Low systemic blood flow and hyperkalemia in preterm infants

OBJECTIVE: Early low systemic blood flow is common in preterm infants. This study examines the relationship among low flow, renal function, and early changes in blood potassium (K(+)). METHODS: Preterm infants (n = 119) born before 30 weeks' gestational age underwent serial Doppler echocardiographic studies. Superior vena cava flow (SVC flow) was assessed as a measure of upper body systemic blood flow uncorrupted by systemic to pulmonary shunts. Serial whole blood K(+) concentrations on each arterial blood gas sample and urinary output in the first 48 hours were recorded. RESULTS: Most infants had a variable degree of rise in K(+) during the first 24 hours of life. The mean rate of rise was 0.17 mmol/L/h, the mean peak K(+) was 5.54 mmol/L, and the mean time of peak K(+) was 20 hours. The peak K(+) occurred after the lowest measured SVC flow in 84% of infants. A significant positive relationship was found between the lowest measured SVC flow and the mean (r = 0.31, P =.001) and peak (r = 0.31, P =.001) K(+) in the first 24 hours. Low SVC flow at 5 hours best predicted the rate of K(+) rise (r = 0.28, P =.002) and at 12 hours best predicted the peak K(+) concentration (r = 0.47, P <.001). The mean minimum SVC flow in the 17 babies who became hyperkalemic was 29.5 mL/kg/min versus 46.2 mL/kg/min in the 102 infants with normokalemia. Urine output in the first 24 hours was significantly lower in the hyperkalemic infants. A K(+) rate rise exceeding 0.12 mmol/L/h in the first 12 hours predicted low SVC flow with 93% accuracy. CONCLUSIONS: The data are consistent with a role for low systemic blood flow leading to reduced urinary output and subsequent hyperkalemia in preterm infants.     

Ductal shunting, high pulmonary blood flow, and pulmonary hemorrhage

OBJECTIVE: To describe the relationship among ductal shunting, estimated pulmonary blood flow, and pulmonary hemorrhage in very preterm infants. STUDY DESIGN: A total of 126 babies born before 30 weeks' gestation (median gestation 27 weeks, range 23 to 29 weeks) underwent echocardiography at 5, 12, 24, and 48 hours of age; measurements included right and left ventricular output, superior vena cava flow, and color Doppler diameter of any ductal shunt. Pulmonary blood flow was derived from the sum of right ventricular output and estimated ductal shunt flow. RESULTS: Twelve (9.5%) babies had a pulmonary hemorrhage at a mean age of 38 hours. Compared with the rest of the cohort, these 12 babies were less likely to have had antenatal steroids (59% vs 90%) and were less mature (26 weeks vs 27 weeks). At the echocardiogram closest to the pulmonary hemorrhage, 11 (92%) of the 12 babies had a significant patent ductus arteriosus >1.6 mm in diameter (median 2 mm, range 0.7 to 2.4 mm), and the median pulmonary blood flow was 326 mL/kg/min (range 210 to 598 mL/kg/min). These measurements were significantly higher than those found in the rest of the cohort in the same period (median duct diameter 0.5 mm [range 0 to 2.9 mm], median pulmonary blood flow 237 mL/kg/min [range 107 to 569 mL/kg/min]). At 5-hour echocardiography the babies with pulmonary hemorrhage had significantly larger diameter ducts but similar pulmonary blood flow. CONCLUSIONS: Pulmonary hemorrhage in preterm babies is associated with significant ductal shunting and high estimated pulmonary blood flow.     

Randomized trial of high-frequency oscillatory ventilation versus conventional ventilation: effect on systemic blood flow in very preterm infants

OBJECTIVE: Low superior vena cava (SVC) flow is common in very preterm infants in the first day and strongly associated with periventricular hemorrhage and disability. We examined the effect of high-frequency oscillatory ventilation (HFOV) compared with conventional ventilation (CV) on SVC flow and right ventricular output. METHODS: Forty-five infants <29 weeks were randomized before 1 hour of age to HFOV or CV. Echocardiography was performed on 43 infants at 3, 10, and 24 hours of age. Infants with low SVC flow (<50 mL/kg/min) or hypotension (mean blood pressure < or =20) were treated with volume and inotrope. RESULTS: Infants allocated to HFOV (n=23) and to CV (n=20) were well matched. There was a nonsignificant trend toward more infants on HFOV having SVC flow <50 mL/kg/min (48% vs 20%) and receiving volume and inotropes (61% vs 40%). There were no significant differences in mean SVC flow or right ventricular output at 3, 10, or 24 hours. Infants on HFOV had a significantly higher calculated upper body vascular resistance at 10 hours and mean blood pressure at 24 hours. CONCLUSIONS: There were no significant adverse effects of HFOV on systemic blood flow in very preterm infants during the first 24 hours of life.     

Low superior vena cava flow and intraventricular haemorrhage in preterm infants

OBJECTIVES: To document the incidence, timing, degree, and associations of systemic hypoperfusion in the preterm infant and to explore the temporal relation between low systemic blood flow and the development of intraventricular haemorrhage (IVH). STUDY DESIGN: 126 babies born before 30 weeks' gestation (mean 27 weeks, mean body weight 991 g) were studied with Doppler echocardiography and cerebral ultrasound at 5, 12, 24, and 48 hours of age. Superior vena cava (SVC) flow was assessed by Doppler echocardiography as the primary measure of systemic blood flow returning from the upper body and brain. Other measures included colour Doppler diameters of ductal and atrial shunts, as well as Doppler assessment of shunt direction and velocity, and right and left ventricular outputs. Upper body vascular resistance was calculated from mean blood pressure and SVC flow. RESULTS: SVC flow below the range recorded in well preterm babies was common in the first 24 hours (48 (38%) babies), becoming significantly less common by 48 hours (6 (5%) babies). These low flows were significantly associated with lower gestation, higher upper body vascular resistance, larger diameter ductal shunts, and higher mean airway pressure. Babies whose mothers had received antihypertensives had significantly higher SVC flow during the first 24 hours. Early IVH was already present in 9 babies at 5 hours of age. Normal SVC flows were seen in these babies except in 3 with IVH, which later extended, who all had SVC flow below the normal range at 5 and/or 12 hours. Eight of these 9 babies were delivered vaginally. Late IVH developed in 18 babies. 13 of 14 babies with grade 2 to 4 IVH had SVC flow below the normal range before development of an IVH. Two of 4 babies with grade 1 IVH also had SVC flow below the normal range before developing IVH, and the other 2 had SVC flow in the low normal range. In all, IVH was first seen after the SVC flow had improved, and the grade of IVH related significantly to the severity and duration of low SVC flow. The 9 babies who had SVC flow below the normal range and did not develop IVH or periventricular leucomalacia were considerably more mature (median gestation 28 v 25 weeks). CONCLUSIONS: Low SVC flow may result from an immature myocardium struggling to adapt to increased extrauterine vascular resistances. Critically low flow occurs when this is compounded by high mean airway pressure and large ductal shunts out of the systemic circulation. Late IVH is strongly associated with these low flow states and occurs as perfusion improves.     

Pilot study of milrinone for low systemic blood flow in very preterm infants

OBJECTIVES: To examine the hemodynamic effects of milrinone given prophylactically to very preterm infants at high risk of low superior vena cava (SVC) flow and to investigate the preliminary efficacy and safety of an optimal dose. STUDY DESIGN: This was a prospective, open-label study in two stages. The first involved dose escalation in two cohorts. Milrinone infusions of 0.25 microg/kg per minute (n = 8) and then 0.5 microg/kg per minute (n = 11) were administered from 3 to 24 hours of age. Population pharmacokinetic modeling was used to develop an optimized dose regimen. Ten infants then were loaded with 0.75 microg/kg per minute for 3 hours, followed by 0.2 microg/kg per minute maintenance until 18 hours of age. Infants were monitored for blood pressure, serial echocardiograms, and blood milrinone levels. The primary outcome was maintenance of SVC flow greater than 45 mL/kg per minute through the first 24 hours. RESULTS: Low SVC flow developed in 36% of babies at both 0.25 microg/kg per minute and 0.5 microg/kg per minute of milrinone. Blood levels on these two regimens were slow to reach the target range and accumulated above this range by 24 hours. At 0.75 to 0.2 microg/kg per minute, no infant had SVC flow below 45 mL/kg per minute, compared with 61% in historic control subjects. Four infants needed an additional inotrope to support blood pressure. Blood levels were within the target range in 9 of 10 babies. CONCLUSIONS: We used population pharmacokinetic modeling to develop an optimal dosing regimen for milrinone. The efficacy and safety in this novel preventative approach to circulatory support is encouraging but inconclusive. We do not recommend the use of milrinone in preterm infants outside a research setting.     

Blood flow in the common carotid artery in term and preterm infants: reproducibility and relation to cardiac output

AIM: To assess the reproducibility of, and determine normative data for, flow volume measurements from the right common carotid artery (CCA) and its relation to left ventricular output (LVO) in stable term and preterm babies using Doppler ultrasound. METHODS: Right CCA flow volume was measured using a near focus, high frequency transducer by obtaining intensity weighted mean velocity and right CCA diameter. LVO was determined using standard Doppler techniques. Reproducibility studies were performed on 30 newborn infants by two observers. Normative data were obtained from 40 spontaneously breathing preterm babies and 21 term babies. RESULTS: The intraobserver coefficient of variation for CCA flow measurements was 10.5% for observer 1 and 15.4% for observer 2, whereas the interobserver coefficient of variation was 16.4%. In term and preterm infants, right CCA flow was about 20 ml/kg/min, accounting for 11% of cardiac output. Among the preterm infants, there was a positive correlation of right CCA flow with gestation (r = 0.61, p<0.001), weight (r = 0.64, p<0.001), and LVO (r = 0.59, p<0.001). Right CCA diameter also increased with weight (r = 0.63, p<0.001) and gestation (r = 0.58, p<0.001). The proportion of LVO distributed to the right CCA did not increase with gestation, nor did the right CCA flow per kg body weight. CONCLUSIONS: It is possible to perform reproducible measurements of flow volume in the CCA of newborn infants. In stable, spontaneously breathing babies, both cardiac output and carotid flow increased with gestation and body weight. The proportion of cardiac output distributed to the right CCA remained relatively constant across gestation.     

Randomized trial of dobutamine versus dopamine in preterm infants with low systemic blood flow

OBJECTIVE: Our purpose was to determine if dobutamine or dopamine results in greater improvements in systemic blood flow in very preterm infants with low flow during the first 24 hours of life. STUDY DESIGN: A 2-center, randomized, double-blind study. Infants (n = 42) with low superior vena cava (SVC) flow (<41 mL/kg/min) in the first 12 hours were randomly assigned to receive 10 mL/kg normal saline solution, followed by 10 microg/kg/minute of dobutamine or dopamine. If low flow persisted or recurred, the inotrope was increased to 20 microg/kg/minute, with crossover to the other inotrope if treatment failed to maintain flow. RESULTS: Volume produced a more significant increase in SVC flow than dopamine (+43%). At the highest dose, dobutamine resulted in a significantly greater increase in SVC flow than dopamine (mean, +9.9 vs -3.2 mL/kg/min, P =.02). Dopamine resulted in a significantly greater increase in blood pressure. Infants receiving dobutamine only at 24 hours had a greater right ventricular output than infants receiving dopamine (mean, 295 vs 167 mL/kg/min, P <.001). Forty percent failed to increase or maintain SVC flow in response to either inotrope. No significant differences in mortality or morbidity were found. CONCLUSIONS: Dobutamine produced a greater increase in blood flow than dopamine.     

The diagnostic value of a single measurement of superior vena cava flow in the first 24?h of life in very preterm infants

Low superior vena cava (SVC) flow has been associated with intraventricular haemorrhage (IVH) in very preterm infants. We studied the diagnostic value of a single measurement of SVC flow within the first 24?h of life in very preterm infants and its association with occurrence or extension of IVH in a setting of limited availability of neonatal echocardiography. Preterm infants who were born at less than 30?weeks gestation and who had an echocardiogram within 24?h after birth were eligible. Baseline, clinical and ultrasound data were collected. A total of 165 preterm infants were included. Low SVC flow (<41?ml/kg/min) occurred in six infants and was associated with severe IVH and extension of IVH, although this was not significant after adjusting for confounders. The only independently associated variable with low SVC flow was admission temperature (odds ratio 0.27, p?=?0.001). A review of SVC flow values shows that these are higher now than initially reported. This study does not show an association of low SVC flow and severe IVH or extension of IVH after adjusting for confounders as a single measurement of SVC flow did not add any diagnostic value in this cohort. Thus, the exact role of SVC flow measurements in the circulatory assessment of preterm infants remains to be elucidated. However, admission temperature may have an effect on systemic blood flow in very preterm infants.     

Effective pulmonary blood flow in preterm and light-for-date infants.

Using a method employing low concentrations (3%) of nitrous oxide, we measured effective pulmonary capillary blood flow (Qpc eff) in 23 preterm infants, 26 light-for-date infants, and 15 infants who were both preterm and light-for-date. All infants studied had no clinical or laboratory evidence of idiopathic respiratory distress syndrome (IRDS) and were studied before the age of 48 hours. The mean Qpc eff of 175 ml/kg/min in preterm infants (a group at high risk of developing IRDS), although significantly less than the mean of 214 ml/kg/min found in light-for-date infants (a group with a low risk of developing IRDS), was similar to that reported in normal term infants. The mean result for preterm, light-for-date infants was 189 ml/kg/min. No evidence was found that preterm infants were predisposed to IRDS as a consequence of preexisting pulmonary hypoperfusion.     

Low superior vena cava flow and neurodevelopment at 3 years in very preterm infants

OBJECTIVES: Low superior vena cava (SVC) flow is common in the first hours after very preterm birth and has a strong association with subsequent periventricular/intraventricular hemorrhage. We report the neurodevelopmental outcome at 3 years of age of very preterm babies who had serial echocardiographic studies, including measures of SVC flow, during the first 48 hours after birth. STUDY DESIGN: A prospective observational study was performed on a cohort of 126 babies (<30 weeks), 103 of whom survived to discharge. Neurodevelopmental follow-up data, which included abnormal developmental quotient, abnormal motor score, and cerebral palsy, were available for 93% of this cohort at 3 years of age. Relations between 3-year outcome and early hemodynamic measures and clinical parameters were explored. RESULTS: After controlling for confounding variables, average SVC flow over the first 24 hours of life was significantly associated with the primary outcome of death or survival with any disability (P=.004) and with the secondary outcome of abnormal developmental quotient (P = .006). A greater number of low SVC flow readings during the first 24 hours was significantly related to death and adverse developmental outcome, but the individual lowest SVC flow was not, suggesting the importance of duration of low SVC flow. After adjustment, there was no significant association between average mean blood pressure over the first 24 hours and abnormal developmental outcome, whereas the proportion of mean blood pressure readings less than the gestational age showed a trend toward an association with death and any disability. CONCLUSIONS: Low early postnatal blood flow to the upper body and brain may be one factor in the causal pathway of impaired preterm neurodevelopmental outcome.     

Effect of early targeted indomethacin on the ductus arteriosus and blood flow to the upper body and brain in the preterm infant

OBJECTIVE: To determine if indomethacin given to preterm infants with a large ductus arteriosus (DA) in the first hours of life results in maintained or improved brain and upper body blood (superior vena cava (SVC)) flow. STUDY DESIGN: A randomised, double blind trial of indomethacin v placebo. Echocardiography was performed on 111 infants born at < 30 weeks gestation at 3 and/or 10 hours after birth. Infants were eligible if the DA diameter was > 1.6 mm. Infants were randomised to receive indomethacin 0.2 mg/kg or placebo. Crossover occurred if the DA was still > 1.6 mm. Echocardiography was performed one hour after each treatment. RESULTS: Seventy (63%) infants had a DA > 1.6 mm, with 35 randomised to receive indomethacin and 35 to receive placebo. At one hour there was no difference in DA constriction (indomethacin -20% v placebo -15%), change in SVC flow (-1% v -9%), for right ventricular output (RVO). Two hours after indomethacin, 62 infants had uncontrolled observations, at which time significant ductal constriction had occurred. At this time, infants of > or = 27 weeks gestation had significantly greater increases in SVC flow and RVO than infants of < 27 weeks gestation. Infants with failed ductal constriction had significantly lower initial SVC flow and developed more late grade 3/4 peri/intraventricular haemorrhage (P/IVH). Initial SVC flow, but not ductal constriction, was a significant predictor of late grade 3/4 P/IVH in adjusted analysis. CONCLUSIONS: Indomethacin had minimal effect on ductal constriction and blood flow at one hour compared with placebo. Failure of ductal constriction is associated with low SVC flow and subsequent late severe P/IVH.     

Which to measure,systemic or organ blood flow? Middle cerebral artery and superior vena cava flow in very preterm infants

AIM: To describe, in very preterm babies, postnatal changes in measures of middle cerebral artery (MCA) Doppler variables. To relate these peripheral measures to echocardiographic measures of systemic blood flow and ductal shunting, and to study their relation to subsequent intraventricular haemorrhage (IVH). METHODS: 126 babies born before 30 weeks were studied with serial echocardiography and cerebral and Doppler ultrasound of the MCA at 5, 12, 24, and 48 hours of age. Echocardiographic measures included superior vena cava (SVC) flow and colour Doppler diameter of the ductal shunt. MCA Doppler measures included mean velocity, pulsatility index (PI), and estimated colour Doppler diameter. RESULTS: MCA mean velocity increased whereas the PI decreased significantly over the first 48 hours. Babies with low SVC flow had significantly lower MCA mean velocity and estimated diameter than babies with normal SVC flow. There was no difference in PI. On multivariant analysis, the significant associations with MCA mean velocity were mean blood pressure (MBP), heart rate, SVC flow, and lower calculated vascular resistance. The significant associations with PI were larger ductal diameter and lower mean MBP. The significant associations with MCA diameter were higher SVC flow and lower calculated vascular resistance. After controlling for gestation, there was a highly significant association between lowest SVC flow and subsequent IVH but no association between IVH and lowest MCA mean velocity, estimated diameter, PI, or MBP. CONCLUSIONS: These data are consistent with the speculation that SVC flow is a reflection of cerebral blood flow. Low SVC flow is more strongly associated with subsequent IVH than cerebral artery Doppler measures or MBP.     

Clinical detection of low upper body blood flow in very premature infants using blood pressure, capillary refill time, and central-peripheral temperature difference

OBJECTIVE: To determine the accuracy of blood pressure (BP), capillary refill time (CRT), and central-peripheral temperature difference (CPTd) for detecting low upper body blood flow in the first day after birth. METHODS: A prospective, two centre cohort study of 128 infants born at < 30 weeks gestation. Invasive BP (n = 108), CRT (n = 128), and CPTd (n = 46) were performed immediately before echocardiographic measurement of superior vena cava (SVC) flow at three, 5-10, and 24 hours after birth. RESULTS: Forty four (34%) infants had low SVC flow (< 41 ml/kg/min) in the first day, 13/122 (11%) at three hours, 39/126 (31%) at 5-10 hours, and 4/119 (3%) at 24 hours. CPTd did not detect infants with low flows. Combining all observations in the first 24 hours, CRT > or = 3 seconds had 55% sensitivity and 81% specificity, mean BP < 30 mm Hg had 59% sensitivity and 77% specificity, and systolic BP < 40 mm Hg had 76% sensitivity and 68% specificity for detecting low SVC flow. Combining a mean BP < 30 mm Hg and/or central CRT > or = 3 seconds increases the sensitivity to 78%. CONCLUSIONS: Low upper body blood flow is common in the first day after birth and strongly associated with peri/intraventricular haemorrhage. BP and CRT are imperfect bedside tests for detecting low blood flow in the first day after birth.     

Cerebral tissue oxygenation index,cardiac output and superior vena cava flow in infants with birth weight less than 1250 grams in the first 48 hours of life

Background

Near-infrared spectroscopy is a non-invasive method of assessing cerebral oxygenation. Functional echocardiography is increasingly used by neonatologists in the assessment of cardiovascular function.

Aims

To correlate cerebral tissue oxygenation index (cTOI) and cardiac output in infants less than 1250 g at 6, 12, 24 and 48 hours of age.

Study design

A prospective observational study.

Subjects

Newborns with birth weight < 1250 g.

Outcome measures

Serial assessments of superior vena cava (SVC) flow, right and left ventricular outputs, ductus arteriosus and cTOI were performed at 6, 12, 24 and 48 hours of age. Clinical parameters, including mean blood pressure, mean airway pressure, blood gas parameters and oxygen saturations were recorded.

Results

22 neonates were enrolled following parental consent. The mean birth weight was 851 g (SD ± 201), mean gestational age was 25.9 weeks (SD ± 1.7). Mean SVC flow at 6 hours of age was 56.8 ml/kg/min and increased to 68.6 ml/kg/min at 48 hours of age. 9 infants (41%) had at least one measurement of low SVC flow (< 41 ml/kg/min) in the first 48 hours. Mean cTOI was 65.2% at 6 hours of age, 63.9% at 12 hours of age, 68.8% at 24 hours of age and 67.2% at 48 hours of age. Cerebral fractional tissue oxygen extraction values were highest at 12 hours (0.31 ± 0.09). There was no correlation between SVC flow and cTOI values.

Conclusion

SVC flow, left and right ventricular output increased during first 48 hours of life. cTOI decreased at 12 hours of age with a concomitant increase in fractionated oxygen extraction. These changes reflect transitional changes in both cardiac and cerebral hemodynamics in extremely low gestational age newborns during the first 48 hours.     

Correlation between echocardiographic superior vena cava flow and short-term outcome in infants with asphyxia

Objectives

To assess the relationship between superior vena cava (SVC) flow and short-term outcome in infants with perinatal asphyxia.

Methods

Infants in sequence born after more than 35 weeks of gestation who had been hospitalized at the NICU and normal neonatal wards of Wakayama Medical University between May 2005 and September 2010 were recruited for this observational cohort study. The study eligibility criterion was the presence of perinatal asphyxia, as evidenced by abnormal fetal heart rate monitoring and an Apgar score of 7 or less at 1 min or need for resuscitation using positive pressure ventilation. SVC flow was measured in the first three days of life by Doppler echocardiography as described by Kluckow and Evans. Short-term outcome was defined as poor if MRI demonstrated bilateral lesions of the basal ganglia and thalamus and/or multicystic encephalomalacia due to hypoxic ischemia.

Results

In the head cooling group, SVC flow in infants with a good outcome was lower than that in infants with a poor outcome at 12 h (36.9 ± 7.7 vs 113.4 ± 42.4 ml/kg/min (p = 0.01)), 24 h (75.2 ± 25.3 vs 155.6 ± 45.7 ml/kg/min (p = 0.03)), and 48 h (92.5 ± 34.2 vs 161.1 ± 46.7 ml/kg/min (p = 0.04)) after birth. SVC flow decreased promptly after introduction of head cooling in infants who had a good outcome, whereas it increased gradually after head cooling in those who had a poor outcome.

Conclusion

We speculate that regulation of brain circulation is disrupted in infants with asphyxia who show a poor outcome.     

Ductus arteriosus blood flow during first 48 hours of life.

A volumetric Doppler technique was used to measure net ductus arteriosus shunt during the first 48 hours of life in 30 infants of less than 33 weeks'' gestation, and in 10 full term infants. In the full term infants a left to right shunt of 62 ml/kg/minute (95% confidence limits 43-82) shortly after birth decreased rapidly over the first 12 hours and was not measurable by 48 hours. The preterm infants had smaller left to right shunts shortly after birth--49 ml/kg/minute (95% confidence limits 38-59). There was no obvious subsequent change in the mean shunt, although by 48 hours there was greater variation in the size of the shunt. The respiratory distress syndrome did not affect the size of the ductal shunt, but the shorter the gestation period the larger the shunt by 48 hours. A ductal flow of greater than 70 ml/kg/minute at 48 hours of age predicted the subsequent development of a ductal murmur with 75% sensitivity and 100% specificity.     

Severity of the ductal shunt: a comparison of different markers

BACKGROUND: When the ductus arteriosus (DA) is patent, the ductal shunt is proportional to the ratio of left ventricular output (LVO) to systemic blood flow. Systemic blood flow can be estimated by measuring flow in the superior vena cava (SVC). OBJECTIVE: To re-evaluate the accuracy of standard echocardiographic markers of patent ductus arteriosus (PDA) using LVO/SVC flow ratio. METHODS: Prospective study. Preterm infants of 24-30 weeks gestational age and postnatal age less than 48 hours. The following echocardiographic criteria were measured: left atrial to aortic root ratio (LA/Ao); DA diameter by B mode and colour Doppler; mean and end diastolic flow velocity of the left pulmonary artery (LPA); LVO; SVC flow. RESULTS: Twenty three preterm infants were enrolled (median gestational age 28 weeks (range 24-30), median birth weight 840 g (500-1440)). The DA was closed in eight (mean (SD) LVO/SVC 2.4 (0.3)) and open in 15 (mean (SD) LVO/SVC 4.5 (0.6)). An LA/Ao ratio > or =1.4, a DA diameter > or =1.4 mm/kg, and a mean and end diastolic flow velocity of LPA respectively > or =0.42 and > or =0.20 m/s identified an LVO/SVC > or =4 with a sensitivity and a specificity above 90%. CONCLUSION: This study indicates that LA/Ao ratio, DA diameter, and mean and end diastolic flow velocity of the LPA are accurate markers of PDA. These standard echocardiographic variables are easy to measure and need less skill and resources than direct measurements of ductal shunt.     

Cerebral blood flow and left ventricular output in spontaneously breathing, newborn preterm infants treated with caffeine or aminophylline

Aminophylline and caffeine are commonly used for prophylaxis of apnea in premature infants. Previous studies have indicated different effects of the drugs on cerebral circulation. Therefore, we have compared the acute effects of bolus administration of caffeine citrate or aminophylline on left ventricular output, heart rate, blood pressure and global cerebral blood flow. The study group consisted of 33 newborn, spontaneously breathing, preterm infants randomly assigned to receive either aminophylline 5mg/kg (n = 19) or caffeine citrate 20mg/kg ( n = 14). Two hours after iv drug administration, global cerebral blood flow measured by the Xe-clearance technique was significantly lower after aminophylline than after caffeine (mean(SD)): 13.2 (+2.9/ - 2.3) versus 17.2 (+7.1/ - 5.1) ml/100 g/min) (p = 0.01). There were no other statistically significant differences in circulatory or ventilatory parameters between the groups. Further studies are needed to clarify the clinical relevance of these results.     

Left ventricular contractility in extremely premature infants in the first day and response to inotropes

The aim was to assess myocardial contractility in infants born <30 wk gestation developing low systemic blood flow (SBF) in the first day, and the effect of dobutamine versus dopamine. Superior vena cava (SVC) flow was used as a measure of SBF at 3, 10, and 24 h (n = 106). Infants with low SVC flow randomized to dopamine or dobutamine. Myocardial contractility was determined by the relationship between left ventricular (LV) mean velocity of circumferential fiber shortening (mVcfs) and wall stress. Infants who developed low SVC flow had significantly worse myocardial contractility at 3 h, but not 10 h. At 24 h, low-flow infants had lower than expected mVcfs for any given LV stress. In 37 infants randomized to inotrope, there was no significant difference in contractility at 10 microg/kg/min. At 20 microg/kg/min (n = 21), dopamine increased whereas dobutamine decreased LV stress. Infants on dobutamine had significantly lower than expected mVcfs for any given LV stress compared with infants on dopamine. Contractility was not improved by either inotrope at either dose. In conclusion, infants developing low SVC flow in the first day have worse myocardial contractility at 3 h. Neither inotrope increased contractility, but dopamine increased LV stress at 20 microg/kg/min.     

Crying vital capacity. Measurement of neonatal lung function.

Serial measurements of crying vital capacity (CVC), expressed as ml/cm chest circumference, were made by reverse plethysmography during the first 2 weeks of life. Clinically normal babies born at term by elective caesarean section had a smaller mean CVC in the first 2 weeks of life compared with clinically normal term babies born vaginally. In contrast, no significant difference was shown between the mean CVC in term babies born vaginally and those born by urgent caesarean section. Clinically normal term babies born by caesarean section (elective and urgent) had a smaller mean percentage rise of CVC in the first 24 hours of life and a significant delayed rise of CVC from 24-48 hours compared with those born vaginally. Clinically normal preterm babies born vaginally had a smaller mean CVC in the first 2 weeks of life compared with term babies born vaginally, and were characterized by a significant rise of CVC from 5-10 days. Babies with hyaline membrane disease (HMD) had a smaller CVC in the first 2 weeks of life compared with clinically normal preterm babies. Babies of various gestational ages with transient tachypnoea (TT) had a smaller mean CVC in the first 2 weeks of life compared with clinically normal term babies, but a similar mean CVC in the first 72 hours of life compared with clinically normal preterm babies. At each postnatal age the mean CVC of babies with HMD was less than the corresponding mean in babies with TT. All babies with TT had a rise in CVC from 24-48 hours, whereas CVC fell in all babies with HMD except one during this period. CVC is a simple, safe, rapid, and noninvasive test of neonatal lung function, and is a valuable aid to other methods of assessing pulmonary function in the neonate with respiratory distress.