Cardiovascular response to dopamine in hypotensive preterm neonates with severe hyaline membrane disease

The effect of low dose (2, 4, and 8 g/kg per min) dopamine infusion on blood pressure, heart rate and renal function was studied in 18 hypotensive, preterm infants with severe hyaline membrane disease (HMD). Significant dose-related effects found during dopamine infusion were systolic and diastolic blood pressure elevation and diuretic effect, while heart rate increase occurred only with 8 g/kg per min of the drug. This indicates, that in the preterm neonate, dopamine at low doses has a pronounced effect on the alpha-and dopamine-receptors, while its beta-receptor stimulating activity is minimal. We demonstrated a significantly decreased metabolic clearance rate of dopamine in preterm infants. Thus, beside the differences in the vascular receptors' maturation, the decreased metabolic clearance rate should also be taken into account when explaining the cardiovascular and renal effects of low dose dopamine infusion in these babies. Dopamine was found to be useful in normalizing low arterial blood pressure, in improving impaired peripheral circulation, and in producing a marked diuresis in hypotensive preterm neonates with severe hyaline membrane disease.Abbreviations CVP central venous pressure - HMD hyaline membrane disease - tcpO₂ transcutaneous oxygen tension - TPVR total peripheral vascular resistance     

Characteristics of the cardiovascular system in children with primary arterial hypotension

Overall 120 children aged 12 to 15 years with primary arterial hypotension and different variants of the disease course (grave, of medium gravity or mild) were examined. The control group was made up to 50 normal children. The program of the examination included electrocardiography, echocardiography, tetrapolar chest rheography and bicycle ergometry. It has been established that in children with arterial hypotension, the intracardiac hemodynamics undergoes compensatory adaptive reconstruction characterized by the enhancement of contractile and pump functions of the myocardium combined with the increased relaxation capacity. The central hemodynamics is characterized by the lowering of the general peripheral vascular resistance. The functional potentialities of the cardiovascular system decline, manifesting in the form of a decrease of exercise tolerance in association with energy losses necessary for its performance. The use of bicycle ergometry made it possible to delineate dysadaptation reactions of arterial pressure to exercise, modified by hereditary factors.     

Increased hypoxemia in neonates secondary to the use of continuous positive airway pressure.

Five neonates are presented who, while receiving continuous transpulmonary pressure, developed increased systemic arterial hypoxemia, which was relieved when this therapeutic modality was decreased or discontinued. Three of the five had chest radiographs consistent with hyaline membrane disease: the other two had atypical radiographs. None had evidence of air leaks. Levels of positive airway pressure utilized when the hypoxemia was noted ranged from 5 to 15 cm H2O. Calculated shunt fractions (Qs/Qt) improved from a mean of 73% to 37% when the continuous positive airway pressure was lowered. The site of shunting in these infants could have been in the lung or through anatomic extrapulmonary shunts. Improvement in total cardiac output may also have contributed to the improved oxygenation. This paradoxical effect of continuous transpulmonary pressure appears to be mediated through changes in the pulmonary vascular resistance brought about by the continuous transpulmonary pressure.     

Changes in Intracranial Arterial Blood Flow Velocities during Surgical Ligation of the Patent Ductus Arteriosus

ABSTRACT. A combined continuous and range-gated Doppler instrument was used to assess intracranial arterial blood flow velocity changes in infants and neonates undergoing surgical ligation of the Ductus Arteriosus (DA). Continuous recordings during DA closure in six infants (3.5-10 months old), showed an abrupt increase in diastolic blood flow velocity simultaneous with an increase in systolic and diastolic arterial blood pressure. In five infants, these changes were followed by a rapid fall in systolic and diastolic blood pressure without a concomitant change in blood flow velocity, which may be secondary to a rapid fall in intracranial vascular resistance. The mean blood flow velocity increase following DA closure was 27 % (8-43 %) and the changes in diastolic and mean blood flow velocity were significant (p<0.01). In seven preterm neonates (24-28 weeks) studied before and after surgery, a mean blood flow velocity increase of 50 % (14-115 %) (p<0.01), mainly due to an increase in diastolic blood flow velocity (p<0.01), was recorded. These rapid intracranial hemodynamic changes during surgical DA closure should be taken into consideration when selecting techniques for DA closure.     

Changes in intracranial arterial blood flow velocities during surgical ligation of the patent ductus arteriosus

A combined continuous and range-gated Doppler instrument was used to assess intracranial arterial blood flow velocity changes in infants and neonates undergoing surgical ligation of the Ductus Arteriosus (DA). Continuous recordings during DA closure in six infants (3.5-10 months old), showed an abrupt increase in diastolic blood flow velocity simultaneous with an increase in systolic and diastolic arterial blood pressure. In five infants, these changes were followed by a rapid fall in systolic and diastolic blood pressure without a concomitant change in blood flow velocity, which may be secondary to a rapid fall in intracranial vascular resistance. The mean blood flow velocity increase following DA closure was 27% (8-43%) and the changes in diastolic and mean blood flow velocity were significant (p less than 0.01). In seven preterm neonates (24-28 weeks) studied before and after surgery, a mean blood flow velocity increase of 50% (14-115%) (p less than 0.01), mainly due to an increase in diastolic blood flow velocity (p less than 0.01), was recorded. These rapid intracranial hemodynamic changes during surgical DA closure should be taken into consideration when selecting techniques for DA closure.     

Arginine vasopressin to manage hypoxemic infants after stage I palliation of single ventricle lesions

OBJECTIVE: Management of patients with single ventricle physiology following stage I palliation procedures is often challenging, with optimization of the ratio of pulmonary-to-systemic blood flow as an important goal. Persistent hypoxemia may be a manifestation of elevated pulmonary vascular resistance and therefore decreased blood flow to the lungs. In such situations, the use of arginine vasopressin to increase systemic vascular resistance may be an effective strategy to improve pulmonary blood flow and maintain adequate pulmonary-to-systemic blood flow ratio. We describe three infants in whom persistent hypoxemia improved after institution of arginine vasopressin. DESIGN: Retrospective chart review. SETTING: Twenty-four bed medical-surgical pediatric intensive care unit at a large tertiary care academic hospital. PATIENTS: Three neonates with single ventricle physiology who received arginine vasopressin in the setting of hypoxemia following stage I palliation. RESULTS: Arginine vasopressin was initiated in all three patients for hypoxemia with a goal to increase systemic vascular resistance and generate a higher driving pressure for pulmonary blood flow. Twelve hours after arginine vasopressin initiation, systemic arterial saturation as determined by pulse oximetry and blood pressure increased, whereas heart rate, inotrope score, and Fio2 decreased in all three patients. Urine output was maintained and arterial lactate decreased during this time. Pulmonary-to-systemic flow ratio increased in one patient in whom it could be determined. CONCLUSION: In patients with single ventricle physiology and persistent hypoxemia following stage I palliation, administration of arginine vasopressin could improve oxygenation possibly by increasing systemic vascular resistance and therefore the pulmonary blood flow.     

Effect of blood pressure cuffs on neonatal circulation: Their potential application to newborns with persistent pulmonary hypertension

The contribution of vasoactive pharmacologic agents to the care of the infant with primary pulmonary hypertension of the newborn (PPHN) is hampered by their limited ability to act selectively on different vascular beds. In contrast, blood pressure (BP) cuffs decrease flow and increase resistance only in the extremities around which they are applied. They therefore offer a means of increasing systemic vascular resistance without affecting pulmonary vascular resistance, a hemodynamic effect that may be particularly desirable among PPHN patients receiving vasodilators. We studied the effect of BP cuffs on the circulation of nine healthy neonates and three infants with severe PPHN. Among the healthy neonates, inflation of the cuffs to 20 mmHg had no discernible hemodynamic effect. Inflation to systolic pressures, however, caused the left ventricular preejection period to increase from 36±9 ms to 45±10 ms, the end-diastolic dimension to increase from 1.80±0.16 cm to 1.92±0.16 cm, and the cardiac output to fall to 87±12% of baseline (allp<0.05)—changes indicative of an increase in systemic vascular resistance. Application of BP cuffs to the patients with PPHN was associated with 10–25 mmHg increases in transcutaneous arterial oxygen tensions. Administration of tolazoline to these patients while the cuffs were inflated resulted in additional 10–20 mmHg increases and did not precipitate hypotension. These observations suggest that BP cuffs can play a useful role in the management of patients with PPHN.     

Plasma endothelin concentration: Relation with vascular resistance and comparison before and after balloon dilatation procedures

Endothelin (ET) is a potent vasoconstrictor peptide with an as yet uncertain physiological role in cardiovascular disease. We measured blood plasma ET concentrations using a recently developed radioimmunoassay and analysed the relations between ET concentration, systemic arterial pressure and systemic vascular resistance. In addition, ET levels before and after percutaneous balloon valvuloplasty and angioplasty were measured. Fifty-one patients were studied: (1) 13 patients with small left-to-right shunting or Kawasaki heart disease (age ranged from 4 to 144 months); (2) 10 patients who had undergone ballon valvuloplasty or angioplasty (age ranged from 1 to 233 months) and (3) 28 healthy infants and children (age ranged from 3 to 152 months). Systemic vascular resistance was calculated by the formula (mean aortic pressure — mean right atrial pressure) X 80/cardiac output (dyne·sec·cm^–5). Plasma ET concentrations in healthy children less than 2 years were significantly higher than those over 2 years (2.48±0.62 vs 1.31±0.53 pg/ml). In eight patients in groups 1 and 2, plasma ET concentration in the pulmonary artery (2.00±0.43 pg/ml) was significantly lower than that in the femoral vein (2.39±0.69 pg/ml) and aorta (2.23±0.59 pg/ml), suggesting ET secretion derived from endothelial cells in peripheral pulmonary vessels. There was a significant positive correlation between ET concentrations in the femoral vein and systemic vascular resistance (r=0.55,p<0.05). After balloon dilatation ET concentration rose from 2.15±0.82pg/ml to 2.61±1.38 pg/ml. These results suggest that ET may be a stress-induced hormone which is secreted by the transient hypotension following percutaneous balloon dilatation and which regulates peripheral vascular tonus.     

新生儿血型不合溶血病丙种球蛋白治疗安全性和有效性的Meta分析

目的 新生儿母婴血型不合溶血病仍是新生儿早期高胆红素血症的主要病因,严重者需要光照及交换输血治疗.早期静脉使用丙种球蛋白可以在一定程度上阻断溶血.本研究通过Meta分析评价静脉滴注丙种球蛋白对新生儿血型不合溶血病的治疗作用及安全性.方法 使用相关检索词检索MEDLINE、Cochrane Library、EMBASE、CNKI及CBM数据库,获得关于静脉滴注丙种球蛋白治疗新生儿Rh及ABO血型不合溶血病的临床随机对照试验,采用Review Manager 4.2统计软件对数据进行Meta分析.结果 共纳入6篇文献、456例溶血病新生儿.其中4篇文献纳入Rh血型不合溶血病患儿,共109例;4篇文献纳入ABO血型不合溶血病患儿,共347例.各研究中丙种球蛋白治疗组和对照组新生儿的胎龄、体重及性别等均无统计学差异.静脉滴注丙种球蛋白联合光疗组新生儿相对于单纯光疗组新生儿,平均光疗时间缩短(加权均数差-15.42,95%可信区间-29.00～-1.85),换血人数比率明显减少(相对危险度0.25,95%可信区间0.17～0.39),平均住院时间缩短(加权均数差-25.44,95%可信区间-36.93～-13.94),但是对降低血清最高胆红素值的效果不明显(加权均数差-29.91,95%可信区间-78.24～18.42),对晚期贫血的发生也无明显作用.没有研究发现静脉应用丙种球蛋白有明显的不良反应.结论 Meta分析支持静脉滴注丙种球蛋白对新生儿血型不合溶血病有一定治疗效果,可缩短光疗时间,减少换血次数,但还需要更严格设计的大样本双盲随机对照试验,并应进行较长期的随访研究.     

Cardiovascular effects of carbon dioxide in ventilated preterm infants

Sick preterm infants may, under certain conditions, demonstrate blood pressure passive cerebral blood flow in response to changes in arterial carbon dioxide tension. Blood pressure in turn depends on cardiac output and peripheral resistance. A Doppler technique for assessing cardiac output compared favourably in terms of reproducibility to a thermodilution technique in a group of infants undergoing cardiac catheterization for congenital heart disease. Doppler was subsequently used to monitor changes in cardiac output following an increase in arterial carbon dioxide tension of 1 kPa in 25 ventilated preterm infants. Blood pressure increased significantly (p = 0.006). However, heart rate did not change significantly (p = 0.16) and, in addition, both stroke and minute volume decreased (p = 0.023, p = 0.02, respectively). This suggests that accompanying changes in components of peripheral resistance exert important effects on blood pressure in the preterm neonate in response to changes in arterial carbon dioxide tension.     

Chloralose alters both basal hemodynamics and cardiovascular responses to alveolar hypoxia in chronically instrumented, spontaneously breathing lambs

We studied the effects of chloralose anesthesia on the basal hemodynamic state and on the cardiovascular response to alveolar hypoxia in chronically instrumented, spontaneously breathing lambs, compared with responses to the saline vehicle. Chloralose significantly increased heart rate (23%), mean systemic arterial pressure (11%), systemic vascular resistance (21%), mean pulmonary arterial pressure (23%), and pulmonary vascular resistance (46%) (n = 30, p less than 0.05, ANOVA). These changes were unrelated to baseline tone of the circulation, cardiac output, mean left atrial pressure, or physiologically important changes in arterial blood gas tensions. In addition, chloralose-treated lambs had increased heart rate, systemic vascular resistance, and pulmonary vascular resistance compared to controls during alveolar hypoxia (13-15% FiO2). Importantly, chloralose-treated lambs did not increase their cardiac output during alveolar hypoxia as did control lambs. During hypoxia, systemic vascular resistance remained elevated in chloralose-treated lambs, but declined in control lambs. Chloralose has been recommended as an ideal anesthetic agent for cardiovascular experimentation. Our data suggest that chloralose-induced alterations in basal hemodynamics and in cardiovascular responses to alveolar hypoxia represent an uncontrolled variable in acute experimental studies. Complex cardiovascular alterations caused by anesthesia should be considered in experimental design.     

Effects of Intralipid infusion on hemorheology and peripheral resistance in neonates and children

Deleterious microcirculatory effects of Intralipid (IL) infusion may be caused by hemorheological or vascular effects. The aim of this investigation was to study vascular and hemorheological effects of IL in preterm and fullterm neonates and children. Ten preterm newborns, 10 fullterm neonates, and 10 children received an initial infusion of IL (0.6 g/kg) over 4 h. Calf blood flow (venous occlusion plethysmography), blood pressure (Dinamap), whole blood and plasma viscosity (capillary viscometer), red blood cell deformability (rheoscope), and erythrocyte aggregation (aggregometer) were measured before and after administration of IL. Plasma triglyceride levels showed the greatest increase in preterm infants. Whole blood viscosity decreased by about 10% in all three groups because of a similar reduction in hematocrit. Red blood cell aggregation decreased by about 20% after IL infusion. Blood pressure rose by 10%, and peripheral blood flow declined by about 10% in the three groups. Vascular hindrance, a calculation of blood pressure divided by blood flow and viscosity, was raised by about 20%, suggesting marked vasoconstriction of peripheral arteries. Vasoconstriction rather than hemorheological changes during infusion of IL may play a crucial role in the pathogenesis of circulatory alterations in parenterally-fed neonates.     

Role of prostanoids in the regulation of cerebral blood flow during normoxia and hypoxia in the fetal sheep

The fetal cardiovascular responses to hypoxia include decreased peripheral blood flow and increased cerebral, cardiac, and adrenal blood flow. Prostanoids, metabolites of cyclooxygenase enzyme activity, have potent effects on vascular tone in both the adult and the fetus. To examine the role of prostanoids in the regulation of fetal cerebral blood flow (CBF) during acute hypoxic stress, eight near term fetal sheep were studied after infusing vehicle or diclofenac, a cyclooxygenase inhibitor, followed by a 30-min period of hypoxia (arterial Po(2) 12 Torr). In the control experiments, CBF, measured continuously with laser Doppler flowmetry, increased to 148% of baseline values (p < 0.01) and cerebral vascular resistance decreased to 70% of baseline values after 30 min of hypoxic stress. During diclofenac infusion, hypoxia resulted in a CBF increase to only 129% of baseline, a significant attenuation (p < 0.05), accompanied by decreased plasma prostanoid concentrations. Increases in mean arterial blood pressure during hypoxia were also attenuated by diclofenac infusion. Flow and pressure responses were not accompanied by changes in cerebral vascular resistance. These results indicate that prostanoids indirectly modulate fetal CBF responses to hypoxia, but that their effects are mediated through modulation of systemic rather than cerebral vascular tone.     

肾上腺髓质素在先天性心脏病中的测定及临床意义

目的：肾上腺髓质素(ADM)对心血管疾病有多方面的影响,但其与先天性心脏病关系的研究较少。该实验通过检测不同类型先天性心脏病患儿体内ADM的变化,分析ADM在先天性心脏病病理生理中的作用。方法：筛选住院的48例先天性心脏病患儿,经超声心动图及心导管检查术证实,在心导管检查术中测定血流动力学指数及采血备测,依据血流动力学特征分为高肺血流非肺动脉高压组、高肺血流并肺动脉高压组、紫绀组,平均肺动脉压(mPAP)>20 mmHg为肺动脉高压的标准。选6例川崎病痊愈患儿作为对照组。采用特异性放射免疫法检测血浆ADM的水平。结果：先天性心脏病患儿股静脉中的血浆ADM水平较股动脉明显增高(P<0.05);与对照组相比,高肺血流并肺高压组及紫绀组中的ADM明显增高,均P<0.01;ADM与主动脉平均压(mSAP)、混合静脉血氧饱和度(MVsat)、主动脉血氧饱和度(AOsat)及肺血管阻力(Rp)之间有密切的关系。结论：高肺血流并肺动脉高压和紫绀型先天性心脏病患儿的ADM水平增高,ADM的变化同肺动脉阻力和缺氧有密切关系,推测ADM水平的升高可能有助于减轻肺动脉阻力和改善缺氧。     

中重度缺氧缺血性脑病新生儿亚低温治疗诱导期血流动力学的变化探讨

目的 探讨中重度缺氧缺血性脑病(HIE)新生儿在实施全身亚低温治疗诱导低温阶段的血流动力学的变化.方法 选取2017年7月至2020年4月在广东医科大学附属东莞儿童医院新生儿科进行全身亚低温治疗的HIE患儿21例,采用亚低温治疗仪将新生儿直肠温度在1～2 h诱导降至34℃并维持在该水平72 h.期间采用阻抗法进行无创血...     

Effect of limb cooling on peripheral and global oxygen consumption in neonates

AIM: To evaluate peripheral oxygen consumption (VO(2)) measurements using near infrared spectroscopy (NIRS) with arterial occlusion in healthy term neonates by studying the effect of limb cooling on peripheral and global VO(2). SUBJECTS AND METHODS: Twenty two healthy term neonates were studied. Peripheral VO(2) was measured by NIRS using arterial occlusion and measurement of the oxyhaemoglobin (HbO(2)) decrement slope. Global VO(2) was measured by open circuit calorimetry. Global and peripheral VO(2) was measured in each neonate before and after limb cooling. RESULTS: In 10 neonates, a fall in forearm temperature of 2.2 degrees C (mild cooling) decreased forearm VO(2) by 19.6% (p < 0.01). Global VO(2) did not change. In 12 neonates, a fall in forearm temperature of 4 degrees C (moderate cooling) decreased forearm VO(2) by 34.7% (p < 0.01). Global VO(2) increased by 17.6% (p < 0.05). CONCLUSIONS: The NIRS arterial occlusion method is able to measure changes in peripheral VO(2) induced by limb cooling. The changes are more pronounced with moderate limb cooling when a concomitant rise in global VO(2) is observed. Change in peripheral temperature must be taken into consideration in the interpretation of peripheral VO(2) measurements in neonates.     

转化生长因子β/骨形成蛋白通路与肺动脉高压遗传学机制的研究进展

肺动脉高压由多种心、肺疾病所致,以动脉压力进行性升高、肺血管阻力逐渐增加为特征,最终导致右心衰竭和死亡,其发病机制至今尚未完全阐明.近期有研究发现,转化生长因子β/骨形成蛋白通路对肺动脉高压的发生发展可产生重要影响.针对转化生长因子β/骨形成蛋白通路的研究为肺动脉高压的防治提供了新的理论依据.该文就转化生长因子β/骨形成蛋白通路与肺动脉高压遗传学机制作一综述.     

Paediatric pulmonary vascular disease

Pulmonary vascular disease comprises any congenital or acquired pathology of the intrinsic pulmonary vessels with the unique feature of pulmonary arteries carrying unsaturated blood and pulmonary veins carrying oxygenated blood. Pulmonary hypertension (PH) ensues when pulmonary vascular disease affects at least 50% of the capillary resistance vessels, i.e. pulmonary pre-acinar and intra-acinar arteries (so-called pre-capillary PH), or when pressure in the pulmonary venous system distal to the capillaries rises above a mean of 15 mmHg (so-called post-capillary PH). PH is defined by a mean pulmonary arterial pressure above 25 mmHg at rest. Vasoconstriction, remodelling and thrombosis of small pulmonary arteries lead to an increase in pulmonary vascular resistance. The consequence is failure of the afterload-intolerant right ventricle. In this review, pulmonary vascular disease in children will be addressed according to the 2003 World Health Organisation (Venice) classification of PH.     

Effects of oxygen and nitric oxide in oxygen on pulmonary arterial pressures of children with congenital cardiac defects

Inhaled nitric oxide is a specific pulmonary vasodilator. This study was undertaken to assess the effect on pulmonary arterial pressure of administering 100% oxygen compared with nitric oxide in oxygen. Thirteen mechanically ventilated children undergoing routine cardiac catheterization for the investigation of congenital heart disease were studied. Pulmonary arterial pressures were measured during inhalation of 30% oxygen (baseline), 100% oxygen, and nitric oxide (40 parts per million) in oxygen. In addition, in six children the pulmonary/systemic blood flow ratio and pulmonary vascular resistance were calculated using oxygen content, an assumed value for oxygen uptake, and the Fick principle. Results were compared using analysis of variance and the Wilcoxon signed-rank test. Pulmonary arterial pressure decreased from a mean value of 29.5 mmHg (SD 15.1) to 25.6 mmHg (SD 9.3), p= 0.048, after increasing the inspired oxygen fraction from 0.3 to 1.0. The addition of nitric oxide caused a further reduction to 22.9 mmHg (SD 7.9), p= 0.0001. There was no change in systemic arterial pressure or heart rate during the study period, but a small increase occurred in the mean methemoglobin level (1.1% to 1.3%) p= 0.039. Changes in the pulmonary/systemic blood flow ratio and pulmonary vascular resistance (n= 6) were not significant. Nitric oxide in oxygen appears to be a more potent pulmonary vasodilator than oxygen alone in pediatric patients with congenital cardiac defects.     

Core-peripheral temperature gradient in children: does it reflect clinically important changes in circulatory haemodynamics?

Following open heart surgery, changes in core and peripheral skin temperature and changes in the core-peripheral temperature gradient were measured in 10 children. These were correlated with changes in cardiac index, systemic vascular resistance index, mean arterial pressure and urinary output. During the study intervals, which lasted 1 h each, no changes in medical management were made. Using Spearman's rank correlation, only a change in central venous pressure was found to correlate with a change in the core-peripheral temperature gradient. We conclude that a change in the core-peripheral temperature will give valuable information about the patient's intravascular volume.