Tomas Salek

Intermittent hemodialysis is superior to continuous veno-venous hemodialysis/hemodiafiltration to eliminate methanol and formate during treatment for methanol poisoning

During an outbreak of methanol poisonings in the Czech Republic in 2012, we were able to study methanol and formate elimination half-lives during intermittent hemodialysis (IHD) and continuous veno-venous hemodialysis/hemodiafiltration (CVVHD/HDF) and the relative impact of dialysate and blood flow rates on elimination. Data were obtained from 11 IHD and 13 CVVHD/HDF patients. Serum methanol and formate concentrations were measured by gas chromatography and an enzymatic method. The groups were relatively comparable, but the CVVHD/HDF group was significantly more acidotic (mean pH 6.9 vs. 7.1 IHD). The mean elimination half-life of methanol was 3.7 and formate 1.6 h with IHD, versus 8.1 and 3.6 h, respectively, with CVVHD/HDF (both significant). The 54% greater reduction in methanol and 56% reduction in formate elimination half-life during IHD resulted from the higher blood and dialysate flow rates. Increased blood and dialysate flow on the CVVHD/HDF also increased elimination significantly. Thus, IHD is superior to CVVHD/HDF for more rapid methanol and formate elimination, and if CVVHD/HDF is the only treatment available then elimination is greater with greater blood and dialysate flow rates.

Is the Measurement of Serum Formate Concentration Useful in the Diagnostics of Acute Methanol Poisoning? A Prospective Study of 38 Patients

The aim of this article was to study the role of serum formate (S‐formate) in diagnosing methanol poisoning. A prospective study was undertaken of 38 patients from the Czech methanol mass poisoning in 2012 – median age 51 [interquartile range (IQR) 37–62] years with confirmed methanol poisoning. S‐formate was measured enzymatically. The receiver operating characteristics (ROC) curve was used to examine the predictive ability of S‐formate. Asymptomatic patients had median S‐formate of 1.9 (IQR 1.5–2.4) mmol/L. The median S‐formate was 15.2 (IQR 13.9–17.6) mmol/L in symptomatic subjects with visual disturbances, 15.4 (12.1–18.0) mmol/L in subjects with dyspnoea and 15.7 (IQR 12.8–18.5) mmol/L in comatose patients. The differences in serum formate concentrations in symptomatic patients depending on clinical features were not significant (all p > 0.05). Patients with long‐term visual sequelae of poisoning had median S‐formate of 16.1 (IQR 14.3–19.9) mmol/L; with central nervous system (CNS) sequelae, patients had 15.9 (IQR 14.2–19.5) mmol/L. In lethal cases, the median S‐formate was 15.2 (IQR 13.8–15.9) mmol/L. The probability of a poor outcome (death or survival with sequelae) was higher than 90% in patients with S‐formate ≥17.5 mmol/L, S‐lactate ≥7.0 mmol/L and/or pH <6.87. The ROC analysis showed that the corresponding areas under the curve (AUC) were 0.64 (0.44–0.85 CI 95%) for S‐formate, 0.75 (0.56–0.93 CI 95%) for ‘S‐formate+S‐lactate’ and only 0.54 (0.38–0.69 CI 95%) for serum methanol, which is lower than for S‐formate (p < 0.05). The measurement of S‐formate is an important tool in the laboratory diagnostics and clinical management of acute methanol poisoning. S‐formate ≥3.7 mmol/L can lead to the first clinical signs of visual toxicity, indicating haemodialysis. S‐formate ≥11–12 mmol/L is associated with visual/CNS sequelae and a lethal outcome.

Efficiency of acidemia correction on intermittent versus continuous hemodialysis in acute methanol poisoning.

Abstract Context: Acidemia is a marker of prognosis in methanol poisoning, as well as compounding formate-induced cytotoxicity. Prompt correction of acidemia is a key treatment of methanol toxicity and methods to optimize this are poorly defined. Objective: We studied the efficiency of acidemia correction by intermittent hemodialysis (IHD) and continuous renal replacement therapy (CRRT) in a mass outbreak of methanol poisoning. Methods: The study was designed as observational cohort study. The mean time for an increase of 1 mmol/L HCO3–, 0.01 unit arterial blood pH, and the total time for correction of HCO3– were determined in IHD- and CRRT-treated patients. Results: Data were obtained from 18 patients treated with IHD and 13 patients treated with CRRT. At baseline, CRRT group was more acidemic than IHD group (mean arterial pH 6.79 ± 0.10 versus 7.05 ± 0.10; p = 0.001). No association was found between the rate of acidemia correction and age, weight, serum methanol, lactate, formate, and glucose on admission. The time to HCO3– correction correlated with arterial blood pH (r= −0.511; p = 0.003) and creatinine (r = 0.415; p = 0.020). There was association between the time to HCO3– correction and dialysate/effluent and blood flow rates (r= −0.738; p < 0.001 and r= −0.602; p < 0.001, correspondingly). The mean time for HCO3– to increase by 1 mmol/L was 12 ± 2 min for IHD versus 34 ± 8 min for CRRT (p < 0.001), and the mean time for arterial blood pH to increase 0.01 was 7 ± 1 mins for IHD versus 11 ± 4 min for CRRT (p = 0.024). The mean increase in HCO3– was 5.67 ± 0.90 mmol/L/h for IHD versus 2.17 ± 0.74 mmol/L/h for CRRT (p < 0.001). Conclusions: Our study supports the superiority of IHD over CRRT in terms of the rate of acidemia correction.

Incorporating thyroid markers in Down syndrome screening protocols

The article aimed to assess the benefit of incorporating maternal serum thyroid disease marker levels (thyroid‐stimulating hormone and free thyroxine) into first trimester Down syndrome screening protocols.

Topiramate induced metabolic acidosis and kidney stones – a case study

Introduction The aim of this study is to present a case of 44 years old woman with topiramate induced metabolic acidosis and kidney stones. Materials and methods The laboratory features of topiramate caused renal tubular acidosis in blood and urine during topiramate treatment, with correction of metabolic acidosis by potassium citrate, and after topiramate withdrawal are presented. Differential diagnosis of all possible causes of metabolic acidosis is discussed. Results The results revealed negative base excess in extracellular fluid of - 9.2 mmol/L, low serum HCO3- concentration (18.6 mmol/L), trend to alkaline urine (pH 6.39) and low urine citrate concentration (0.3 mmol/24h). After topiramate withdrawal, all parameters of the internal environment normalized. Conclusions This study has shown that long-term topiramate administration could induce metabolic acidosis and consequently urholithiasis. Thus, we could recommend testing blood acid base balance, urinary pH and citrates in patients taking topiramate and suffering from kidney stones.

Maternal thyroid-stimulating hormone reference ranges for first trimester screening from 11 to 14 weeks of gestation

To establish maternal thyroid‐stimulating hormone (TSH) reference ranges for first trimester screening from 11 + 0 to 13 + 6 weeks of gestation.

Pseudohyperkalemia - Potassium released from cells due to clotting and centrifugation - a case report

Hyperkalemia is a potentially lethal condition. Pseudohyperkalemia should be always excluded before implementing treatment to prevent inappropriate cause of hypokalemia – equally a potentially lethal condition. Here we present a case report of a 62 year female with chronic myeloproliferative disorder, i.e. essential thrombocythemia. The laboratory test results for potassium concentration were 6.3 mmol/L, for platelet count 1305 x109/L and for leukocyte count 39.8 x109/L. This was due to a temporary drug withdrawal after a surgical intervention for gastric bleeding. Potassium concentration in lithium heparin plasma collected in a vacuum tube without gel separator and in whole blood syringe were 4.6 mmol/L and 3.4 mmol/L, respectively. It means that mechanical stress such as centrifugation can contribute to spurious hyperkalemia.
Prior to reporting unexpected hyperkalemia result, pseudohyperkalemia should always be considered by the laboratory. Such potassium results require investigation in case it is pseudohyperkalemia, which may be due to thrombocytosis and leukocytosis. In cases where thrombocytosis or leukocytosis exists, an interpretative comment indicating these conditions inserted with the results of the potassium concentration can increase awareness for more accurate patient care decisions.

Cystatin C measurement leads to lower metformin dosage in elderly type 2 diabetic patients

The aim of this study was to provide evidence for the hypothesis that estimated glomerular filtration rate from serum Cystatin C (eGFRcys) is better to be determined for all elderly type 2 diabetes mellitus (T2DM) patients based on eGFRcys upward and downward reclassification rate for hypothetical metformin dose reduction by eGFRcys at the GFR decision point of 45 mL/min/1.73 m2. A total of 265 consecutive T2DM elderly patients (age range 65‐91 years) from outpatient diabetic clinic were included in the study. The Kidney Disease Improving Global Outcomes (KDIGO) guidelines for metformin dosing were strictly followed. Estimated glomerular filtration rate from serum creatinine (eGFRcrea) led to results of metformin eligibility. Each of the results of eGFRcrea‐based eligibility was further compared to eGFRcys‐based eligibility. Creatinine was measured by enzymatic method standardized against international reference material SRM 967. Cystatin C was determined by method traceable to DA ERM 471 international standard. eGFRcrea and eGFRcys were calculated according to Chronic Kidney Disease Epidemiology Collaboration (CKD‐EPI) equations. A downward reclassification rate was higher than upward reclassification rate (31 vs 3, respectively; P < 0.0001). The median (IQR) eGFRcrea was higher than eGFRcys (73 (58‐85) vs 63 (50‐75) mL/min/1.73 m2, respectively; P < 0.0001). eGFRcys reclassified significant proportion of patients with T2DM from metformin eligible CKD stages to less or non‐eligible stages. The downward reclassification was more frequent in patients older than 80 years (P < 0.01). Cystatin C‐based eGFR selects more complicated patients, where lower doses of metformin are possibly advisable. We recommend calculating both eGFRcrea and eGFRcys for metformin dosing in elderly patients with T2DM.

Analytical Interference Leading to a Diagnosis of Lymphoproliferative Disorder

BACKGROUND Monoclonal immunoglobulins (paraproteins) are produced by B lymphocytes in lymphoproliferative disorders. A single monoclonal immunoglobulin is homogeneous in terms of its structure, and it can occur in human serum at high concentration and cause significant interference in laboratory assays. CASE We present a case of an 84-year-old man who was admitted to the hospital for progression of dyspnea. Basic laboratory tests showed a serum concentration of conjugated bilirubin, measured using the diazo spectrophotometric method, which was much higher than that of total bilirubin. The cause of the discrepancy was attributed to analytical interference by monoclonal immunoglobulins, which helped establish a diagnosis of lymphoproliferative disorder. CONCLUSION Monoclonal immunoglobulins are relatively rare in serum but are an important cause of analytical interference. Monoclonal immunoglobulins should always be considered a source of interference when unexpectedly high, low, or contradictory data are encountered, and appropriate confirmatory tests (electrophoresis, imunofixation) should be performed in such circumstances. Failure to do so can result in errors in diagnosis and inadequate treatment. Conversely, when samples contain abnormal and especially high monoclonal immunoglobulin levels, the biochemical data should be carefully examined for any discrepancies, such as paraprotein interference, and the results should be taken into consideration in patient management.Key words: paraproteins - lymphoproliferative disorders - bilirubin - interferenceThe authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study.The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 22. 1. 2016Accepted: 1. 12. 2016.