencia.  
 
The procedures of the study consisted in the sequential performance of four injections of 
0,1mL of physiologic saline (0,9%NaCl) in the forehead of each subject, 2cm above the 
eyebrows, with a 29G needle, after applying each one of the non-invasive analgesic 
methods studied in the trial, except for the control zone. The anesthetic method utilized in 
each part of the forehead of each patient was randomized through simple randomization. 
Injections always started from the right side of the forehead to the left. The non-invasive 
analgesic methods utilized were: 
 Control zone (A): None 
 Vibration (B): Application of the vibrating device on the skin below the injection 
site, before and during injection. 
 Cold (C): Application of a bag of 50mL of frozen physiologic saline covered with a 
plastic glove on the injection site for 50 seconds prior to performing the injection. 
 Anesthetic cream (D): Application of a uniform thickness of 2mm of the anesthetic 
cream EMLA covered with an adhesive transparent plastic dressing for 30 minutes, 
before injection. 

13 
 
 
Results were evaluated through surveys that included demographic data (initials, gender, 
age), a Visual Analogic Scale (VAS) with a maximum value of 10 and minimum of 0 for 
pain evaluation of each of the four injected zones of each subject. Also, two direct 
questions were included, one with the aim of determining the preferred method for each 
subject for future injections (“Which anesthetic technique would you prefer if you had to be 
injected again?”), and another to report discomfort related to the application of any of the 
anesthetic procedures (“Did any of the anesthetic methods cause you pain or discomfort?”) 
 
An interim analysis was performed when 50 subjects had already been recruited. A sample 
size of 46 subjects (184 interventions) was estimated, assuming a variance in the values of 
the control zone of 2,69, with a precision of 1, confidence level of 95%, and statistical 
power of 0,9. The statistical study included a Friedman test for evaluating the existence of 
differences between the average results of each different anesthetic method and control 
zones, and to evaluate the existence of differences in pain referred depending on the 
injection order, or the side of the forehead injected (central or lateral). After finding 
statistically significant differences between average pain referred with different techniques, 
paired comparisons were performed between each non-invasive anesthetic method with a 
Wilcoxon test. For comparison of average pain according to subject gender, a Mann-
Whitney U test was utilized. Statistical analysis was performed by a researcher that did not 
participate in the practical part of the study (Alberto Pérez-García) utilizing the software 
SPSS.