Main Pain Indicators for Injectable Fillers
Dr S. Sadeghi, M.D, PhD, FRACGP 1, Dr M. Dingley1. MB BS. FFMACCS, Dr C. Gaulton, MB BS, FRACGP1.Dr D. Whiteman MB BS, PhD, FAFPHM2
1 The Cosmetic Medicine Centre, Brisbane, QLD
2Queensland Institute of Medical Research, QLD
Introduction: Minimally invasive cosmetic facial surgery procedures including injectable fillers are more popular than ever. Many of the newer fillers are pre-incorporated with lidocaine to reduce pain however any such procedure that injures dermal or subcutaneous tissue can also cause pain. To reduce this pain different techniques are being used including application of topical anaesthetic creams like Eutectic Mixture of Local Anaesthetics EMLA®. In order to identify the most practical and effective method of reducing pain using topical anaesthetic for patients undergoing hyaluronic acid (HA) injections on the face we performed a randomised controlled trial by examining pain level experienced by patients during this procedure based on type of topical anaesthetic dressing that they had.
Methods and materials: We ran a randomised controlled trial from September to October 2011 at The Cosmetic Medicine Centre among patients that were undergoing HA filler injection procedures. During this period of time, volunteer patients were invited to report the severity of pain that they experienced on a scale of 0-10 based on a standardised pain scale. Participants were allocated into two groups with or without occlusion of topically applied EMLA. Unidentifiable data was recorded on an electronic database, SAS statistical package was used to examine any statistical difference in pain scale observed among clients.
Results: From 114 clients, 69 of them accepted to participate. The majority of participants (73%) did not find these procedures very painful scoring pain levels from 0-3. Despite a lack of statistically significant difference in pain scale, based on type of application of EMLA, patients in occluded dressing group reported slightly lower scales of pain. Depth of filler injection also was not a significant factor in pain level, however fillers pre-incorporated with lidocaine, although not statistically significant (p-value =0.3), seemed to be less painful compared with plain fillers.
Conclusion: Injecting HA fillers is not a distressing procedure. We did not find a significant difference in pain score based on type of dressing applied. Finally, local infiltration or inclusion of lidocaine inside the filler seems to be an important factor in pain reduction.
Our small randomised controlled trial study could be a good preliminary study for a larger multicentre study to examine any association between pain and type of local or topical anaesthetic.
Minimally invasive facial cosmetic surgery procedures including injectable hyaluronic acid (HA) fillers are more popular than ever Many of the newer fillers contain lidocaine to reduce pain (1, 2). However administration of injections, whether local anaesthetic or cosmetic injectable, that injures dermal or subcutaneous tissue can result in significant distress and discomfort to patients. In fact, such a pain may deter patients from similar procedures in the future. In order to reduce pain, different techniques can be used, such as tapping/vibrating (3-5), cooling (6), local anaesthetics/nerve blocks (7) and topical anaesthetic creams (8-12). Topical anaesthesia was previously reserved for mucosal surfaces only, however the introduction of other topical anaesthetic creams including Eutectic Mixture of Local Anaesthetics EMLA®, with ability to penetrate the papillary dermis (13) has provided an effective topical anaesthesia for either superficial procedures or for painless insertion of the needle. Use of topical anaesthetic agents prior to cosmetic procedures not only can reduce pain it also has been shown to be safe and effective across a range of applications (9).EMLA can be delivered in different ways (occluded vs. non-occluded). All published studies suggested superiority of the occluded dressing to non-occluded dressing. However, to our knowledge, there have been few studies directly compare these approaches. In our literature search we found one study comparing occluded versus non-occluded methods with no statistically significant difference between them (sample size 40) (14). Another study by Kashkouli et al reported the unpopularity of occluded dressing by clients in their experience with no supporting data (8).
In order to identify the most effective method of reducing pain using topical anaesthetic for patients undergoing cosmetic HA filler injections on the face we performed a single centre randomised controlled trial to examine pain level experienced by clients during the procedure. The other co-variates that were examined in this study were duration of time that topical anaesthetic remained on the face (15), method of application (occluded dressing or non-occluded dressing of EMLA, depth of injection and also presence or absence of pre-incorporated lidocaine in HA fillers (1, 6, 16).
Patients and Methods
We ran a randomised controlled trial from September to October 2011 at The Cosmetic Medicine Centre, Brisbane, QLD, among all patients that were undergoing HA filler injection procedure in that period. Participation was voluntary and only patients that signed the consent form to participate in our study were included in the study. All participants were assigned to one of two groups based on the type of EMLA dressing i.e. with and without occlusion. Allocation was based on alternative days of the week (Tuesday and Thursday for occluded and Monday, Wednesday and Friday for non-occluded dressing) therefore everyone received same type of occluded or non-occluded treatment depending on the allocation of the day to that type of dressing with EMLA. For the occluded group, after applying EMLA cream on face, the area was covered with plastic wrap. In the non-occluded group however, the area was left air-exposed. During our study, participants were asked to report the severity of pain that they experienced on a scale of 0-10 based on standardised pain scale through a self-administered questionnaire (17). To assist patients with their decision making and also to obtain more consistent responses, a detailed table of pain scale with clear examples of pain levels was provided along with the questionnaire. To avoid response bias we kept participants unaware of main research question, therefore we included other questions in the questionnaire about participants’ gender, age, time that they waited in waiting room, satisfaction from previous treatments and type of treatment they received that day. Finally, treating doctors were asked to fill in another questionnaire at the end of the procedure for each patient, asking the type of procedure (only filler or filler with botulinum toxin) and areas of injection based on the anatomical zones of face presented in a pictorial format – (from trichion to glabella, glabella to subnasale, upper lip and lower lip to menton). In addition, treating doctors were asked to record the product name and also indicate any infiltration of the area with lidocaine prior to the procedure. By knowing the injection site and type of the filler we were able to determine depth of injection (superficial or deep). Finally, clinic staff recorded the time when the cream was applied to participants’ faces and clinicians recorded the time that cream was removed prior to the procedure.
We entered data in a de-identified format to an electronic database and used SAS statistical package for analysis (SAS Institute, Inc.). For analysis we first ran a univariate categorical analysis to identify any statistically significant differences (α≤0.05) between occluded and non-occluded dressing groups based on their gender, age (<30 yrs, 30-50 yrs, and 50+ yrs), pain score (≤5 or >5) once for all fillers and then separately for superficial fillers and deep fillers. Fillers like Esthelis Basic® were considered superficial and fillers like Juvederm Ultra XC®, Juvederm ultra plus XC® , Juvederm Voluma®, Restylane®, Modelis® and SubQ® were consider deep unless being used in a different depth (Esthelis Basic® for the treatment of tear trough) or anatomical location. Because of the limitation in sample size, we combined intermediate to deep fillers in one category as deep.
In another analysis we examined the pain score (≤5 or >5) based on presence or absence of lidocaine infiltrated prior to the procedure or premixed with the filler. We also calculated p-values for each examined factor using chi-square statistic.
From 114 potentially eligible participants, 69 (61%) accepted the invitation to participate in the study. Of these, 42 persons attended the clinic on days assigned to the occluded dressing group, and 27 persons attended on days assigned to the non-occluded dressing group. The majority of participants (68%) were older than 50 years of age while 3% were younger than 30 and 29% were aged 30-50 years (Table 1). Despite a small difference in distribution of age between occluded and non-occluded dressing group this difference was not statistically significant (p-value 0.15).
The average time that EMLA cream stayed on patients’ faces was 36.1 minute (SD 6.3) for occluded dressing group versus to 35.6 minute (SD 9.6) for non-occluded group with no statistically significant difference between two groups (p-value 0.78 ) (Table-1).
The pain scores reported by participants was skewed in both groups, however there was less skewing for the occluded group compared to the non-occluded group (Graph-1). An overall pain score of five or less was reported in 93% of occluded dressing group while it was 82% for the non-occluded group (p-value 0.16).
Overall self-reported pain scores were low, but slightly more participants in occluded group reported pain scores of five or less than the non-occluded participants at both injection depths (88% Vs 78% and 96% Vs 83% superficial and deep injection categories consecutively); none of these differences between the groups were statistically significant however (p-value 0.52 and 0.16). In each category (superficial and deep injection), a pain score of more than five was reported slightly more for superficial injections compared to deep injections (15% Vs 9%).
No significant difference was noticed in the distribution of injections for different regions of the face in each group, and due to small sample size in each region pain scores were not presented (Table-2).
Finally, we compared the pain scores between patients who received local anaesthetic injection prior to the hyaluronic acid injection or received hyaluronic acid pre-incorporated with lidocaine (Table-3). In this analysis type of EMLA dressing did not have any role as we were interested in the role of local rather than topical anaesthetics. In this analysis, we noticed that 92% of patients in anaesthetic group reported pain score of five or less compared to 83% in the other group although the p-value was not statistically significant (0.3).
According to our study findings injecting fillers is not a distressing procedure for the clients as most of the participants reported very low scores of pain in each group. However, participants who had occluded dressing reported slightly lower pain scores than those who had non-occluded dressing although the difference was not statistically significant. Finally, incorporation of lidocaine with the filler or infiltration of lidocaine prior to injection of fillers reduces the pain score although again the difference between the two observations didn’t reach statistical significance.
This study has weaknesses and strengths. The small sample size was a major limitation in our study. In fact we could have ended up with statistically significant difference between two groups if we had larger sample size as p-value is sample size dependent (18). To increase the sample size, we either need to have a larger sample size, which is sometimes hard to fund (1, 2,17,19), or use a multicentre study which is more favourable but needs closer cooperation between cosmetic centres (20, 21). Treating doctors were aware of the patients’ status, making this study single blinded rather than a double blinded study, raising the potential issue of information bias. However, in our study patients scored their pain level independently after leaving the procedure room and doctors had no role in scoring pain that patients experienced. Therefore the single blinded design should not have had any effect on the findings of this study.
In this study, we were unable to examine the effect of time as both groups had almost the same mean duration of exposure to EMLA cream. Furthermore, the recommended duration for dressing with EMLA cream in some studies has been reported to be between 45 to 60 minutes while in our study it was applied for around 30 minutes (shorter than those recommendations) which can partially address the lack of statistical difference between two methods (15, 22). However there are other studies that suggest having EMLA cream on patients’ faces for longer periods of time is a draw back in terms of practicality and therefore is not considered very popular for non-surgical procedures (23).
Another possible reason for not finding a statistically significant result could be volunteer bias. In this type of bias people who are enthusiastic and positive, participate in the study and being blind to the study outcome, usually answer as positive as possible. One way to deal with this type of bias which also helps to increase the sample size is half face study. In this particular case we could have applied closed dressing to one half and open dressing to the other half of face. Another source of potential error is the allocation of week days, however in this procedure patients or staff were not aware about the allocations of the days when booking patients weeks before study begun. Furthermore there was no any difference between days of the week and type of the procedures that patients were booked for.
Our study also had its strengths. Low participation proportion is also an important threat in interventional studies which tends to make them suffer (18). In our study, participation proportion was high therefore it is unlikely that our findings would be subject to volunteer/participant bias.
In order to avoid the effect of confounding factors in the final results we adjusted our findings for gender, age and place of procedure in a logistic regression analysis however as findings did not vary from row analysis findings we did not present them in the tables.
Our findings were mostly in alignment with another similar study by Suswardana et.al that also showed no statistical difference between occluded and non-occluded application of EMLA (14).
Optimising pain control is a priority for cosmetic medicine procedures. In this small trial, we found no evidence that EMLA cream applied to the face through occluded dressings provided significantly better pain relief than non-occluded dressings. These data re preliminary however, and await confirmation in a larger trial which might be coordinated through a multi-centre collaboration
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Graph 1: Pain score in scale of ten among occluded and non-occluded dressing groups.
Type of EMLA application
Duration of dressing(p-value)=0.78
Mean 36.1 SD 6.3
Mean 35.6 SD 9.2
Table 1: Demographics of the participants and duration of the dressing on each group:
Type of EMLA application
Pain score (p-value)=0.16
Five or less
More than five
Depth of injection
Five or less
More than five
Five or less
More than five
Place of injection
Lower lip to menton
Table 2: Pain scores reported by each group of participants (occluded vs non-occluded)
Table 3: Pain score based on presence of absence of local anaesthetic in a combined analysis regardless of type of dressing.
Presence or absence of lidocaine
Pain score (p-value)=0.30
Five or less
More than five