| 1. |
- Mokarami, Parisa, et al.
(author)
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An overlooked aspect on metabolic acidosis at birth: blood gas analyzers calculate base deficit differently.
- 2012
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In: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 1600-0412 .- 0001-6349. ; 91:5, s. 574-579
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Journal article (peer-reviewed)abstract
- Background: Metabolic acidosis (MA) at birth is commonly defined as umbilical cord arterial pH <7.0 plus base deficit (BD) ≥12.0 mmol/L. BD is not a measured entity but calculated from pH and pCO(2) values, with the hemoglobin (Hb) concentration included in the calculation algorithm as a fixed or actual value. Various blood gas analyzers use different algorithms, indicating variations in the MA diagnosis. Objective. To calculate the prevalence of MA in blood and extracellular fluid (ecf) with algorithms from three blood gas analyzer brands relative to the Clinical and Laboratory Standards Institute (CLSI) algorithm. Design: Comparative study. Setting. University hospital. Sample. Arterial cord blood from 15354 newborns. Main outcome measure. Prevalence of MA. Methods. Blood was analyzed in a Radiometer ABL 735 analyzer. BD was calculated post hoc with algorithms from CLSI and Corning and Roche blood gas analyzers, and with actual and fixed (9.3 mmol/L) Hb values. Results: The prevalence of BD ≥12.0 mmol/L in blood was with the CLSI algorithm 1.97%, Radiometer 5.18%, Corning 3.84%, and Roche 3.29% (CLSI vs other; McNemar test, P <0.000001). Similarly, MA prevalences were 0.58%, 0.66%, 0.64% and 0.64% (P≤0.02). BD ≥12.0 and MA rates were lower in ecf than in blood (P≤0.002). Algorithms with actual or fixed Hb concentration made no differences in MA rates (P≥0.1). Conclusion. The neonatal metabolic acidosis rate varied significantly with blood gas analyzer brand and fetal fluid compartment for calculation of BD.
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| 2. |
- Mokarami, Parisa, et al.
(author)
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Arterio-venous blood gas Δvalues for validation of umbilical cord blood samples at birth are not only biased by sample mix ups but also affected by clinical factors
- 2019
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In: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 0001-6349. ; 98:2, s. 167-175
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Journal article (peer-reviewed)abstract
- Introduction: Traditional validation of umbilical cord blood samples with positive veno-arterial ΔpH and arterio-venous ΔpCO2 values confirms the source of samples, whereas negative Δvalues represent mix-up of samples. To investigate whether this is true, the distributions of V-A ΔpO2 and A-V Δlactate were also explored and related to clinical characteristics. In addition, different cord blood sampling techniques were evaluated. Material and methods: Register study with cord blood acid-base and clinical data from 27 233 newborns. Clinical characteristics were related to positive, zero and negative Δvalues. Blood samplings from unclamped and double-clamped cords were compared. A two-sided P < 0.05 was considered significant. Results: ΔpH and ΔpCO2 values distributed into positive, around zero, and negative sub-populations, with significant differences in pH and clinical characteristics between sub-populations. No such sub-populations were distinguished for ΔpO2 and Δlactate. The 2.5th and 5th ΔpH percentiles were 0.013 and 0.022, respectively, and for ΔpCO2 0.30 and 0.53 kPa. Applying 5th percentile criteria resulted in 3.5% of “approved” cases showing a ΔpO2 ≤ 0. Puncture and sampling of the unclamped cord resulted in significantly better sample quality. Conclusions: Unphysiological negative ΔpO2 values occurred despite correct validation with traditional criteria. Δlactate cannot be used for validation because both positive and negative values are physiological. Positive/around zero/negative ΔpH and ΔpCO2 sub-populations were associated with significant differences in pH and clinical characteristics, indicating that defective sampling and sample handling are not the sole explanations for negative Δvalues. Prompt puncture and sampling of the unclamped cord resulted in best sample quality.
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| 3. |
- Mokarami, Parisa, et al.
(author)
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Hidden acidosis: an explanation of acid-base and lactate changes occurring in umbilical cord blood after delayed sampling.
- 2013
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In: BJOG: An International Journal of Obstetrics & Gynaecology. - : Wiley. - 1471-0528 .- 1470-0328. ; 120:8, s. 996-1002
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Journal article (peer-reviewed)abstract
- OBJECTIVE: To explore the 'hidden acidosis' phenomenon, in which there is a washout of acid metabolites from peripheral tissues in both vaginal and abdominal deliveries, by investigating temporal umbilical cord blood acid-base and lactate changes after delayed blood sampling. DESIGN: Prospective comparative study. SETTING: University hospital. SAMPLE: Umbilical cord blood from 124 newborns. METHODS: Arterial and venous cord blood was sampled immediately after birth (T0 ), and at 45 seconds (T45 ), from unclamped cords with intact pulsations taken from 66 neonates born vaginally and 58 neonates born via planned caesarean section at 36-42 weeks of gestation. Non-parametric tests were used for statistical comparisons, with P < 0.05 considered significant. MAIN OUTCOME MEASURES: Temporal changes (T0 -T45 ) in umbilical cord blood pH, the partial pressure of CO2 (\prod a) and O2 (\prod a), and in the concentrations of lactate, haematocrit (Hct), and haemoglobin (Hb). RESULTS: In both groups all arterial parameters, except for \prod a in the group delivered by caesarean section, changed significantly (pH decreased and the other variables increased). There were corresponding changes in venous acid-base parameters. When temporal arterial changes were compared between the two groups, the decrease in pH and increase in \prod a were more pronounced in the group delivered vaginally. Neonates born vaginally had significantly lower pH and higher lactate, Hct, and Hb concentrations at T0 and T45 in both the artery and the vein. At T45 , arterial \prod a and \prod a levels in the group delivered vaginally were also significantly higher. CONCLUSIONS: Delayed umbilical cord sampling affected the acid-base balance and haematological parameters after both vaginal and caesarean deliveries, although the effect was more marked in the group delivered vaginally. The hidden acidosis phenomenon explains this change towards acidaemia and lactaemia. Arterial haemoconcentration was not the explanation of the acid-base drift.
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| 4. |
- Mokarami, Parisa
(author)
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Pitfalls in Interpreting Umbilical Cord Blood Gases and Lactate at Birth
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Acid-base status in umbilical cord blood is an objective measure of the fetus’ exposure to and ability to handle hypoxia. The objective of this thesis was to clarify some of the methodological pitfalls in interpreting umbilical cord blood gases and lactate values at birth. Study I pinpoints the methodological confounding in calculating base deficit (BD) with algorithms used in different brands of blood gas analyzers and reports the consequences for diagnosing metabolic acidosis (MA) at birth. Neonatal MA rates cannot be compared between maternity units or between scientific articles where different fetal compartments (blood or extracellular fluid) and different algorithms for calculating BD have been used. Study II addresses the issue of possible diagnostic discrepancies when acid-base parameter value decimals are rounded off. A drift of a dichotomy parameter value cut-off due to decimal rounding will result in a shift in distribution of negative and positive cases in a population sample. The findings warrant a discussion on standardization of round-off rule and the number of decimals for a specific analyte result. Study III demonstrates that delayed cord blood sampling with intact pulsations affects umbilical acid-base values and hematological parameters in both vaginal and cesarean deliveries. The changes were more marked after vaginal delivery. A change towards acidemia and lactemia can be explained by the hidden acidosis phenomenon, i.e. a surge into the central circulation of peripherally trapped acid metabolites when the newborn starts to breathe. Study IV shows that clinical characteristics have a significant influence on the distribution of veno-arterial and arterio-venous gradients (Δ values) in umbilical cord blood. Validation criteria based on fixed ΔpH and ΔpCO2 values may then exclude correct samples of clinical outliers. Lactate cannot be used for validation of umbilical cord blood samples. A negative ΔpO2 value indicates delayed cord blood sampling or mix-up of samples and is the only certain validation criterion.
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| 5. |
- Olofsson, Per, et al.
(author)
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How mathematics warp biology: round-off of umbilical cord blood gas case value decimals distorts calculation of metabolic acidosis at birth.
- 2012
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In: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 1600-0412 .- 0001-6349. ; 91, s. 39-43
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Journal article (peer-reviewed)abstract
- Objective. To illustrate the impact on settling neonatal metabolic acidosis diagnosis by rounding off pH and base deficit (BD) case value decimals. Design. Comparative study. Setting. University maternity units. Sample. Umbilical cord arterial blood gas values from 18 831 newborns. Main outcome measures. Prevalences of pH <7.05 and metabolic acidosis diagnosis (pH <7.05 plus BD >12.0 mmol/L). Methods. Calculation of BD from pH and pCO(2) values, and calculating the prevalences of metabolic acidosis before and after rounding off three-decimal values to two or one decimals. The 'round to half even' and 'round half up' round-off rules were used for digit 5. Results. Arterial pH was ≤7.049 in 339 newborns (1.8%). In 27 (8.0%) pH was 7.045-7.049, rounded off to 7.05 when truncated to two decimals (crude vs. round-off values; McNemar´s test, p<0.000001). Depending on round-offs of pH case value decimals before or after calculation of BD, and round-offs of resulting three-decimal BD values to one decimal, metabolic acidosis 'disappeared' or 'appeared' in eight of totally 75 metabolic acidosis cases (10.7%). With different modes of calculation, the number of metabolic acidosis cases varied between 75 and 71 cases (p≥0.1). Conclusion. Due to pH and BD case value decimal round-offs, a diagnostic discrepancy of acidotic pH values occurred in 8%, and of metabolic acidosis diagnosis in 10.7% of cases. A drift of a dichotomy parameter value cut-off due to decimal round-offs will result in a shift in distribution of positive and negative cases in a population sample.
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| 6. |
- Åkerman, Fernanda, et al.
(author)
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The small-for-gestational-age fetus has an intact ability to develop lacticemia when exposed to hypoxia : a retrospective comparative register study
- 2018
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In: Journal of Maternal-Fetal and Neonatal Medicine. - : Informa UK Limited. - 1476-7058 .- 1476-4954. ; 31:10, s. 1290-1297
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Journal article (peer-reviewed)abstract
- Objective: To investigate the ability of small-for-gestational-age (SGA) fetuses to develop lacticemia during hypoxia. Methods: Umbilical cord arterial and venous pH, lactate and glucose concentrations were determined in 1777 SGA (<10th percentile) and 14,569 AGA newborns and related to acidemia (pH < mean –2SD). Non-parametric statistics with two-sided p < .05 were considered significant. Results: Glucose and lactate were linearly related and both variables correlated negatively with pH. Glucose was equal in SGA and AGA at a normal pH, but at severe acidemia it was lower in SGA. Glucose was higher in both groups during acidemia. Lactate was higher in SGA at both a normal and a low pH, and in both groups lactate increased progressively with the severity of acidemia. Conclusions: In both SGA and AGA fetuses, glucose was mobilized during acidemia; lactate was higher in SGA at both a normal and low pH. Considering SGA being a proxy for fetal growth restriction, and acidemia a proxy for hypoxia, it is concluded that growth-restricted fetuses have an intact ability to develop lacticemia during hypoxia.
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