A 34-year-old man is brought to the emergency department after a motor vehicle collision. He has blunt abdominal trauma and bilateral femur fractures. The patient has no significant medical history and takes no medications. He does not smoke but drinks 8-12 alcoholic beverages a day. Blood pressure is 80/40 mm Hg and pulse is 110/min. Immediate resuscitation efforts are initiated, during which he receives transfusion of several units of packed red blood cells. During transport to the intensive care unit, the patient reports a tingling sensation in his fingers and toes. Serum ionized calcium level is 4 mg/dL (normal: 4.8-5.5). Which of the following is the most likely cause of this patient's current symptoms?

Question

A 34-year-old man is brought to the emergency department after a motor vehicle collision.  He has blunt abdominal trauma and bilateral femur fractures.  The patient has no significant medical history and takes no medications.  He does not smoke but drinks 8-12 alcoholic beverages a day.  Blood pressure is 80/40 mm Hg and pulse is 110/min.  Immediate resuscitation efforts are initiated, during which he receives transfusion of several units of packed red blood cells.  During transport to the intensive care unit, the patient reports a tingling sensation in his fingers and toes.  Serum ionized calcium level is 4 mg/dL (normal: 4.8-5.5).  Which of the following is the most likely cause of this patient's current symptoms?

Quizplus · Accepted Answer

11ec160b_3cc8_658e_9249_b5b6093d7150_MD0001_00 This patient has symptomatic hypocalcemia (eg, paresthesias) following high-volume blood transfusion. Prior to storage, donated blood is generally mixed with solutions containing citrate anticoagulant. Following transfusion, citrate is rapidly metabolized to bicarbonate in the liver; however, when large volumes of blood are transfused rapidly, the excess citrate can chelate calcium in the plasma, leading to hypocalcemia due to decreased serum ionized calcium concentration. This is most common with very high transfusion rates (eg, >9 units/hr), but it can also be seen at lower rates in patients with underlying hepatic insufficiency (eg, alcohol-associated liver disease). Other complications of high-volume transfusion include depletion of coagulation factors and volume overload. (Choices A and C) Antibody-mediated hemolysis is typically caused by transfusion of ABO-incompatible blood. Characteristic clinical findings include fever, back or flank pain, acute kidney injury, and hemoglobinuria. The primary electrolyte complication is hyperkalemia due to release of intracellular potassium. Hyperkalemia can also be seen due to leakage of potassium from red cells during storage. However, hypocalcemia would not occur in these scenarios. (Choice D) Acute hypocalcemia due to increased renal calcium excretion can be seen in hypoparathyroidism. This is commonly encountered as a complication of thyroid or other neck surgery with inadvertent injury or removal of the parathyroid glands. Abdominal and lower extremity trauma would not affect parathyroid function. (Choice E) Rhabdomyolysis typically presents with muscle pain, red urine (ie, myoglobinuria), and elevated creatine kinase. Release of intracellular phosphate from muscle cells can precipitate calcium salts in damaged muscle and lead to hypocalcemia, but this is typically a delayed finding (24-72 hours after trauma). Educational objective: Citrate anticoagulants in high-volume blood transfusion can chelate plasma calcium, leading to hypocalcemia which causes peripheral neuromuscular excitability (eg, paresthesia, muscle spasms). This is most common with very rapid transfusion rates, but it can also be seen at lower rates in patients with hepatic insufficiency because citrate is metabolized by the liver. __________ References: Hypocalcemia in trauma patients receiving massive transfusion. (http://www.ncbi.nlm.nih.gov/pubmed/27083965)

A 34-Year-Old Man Is Brought to the Emergency Department After