Nana Wiberg

Delayed umbilical cord clamping at birth has effects on arterial and venous blood gases and lactate concentrations

Objective  To estimate the influence of delayed umbilical cord clamping at birth on arterial and venous umbilical cord blood gases, bicarbonate (), base excess (BE) and lactate in vigorous newborns.

Relation between umbilical cord blood pH, base deficit, lactate, 5-minute Apgar score and development of hypoxic ischemic encephalopathy

Objective. Umbilical cord acid–base analysis is fundamental for assessing intrapartum hypoxia. The accuracy of arterial umbilical cord blood lactate, pH and base deficit to reflect a low 5‐minute Apgar score and hypoxic ischemic encephalopathy (HIE) stage 2–3 was assessed, and new gestational age‐adjusted reference standards were compared with traditional stationary reference values. Design and sample. A total of 13,735 pH‐validated routine cord acid–base values from singleton deliveries were tested with stationary and gestational age‐adjusted reference values using receiver operating characteristic curves and calculation of area under curve. Setting. University hospital. Main outcome measures. Accuracy of low pH, high base deficit and high lactate, alone or in combination, to imply 5‐minute Apgar score < 7 or < 4 or HIE. Results. Gestational age‐adjusted values were for all parameters significantly better than crude values to indicate Apgar score < 7. For Apgar score < 4, the differences were not significant. The frequency of HIE was 0.046%, making statistical analyses pointless. Gestational age‐adjusted lactate had the overall best accuracy and among combinations; a low age‐adjusted pH plus high age‐adjusted lactate was slightly better than a low age‐adjusted pH plus high age‐adjusted base deficit. The sensitivity and positive predictive value were low for all parameters. Conclusions. Lactate in cord arterial blood at birth is at least as good as base deficit to reflect an impaired condition at birth, and best when gestational age‐adjusted values are used. Due to methodological confounding involved in calculation of base deficit, lactate may replace base deficit as an acid–base outcome parameter at birth.

Lactate concentration in umbilical cord blood is gestational age-dependent: a population-based study of 17 867 newborns.

Objective  To study the influence of gestational age on lactate concentration in arterial and venous umbilical cord blood at birth and to define gestational age‐specific reference values for lactate in vigorous newborns.

An overlooked aspect on metabolic acidosis at birth: Blood gas analyzers calculate base deficit differently

Objective. Metabolic acidosis (MA) at birth is commonly defined as umbilical cord arterial pH < 7.0 plus base deficit (BD) ≥ 12.0 mmol/L. Base deficit is not a measured entity but is calculated from pH and Pco2 values, with the hemoglobin (Hb) concentration [Hb] included in the calculation algorithm as a fixed or measured value. Various blood gas analyzers use different algorithms, indicating variations in the MA diagnosis. The objective was therefore to calculate the prevalence of MA in blood and extracellular fluid 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 15 354 newborns. Main outcome measure. Prevalence of MA. Methods. Blood was analyzed in a Radiometer ABL 735 analyzer. Base deficit was calculated post hoc with algorithms from CLSI and Corning and Roche blood gas analyzers, and with measured and fixed (9.3 mmol/L) values of [Hb]. 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). Likewise, MA prevalences were 0.58, 0.66, 0.64 and 0.64%, respectively (p≤ 0.02). Base deficit ≥ 12.0 mmol/L and MA rates were lower in extracellular fluid than in blood (p≤ 0.002). Algorithms with measured or fixed Hb concentration made no differences to MA rates (p≥ 0.1). Conclusions. The neonatal metabolic acidosis rate varied significantly with blood gas analyzer brand and fetal fluid compartment for calculation of BD.

Lipogranuloma peritonealis caused by spontaneous rupture of a benign cystic ovarian teratoma

Acta Obstet Gynecol Scand 2003; 82: 91–94.

Fetal scalp blood lactate during second stage of labor: determination of reference values and impact of obstetrical interventions

Abstract Objective: To determine the reference interval of fetal scalp blood lactate during second stage of labor. Material: Two hundred and fifty-three women in first stage of labor with a reassuring CTG were asked for permission to sample fetal scalp blood during second stage. Results: In cases with reassuring CTG and five minute Apgar score ≥9, the mean lactate value (±2 SD) was 2.5 mmol/L (lower limit 1.1, higher limit 5.2). The lactate concentration was significantly higher among nulliparous and in cases with use of epidural or oxytocin (p <0.001). There was a moderate positive correlation between scalp lactate values and active pushing time. When parity, epidural, oxytocin and active pushing time were analyzed together, they had equal influence on lactate values (p <0.001). Higher lactate values were associated with intermediate/pathological CTG compared to normal CTG (p <0.001). There was no correlation to gestational age or birthweight (p = 0.72, respectively 0.43). Conclusions: The reference interval of fetal scalp lactate during second stage is 1.1–5.2 mmol/L. Parity, use of epidural or oxytocin and the duration of pushing are associated to increased lactate concentration; however, we could not demonstrate any correlation to advancing gestational age or birthweight.

Fetal scalp blood sampling during labor: an appraisal of the physiological basis and scientific evidence

Fetal cardiotocography is characterized by low specificity; therefore, in an attempt to ensure fetal well‐being, fetal scalp blood sampling has been recommended by most obstetric societies in the case of a non‐reassuring cardiotocography. The scientific agreement on the evidence for using fetal scalp blood sampling to decrease the rate of operative delivery for fetal distress is ambiguous. Based on the same studies, a Cochrane review states that fetal scalp blood sampling increases the rate of instrumental delivery while decreasing neonatal acidosis, whereas the National Institute of Health and Clinical Excellence guideline considers that fetal scalp blood sampling decreases instrumental delivery without differences in other outcome variables. The fetal scalp is supplied by vessels outside the skull below the level of the cranial vault, which is likely to be compressed during contractions. The self‐regulated redistribution of oxygenated blood from peripheral to central organs causes peripheral ischemia, thus theoretically bringing into question the scalp capillary bed as representative of the central circulation.

Hidden acidosis: an explanation of acid-base and lactate changes occurring in umbilical cord blood after delayed sampling.

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.

How mathematics warp biology: round-off of umbilical cord blood gas case value decimals distorts calculation of metabolic acidosis at birth.

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 pCO2 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; McNemars 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 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.

Arterio-venous blood gas Δvalues for validation of umbilical cord blood samples at birth are biased not only by sample mix ups but also affected by clinical factors

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.