Successful intravenous heparin administration during coronary revascularization surgery in a patient with alpha-gal anaphylaxis history

Alpha-Gal Syndrome and Cardiac Surgery

Galactose-alpha-1,3-galactose (alpha-gal) is a carbohydrate expressed by all mammals except for humans and certain old-world primates. It can be found in a plethora of products derived from mammals, including milk, organs, skeletal muscle and gelatin, in addition to products prepared with mammalian cells or constituents. In the late 2000s, an association between tick bites and the development of immunoglobulin E antibodies to the alpha-gal carbohydrate was discovered. The term "alpha-gal syndrome" (AGS) was then coined to describe allergic reactions to mammalian meat or other alpha-gal-containing products derived from mammals. Symptoms are often delayed several hours from consumption and can be urticarial and/or gastrointestinal. Medications and bioprosthetic inserts derived from mammals were also noted to cause allergic reactions in affected patients. Cardiac surgery, in particular, is considered high risk, given that unfractionated heparin has a bovine or porcine origin and is administered in large doses for cardiopulmonary bypass. Bioprosthetic valves have similar origins and risks. Awareness of AGS in cardiac surgery patients can lead to decreased risk preoperatively and inform management perioperatively and postoperatively. In this narrative review, we have reviewed the published literature relevant to AGS in patients undergoing cardiac surgery and shared our treatment approach.

Heparin desensitisation prior to cardiopulmonary bypass in a patient with alpha-gal allergy

This case report describes the implementation of a heparin desensitisation strategy for a patient with confirmed galactose-alpha-1,3-galactose (alpha-gal) allergy, prior to cardiac surgery. We describe the pre-, intra- and postoperative management. We believe this report can enhance the limited data currently in existence on alternative strategies for heparin utilisation in cardiopulmonary bypass in a previously intolerant patient population.

A retrospective evaluation of heparin product reactions in patients with alpha-gal allergies

BACKGROUND

Alpha-gal allergy, also known as red meat allergy or alpha-gal syndrome, can present after bites of certain tick species that contain galactose-alpha-1,3-galactose (alpha-gal) carbohydrate. Following this exposure, patients may develop an allergic reaction after mammalian meat consumption. Some heparin products are derived from porcine intestinal tissue, and it is therefore possible that administering these medications to a patient with an alpha-gal allergy may trigger a reaction.

OBJECTIVE

The purpose of this study was to evaluate the incidence of reactions to porcine heparin products in patients with an alpha-gal allergy.

METHODS

A retrospective case series was conducted by review of electronic medical record data. Patients included were between the ages of 18 and 89 years, with a documented alpha-gal or red meat allergy and an admission to a hospital in the Sentara Healthcare system. The primary outcome was the incidence of allergic reactions upon exposure to heparin products in patients with a documented alpha-gal allergy.

RESULTS

Patients with a documented alpha-gal allergy received a heparin product in 57 of 158 hospital visits (36.1%). Heparin products were tolerated in 56 of the 57 visits (98.3%). The incidence of an alpha-gal reaction to unfractionated heparin was 2.6% (1/39) while the incidence of an alpha-gal reaction to enoxaparin was 0% (0/22).

CONCLUSION AND RELEVANCE

Heparin products were associated with a low incidence of alpha-gal reactions among patients with documented alpha-gal allergy. It is possible that enoxaparin poses less of a risk for reaction in these patients compared to unfractionated heparin.

IgE-mediated food allergy throughout life

Food allergy (FA) has become an increasing problem throughout the world. Over the last 2 decades, the frequency of FA has increased in both children and adults. The prevalence differs according to the research methodology, age, and geographic regions, ranging between 2.0% and 10.0%. The most common form of FA is immunoglobulin E (IgE)-mediated FA. In this form, patients may present with life-threatening conditions, such as anaphylaxis, or milder conditions, such as urticaria, angioedema, sneezing, and nausea alone. The gold standard in the diagnosis of FA is oral provocation tests. Epidermal skin prick tests and specific IgE measurements, as well as component-resolved diagnostic techniques are helpful in the diagnosis and follow-up of patients. In this review, the epidemiology, diagnosis, follow-up, and prognosis of IgE-mediated FA in children and adults were discussed and some specific forms of FA, such as pollen FA syndrome, alpha-gal allergy, and food-dependent exercise-induced anaphylaxis were explained.

Safety of Intravenous Heparin for Cardiac Surgery in Patients With Alpha-Gal Syndrome

BACKGROUND

Alpha-gal syndrome is a tick-acquired disease caused by immunoglobulin E (IgE) to the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal), causing allergic reactions to meat and products sourced from nonprimate mammals. As heparin is porcine-derived, we hypothesized that patients with alpha-gal syndrome who received high-dose heparin for cardiac surgery would have increased risk of anaphylaxis.

METHODS

All cardiac surgery patients at an academic medical center from 2007 to 2019 were cross-referenced with research and clinical databases for the alpha-gal IgE blood test. Clinical data were obtained through the institutional Society of Thoracic Surgeons Adult Cardiac Database and chart review. Patients were stratified by development of an allergic reaction for univariate statistical analysis.

RESULTS

Of the 8819 patients, 17 (0.19%) had a positive alpha-gal test before cardiac surgery. Of these 17 patients, 4 (24%) had a severe allergic reaction. The median alpha-gal titer was significantly higher in patients with a reaction (75 [interquartile range, 61-96] IU/mL vs 8 [interquartile range, 3-18] IU/mL; P = .006). There were no differences in median heparin loading dose, total dose, or maximum activated clotting time (all P > .05). In a subgroup of 8 patients with recent alpha-gal IgE level, 4 (50%) developed an allergic reaction.

CONCLUSIONS

Although alpha-gal is rare in patients undergoing cardiac surgery, there is up to a 50% risk of serious allergic reaction to heparin for cardiopulmonary bypass. Higher preoperative alpha-gal titers may confer a higher risk of severe allergic reaction. For patients with a clinical suspicion of alpha-gal syndrome, we recommend prescreening with IgE levels and premedicating before receiving high doses of intravenous heparin.

Diagnosis and Management of Patients with the α-Gal Syndrome

The galactose-α-1,3-galactose (α-Gal) syndrome has many novel features that are relevant to diagnosis and management. In most cases, the diagnosis can be made on a history of delayed allergic reactions to mammalian meat and the blood test for IgE to the oligosaccharide α-Gal. In general, the diagnosis also dictates the primary treatment, that is, avoiding mammalian meat and also dairy in some cases. In the United States, the lone star tick is the primary cause of this disease, but different ticks are responsible in other countries. Blood levels of IgE to α-Gal often drop in patients who avoid recurrent tick bites, but the rate of decline is variable. Similarly, the delay before reactions is variable and the severity of the allergic reactions is not predicted by the delay or the titer of specific IgE. Some mammalian-derived products such as heart valves, gelatin-based plasma expanders, and pancreatic enzymes are relevant to only select patient groups. A minority of cases may benefit from avoiding a wide range of products that are prepared with mammalian-derived constituents, such as gelatin. This review focuses on the nature of the syndrome, common challenges in diagnosis and management, and also gaps in our current knowledge that would benefit from additional investigation.