Cite as: Cohen S. ASRA answers: is the use of skin wheals in interventional pain procedures an obsolete practice. ASRA Pain Medicine News 2025;50. https://doi.org/10.52211/asra020125.006.

ASRA Answers

Introduction

The use of subcutaneous local anesthetic skin wheals prior to interventional pain procedures has been a long-standing practice. However, current examination suggests that this practice may not only be unnecessary but may also negatively impact patient experience. This editorial explores the rationale against the routine use of skin wheals, highlighting the evolving understanding of pain management.

Literature Review

Historically, the creation of skin wheals was thought to enhance patient comfort by numbing the area before a procedure. However, evidence indicates that this approach may not alter pain experiences during interventional procedures and that excessive local administration may even reduce the diagnostic specificity of some procedures.^1-3 In one prospective study, needle sticks performed using skin wheals before lumbar medial branch (facet joint nerve) blocks caused more pain than those performed without skin wheals or with another type of local anesthesia.¹  

Patients often report similar pain levels whether they receive these preemptive injections or not. Additionally, nerve endings are concentrated in the dermis as it has evolved to be the first line of defense against potentially harmful stimuli, alerting individuals to imminent danger.^4-6 One could argue that the formation of a skin wheal may paradoxically exacerbate pain by distending the dermis and epidermis, which are densely populated with nerve endings, ultimately resulting in heightened tissue distortion. In clinical studies that have measured pain after both a skin wheal and an entire chronic pain procedure, about one-third report the skin wheal, which takes a fraction of the time that a facet block, radiofrequency ablation procedure, sacroiliac joint injection, or epidural steroid injection take, to be more painful than the pain procedure itself.⁷ This raises important questions about the rationale for continuing a practice where the risk to patients often outweighs the benefits.

The reliance on skin wheals appears to stem from tradition rather than scientific evidence. Since the first pain clinics were staffed by anesthesiologists, who typically employed skin wheals before tunneling large-bore subcutaneous intravenous catheters (IVs) lengthwise over veins, this practice became routine.⁸ Although demographic trends are changing, most interventional pain physicians are trained in anesthesiology as their primary specialty. They have routinely utilized subcutaneous local anesthetics (skin wheal) to reduce patient discomfort when placing IV catheters. This practice has been supported historically; IV catheter placement was more challenging earlier on due to the limited availability of modern, thin-walled, and flexible catheters. Early catheters were often larger, more rigid, and harder to insert, increasing the risk of tissue trauma and discomfort.⁹ This practice continues to be reinforced as literature has shown that 1% subcutaneous lidocaine can reduce discomfort for patients during IV placement.⁵ Skin wheals are also used in other specialties that utilize needle-based approaches, such as pulmonology, interventional radiology, and sports medicine. However, the use of a skin wheal before IV catheter placement is different than for interventional pain procedures as the target veins are much more superficially located compared to the structures interventional pain physicians are trying to inject, such as facet joints or the epidural space for epidural steroid injections. The superficial nature of IV catheter placement renders the use of skin wheals more justifiable, whereas, for interventional pain procedures, this practice is harder to defend.

Needle gauge is pivotal in procedural techniques, impacting patient comfort, procedural accuracy, and overall outcomes. Needle gauge refers to the thickness of the needle with higher numbers indicating thinner needles and lower numbers signifying thicker ones. While thinner needles are often presumed to reduce pain, evidence suggests that this assumption, while generally true for lower gauge needles, does not always hold true for higher gauge needles. For example, a study comparing various gauges for lidocaine injections—27-gauge vs. 23-gauge vs. 21-gauge—found no significant difference in reported pain.¹⁰ Similarly, for Botox injections around the eyes, no difference in pain scores was noted between 32-gauge and 30-gauge needles.¹¹ These findings reflect a consistent theme in the scientific literature: Participants often do not perceive substantial differences in pain when comparing smaller diameter needles.

Routine Use of Skin Wheals Raises Several Important Concerns

First, relying on this practice may divert attention from the practitioner’s skills and the appropriateness of the chosen intervention. Ackerman et al. highlighted the potential for increased false-positive rates of diagnostic facet joint or medial nerve branch injections using subcutaneous local anesthetic.² Their study found that the incidence of a positive block (ie, >75% pain relief) was significantly higher in subjects who received a continuous injection of local anesthetic into their musculature vs. those individuals who received continuous saline followed by an injection of local anesthetic into either the facet joint or around the medial branch that innervates it. Thus, anesthetizing the skin and underlying soft tissue prior to medial branch (facet joint nerve) blocks can compromise diagnostic specificity as the local anesthetic may diffuse into the myofascial tissue, raising the likelihood of false-positive results. However, an alternative explanation is that the false-negative rate of blocks (ie from excessive procedure-related pain) is higher without the use of superficial local anesthetic.

Historically, the creation of skin wheals was thought to enhance patient comfort by numbing the area before a procedure. However, evidence indicates that this approach may not alter pain experiences during interventional procedures and that excessive local administration may even reduce the diagnostic specificity of some procedures.

Second, using skin wheals despite the lack of supporting evidence has implications for patient outcomes. Many studies emphasize that commonly used practices in pain management and medicine as a whole lack robust evidence, leading to variability in procedures and outcomes across different practitioners and institutions. For example, Prasad et al. analyzed 2,044 original articles with 1,344 focusing on medical practices. Among the 363 articles testing the standard of care, 146 (40.2%) reversed that practice.¹² This inconsistency can compromise patients’ quality of care, undermining their trust in healthcare providers.

Third, the routine use of skin wheals may cause more pain and contribute to unnecessary procedural complexity and inefficiency. Adding this step to interventional pain procedures increases the overall time required for the intervention without clear evidence of substantial benefit, particularly in deeper-target procedures like facet joint or epidural injections. This additional time can reduce procedural throughput, impacting clinic efficiency and increasing costs for the healthcare provider and the patient.

Alternative Strategies to the Skin Wheal

Alternative strategies can enhance patient comfort without relying on practices such as the skin wheal. For instance, education and communication about procedures can significantly alleviate anxiety and discomfort. Engaging patients in discussions about their treatment options can foster a sense of control and understanding, which may, in turn, contribute to improved satisfaction and perceived outcomes.

Distraction techniques offer a powerful, evidence-based alternative for enhancing patient comfort during interventional procedures. By redirecting the patient’s focus away from the procedure, distraction can help reduce pain perception and alleviate anxiety. Simple methods, such as providing visual or auditory stimuli, can be highly effective. For instance, allowing patients to engage with virtual reality environments has been shown to lower self-reported pain scores and improve overall experiences compared to local anesthetic alone with fewer side effects, superior communication, and a shorter recovery period compared to intravenous sedation for epidural steroid injections.¹⁴

Moreover, advancements in technology and technique can provide effective methods for minimizing discomfort during interventional procedures. For example, ultrasonography has been shown to improve the accuracy of needle placement and reduce patient discomfort. As interventional pain management continues to evolve, practitioners should focus on integrating evidence-based approaches and innovative techniques rather than adhering to outdated practices like skin wheals.

Summary

In summary, the routine use of skin wheals when using a higher gauge needle lacks strong evidence and is typically unnecessary for most interventional pain procedures. For neuraxial and deep extra-axial blocks, such as epidural injections or medial branch blocks, skin wheals may compromise diagnostic accuracy by causing anesthetic diffusion. Additionally, their use can make the procedure more painful than necessary without adding any benefit. Similarly, for intra-articular injections and therapeutic procedures, their benefit appears limited and situational. Although many physicians are trained to use this technique for peripheral procedures, its application for deeper interventional blocks is unproven and unjustified as stimulation of nociceptors in the epidermis and dermis by creating a skin wheal adds unnecessary pain, especially when the procedure itself targets structures much deeper than these layers.

References

1. Chen AS, Miccio VF, Smith CC, et al. Procedural pain during lumbar medial branch blocks with and without skin wheal anesthesia: a prospective comparative observational study. Pain Medicine 2019;20(4):779-83. https://doi.org/10.1093/pm/pny322
2. Ackerman WE, Munir MA, Zhang JM, et al. Are diagnostic lumbar facet injections influenced by pain of muscular origin? Pain Pract 2004;4(4):286-91. https://doi.org/10.1111/j.1533-2500.2004.04402.x
3. Bakshi R., Berri H, Kalpakjian C, et al. (2015). The effects of local anesthesia administration on pain experience during interventional spine procedures: a prospective controlled trial. Pain Med 2016;17(3):488-93. https://doi.org/10.1093/pm/pnv015
4. Joukhadar N, Lalonde D. How to minimize the pain of local anesthetic injection for wide awake surgery. Plast Reconstr Surg Glob Open 2021;9(8):e3730. https://doi.org/10.1097/GOX.0000000000003730
5. Winfield C, Knicely C, Jensen C, et al. What is the least painful method of anesthetizing a peripheral iv site? J Perianesth Nurs 2013;28(4): 217-22. https://doi.org/10.1016/j.jopan.2012.09.007
6. Smith ESJ, Lewin GR. Nociceptors: a phylogenetic view. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2009;195(12): 1089–1106.https://doi.org/10.1007/s00359-009-0482-z
7. Cohen SP, Doshi TL, Kurihara C, et al. Multicenter study evaluating factors associated with treatment outcome for low back pain injections. Reg Anesth Pain Med 2022;47(2) 89-99. https://doi.org/10.1136/rapm-2021-103247
8. Upp J, Kent M, Tighe PJ. The evolution and practice of acute pain medicine. Pain Med 2013;14(1):124-44. https://doi.org/10.1111/pme.12015
9. Rivera AM, Strauss KW, van Zundert A, et al. The history of peripheral intravenous catheters: how little plastic tubes revolutionized medicine. Acta Anaesthesiol Belg 2005;56(3):271-82.
10. Wågø KJ, Skarsvåg TI, Lundbom JS, et al. The importance of needle gauge for pain during injection of lidocaine. J Plast Surg Hand Surg 2016;50(2):115-8. https://doi.org/10.3109/2000656X.2015.1111223
11. Yomtoob DE, Dewan MA, Lee MS, et al. Comparison of pain scores with 30-gauge and 32-gauge needles for periocular botulinum toxin type A injections. Ophthalmic Plast Reconstr Surg 2009;25(5):376-7. https://doi.org/10.1097/IOP.0b013e3181b1e526
12. Prasad V, Vandross A, Toomey C, et al. A decade of reversal: an analysis of 146 contradicted medical practices. Mayo Clin Proc 2013;88(8):790-8 https://doi.org/10.1016/j.mayocp.2013.05.012
13. Elshaug AG, Watt AM, Mundy L, et al. Over 150 potentially low‐value health care practices: an Australian study. Med J Aust 2012;197(10): 556–60. https://doi.org/10.5694/mja12.11083
14. Cohen SP, Doshi TL, Munjupong CS, et al. Multicenter, randomized, controlled comparative-effectiveness study comparing virtual reality to sedation and standard local anesthetic for pain and anxiety during epidural steroid injections. Lancet Reg Health Southeast Asia 2024;27:100437. https://doi.org/10.1016/j.lansea.2024.100437