title: Falsely raised whole blood chloride caused by systemic absorption of cerium nitrate cream for burns.
abstract: Whole blood, serum or plasma chloride is almost exclusively measured by potentiometry with an ion-selective chloride electrode which utilizes membrane selectivity to chloride ions. Other anions such as bromide, iodide and thiosulphate can interfere but usually are not present in high enough concentration to cause significant cross reactivity. A patient from our burns unit had serial chloride measurements on a Radiometer ABL800 blood gas analyser. The results were higher in contrast to plasma measurements on the Abbott Architect Ci8200, which were within reference intervals and in line with the patient's pathophysiological status. This indicated a likely interference with the blood gas analyser chloride estimation. The chloride results on the ABL800 for 3rd, 4th and 5th day after the burn accident were 170, 137 and 119 mmol/L. Corresponding plasma chloride results on the Ci8200 were all around 105 mmol/L. Nitrate was found to be markedly elevated in these samples, and the results were 6.7, 4.9 and 1.1 mmol/L, respectively (reference limit < 0.08 mmol/L). To further demonstrate nitrate was the causative agent, pooled plasma spiked with 7 mmol/L of sodium nitrate caused a rise in the ABL800 chloride from 105 to 202 mmol/L. Later we confirmed that the patient was topically medicated with cerium nitrate cream (Flammacerium®, Sinclair IS Pharma, UK) for his burns. In summary, the results clearly indicated nitrate was the interferent with the ABL800 chloride estimation and the source was the topical burns cerium nitrate cream.
authors.affiliation: Department of Chemical Pathology, Middlemore Hospital, Auckland, New Zealand leah.ha@middlemore.co.nz.
authors.forename: Leah Y
authors.initials: LY
authors.lastname: Ha
authors.affiliation: Department of Specialist Chemical Pathology, Auckland City Hospital, Auckland, New Zealand.
authors.forename: Gerald A
authors.initials: GA
authors.lastname: Woollard
authors.affiliation: Department of Chemical Pathology, Middlemore Hospital, Auckland, New Zealand Department of Specialist Chemical Pathology, Auckland City Hospital, Auckland, New Zealand.
authors.forename: Weldon W
authors.initials: WW
authors.lastname: Chiu
mesh_terms: D000279:Administration, Cutaneous; D000891:Anti-Infective Agents, Local / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D002056:Burns / Q000097:blood / Q000188:drug therapy* / Q000628:therapy; D002563:Cerium / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D002648:Child; D002713:Chlorine / Q000097:blood; D003131:Combined Modality Therapy; D004338:Drug Combinations; D005189:False Positive Reactions; D017809:Fatal Outcome; D006801:Humans; D008297:Male; D009566:Nitrates / Q000097:blood*; D012837:Silver Sulfadiazine / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use; D012869:Skin Absorption; D063465:Skin Cream / Q000493:pharmacokinetics* / Q000627:therapeutic use; D015854:Up-Regulation
chemical_list: D000891:Anti-Infective Agents, Local; D004338:Drug Combinations; D009566:Nitrates; C046337:cerous nitrate, sulfadiazine silver drug combination; D002563:Cerium; D002713:Chlorine; D012837:Silver Sulfadiazine
keywords: Chloride ion-selective electrode; interference; nitrate