Anaphylactic Reaction Rates to Blue Dyes Used for Sentinel Lymph Node Mapping: Systematic Review and Meta-analysis

Food Safety and Health Concerns of Synthetic Food Colors: An Update

The toxicity of food additives is widely studied and concerns many consumers worldwide. Synthetic food colors are often considered an unnecessary risk to consumer health. Since the European Food Safety Authority's (EFSA) re-evaluation between 2009 and 2014, the body of scientific literature on food colors has grown, and new evaluations are being published by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Therefore, this narrative review aims to review the toxicological data that have become available since 2014. The reviewed colors are Quinoline Yellow, Sunset Yellow, Azorubine, Amaranth, Ponceau 4R, Erythrosine, Allura Red, Patent Blue, Indigo Carmine, Brilliant Blue FCF, Green S, Brilliant Black, Brown HT, and Lithol Rubine BK. Tartrazine was not included in this paper; the overwhelming amount of recent data on Tartrazine toxicity requires more space than this review can provide. The issues regarding the toxicity of synthetic food colors and real population exposures are being regularly examined and reviewed by relevant authorities, such as the EFSA and JECFA. The current ADI limits set by the authorities are mostly in agreement, and they seem safe. However, the EFSA and JECFA assessments of some of the colors are more than a decade old, and new evidence will soon be required.

Avoiding unnecessary sentinel lymph node biopsy with the use of superparamagnetic iron oxide mapping agents (Magtrace®) in breast surgery

BACKGROUND

Superparamagnetic iron oxide (SPIO) (Magtrace®) is a non-radioactive liquid tracer that can stay in the sentinel lymph nodes for 30 days. Injection of SPIO at time of primary breast surgery where upfront sentinel lymph node biopsy (SLNB) is not immediately indicated allows for a return to theatre if pathology then identifies invasive disease. SLNB is associated with paraesthesia, pain, seroma formation and lymphoedema risk. Hence, our study aims to assess the use of SPIO to avoid upfront SLNB in breast surgery for ductal carcinoma in situ (DCIS) and prophylaxis.

METHODS

Retrospective single-centre study of consecutive patients who underwent injection of SPIO tracer at time of primary breast surgery to avoid upfront SLNB at Chris O'Brien Lifehouse, Sydney, NSW, Australia over a 10-month period.

RESULTS

SPIO was injected 38 times, with 34 at time of mastectomy and four cases at time of wide local excision. The indication for surgery was DCIS in 18 cases, risk reduction in 17 cases and other indications in three patients. Six cases (15.8%) required delayed SLNB (D-SLNB) due to the finding of invasive disease on post-operative histopathology. All patients who underwent D-SLNB had nodes successfully localized with SPIO.

CONCLUSION

In our cohort, 84.2% of cases were able to avoid upfront SLNB, and hence avoid the associated complications of SLNB. SPIO injection was successful in localizing the SLN in all cases at time of surgery for D-SLNB. This technique was safe with few associated complications.

Adverse Clinical Effects Associated With Non-catecholamine Pharmacologic Agents for Treatment of Vasoplegic Syndrome in Adult Cardiac Surgery

Vasoplegic syndrome is a relatively common complication that can happen during and after major adult cardiac surgery. It is associated with a higher rate of complications, including postoperative renal failure, longer duration of mechanical ventilation, and intensive care unit stay, as well as increased mortality. The underlying pathophysiology of vasoplegic syndrome is that of profound vascular hyporesponsiveness, and involves a complex interplay among inflammatory cytokines, cellular surface receptors, and nitric oxide (NO) production. The pharmacotherapy approaches for the treatment of vasoplegia include medications that increase vascular smooth muscle contraction via increasing cytosolic calcium in myocytes, reduce the vascular effects of NO and inflammation, and increase the biosynthesis of and vascular response to norepinephrine. Clinical trials have demonstrated the clinical efficacy of non-catecholamine pharmacologic agents in the treatment of vasoplegic syndrome. With an increase in their use today, it is important for clinicians to understand the adverse clinical outcomes and patient risk profiles associated with these agents, which will allow better-tailored medical therapy.

Fluorescent-guided surgery and the use of indocyanine green sentinel lymph node mapping in the pediatric and young adult oncology population

BACKGROUND

Technetium-99 (99m Tc) lymphoscintigraphy with blue dye injection is an accepted method for sentinel lymph node (SLN) mapping, but blue dye has known adverse effects, and injection of 99m Tc may increase time under anesthesia for pediatric patients. Indocyanine green (ICG) may serve as an adjunct to assist with visibility and identification of SLNs. We hypothesized that sensitivity of ICG was similar to blue dye in SLN biopsies.

METHODS

Thirty patients (36 procedures with 96 total specimens) underwent preoperative intradermal injection of 99m Tc, followed by intradermal injection of isosulfan blue and ICG. Test characteristics of blue dye, ICG, and 99m Tc included sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

RESULTS

ICG had a sensitivity of 87% and PPV of 83% for detection of 99m Tc-hot lymph nodes; blue dye had a sensitivity of 44% and PPV of 97%. For detection of pathologically confirmed lymph nodes, ICG had a sensitivity of 84% and a positive predictive value (PPV) of 91%. 99m Tc had a sensitivity of 82% and a PPV of 94%. ICG had no significant difference in odds of being positive in pathology-confirmed lymph nodes compared to 99m Tc (odds ratio [OR], 0.818; 95% confidence interval [CI], 0.3-2.172; p = .823) and had higher odds than isosulfan blue (OR, 0.025, 95% CI, 0.001-0.148; p < .001).

CONCLUSION

This study established the efficacy of ICG as an adjunct to SLNB in the pediatric and young adult population. ICG was safe, more efficacious than blue dye, and may obviate the need for lymphoscintigraphy in selected patients resulting in reduced time under anesthesia.

Case Report: Isosulfan Blue-Related Anaphylaxis

Anaphylaxis is an acute multisystem syndrome typically resulting from the sudden release of mast cell and basophil-derived mediators into the circulatory system. Isosulfan blue dye is a rare, but known, mediator of anaphylaxis with an incidence between 0.16% and 2% of cases. We report two cases of anaphylaxis attributed to the use of isosulfan blue dye in the intraoperative setting. Both of the patients we report had grade 3 anaphylactic reactions requiring vasopressors to correct significant hypotension. Both patients required overnight monitoring in the intensive care unit with the second patient also requiring continued vasopressor support.

Novel Dual Tracer Indocyanine Green and Radioisotope Versus Gold Standard Sentinel Lymph Node Biopsy in Breast Cancer: The GREENORBLUE Trial

BACKGROUND

The methods for sentinel lymph node (SLN) biopsy in breast cancer have been variable in type and number of tracers. Some units have abandoned the use of blue dye (BD) due to adverse reactions. Fluorescence-guided biopsy with indocyanine green (ICG) is a relatively novel technique. This study compared the clinical efficacy and costs between novel dual tracer ICG and radioisotope (ICG-RI) with "gold standard" BD and radioisotope (BD-RI).

METHODS

Single-surgeon study of 150 prospective patients with early breast cancer undergoing SLN biopsy (2021-2022) using ICG-RI compared with a retrospective cohort of 150 consecutive previous patients using BD-RI. Number of SLNs identified, rate of failed mapping, identification of metastatic SLNs, and adverse reactions were compared between techniques. Cost-minimisation analysis performed by using Medicare item numbers and micro-costing analysis.

RESULTS

Total number of SLNs identified with ICG-RI and BD-RI was 351 and 315, respectively. Mean number of SLNs identified with ICG-RI and BD-RI was 2.3 (standard deviation [SD] 1.4) and 2.1 (SD 1.1), respectively (p = 0.156). There were no cases of failed mapping with either dual technique. Metastatic SLNs were identified in 38 (25.3%) ICG-RI patients compared with 30 (20%) BD-RI patients (p = 0.641). There were no adverse reactions to ICG, whereas four cases of skin tattooing and anaphylaxis were associated with BD (p = 0.131). ICG-RI cost an additional AU$197.38 per case in addition to the initial cost for the imaging system.

CLINICAL TRIAL REGISTRATION

 ACTRN12621001033831.

CONCLUSIONS

Novel tracer combination, ICG-RI, provided an effective and safe alternative to "gold standard" dual tracer. The caveat was the significantly greater costs associated with ICG.

Blue Wheals and Blue Angioedema Induced by Blue Dyes: A Systematic Review

BACKGROUND

Blue wheals and blue angioedema, the adverse reactions to blue dye injections with or without anaphylaxis, are poorly defined.

OBJECTIVE

The objective is to review the characteristics (ie, sex and age at onset, interval between blue dye injection and symptom onset, clinical manifestations, duration of blue wheals or angioedema), natural courses, and treatments of blue dye adverse reactions.

METHODS

A review of the articles published through July 2021 was performed per the Preferred Reporting Items for Systematic Reviews and Meta-Analysis recommendations.

RESULTS

Across 523 patients (175 studies) with any adverse reactions to blue dye injections, wheals, angioedema, or both occurred in 193 patients (36.9%). Of these 193 patients, 68 patients (35.2%) developed blue wheals or angioedema, 118 (61.1%) had ordinary wheals or angioedema (nonbluish), and 7 had both (3.6%). We reviewed 169 patients with available data (99 with ordinary lesions and 70 with blue lesions). Patent blue violet had the highest rate of inducing blue wheals or angioedema (odds ratio 4.9). Almost half of the patients with blue wheals or angioedema developed systemic symptoms; and of those with systemic symptoms, all except 1 progressed to anaphylaxis. On-demand treatments with antihistamines, corticosteroids, and epinephrine were commonly used and effective.

CONCLUSIONS

Using blue dyes can lead to blue wheals or angioedema and systemic reactions. In patients with a history of a severe allergic reaction to a blue dye, repeat administration of a blue dye should be used only after carefully weighing all the risks and benefits.

Patent blue versus methylene blue and indigo carmine as a better dye for chromodiscography: in vitro staining efficacy and cytotoxicity study using bovine coccygeal intervertebral discs

BACKGROUND CONTEXT

Chromodiscography is an integral part of full-endoscopic discectomy (FED), comprising ordinary discography with radiopacity produced by contrast medium and intradiscal stain for visualizing annular defects in the endoscopic field. Nevertheless, concerns remain about the cytotoxicity of the stains used. The study of their staining efficacy is also lacking.

PURPOSE

To evaluate the feasibility of methylene blue, patent blue, and indigo carmine for intradiscal injection, investigate the effectiveness of each dye, and define critical concentration with adequate staining efficacy and tolerable cytotoxicity for use in chromodiscography during FED.

STUDY DESIGN

An experimental in vitro study.

METHODS

Dye stock solutions were prepared from powder. The stock was diluted with culture medium or balanced saline and used for cytotoxicity or intervertebral disc staining assays, respectively. Bovine tails were obtained from the local slaughterhouse and functional spine units of intervertebral discs were acquired by transverse incision at the disc level. Each disc was punctured over the posterolateral aspect using a surgical knife to simulate an annular defect. The intradiscal injection was performed with each dye at different concentrations using a 22G needle from the contralateral aspect of the punctured site. Staining efficacy was quantified using ImageJ software. Primary cells of bovine tails were cultivated in each dye at different concentrations. Cytotoxicity was assessed 24 hours after stain exposure using the CCK-8 toxicity assay.

RESULTS

Staining efficacy and cytotoxicity were proportional to the concentration of tested dyes. Lower limits of concentration producing significant staining efficacy of indigo carmine, methylene blue, and patent blue were 0.25 mg/mL, 0.25 mg/mL, and 0.05 mg/mL, respectively. Compared with controls, concentrations showing significant toxicity for indigo carmine, methylene blue, and patient blue were 1 mg/mL, 0.5 mg/mL, and 2.5 mg/mL, respectively.

CONCLUSIONS

Patent blue can serve as a more suitable tissue stain than either indigo carmine or methylene blue due to the widest range of tradeoff concentration within 0.05 to 2.5 mg/mL.

CLINICAL SIGNIFICANCE

Patent blue with the characteristic of good staining efficacy and lower cytotoxicity may be a promising option for chromodiscography during FED.

Omitting Sentinel Lymph Node Biopsy after Neoadjuvant Systemic Therapy for Clinically Node Negative HER2 Positive and Triple Negative Breast Cancer: A Pooled Analysis

Recent advances in systemic treatment for breast cancer have been underpinned by recognising and exploiting subtype-specific vulnerabilities to achieve higher rates of pathologic complete response (pCR) after neo-adjuvant systemic therapy (NAST). This down-staging of disease has permitted safe surgical de-escalation in patients who respond well. Triple-negative (TNBC) or HER2-positive breast cancer is most likely to achieve complete radiological response (rCR) and pCR after NAST. Hence, for selected patients, particularly those who are clinically node-negative (cN0) at diagnosis, the probability of disease in the sentinel node after NAST could be low enough to justify omitting axillary surgery. The aim of this pooled analysis was to determine the rate of sentinel node positivity (ypN+) in patients with TNBC or HER2-positive breast cancer who were initially cN0, achieving rCR and/or pCR in the breast after NAST. MedLine was searched using appropriate search terms. Five studies (N = 3834) were included in the pooled analysis, yielding a pooled ypN+ rate of 2.16% (95% CI: 1.70-2.63). This is significantly lower than the acceptable false negative rate of sentinel lymph node biopsy (SLNB) and supports consideration of omission of SLNB in this subset of patients.

Sentinel Lymph Node Techniques in Urologic Oncology: Current Knowledge and Application

Lymph node (LN) metastases have a significant negative impact on the prognosis of urological malignancies. Unfortunately, current imaging modalities are insufficient when it comes to detecting micrometastases; thus, surgical LN removal is commonly used. However, there is still no established ideal lymph node dissection (LND) template, leading to unnecessary invasive staging and the possibility of missing LN metastases located outside the standard template. To address this issue, the sentinel lymph node (SLN) concept has been proposed. This technique involves identifying and removing the first group of draining LNs, which can accurately stage cancer. While successful in breast cancer and melanoma, the SLN technique in urologic oncology is still considered experimental due to high false-negative rates and lack of data in prostate, bladder, and kidney cancer. Nevertheless, the development of new tracers, imaging modalities, and surgical techniques may improve the potential of the SLN procedures in urological oncology. In this review, we aim to discuss the current knowledge and future contributions of the SLN procedure in the management of urological malignancies.

Perioperative Hypersensitivity Evaluation and Management: A Practical Approach

Perioperative hypersensitivity (POH) is an uncommon, potentially life-threatening event. Identification of POH can be difficult given the lack of familiarity, physiological effects of anesthesia, draping of the patient during surgery, and potential nonimmunological factors contributing to signs and symptoms. Given the unique nature and large number of medications administered in the perioperative setting, evaluation of POH can be challenging. In this paper, we present a practical approach to management with an emphasis on understanding what happens in the operating room, the overlap of signs and symptoms between nonimmunological and immunological reactions, acute management, and subsequent evaluation. In addition, we provide a strategy for further review of an initially negative evaluation and emphasize the importance of establishing management plans for the patient as well as providing recommendations to the medical, anesthesia, and surgical teams for future surgeries. A critical factor for successful management at all points in the process is a close collaboration between the anesthesia and the allergy teams.

Sentinel Lymph Node Biopsy by Lymphatic Flare Technique: a Feasibility Study-"The FLAIR Is in the FLARE"

Background

Sentinel lymph node (SLN) biopsy is a standard procedure in evaluating the status of node negative axilla. Numerous techniques have been described in literature. We hereby describe a new technique of intradermal injection of blue dye called the lymphatic flare technique.

Methods

The study was conducted in two phases over a year from August 2020 to May 2021with an internal audit to validate and standardize the technique in January 2021.

Results

Between August 2020 and December 2020, 32 patients were evaluated for validation of this technique by two senior surgeons, which yielded a SLN identification rate of 93.75% (30 out of 32). After validating, standardizing, and educating the entire surgical team of the technique, another consecutive 27 patients were evaluated. The SLN identification rate increased to 100% (27 out of 27). Overall, SLN positivity for cancer was 16.6% (10 out of 60).

Conclusion

SLN identification by the lymphatic flare technique is feasible, accurate, and reproducible.

Long lasting effect on testes following methylene blue injection in laparoscopic lymphatic sparing varicocelectomy

OBJECTIVE

Injection of methylene blue to testis has been shown to have adverse effect in animal studies but it is still being used frequently as lymphatic mapping agent during lymphatic sparing varicocelectomy in adolescent varicoceles. We aim to report postoperative ultrasound changes after subaortic injection of methylene blue in human testes.

STUDY DESIGN

A retrospective observational study of consecutive patients under 18 years old undergoing laparoscopic varicocelectomy from August 2017 to August 2021 was performed. Demographics such as age, symptoms, pre-operative testicular volume was collected. Primary outcome was change on testicular ultrasound at 3, 6, 12 months after the operation. Secondary outcome was testicular volume difference between affected and unaffected testes, and growth rate of affected testis at 1 year after the operation.

RESULTS

Fifty-eight patients were included, with median age of 15 years old (IQR 11-18 years). Thirty-one patients had non-lymphatic sparing varicocelectomy (Group A) and 27 patients had lymphatic sparing varicocelectomy (Group B). There was no statistical difference between the mean testicular volume difference between the two groups, but hydrocele rate was significantly higher in Group A (16% vs 0%, p = 0.03). In group B, 6 patients (22.2%, p = 0.005) developed testicular change detectable by ultrasound. No statistical difference could be demonstrated for median testicular size difference (between affected and unaffected testes) at 1 year between group with and without ultrasound change (-23% vs 0%, p = 0.36). Median follow up time was 20.4 months (IQR 5-32 months).

DISCUSSION

Varicocele treatments improve testicular volume and increase total sperm concentration and lymphatic sparing surgery significantly decreased post-operative hydrocele rates [2]. Different agents have been used to delineate lymphatic vessels and one commonly used agent is methylene blue [10,15-16]. However it has been shown in other animal studies that intraparenchymal injection of methylene blue to rat testis result in degenerative changes [18]. Our study is the first to describe post-operative changes of human testes on imaging after lymphatic sparing varicocelectomy with subdartoic injection of methylene blue. Six patients (22.2%) demonstrated new onset testicular changes on post-operative ultrasound. Although no statistically significant testicular volume reduction was seen in the group with change on imaging, these observations may serve as a surrogate marker for testicular injury or reduced testicular function. It will be desirable for future studies if we can investigate it further with hormonal markers or semen analysis after puberty has been reached.

CONCLUSION

Lymphatic sparing procedure reduced post-operative hydrocele in adolescent varicocele, however long-lasting effect on testis is evident with subdartoic injection of methylene blue. This agent must be used with caution and long term follow up of these patients are needed.

Sentinel Lymph Node Mapping: Current Applications and Future Perspectives in Gynecology Malignant Tumors

The sentinel lymph nodes (SLNs) is a group of lymph nodes initially involved in the metastatic spread of cancer cells. SLN mapping refers to intraoperative localization and biopsy of SLNs with specific tracers to assess lymph node metastases. It is widely used in a variety of tumor surgeries for its high sensitivity and high negative predictive value. In the evaluation of the status of lymph node metastases in gynecological malignancies, it has received increasingly more attention due to its minor invasiveness, few complications, and high diagnosis rate. The National Comprehensive Cancer Network (NCCN) guidelines provide an excellent introduction to the indications and methods of SLN techniques in vulvar, cervical, and endometrial cancers, but they provide little explanation about some specific issues. In this review, we summarize different dyes and injection methods and discuss the indications of application and the clinical trials of SLN mapping in gynecological malignant tumors, aiming to provide a reference for the rational application of sentinel techniques in gynecology malignant tumors before relevant guidelines are updated.

Ventricular Infusion and Nanoprobes Identify Cerebrospinal Fluid and Glymphatic Circulation in Human Nerves

Growing evidence suggests that cerebrospinal fluid circulates in human nerves. Several conditions encountered by the plastic surgeon may be related to dysregulation of this system, including nerve transection, stretch injuries, and peripheral neuropathy. The purpose of this study was to show how ventricular infusion and nanoprobes identify CSF and glymphatic circulation in neural sheaths of human nerves.

METHODS

The technique of ventricular infusion using buffered saline was developed in 2017. The technique was used in a series of eight fresh cadavers before dissection of the median nerve, and combined with fluorescent imaging and nanoprobe injections in selected specimens.

RESULTS

Eight cadaver specimens underwent ventricular infusion. There were six female and two male specimens, ages 46-97 (mean 76.6). Ventricular cannulation was performed successfully using coordinates 2 cm anterior to coronal suture and 2.5 cm lateral to sagittal suture. Depth of cannulation ranged from 44 to 56 mm (mean 49.7). Ventricular saline infusion complemented by nanoprobe injection suggests CSF flows in neural sheaths, including pia meninges, epineurial channels, perineurium, and myelin sheaths (neurolemma).

CONCLUSIONS

Ventricular infusion and nanoprobes identify CSF flow in neural sheaths of human nerves. CSF flow in nerves is an open circulatory system that occurs via channels, intracellular flow, and cell-to-cell transport associated with glial cells. Neural sheaths, including neurolemma, may participate in glucose and solute transport to axons. These techniques may be used in anatomic dissection and live animal models, and have been extended to the central nervous system to identify direct ventricle-to-pia meninges CSF pathways.

Sentinel Node Methods in Penile Cancer - a Historical Perspective on Development of Modern Concepts

Malignant penile tumors are of squamous cell origin in more than 95% of cases and the occurrence of a distant metastasis without prior inguinal lymph node metastatic deposits is very rare. This makes inguinal lymph node staging very reliable and of great prognostic significance since undiscovered and untreated inguinal metastases may lead to a fatal clinical course. In lack of a sufficiently accurate noninvasive lymph node staging modality, penile cancer relies on surgical lymph node removal for regional staging. In this respect sentinel node biopsy offers a favourable minimally invasive alternative to prophylactic inguinal lymph node dissection which is associated with significant surgery-related morbidity. Today sentinel node biopsy is widely used in surgical oncology within high volume cancers such as breast cancer and melanoma. In rare cancers sentinel node biopsy is also emerging as a minimal invasive staging tool in patients with no obvious lymph node involvement. At several specialized units across Europe sentinel node biopsy has been practiced by dedicated specialist within vulva and penile cancer for more than two decades. In fact, the rare disease penile cancer was a model entity for development of the original sentinel node concept as early as the 1970'es due to work by the Paraguayan penile cancer pioneer, Cabañas, the sentinel node concept was subsequently successfully adapted in breast cancer and melanoma. This turned out mutually beneficial since the sequential development of sentinel node biopsy in penile cancer in the 1990s eventually adopted new insights and added conceptual details from the experiences harvested in the broader clinical application possible in these high-volume diseases. The prerequisite to conceptualising the sentinel node approach was the gradual anatomical and functional understanding of the lymphatic system which in western medicine rooted in ancient Greece and gradually increased in details and comprehension with significant contributions from many great notabilities during the last centuries including Hippocrates, Galen, Fallopio, Malpighi, Virchow, Starling, Cabañas, Hodgkin and Horenblas. Sentinel node biopsy in penile cancer is a complex multimodality procedure involving inguinal ultrasonography by radiologists, precise tracer-injection and interpretation of nuclear images by nuclear medicine physicians, radio-tracer- and dye guided open surgical biopsies by urologists and thorough step-sectioning, immunostaining and accurate lymph node specimen analysis by pathologists. This team effort requires well-tested protocols, experience and good collaboration and in rare diseases this calls for centralization of service.

Does failed mapping predict sentinel lymph node metastasis in cN0 breast cancer?

Aims: The clinical significance of nonvisualized sentinel lymph nodes (non-vSLNs) is unknown. The authors sought to determine the incidence of non-vSLNs on lymphoscintigraphy, the identification rate during surgery, factors associated with non-vSLNs and related axillary management. Patients & methods: A total of 30,508 consecutive SLN procedures performed at a single institution from 2000 to 2017 were retrospectively studied. Associations between clinicopathological factors and the identification of SLNs during surgery were assessed. Results: Non-vSLN occurred in 525 of the procedures (1.7%). In 73.3%, at least one SLN was identified intraoperatively. Nodal involvement was only significantly associated with SLN nonidentification (p < 0.001). Conclusion: Patients with non-vSLN had an increased risk for SLN metastasis. The detection rate during surgery was consistent, reducing the amount of unnecessary axillary dissection.

A retrospective analysis of rates of allergic reaction to Patent V blue dye used in sentinel lymph node biopsies for melanoma

Sentinel lymph node biopsies are a well-established component of the assessment and treatment pathway for patients with cutaneous melanoma in the UK. Commonly utilised techniques involve the use of blue dye which has an established risk of inducing allergic reactions in patients. Such reactions can be life-threatening, and this risk is important to highlight to patients. We conducted a retrospective review of all patients who had undergone this procedure at our melanoma centre in Cambridge, UK. From a group of 715 patients who received blue dye as part of the procedure, six patients suffered an allergic reaction (0.84%) with one of these treated as anaphylaxis. Our incidence of anaphylaxis is almost ten times greater than that reported in the NAP6 report led by the National Institute of Academic Anaesthesia and significantly higher than reported by others. We propose several reasons why our results differ from previous estimates. This study has focused only on patients undergoing a sentinel node procedure for melanoma, others have focused on such procedures performed on patients with breast cancer and some have combined the two. The administration technique, volume and anatomical distribution of disease all differ significantly from melanoma, possibly influencing rates and severity of allergic reactions.