cord gas interpretation calculator cord gas interpretation calculator

not associated with metabolic acidosis) at birth is indicative of impaired gas exchange and consequent reduced oxygen delivery to the fetus. Together with other clinical measurements (including fetal heart rate [FHR] tracings, Apgar scores, newborn nucleated red cell counts, and neonatal imaging), cord gas analysis can be remarkably helpful in determining the cause for a depressed newborn. BACKGROUND. 18-22 As delayed cord clamping has . Metabolic acidosis is when there are high acid levels in the body that originated from impaired kidney function. Wykoff M, Garcia D, Margraf L, Perlman J, et al. So when HCO 3 - is raised the pH is increased as there are less free H+ ions (alkalosis). Check out our full ABG interpretation guide if you want to learn more. Unfortunately it is more difficult to sample arterial than venous cord blood because umbilical arteries are much smaller and less visible than umbilical veins [20]. There are many reasons as to why a baby would have normal blood cord gases despite suffering from a hypoxic brain injury. Australia and New Zealand J of Obstetrics and Gynaecology 2010; 50: 318-28, Get fertility advice personalized for you, Umbilical cord base excess or base deficit, needle aspiration of two blood samples (one venous, one arterial) from the excised clamped cord segment into pre-heparinized syringes. The pH of venous blood should be between 7.31 and 7.41, whereas arterial blood should be between 7.35 and 7.45. It was a good review of ABG analysis. Btu Calculator. After the mother's blood is oxygenated, it is absorbed by the placenta's capillaries. New York, Springer-Verlag; 1990, p91. Blood gas analysis is a commonly used diagnostic tool to evaluate the partial pressures of gas in blood and acid-base content. The change is a progressive decrease in pH and base excess, and an increase in pCO2 and lactate. Box 51-1 describes an umbilical cord blood gas sampling procedure. SID means Strong Ion Difference (SIDa and SIDe for SID apparent or effective). Again, this needs to be done quickly to get reliable umbilical cord blood gas results. Tight nuchal cord and neonatal hypovolemic shock. Hopefully I won't need it again but if I do, I have definitely found my lawyer for life and I would definitely recommend this office to anyone! Acta Paediatr 1963;52: 497-512. A VBG is obtained by placing a venous sample . Low pH levels caused by acidosis can result in hypoxic-ischemic encephalopathy, periventricular leukomalacia, seizures, brain hemorrhages, and cerebral palsy. Dunn PM. There is no general agreement on the definition of a widened base deficit difference. A widened difference in PCO2 (18 mmHg or greater) in the absence of a widened pH difference is clinically quite rare. Median (5th-95th percentile):PH:7.27 (7.12 7.35); pO2: 16.3 mmHg (6.2-27.6); PCO2:55.1 mmHg (41.9-73.5);Bicarbonate:24.3 mmol/L (18.8-28.2);Base excess:-3.00 mmol/L (-9.3 to +1.5);Lactate:3.7 mmol/L (2.0-6.7). The standard technique of sampling cord blood for gas and acid-base analysis comprises three steps: clamping a segment of the cord removing the clamped cord segment needle aspiration of two blood samples (one venous, one arterial) from the excised clamped cord segment into preheparinized syringes With an intact umbilical-placental circulation, any metabolic acidosis appearing in the umbilical arteries will almost instantaneously appear in the umbilical vein. Base excess is defined as the amount of strong acid that must be added to each liter of fully oxygenated blood to return the pH to 7.40 at a temperature of 37C and a pCO2 of 40 mmHg (5.3 kPa), while a base deficit (ie. The blood-gas values were statistically analyzed and reported. Reduced prevalence of metabolic acidosis at birth: an analysis of established STAN usage in the total population of deliveries in a Swedish district hospital. Umbilical venous pressure and Doppler flow pattern of inferior vena cava in the fetus. Umbilical cord O 2 and CO 2 Fetal cord gas values result from the rapid transfer of gases and the slow clearance of acid across the placenta. Although the quality and reliability of the blood gas instruments have improved dramatically, constant vigilance still is required and mandated to ensure accurate and precise results. In: Handmaker H, Lowenstein JM (eds): Nuclear medicine in clinical pediatrics.. New York, Society of Nuclear Medicine, 1975, pp167-185. Arterial Blood Gas Interpretation Calculator. The P o2 and P co2 values can provide further clues to the interpretation of the clinical picture and helps to exclude rogue results. NEONATOLOGYTODAY Volume 15Issue 11 Pages 54-57 Release date: November 2020 DOI: https://doi.org/10.51362/neonatology.today/20201115115457 [Click Here to Download PDF], [Full Text][Figures & Tables][Article Info][Reference]. mmol/L. Immediately after birth, ideally before the babys first breath, an approximate 20-cm segment of cord must be isolated between two sets of two clamps. The applicability of cord blood gas analysis is an unresolved controversy that will be addressed: should cord blood gas analysis be reserved for defined high-risk deliveries or should it, as some advise, be more universally applied at all hospital births? Program: Blood Gas Interpretation Chart, 3rd Ed (5-Pack) $ 30.00 Based on the Siggaard-Andersen Acid-Base Alignment Nomogram, this tool allows you to accurately interpret a neonatal blood gas result in seconds. The umbilical-cord blood data contained in the table is derived from a study [1] of all 19,600 live births (>20 weeks gestation) at a tertiary care obstetrics unit during a 3-year period; results are consistent with smaller, earlier studies [2, 3]. The test is used to check the function of the patient's lungs and how well they are able to move oxygen into the blood and remove carbon dioxide. A review of basic fetal cord gas physiology will assist in understanding how values are interpreted. Cord-blood metabolic acidosis which is characterized by reduced blood pH and decreased base excess (i.e. First, the A-V difference of lactate in cord blood has not been sufficiently clearly defined, so there is no way of reliably confirming that a lactate result relates to cord arterial blood. The baby might have had poor circulation and perfusion shortly before being born or they could have experienced a physical head injury during delivery. Your practical guide to critical parameters in acute care testing. Paediatric Child Health 2012; 17: 41-43, Mokorami P, Wiberg N, Olofsson P. Hidden acidosis: an explanation of acid-base and lactate changes occurring in umbilical cord blood after delayed sampling. Am J Perinatol 1994;11:255-9. The lack of consensus on this issue among national expert bodies is reflected in obstetric practice around the world; some obstetric units having a selective policy, whilst others are routinely performing cord blood gas analysis at all births. New York, Academic Press, 1967, p279. by Cathy Parkes July 17, 2020 Updated: January 18, 2023 2 min read 5 Comments. Your doctor may run a blood gas analysis or arterial blood gas (ABG) test if you are showing the signs of an oxygen, carbon dioxide, or pH imbalance such as confusion or difficulty breathing. As one erudite neonatologist summarized, "Just add water! In the intervillous space of the placenta, carbon dioxide diffuses from the fetus into the mothers blood and the mother can eliminate it by exhalation through her lung. We calculated Spearman correlation coefficients and receiver operating characteristic curves for various levels of umbilical artery pH, base excess, and Apgar scores. increased base deficit) thus implies that sometime during labor, oxygenation of fetal tissues was severely compromised. Venous cord blood analysis reflects a combination of maternal acid-base status and placental function . When HCO 3 - is low the pH is decreased as there are more free H+ ions (acidosis). To my knowledge, all animal studies of fetal cord occlusion involve sudden and complete occlusion rather than any period of continued venous occlusion with the restored arterial flow. Arterial Blood Gases (ABG) Calculator The arterial blood gases calculator calculates whether an individual is in metabolic acidosis, metabolic alkalosis, respiratory acidosis, respiratory alkalosis, or is normal. However, a diagnosis of HIE depends in part on demonstrating significant cord-blood metabolic acidosis, and a normal arterial cord-blood pH and base excess result usually excludes the possibility of perinatal asphyxia, and thereby that any neurological signs and symptoms (including cerebral palsy) exhibited by the neonate is due to HIE. It does not determine if a baby should be cooled. a negative base excess) is defined by the amount of strong base that must be added. Curr Opin Obstet Gynecol 2001; 13: 141-45, Gjerris A, Staer-Jensen J, Jorgenson J. Umbilical cord blood lactate: a valuable tool in the assessment of fetal metabolic acidosis. The hallmark of cord occlusion with terminal bradycardia is widened venoarterial pH, PCO. WbmedCentral. Acidosis usually presents itself as decreased blood pH and increased base deficit. WARNING. Fetal heart rate variability changes during brief repeated umbilical cord occlusion in near term fetal sheep. Wyckoff MH, Perlman JM, Laptook AR. Because pH is the most reproducible of the three measured blood gas parameters, looking at the difference between pHs to alert to an abnormally large difference is most helpful. Cord Occulsion with Terminal Fetal Bradycardia Anatomy and Pathophysiology: Sequential Events and Approximate Timeline. The investigation is relatively easy to perform and yields information that can guide the management of acute and chronic illnesses.This information indicates a patient's acid-base balance, the effectiveness of their gas exchange and the state of their ventilatory control. The analysis of cord blood respiratory gases and acid-base values is an important adjunct for determining the extent and cause of fetal acidosis at delivery. The question is how much oxygen the baby was getting. There are wide ranges of umbilical cord gas values which can be considered normal. Procedures for the Collection of Arterial Blood Specimens; Approved Standard Fourth Edition. Membranes ruptured spontaneously two hours prior to admission. The slower the circulation is through the placenta, the greater the amount of oxygen diffusion from mother to fetus, and the higher the PO2 in the umbilical vein. Body Mass Index. Value: Normal Range: Abnormal Values: pH. The contact form sends information by non-encrypted email, which is not secure. The umbilical cord segment can be set aside at room temperature for 60 minutes without risk of clotting or changes in pH, PO 2, or PCO 2. Early Human Development 2010; 86: 336-44, Kurinczuk J, White-Koning M, Badawi N. Epidemiology of neonatal encephalopathy and hypoxic-ischemic encephalopathy. 1. Arterial Blood Gas (ABG) Calculator pH : PaCO2 : mm Hg HCO3 : mEq/L Result : Please fill out required field. Base buffers have been used to maintain oxygenation B. Pediatrics 1997; 99: 851-59, Peliowski-Davidovich A. Hypothermia for newborns with hypoxic ischemic encephalopathy. Asphyxia is reduced tissue oxygen (hypoxia) of sufficient severity and duration to cause metabolic acidosis [5]. However, it is important to note that the ABG calculator should not be used as a substitute for clinical judgment. All human beings including the fetus inside the uterus before birth depend on two gases, oxygen, and carbon dioxide are being exchanged, oxygen enters the body and carbon dioxide exits the body. Normal buffering mechanisms are overwhelmed by this acid influx, and pH falls below normal limits. and Towson; Carroll County including Westminster; Frederick County including Frederick; Harford County including Abingdon, Bel Air, Belcamp, and Forest Hill; Montgomery County including Germantown and Rockville; Howard County including Ellicott City and Columbia, Washington, D.C. and Washington County including Hagerstown. At time of cord clamp: Double clamp and divide a ~10-15 cm segment of cord and place on delivery table* * time for blood gas assessment: 60 minutes from clamped cord segment, 60 minutes in heparin flushed syringe at room temp. (16). How long can umbilical cord blood gases remain stable in a heparinized syringe at room temperature? Compensation can be seen when both the PCO2 and HCO3 rise or fall together to maintain a normal pH. National clinical guidelines in the UK [26], endorsed by the Royal College of Obstetricians and Gynaecologists, suggest a selective approach, in stating that Paired cord blood gases do not need to be taken routinely. Delay in clamping by as little as 45 seconds after birth results in significant change in acid-base parameters [13-15]; the longer the delay, the greater is the change [16, 17]. Randomized trial of volume infusion during resuscitation of asphyxiated neonatal piglets. Some experts define fetal acidemia as a pH of less than 7.1. If is preferable to obtain both arterial and venous umbilical cord blood samples for analysis. However, because lactic acid crosses the placenta relatively poorly, a significantly greater base deficit in arterial cord blood indicates the presence of umbilical vein occlusion with at least some interval of partially restored umbilical arterial blood flow. This has medico-legal significance for resolving disputes about the cause of brain damage sustained at birth [11]. The case settled and I got a lot more money than I expected. Blood cord gases results can be used as an important piece of evidence in birth injury litigation. Adult arterial (non-cord) blood values (for comparison only). Recommendation from the Clinical and Laboratory Standards Institute (CLSI) is that arterial blood specimens should be analyzed within 30 minutes of sampling [19]. Correpondence of this manuscript should be addressed to: Case 10: Umbilical Cord Occlusion with Terminal Fetal Bradycardia, Mild. Metabolic acidosis develops because when tissue cells are severely depleted of oxygen, aerobic metabolism of glucose is compromised, and cells must depend for their function and survival on less effective anaerobic pathways that result in reduced ATP (energy) production and, importantly for this discussion, accumulation of metabolic acids (principally lactic acid) [6]. Introduction, indications and sources of errors 2. The primary cause of acidosis comes from the lack of adequate oxygen being transferred from the placenta to the baby. (18,19) This is difficult to study because of the rarity of delivery room resuscitation that includes volume expansion. The wider the differences between umbilical venous and arterial samples, likely the longer the interval of umbilical vein obstruction with the restored umbilical arterial flow. Well summarized and easy to under stand and remember . 0.3-3mLs. [1] Immediately after birth, by umbilical cord blood sampling. Blood gas measurements and noninvasive estimations provide important information about oxygenation. Teitel DF, Iwamoto HS, Rudolph AM. NCCLS document H11-A4. cord gas interpretation calculator. In severe cases of metabolic acidosis, it can lead to multi-organ failure and even death. To retrieve blood for analysis the cord segment is first cut between the two clamps at each end, so that the clamped segment can be removed from the immediate vicinity of the baby. They should be taken when there has been concern about the baby either in labor or immediately following birth.. Nippon Sanka Fujinka Gakkai Zasshi 1984;36:1921-9. The most important measurements used in arterial cord blood gases examination are the baby's pH levels and their base deficit. Understanding and use of blood gas analysis enable providers to interpret respiratory, circulatory, and metabolic disorders. Under these circumstances it cannot be assumed that the results relate to arterial blood; indeed, it is most probable, given the relative ease of sampling venous blood, that they relate to venous blood. Widened differences also may be associated with fetal heart failure. Indeed, most (around 75 %) babies with significant metabolic acidosis (pH <7.0, base excess. This calculator only differentiates between acute (pH abnormal) and compensated (pH normal). 7.35-7.45. pH < 7.35 indicates ACIDOSIS (ACID) Thus venous cord blood reflects the combined effect of maternal acid-base status and placental function, whilst arterial cord blood reflects neonatal acid-base status. Arterial Blood Gas (ABG) Analyzer - MDCalc Arterial Blood Gas (ABG) Analyzer Interprets ABG. Martin GC, Green RS, Holtzman IR. After birth, this exchange of gases happens in the lung, oxygen entering the body through inhaling and the lungs, and carbon dioxide leaving through exhaling and the lungs.But before birth, the fetus does not use its lungs the same way we use after birth. The doctor will clamp the umbilical cord quickly after childbirth. Effects of birth-related events on central blood flow patterns. The pros and cons of selective versus routine cord blood gas analyses were discussed by Thorp, All damaged babies will have a cord-blood pH on record (important for medico-legal disputes because a normal cord-blood pH usually excludes perinatal asphyxia as the cause of brain injury), Staff become more proficient in obtaining cord-blood samples, Process becomes habitual, so less chance of forgetting to perform in emergency situations, Result may assist with newborn care, should unforeseen problems develop after birth, Helps clinicians gain insight into interpretation of electronic fetal monitoring for safe and effective intervention strategies has educative value, Requires increased staff resources that might simply not be available in some units, Occasional finding of reduced cord-blood pH in a normally healthy vigorous newborn might pose a potential medico-legal concern because it falsely suggests birth asphyxia, Webinar presented by Jan Stener Jrgensen, MD PhD, Head of Obstetrics and Professor of Clinical Obstetrics, University of Southern Denmark. In the experimental animal, it has been demonstrated that occluding the cord for one minute and repeating the occlusion every 2.5 minutes results in progressive acidosis in the fetus. So we need to ask ourselves: Is the HCO 3 - normal or abnormal? This potential safety audit function of universal cord blood gas testing is addressed by a recent study [1] that suggests adoption of a universal testing policy resulted in improved perinatal outcomes. Although widened pH differences are almost always associated with cord occlusion with terminal fetal bradycardia, rarely the pH difference falls within the normal range, 0.04 0.10. But you do not need to have a malpractice lawsuit to want to better understand your child's blood gas values and what they mean. Then it can be seen that bicarbonate "falls," revealing the underlying . Armstrong L, Stenson B. We have written extensively about umbilical cord blood gas interpretation.. Can occur after delayed cord clamp. Second, there remains no consensus on the cut-off lactate value that should be used to define significant cord metabolic acidosis, as there is for pH and base excess (pH <7.0, base excess. Body Surface Area. Sign up for our quarterly newsletter and get the newest articles from acutecaretesting.org. Maternal reduced oxygen-carrying capability due to: - anemia In: McLaren A (ed): Advances in reproductive physiology. Clamping the umbilical cord is standard procedure when a baby is born. And what is a normal PC02 level? Case of the Missing Cord Gases: No Standing Orders or Reminder to Provider to Order Umbilical Cord Gases provide evidence of infant's condition at birth relative to acidosis & labor Need both umbilical arterial gases And umbilical venous gases Can cut & clamp cord & set aside until newborn's status is determined It signifies that this type of blood is acidic in comparison to arterial blood. Benefits of introducing universal cord blood gas and lactate analysis into an obstetric unit. Normal Arterial Blood Gas Values pH : 7.36-7.44 PaCO2 : 36-44 mm Hg HCO3 : 22-26 mEq/L Legal Notices and Disclaimer All Information contained in and produced by the Pediatric Oncall system is provided for educational purposes only. Blood is a body fluid that delivers vital substances . Umbilical-cord acidemia may indicate perinatal asphyxia and places a neonate at increased risk for hypoxic ischemic encephalopathy (HIE). But whether a value is normal or not depends often on the circumstances of the birth and other information. This acid base calculator estimates both the anion gap and provides you with an arterial blood gas interpretation. Sodium and chloride are required for anion gap calculation. Obstet Gynecol 2006; 108: 1319-22, Andersson O, Hellstrom-Westas L, Andersson D, Di Tommasso M, Seravalli V, Martini I. The readout from the machine quotes normal values based on the assumption that the sample analysed is arterial (an ABG). Instead, the exchange of gases, breathing occurs in the placenta where oxygen is transported from the mother's blood vessels into the placenta and then from the placenta through the umbilical cord to the fetus and carbon dioxide is exchanged from the fetus to the mother. Specs: Laminated 8.5 X 11 inches (21.6 X 27.9 cm) ISBN: 978-1-937967-06-2 Item No: 3rd Ed Nomo Add to cart Lactic acid is the principal metabolic acid responsible for the fall in cord-blood pH and base excess that is associated with cord-blood metabolic acidosis and birth asphyxia [28]. Input pH : Input pCO 2 : HCO 3 = Base Excess = . Experimental design in psychological research, 4th ed. The finding of isolated respiratory acidosis (i.e. Pediatr Res 2007;61:415-20. Acidosis with nuchal cords and normal Apgar scores. Remove ALL air and gently rotate for 30 seconds . ROME method for ABGs (arterial blood gases) interpretation: Solve uncompensated, partially and fully compensated ABG problems. 1,2. See also Legal info. Instructors may supply a dry-erase pen during blood gas instruction . Both umbilical cord blood venous or arterial values may be influenced by many different conditions including but not limited to: In order to examine the fetus' status, umbilical artery blood needs to be examined as this is the blood coming from the baby (as opposed blood going to the baby through the umbilical veins). Likewise, there will also be a greater associated fetal hypovolemia. Gruenwald P. Growth of the human foetus. The blood in the umbilical vein reflects the placental condition. The change is a progressive decrease in pH and base excess, and increase in pCO2 and lactate. 2008; 139: 16-20, Koshnow Q, Mongelli M. Cord blood lactate and pH values at term and perinatal outcome: a retrospective cohort study. 60 minutes. The blood samples were collected immediately after birth in the operating room and then sent for blood-gas analysis. To understand what cord blood gases are, it's helpful to know how the placenta supplies oxygen and nutrition to a baby in the womb. Info. Significant metabolic acidosis, widely defined as cord arterial blood pH <7.0 and base excess 12.0 mmol/L), occurs in around 0.5-1 % of deliveries [1]. The article begins with some background physiology/anatomy of placental/fetal circulation that highlights the all-important distinction between arterial and venous cord blood for accurate assessment of fetal/neonatal acid-base status. Analyzing cord blood gas levels is often the best indicator of hypoxia or ischemia during the delivery period. In Geneva in 1821, a French nobleman Jacques Alexandre Le Jumeau, Vicomte de Kergaradec, became the Apgar scores and umbilical artery pH have traditionally been used as objective measures of 2022 Radiometer Medical ApS | kandevej 21 | DK-2700 | Brnshj | Denmark | Phone +45 3827 3827 | CVR no. Interpreting Arterial Cord Blood Gas Values. There are five different umbilical cord gases and other measurements that can be measured and calculated separately in the umbilical artery and the umbilical vein: There are several steps involved in collecting umbilical blood cord gases: The purpose of cord blood gas analysis is to determine the acid-base status of the neonate at the moment of delivery. An infant was delivered via cesarean. If the episodes are severe enough or frequent enough, there may be insufficient time for complete recovery between episodes, and acid-base values will deteriorate over time. Intrapartum care: Care of healthy women and their babies during childbirth. Pediatrics 2005;115:950-5. The placenta is an organ which is attached to the inside of the uterine wall and connects the fetus through the umbilical cord and allows for nutrient exchange, waste elimination and gas exchange via the mothers blood supply. Molar Heat Vaporization Calculator. The general goals of oxygen therapy in the neonate are to maintain adequate arterial P a O 2 and S a O 2, and to minimize cardiac work and the work of . This calculator only differentiates between acute (pH abnormal) and compensated (pH normal). The entire team from the intake Samantha to the lawyer himself (Ron Miller) has been really approachable. CrCl Schwartz Rev. Blood Gas (Stewart) ICU Calculators-RNSH. At birth, a 10- to 20-cm segment of umbilical cord is doubly clamped and cut. Once isolated from maternal/neonatal circulation, the acid-base parameters of clamped cord blood are stable at room temperature for 60 minutes [14, 15]. Two unresolved issues militate against the routine use of cord-blood lactate alone, at the current time. As far as I am aware, cord occlusion with terminal bradycardia has never been studied separately as a cause of neonatal asphyxia. Arch Dis Child 1987;62:1276-7. At term, normal mean umbilical venous blood pressure is 4.9 mmHg, whereas normal mean aortic blood pressure is about 52 mmHg. Given these difficulties, it is widely recommended [2, 20-22] that blood from both artery and vein are sampled and analyzed, so that arterial blood results can be validated as truly arterial. Umbilical cord blood gas and acid-base analysis. Once the fetus uses this blood, it is carried away from the heart and back to the placenta by both umbilical arteries into the placenta and then to the mother. has a master's degree in medical biochemistry and he has twenty years experience of work in clinical laboratories. It is these infants who are most likely to benefit from volume expansion. If a baby has acidosis, you will see poor cord gases at birth. Because of increasing occluding forces, or as fetal blood pressure begins to falter secondary to fetal hypovolemia and cardiac hypoxia, the fetus' ability to continue umbilical artery blood flow will end. Deorari , AIIMS 2008 2 Contents 1. pH difference <0.02 and/or pCO2 difference <0.5 kPa), then the two samples almost certainly came from the same vessel, either a vein or an artery. It should look like this: Now lets solve a problem using the tic tac toe method: ABG results are the following..pH 7.24, PCO2 75, HCO3 28. Early Human Development 2010; 86: 329-38, Perlman J. Intrapartum hypoxic-ischemic cerebral injury and subsequent cerebral palsy. Australia and New Zealand J of Obstetrics and Gynaecology 2010; 50: 318-28, Dr. Amos Grunebaum, MD, FACOG is a Professor of Obstetrics and Gynecology, and among the world's leading authorities on fertility and pregnancy. HIE Calculator This tool is intended to promote identification and early referral of babies at risk for hypoxic-ischemic encephalopathy (HIE). Advantages of routine (non-selective) cord blood gas testing: Disadvantages of routine (non-selective) cord blood gas testing: Proponents of routine cord blood gas analysis also argue that it can be used as an audit of the effectiveness of the fetal monitoring and intervention strategies used in the unit to prevent significant metabolic acidosis and associated neonatal morbidity and mortality. Umbilical cord blood analysis is designed to give a picture of the acid-based balance of the infant at the moment of birth. Which interpretation of these umbilical cord and initial neonatal blood results is correct? It is also important to get accurate results. Measurements of umbilical cord blood gases may be affected by several factors related to the method of sampling, storage, and assessment, and therefore there potentially a wide variation in accuracy. (3,4) Finding a pH difference greater than 0.10 suggests either cord occlusion with terminal bradycardia or chronic fetal heart failure with terminal bradycardia. What about a PO2 level? It is vital, therefore, that the acid-base parameters (pH, base excess (BE) and lactate) derived from arterial rather than venous cord blood are used to assess neonatal condition. In one study [27], for example, the introduction of ST waveform analysis as an adjunct to fetal ECG monitoring resulted in a remarkable reduction in the prevalence of significant metabolic acidosis (0.72 % of all live births to 0.06 %). Then using 125 mL/kg (11,12) of newborn weight as the total fetal-placenta blood volume and 84 mL/kg (13) as the total blood volume of a term newborn, one could calculate the approximate upper end of blood transferred from fetus to placenta, i.e., a placental blood volume increase of approximately 20.5 mL/kg (50% of placenta blood volume: 125 minus 84 mL/kg = 41 mL/kg times 50% = 20.5 mL/kg, divided by 84 mL/kg = 24%), giving an approximate maximum transfer of 24% of the total fetal blood volume. The intrapartum acid-base status, the status of the oxygen and other gases in the fetus and the umbilical cord after birth is important in establishing the link between events before and shortly after delivery. a) Contamination of the arterial sample with an air bubble resulting . The assessment should take place within 60 minutes. It is used to determine the extent of the compensation by the buffer system and includes the measurements of the acidity (pH), levels of oxygen, and carbon dioxide in arterial blood.