Abstract Pseudohyperkalaemia is defined as a rise in serum potassium with concomitantly normal plasma potassium. The case of long undiagnosed pseudohyperkalaemia in an 84-year-old lady with thrombocytosis post splenectomy is presented. Presenting a historical perspective and the multifactorial aetiology of pseudohyperkalaemia the author underlines the importance of detecting apparent hyperkalaemia by testing the plasma potassium. Awareness of the possible causes of pseudohyperkalaemia increases the likelihood of it being detected earlier thereby decreasing the risk of harming the patient. Unnecessary treatment and investigation of pseudohyperkalaemia can cause harm to the patient in the form of undesired side effects, unnecessary investigations and concerns, and potentially dangerous iatrogenically induced cardiac arrhythmias. pseudohyperkalaemia, thrombocytosis, splenectomy, insulinoma, older people An 84-year-old female was transferred to our ward in a long-term care facility from another ward within the same facility with a diagnosis of dementia with wandering behaviour. The patient was on Calcium Resonium for persistent hyperkalaemia and was refusing the medication as it was causing her constipation. There were no ECG changes. A review of the patient’s history showed that she was a known case of an insulinoma. This was diagnosed 3 years previously after presenting to the emergency department with hypoglycaemia on three separate occasions. A CT scan showed a large vascular mass with cystic components arising from the tail of the pancreas. The patient then underwent a distal pancreatectomy with splencetomy. Soon after the surgery she started having high serum potassium levels and was prescribed the hyperkalaemia regime a number of times with a prescription for calcium resonium upon discharge home. Six months after the surgery the patient was admitted to a long-term care facility in view of her declining health status. The hyperkalaemia persisted and the patient’s potassium was tested for 137 times in 40 months. Upon transfer to our ward, it was noted that the rise in serum potassium coincided with a rise in the platelet count following the splenectomy. The possibility of a pseudohyperkalaemia was put forward and confirmed by a plasma electrolyte measurement. This showed the plasma potassium to be at 4.16 mmol/L as opposed to serum potassium of 6.60 mmol/L on a background of a platelet count of 913 × 106. Hyperaemia is defined as a plasma potassium level exceeding 5.1 mmol/l. Pseudohyperkalaemia is defined as a rise in serum potassium with concomitantly normal plasma potassium. Pseudohyperkalemia needs to be excluded before true hyperkalemia is considered. A number of causes of pseudohyperkalemia have been described in the literature. In total, 59 causes have been listed by Young  as possible causes of pseudohyperkalemia. The role of an increase in the blood cellular components as a cause of pseudohyperkalemia has been described for a long time. These include studies about platelets after centrifugation , from white blood cells in cases of chronic myeloid leukaemia  and from red blood cells . In the 1980s, Moddler and Meuthen  postulated that the lag time between collection and potassium determination could lead to pseudohyperkalemia. Wulkan and Michiels  confirmed the positive correlation between platelet count and serum potassium, but not plasma potassium. Singh et al.  recommended that pseudohyperkalemia should only be considered if serum K+ level exceeds plasma K+ level by 0.4 mmol/l provided that samples are collected under strict techniques, remain at room temperature and are tested within 1 h from blood specimen collection. Fukasawa et al.  suggest that normal counts of activated platelets might also be the cause of pseudohyperkalemia. The multifactorial aetiology of pseudohyperkalemia stems from the possibility of it occurring at the point of blood collection, during the transit time or during storage prior to lab evaluation. Fist clenching, traumatic venepuncture and haemolysis from mechanical trauma have all been implicated at the time of blood collection. The use of vacuum tubes, pneumatic tube transportation, prolonged incubation and re-centrifugation have been implied during the time of transport and storage. Ambient temperature, together with delayed processing and placing the sample for a prolonged period on ice, has also been implicated in the literature. A similar case of pseudohyperkalaemia post splenectomy has been described by Ruddy et al.  in a patient with chronic lymphocytic leukaemia. The early identification of pseudohyperkalaemia as opposed to true hyperkalaemia will help avoid unnecessary harm to the patient including potential death. Unnecessary treatment may lead to potentially dangerous iatrogenically induced hypokalaemia leading to cardiac arrythmyias. Key points Pseudohyperkalaemia is defined as a rise in serum potassium with concomitantly normal plasma potassium. The causes of pseudohyperkalaemia are multifactorial. The early identification of pseudohyperkalaemia will help avoid unnecessary harm to the patient. Conflict of interest None. References 1 Young D. Effects of Preanalytical Variables on Clinical Laboratory Tests . Washington, DC: AACC Press, 1997. 2 Hartmann RC, Melinkoff SM. The relationship of platelets to the serum potassium concentration. J Clin Invest 1955; 34: 938, 1954. 3 Bronson WR, DeVita VT, Carbone PP, Cotlove E. Pseudohyperkalaemia due to release of potassium from white blood cells during clotting. N Engl J Med 1966; 274: 369– 75. Google Scholar CrossRef Search ADS PubMed 4 Nilsson IM, Skanese B, Biorkman SK, Serin F. Platelet function in thrombocytaemia. The effects of platelets and serotonin on serum potassium and bilirubin. Acta Med Scand 1960; 167: 353. Google Scholar CrossRef Search ADS PubMed 5 Moddler B, Meuthen I. Pseudohyperkalaemia in the serum in reactive thrombocytosis and thrombocythaemia. Dtsch Med Wochenschr 1986; 111: 329– 32. Google Scholar CrossRef Search ADS PubMed 6 Wulkan RW, Michiels JJ. Pseudohyperkalaemia in thrombocythaemia. J Clin Chem Clin Biochem 1990; 28: 489– 91. Google Scholar PubMed 7 Singh PJ, Zawada ET, Santella RN. A case of ‘reverse’ pseudohyperkalemia. Miner Electrolyte Metab 1997; 23: 58– 61. Google Scholar PubMed 8 Fukasawa H, Furuya R, Kato A et al. . Pseudohyperkalaemia occurring in a patient with chronic renal failure and polycythaemia Vera without severe leukocytosis or thrombocytosis. Clin Nephrol 2002; 58: 451– 4. Google Scholar CrossRef Search ADS PubMed 9 Ruddy KJ, Wu D, Brown JR. Pseudohyperkalaemia in chronic lymphocytic leukaemia. J Clin Oncol 2008; 26: 2781– 2. Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the British Geriatrics Society. All rights reserved. For permissions, please email: firstname.lastname@example.org This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)
Age and Ageing – Oxford University Press
Published: May 11, 2018
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