Hyperkalaemia following blood transfusion

A 35-year-old man weighing 63 kg was presented for elective repair of an atherosclerotic thoraco-abdominal aortic aneurysm. He was a known hypertensive on oral nifedipine 20 mg 12 hourly and propranolol 20 mg 8 hourly. He had no known allergies. Routine biochemistry (Na+ 135 mmol/l, K+ 3.6 mmol/l, urea 5.1 mmol/l, creatinine 56 μmol/l) and haematological investigations were within normal limits. Echocardiography suggested normal left ventricular function and the electrocardiogram (ECG) was normal. An aortogram demonstrated a fusiform aneurysm extending from the descending thoracic aorta (distal to the left subclavian artery) to just distal to the renal arteries. After anaesthetising the patient, the aneurysm was exposed using a thoraco-abdominal incision. Mannitol 0.5 g/kg and heparin 1 mg/kg were given before aortic cross-clamping. No temporary arterial shunts were used during the aortic cross-clamping and the total cross-clamped time was 65 min. On declamping, the patient developed severe hypotension (a systolic pressure of 40 mmHg), which was treated with rapid transfusion of 1 litre of crystalloids, 1 litre of colloids, 4 units of warmed CPD-A (citrate-phosphate-dextrose-adenine) stored whole blood and 10 ml of 10% calcium gluconate. Despite this, the hypotension persisted; therefore the aorta was reclamped (supra-coeliac) to maintain the blood pressure and coronary perfusion. This was immediately followed by bradycardia, widening of QRS complexes and ventricular fibrillation (VF). The VF did not respond to two internal DC shocks of 20 J each and one DC shock of 30 J. Internal cardiac massage was started; the heart was found to be very flabby. Intravenous lignocaine (2 mg/kg) and additional doses of calcium gluconate (10 ml of 10%) and 7.5% sodium bicarbonate 100 ml produced no improvement. In view of the VF resistant to DC shock and a ‘flabby’ heart, hyperkalaemia was suspected. Blood transfusion was discontinued, even though the haemoglobin was 7 g/dl and the hypovolaemia was treated by infusing crystalloid and colloid solutions only. The patient's blood was analysed for serum potassium, which was 7.0 mmol/l. The blood used for transfusion was noted to be 16 days old and biochemical analysis of the unwarmed bag blood showed a pH= 6.803, standard bicarbonate content 7.8 mmol/l, base deficit 20.1 mmol and potassium 16.6 mmol/l.