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Preemie CV insufficiency

Courtesy of Jay P. Goldsmith, M.D., FAAP

Diagnosis of cardiac insufficiency in VLBW infants should consider multiple factors

February 28, 2022

About 50,000 infants weighing less than 1,500 grams (very low birth weight [VLBW]) were born in 2020, according to the National Vital Statistics System. As more VLBW infants survive, they represent a disproportionate percentage of children with developmental disabilities and cerebral palsy.

One major aspect of their clinical care is the evaluation of adequate perfusion to the brain and other organs.

 A new AAP clinical report provides an evidenced-based review of the diagnosis and treatment of cardiovascular insufficiency in the first three days of life in this vulnerable population. The report Recognition and Management of Cardiovascular Insufficiency in the Very Low Birth Weight Newborn, from the Committee on Fetus and Newborn and the National Association of Neonatal Nurses (NANN), is available at https://doi.org/10.1542/peds.2021-056051 and will be published in the March issue of Pediatrics.

The report updates a 2011 clinical guideline from the NANN, which was endorsed by the AAP.

Clinically challenging

Recognition and management of clinically significant systemic hypoperfusion in VLBW infants during the first few days of postnatal life are challenging. Indicators of cardiovascular insufficiency include hypotension, delayed capillary refill, oliguria and metabolic acidosis. The provider then must decide when to intervene and which therapies to use. Relying on blood pressure (BP) measures alone is a poor predictor of pathology.

Moreover, during the first few days of life, infants at the same gestational age and weight will have changing threshold BP values that potentially warrant intervention. High-level evidence does not support arbitrary numeric thresholds for treatment such as a mean arterial pressure (MAP) of 30 mm Hg or a MAP value 1-2 mm Hg less than the infant’s gestational age in weeks.

Valid BP values that reflect pathology in the VLBW neonate, either by invasive intra-arterial measurements or by cuff technology, may be problematic. Published values that reflect population “norms” do not necessarily correlate with abnormal end organ perfusion. However, the consequences of organ hypoperfusion are serious and include reduced delivery of oxygen and other nutrients, potentially leading to cell injury and/or death.

Multiple considerations required

When managing hypotension in the VLBW infant, providers should consider the physiologic consequences of the conversion from fetal to neonatal circulation and possible intracardiac shunting through the foramen ovale and ductus arteriosus. Additionally, when deciding how to manage possible cardiovascular insufficiency, they should consider how systemic hemodynamics influence cerebral hemodynamics.

All parameters of effective circulating blood volume should be considered before deciding on interventions. The report suggests a cautious, conservative approach based on known physiology in this population. However, knowledge gaps on transitional cardiovascular physiology and pathophysiology in VLBW infants make it difficult to establish specific treatment guidelines.

Recent clinical trials addressing this question have been unable to provide specific guidance on the management of neonatal hypotension in clinical practice. The Hypotension in Preterm Infants trial randomized neonates born less than 28 weeks’ gestation with mean BP less than gestational age in the first 72 hours of life to saline bolus/dopamine (treatment group) or 5% dextrose infusion only (restrictive management group). The study failed to demonstrate significant differences between the groups in clinical outcomes at 36 weeks’ postmenstrual age (Dempsey EM, et al. Arch Dis Child Fetal Neonatal Ed. 2021;106:398-403, https://fn.bmj.com/content/106/4/398).

Trials with relevant outcome measures are needed to establish reasonable BP values and treatment modes in this population.

Recommendations

At this time, the following recommendations can be made:

  • The measurement of BP in the VLBW population is not simple and may be erroneous. Treatment should not be based on a threshold BP value alone.
  • Multiple parameters can be used to diagnose cardiac insufficiency, including gestational age, weight and postnatal age using standardized tables that recognize values more than two standard deviations below the mean. Other factors can help guide therapy, including physical findings; clinical findings, such as poor urine output; laboratory studies, such as metabolic acidosis and increased lactate concentrations; and functional echocardiography.
  • The potential complications of treatments for hypotension should be considered.
  • Hypoperfusion states may be mitigated by delayed cord clamping, decreased blood sampling, appropriate ventilatory management (i.e., avoiding hypocarbia) and other attempts to avoid hypovolemia and maintain cardiac output.

Dr. Goldsmith is a lead author of the clinical report and former member of the Committee on Fetus and Newborn.

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