Haematocrit and red blood cell transport in preterm infants: an observational study

AIMS: To test whether cardiac output acts as a compensatory response to changes in haematocrit. METHODS: A cohort of 38 preterm infants (27-31 weeks' gestation) was studied with repeated Doppler measurements of left ventricular output during the 1st month of life. Red blood cell transport was calculated when the duct was closed. RESULTS: Multiple regression analysis showed that left ventricular output correlated negatively with haematocrit when the duct was closed (n = 84) and when it was open (n = 59). The influence of an increase of 10% in haematocrit absolute value on mean (SD) left ventricular output was estimated at -55 (11) ml/kg/min. Mean (SD) red blood cell transport was 132 (30) ml/kg/min with a mean (SD) intra-individual variability of 20% (8.8%). Red blood cell transport was increased more frequently by left ventricular output than by haematocrit. Haematocrit and left ventricular output but not red blood cell transport were dependent on postnatal age. CONCLUSION: These results suggest that in preterm infants cardiac output adaptation is effective in attenuating the effects of red blood cell mass variations on systemic oxygen carrying capacity.     

Impact of delivery mode and gestational age on haematological parameters in Taiwanese preterm infants

Aim:   Reference ranges of haematological parameters in preterm infants are limited. The aim of this study is to determine the reference values of haematological parameters in preterm infants in Taiwan, and to assess the impact of gestational age and mode of delivery on these parameters.
Method:   Medical records were retrospectively reviewed in preterm infants admitted to National Taiwan University Hospital from January 2001 to December 2004. The inclusion criteria included infants with <37 weeks of gestation who had blood sampling within 24 h of birth. The exclusion criteria included those with maternal history of antepartum haemorrhage, chorioamnionitis, fever, sepsis, preeclampsia and hypertension; and perinatal history of twin-to-twin transfusion syndrome, feto-maternal transfusion, injury and infection.
Results:   Of 568 preterm infants with blood cell counts, 337 were available for analysis. There were trends of increase in red blood cell counts, haemoglobin levels and haematocrit values as gestation increased up to 34 weeks. In contrast, a trend of decrease was noted in mean corpuscular volume values. There was an initial trend of decrease in white blood cell counts and then increased after 31 weeks gestation. The platelet counts were essentially unchanged. Infants born by vaginal delivery generally had higher haematological parameters than those born by Caesarean section at different gestational ages except for mean corpuscular volume values.
Conclusions:   We established the reference ranges of haematological parameters in Taiwanese preterm infants. Health-care professionals must be cautious in clinical application of the haematological values because of varying antenatal and perinatal risk factors.     

Effects of partial plasma exchange transfusion on blood flow velocity in large arteries of arm and leg, and in cerebral arteries in polycythaemic newborn infants

Continuous wave Doppler velocimetry was performed in brachial, femoral and cerebral arteries in four preterm, four small-for-gestational-age (SGA) and eight appropriate-for-gestational age (AGA) polycythaemic newborns before and at 3 and 24 h after partial plasma exchange transfusion and in 18 matched controls at 3 and 24 h after birth. In peripheral arteries, end-diastolic flow velocity was zero in all eight AGA controls, but only in two of the other infants. Consequently, mean flow velocity and red cell transport in AGA controls were significantly lower than in the other five groups, which did not differ. Partial plasma exchange transfusion did not influence flow velocities and red cell transport in peripheral arteries, but normalized the flow velocities in cerebral arteries in all three subgroups of polycythaemic infants, which were lower than in control infants. Cerebral red cell transport in controls increased significantly between 3 and 24 h, and in polycythaemic infants between 0 and 3 h after partial plasma exchange transfusion. In conclusion, reduction in haematocrit had different effects on blood flow velocity and red cell transport of peripheral and cerebral vessels, suggestirng that the increased cerebral blood flow velocity after partial plasma exchange transfusign is not simply due to a reduction in viscosity or oxygen content of the blood. The lower peripheral blood flow velocities in normocythaemic AGA infants as compared to all other groups, suggest that the level of maturity is an important determinant for the capacity to regulate blood flow.     

Effect of hemoglobin on transfusion and neonatal adaptation in extremely low-birthweight infants

Background: The aim of the present paper was to investigate the effect of initial hemoglobin level on red blood cell transfusion and neonatal adaptation in extremely low-birthweight (ELBW) infants.
Methods: Subjects consisted of 54 ELBW infants admitted to level III neonatal intensive care unit between 1995 and 2000, and divided into two groups based on hemoglobin level at birth. High hemoglobin was defined as hemoglobin ≥15.0 g/dL.
Results: There were no significant differences in gestational age and birthweight between the high hemoglobin group ( n  = 28) and low hemoglobin group ( n  = 26). The high hemoglobin group had decreased probability of requiring red blood cell transfusion ( P  < 0.05) and number of red blood cell transfusions ( P  < 0.05). Mortality rate in the low hemoglobin group was significantly higher compared with the high hemoglobin group ( P  = 0.03). In the high hemoglobin group, blood pressures during the first 24 h were significantly higher ( P  < 0.05) and the risk of intraventricular hemorrhage was significantly lower ( P  = 0.04) compared with the low hemoglobin group. The predictive variables, initial hemoglobin level (odds ratio 1.93 [decrease by 1 g/dL]) and intraventricular hemorrhage ≥III (odds ratio 21.76 [positive]) were found to be most predictive for death on logistic regression.
Conclusion: High hemoglobin level at birth is associated with a significantly reduced requirement for red blood cell transfusion and might contribute to stabilization of blood pressure, and thus reduce mortality and the risk of severe intraventricular hemorrhage.     

红细胞持续输注3小时和4小时改善贫血早产儿脑组织氧合的非随机对照试验

目的：探讨红细胞持续输注（本文简称输血）3 h和4 h对贫血早产儿脑、肠、肾组织氧合的影响。 方法：以在复旦大学附属儿科医院（我院）新生儿科住院、胎龄<37周、符合早产儿输血指征的早产儿为研究对象,以我院新生儿科二和三病区分别为输血3 h和4 h组,设定输血3 h和4 h后可接受的CrSO2变化差值为4%;主要结局指标：输血后12~24 h时间段的脑组织氧饱和度（CrSO2 );次要结局指标：输血前2 h、输血过程中和之后2、~4、~6、~12 h时间段的脑组织氧饱和度（CrSO2 ),输血前2 h、输血过程中和之后2、~4、~6、~12和~24 h时间段肠组织氧饱和度（SrSO2）和肾组织氧饱和度（RrSO2）,输血前2 h、输血过程中和之后2 h每搏输出量（SV）、心输出量（CO）、心率（HR）、经皮动脉氧饱和度（TcSaO2）和平均动脉血压（MABP）。采用非劣效检验分析两组患儿组织氧饱和度、心功能指标和基本生命体征参数输血前后差值的差异性。 结果：①符合本文纳入、排除和剔除标准的患儿共52例。输血3 h和4 h组分别为21和31例,输血时矫正胎龄分别为（38.6±4.3）和（36.4±3.1）周（P=0.033）。②输血3 h组输血前后CrSO2、SrSO2和RrSO2分别为（0.573±0.025） vs （0.600±0.017）、（0.530±0.038） vs （0.561±0.032）、（0.564±0.035） vs （0.595±0.037）,输血4 h组输血前后CrSO2、SrSO2和RrSO2分别为（0.573±0.045） vs （0.596±0.033）、（0.543±0.052） vs （0.552±0.052）、（0.533±0.063） vs （0.576±0.050）;两组患儿组内比较,输血前后CrSO2、SrSO2和RrSO2差异均有统计学意义（P均<0.05）;组间比较,CrSO2、SrSO2和RrSO2输血前后差值差异均无统计学意义,非劣效检验成立。③两组患儿组内比较,输血前后HR和MABP差异均有统计学意义（P均<0.05）。 结论对于输血时矫正胎龄大于38周的早产儿组织氧合影响输血3 h不劣于常规的输血4 h。     

Haemodynamic effects of erythrocyte transfusion in preterm infants

The aim of the study was to assess the short-term cardiorespiratory effects of a standard red cell transfusion in very low birth weight (<1500 g) infants undergoing intensive care. A total of 37 infants (birth weight 920±230 g, gestational age 27.8±2.1 weeks, age at study 6.1±3.9 days) with indwelling arterial lines were studied when 10 ml/kg of packed donor red cells were transfused based on clinical judgment. Infants with patent ductus arteriosus and/or inotropic treatment were excluded from the study. Oxygen saturation, left ventricular output, stroke volume, systolic, diastolic and mean arterial pressure, heart rate, and capillary refill time were assessed immediately prior to the transfusion and within an hour after the transfusion was completed. Capillary refill time after the transfusion was significantly shorter than prior to the transfusion (2.1±0.9 versus 2.4±1.0 s, P =0.033). Left ventricular output, stroke volume and arterial pressures remained unaltered. Oxygen saturation after the transfusion was lower than before the transfusion (94.0±3.8 versus 95.3±2.5%, P =0.014) despite unaltered oxygen supply. Conclusion: the data suggest that although a red cell transfusion of 10 ml/kg may marginally improve peripheral perfusion, it does not influence cardiac output and arterial blood pressure in normotensive preterm infants. It may, however, cause a transient decrease in oxygen saturation.Abbreviations CRT capillary refill time - HR heart rate - LVO left ventricular output - PDA patent ductus arteriosus - SV stroke volume     

Effects of red cell transfusion on cardiac output and perfusion index in preterm infants

Objective/Aim

The present investigation was designed to study the effect of blood transfusion on cardiac output and perfusion index. The aim was to demonstrate a relationship between hematocrit, lactate, cardiac output and perfusion index in anemic preterm infants and to investigate significant changes in these parameters induced by RBC transfusion.

Methods

Anemic infants who were under 35 weeks of gestational age (GA) and were in a stable clinical condition without respiratory or cardiac problems, signs of sepsis, or renal disease at the time of investigation were enrolled in the study. Enrolled infants received 15 ml/kg pure red blood cells over 4 h. Hematocrit and lactate levels were studied before and after transfusion. Cardiac output was measured by an ultrasound device (USCOM 1A) and perfusion index was monitored by pulse oximeter (MasimoRad7).

Results

Cardiac output decreased by 9% (p < 0.05), due to decrease in heart rate by 10% (p < 0.05) and stroke volume significantly by 5% (p < 0.05) both in left and right sided cardiac measurements. Perfusion index significantly increased and lactate levels significantly decreased after transfusion (p < 0.05). Htc was inversely correlated with lactate levels, HR, CI and CO (r = − 0.33, p = 0.01; r = − 0.53, p = 0; r = − 0.37, p = 0.004, r = − 0.28, p = 0.03). PI was not significantly correlated with Htc levels before and after transfusion (r = 0.07, p = 0.7 and r = 0.007, p = 0.97).

Conclusion

Our data support that heart rate, CO and CI and lactate levels increased as a response to anemia in preterm infants and RBC transfusion improved perfusion index suggesting better tissue oxygenation.     

Cardiac output and blood volume parameters using femoral arterial thermodilution

Background:  The pulse-induced continuous cardiac output (PiCCO) system is a less invasive method than pulmonary thermodilution for the measurement of cardiac output and estimating blood volume parameters. The normal values in children have not been defined. The purpose of the present paper was therefore to evaluate cardiac output and parameters of blood volume using femoral arterial thermodilution in critically ill children.
Methods:  A prospective study was performed in 17 critically ill children aged between 2 months and 14 years. Two measurements were taken for each determination of cardiac output, global end diastolic volume (GEDVI), intrathoracic blood volume index (ITBI), extravascular lung water index (ELWI), systolic volume index (SVI), stroke volume variation (SVV), cardiac function index (CFI), left ventricular contractility (dp/dt max), and the systemic vascular resistance index (SVRI).
Results:  One hundred and seventeen measurements were performed. The mean cardiac index (CI) was 3.5 ± 1.3 L/min per m². The GEDVI (399.7 ± 349.1 mL/m²), ITBI (574.5 ± 212.2 mL/m²) and dp/dt max (804.6 ± 372.1 mmHg/s) were lower than reported in adults, whereas ELWI (18.9 ± 9.3 mL/m2) and CFI (8 ± 2.5 L/min) where higher. The GEDVI, SVI, dp/dt max and CI increased with the weight of the patients whereas the ELWI values decreased.
Conclusions:  Femoral arterial thermodilution is a suitable technique for the measurement of cardiac output in critically ill children. The intrathoracic and intracardiac volumes are lower than in adults, whereas extrapulmonary water is higher; these values are related to the weight of the patient.     

Cardiac outcomes of hydrops as a result of twin–twin transfusion syndrome treated with laser surgery

Aim:   To determine cardiac outcomes of foetal hydrops as a result of twin–twin transfusion syndrome treated with laser surgery.
Methods:   Hydrops identified in 16 recipient foetuses with twin–twin transfusion syndrome was treated with laser ablation surgery to anastomotic vessels. Prior to laser surgery, the foetuses were assessed by echocardiography for cardiac abnormalities and ventricular and valvular dysfunction. After delivery, echocardiography was performed on 15 of the 16 newborn infants.
Results:   Foetal echocardiography indicated impaired biventricular function in the 16 hydropic foetuses. Five foetuses had little or no forward flow through the pulmonary valve, while four had pulmonary regurgitation. Following laser surgery performed at a mean of 22.9 weeks gestation, hydrops resolved in all cases. Delivery occurred at a mean of 33.6 weeks gestation. Post-natal echocardiography revealed cardiac abnormalities in five neonates, of whom three had right ventricular outflow tract obstruction. One preterm infant with severe pulmonary stenosis died with intractable cardiac failure.
Conclusion:   The majority of hydropic infants with twin–win transfusion syndrome have normal cardiac outcomes following intrauterine laser surgery. As up to one-third may have cardiac abnormalities, cardiological monitoring is recommended during the first year of life.     

输血对贫血早产儿生命体征及心脏功能的影响

目的 探讨输血对贫血早产儿生命体征及心脏功能的影响。方法 采用前瞻性队列研究方法,以胎龄<34 周、出生1 周后接受输血治疗的40 例贫血早产儿为研究对象。运用便携式超声诊断仪测定输血前与输血结束后24 h 内左心室射血分数、短轴缩短率、每搏输出量、心输出量。输血前后各24 h 内记录患儿有无呼吸暂停及呼吸暂停次数;输血前及输血结束时,在患儿安静时监测一次体温、血压,同时输血前后各4 h 内每小时记录一次患儿安静时的心率、呼吸频率、经皮氧饱和度等。结果 与输血前比较,输血后4 h 内患儿心率、呼吸频率均明显下降(P<0.05)。4 例患儿输血前24 h 内有呼吸暂停,输血后24 h 内未再出现呼吸暂停。输血后收缩压、舒张压、平均动脉压、体温较前均无显著变化(P>0.05);输血后左心室射血分数、每搏输出量、心输出量、短轴缩短率较前均无显著变化(P>0.05)。结论 输血可以改善贫血早产儿的临床症状,而且对心脏功能无显著影响。     

Effects of red cell transfusion on pulmonary blood flow and right ventricular systolic time intervals in neonates

Blood transfusion increases blood volume and blood viscosity of the neonate. Since both volume expansion and increase in blood viscosity may be associated with increased pulmonary artery pressure, we studied effects of transfusion (10 ml of red blood cells per kilogramme of body weight) on right ventricular output and right systolic time intervals by means of pulsed-Doppler echocardiography in 38 preterm infants with a mean (SD) gestational age of 28 (5) weeks (range 25–34), birth weight 1060 (395) g (range 480–1910), actual body weight 1875 (450) g (range 820–2790) and postnatal age of 44 (23) days (range 17–105). After transfusion, packed cell volume and haemoglobin increased significantly from 0.26 (0.044) to 0.38 (0.046), and from 8.2 (1.6) g/l to 12.8 (1.9), respectively. Blood viscosity increased from 1.78 (0.3) mPa to 2.68 (0.4) by 33%. Right ventricular output decreased significantly from 320 (57) ml/kg/min to 290 (70) due to decrease in heart rate by 7%. Blood pressure and right ventricular stroke volume did not change. There was a significant increase in pulmonary red cell transport (right ventricular output times packed cell volume) of 21%. Right ventricular pre-ejection period (RPEP), right time peak velocity (RTPV), right ventricular ejection time (RVET), and ratios of RTPV/RVET_(c), RPEP:RVET did not change after transfusion. Conclusion These results suggest that neither pulmonary artery pressure nor right ventricular function changed as a result of transfusion in spite of rising blood volume and blood viscosity. Received: 19 October 1996 / Accepted: 23 December 1996     

Effects of red cell transfusion on cardiac output and blood flow velocities in cerebral and gastrointestinal arteries in premature infants.

Anaemia may increase the risk of tissue hypoxia in preterm infants. The effect of transfusion on circulation was studied in 33 preterm infants with a mean (SD) gestational age of 29 (5) weeks (range 26-34), birth weight 1153 (390) g (range 520-1840), and postnatal age of 48 (21) days (range 19-100). Packed cell volume, blood viscosity (capillary viscometer), cardiac output, and cerebral blood flow velocities in the internal carotid artery, anterior cerebral artery, and coeliac trunk (Doppler ultrasound) were determined before and after transfusion of 10 ml/kg of packed red blood cells. Transfusion increased packed cell volume from a mean (SD) 0.27 (0.45) to 0.37 (0.48). Mean arterial blood pressure did not change while heart rate decreased significantly from 161 (14) l/min to 149 (12). Cardiac output decreased from 367 (93) ml/kg/min to 311 (74) due to decrease in stroke volume from 2.28 (0.57) ml/kg to 2.14 (0.46) and in heart rate. There was a significant increase in systemic red cell transport (cardiac output times packed cell volume) by 17%, systemic flow resistance (blood pressure to cardiac output ratio) by 23%, and blood viscosity by 33%. Vascular hindrance (flow resistance to blood viscosity ratio) did not change significantly, thereby suggesting that neither vasoconstriction nor vasodilation occurred with transfusion. After transfusion blood flow velocities decreased significantly in the anterior cerebral artery by 23%, in the internal carotid artery by 8%, and in the coeliac trunk by 12%. Red cell transport estimated as products of blood flow velocities times packed cell volume increased significantly by 25% in the internal carotid artery and by 21% in the coeliac trunk. These results indicate that red cell transfusion improved systemic oxygen transport as well as oxygen transport in the internal carotid artery and coeliac trunk.     

Postnatal adaptation of cerebral blood flow using near infrared spectroscopy in extremely preterm infants undergoing high-frequency oscillatory ventilation

Aim: To determine cerebral blood flow using near infrared spectroscopy in extremely preterm infants undergoing high-frequency oscillatory ventilation during the first three days of life. Low cerebral blood flow has been associated with both intra-ventricular haemorrhage and periventricu-lar leucomalacia. It is well established that cerebral blood flow increases over the first three days of life in extremely preterm infants who are conventionally ventilated with intermittent positive pressure ventilation. However, there is no information about cerebral blood flow in preterm babies undergoing high-frequency oscillatory ventilation. In addition, there are concerns that high-frequency oscillatory ventilation may be associated with an increased incidence of intra-ventricular haemorrhage in premature infants. Methods: Thirteen appropriately grown, preterm infants of less than 28 wk gestation who were admitted to the neonatal unit at University College Hospital, London were studied using near infrared spectroscopy. Left ventricular output and right ventricular output were assessed echocardiographically. Results: Extremely preterm infants undergoing high-frequency oscillatory ventilation have remarkably low cerebral blood flow in the first 12 h of life, median 6.7 (range 4.4-11) mls. 100 g[Formula: See Text] min[Formula: See Text] followed by an increase over the subsequent three days. Left ventricular output also increased over the first three days of life, whereas right ventricular output showed no clear relationship with time. Despite low cerebral blood flow only one infant had evidence of major cerebral injury.

Conclusion: Cerebral blood flow is extremely low in this group of preterm babies. Despite this extremely low cerebral blood flow, the clinical outcome is good. There was an increase in cerebral blood flow and a corresponding increase in left ventricular output over the first few days of life.     

Effect of transfusion on the venous blood lactate level in very low-birthweight infants

Background:  In recent years the blood lactate level can be easily and quickly measured with a small amount of blood, and the availability of an arterial blood lactate level has been reported as an indicator of oxygen deficit in adults. To determine whether venous blood lactate level can serve as such a marker for determining the indications for transfusion, blood lactate and hemoglobin level were monitored before and after transfusion.
Methods:  The study subjects consisted of 12 very low-birthweight infants admitted to the neonatal intensive care unit and who had transfusion between June 2005 and June 2007. The data on the blood lactate and hemoglobin were collected retrospectively by referring to the clinical records.
Results:  A total of 18 transfusions was performed. There was no significant relationship between venous blood lactate and hemoglobin concentration before transfusion. The subjects were classified into two groups according to the lactate level before transfusion: 3.3 mmol/L and <3.3 mmol/L. In the high-lactate group the lactate decreased significantly after transfusion ( P  < 0.01) and it continued to decrease thereafter. In the low-lactate group, however, the lactate remained unchanged.
Conclusions:  Venous blood lactate measurements may offer some additional information regarding the optimal time for performing a transfusion. To the authors' knowledge this is the first report to study the changes in lactate levels using venous blood sampling in red blood cell transfusion in very low-birthweight infants.     

Effects of partial plasma exchange transfusion on cerebral blood flow velocity in polycythaemic preterm,term and small for date newborn infants

Isovolemic haemodilution with plasma was performed in 36 newborn infants with polycythaemia 3 h after birth. Continuous wave Doppler ultrasonography was used to study the short and longer term influence of partial plasma exchange transfusion on cerebral blood flow velocity in both the anterior cerebral and mid cerebral arterial system up to 24 h after haemodilution. The study group consisted of 11 preterm infants, 12 term infants, and 13 small for date infants. After exchange transfusion peripheral venous haemotocrit decreased from 72.5% to 59.4%. In all experimental groups cerebral blood flow velocity (CBFV) before exchange transfution was significantly lower (18%–44%) than matched controls, and increased to control levels after exchange transfusion. CBFV improved most in preterm infants. After the transfusion the values were no different from the age-, weight-, sex-and parity-matched control groups, and they remained at this level during the next 24 h. No differences could be found between the anterior and mid-cerebral arterial system. When clinical symptoms were present, they subsided in all infants. In conclusion, partial plasma exchange transfusion has a favourable effect for at least 24 h on cerebral blood flow velocity in newborn infants with polycythaemia.Abbreviations AUC area under the curve (mean flow velocity) - CBFV cerebral blood flow velocity - EDFV end diastolic flow velocity - Hct haematocrit - PI pulsatility index according to Pourcelot - PRET partial plasma exchange transfusion - PSFV peak systolic flow velocity     

Childhood cardiac function after twin-to-twin transfusion syndrome – a 10-year follow up

Aim:  To perform a 10-year follow up of cardiac structure and function after twin-to-twin transfusion syndrome (TTTS) – a severe foetal circulatory complication associated with myocardial hypertrophy in the recipient twin.
Methods:  Cardiac dimensions, systolic and diastolic function as assessed by echocardiography including flow and tissue Doppler velocimetry in 22 healthy survivors of TTTS with a mean age of 9.6 (7.2–11.8) years.
Results:  The donor and recipient twin did not show any differences in end-diastolic ventricular size, interventricular septum thickness, diameter of right ventricular outflow tract, cardiac valves, coronary arteries or in systolic blood flow velocities. However, compared with the donors, the recipients had significantly lower E/A ratios because of lower E-waves in both mitral (−0.15 ± 0.10, p < 0.01) and tricuspid (−0.09 ± 0.07, p < 0.01) valves, indicating reduced early diastolic ventricular fillings compared with donors.
Conclusion:  At school age, twins surviving TTTS had a cardiac structure and function within normal range. There were no differences in heart structure or systolic ventricular function between twins but, compared with the donor twin, we found a reduced early diastolic function in the recipient.     

Haemodynamic effects of differing blood transfusion rates in infants less than 1500 g

Objective : To investigate whether the haemodynamic effects of the standard 2-3 h blood transfusion increases the risk for intraventricular haemorrhage (IVH) and patent ductus arteriosus (PDA) in very low birthweight infants.
Methodology : In a randomized controlled study, haemodynamic changes using slow and rapid transfusion were compared. Twenty-seven very low birthweight infants were divided between 12 h ( n = 14) and 3 h ( n = 13) transfusion groups. Blood pressure, ejection fraction (EF), anterior cerebral artery pulsatility index (Pl), blood gases, serum electrolytes and haematocrit were measured pre- and post-transfusion. Infectious status was also monitored.
Results : Blood pressure (48.1/25.5 vs 55.7/30.2 mmHg) and EF (0.68 vs 0.73) increased significantly during rapid transfusion ( P >0.01) but remained stable with slow transfusion. Serum potassium, base excess and incidence of infection did not increase in either group.
Conclusions : Slow transfusion causes less haemodynamic disturbance than rapid transfusion, thereby preventing the potential risk for IVH and PDA.     

The contractility and performance of the preterm left ventricle before and after early patent ductus arteriosus occlusion in surfactant-treated lambs

The influence of left-right ductal shunting on early hemodynamic responses, namely left ventricular performance, contractility, and systemic perfusion was evaluated in nine preterm lambs (120 days gestational age) treated with surfactant. Blood gases were maintained in the physiological range using mechanical ventilation; hemodynamic and blood flow measurements (radionuclide labeled microspheres) were obtained before and after occlusion of the patent ductus arteriosus with a catheter balloon. The mean left-right ductal shunt before occlusion (1.2 h postnatal age) was 59 +/- 11% SD. Left ventricular output was increased in all lambs with PDA (pre: 306 +/- 106 versus post: 155 +/- 31 ml/min/kg; p less than 0.001); effective systemic blood flow and organ blood flows did not change. The left ventricle end-diastolic volume was increased in all and decreased following ductal occlusion (pre: 2.0 +/- 0.4 versus post: 1.5 +/- 0.2 ml/kg; p less than 0.01). Cardiac rate, ejection fraction, and contractility (peak dP/dt) did not change. Right-left ductal shunting was not detected in six similarly treated lambs. Thus, during the 1st h of life the hemodynamic profile of preterm lambs with patent ductus arteriosus was characterized by large magnitude left-right shunt and a "high" cardiac output state sufficient to maintain unchanged systemic perfusion. The increased left ventricle output was accomplished by increasing end-diastolic volume (Frank-Starling mechanism), but left ventricle contractility remained unchanged. We speculate that the preterm left ventricle may be unable to sustain the high level of pump performance and contractility required to compensate for the ductal "steal" of systemic blood flow.     

Short-term effects of blood transfusion on blood volume and resting peripheral blood flow in preterm infants

The effects of blood transfusion on cardiac output and blood pressure are variable, but resting peripheral blood flow (RPBF) may be a sensitive indicator of changes in blood volume. The purpose of this investigation was to study the effects of red cell transfusion on blood volume (Evans blue), blood pressure, RPBF in the leg (strain-gauge plethysmography) and blood viscosity (cone-plate viscometer) in preterm infants during the first week after birth. Fourteen infants with mean ± SD birth weight of 1658 ± 429 g, gestational age 33 ± 3 weeks and postnatal age 64 ± 40 h received 18 ±4 ml/kg of packed red cells (red cells 11±2 ml/kg, plasma 7± 1 ml/kg) because their hematocrit was less than 0.45 l/l. Mean blood volume before transfusion was 88±15 ml/kg. The increase in blood volume (9 ±4 ml/kg) measured 4 to 6 h after transfusion was smaller than the transfused volume (18 ± 4 ml/kg), due to a shift of plasma to the extravascular space. The plasma shift increased with increasing pretransfusion blood volume ( r = 0.70; p = 0.007). Red cell transfusion caused an increase in RPBF by 25% ( p <0.01), whereas systolic blood pressure (BP) increased by only 12%. Peripheral resistance (R = BP/RPBF) decreased by 9% (p<0.01). Blood viscosity (±) increased by 21'% ( p <0.001) and vascular hindrance (R/±) decreased by 24% ( p < 0.001), indicating vasodilatation of limb arteries. The increase in RPBF and the decrease in hindrance were particularly pronounced in infants with high pretransfusion blood volume. We conclude that the increase in blood volume after transfusion is not proportional to the transfused volume and that RPBF increases more than systolic blood pressure with increasing blood volume. The increase in RPBF can be explained by vasodilatation of limb arteries and by increased blood pressure.     

Circulatory changes induced by isovolumic increase in red cell mass in fetal lambs

AIM: To verify whether extra uterine changes in total peripheral vascular resistance and cardiac output, caused by raised haematocrit, occur in fetal life and if they can be documented using conventional ultrasound techniques. METHODS: An exchange transfusion with packed red cells was performed on five fetal lambs at 140 days of gestation (weight 3.44, SD 0.48 kg); three others were used as controls. The haematocrit was raised from 44 +/- 3 to 64 (SD2)%. RESULTS: Body temperature, blood gas, and pH remained within normal limits. Blood viscosity increased from 5.3 (0.3) to 9.6 (1.6) cps. Combined cardiac output fell to 30% of its initial value. The pulsatility index (PI) remained unchanged in the umbilical artery (0.66, SD 0.1) and descending aorta (1.3, SD 0.3). A significant positive correlation was found between haematocrit and PI only in the carotid artery (r = 0.67, p < 0.01). CONCLUSION: In the fetus, as in adults, an increase in blood viscosity is associated with a fall in cardiac output. However, the low resistance and the relative inertia of the placental vascular bed blunt the velocimetric changes that could be induced in the lower body vascular system by an increase in resistance. Such changes were observed only in the carotid artery. These results could be of interest in the Doppler monitoring of human fetuses at risk of an abnormal increase in their haematocrit.