Regional hemodynamic effects of dopamine in the sick preterm neonate

Renal Oxygen Saturations and Acute Kidney Injury in the Preterm Infant with Patent Ductus Arteriosus

OBJECTIVE

Decreased near-infrared spectroscopy (NIRS) measures of renal oxygen saturation (Rsat) have identified preterm infants with a hemodynamically significant patent ductus arteriosus (hsPDA). NIRS may further identify infants at risk for acute kidney injury (AKI) in a population with concern for hsPDA.

STUDY DESIGN

Review of infants ≤29 weeks' gestation undergoing NIRS and echocardiography due to concern for hsPDA. The hsPDA was defined by two of the following: moderate-large size, left to right shunt, aortic flow reversal, left atrial enlargement. AKI was defined by neonatal modified Kidney Disease Improving Global Outcomes (KDIGO). Rsat and cerebral saturation (Csat), averaged over 1 hour, were evaluated for the 24-hour period around echocardiography.

RESULTS

Among 77 infants, 29 (38%) had AKI by neonatal modified KDIGO criteria. hsPDA was found on echocardiography in 59 (77%). There were no differences in hsPDA in infants with and without AKI (p = 0.1). Rsat was not associated with AKI (p = 0.3). Infants on dopamine had less Rsat variability (p < 0.01).

CONCLUSION

Rsat prior to echocardiography did not discriminate AKI in this cohort of preterm infants at risk for hsPDA; however, data may not capture optimal timing of Rsat measurement before AKI.

KEY POINTS

· No Rsat value was found to be associated with the development of AKI.. · The optimal timing of Rsat measurement should be evaluated in infants at risk for hsPDA.. · NIRS bedside monitoring of Csat and Rsat measures may be useful in trending perfusion patterns.. · Identification of those at high risk for AKI may allow for more careful kidney function monitoring..

The Use of Low-Dose Dopamine in the Neonatal Intensive Care Unit

Dopamine has been used for half a century in adult and pediatric patients for the treatment of hypotension, as well as for the theoretical prevention of acute kidney injury (AKI). Although activation of renal dopamine receptors leads to increased urine output, there is no evidence that low-dose dopamine reduces the incidence of AKI, need for dialysis, or death. Dopamine administration is also associated with multiple adverse effects, particularly in preterm infants. Despite the lack of evidence for its use, as well as the known adverse effects of dopamine, many neonatologists still use low-dose dopamine to prevent or treat AKI in neonates. In this review, we provide a summary of our current medical knowledge about the use of low-dose dopamine in the neonatal population.

The Use of Low-Dose Dopamine in the Neonatal Intensive Care Unit

Dopamine has been used for half a century in adult and pediatric patients for the treatment of hypotension, as well as for the theoretical prevention of acute kidney injury (AKI). Although activation of renal dopamine receptors leads to increased urine output, there is no evidence that low-dose dopamine reduces the incidence of AKI, need for dialysis, or death. Dopamine administration is also associated with multiple adverse effects, particularly in preterm infants. Despite the lack of evidence for its use, as well as the known adverse effects of dopamine, many neonatologists still use low-dose dopamine to prevent or treat AKI in neonates. In this review, we provide a summary of our current medical knowledge about the use of low-dose dopamine in the neonatal population.

Blood Pressure Goals: Is Cerebral Saturation the New Mean Arterial Pressure?

OBJECTIVE

The objective of this article was to correlate hypotension and cerebral saturation from near-infrared spectroscopy (cNIRS) in neonates on dopamine.

STUDY DESIGN

Retrospective review of neonates receiving dopamine between August 2018 and 2019 was performed. Hypotension thresholds included mean arterial pressure (MAP) of postmenstrual age (PMA) ± 5 and 30 mm Hg and gestational age (GA) ± 5 mm Hg. Time below threshold MAP was compared with time with cerebral hypoxia (cNIRS <55%).

RESULTS

Hypotension occurred 6 to 33% of the time on dopamine in 59 cases. Hypotension did not correlate with abnormal cNIRS overall, within PMA subgroups or by outcomes. Hypotensive periods with MAP < GA had fewer corresponding percent time with abnormal cNIRS events (3.7 ± 1.3%) compared with MAP < PMA (11.9 ± 4.9%, p < 0.003) or 30 mm Hg thresholds (12.2 ± 4.7%, p < 0.0001). In most premature infants, mean cNIRS values during hypotension were still within normal range (57 ± 6%).

CONCLUSION

cNIRS may be a more clinically relevant measure than MAP for the assessment of neonatal hypotension.

KEY POINTS

· Hypotension occurred 6 to 33% of the time on dopamine in 59 cases.. · Hypotension did not correlate with abnormal cNIRS overall, within PMA subgroups or by outcomes.. · MAP. · We found no cNIRS difference between IVH grades, mortality, average Hct, lactates, or urine output.. · cNIRS may be a more clinically relevant measure than MAP for the assessment of neonatal hypotension..

To Feed or Not to Feed: A Critical Overview of Enteral Feeding Management and Gastrointestinal Complications in Preterm Neonates with a Patent Ductus Arteriosus

The management of enteral feeds in preterm infants with a hemodynamically significant patent ductus arteriosus (hs-PDA) is a major challenge for neonatologists due to the fear of gastrointestinal (GI) complications. This review aims to analyze the available evidence on the complex relation between the presence and management of PDA, enteral feeding practices, and GI outcomes in the preterm population. There is limited evidence, based on small and heterogeneous trials, that hs-PDA may affect the splanchnic hemodynamic response to enteral feeds. While the presence of PDA seems a risk factor for adverse GI outcomes, the benefits of feeding withholding during pharmacological PDA treatment are controversial. The lack of robust evidence in support of or against a timely feeding introduction or feeding withholding during pharmacological PDA closure in preterm neonates does not allow to draw any related recommendation. While waiting for further data, the feeding management of this population should be carefully evaluated and possibly individualized on the basis of the infants’ hemodynamic and clinical characteristics. Large, multicentric trials would help to better clarify the physiological mechanisms underlying the development of gut hypoperfusion, and to evaluate the impact of enteral feeds on splanchnic hemodynamics in relation to PDA features and treatment.

The Use of Cardiotonic Drugs in Neonates

There is a distinct lack of age-appropriate cardiotonic drugs, and adult derived formulations continue to be administered, without evidence-based knowledge on their dosing, safety, efficacy, and long-term effects. Dopamine remains the most commonly studied and prescribed cardiotonic drug in the neonatal intensive care unit (NICU), but evidence of its effect on endorgan perfusion still remains. Unlike adult and pediatric critical care, there are significant gaps in our knowledge on the use of various cardiotonic drugs in various forms of circulatory failure in the NICU.

Dopamine plasma clearance is increased in piglets compared to neonates during continuous dopamine infusion

AIM

Piglets models have often been used to study the effects of dopamine infusion on hypotension in neonates. However, piglets need higher doses of dopamine than neonates to increase blood pressure. We investigated whether this difference was due to interspecific difference in dopamine pharmacokinetics.

METHODS

Arterial blood samples were drawn from six neonates admitted to the neonatal intensive care unit of Copenhagen University Hospital and 20 newborn piglets during continuous dopamine infusion. Furthermore, to estimate the piglet plasma dopamine half-life, blood samples were drawn at 2.5-minute intervals after the dopamine infusion was discontinued. The plasma dopamine content was analysed by high-performance liquid chromatography with electrochemical detection.

RESULTS

The dopamine displayed first-order kinetics in piglets and had a half-life of 2.5 minutes, while the median plasma clearance was 627.9 mL/kg/minute (interquartile range 452.6-1914.4). Both piglets and neonates showed large interindividual variations in plasma clearance, but the median tended to be lower in neonates (384.9, interquartile range 114.2-480.2 mL/kg/minute).

CONCLUSION

Our results suggest that pharmacokinetic differences may explain the interspecific difference in required doses of dopamine infusion to increase blood pressure. This is important when translating the results obtained in piglet models to treating neonatal hypotension with dopamine.

Inotropes for Preterm Infants: 50 Years on Are We Any Wiser?

For almost half a century, inotropes have been administered to preterm infants with the ultimate goal of increasing their blood pressure. A number of trials, the majority of which focused on dopamine administration, have demonstrated increased blood pressure following inotrope administration in preterm infants and have led to continued use of inotropes in our neonatal units. We have also seen an increase in the number of potential agents available to the clinician. However, we now know that hypotension is a much broader concept than blood pressure alone, and our aim should instead be focused on improving end organ perfusion, specifically cerebral perfusion. Only a limited number of studies have incorporated the organ-relevant hemodynamic changes and long-term outcomes when assessing inotropic effects in neonates, the majority of which are observational studies or have a small sample size. In addition, important considerations, including the developing/maturing adrenergic receptors, polymorphisms of these receptors, and other differences in the pharmacokinetics and pharmacodynamics of preterm infants, are only recently being recognized. Certainly, there remains huge variation in practice. The lack of well-conducted randomized controlled trials addressing these relevant outcomes, along with the difficulty executing such RCTs, leaves us with more questions than answers. This review provides an overview of the various inotropic agents currently being used in the care of preterm infants, with a particular focus on their organ/cerebral hemodynamic effects both during and after transition.

Pharmacological management of acute kidney injury and chronic kidney disease in neonates

Both acute kidney injury (AKI) and chronic kidney disease (CKD) are seen more frequently in the neonatal intensive care unit (NICU) as advances in supportive care improve the survival of critically ill infants as well as those with severe, congenital kidney and urinary tract anomalies. Many aspects of the infant's care, including fluid balance, electrolyte and mineral homeostasis, acid-base balance, and growth and nutrition require close monitoring by and collaboration among neonatologists, nephrologists, dieticians, and pharmacologists. This educational review summarizes the therapies widely used for neonates with AKI and CKD. Use of these therapies is extrapolated from data in older children and adults or based on clinical experience and case series. There is a critical need for more research on the use of therapies in infants with kidney disease as well as for the development of drug delivery systems and preparations scaled more appropriately for these small patients.

How to find and how to read articles in neonatology

Staying abreast of the neonatal literature is an important task. Being aware of new information and knowing how to evaluate its reliability remain essential to be able to provide the most appropriate, evidence-based, therapy to our patients. This article discusses methods for being informed of, and critically reviewing, published research in order to fulfill these tasks without being overwhelmed by the number or complexity of publications.

Acute kidney injury in the neonate

Critically ill neonates are at risk for acute kidney injury (AKI). AKI has been associated with increased risk of morbidity and mortality in adult and pediatric patients, and increasing evidence suggests a similar association in the neonatal population. This article describes the current AKI definitions (including their limitations), work on novel biomarkers to define AKI, diagnosis and management strategies, long-term outcomes after AKI, and future directions for much-needed research in this important area.

Diagnosis and management of hypotension in neonates

The diagnosis and management of hypotension in neonates is a frequently encountered issue in the intensive care setting. There is an ongoing debate as to the appropriateness of blood pressure monitoring as an indicator of organ perfusion and tissue hypoxia. These ultimately determine morbidity and mortality in the sick newborn. This article explores the methods available for the assessment of organ perfusion and speculates on other means that may become available in the future. Different modalities of treatment currently in use are discussed, with the aim of using information gained from perfusion monitoring techniques to determine the optimal choice of therapy.

Effects of low-dose dopamine on urine output in normotensive very low birth weight neonates

OBJECTIVE

To determine the effects of low-dose dopamine on urine output (UOP) in very low birth weight premature neonates.

STUDY DESIGN

Retrospective cohort study of all low-dose (3-5 μg kg(-1) per min) dopamine infusions >24-h duration in neonates 1500 g and 32 weeks gestation from August 2009 through September 2011. Linear regression was used to estimate the impact of covariates on UOP.

RESULT

We identified 91 episodes of low-dose dopamine use in 65 neonates. Increased UOP occurred in 64% of episodes. Low-dose dopamine use was associated with a 0.6 ml kg(-1) h(-1) increase in UOP (P<0.001) and a 1.3 ml kg(-1)h(-1) increase when baseline UOP was <1.5 ml kg(-1) h(-1) (P<0.001). The improvement remained statistically significant after controlling for medications (diuretics and hydrocortisone) and fluid intake.

CONCLUSION

Low-dose dopamine use was associated with increased UOP in very low birth weight neonates.

Cerebral effects of commonly used vasopressor-inotropes: a study in newborn piglets

Background

Despite widespread use in sick infants, it is still debated whether vasopressor-inotropes have direct cerebral effects that might affect neurological outcome. We aimed to test direct cerebrovascular effects of three commonly used vasopressor-inotropes (adrenaline, dopamine and noradrenaline) by comparing the responses to those of nonpharmacologically induced increases in blood pressure. We also searched for reasons for a mismatch between the response in perfusion and oxygenation.

Methods

Twenty-four piglets had long and short infusions of the three vasopressor-inotropes titrated to raise mean arterial blood pressure (MAP) 10 mmHg in random order. Nonpharmacological increases in MAP were induced by inflation of a balloon in the descending aorta. We measured cerebral oxygenation (near-infrared spectroscopy), perfusion (laser-Doppler), oxygen consumption (co-oximetry of arterial and superior sagittal sinus blood), and microvascular heterogeneity (side stream dark field video microscopy).

Results

Vasopressor-inotropes increased cerebral oxygenation significantly less (p≤0.01) compared to non-pharmacological MAP increases, whereas perfusion was similar. Furthermore, cerebral total hemoglobin concentration increased significantly less during vasopressor-inotrope infusions (p = 0.001). These physiologic responses were identical between the three vasopressor-inotropes (p>0.05). Furthermore, they induced a mild, although insignificant increase in cerebral metabolism and microvascular heterogeneity (p>0.05). Removal of the scalp tissue did not influence the mismatch (p>0.05).

Conclusion

We demonstrated a moderate vasopressor-inotrope induced mismatch between cerebral perfusion and oxygenation. Scalp removal did not affect this mismatch, why vasopressor-inotropes appear to have direct cerebral actions. The statistically nonsignificant increases in cerebral metabolism and/or microvascular heterogeneity may explain the mismatch. Alternatively, it may simply reflect a vasopressor-inotrope-induced decrease in the arterial-to-venous volume ratio as detected by near-infrared spectroscopy.

Challenges in understanding the impact of blood pressure management on cerebral oxygenation in the preterm brain

Systemic hypotension in preterm infants has been related to increased mortality, cerebrovascular lesions, and neurodevelopmental morbidity. Treatment of hypotension with inotropic medications aims at preservation of end organ perfusion and oxygen delivery, especially the brain. The common inotropic medications in preterm infants include dopamine, dobutamine, adrenaline, with adjunctive use of corticosteroids in cases of refractory hypotension. Whether maintenance of mean arterial blood pressure (MAP) by use of inotropic medication is neuroprotective or not remains unclear. This review explores the different inotropic agents and their effects on perfusion and oxygenation in the preterm brain, in clinical studies as well as in animal models. Dopamine and adrenalin, because of their α-adrenergic vasoconstrictor actions, have raised concerns of reduction in cerebral blood flow (CBF). Several studies in hypotensive preterm infants have shown that dopamine elevates CBF together with increased MAP, in keeping with limited cerebro-autoregulation. Adrenaline is also effective in raising cerebral perfusion together with MAP in preterm infants. Experimental studies in immature animals show no cerebro-vasoconstrictive effects of dopamine or adrenaline, but demonstrate the consistent findings of increased cerebral perfusion and oxygenation with the use of dopamine, dobutamine, and adrenaline, alongside with raised MAP. Both clinical and animal studies report the transitory effects of adrenaline in increasing plasma lactate, and blood glucose, which might render its use as a 2nd line therapy. To investigate the cerebral effects of inotropic agents in long-term outcome in hypotensive preterm infants, carefully designed prospective research possibly including preterm infants with permissive hypotension is required. Preterm animal models would be useful in investigating the relationship between the physiological effects of inotropes and histopathology outcomes in the developing brain.

Neonatal pharmacology: extensive interindividual variability despite limited size

Providing safe and effective drug therapy to neonates requires knowledge of the impact of development on the pharmacokinetics and pharmacodynamics of drugs. Although maturational changes are observed throughout childhood, they are most prominent during the first year of life. Several of these processes overlap, making development an extremely dynamic system in the newborn compared with that in infants, children, or adults. Changes in body composition and porportions, liver mass, metabolic activity, and renal function collectively affect the pharmacokinetic behavior of medications. Instead of simply adapting doses by scaling adult or pediatric doses on the basis of a patient's weight and/or body surface area, integrated knowledge of clinical maturation and developmental pharmacology is critical to the safe and effective use of medications in neonates. Unfortunately, the effects of human ontogeny on both pharmacokinetics and pharmacodynamics have not been well established in these early stages of life, and information regarding the influence of developmental changes on the pharmacodynamics of medications is even more limited. Theoretically, age-dependent variations in receptor number and affinity for drugs have significant potential to influence an individual's response to drug therapy. In this review, some of the relevant covariates of pharmacokinetics and pharmacodynamics in neonates are reviewed and illustrated based on the published literature.

Cerebral vascular effects of hypovolemia and dopamine infusions: a study in newborn piglets

AIM

Despite widespread use, effects of volume boluses and dopamine in hypotensive newborn infants remain controversial. We aimed to elucidate if hypovolemia alone impairs cerebral autoregulation (CA) and if dopamine affects cerebral vasculature.

METHODS

In 12 piglets, cerebral perfusion (laser-Doppler flux) and oxygenation [near-infrared spectroscopy (NIRS)] were examined during dopamine (20-50 μg/kg per minute) and nonpharmacologically induced blood pressure (ABP) changes. Effect on cerebral perfusion and oxygenation was quantified as frequency gain between ABP and laser-Doppler flux (gain-LDF) and NIRS [gain-oxygenation index (OI)], respectively. Gain quantifies change in perfusion or oxygenation per ABP-change. CA was estimated as gain-LDF during nonpharmacologically induced ABP changes, that is, as degree of impairment. Dopamine's cerebrovascular effect was estimated by contrasting gain during dopamine- and nonpharmacologically induced ABP changes. Measurements were conducted during both normovolemia- and haemorrhage-induced hypovolemia.

RESULTS

Hypovolemia elicited hypotension (p = 0.02) as well as increasing impairment of CA (p = 0.01). However, hypovolemia without hypotension did not affect CA significantly. Dopamine increased perfusion significantly compared to nonpharmacological challenges (mean difference: 1.5%/mmHg, 95% CI: 0.5-2.6, p = 0.007). Oxygenation was, however, similar (mean difference: 0.01 μmol/L per mmHg, 95% CI: -0.03 to 0.05, p = 0.7).

CONCLUSION

Our findings do not support that hypovolemia alone impairs CA. Furthermore, dopamine seems to increase cerebral perfusion but not oxygenation.

Effect of dopamine on peripheral perfusion in very-low-birth-weight infants during the transitional period

INTRODUCTION

Dopamine is one of the most frequently used inotropic drugs in neonatal intensive care units (NICUs); however, it does not seem to improve outcomes in premature infants. Given that the ultimate aim of cardiovascular management is to stabilize and maintain organ perfusion, an understanding of dopamine's effects on organ blood flow will help in judging when to use dopamine and how to titrate the dosage. Such an approach can lead to improved outcomes. This study aimed to evaluate the effects of dopamine on peripheral perfusion in very-low-birth-weight (VLBW) infants within 72 h of birth.

METHODS

This prospective observational study identified and sampled 44 instances of initiation of dopamine treatment or increase in dopamine dose in 29 VLBW infants. Blood pressure, heart rate, and skin and subcutaneous blood flow were measured and compared before and after each instance.

RESULTS

Blood pressure and skin and subcutaneous blood flow in the lower limbs increased after initiation of dopamine treatment or after dose increase.

DISCUSSION

Dopamine increases blood pressure as well as skin and subcutaneous blood flow in VLBW infants despite its supposed vasoconstrictive action, indicating that it increases both perfusion pressure and blood flow and is devoid of overwhelming peripheral vasoconstrictive effects.

Neonatal blood pressure support: the use of inotropes, lusitropes, and other vasopressor agents

A solid understanding of the mechanisms of action of cardiovascular medications used in clinical practice along with efforts to develop comprehensive hemodynamic monitoring systems to improve the ability to accurately identify the underlying pathophysiology of cardiovascular compromise are essential in the management of neonates with shock. This article reviews the mechanisms of action of the most frequently used cardiovascular medications in neonates. Because of paucity of data from controlled clinical trials, evidence-based recommendations for the clinical use of these medications could not be made. Careful titration of the given medication with close monitoring of the cardiovascular response might improve the effectiveness and decrease the risks associated with administration of these medications.

Effect of antihypotensive treatment on cerebral oxygenation of preterm infants without PDA

BACKGROUND

Preterm infants with hypotension (mean arterial blood pressure [MABP] < gestational age [GA]) are treated with volume expansion and/or dopamine to ensure adequate cerebral perfusion/oxygenation. We used near-infrared spectroscopy to analyze the effects of volume expansion and dopamine on cerebral oxygenation in hypotensive preterm infants without patent ductus arteriosus (PDA).

PATIENTS AND METHODS

Among 390 infants, 71 (GA < 32 weeks) were hypotensive and eligible for inclusion. Thirty-three infants received volume expansion only (NaCl 0.9%; 20 mL/kg), and 38 received additional dopamine (5 μg/kg per minute). Nine and 11 infants initially treated with dopamine subsequently needed 7.5 and 10 μg/kg per minute, respectively. Seventy-one infants without hypotension were individually matched to serve as controls. MABP, regional cerebral oxygen saturation (rSco(2)), fractional tissue oxygen extraction (cFTOE), and arterial saturation (Sao(2)) were monitored 15 minutes before and 30 and 60 minutes after volume or dopamine and at comparable postnatal ages in controls.

RESULTS

No changes in MABP, rSco(2), or cFTOE were found 30 minutes after volume expansion. MABP increased 60 minutes after 5 μg/kg per minute dopamine (median [range]: 28 [19-32] vs 33 [23-46] mm Hg; P < .001). There was a small increase and decrease, respectively, in rSco(2) (63 [43-84] vs 66 [46-87]%; P < .05) and cFTOE (0.33 [0.14-0.56] vs 0.31 [0.07-0.54]1/1; P < .05). However, no differences were found at any time point between controls and infants treated with volume or additional dopamine (5, 7.5, and 10 μg/kg per minute) for rSco(2) or cFTOE.

CONCLUSIONS

Volume expansion and additional dopamine do not cause any significant change in rSco(2) or cFTOE in hypotensive preterm infants without PDA. We speculate that very preterm infants with hypotension but without signs of a compromised cerebral oxygenation and systemic perfusion might not be in need of antihypotensive therapy.

Dose-dependent hemodynamic and metabolic effects of vasoactive medications in normotensive, anesthetized neonatal piglets

The developmentally regulated hemodynamic effects of vasoactive medications have not been well characterized. We used traditional and near-infrared spectroscopy monitoring technologies and investigated the changes in heart rate, blood pressure, common carotid artery (CCA) blood flow (BF), cerebral, renal, intestinal, and muscle regional tissue O2 saturation, and acid-base and electrolyte status in response to escalating doses of vasoactive medications in normotensive anesthetized neonatal piglets. We used regional tissue O2 saturation and CCA BF as surrogates of organ and systemic BF, respectively, and controlled minute ventilation and oxygenation. Low to medium doses of dopamine, epinephrine, dobutamine, and norepinephrine increased blood pressure and systemic and regional BF in a drug-specific manner, whereas milrinone exerted minimal effects. At higher doses, dopamine, epinephrine, and norepinephrine but not dobutamine decreased systemic, renal, intestinal, and muscle BF, while cerebral BF remained unchanged. Epinephrine induced significant increases in muscle BF and serum glucose and lactate concentrations. The findings reveal novel drug- and dose-specific differences in the hemodynamic response to escalating doses of vasoactive medications in the neonatal cardiovascular system and provide information for future clinical studies investigating the use of vasoactive medications for the treatment of neonatal cardiovascular compromise.

A meta-analysis of dopamine use in hypotensive preterm infants: blood pressure and cerebral hemodynamics

OBJECTIVE

Dopamine administration results in variable effects on blood pressure in hypotensive preterm infants. The clinical benefits of dopamine administration in increasing cerebral blood flow (CBF) and reducing adverse neurological outcomes in hypotensive preterm neonates are unclear. The objective of this study was to examine the efficacy of dopamine for treatment of hypotension and investigate the changes in cerebral hemodynamics and central nervous system injury in hypotensive preterm infants following dopamine administration.

STUDY DESIGN

Standard meta-analytic techniques, including random and fixed effects models, were used to calculate combined effect size correlations and significance levels.

RESULT

Random effects meta-analysis found that dopamine increases mean arterial blood pressure (12 studies; N=163; r=0.88, 95% confidence interval (CI)=0.76 to 0.94) and systolic blood pressure (8 studies; N=142; r=0.81, 95% CI=0.42 to 0.94). For the increase in blood pressure, dopamine administration was associated with a significantly greater overall efficacy than dobutamine (seven studies; N=251; r=0.26; 95% CI=0.20 to 0.32), colloid (two studies; N=67; r=0.60; 95% CI=0.41 to 0.74) and hydrocortisone (one study; N=28; r=0.40; 95% CI=0.034 to 0.67). CBF increased following dopamine administration (five studies; N=75; r=0.36; 95% CI=-0.059 to 0.67) and the increase in CBF was greater in hypotensive than normotensive preterm infants (eight studies; N=153; r=0.16; 95% CI=-0.0080 to 0.32). There were no statistically significant differences in adverse neurological outcome between dopamine and dobutamine (three studies; N=118; r=-0.13; 95% CI=-0.31 to 0.059), epinephrine (two studies; N=46; r=0.06; 95% CI=-0.23 to 0.34), colloid (two studies; N=80; r=0.0070; 95% CI=-0.218 to 0.23) or hydrocortisone administration (one study; N=40; r=-0.10; 95% CI=-0.40 to 0.22).

CONCLUSION

Dopamine administration increases mean and systolic blood pressure in hypotensive preterm infants, and is more effective than dobutamine, colloid or hydrocortisone alone. Dopamine administration is associated with increased CBF, with greater increases in CBF in hypotensive than in normotensive preterm infants. Dopamine is not associated with a greater incidence of adverse effects than other therapies used to treat hypotension.

Systemic and cerebral hemodynamics during the transitional period after premature birth

Little is known about the effect on clinically relevant outcomes of the complex hemodynamic changes occurring during adaptation to extrauterine life in preterm neonates, particularly in very low birth weight neonates. As cardiovascular adaptation in this extremely vulnerable patient population is complicated by immaturity of all organ systems, especially that of the cardiorespiratory, central nervous, and endocrine systems, maladaptation has been suspected, but not necessarily proven, to contribute to mortality and long-term morbidities. This article describes recent advances in the understanding of hemodynamic changes in very low birth weight neonates during postnatal transition, and reviews the complex and developmentally regulated interaction between systemic and cerebral hemodynamics and the effect of this interaction on clinically relevant outcomes.

The role of systemic hemodynamic disturbances in prematurity-related brain injury

Premature infants who experience cerebrovascular injury frequently have acute and long-term neurologic complications. In this article, we explore the relationship between systemic hemodynamic insults and brain injury in this patient population and the mechanisms that might be at play.

Cerebral blood flow velocities in extremely low birth weight infants with hypotension and infants with normal blood pressure

OBJECTIVE

To determine whether extremely low birth weight (ELBW) infants with hypotension have similar cerebral hemodynamics when compared with control subjects with normal blood pressure. We hypothesized that ELBW infants with low or normal blood pressure have similar cerebral blood flow (CBF) velocity.

STUDY DESIGN

In this case control study, CBF velocity (with Doppler ultrasound scanning), PCO2, and mean arterial blood pressure (MABP) were continuously monitored twice daily before intensive care procedures. If an infant became hypotensive (MABP < or = gestational age in weeks), additional monitoring was performed for 10 to 20 minutes, before treatment with dopamine. Thirty ELBW infants were enrolled (637 +/- 140 g, 24.2 +/- 1.1 weeks); 15 had hypotension, and 15 were gestational age/birth weight-matched control subjects with normal blood pressure. CBF velocity was compared by use of the Mann-Whitney U test.

RESULTS

The groups did not differ significantly in gestational age, birth weight, race, sex, PCO2, Apgar scores, or occurrence of severe intraventricular hemorrhage. There was no difference in mean CBF velocity (P = .934) in infants with hypotension (MABP: 23 [20-24.9] mm Hg) compared with infants with normal blood pressure (MABP: 32.6 [27.5-35.7] mm Hg).

CONCLUSION

Despite having hypotension, ELBW infants (before treatment) had similar CBF velocity compared with control subjects with normal blood pressure. On the basis of these results, hypotension may not indicate decreased CBF.

Early systemic hypotension and vasopressor support in low birth weight infants: impact on neurodevelopment

BACKGROUND

The duration and severity of systemic hypotension have been related with altered neurodevelopment. Cerebral circulation is pressure-passive in low birth weight infants with early systemic hypotension who receive cardiovascular support. The treatment of early systemic hypotension is controversial, because it has been associated with short-term and long-term morbidity in retrospective studies. However, there has been no prospective information on cardiovascular support for hypotension and morbidity.

OBJECTIVE

Our goal for this prospective study was to evaluate the effect on neurodevelopment resulting from the use of vasopressors/inotropes for early systemic hypotension.

METHODS

Low birth weight infants with early systemic hypotension (<24 hours of life; study group) were assigned randomly to receive dopamine (2.5-10 microg/kg per minute) or epinephrine (0.125-0.5 microg/kg per minute) in progressively larger doses until target blood pressure was attained (treatment-success subgroup). Hemodynamically stable patients who did not receive cardiovascular support were the control group. Outcome measures were serial cranial ultrasound up to 40 weeks, structured neurologic evaluation (every 3 months), and neurodevelopmental test at 2 to 3 years of age.

RESULTS

One hundred thirty patients were included (study = 60; treatment success = 38; controls = 70). Study-group patients had lower birth weight, gestational age, and 5-minute Apgar score, higher rates of premature rupture of membranes, need for cardiorespiratory resuscitation at birth, and sickness shortly after birth than the control group. The patients in the study group also had significantly higher serum troponin I levels at birth. Initial cranial ultrasound findings did not differ between groups, but the final cranial ultrasounds revealed higher rates of severe periventricular hemorrhage in the study group and higher rates of normal cranial ultrasounds in the control group. Only the latter remained when the treatment-success subgroup and control group were compared. Multivariate analysis did not detect any association between final cranial ultrasounds and the use of vasopressors/inotropes. Sixteen infants died and 103 were followed up (90% survival rate). No differences between groups were found in the rates of abnormal neurologic status, developmental delay, or combined adverse outcome (death or cerebral palsy or severe neurodevelopmental delay).

CONCLUSIONS

Cautious use of cardiovascular support to treat early systemic hypotension in low birth weight infants seems to be safe. The question of whether raising systemic blood pressure to within a normal range will improve outcome should be examined by using appropriate study designs.

Definition of hypotension and assessment of hemodynamics in the preterm neonate

The complexity of postnatal cardiovascular transition has only recently been better appreciated in the very low birth weight neonate. As blood pressure in itself poorly represents systemic blood flow, especially when the fetal channels are open and the developmentally regulated vital organ assignment may not have been completed, efforts to measure systemic blood flow have resulted in a novel, yet incomplete, understanding of the principles and clinical relevance of cardiovascular adaptation during postnatal transition in this patient population. This article describes the definition of hypotension based on the principles of cardiovascular physiology, and reviews the tools available to the clinician and researcher at the bedside to examine the complex relationship among blood pressure, systemic and organ blood flow, and tissue oxygen delivery and oxygen demand in vital and non-vital organs in the very low birth weight neonate. Only after gaining an insight into these complex relationships and processes will we be able to design clinical trials of selected treatment modalities targeting relevant patient sub-populations for the management of neonatal cardiovascular compromise. Only clinical trials based on a solid understanding of developmental cardiovascular physiology tailored to the appropriate patient sub-population hold the promise of being effective and practical, and can lead to improvements in both hemodynamic parameters and clinically relevant outcome measures.

Epinephrine versus dopamine to treat shock in hypoxic newborn pigs resuscitated with 100% oxygen

Shock and tissue hypoperfusion are common after asphyxia. We compared systemic and regional hemodynamic effects of epinephrine and dopamine in the treatment of shock and hypotension in asphyxiated newborn piglets resuscitated with 100% oxygen. Twenty-four piglets (1-3 days old; weight, 1.4-2.6 kg) were acutely instrumented to measure cardiac index (CI), carotid, mesenteric and renal arterial blood flows, and mean systemic (SAPs) and pulmonary arterial pressures (PAPs). Piglets had normocapnic alveolar hypoxia (F(IO2)=0.08-0.10) for 50 min and reoxygenated with F(IO2)=1.0 for 1 h then F(IO2)=0.21 for 3.5 h. After 2 h reoxygenation, either dopamine (2 microg kg(-1) min(-1)) or epinephrine (0.2 microg kg(-1) min(-1)) was given for 30 min in a blinded randomized manner, which was then increased to maintain SAP (within 10% of baseline, pressure-driven dose) for 2 h. Hypoxia caused hypotension (SAP, 44%+/-3% of baseline), cardiogenic shock (CI, 41%+/-4%), and metabolic acidosis (mean pH, 7.04-7.09). Upon reoxygenation, hemodynamic parameters immediately recovered but gradually deteriorated during 2 h with SAP at 45+/-1 mmHg, CI at 74+/-9% of baseline, and pH 7.32+/-0.03. Low doses of either drug had no significant systemic and renal hemodynamic response. Epinephrine (0.3-1.5 microg kg(-1) min(-1)) for 2 h increased SAP and CI (with higher stroke volume) and decreased pulmonary vascular resistance (with reduced PAP-SAP ratio), whereas the responses with dopamine (10-25 microg kg(-1) min(-1)) were modest. Low-dose epinephrine improved mesenteric and carotid arterial flows, whereas the pressure-driven doses of epinephrine and dopamine increased carotid and mesenteric arterial flows, respectively. To treat shock in asphyxiated newborn piglets resuscitated with 100% oxygen, epinephrine exhibits an inotropic action compared with dopamine, whereas both catecholamines can increase carotid and mesenteric perfusion.

Systemic and regional hemodynamic effects of high-dose epinephrine infusion in hypoxic piglets resuscitated with 100% oxygen

Shock and poor regional perfusion are common in asphyxiated neonates. We compared the systemic and regional hemodynamic effects of high-dose epinephrine (E) with those of dopamine combined with low-dose epinephrine (DE) infusions in a neonatal model of hypoxia-reoxygenation. Neonatal piglets (1-3 days, 1.5-2.5 kg) were acutely instrumented to continuously monitor systemic arterial pressure (SAP), pulmonary artery pressure, cardiac index (CI), and blood flows at the left common carotid, superior mesenteric, and renal arteries. Either epinephrine (1 microg.kg(-1).min(-1)) or dopamine (10 microg.kg(-1).min(-1)) and epinephrine (0.2 microg.kg(-1).min(-1)) were given for 2 h in hypoxic piglets resuscitated with 100% oxygen (n = 8 per group) in a randomized blinded fashion. Control piglets received hypoxia and reoxygenation but no catecholamine infusion (n = 7). Alveolar hypoxia (PaO2, 33-37 mmHg) caused reduced CI (89-92 vs. 171-186 mL.kg(-1).min(-1) of baseline, P < 0.05), hypotension (SAP, 28-32 mmHg) with pH 7.05 to 7.10, and decreased regional flows. Upon reoxygenation, CI and SAP improved but gradually deteriorated to 131 to 136 mL.kg(-1).min(-1) and 41 to 49 mmHg at 2 h of reoxygenation, respectively. E and DE administration similarly improved CI (167 +/- 60 and 166 +/- 55 vs. 121 +/- 35 mL.kg(-1).min(-1) of controls) and SAP (53 +/- 7 and 56 +/- 10 vs. 39 +/- 8 mmHg of controls), respectively, and the pulmonary vascular resistance (vs. controls, all P < 0.05). Heart rate and pulmonary artery pressure were not different between groups. Systemic oxygen delivery and consumption were increased in E- and DE-treated groups with no difference in extraction ratio between groups. There were no differences in regional blood flows and oxygen delivery between groups. After hyperlactatemia with hypoxia, plasma lactate levels decreased with no difference between groups. Epinephrine given as the sole agent is as effective as dopamine and low-dose epinephrine combined in treating shock and hypotension that follow the resuscitation of hypoxic neonatal piglets, with no reduction in regional perfusion.

The effect of inotropes on morbidity and mortality in preterm infants with low systemic or organ blood flow

BACKGROUND

Low systemic blood flow (SBF) is common in extremely premature infants in the first day after birth and has been associated with peri / intraventricular haemorrhage (PIVH), necrotising enterocolitis (NEC), mortality and developmental impairment.

OBJECTIVES

To determine the effect of specific inotropes on morbidity and mortality in preterm infants with low systemic blood flow

SEARCH STRATEGY

Searches were made of The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2006 ), MEDLINE (1966 - April 2006), EMBASE (1980 - April 2006) and CINAHL (1982 - April 2006), supplemented by searches of abstracts of conference proceedings, citations of reviews and expert informants.

SELECTION CRITERIA

Random and quasi-random controlled trials of inotropes enrolling preterm infants with low systemic or organ blood flow in the neonatal period.

DATA COLLECTION AND ANALYSIS

Independent assessment of trial eligibility, quality and data extraction by each review author. Synthesis of data using relative risk (RR) and weighted mean difference (WMD) using standard methods of the Cochrane Collaboration.

MAIN RESULTS

No studies that compared an inotrope to no treatment in preterm infants with low SBF were found. One study (Osborn 2002a) was found that compared dobutamine versus dopamine. The study was of adequate methodology. It enrolled 42 infants < 30 weeks gestation and < 12 hours after birth with low SVC flow. The trial compared the effect of dobutamine versus dopamine titrated 10 to 20 mug/kg/min with the goal of increasing and maintaining SVC flow > 40 ml/kg/min. No significant difference was reported in mortality to discharge (RR 1.41, 95% CI 0.79, 2.52), PIVH (RR 1.01, 95% 0.52, 1.97), grade 3 or 4 PIVH (RR 0.39, 95% CI 0.12, 1.31) or NEC. At three years, there was no significant difference in cerebral palsy, deafness, Developmental quotient > 2 sd below norm or combined disability (RR 0.10, 95% CI 0.01, 1.56). Surviving infants treated with dobutamine had a significantly higher development quotient (MD 35.00, 95% CI 17.68, 52.32). There was no significant difference in death or disability at the latest time reported (RR 0.95, 95% CI 0.66, 1.38). For secondary outcomes, there was no significant difference in periventricular leucomalacia, renal impairment, pulmonary haemorrhage, retinopathy of prematurity or CLD at 36 weeks. There was no significant difference in treatment failure. Dobutamine produced a significantly greater increase in SVC flow at the highest dose reached (MD 13.10, 95% CI 2.87, 23.33), whereas dopamine produced a significantly greater increase in mean BP at 10 and 20 mug/kg/min and at the highest dose reached (MD -7.20, 95% CI -11.41, -2.99).

AUTHORS' CONCLUSIONS

In preterm infants with low systemic blood flow, there is some evidence that dobutamine is better than dopamine at increasing and maintaining systemic blood flow. The only eligible trial did not demonstrate any consistent differences in clinical outcomes. However, this study was not sufficiently powered to prove or disprove effects on clinical outcomes. It is unclear what is the most effective strategy for improving the cardiovascular status of immature infants in the first day. Further trials are needed to determine effective strategies for preventing and improving low systemic and organ blood flow.

Dopamine does not limit fetal cerebrovascular responses to hypoxia

Dopamine is used clinically to stabilize mean arterial blood pressure (MAP) in sick infants. One goal of this therapeutic intervention is to maintain adequate cerebral blood flow (CBF) and perfusion pressure. High-dose intravenous dopamine has been previously demonstrated to increase cerebrovascular resistance (CVR) in near-term fetal sheep. We hypothesized that this vascular response might limit cerebral vasodilatation during acute isocapnic hypoxia. We studied nine near-term chronically catheterized unanesthetized fetal sheep. Using radiolabeled microspheres to measure fetal CBF, we calculated CVR at baseline, during fetal hypoxia, and then with the addition of an intravenous dopamine infusion at 2.5, 7.5, and 25 μg·kg−1·min−1 while hypoxia continued. During acute isocapnic fetal hypoxia, CBF increased 73.0 ± 14.1% and CVR decreased 38.9 ± 4.9% from baseline. Dopamine infusion at 2.5 and 7.5 μg·kg−1·min−1, begun during hypoxia, did not alter CVR or MAP, but MAP increased when dopamine infusion was increased to 25 μg·kg−1·min−1. Dopamine did not alter CBF or affect the CBF response to hypoxia at any dose. However, CVR increased at a dopamine infusion rate of 25 μg·kg−1·min−1. This increase in CVR at the highest dopamine infusion rate is likely an autoregulatory response to the increase in MAP, similar to our previous findings. Therefore, in chronically catheterized unanesthetized near-term fetal sheep, dopamine does not alter the expected cerebrovascular responses to hypoxia.

Assessment and support of the preterm circulation

There are no clinical outcome data on which to base recommendations on how to assess and support the preterm circulation. Current standards are derived from an assumed proportionality between systemic and organ blood flow and mean blood pressure. Our study of central measures of systemic blood flow suggests preterm haemodynamics are more complex than this. Low systemic blood flow is common in the first 24 h after birth in very preterm babies and is not necessarily reflected by low blood pressure. The causes of this low systemic blood flow are complex but may relate to maladaptation to high extrauterine systemic (and sometimes pulmonary) vascular resistance. After day 1, hypotensive babies are more likely to have normal or high SBF reflecting vasodilatation. Empirically, inotropes that reduce afterload (such as dobutamine) may be more appropriate in the transitional period, while those with more vasoconstrictor actions (such as dopamine) may be more appropriate later on. Defining the haemodynamic in an individual baby needs both blood pressure and echocardiographic measures of systemic blood flow. Research in this area needs to move beyond just demonstrating changes in physiological variables to showing improvements in important clinical outcomes.

Systemic and Pulmonary Effects of Vasopressors and Inotropes in the Neonate

This paper briefly reviews the systemic and pulmonary hemodynamic actions of the most frequently used vasopressor-inotropes and inotropes in the preterm and term neonate. It is important to note that very little is known about the medium- and long-term cardiovascular and neurodevelopmental benefits of the use of these medications in the neonate.

Dopamine versus epinephrine for cardiovascular support in low birth weight infants: analysis of systemic effects and neonatal clinical outcomes

BACKGROUND

Early postnatal adaptation to transitional circulation in low birth weight infants frequently is associated with low blood pressure and decreased blood flow to organs. Catecholamines have been used widely as treatment, despite remarkably little empirical evidence on the effects of vasopressor/inotropic support on circulation and on clinically important outcomes in sick newborn infants.

AIMS

To explore the effectiveness of low/moderate-dose dopamine and epinephrine in the treatment of early systemic hypotension in low birth weight infants, evaluate the frequency of adverse drug effects, and examine neonatal clinical outcomes of patients in relation to treatment.

DESIGN/METHODS

Newborns of <1501-g birth weight or <32 weeks of gestational age, with a mean blood pressure lower than gestational age in the first 24 hours of life, were assigned randomly to receive dopamine (2.5, 5, 7.5, and 10 microg/kg per minute; n = 28) or epinephrine (0.125, 0.250, 0.375, and 0.5 microg/kg per minute; n = 32) at doses that were increased stepwise every 20 minutes until optimal mean blood pressure was attained and maintained (responders). If this treatment was unsuccessful (nonresponders), sequential rescue therapy was started, consisting first of the addition of the second study drug and then hydrocortisone.

OUTCOME MEASURES

These included: (1) short-term changes (first 96 hours, only responders) in heart rate, mean blood pressure, acid-base status, lactate, glycemia, urine output, and fluid-carbohydrate debit; and (2) medium-term morbidity, enteral nutrition tolerance, gastrointestinal complications, severity of lung disease, patent ductus arteriosus, cerebral ultrasound diagnoses, retinopathy of prematurity, and mortality.

RESULTS

Patients enrolled in this trial did not differ in birth weight or gestational age (1008 +/- 286 g and 28.3 +/- 2.3 weeks in the dopamine group; 944 +/- 281 g and 27.7 +/- 2.4 weeks in the epinephrine group). Other main antenatal variables were also comparable. However, responders and nonresponders differed significantly with respect to the need for cardiorespiratory resuscitation at birth (3% vs 23%), Critical Risk Index for Babies score (3.8 +/- 3 vs 7 +/- 5), and premature rupture of membranes >24 hours (39.5% vs 13.6%), respectively. No differences were found in the rate of treatment failure (dopamine: 36%; epinephrine: 37%) or need for rescue therapy according to treatment allocation. Groups did not differ in age at initiation of therapy (dopamine: 5.3 +/- 3.9 hours; epinephrine: 5.2 +/- 3.3 hours), but withdrawal was significantly later in the dopamine group. For short-term changes, mean blood pressure showed a significant increase from baseline throughout the first 96 hours with no differences between groups. However, epinephrine produced a greater increase in heart rate than dopamine. After treatment began, epinephrine patients showed higher plasma lactate (first 36 hours) and lower bicarbonate and base excess (first 6 hours) and received more bicarbonate. Patients in the epinephrine group also had higher glycemia (first 24 hours) and needed insulin therapy more often. Groups did not differ in urine output or fluid-carbohydrate supply during the first 96 hours. For medium-term morbidity, there were no differences in neonatal clinical outcomes in responders. However, significant differences were found in the incidence of patent ductus arteriosus, bronchopulmonary dysplasia, need for high-frequency ventilation, occurrence of necrotizing enterocolitis, and death between responders and nonresponders.

CONCLUSIONS

Low/moderate-dose epinephrine is as effective as low/moderate-dose dopamine for the treatment of hypotension in low birth weight infants, although it is associated with more transitory adverse effects.

Management of hypotension and low systemic blood flow in the very low birth weight neonate during the first postnatal week

Systemic hypotension during the first postnatal week is associated with increased mortality and morbidity in the very low birth weight (VLBW) neonate. Hypotension is generally defined as blood pressure below the fifth percentile of the gestational- and postnatal-age dependent blood pressure norms. Recent studies indicate that in most VLBW neonates, cerebral blood flow autoregulation is indeed lost when blood pressure reaches the fifth percentile. Treatment of the circulatory compromise should address the primary pathogenic factor(s) of the condition (hypovolemia, myocardial compromise, failure of vasoregulation or a combination of factors). Recent findings also suggest that vasopressor resistance can be treated with a brief course of low-dose hydrocortisone. However, due to the short- and potential long-term side effects of early hydrocortisone treatment, its use should be restricted to neonates with vasopressor-resistant hypotension. Finally, concomitant administration of hydrocortisone with indomethacin should be avoided due to the increased incidence of gastrointestinal perforations.

Which inotrope for which baby?

While we know a lot about blood pressure (BP) responses to various inotropes and a bit about systemic and organ blood flow responses, we know almost nothing about how different inotropes affect clinical outcomes. Low systemic blood flow (SBF) is common in the first 24 h after birth in very preterm babies (and more mature babies with severe respiratory problems) and is not always reflected by low BP. The causes of this low SBF are complex but may relate to maladaptation to high extrauterine systemic (and sometimes pulmonary) vascular resistance. After day 1, hypotensive babies are more likely to have normal or high SBF reflecting vasodilatation. Empirically, inotropes that reduce afterload (such as dobutamine) may be more appropriate in the transitional period, while those with more vasoconstrictor actions (such as dopamine) may be more appropriate later on. Defining the haemodynamic in an individual baby needs both BP and echocardiographic measures of SBF. Research in this area needs to move beyond just demonstrating changes in physiological variables to showing improvements in important clinical outcomes.

Cardiovascular drugs for the newborn

This article reviews the various cardiovascular drugs for newborns, including antiarrhythmics, antihypertensives, inotropes, and pulmonary vasodilators. Antiarrhythmic drugs are classified according to their mechanisms of action, such as effects on ion channels, duration of repolarization, and receptor interaction, which help with understanding the effects of individual antiarrhythmic drugs and selection of drugs for specific arrhythmias. Drug treatment for hypertension should start with a single drug from one of the following classes: ACE inhibitors, angiotensin-receptor antagonists, beta-receptor antagonists, calcium channel blockers, or diuretics. The inotropic drug should be selected according to its specific pharmacologic properties and the specific cardiovascular abnormality to be corrected. An effective pulmonary vasodilator must dilate the pulmonary vasculature more than the systemic vasculature.

Different Doses of Dopamine Have Heterogeneous Effects on Cerebral Hemodynamics and Dopamine Receptors in Young Rabbits as Measured with Near Infrared Spectroscopy

BACKGROUND

Fluctuations in cerebral blood volume and cerebral oxygenation may be important in the pathogenesis of intraventricular hemorrhage and hypoxic-ischemic brain injury in the neonate. The cerebral hemodynamic response to dopamine infusion in premature infants is not well established. The newborn rabbit, a rather immature species at birth, is a suitable model for monitoring the physiological changes of the cerebral circulation.

METHODS

The effect of dopamine upon cerebral hemodynamics and basal ganglia dopaminergic receptors were studied using four different dopamine doses.

RESULTS

No significant changes in near infrared spectroscopy (NIRS) parameters were observed in the animals that received 0.5 (n = 5) and 1 microg/kg/min (n = 4) of dopamine intravenously. In contrast, in those animals that received dopamine at 5 microg/kg/min (n = 7) and 50 microg/kg/min (n = 7), there was a significant decrease in oxygenated hemoglobin. Moreover, this was accompanied by a significant increase in deoxygenated hemoglobin soon after drug infusion. Cerebral blood volume was increased in the group that received 5 microg/kg/min, but significantly decreased in the group that received 50 microg/kg/min. In both groups NIRS parameters returned to baseline values soon after stopping dopamine infusion.

CONCLUSION

Despite evidence of a physiological response, we found no difference in the distribution of dopamine receptors between experimental and control animals. We therefore speculate that dopamine has an effect on the cerebrovasculature that could be mediated by factors other than changes in the basal ganglia dopamine receptors.

Cardiovascular support for low birth weight infants and cerebral hemodynamics: a randomized, blinded, clinical trial

BACKGROUND

Maintaining adequate organ blood flow is the target of vasopressor treatment, but the impact of these measures on cerebral perfusion has not yet been evaluated systematically in a randomized, blinded, clinical trial.

OBJECTIVES

To explore the effects on brain hemodynamics of 2 different inotropic agents used to treat systemic hypotension among low birth weight (LBW) infants.

DESIGN AND METHODS

Newborns of <1501 g birth weight or <32 weeks' gestational age, with a mean blood pressure (MBP) lower than gestational age in the first 24 hours of life, were assigned randomly to receive dopamine (DP) (2.5, 5, 7.5, or 10 microg/kg per minute; n = 28) or epinephrine (EP) (0.125, 0.250, 0.375, or 0.5 microg/kg per minute; n = 32), at doses that were increased in a stepwise manner every 20 minutes until the optimal MBP (MBP-OP) was attained and maintained.

OUTCOME MEASURES

Continuous monitoring of quantitative changes in cerebral concentrations of oxyhemoglobin and deoxyhemoglobin, cerebral intravascular oxygenation (HbD) (the difference between oxyhemoglobin and deoxyhemoglobin), and cerebral blood volume (CBV) were assessed with near-infrared spectroscopy. MBP, heart rate, transcutaneous Pco2 and Po2, and peripheral oxygen saturation were recorded continuously and analyzed at baseline, 20 minutes after each dose increase (T1, T2, T3, and T4) until MBP-OP was reached, and then every 20 minutes up to 1 hour of stable MBP-OP.

RESULTS

Fifty-nine infants were considered for analysis. Patients did not differ in birth weight or gestational age (1008 +/- 286 g and 28.3 +/- 2.3 weeks, respectively, in the DP group and 944 +/- 281 g and 27.7 +/- 2.4 weeks in the EP group). Studies were performed at a mean age of 5.3 +/- 3.7 hours of life (range: 2-16 hours). MBP-OP was attained for 96.3% of patients with DP and 93.7% with EP (responders). For those patients, MBP, heart rate, CBV, and HbD increased from baseline throughout the study period, with no differences between groups except for a higher heart rate with EP. Changes in MBP were correlated significantly with changes in HbD. Dose escalation of drugs produced no differences between groups in the behavior of the variables, except for a greater heart rate with EP from 20 minutes after dose 2 (T2) onward. Drug-induced changes in cerebral hemodynamics varied with gestational age; the EP-induced increase in CBV was greater among less mature patients (<28 weeks), whereas the DP-induced increase in CBV was greater among patients of > or =28 weeks.

CONCLUSIONS

Among hypotensive LBW infants, cardiovascular support with low/moderate-dose DP or low-dose EP increased cerebral perfusion, as indicated by the increase in both CBV and HbD. Low-dose EP was as effective as low/moderate-dose DP in increasing MBP among LBW infants.

Inotrope, lusitrope, and pressor use in neonates

Successful management of neonatal shock is driven by the etiology and pathophysiology of the cardiovascular compromise. In the clinical practice, however, we only have a limited ability to recognize the etiology of the condition (hypovolemia, myocardial dysfunction or abnormal vasoregulation). Therefore, management is based on administration of fluid boluses and vasoactive medications according to personal preference rather than to the underlying pathophysiology. In addition, although management strategies aimed at improving systemic blood pressure may have been associated with a decrease in mortality in critically ill neonates, there are no prospective data on the effect of these management strategies on morbidity, especially on long-term neurodevelopmental outcome. This paper briefly reviews some of the more frequently encountered clinical presentations of neonatal shock and describes the developmentally regulated cardiovascular responses to the pathophysiology-driven management strategies used in these clinical presentations in the critically ill preterm and term neonate.

Hypotensive extremely low birth weight infants have reduced cerebral blood flow

OBJECTIVES

Whether extremely low birth weight (ELBW) infants are at risk of cerebral hypoperfusion is uncertain because key issues concerning their cerebral blood flow (CBF) and mean arterial pressure (MAP) are unresolved: (1) whether CBF is pressure-passive or autoregulated; (2) the normal level of MAP; and (3) whether inotropic drugs used to increase MAP might inadvertently impair CBF. We addressed these issues in ELBW infants undergoing intensive care.

METHODS

CBF (measured by near-infrared spectroscopy) and MAP were measured in 17 infants aged 1.5 to 40.5 hours.

RESULTS

Five infants remained normotensive (MAP 37 +/- 2 mm Hg, [mean +/- SEM]); twelve became hypotensive (MAP 25 +/- 1 mm Hg) and were treated with dopamine (10-30 mug x kg(-1) per min). CBF of hypotensive infants (14 +/- 1 mL x 100 g(-1) per min) was lower than the CBF of normotensive infants (19 +/- mL x 100 g(-1) per min). After commencement of dopamine in hypotensive infants, MAP increased (29 +/- 1 mm Hg) and CBF also increased (18 +/- 1 mL x 100g(-1) per min). CBF was correlated with MAP in hypotensive infants before (R = 0.62) and during (R = 0.67) dopamine, but not in normotensive infants. A breakpoint was identified in the CBF versus MAP autoregulation curve of untreated infants at MAP = 29 mm Hg; no breakpoint was evident in dopamine-treated infants.

CONCLUSIONS

In ELBW infants (1) cerebral autoregulation is functional in normotensive but not hypotensive infants; (2) a breakpoint exists at approximately 30 mm Hg in the CBF-MAP autoregulation curve; and (3) dopamine improves both MAP and CBF.

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.

Dietary nucleotides and intestinal blood flow velocity in term infants

OBJECTIVES

Two previous studies have shown that the addition of nucleotides to single feedings of formula is associated with increased 90-minute postprandial superior mesenteric artery (SMA) blood flow velocity (BFV). To assess the effect of chronic feeding of nucleotide-supplemented formula, we measured pre- and postprandial SMA BFV in term infants fed formula with or without added nucleotides for 4 weeks.

METHODS

At 1 week of age, healthy, term infants were randomized to receive formula with added nucleotides (NT+), or formula without added nucleotides (NT-) from age 1 to 5 weeks. When the infants were 5 weeks of age, SMA BFV was measured by Doppler ultrasound 15 minutes before the assigned feeding (baseline) and 30, 60, and 90 minutes after the start of feeding. A reference group of human milk-fed infants was studied before and after breast feeding.

RESULTS

Thirty formula-fed (NT+ = 17; NT- = 13) and 10 human milk-fed infants were studied. Baseline BFV was similar among the three groups. BFV increased in each group from baseline to 30 minutes after initiation of feeding and progressively declined from 30 to 90 minutes in infants fed NT- formula or human milk. In infants fed NT+ formula, BFV decreased between 30 and 60 minutes. However, from 60 to 90 minutes, velocity was unchanged or increased. At 90 minutes, mean and peak systolic velocities were significantly greater in the NT+ group than the NT- group (P < 0.001).

CONCLUSIONS

These data agree with those of previous studies showing increased 90-minute postprandial SMA BFV after a feeding with nucleotide-supplemented formula. The clinical significance of these findings is unknown.

Cerebral fractional oxygen extraction in very low birth weight infants is high when there is low left ventricular output and hypocarbia but is unaffected by hypotension

This study examined the relationships between cerebral fractional oxygen extraction (FOE), mean arterial blood pressure (MABP), left ventricular output (LVO), blood gases, and other physiologic variables in 36 very-low-birth-weight preterm infants during the first 3 d after birth. There was a decrease in cerebral FOE (p = 0.008), and rises in LVO (p < 0.0001) and MABP (p = 0.02) during the 3 d. Between d 1 and 2, cerebral FOE decreased (p = 0.007) and LVO increased (p < 0.0001). There was no relationship between MABP and cerebral FOE. LVO correlated negatively with cerebral FOE on d 1 (p = 0.01), but not on d 2 (p = 0.07). On d 1, median pressure of arterial CO(2) was lower in infants with low LVO (<5(th) centile) and high cerebral FOE (>95(th) centile) than in infants with low LVO (<5(th) centile) but normal cerebral FOE (5(th)-95(th) centile) (p = 0.03). These findings suggest that cerebral FOE was increased only when LVO was low and there was hypocarbia. MABP had no demonstrable effect. It is likely that increased cerebral FOE is a normal physiologic response to maintain an adequate oxygen supply to the cerebral tissues when LVO is low and hypocarbia has caused vasoconstriction. It is possible that the cerebral hemispheres are low-priority vascular beds in the preterm infant, and that the high cerebral FOE is a result of reduced hemispheric blood flow to maintain MABP in the presence of low LVO.

Adrenaline for prevention of morbidity and mortality in preterm infants with cardiovascular compromise

BACKGROUND

Inotropes are widely used in preterm infants to treat cardiovascular compromise, which may result from early adaptive problems of the transitional circulation, perinatal asphyxia or sepsis. Sustained hypotension and poor organ blood flow are associated with brain injury including peri/intraventricular haemorrhage and subsequent poor neurodevelopmental outcomes. Adrenaline (epinephrine) infusions are used in preterm infants with clinical cardiovascular compromise.

OBJECTIVES

To determine the effectiveness and safety of adrenaline compared to no treatment or other inotropes in reducing mortality and morbidity in preterm infants with cardiovascular compromise.

SEARCH STRATEGY

Randomised controlled trials were identified by searching MEDLINE (1966-August 2003), The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2003) and EMBASE (1980 - 2003), supplemented with searches of reference lists of published trials and abstracts of conference proceedings.

SELECTION CRITERIA

Randomised controlled trials of preterm newborn infants that compared adrenaline to no treatment or other inotropic agents (including dopamine, dobutamine, noradrenaline or isoprenaline).

DATA COLLECTION AND ANALYSIS

Data were extracted and analysed independently by two reviewers. Treatment effects on the following outcomes were to be determined: mortality in the newborn period, long term neurodevelopmental outcomes, radiological evidence of brain injury, short term haemodynamic changes, adverse drug effects and short term neonatal outcomes. Study authors were contacted for additional information. Studies were analysed for methodological quality using the criteria of the Cochrane Neonatal Review Group.

MAIN RESULTS

One ongoing study (Pellicer 2003) was identified. One study comparing adrenaline with dopamine infusion was included but was published in abstract form only (Phillipos 1996). It enrolled hypotensive, predominantly preterm infants in the first 24 hours. Only infants >1750g are included in this review (report for infants <=1750g appears incomplete). The study was reported as being randomised and double blinded, but methods were not reported. Both adrenaline and dopamine significantly increased heart rate and mean BP, with no statistically significant effect on left or right ventricular outputs. No other clinical outcomes were reported. No studies were identified that compared adrenaline to other inotropes, placebo or no treatment.

REVIEWER'S CONCLUSIONS

There are insufficient data on the use of adrenaline infusions in preterm infants with cardiovascular compromise to make recommendations for practice. There is a need for larger trials to determine whether adrenaline is effective in reducing morbidity and mortality in preterm infants with cardiovascular compromise.

Treatment of hypotension in newborns

Systemic hypotension is a common complication of preterm birth affecting approximately one-third of very low-birthweight infants. There is considerable variation between neonatal units in the reported prevalence of hypotension, the threshold for therapeutic intervention and the nature of any cardiovascular support offered. Systemic hypotension is associated with adverse long-term neurodevelopmental outcome. The majority of preterm infants with hypotension have a normal or high left ventricular output, with low systemic vascular resistance often associated with a haemodynamically significant ductal shunt. Historically, volume expansion, dopamine and dobutamine have been the agents most commonly used to treat hypotension. Some hypotensive preterm infants have low cortisol levels, and corticosteroids are being used increasingly to prevent or treat hypotension in these babies.

Hypotension in the very low birthweight infant: the old, the new, and the uncertain

Hypotension occurs in up to 20% of very low birthweight infants, usually in the first 48 hours after birth. Its importance lies in its possible causal link with brain injury. Its management is controversial.