Diagnosis and treatment of preterm transitional circulatory compromise
Introduction
Many extremely preterm infants will suffer from periods of low systemic blood flow (SBF) in the first day of life with the high likelihood of end organ damage resulting in death or long term neurologic impairment. Many of these infants will not be detected in a timely manner by traditional measures of cardiovascular adequacy such as invasive blood pressure (BP) monitoring. Echocardiography and other measures of organ blood flow greatly facilitate the understanding of the pathophysiology of the preterm circulation whilst allowing early targeted treatment that is appropriate for the infant's circulatory state. Optimal management of infants with circulatory compromise in the first day of life requires an understanding of the pathophysiology of low SBF and hypotension, identifying infants at risk, understanding the limitations of bedside assessment, use of diagnostic techniques such as echocardiography and knowledge of the pharmacokinetics and pharmacodynamics of possible interventions. This review will focus on identifying infants at risk of circulatory compromise, the accuracy of bedside diagnosis of low SBF, use of echocardiography to measure SBF and organ blood flow in the first day of life, and evidence for treatment with emphasis on high level evidence from clinical trials and systemic reviews. The focus will be on the adaptation of the immature circulation to life and will take a problem based approach.
Section snippets
Risk factors for circulatory compromise
Low SBF is common in the first day of life occurring in approximately 1 / 3 of infants born < 30 weeks gestation and the majority of infants < 27 weeks [1], [2]. Of those infants who develop low SBF, around a third will do so by 3 h with nearly all developing low flows by 12 h of age. Many of these infants will initially have what on a population basis are considered to be normal blood pressures (i.e. they are in ‘compensated shock’). Our research has found that these low SBFs are associated with
Diagnosis of preterm circulatory compromise
There are various approaches that can be taken in managing cardiovascular compromise in the extremely preterm infant. There is no definitive evidence to date that one approach is better. Most clinicians diagnose cardiovascular compromise at the bedside measuring blood pressure (BP) supplemented by clinical signs of poor organ perfusion. Echocardiography is requested, not always performed in a timely manner, to confirm a symptomatic PDA or pulmonary hypertension and rule out structural heart
Treatment of preterm transitional circulatory compromise
Inotropes used in preterm infants have included dopamine, dobutamine, isoprenaline (isoproterenol), adrenaline (epinephrine), noradrenaline (norepinephrine) and milrinone. In selecting an inotrope for treatment in preterm infants, it is likely to be important to consider the underlying pathophysiology of the cardiovascular compromise as well as the pharmacokinetics and pharmacodynamics of the inotrope. Dopamine at low doses (2–10 μg/kg/min) stimulates dopamine and β-adrenergic receptors with
Summary-targeting treatments
Extremely preterm infants in the first day are at high risk of low SBF and subsequent organ injury. Low SBF is associated with high mean airway pressures, a large diameter PDA and high SVR. Knowledge of both BP and SBF is critical. Echocardiography allows for early targeted treatment of a large PDA, low SBF and assessment for pulmonary hypertension in the first hours. The underling cause of cardiovascular compromise should be sought from history and examination. Potentially reversible factors
Key guidelines
- 1.
Preterm infants are at high risk of low SBF in the first day of life, with almost all infants who develop low flows doing so within the first 12 h. Infants most at risk are born < 28 weeks gestation and ventilated with higher mean airway pressures. Echocardiography is required to detect infants with low SBF.
- 2.
In infants with low SBF, volume (normal saline 10–15 ml/kg) and dobutamine 10–20 μg/kg/min increases flow better than dopamine.
- 3.
High risk infants should be monitored using an umbilical or
Research directions
- 1.
In managing the ductus arteriosus, trials of early treatment with indomethacin or ibuprofen targeted at infants with a large diameter PDA on echocardiography are needed. Trials should assess the effects of ductal closure on systemic and organ blood flows in the first day and be adequately powered to assess clinical and long term outcomes.
- 2.
Different strategies for managing the cardiovascular status of extremely preterm infants are required. Two such strategies include targeting treatment of
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