How useful is intrapartum electronic fetal heart rate monitoring?

It is essential for an obstetric anesthesiologist to be aware of the fetal status before undertaking care of the laboring mother. In the last 20 years electronic fetal monitoring has been the most widely used technique of evaluating the fetus in labor. Recently however, the ability to predict or improve fetal outcome using traditional interpretation has been questioned. This review presents a summary of the current technology and interpretation of intrapartum electronic fetal monitoring, as well as a discussion of its limitations and some of the developments in this field which may help improve the accuracy of fetal assessment. The new developments in fetal monitoring discussed in this article are computerized assessment of fetal heart tracings, heart rate variability analysis, fetal electrocardiogram waveform analysis, abdominal detection of fetal ECG, fetal scalp oxygen saturation, fetal pH sampling and transcutaneous oxygen and carbon dioxide measurement.     

Fetal kidney volume and its association with growth and blood flow in fetal life: The Generation R Study

An adverse fetal environment may lead to smaller kidneys and subsequent hypertension with renal disease in adult life. The aim of our study was to examine whether maternal characteristics, fetal growth, fetal blood flow redistribution, or inadequate placental perfusion in different periods of fetal life affect kidney volume in late fetal life. We also determined if fetal kidney volume was linked to the amount of amniotic fluid. In a population-based prospective study from early fetal life, fetal growth characteristics and fetal blood flow parameters were assessed by ultrasound and Doppler examinations in 1215 women in mid- and late-pregnancy. Kidney volume was measured in late pregnancy. Maternal height and pre-pregnancy weight were associated with kidney volume. After adjustment for the same characteristics in late pregnancy, fetal growth and blood flow in mid-pregnancy were not associated with kidney volume in late pregnancy. In late pregnancy, however, all fetal growth parameters were positively linked with kidney volume. The largest effect on kidney volume was found for abdominal circumference. Signs of fetal blood flow redistribution and increased placental resistance were associated with decreased kidney volume in late pregnancy. Amniotic fluid volume was positively associated with kidney volume. Our study shows that maternal anthropometrics, fetal growth, fetal blood flow redistribution, and raised placental resistance all correlate with kidney volume.     

Effects of fetal insulin secretory deficiency on metabolism in fetal lamb

Fetal insulin secretion may be of importance in determining both fetal metabolic rate and glucose homeostasis in the resting state. To investigate this question, streptozocin (STZ) was injected into 10 late-gestation fetal lambs, and the effects of STZ on fetal pancreatic insulin storage and secretion, fetal metabolic rate, and umbilical glucose uptake were then studied. Fetal STZ injection caused a relative fetal hyperglycemia by 24 h after injection. Fetal hyperglycemia reached a maximum by 72 h and persisted for at least 10 days after injection. Neonates delivered after fetal injection were frankly diabetic. Fetal STZ injection was associated with complete suppression of both glucose- and tolbutamide-stimulated insulin release, although no changes in peripheral insulin concentration were observed when compared with controls. Fetal pancreatic insulin content was only 13% of that expected on the basis of gestational age. In a subgroup of 7 STZ-treated fetal lambs, fetal hyperglycemia was related to decrements in umbilical venoarterial difference of glucose, umbilical glucose uptake, and glucose-O2 quotient. No changes in maternal glucose homeostasis or in fetal O2 consumption were noted. The data suggest that deficient fetal insulin storage and secretion are associated with a decrement in exogenous fetal glucose entry but not in fetal metabolic rate. Whether the observed fetal changes relate to enhanced endogenous fetal glucose production with a passive decrease in maternofetal glucose transfer or are simply due to a decrease in overall fetal glucose utilization is not known. It is speculated that a quantitative decrease in pancreatic insulin secretion is responsible for the observed changes.     

Effects of Fetal pH on Local Anesthetic Transfer across the Human Placenta

Background: Fetal acidemia increases umbilical venous bupivacaine concentrations in the in situ rabbit model. The authors studied the effects of decreasing fetal pH on the rate of maternal to fetal (M-->F) clearances of lidocaine, bupivacaine, 2-chloroprocaine, and antipyrine (a nonionic marker of placental transfer) across the isolated, dual perfused, human placental cotyledon.

Methods: Maternal to fetal clearances of bupivacaine, lidocaine, 2-chloroprocaine, and antipyrine were determined at fetal pH (7.4), during progressive fetal acidemia (pH 7.2-->7.0-->6.8), and after recovery to fetal pH 7.4 in experiments with both low protein state and in those with in vivo maternal and fetal protein-binding potentials.

Results: Placental transfer of all three agents increased linearly as the fetal pH decreased. Antipyrine transfer was unaffected. Clearance of lidocaine and bupivacaine, but not 2-chloroprocaine, returned to baseline when fetal pH was restored to 7.4. When maternal and fetal protein-binding potentials were increased, clearance at fetal pH 7.4 of bupivacaine, but not lidocaine, decreased significantly. During fetal acidemia, the transfer of both agents increased, but to a lesser extent than in the low protein concentration experiments.     

膜式氧合器在胎羊体外循环中的运用

目的　为了改进胎羊体外循环技术 ,探讨膜式氧合器在胎羊体外循环中的应用。　方法　将健康怀孕山羊8只 ,采用 Dideco 90 1膜式氧合器和滚轴泵建立胎羊体外循环 ,常温 (37℃ )转流 6 0分钟 ,氧合器内充低氧混合气体 (8%O2 和 92 % N2 ) ,监测胎羊的血压、心率、血气、血清乳酸和胎盘血管阻力。　结果　胎羊体外循环中动脉氧分压 (PO2 )和二氧化碳分压 (PCO2 )维持在宫内生理水平 ,胎羊心搏有力 ,血压正常。但胎羊 p H值缓慢下降 (P<0 .0 5 ) ,血清乳酸值明显增高 (P<0 .0 1) ,胎盘血管阻力显著上升 (P<0 .0 1)。停体外循环后胎羊出现低氧、高碳酸血症和酸中毒。　结论　胎羊体外循环影响胎盘功能 ,膜式氧合器可以代替胎盘气体交换功能 ,体外循环中胎羊生理低水平 PO2 是否适合其需要值得探讨。     

Adult skin wounds in the fetal environment heal with scar formation.

OBJECTIVE: This study investigated the influence of the fetal environment on the healing characteristics of adult skin. SUMMARY BACKGROUND DATA: The remarkable ability of the fetus to heal without scarring is poorly understood. The unique qualities of fetal wound healing may be caused by the fetal environment, the fetal tissues, or a combination of both. There are numerous differences between the prenatal and postnatal environments that may play a role in the unique fetal response to injury. METHODS: Full-thickness adult sheep skin was transplanted onto the backs of 60-day-gestation fetal lambs (term, 145 days of gestation). The adult skin grafts were thus perfused by fetal blood and bathed in amniotic fluid. Previous work has demonstrated that, before midgestation, fetal lambs do not reject allogenic skin grafts. Forty days later (100 days of gestation), incisional wounds were made on both the adult skin graft and the adjacent fetal skin. The wounds were harvested 14 days postwounding and analyzed by both light microscopy and immunohistochemical testing using antibodies to collagen types I, III, and VI. RESULTS: The wounds in the adult skin grafts healed with scar formation. This observation contrasts strongly with the scarless healing of the incisional fetal skin wounds. CONCLUSIONS: This study suggests that scarless fetal skin healing properties are intrinsic to fetal skin and are not primarily the result of the fetal environment.     

胎儿手术的麻醉进展

胎儿手术的麻醉既不同于儿科麻醉也有别于产科麻醉。现就胎儿手术的麻醉所需关注的主要问题如麻醉特点及目标、母体的主要麻醉方法、子宫松弛的方法、胎儿麻醉和镇痛、胎儿的安全和监护等及其进展作一综述。     

应用三维超声体积自动测量技术评价胎儿肺发育不良

目的探讨应用三维超声体积自动测量（VOCAL）技术测量胎儿肺体积的可行性及超声肺重比（UFLB）对胎儿肺发育不良（PH）的诊断价值。方法选取经产前超声检查诊断为先天性发育异常且孕妇选择引产并同意进行尸检的胎儿35胎,胎龄16～36周。应用VOCAL技术获得胎儿肺体积,采用二维超声测得的生物参数经Hadlock方程系统自动生成胎儿质量,进而获得UFLB。将应用VOCAL技术测得的胎儿肺体积与尸检后实测的肺体积进行比较,并评价UFLB对PH的诊断价值。结果应用VOCAL技术测得的胎儿肺体积与实测的肺体积之间的差值为（-0.81±1.77）cm3。应用UFLB诊断胎儿PH的敏感度为83.33%,特异度为95.65%,阳性预测值为90.91%,阴性预测值为91.67%,诊断准确率为91.43%。结论应用VOCAL技术可准确评估胎儿肺体积,UFLB对胎儿PH的产前诊断具有一定意义。     

一氧化氮在成兔与胚胎兔创面愈合过程中含量的比较

目的 :分析胚胎无瘢痕愈合的潜在原因 ,研究NO(一氧化氮 )在成人型和胚胎型愈合过程中的差别。方法 :在已建立的胎兔创伤模型的基础上 ,用一氧化氮酶法试剂盒检测胚胎兔和成兔皮肤匀浆液中NO的含量 ,并对结果进行比较。结果 :①正常胎兔不同孕期皮肤中NO含量无差别。②正常胎兔皮肤中NO含量高于正常成兔皮肤中NO含量 (P <0 .0 1)。③创伤胎兔皮肤中NO含量高于正常胎兔皮肤中NO含量 (P <0 .0 1)。④创伤成兔皮肤中NO含量高于正常成兔皮肤中NO含量 (P <0 .0 1)。⑤创伤胎兔皮肤中NO含量高于创伤成兔皮肤中NO含量 (P <0 .0 1)。结论 :NO参与了胚胎和成年动物的创面愈合过程 ,并在两种愈合过程中存在差别     

超声评价胎儿胃泡发育的研究进展

消化道异常是一种较常见的胎儿畸形,严重者可影响胎儿正常生长发育,甚至导致死亡。准确评价胃泡发育有助于发现和确定胎儿消化道先天发育异常,且在评价胎儿胃肠道动力方面也有一定作用。本文就国内外近年来评价胃泡发育的各种指标和方法予以综述。     

Uptake and distribution of bupivacaine in fetal lambs

Direct continual measurement of placental drug transfer was introduced to evaluate more precisely the fetal uptake of a commonly used local anesthetic in obstetrics. Bupivacaine, 2.7 mg X kg-1 (base), was infused at a constant rate over 1 h into a maternal jugular vein of five chronically prepared pregnant ewes. Blood was sampled simultaneously from the umbilical vein (UV), fetal aorta (FA), and a maternal artery (MA). Fetal uptake rate was determined from the product of the bupivacaine UV-FA blood concentration difference and the umbilical flow rate (Qu). Total fetal accumulation was determined by integrating uptake rate over 5 h. Correlation of total fetal uptake and the infused mean maternal dose (r = 0.993, P less than 0.001) indicated that during the infusion, mean fetal uptake was a constant fraction (0.16) of the maternal infused dose. Total fetal uptake was linear despite wide individual changes in Qu, suggesting that within limits fetal accumulation is not Qu-dependent. Mean ovine protein binding of bupivacaine by maternal and fetal whole blood was 85.49% +/- 2.61 (SD) and by fetal blood, 40.43% +/- 9.60 (SD). Back-transfer of bupivacaine to the mother proceeded against a higher total bupivacaine concentration because unbound unionized drug concentrations in maternal blood were less than in fetal blood. At maternal-fetal equilibrium when UV and FA total blood concentrations were equal, the calculated fetal/maternal concentration ratio (f/m) (0.36) determined from the maternal and fetal protein binding and pH closely approximated the observed (0.35). The f/m increased during both fetal uptake and back-transfer and cannot be considered a good index of placental transfer.(ABSTRACT TRUNCATED AT 250 WORDS)     

Recognition and management of traumatic fetal injuries

Trauma during pregnancy is the leading non-obstetric cause of morbidity and mortality, and accounts for five per 1000 fetal deaths. Direct fetal injury due to trauma during pregnancy is rare, and limited information is available about how to optimize fetal outcomes after injury. Early recognition and appropriate management of direct fetal trauma may improve outcomes for the fetus. There are currently no available guidelines to direct management of the injured fetus. We provide a detailed literature review of the management and outcomes of direct fetal injury following blunt and penetrating injury during pregnancy, and describe a suggested initial approach to the injured pregnant patient with a focus on evaluation for fetal injury. We identified 45 reported cases of blunt trauma resulting in direct fetal injury, with 21 surviving past the neonatal period, and 33 of penetrating trauma resulting in direct fetal injury, with 24 surviving past the neonatal period. Prenatal imaging identified fetal injury in 19 cases of blunt trauma and was used to identify bullet location relative to the fetus in 6 cases. These reports were used to develop management algorithms for the injured fetus.     

Fetal surgery: general or regional anaesthesia?

Major improvements in the diagnosis and treatment of fetal malformations, including in-utero surgical repair, have occurred in the past decade. As opposed to anaesthesia for caesarean sections, a high placental drug transfer is warranted to provide adequate fetal anaesthesia and immobility, strongly favouring the use of general anaesthesia for these cases. Even though the question of fetal pain perception is still debated, studies suggest that attenuation of the fetal stress response can improve outcome. Other major concerns include the maintenance of uterine blood flow and uterine relaxation, as premature labour and delivery severely limit fetal benefits from surgery. When performing these procedures, physicians have a special responsibility to weigh maternal risks against fetal benefits and should not jeopardize the life of the mother for procedures with questionable fetal outcome.     

Fetal wound healing: an overview

The ability of fetal tissues to heal without scarring has prompted extensive research into the biochemical and molecular differences between fetal and postnatal wound healing. A thorough understanding of the basic mechanisms of fetal wound repair may to lead to approaches to correct or prevent the clinical problems encountered in abnormal adult wound healing and fetal surgery. This article contrasts the normal healing response in adults with fetal repair in animal models, highlighting investigations of extracellular matrix expression, cytokine profiles, and cellular dynamics.     

New techniques in fetal surgery.

Optimal fetal management during and after fetal surgery has been limited by an inability to reliably monitor the fetal heart rate and temperature, and by a lack of access to the fetal circulation. In order to solve these problems, we used early third trimester fetal sheep to develop: (1) an implantable radiotelemetry device that transmits the fetal electrocardiogram and temperature, and (2) an intraosseous access technique. A miniaturized radiotelemeter was implanted subcutaneously in the axilla of four fetal sheep. Safe implantation of the radiotelemeter was technically feasible and the device reliably recorded the fetal electrocardiogram and temperature both intraoperatively and postoperatively. Although many possible routes for access to the fetal circulation have been tried experimentally and clinically for both resuscitation and blood sampling, none have proven satisfactory. We assessed the use of intraosseous access in fetal sheep (n = 6) for both infusion and blood sampling. Access with an intraosseous needle was obtained in both sheep fetuses and human fetal cadavers. Blood gas values (pH, PCO2, and PO2) obtained from the medullary cavity of fetal sheep accurately reflected peripheral venous values. Resuscitation drugs reached the fetal circulation via the intraosseous route: sodium bicarbonate elevated venous bicarbonate levels from 28.4 +/- 1.7 to 31.8 +/- 2.1 mEq/dL (P < .05); injected glucose increased venous glucose levels by 520 +/- 108 mg/dL (P < .01); and injection of calcium chloride elevated venous calcium levels from 11.8 +/- 0.7 to 15.2 +/- 2.2 mEq/dL (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Spiral electrode for continuous fetal heart rate monitoring during in-utero myelomeningocele repair

Continuous fetal hemodynamic monitoring during in-utero surgery is desirable, but it is often not feasible without intermittent interruption. We report the use of a fetal spiral electrode for continuous heart rate monitoring during fetal myelomeningocele repair. Fetal echocardiography and a fetal spiral electrode were used to monitor fetal heart rate during in-utero repair at 25 weeks’ gestation. We observed good agreement between echocardiographic and spiral electrode heart rate measurements. Using the Bland-Altman approach, the mean (SD) difference between measurements was 1.8 (3.5) beats per minute with limits of agreement of −5.3 to 8.8 beats per minute. This case illuminates a potential role for a fetal spiral electrode as a real-time adjunct in fetal interventions.     

Studies in fetal wound healing, VI. Second and early third trimester fetal wounds demonstrate rapid collagen deposition without scar formation

The mechanisms that underlie the lack of scarring in fetal wounds are unknown, but probably relate to the control of collagen fibrillogenesis. The role of collagen in the fetal wound matrix is controversial, and several wound implant models have been used to evaluate collagen deposition in fetal wounds. Unfortunately, these models create an artificial wound environment and may thereby affect the results. In order to study fetal wound collagen deposition in linear wounds without artificially altering the wound environment, we applied a highly sensitive immunohistochemical technique that uses antibodies to collagen types I, III, IV, and VI. We found that collagen was deposited in fetal wounds much more rapidly than in adult wounds. Wound collagen deposition occurred in a normal dermal and mesenchymal pattern in second and early third trimester fetal lambs. These findings are consistent with the observation that the fetus heals rapidly and without scar formation. In contrast, wounds in late gestation fetal lambs showed some evidence of scar formation. Further studies may suggest ways to alter the adult wound so that it heals in a fetal manner.     

The effects of ephedrine and etilefrine on uterine and fetal blood flow and on fetal myocardial function during spinal anaesthesia for caesarean section

The effects of two vasopressors, ephedrine and etilefrine, on blood flow in maternal uterine, fetal umbilical, middle cerebral and renal arteries and on fetal myocardial function were studied by colour Doppler and M-mode echocardiography techniques during spinal anaesthesia for caesarean section. There were 7 healthy pregnant women in each treatment group. The vascular resistance of maternal uterine arteries increased significantly after both of the vasopressors while the vascular resistance of the umbilical artery remained unchanged. Ephedrine decreased the blood velocity waveform indices in the fetal middle cerebral and renal arteries, increased fetal right ventricular contractility and decreased left ventricular inner end-diastolic dimension. Fetal heart rate was unchanged. Etilefrine caused no detectable changes in fetal haemodynamics or in fetal myocardial function. These findings demonstrate that vasopressors administered for the treatment of minor maternal arterial pressure fall produce vasoconstriction in the uterine circulation during spinal anaesthesia, yet healthy fetuses seem to tolerate these haemodynamic alterations well. On the other hand, ephedrine caused changes in fetal myocardial function and in the vascular resistance of fetal middle cerebral and renal arteries, which demonstrates the potential modifying effect of vasoactive drug given to the mother on fetal haemodynamics.     

New developments in fetal monitoring for the anesthesiologist

Assessing fetal wellbeing has evolved from the ancient awareness of 'quickening' to a vast array of biophysical, imaging and biochemical methods. Because the results of these tests influence the urgency of fetal delivery and sometimes the choice of maternal anesthetic technique, it is important for anesthesiologists to understand the fundamentals of fetal monitoring and the changing face of new developments in this field. Noteworthy publications from the past year on this topic include new guidelines for the interpretation of fetal heart monitoring, advances in intrapartum fetal pulse oximetry, thresholds of acidosis associated with fetal injury, and efforts to decrease cerebral palsy through better antenatal biophysical testing.