Recurrent intradialytic heparin induced anaphylaxis: workup and management
A 70-year-old Chinese female with hypertensive kidney disease was deemed to require dialysis. She had no known allergies and never received angiotensin converting enzyme (ACE) inhibitors. Dialysis was commenced through a permanent catheter with 500 U of unfractionated heparin/hr for intradialytic anticoagulation. She tolerated 3 hemodialysis sessions per-week in the initial 2 weeks. The following week she developed hypotension and dyspnea at the start of a dialysis session. First use syndrome was the postulated cause and she was discharged after observation and treatment with intravenous hydrocortisone and antihistamines. However, she mounted a more severe reaction within minutes of starting the subsequent dialysis session two days later, with flushing, hypotension and rhonchi, requiring admission to the high dependency unit. A serum tryptase level by fluorescent enzyme immunoassay done immediately after the reaction was elevated at 43.1 µg/L (ref <11.4 µg/L). Heparin was thought to be the common inciting agent and the cause for her recurrent anaphylaxis. Furthermore, although no subsequent dialysis sessions with heparin were carried out, she developed urticaria on the following day. As heparin was used in the central catheter lock solution, it was postulated that systemic extension of heparin from within the tubing was responsible for this particular reaction. She was subsequently able to tolerate heparin-free dialysis, lending support to our hypothesis that heparin was indeed the culprit. In addition, citrate substituted heparin as catheter lock solution, and no further reactions were observed. Other variables, including the dialysis membrane and sterilant, were not modified. Further evaluation to confirm the suspected heparin allergy and determine safe alternatives for subsequent hemodialysis was indicated.\nSkin prick tests were done with unfractionated heparin (5,000 U/mL), and its possible alternatives: dalteparin (2,500 U/mL), enoxaparin (20 mg/0.2 mL), tinzaparin (3,500 IU/0.35 mL) and fraxiparin (2,850 IU/0.35 mL) (). Histamine (0.1 mg/mL) and 0.9% normal saline solution were used as positive and negative controls. The prick test was positive for heparin but negative for the rest. This was further substantiated by a positive intradermal test with heparin at 1:10 dilution of the above concentration (negative at 1:1,000 and 1:100). Intradermal tests were negative for dalteparin at similar dilutions (1:1,000, 1:100 and 1:10). This was followed by subcutaneous and intravenous challenges with dalteparin at incremental concentrations as described in , reaching up to 1,250 U of intravenous dalteparin. She has tolerated hemodialysis with dalteparin for the past 2 years.