P0008CASE REPORT: METABOLIC ALKALOSIS RESULTING IN RESPIRATORY COMPROMISE IN A PATIENT UNDERGOING HIGH DOSE METHOTREXATE THERAPY

Background and Aims High dose Methotrexate (HDMTX) is an important component of several modern oncological/haematological treatment protocols due to its central nervous system penetrance. Nephrotoxicity represents a significant adverse effect and can limit therapeutic options. Therefore, strategies to prevent this are paramount. Urinary alkalinisation and large volume resuscitation to maintain adequate hydration and urine output are the typical strategies. Urinary alkalinisation prevents tubular precipitation of methotrexate and therefore, a strict urinary pH target of 7 is maintained via a continuous bicarbonate infusion. Method We describe a case report, of Iatrogenic metabolic alkalosis leading to respiratory compromise in a patient receiving HDMTX from Mayo Clinic, Rochester. Results We present the case of a 76-year-old woman with a Diffuse Large B-Cell Lymphoma with CNS involvement who presented for elective admission for her 1st cycle of HDMTX. She received 7g of Methotrexate at dosing of 8 g/m2. She received the standard urinary alkalinisation with pre- and post-hydration. Her baseline HCO3- was 28 mEq/L. Her 48 hour MTX level was elevated at 1.2 so the urinary alkalinisation protocol was continued until <0.1 mcmol/L. On day 4, she developed frequent episodes of apnoea. Her ABG demonstrated a metabolic alkalaemia pH 7.54, pCO 53, pO2 91, HCO3 45. She was transferred to the ICU for close monitoring. Her bicarbonate infusion was discontinued and she received acetazolamide. Her bicarbonate improved to 31 after 12 hours. She had a significant improvement in her respiratory status with no further episodes of apnoea. Her bicarbonate infusion was restarted due to elevated MTX levels. She was discharged home with no further complications. Conclusion Iatrogenic Metabolic alkalosis leading to respiratory compromise represents a rare but important complication of urinary alkalinsation protocols for High-dose Methotrexate therapy.