Changes in fetal hemodynamics with terbutaline treatment and premature labor

The aim of this study was to examine the fetal hemodynamic effects of terbutaline treatment and premature labor. Image-directed pulsed and continuous wave Doppler ultrasound studies, using 3.3-MHz and 5-MHz transducers (GE PASII and ATL echocardiographic machines), were used to assess fetal cardiac blood velocities in three groups of pregnancies matched for menstrual age (MA). Group 1: 13 normal pregnancies, mean MA 31 weeks. Group 2: 7 women in premature labor prior to tocolytic therapy, mean MA 32 weeks. Group 3: 8 women treated with terbutaline, average dose 18.8 mg daily, for previous premature labor, mean MA 31 weeks. Heart rate averaged 150 bpm, 135 bpm, and 127 bpm in the terbutaline, premature labor, and normal groups, respectively, and each were significantly different from each other. Products of time velocity interval and heart rate at the aortic valves were 1603 cm +/- 140 cm, 1413 cm +/- 190 cm and 1238 cm +/- 200 cm, and at the mitral valves 1102 cm +/- 170 cm, 812 cm +/- 110 cm, and 878 cm +/- 150 cm in the terbutaline, premature labor, and the normal groups, respectively. Aortic and mitral blood velocity products of time velocity integrals and heart rates were significantly higher (p = 0.01) in the terbutaline group relative to the normal group. In addition, the terbutaline group was significantly higher than the labor group at the mitral valve (p = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic effects of ritodrine in the fetal lamb.

Ritodrine infusion to fetal lambs causes numerous metabolic perturbations including hypoxemia. To investigate these changes further and to elucidate a mechanism for the development of hypoxemia, ritodrine was infused at rate of 2.6 micrograms/min into nine chronically catheterized fetal lambs for 8, 12 or 24 hr. Plasma levels of ritodrine (20.0 +/- 2.7 ng/ml) were within the range of those reported in human fetuses exposed to ritodrine tocolysis. Fetal arterial glucose levels nearly doubled (0.72 +/- 0.07 to 1.29 +/- 0.18 mM), whereas lactate levels rose more than 5-fold (1.54 +/- 0.11 to 8.67 +/- 1.12 mM), with the latter change leading to a decline in fetal arterial pH from 7.370 +/- 0.004 to 7.273 +/- 0.033. Fetal oxygen consumption (VO2) rose from 342 +/- 35 to 407 +/- 30 mumol/min.kg via an increase in fetal fractional O2 extraction (32.0 +/- 1.1 to 49.0 +/- 1.7%). The rise in fetal O2 extraction contributed to concurrent declines in fetal arterial PO2 (21.9 +/- 0.6 to 17.0 +/- 0.5 mm Hg) and O2 content (3.7 +/- 0.2 to 2.1 +/- 0.1 mM). Umbilical venous PO2 and O2 content also fell resulting in a decline in fetal O2 delivery (DO2) from 1115 +/- 97 to 838 +/- 68 mumol/min.kg. The rise in fetal VO2 was reflected by a similar rise uterine VO2 (not significant), with the latter being accompanied by a significant increase in uterine O2 extraction and decrease in uterine venous PO2 and O2 content, perhaps contributing to the fall in fetal DO2. In conclusion, fetal hypoxemia during the infusion of ritodrine results from an increase in fetal VO2 that is not compensated for by a similar increase in umbilical or uterine DO2. These metabolic effects may put the fetus at risk, particularly in situations in which fetal DO2 is already reduced, as may occur in compromised pregnancies.     

Effect of fetal breathing movements on fetal cardiac hemodynamics.

Maximum flow velocity waveforms were studied at atrioventricular and outflow tract level in 12 cases during fetal breathing activity and in 12 cases during fetal apnea matched for maternal and gestational age and maternal parity. Gestational age ranged between 27 and 40 weeks (median 30 weeks). All flow velocity waveforms were obtained using a mechanical sector scanner with a pulsed Doppler system (carrier frequency 3.5 MHz). Time-averaged flow velocities were clearly different between inspiration and expiration at all four recording levels, reflecting changes in venous return as a result of fluctuations in intrathoracic pressure during fetal breathing activity. Percentage change between inspiration and expiration at outflow tract level was positively correlated with gestational age. Time-averaged flow velocity at mitral level and ascending aorta level was significantly higher during fetal breathing activity than during apnea, suggesting increased shunting of blood flow through the foramen ovale. Acceleration time at outflow tract level demonstrated very little change relative to inspiration and expiration.     

Cerebral hemodynamics and fetal behavioral states.

OBJECTIVE: This study aimed to evaluate the hemodynamic patterns of the proximal (M1) and distal (M2) portions of the middle cerebral artery, during different fetal behavioral states. DESIGN: The study included 20 normal singleton pregnancies at between 36 and 40 weeks of gestation. After identification of the fetal behavioral state (FBS), flow velocity evaluation was performed on the proximal and distal segments of the middle cerebral artery during 'quiescence' (FBS-1F) and 'activity' (FBS-2F). RESULTS: A statistically significant decrease of pulsatility index, reflecting a decrease of impedance to flow values, was identified in both segments of the middle cerebral artery (MCA) during 'activity', with a more marked decrease in the MCA-M2 than in MCA-M1 (M1, P = 0.0028; M2, P = 0.00000085). The mean fetal heart rate during 'quiescence' was significantly lower than during 'activity' (P = 0.0047). However, there was no significant correlation between the pulsatility index of both segments of the middle cerebral artery and the fetal heart rate during different fetal behavioral states. CONCLUSIONS: The results of this study provide evidence of the influence of different fetal behavioral states on fetal cerebral hemodynamic patterns. We believe it is better to sample the proximal segment in clinical practice because it is less influenced by fetal behavioral state. This information should be considered when evaluating fetal cerebral hemodynamics.     

Doppler evaluation of fetal hemodynamics

Human umbilical hemodynamics was investigated in 27 pregnant patients with gestational ages from 29 to 43 weeks using a pulsed Doppler flowmeter. The signals were analyzed by Fast Fourier Transform using a minicomputer. Coherent averaging of the signals, along with the computation of maximum velocity, mean velocity and the first moment of Fourier spectra about the zero frequency axis were performed. Hemodynamic indices were measured utilizing a comprehensive feature characterization technique of the blood flow velocity waveform. It was observed that coherent averaging reduced spectral variance thus relatively simplifying the analyses. The Pulsatility Index based on the first moment of the Fourier spectra indicated a higher umbilical flow change during the fetal cardiac cycle, than that predicted by the peak velocity Pulsatility Index. We also observed a high Pulsatility Index in association with three cases of oligohydramnios indicating the possibility of an elevated placental circulatory impedance. Variation in the peak velocity up to 20% was also noted with fetal breathing movements. Further studies are necessary to determine the clinical relevance of these findings.     

The short-term effect of nifedipine tocolysis on placental, fetal cerebral and atrioventricular Doppler waveforms.

OBJECTIVE: To evaluate the effect of nifedipine on placental and fetal middle cerebral and atrioventricular Doppler waveforms. METHODS: Doppler waveforms of uterine (UtA), umbilical (UA) and middle cerebral (MCA) arteries and both atrioventricular valves were measured from 21 pregnant women/fetuses prior to and during nifedipine therapy for preterm labor. Maternal and fetal heart rates (FHR), maternal systolic and diastolic blood pressure, the Doppler pulsatility index and systolic/diastolic ratio of the UtA, UA and MCA were measured. The total time velocity integrals (TVI) of tricuspid and mitral valves and their E-wave/A-wave (E/A) TVI ratios were measured. Wilcoxon signed pairs test was used to compare the differences in Doppler parameters before and at 3 h after nifedipine loading up to a maximum dose of 40 mg. RESULTS: Fetal arterial and UtA Doppler parameters were not different before and after nifedipine therapy. Blood flow across the atrioventricular valves and the TVI were equally unaffected by nifedipine. The TVI x FHR product was also unchanged following nifedipine therapy. CONCLUSIONS: In women with otherwise uncomplicated pregnancies, nifedipine loading and tocolysis are generally well tolerated by the mother. Placental and fetal cerebral arterial blood flow, fetal systolic and diastolic cardiac function and downstream distribution of fetal cardiac output are unaffected by nifedipine loading. These results apply to women with unchanged vital parameters. Further studies are necessary to show long-term effects of nifedipine therapy and may help to refine choice of tocolytic agents.     

感染性休克患者血流动力学和氧合功能的变化

目的：研究感染性休克患者血流动力学和氧合功能的变化。方法：因输液致感染性休克患者８ 例,入ＩＣＵ后置入Ｓｗａｎ Ｇａｎｚ导管测定中心静脉压（ＣＶＰ）、肺动脉平均压（ＭＰＡＰ）、肺毛细血管嵌压（ＰＣＷＰ）;用热稀释法测定心排血量（ＣＯ）,同时监测平均动脉压（ＭＡＰ）和心率。于入ＩＣＵ 后１、２、３、４ 和５ 日内进行血气分析,计算出氧输送（ＤＯ２ ）、氧耗量（ＶＯ２ ）、氧摄取率（Ｏ２ｅｘｔｒ）、肺内分流率（Ｑｓ／Ｑｔ）、肺泡 动脉血氧分压差〔Ｐ（Ａ－ ａ）Ｏ２ 〕、外周血管阻力指数（ＳＶＲＩ）、肺血管阻力指数（ＰＶＲＩ）和心排指数（ＣＩ）。结果：感染性休克患者入ＩＣＵ 后１ 日内ＭＡＰ和ＣＶＰ分别降低３８．５％ 和４２．８％ （Ｐ均＜ ０．０１）;入ＩＣＵ 后３ 日内ＰａＯ２ 降低３０．６％ ～４３．２％ ,〔Ｐ（Ａ－ ａ） Ｏ２ 〕和Ｏ２ｅｘｔｒ分别升高３８．８％ ～５０．３％ 和８．０％ ～３２．０％ （Ｐ均＜ ０．０１）;入ＩＣＵ 后５ 日内ＣＩ、ＰＶＲＩ、ＭＰＡＰ、ＤＯ２ 、ＶＯ２ 和Ｑｓ／Ｑｔ分别升高１２．０％ ～２２．３％ 、３５．３％ ～５８．２％ 、１７．２％ ～２４．８％ 、１１．９％ ～２０．９％ 、１４．９％     

骨盆骨折后血流动力学的变化

目的：探讨骨盆骨折后血流动力学的变化特点。方法：对进入急救部的18例严重骨盆骨折的患者经颈内静脉置入Swan-Ganz导管进行了动态的血流动力学监测，对死亡者和存活者血流动力学的变化特点进行了分析。结果：死亡者和存活者的血流动力学变化有明显的不同，死亡者7例均于入院后24h内死亡，经液体复苏后4～8h，职显著降低，MAP、CI显著升高，但10h之后MAP、CI又降低非常显著，MPAP、PCWP显著升高，CVP升高非常显著。存活者11例，经液体复苏后血流动力学逐渐平稳，复苏4～6h后职降低非常显著，MAP、CVP、MPAP、PCWP、CI均升高非常显著，16～24h之后血流动力学参数趋于稳定并逐渐回到正常范围。结论：经液体复苏后血流动力学难以稳定者死亡率高。     

病毒性脑炎昏迷患者脑血流动力学变化分析

目的通过观察病毒性脑炎患者昏迷过程中的脑血流动力学情况,探讨经颅多普勒超声（TCD）的参数与格拉斯哥昏迷评分（GCS）的相关性,发现更好的适时、客观评估病情的TCD参数。方法应用TCD动态观察24例病毒性脑炎昏迷患者入院后第1、3、7天的大脑中动脉血流,同时记录下TCD各参数和GCS评分。结果 PI值与GCS评分呈显著负相关（r=-0.72）;24例患者中有4例出现涡流信号,频窗充填,最后全部死亡;昏迷患者发病3 d左右病死率较高,后趋稳定。结论 TCD的PI值比GCS评分能更好的反映出患者的病情,对指导临床治疗有一定帮助;根据连续PI值和频谱检测可以初步了解病情发展趋势、判断预后。     

颈动脉支架置入后的血流动力学改变

颈动脉支架置入可有效改善脑血流灌注,改善狭窄段血流速度,被认为是治疗颈动脉狭窄的有效方法之一。但由于球囊扩张、支架置入机械扩张和牵拉,颈动脉窦引起内膜和动脉粥样硬化斑块的表面撕裂,调整了颈动脉壁顺应性,改变了颈动脉受体的敏感性,引起血液动力学不稳定和斑块碎片脱落,引起低血压、心动过缓、高血压及血管栓塞等并发症,如何控制和减少上述并发症的发生是目前研究的主要问题。选择相对柔软的,侧弯性能较好,且直径应比狭窄处实测直径大1.0～2.0mm的支架,提高置入操作技术,可以减轻支架置入过程中球囊扩张及支架膨胀时对粥样斑块的挤压与切割作用,防止斑块脱落,同时使用滤器脑保护装置以过滤较大组织碎片,阻止较大微栓子进入脑循环,提高颈动脉支架置入的安全性。     

羟苄羟麻黄碱治疗早产的用药护理

通过对68例羟苄羟麻黄碱（安宝）治疗早产用药理的总结。强调在用药的护理过程中，要详细查询病史；做好解释和指导工作；严密监测孕妇和胎儿的心率情况；血压变化；血糖血钾的变化；加强心理护理；注意药物的配伍禁忌。     

Changes in fetal cardiac geometry with gestation: implications for 3- and 4-dimensional fetal echocardiography.

OBJECTIVE: Three- and 4-dimensional fetal echocardiography can be performed using novel algorithms. However, these algorithms assume that the spatial relationships among cardiac chambers and great vessels are constant throughout gestation. The objective of this study was to determine whether changes in fetal cardiac geometry occur during gestation. METHODS: A cross-sectional study was conducted by reviewing 3- and 4-dimensional volume data sets from healthy fetuses obtained between 12 and 41 weeks of gestation. Volume data sets were examined using commercially available software. Parameters measured included angles between: (1) the ductal arch and fetal thoracic aorta; (2) the ductal arch and aortic arch; and (3) the left outflow tract and main pulmonary artery, as seen in the short axis of the heart. The mean angle from the left outflow tract to the short axis was calculated. Nonparametric statistics were used for analysis. RESULTS: Eighty-five fetuses were included in the study. The angle between the ductal arch and the fetal thoracic aorta decreased with gestational age (Spearman rho coefficient: -0.39; P < .001). In contrast, the angle between the ductal arch and aortic arch, and the mean angle between the left outflow tract and the short axis of the heart increased with gestational age (Spearman rho coefficients: 0.45 and 0.40, respectively; P < .001). CONCLUSIONS: (1) Changes in fetal cardiac geometry were shown with advancing gestational age. (2) Proposed algorithms for the examination of the fetal heart with 3-dimensional ultrasonography may need to be adapted to optimize visualization of the standard planes before 26 weeks of gestation.     

胎儿超声心动图血流动力学参数与孕龄的关系

目的 探讨孕20~34周正常胎儿各孕周心脏房室瓣口、大动脉瓣口、胎儿静脉系统及重要生理通道的血流峰值速度随孕龄增长的变化规律。方法 回顾性分析2529名孕龄20~34周的正常单胎胎儿超声心动图资料,应用回归分析检测各参数与孕龄的相关性。结果 正常胎儿二尖瓣口和三尖瓣口舒张早期E峰、舒张晚期A峰和E峰/A峰,主动脉瓣口和肺动脉瓣口收缩期峰值流速,主动脉弓横弓部和动脉导管收缩期峰值流速和舒张期峰值流速,肺静脉左心房开口处收缩期S峰、舒张期D峰和心房收缩期A峰均随孕周增加略有增加;下腔静脉收缩期S峰、舒张期D峰及心房收缩期A峰无明显变化。上述胎儿血流动力学参数均与孕周存在相关关系(P均<0.05)。结论 胎儿超声心动图技术可评价心脏血流动力学状态,为胎儿超声心动图检查提供指导。     

Changes in left heart hemodynamics after technically successful in-utero aortic valvuloplasty.

OBJECTIVE: Severe aortic stenosis in the mid-gestation fetus can progress to hypoplastic left heart syndrome (HLHS). @ In-utero aortic valvuloplasty is an innovative therapy to promote left ventricular growth and function and potentially to prevent HLHS. This study evaluated the effects of mid-gestation fetal balloon aortic valvuloplasty on subsequent fetal left ventricular function and left heart Doppler characteristics. METHODS: We reviewed fetuses with aortic stenosis that underwent attempted in-utero aortic valvuloplasty between 2000 and 2006. Pre-intervention and the latest post-intervention fetal echocardiograms were analyzed to characterize changes in left heart function and Doppler characteristics in utero. RESULTS: Forty-two fetuses underwent attempted aortic valvuloplasty during the study period, 12 of which were excluded from analysis secondary to inadequate follow-up data, termination or fetal demise. Study fetuses (n = 30) underwent pre-intervention echocardiography at a median gestational age of 23 weeks, and were followed for a median of 66 +/- 23 days post-intervention. In 26 fetuses, aortic valvuloplasty was technically successful. Among these 26, left heart physiology was abnormal pre-intervention and improved or normalized after intervention in most cases: biphasic mitral inflow was present in 5/25 (20%) cases pre-intervention and in 21/23 (91%) post-intervention (P < 0.001); moderate or severe mitral regurgitation was present in 14/26 (54%) cases pre-intervention and in 5/23 (22%) post-intervention (P = 0.02); bidirectional flow across the patent foramen ovale was present in 0/26 cases pre-intervention and in 6/25 (24%) post-intervention (P = 0.01); antegrade flow in the transverse arch was present in 0/25 cases pre-intervention and in 17/26 (65%) post-intervention (P < 0.001). The left ventricular ejection fraction increased from 19 +/- 10% pre-intervention to 39 +/- 14% post-intervention (P < 0.001). These changes were not observed in control fetuses (n = 18). CONCLUSION: Fetal aortic valvuloplasty, when technically successful, improves left ventricular systolic function and left heart Doppler characteristics.     

Clearance and disposition of ritodrine in the fluid compartments of the fetal lamb during and after constant rate fetal intravenous infusion

The disposition of the beta-2 adrenoreceptor agonist, ritodrine, has been examined in the fetal lamb during and after constant rate fetal intravenous infusion (8-24 h). Samples were collected from the fetal femoral artery, umbilical vein, maternal femoral artery, uterine vein, fetal trachea and the amniotic activity for ritodrine quantitation. The amniotic fluid was also analyzed for conjugated metabolites of ritodrine. Ritodrine appears to be cleared across the sheep placenta only to a limited extent (placental clearance 9.2 +/- 2 ml/min/kg; mean +/- S.E.M.). There is, however, significant fetal nonplacental clearance of ritodrine (fetal nonplacental clearance 52.8 +/- 8.0 ml/min/kg). At least part of this clearance appears to be due to fetal drug metabolism, as evidenced by the accumulation of glucuronide conjugates of ritodrine in the amniotic fluid. Ritodrine was also shown to accumulate in the amniotic and fetal tracheal fluids and persist after fetal arterial plasma ritodrine concentrations became undetectable. The accumulation of ritodrine in the tracheal fluid may be of pharmacologic significance, given the well documented, potent effects of beta-2 agonists on fetal lung function and development.