Re: [ozmidwifery] Blood gasses( Long)

[Melissa Singer]

Thanks Mary for all your effort in finding these refs.  Very useful.   Melissa ----- Original Message ----- From: Mary Murphy To: ozmidwifery@acegraphics.com.au Sent: Tuesday, October 24, 2006 8:06 PM Subject: [ozmidwifery] Blood gasses( Long) This Technical report covers fetal monitoring in a really comprehensive way.  www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=hstat6.section.700   Re blood gases, I promise not to bother you again, but still having difficulties finding recent studies.   This first one appears to explain the process and meanings better than any other I have read. I excerpted some interesting points from the articles I read.  MM 1. BRITISH JOURNAL OF OBSTETRICS AND GYNAECOLOGY, 101:1054-1063, 1994 “Umbilical Cord Blood Gas Analysis at Delivery: A Time for Quality Data.” Jennifer A. Westgate, Jonathan M. Garibaldi, Keith R. Greene 2, “Postpartum Determination of Umbilical Artery Blood Gases: Effect of Time and Temperature” Moshe Manor, Isaac Blicksteina, Ynon Hazan, Orna Flidel-Rimon1, and Zion J. Hagay 1 Depts. of Obstet. and Gynecol. and Neonatol., Kaplan Hosp., 76100 Rehovot, Israel (affiliated with Hadassah-Hebrew Univ. School of Med., Jerusalem); a author for correspondence: fax 972-8-9411944, e-mail [EMAIL PROTECTED] Determination of cord blood gases and pH is recommended in all neonates with low Apgar scores to distinguish metabolic acidosis from hypoxemia or from other causes that might result in low Apgar scores (1). Although the metabolic acidosis found in cord blood is a poor predictor of long-term neurological injury (2), assessment of umbilical cord blood gas is helpful to exclude intrapartum or birth events that cause acidosis and serves as legal evidence against any alleged association with poor outcome (3). 3. Obstet Gynecol Clin North Am. 1999 Dec;26(4):695-709. Related Articles, Links Umbilical cord blood gas analysis. Thorp JA, Rushing RS. St. Luke's Hospital of Kansas City, Missouri, USA. Umbilical cord blood gas and pH values should always be obtained in the high-risk delivery and whenever newborn depression occurs. This practice is important because umbilical cord blood gas analysis may assist with clinical management and excludes the diagnosis of birth asphyxia in approximately 80% of depressed newborns at term. The most useful umbilical cord blood parameter is arterial pH. Sampling umbilical venous blood alone is not recommended because arterial blood is more representative of the fetal metabolic condition and because arterial acidemia may occur with a normal venous pH. A complete blood gas analysis may provide important information regarding the type and cause of acidemia and sampling the artery and vein may provide a more clear assessment. The sampling technique is simple and easily mastered by any treatment person in the delivery room. Preheparinized syringes ensure a consistent dose and amount of heparin. Depending on how normality is defined and on the population studied, normal ranges for umbilical cord blood gas values vary (see Table 1). In general, the lower range for normal arterial pH extends to at least 7.10 and that for venous pH to at least 7.20. Many different factors during pregnancy, labor, and delivery can affect cord blood gases. Umbilical blood sampling for acid-base status at all deliveries cannot be universally recommended because many facilities do not have the capabilities to support such a practice and in doing so may impose an excessive financial burden. Considering the costs, the accumulated published data, and the nonspecificity of electronic fetal monitoring in the evaluation of fetal oxygenation, it may be more rational to implement universal cord blood gas analysis. Care providers and institutions with the logistical capabilities in place should consider the cost efficacy of routine cord blood gas analysis because it is the gold standard assessment of uteroplacental function and fetal oxygenation/acid-base status at birth.   4. Umbilical Cord Blood Gas Analysis at Delivery S F Loh, A Woodworth, G S H Yeo (research carried out in 1994. MM) Umbilical cord blood gas values reflect the last moment of fetal oxygenation and acid base balance prior to delivery. Severe fetal acidemia is associated with increased perinatal mortality and increased risk of subsequent impaired neurological develop In acute hypoxic insult of short duration, fetal and placental blood may not have sufficient time to equilibrate and this may be reflected in a large arterial-venous difference in BDecf. However, in long-standing hypoxic insult, lactic acid produced by the baby was given time to be removed across the placenta to saturate the placental extracellular fluid compartment. In conclusion, we are sure that umbilical cord blood gas analysis is useful to ascertain whether a particular case of fetal compromise is due to "perinatal asphyxia". Selectively paired umbilical cord blood gas analysis, when properly done and correctly interpreted offers insight into metabolic events occurring in the perinatal period and enables the obstetricians to learn from individual patient. It also provides the neonatologists with a baseline of the neonate’s metabolic condition. A good blood gas in a depressed newborn should alert the neonatologist to search more diligently for other causes of neonatal depression eg. sepsis, trauma or congenital abnormalities. It also provides an objective measure for the evaluation of antepartum and intrapartum care.