Endocrine Abstracts

A 33 year-old-lady presented to the emergency department with acute abdominal pain and per vaginal bleeding. Her last menstrual period was six weeks prior to admission. She had a positive urine pregnancy test and a trans-vaginal ultrasound confirming an ectopic tubal pregnancy. She underwent an emergency laparoscopic right salpingectomy under general anaesthesia with blood loss intra-operatively of 300 ml. One day post-op, her haemoglobin dropped from 129 g/l to 86 g/l. She received 1unit of blood, transfused over 2 hours. Post-blood transfusion, she reported tingling over her hands and perioral area, with acute carpopedal spasm. She had no personal or family history of calcium disorders. She was hypocalcaemic with an adjusted serum calcium 2.07 mmol/l (2.2–2.6) and ionised calcium 1.01 mmol/l (1.13.1.32), phosphate 0.27 mmol/l (0.8–1.5), magnesium 0.91 mmol/l (0.7–1.0) and PTH 4.3 pmol/l (1.6–7.2). Her arterial blood gas showed: pH 7.64, PCO2 2.4kPa, HCO3 17 mmol/l and raised lactate of 4.9 mmol/l, consistent with a respiratory alkalosis superimposed on an underlying metabolic acidosis. She was treated with IV calcium gluconate, IV magnesium and phosphate; after two-cycles of this therapy her symptoms resolved with her adjusted calcium normalised to 2.20 mmol/l and phosphate to 1.25 mmol/l. Hypocalcaemia following large volume transfusions is well-reported. This is driven by large amounts of citrate in transfusions binding calcium. This tends not to occur with low volumes of blood due to prompt removal of citrate by the liver. This case is novel in that only a single unit of blood precipitated the hypocalcaemia, due to a superimposed respiratory alkalosis lowering ionised calcium. We highlight that certain patients (rapid transfusions, alkaloses) are at increased risk of hypocalcaemia following even low volume blood transfusions. Therefore it may be beneficial to monitor serum calcium with a low threshold for ionised calcium to ensure prompt detection of this phenomenon.