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

Effects of Catecholamines on Blood Flow in Preterm Infants: A Subanalysis of PICC-MBF Trial

INTRODUCTION

This study evaluated the correlation between skin blood flow and systemic blood flow and whether skin blood flow can determine the circulatory effects of dopamine and dobutamine on blood flow in very low birth weight (VLBW) infants.

METHODS

This study was a subanalysis of the PICC-MBF randomized controlled trial. The correlation between skin blood flow and echocardiographic findings was examined. Changes in skin blood flow and blood pressure before and after initiation or dose increase of dopamine and dobutamine were also evaluated.

RESULTS

Two hundred and thirty-four participants underwent echocardiography. Skin blood flow was significantly correlated with supra vena cava (SVC) flow (r = 0.31, p < 0.001). Receiver operator characteristic analysis revealed that skin blood flow <17 mL/min effectively detected SVC flow <41 mL/min (area under the curve = 0.83, p < 0.001). Dobutamine significantly increased skin blood flow after initiation or dose increase (p = 0.033) without increasing blood pressure. However, dopamine significantly increased both skin blood flow (p = 0.010) and blood pressure (p < 0.001).

CONCLUSIONS

Our findings indicated that skin blood flow could be used as a surrogate marker of systemic blood flow in VLBW infants and revealed differences in the effects of dopamine and dobutamine on circulation.

Randomized Trial of Perfusion-Based Circulatory Management in Infants of Very Low Birth Weight

OBJECTIVE

To establish the superiority of blood flow (BF)-based circulatory management over conventional blood pressure (BP)-based management strategies used for preventing intraventricular hemorrhage (IVH) in infants of very low birth weight (VLBW).

STUDY DESIGN

We conducted a nonblinded, single-centered randomized trial with the aim to prevent IVH by managing BF. Infants with VLBW were assigned randomly to a BF-based group or BP-based (BP group) circulatory management group. The incidence of IVH was the outcome of interest. The IVH also data were compared among healthy patients and patients responsive and unresponsive to the intervention.

RESULTS

A total of 219 and 220 infants with VLBW were assigned to the BF and BP groups, respectively. The IVH incidence rate was lower in the BF group, but the difference was not statistically significant (BF group, 6.8% vs BP group, 10.9%; P = .14). In 21% of patients of the BP group and 20% of the BF group, the intervention failed. In BF group, the IVH incidence rate was significantly greater in infants with unsuccessful intervention when compared with healthy individuals (6% vs 23%, P = .001). Multivariate logistic regression analysis revealed a correlation between low blood flow and IVH (aOR 3.24; 95% CI 1.49-7.08, P = .003) but not between low BP and IVH (P = .73).

CONCLUSIONS

The BF management protocol did not significantly decrease the incidence of IVH. However, after further optimization, we speculate the treatment strategy holds promise in decreasing the incidence of IVH. Trial registration UMIN-CTR: UMIN000013296.

Influence of sympathetic activity in the control of peripheral microvascular tone in preterm infants

BACKGROUND

Microvascular dysregulation following preterm birth is associated with increased illness severity and hypotension, particularly in males. Sympathetic nervous vascular regulation is evident in females. We hypothesized that sympathetic dysfunction in male preterm infants may contribute to a failure of peripheral microvascular vasoconstriction.

METHODS

Microvascular blood flow of infants 24-43 wk gestational age was assessed at 6, 24, and 72 h of age by laser Doppler. Blood flow Fourier transformed frequency distribution spectra (low frequency/high frequency ratio) were used to assess the influence of sympathetic tone on microvascular regulation. Total sympathetic output was assessed as urinary normetanephrine.

RESULTS

Microvascular sympathetic activity at 24 h postnatal age decreased in early preterm males, but not females. Peripheral sympathetic activity increased with advancing postnatal age in females, but decreased in males. In early preterm infants, total normetanephrine outputs increase significantly with postnatal age, in both sexes.

CONCLUSION

Sympathetic activation following preterm birth is sexually dimorphic, with preterm males having reduced sympathetic tone and reduced upregulation of sympathetic tone following birth. There is evidence of a disconnect between central sympathetic activity and local peripheral microcirculatory sympathetic drive. This may relate to autonomic nervous immaturity and highlights the need to understand how preterm birth may affect autonomic function.

Endogenous angiotensins and catecholamines do not reduce skin blood flow or prevent hypotension in preterm piglets

Endocrine control of cardiovascular function is probably immature in the preterm infant; thus, it may contribute to the relative ineffectiveness of current adrenergic treatments for preterm cardiovascular compromise. This study aimed to determine the cardiovascular and hormonal responses to stress in the preterm piglet. Piglets were delivered by cesarean section either preterm (97 of 115 days) or at term (113 days). An additional group of preterm piglets received maternal glucocorticoids as used clinically. Piglets were sedated and underwent hypoxia (4% FiO₂ for 20 min) to stimulate a cardiovascular response. Arterial blood pressure, skin blood flow, heart rate and plasma levels of epinephrine, norepinephrine, angiotensin II (Ang II), angiotensin‐(1–7) (Ang‐(1‐7)), and cortisol were measured. Term piglets responded to hypoxia with vasoconstriction; preterm piglets had a lesser response. Preterm piglets had lower blood pressures throughout, with a delayed blood pressure response to the hypoxic stress compared with term piglets. This immature response occurred despite similar high levels of circulating catecholamines, and higher levels of Ang II compared with term animals. Prenatal exposure to glucocorticoids increased the ratio of Ang‐(1‐7):Ang II. Preterm piglets, in contrast to term piglets, had no increase in cortisol levels in response to hypoxia. Preterm piglets have immature physiological responses to a hypoxic stress but no deficit of circulating catecholamines. Reduced vasoconstriction in preterm piglets could result from vasodilator actions of Ang II. In glucocorticoid exposed preterm piglets, further inhibition of vasoconstriction may occur because of an increased conversion of Ang II to Ang‐(1‐7).

This study aimed to determine if immature hormonal control of the cardiovascular system contributes to preterm cardiovascular compromise. Physiological and hormonal responses of preterm piglets to hypoxia are immature compared with term piglets. This is not due to a lack of endogenous catecholamines or angiotensin II, but may be due to the differences in cardiovascular actions of the renin–angiotensin system.

Peripheral blood flow monitoring in an infant with septic shock

Septic shock is associated with impaired vasoregulation, and treatment includes vasoactive drugs. Therefore, evaluation of vasoregulatory change is important. The present report describes the successful characterization of vasoregulatory change in response to a vasoactive drug during septic shock. A male infant born at 23 weeks' gestation developed septic shock. Severe hypotension developed, and treatment with colloid fluid and dopamine failed to increase blood pressure. With continuous measurement of skin blood flow using laser Doppler, noradrenaline was started. Based on changes in the blood flow, the dose was increased. At a dose of 1 μg/kg per min, skin blood flow in the foot decreased without any change in blood pressure. Subsequent blood transfusion succeeded in increasing both blood pressure and skin blood flow. It is concluded that decrease in foot blood flow reflects the vasoconstrictive effect of noradrenaline, although this finding must be validated in larger studies.

Early microvascular changes in the preterm neonate: a comparative study of the human and guinea pig

Dysfunction of the transition from fetal to neonatal circulatory systems may be a major contributor to poor outcome following preterm birth. Evidence exists in the human for both a period of low flow between 5 and 11 h and a later period of increased flow, suggesting a hypoperfusion–reperfusion cycle over the first 24 h following birth. Little is known about the regulation of peripheral blood flow during this time. The aim of this study was to conduct a comparative study between the human and guinea pig to characterize peripheral microvascular behavior during circulatory transition. Very preterm (≤28 weeks GA), preterm (29–36 weeks GA), and term (≥37 weeks GA) human neonates underwent laser Doppler analysis of skin microvascular blood flow at 6 and 24 h from birth. Guinea pig neonates were delivered prematurely (62 day GA) or at term (68–71 day GA) and laser Doppler analysis of skin microvascular blood flow was assessed every 2 h from birth. In human preterm neonates, there is a period of high microvascular flow at 24 h after birth. No period of low flow was observed at 6 h. In preterm animals, microvascular flow increased after birth, reaching a peak at 10 h postnatal age. Blood flow then steadily decreased, returning to delivery levels by 24 h. Preterm birth was associated with higher baseline microvascular flow throughout the study period in both human and guinea pig neonates. The findings do not support a hypoperfusion–reperfusion cycle in the microcirculation during circulatory transition. The guinea pig model of preterm birth will allow further investigation of the mechanisms underlying microvascular function and dysfunction during the initial extrauterine period.

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A period of high microvascular flow occurs after birth, however, no period of low flow (hypoperfusion stage) precedes this, suggesting that no hypoperfusion–reperfusion cycle exists during early extrauterine life. The data strongly support the use of the preterm guinea pig in future studies to allow further investigation of the interrelationship between cardiac output, preload, afterload, microvascular flow, and SVC flow. Elucidation of these processes may then aid clinicians in managing the circulatory dysfunction of preterm neonates, particularly those at greatest risk, preterm male neonates.

Evaluating the association of autonomic drug use to the development and severity of retinopathy of prematurity

PURPOSE

To explore the association of autonomic agents with the development and severity of retinopathy of prematurity (ROP).

METHODS

The medical records of all preterm infants screened for ROP were retrospective reviewed. The association between development and severity of ROP and the use and dose(s) of autonomic agents was analyzed, after adjustment for the covariates gestational age, weight, development of septicemia, intraventricular hemorrhage, and respiratory distress syndrome.

RESULTS

A total of 350 infants were screened. Caffeine was used in 338 infants; dopamine in 98 infants. There was a significant association between the use of dopamine and development of ROP (P < 0.001; relative risk [RR] = 1.6 [95% CI, 1.23-2.06]) and the need for ROP treatment (P = 0.001; RR = 4.63 [95% CI, 1.82-11.79]). The number of dopamine doses was significantly associated with the development of any ROP (P < 0.001; RR = 1.07 [95% CI, 1.03-1.1]), the severity of ROP (P < 0.001; RR = 1.09 [95% CI, 1.05-1.14]), and the need for treatment (P < 0.001; RR = 1.09 [95% CI, 1.05-1.14]). The total dose of caffeine was significantly associated with the development of any ROP (P = 0.003; RR = 1.03 [95% CI, 1.01-1.05]) and the need for treatment (P = 0.006, RR = 1.073 [95% CI; 1.021-1.13]).

CONCLUSIONS

Although a causal relationship was not identified, the use of the autonomic agents caffeine and dopamine was associated with the development and severity of retinopathy of prematurity in this cohort.

Skin blood flow as a predictor of intraventricular hemorrhage in very-low-birth-weight infants

BACKGROUND

Cardiovascular instability immediately after birth is associated with intraventricular hemorrhage (IVH) in very-low-birth-weight (VLBW) infants. For circulatory management, evaluation of organ blood flow is important. In this study, the relationship between peripheral perfusion within 48 h after birth and IVH was evaluated in VLBW infants.

METHODS

In this prospective observational study involving 83 VLBW infants, forehead blood flow (FBF) and lower-limb blood flow (LBF) were measured for 48 h after birth using a laser Doppler flowmeter. Blood flow was compared between infants with and without IVH. Multivariate logistic regression analysis was performed to identify the risk factors for IVH.

RESULTS

IVH developed in nine infants. In eight of these patients, IVH occurred after 24 h. LBF was lower in infants with IVH at 18 and 24 h and increased to the same level as that of infants without IVH at 48 h. Multivariate logistic regression analysis identified a correlation only between LBF and IVH at 18 h.

CONCLUSION

These findings were consistent with the hypoperfusion-reperfusion theory, which states that IVH develops after reperfusion subsequent to hypoperfusion. We speculate that measurement of skin blood flow in addition to systemic and cerebral circulation may be helpful in predicting IVH.