Background

Skin ink or tattooing (as it shall be referred to in this study) has been present from as early as 3300 BCE and has evolved into a popular mainstream accessory in the United States (US) and Europe recently.1 In reference to the US culture of tattooing, DeMello2 discusses the connotation of the tattoo as revolutionizing from a stigma of the working class into a middle class status symbol and artistic adornment in the 1970s. This timeframe corresponds to the New Age movement, which served as a redefining period for modern tattoos in mainstream media.2 The transition from a disparaged craft to a moderately acceptable art form over the last 2 decades bolstered the popularity of tattooing.3 According to national survey data in the US from 2004, as many as 36% of people under 40 have at least one tattoo.1 Women receive approximately 50% of all tattoos with an increasing number of these placed on the midline lumbar back region.4

Tattoo ink is derived from different mixtures of metallic salts, with each color comprised of numerous chemical variations.5 These mixtures require pre-market approval and are available in unmixed, premixed and liquid forms with the potential to cause cutaneous sensitivity reactions, chronic or systemic diseases.5-7 Tattoo artists combine these ink mixtures with other substances such as ethanol, isopropyl alcohol or glycerin based on their personal preferences to develop different color shades.6 Tattoo industry market surveys indicate that tattoo ink metal compositions are widely varied and may contain allergenic or toxic metals above the safe tolerable limit of 1 part per million.5

Currently, tattoo inks and color additives are regulated in the US as cosmetics under the Federal Food, Drug and Cosmetic Act with further oversight by varying state and local jurisdictions.1 Internationally, the Inter-Organization Program for the Sound Management of Chemicals states that there is no detailed regulation of tattoo colorants in the European Union and further classifies tattoo colorants as a legal paradox because of their incomplete and unknown chemical profile.8 The report also acknowledges that although these colorants are injected into the human body, the tattooing procedure itself is outside the scope of the Cosmetics Directive and is therefore not further regulated.8 This fundamental lack of medical grade regulations on tattoo ink permits the use of a wide variability of ink compositions with the potential to cause an extensive array of dermatological consequences. The sequelae associated with loosely regulated tattoo ink concoctions may include, but are not limited to, localized infections and inflammatory processes around the area of tattooed skin - possibly occurring even after prolonged time periods following tattoo placement.9

Regional anesthesia is used by anesthesia and pain medicine providers for primary pain control during or after surgery, to treat chronic pain states or to decrease labor and delivery pain in the parturient population.10 As tattoos continue to gain popularity, it is necessary that the medical risks associated with multifarious ink compositions are examined in relation to regional anesthesia. An anesthetic provider's decision to offer regional anesthesia to a patient must be judicious and is inherently complex. Though the vast majority of patients who understand the benefits provided by regional anesthesia often consent willingly, various factors such as pre-existing neurological and neuromotor conditions may negate the option of this treatment.11 Unfortunately, patients with tattoos may also be classified as a cautionary population for regional anesthesia because of unknown ramifications.

A prospective, randomized, blinded study conducted by Campbell et al.12 in 1996 indicated that needle insertion through tattooed skin may lead to the potential complication of coring, in which epidermal cells trapped within a hollow needle can be transferred to deeper tissues. This has been shown to occur even with small 25-gauge Quincke and Whitacre spinal needles with and without a stylet12 as used for spinal anesthesia blocks. An experimental study using a rabbit model by Ferraz13 showed that after intrathecal puncture, tissue impregnated with ink pigments was present under optical microscopy; however, no ink pigments were found in the actual nervous tissue.13 The increased popularity of tattooing among certain patient populations combined with minimal control of tattoo ink compositions and the incidence of tissue coring, leads to concerns about the placement of regional anesthesia over areas of tattooed skin. The possibility of tissue coring and ink pigment deposition in the proximity of nervous tissue leads many providers to use diverse techniques to provide regional anesthesia through or near areas of tattooed skin.4

Shanbhag and Chilvers14 conducted a survey in England examining the possible ramifications of neuraxial analgesia and anesthesia in obstetric patients with tattooed skin. Results revealed 65% of consultant anesthetists would insert a spinal or epidural in the usual space regardless of a tattoo, with none of the providers refusing to perform regional anesthesia.14 Modern practice when encountering this situation includes many different approaches which are based on the personal opinion and experience of the provider. These include: selecting a different vertebral space or injection site placement, using a different angle of approach, finding an area of pigment-free skin within the tattooed region, nicking the skin prior to needle insertion or directly piercing through the tattooed skin.4 Regardless, the patient must always be made well aware of the approaches available and risks associated with the regional anesthesia procedures performed in and around the areas of tattooed skin.

Considering the increasing prevalence of tattoos, the widely variable composition of substances used and the lack of medical grade regulation, anesthesia providers must implement critical judgment in selecting regional anesthetic techniques in the vicinity of tattooed skin. Although the consequences of administering regional anesthetics through tattooed skin are unknown at this time, the possible ramifications could include long-term unanticipated complications such as arachnoiditis or a neuropathy secondary to an inflammatory reaction.15 Currently, there are no specific guidelines to address the safest approach of providing regional anesthesia through or around an area of tattooed skin.4

An initial search of the JBI Database of Systematic Reviews and Implementation Reports, the Cochrane Library, MEDLINE (EBSCOhost) and CINAHL yielded no systematic reviews or non-animal model-based randomized controlled trials investigating the impact of tattoos on the delivery of regional anesthesia; however, limited qualitative and quantitative data exists regarding patients, providers and other affected parties. This leads us to pose the question: What is the impact of tattoos on the delivery of regional anesthesia? In an attempt to capture all of the available evidence on this topic, a comprehensive systematic review will be undertaken. This systematic review is the sensible starting point to begin development of future practice guidelines for anesthesia providers when encountering this clinical situation. This review's goal is to provide either a clear answer for how to proceed in this clinical setting dictated by evidence-based practice or to provide a starting point for future research to develop clinical recommendations.

Inclusion criteria

Types of participants

The review considers adult (18 years of age or older) patients presenting for a regional anesthetic technique who have tattooed skin over the necessary anatomic area for needle placement as well as the anesthesia providers, surgeons or other affected parties (e.g. patient families, hospital or clinic administrators or insurance providers).

Exclusion criteria includes patients under the age of 18 because of issues with informed consent and patient populations with previous neurological or neuromuscular deficits because of confounding variables and the impact on results.

Types of intervention(s)/phenomena of interest

The intervention of interest is regional anesthetics administered through tattooed skin compared with those patients who receive these techniques in the absence of tattooed skin. There is no limitation regarding the type, concentration/dosage and technique of the anesthetic administered.

The phenomena of interest is the perceptions and experiences (which may include thoughts, opinions and biases) related to the administration of a regional anesthetic through tattooed skin from the perspective of the patient, anesthesia provider, surgeon or other affected parties (e.g. patient families, hospital or clinic administrators or insurance providers).

Context

The context includes worldwide patients with tattoos who have received regional anesthesia in accordance with professional standards of aseptic or sterile technique.16 This will eliminate confounding variables such as breaks in aseptic or sterile technique leading to complications if that is typical practice in a served population.

Outcomes

The quantitative section of the review includes the following outcome measures:

Prevalence and incidence of neural or tissue disorders or damage related to tattoo ink being transferred from cutaneous tissue to deeper tissues during the conduct of a regional anesthetic;

Type and severity of neural or tissue disorders, including pain, quality of life impact and physical function as measured by any applicable validated scale;

Outcomes related to disability, injury, physical impairment or other derangement because of the administration of a regional anesthetic through tattooed skin as measured by any applicable validated scale.

Types of studies

The quantitative component of this review considers both experimental and epidemiological study designs, including randomized controlled trials, non-randomized controlled trials, quasi-experimental studies, before and after studies, prospective and retrospective cohort studies, case-control studies and analytical cross-sectional studies.

The quantitative component of the review also considers descriptive epidemiological study designs, including case series, individual case reports and descriptive cross-sectional studies that compare patients with and without tattoos who have received regional anesthetics.

The qualitative component of this review considers studies that focus on qualitative data, including, but not limited to, designs such as phenomenology, grounded theory, ethnography and action research.

In the event that quantitative and qualitative studies are not available, other texts such as opinion papers, conference presentations and reports, discussion papers, position papers and any other sources of texts based on expert opinion discussing this issue will be included in the review.

Search strategy

The search strategy aims to find both published and unpublished studies. A three-step search strategy will be utilized in this review. An initial limited search of MEDLINE (EBSCOhost) and CINAHL will be initiated followed by an analysis of the text words contained in the title and abstract, and of the index terms used to describe the article. A second search using all identified keywords and index terms will then be undertaken across all included databases. Third, the reference list of all identified reports and articles will be searched for additional studies. Studies published in English will be considered for inclusion in this review. Studies published after 1970 until present will be considered for inclusion in this review because of a large increase in tattoo popularity and prevalence since this time.2

The databases to be searched include:

MEDLINE (EBSCOhost)

CINAHL

PubMed

Clinical Key

EMBASE

Web of Science

Cochrane CENTRAL

The search for unpublished studies will include:

ProQuest Dissertations and Theses

MedNar

Initial keywords to be used will be:

Tattoo(s) and anesthesia

Assessment of methodological quality

Quantitative studies selected for retrieval will be assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) (Appendix I). Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer.

Qualitative studies selected for retrieval will be assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Qualitative Assessment and Review Instrument (JBI-QARI) (Appendix I). Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer.

Textual studies selected for retrieval will be assessed by two independent reviewers for authenticity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Narrative, Opinion and Text Assessment and Review Instrument (JBI-NOTARI) (Appendix I). Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer.

Data extraction

Quantitative, qualitative and textual data will be extracted by two independent reviewers from studies included in the review using the standardized data extraction tools specific to each type of data or information (Appendix II). Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer. In the event of incomplete data, authors will be contacted for clarification where possible. If the correspondence does not yield a response or clarification, the data will be excluded.

Quantitative data extracted using the standardized data extraction tool from JBI-MAStARI will include specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives.

Qualitative data extracted using the standardized data extraction tool from JBI-QARI will include specific details about the methodology, method, phenomena of interest, setting, geographical context, cultural context, participants, data analysis and author's conclusions of significance to the review question and specific objectives.

Textual data extracted using the standardized data extraction tool from JBI-NOTARI will include specific details about the types for text, those represented, stated allegiance or position, setting, geographical context, cultural context, logic of argument(s) and author's conclusion(s) of significance to the review question and specific objectives.

Data synthesis

Quantitative studies will, where possible, be pooled in statistical meta-analysis using Joanna Briggs Institute System for the Unified Management, Assessment and Review of Information (JBI-SUMARI). All results will be subject to double data entry. Effect sizes expressed as a relative risk for cohort studies, odds ratios for case-control studies (for categorical data) and weighted mean differences (for continuous data) and their 95% confidence intervals will be calculated for analysis. A random effects model will be used and heterogeneity will be assessed statistically using the standard [chi]² test. If statistical pooling is not possible, the findings will be presented in narrative form, including tables and figures to aid in data presentation where appropriate.

Qualitative research findings will, where possible, be pooled using JBI-QARI. This will involve the aggregation or synthesis of findings to generate a set of statements that represent that aggregation, through assembling the findings (level 1 findings) rated according to their quality and categorizing these findings on the basis of similarity in meaning (level 2 findings). These categories will then be subjected to a meta-synthesis to produce a single comprehensive set of synthesized findings (level 3 findings) that can be used as a basis for evidence-based practice. Where textual pooling is not possible, the findings will be presented in narrative form.

Textual studies will, where possible, be pooled using JBI-NOTARI. This will involve the aggregation or synthesis of conclusions to generate a set of statements that represent that aggregation through assembling and categorizing these conclusions on the basis of similarity in meaning. The first step will generate a set of statements that represent the aggregated data through assembling the conclusions rated according to their quality. Then, findings will be categorized based on similarity of meaning. The final step will be through meta-aggregation of the categories to produce a single comprehensive set of synthesized findings that can be used as a basis for evidence-based practice.

Appendix I: Appraisal instruments

MAStARI appraisal instrument

QARI appraisal instrument

NOTARI appraisal instrument

Appendix II: Data extraction instruments

MAStARI data extraction instrument

QARI data extraction instrument

NOTARI data extraction instrument

References