Determination of Arterial Blood Ammonia in Uremic Patients Before and After Hemodialysis Using Three Different Ammonia Methods

Huizenga, [No Value]; Mulder, Bart A.; Stegeman, CA; Ament, W.; Teelken, A.W.

doi:10.1046/j.1525-1594.2002.00925.x

Cited by 3 publications

(2 citation statements)

References 8 publications

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“…The BAC-II method, on the other hand, is based on a microdiffusion technique in which alkaline liberation of gaseous ammonia is accomplished and ammonia is measured by using the colorimetric bromocresol green reaction within a reaction chamber. 21 In the enzymatic method, blood cannot be preserved at room temperature. This applies even more to blood from patients with liver disease because increased ␥-glutamyl transferase activity, a frequent observation in cirrhotic patients, has been associated with increased enzymatic hydrolysis of glutamine leading to artefactual increased ammonia levels.…”

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confidence: 99%

Blood ammonia determination in cirrhosis: Still confusing after all these years?

Yurdaydın¹

2003

Hepatology

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Correlation between ammonia levels and the severity of hepatic encephalopathy. Am J Med 2003;114:188-193. (Reprinted with permission from Excerpta Medica, Inc.) PURPOSE: Because the correlation between ammonia levels and the severity of hepatic encephalopathy remains controversial, we prospectively evaluated the correlation in 121 consecutive patients with cirrhosis. METHODS: The diagnosis of hepatic encephalopathy was based on clinical criteria, and the severity of hepatic encephalopathy was based on the West Haven Criteria for grading of mental status. Arterial and venous blood samples were obtained from each patient. Four types of ammonia measurements were analyzed: arterial and venous total ammonia, and arterial and venous partial pressure of ammonia. Spearman rank correlations (r s ) were calculated. RESULTS: Of the 121 patients, 30 (25%) had grade 0 encephalopathy (no signs or symptoms), 27 (22%) had grade 1, 23 (19%) had grade 2, 28 (23%) had grade 3, and 13 (11%) had grade 4 (the most severe signs and symptoms). Each of the four measures of ammonia increased with the severity of hepatic encephalopathy: arterial total ammonia (r s ‫؍‬ 0.61, P < .001), venous total ammonia (r s ‫؍‬ 0.56, P < .001), arterial partial pressure of ammonia (r s ‫؍‬ 0.55, P < .001), and venous partial pressure of ammonia (r s ‫؍‬ 0.52, P < .001). CONCLUSION: Ammonia levels correlate with the severity of hepatic encephalopathy. Venous sampling is adequate for ammonia measurement. There appears to be no additional advantage of measuring the partial pressure of ammonia compared with total ammonia levels.

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Section: Commentsmentioning

confidence: 99%

Blood ammonia determination in cirrhosis: Still confusing after all these years?

Yurdaydın¹

2003

Hepatology

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“…Ion-selective electrodes can measure ammonia in plasma or whole blood, but this requires sample volumes of several milliliters, a response time of 10 to 15 min, and frequent electrode recalibration. − The ideal alternative would be a portable point-of-care device that operates on small volumes of whole blood (e.g., a single drop of capillary blood) that is easily available in any clinical setting. The PocketChem Blood Ammonia Checker (BAC) attempts to meet these goals as a portable device that alkalizes a 20 μL blood sample and then quantifies gaseous ammonia using a colorimetric test with bromocresol green. , BAC has been used in several research trials with humans, − but despite being available for more than 25 years, it has not been validated for clinical use. For example, a study comparing the performance of BAC with the standard clinical ammonia assay showed an intraclass correlation coefficient of 0.80 and a Deming linear regression correlation coefficient of only R 2 = 0.705, with a 13% false negative rate, highlighting its inadequacy for clinical use …”

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Point-of-Care Analysis of Blood Ammonia with a Gas-Phase Sensor

et al. 2020

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Elevated blood ammonia (hyperammonemia) may cause delirium, brain damage, and even death. Effective treatments exist, but preventing permanent neurological sequelae requires rapid, accurate, and serial measurements of blood ammonia. Standard methods require volumes of 1 to 3 mL, centrifugation to isolate plasma, and a turn-around time of 2 h. Collection, handling, and processing requirements mean that community clinics, particularly those in low resource settings, cannot provide reliable measurements. We describe a method to measure ammonia from small-volume whole blood samples in 2 min. The method alkalizes blood to release gas-phase ammonia for detection by a fuel cell. When an inexpensive first-generation instrument designed for 100 μL of blood was tested on adults and children in a clinical study, the method showed a strong correlation (R 2 = 0.97) with an academic clinical laboratory for plasma ammonia concentrations up to 500 μM (16 times higher than the upper limit of normal). A second-generation hand-held instrument designed for 10–20 μL of blood showed a near-perfect correlation (R 2 = 0.99) with healthy donor blood samples containing known amounts of added ammonium chloride up to 1000 μM. Our method can enable rapid and inexpensive measurement of blood ammonia, transforming diagnosis and management of hyperammonemia.

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Repeated Measures of Blood and Breath Ammonia in Response to Control, Moderate and High Protein Dose in Healthy Men

Spacek

Strzepka

Saha

et al. 2018

Sci Rep

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Ammonia physiology is important to numerous disease states including urea cycle disorders and hepatic encephalopathy. However, many unknowns persist regarding the ammonia response to common and potentially significant physiologic influences, such as food. Our aim was to evaluate the dynamic range of ammonia in response to an oral protein challenge in healthy participants. We measured blood and breath ammonia at baseline and every hour for 5.5 hours. Healthy men (N = 22, aged 18 to 24 years) consumed a 60 g protein shake (high dose); a subset of 10 consumed a 30 g protein shake (moderate dose) and 12 consumed an electrolyte drink containing 0 g protein (control). Change in blood ammonia over time varied by dose (p = 0.001). Difference in blood ammonia was significant for control versus high (p = 0.0004) and moderate versus high (p = 0.03). Change in breath ammonia over time varied by dose (p < 0.0001). Difference in breath ammonia was significant for control versus moderate (p = 0.03) and control versus high (p = 0.0003). Changes in blood and breath ammonia were detectable by fast, minimally-invasive (blood) or non-invasive (breath) point-of-care ammonia measurement methods. These pilot data may contribute to understanding normal ammonia metabolism. Novel measurement methods may aid research into genetic and metabolic ammonia disorders.

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Determination of Arterial Blood Ammonia in Uremic Patients Before and After Hemodialysis Using Three Different Ammonia Methods

Cited by 3 publications

References 8 publications

Blood ammonia determination in cirrhosis: Still confusing after all these years?

Blood ammonia determination in cirrhosis: Still confusing after all these years?

Point-of-Care Analysis of Blood Ammonia with a Gas-Phase Sensor

Repeated Measures of Blood and Breath Ammonia in Response to Control, Moderate and High Protein Dose in Healthy Men

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