Transfusion and tetany

Case: 54 years old male with a history of alcoholic cirrhosis was brought to the Emergency Department (ED) after a fall and found to have an intracranial bleed. INR was noted to be 6.5. Neurology service wrote for FFP (fresh frozen plasma) and IV Vitamin K. The Patient was admitted to the ICU after neurosurgery decided to go for non-surgical management. At admission, the patient's mental status seems appropriate, but 4 hours after admission, you have been called as the patient was noted to have seizures by bedside staff. On arrival, you noticed the patient having tetany, but he responded appropriately to your questions. Citrate-induced electrolyte imbalance is suspected. Citrate may cause? (select one)

A) hypocalcemia

B) Hypomagnesemia

C) Both

Answer: C

Citrate is usually used in blood products as an anticoagulant. It binds to free calcium to form soluble calcium citrate, thereby lowering the free (ionized) but not the total serum calcium concentration. It is important to check the ionized calcium instead of total serum calcium. The slower infusion rate has shown significantly less ionized calcium reduction than the higher infusion rates.

Prophylactic calcium infusion is not recommended with each blood product transfusion unless clinically indicated. Citrate is normally rapidly excreted by the liver, and transient hypocalcemia is not necessary to treat. However, when a patient receives more than 1 unit of erythrocytes/blood product every 5 minutes or the capacity of the liver to metabolize citrate effectively is exceeded (like in our patient above with cirrhosis), the associated hypocalcemia can cause depressed ventricular contractility and decreased peripheral vascular resistance, causing arrhythmias, hypotension and neurologic symptoms of tetany.

Moreover, citrate binds to magnesium, which may also result in clinically significant hypomagnesemia.

#electrolytes

#transfusion

#neurology

#hepatology

References: 

1. Hall C, Nagengast AK, Knapp C, Behrens B, Dewey EN, Goodman A, Bommiasamy A, Schreiber M. Massive transfusions and severe hypocalcemia: An opportunity for monitoring and supplementation guidelines. Transfusion. 2021 Jul;61 Suppl 1:S188-S194. doi: 10.1111/trf.16496. PMID: 34269436.

2. Byerly S, Inaba K, Biswas S, Wang E, Wong MD, Shulman I, Benjamin E, Lam L, Demetriades D. Transfusion-Related Hypocalcemia After Trauma. World J Surg. 2020 Nov;44(11):3743-3750. doi: 10.1007/s00268-020-05712-x. Epub 2020 Jul 30. PMID: 32734451; PMCID: PMC7391918.

3. McLellan BA, Reid SR, Lane PL. Massive blood transfusion causing hypomagnesemia. Crit Care Med. 1984 Feb;12(2):146-7. doi: 10.1097/00003246-198402000-00014. PMID: 6697734.