4 *MYTHS* about Newborn Blood Pressure!! And why they're WRONG!!

Summary

Dr. Tala, a neonatologist with 16 years of experience, discusses neonatal hypotension in a series of videos. She addresses common myths around blood pressure management in NICUs, focusing on the distinctions between vasopressors, inotropes, and chronotropic drugs. Dr. Tala emphasizes the importance of selecting the correct medication based on the underlying cause of low blood pressure, rather than using terms interchangeably. She also debunks the idea that blood pressure alone is a reliable indicator of neonatal oxygenation, advocating for a more comprehensive approach to evaluating and treating neonatal hypotension.

Takeaways

• 📉 Low blood pressure in neonates is not universally treated the same way across cases, and treatment should depend on the specific cause.
• 💊 Vasopressors and inotropes are different: vasopressors increase diastolic pressure by squeezing blood vessels, while inotropes enhance the heart's contractility, increasing systolic pressure.
• ⏱ Chronotropic drugs, such as epinephrine and dobutamine, increase the heart rate (chronotropy), while some drugs can have multiple effects depending on dosage.
• 👶 Neonatal blood pressure is a poor indicator of blood flow, especially within the first 24 hours of life; other markers like urine output, capillary refill, and lactic acid levels offer more insights.
• 🫀 Blood pressure is only a surrogate marker for blood flow and oxygenation. Even if blood pressure seems normal, there may still be insufficient blood flow to the body's tissues.
• 🧪 When assessing low blood flow, check for signs such as pale skin, delayed capillary refill, decreased urine output, and elevated lactic acid.
• 📏 The mean blood pressure, while commonly used, may not fully indicate adequate perfusion; assessing systolic and diastolic values can provide more clarity, especially in cases like PDA (Patent Ductus Arteriosus).
• 📊 Studies show only a weak correlation between low blood pressure treatment and improved neonatal outcomes, and not all cases of hypotension require intervention.
• 🧠 Treating low blood pressure alone doesn’t necessarily improve outcomes; it’s more effective to intervene when there are signs of inadequate oxygenation, such as high lactic acid levels.
• 📚 It’s critical to match the right medication to the cause of the hypotension—whether vasopressors or inotropes—rather than assuming a one-size-fits-all approach.

Q & A

What is considered a low blood pressure in neonates, and when should it be treated?

A low blood pressure in neonates varies depending on gestational age, clinical condition, and other factors. It is not defined by a single number but rather by a combination of clinical signs and measurements. Treatment should be considered if there are signs of poor perfusion, such as pallor, delayed capillary refill, low urine output, or increased lactate levels, rather than just based on blood pressure alone.

What is the difference between inotropes and vasopressors?

Inotropes are medications that increase the contractility of the heart, making it squeeze harder (e.g., epinephrine, dobutamine, milrinone). They generally increase systolic blood pressure. Vasopressors, on the other hand, work by constricting peripheral blood vessels, increasing diastolic blood pressure (e.g., norepinephrine, vasopressin, dopamine at higher doses). The two should not be used interchangeably as they have different effects.

Why is it important to choose the right medication for hypotension in neonates?

Choosing the right medication is crucial because different types of hypotension may require different treatments. For example, a baby with septic shock and dilated blood vessels may benefit more from a vasopressor to increase diastolic blood pressure, while a baby with poor heart contractility would need an inotrope to improve systolic blood pressure. Using the wrong medication could exacerbate the condition.

Why might mean blood pressure not be the best indicator of a neonate's overall status?

Mean blood pressure is just an average of systolic and diastolic pressures and does not give a complete picture of the baby’s perfusion status. A normal mean blood pressure can mask issues like a low systolic pressure, indicating poor cardiac output, or a low diastolic pressure, indicating peripheral vasodilation. It’s essential to consider systolic and diastolic pressures separately, along with other clinical signs.

What are some clinical signs that indicate poor perfusion in a neonate?

Signs of poor perfusion include pallor, delayed capillary refill (longer than 3-4 seconds), decreased urine output (less than 1 ml/kg/hr or a significant drop from the baseline), and increased lactate levels indicating anaerobic metabolism. These signs suggest that the blood is not reaching all the cells adequately.

What does a widened pulse pressure in a neonate indicate?

A widened pulse pressure, where the difference between systolic and diastolic pressures is large, could indicate conditions such as a patent ductus arteriosus (PDA). In this situation, there may be adequate left ventricular function, but significant blood shunting during diastole, leading to decreased blood flow to the rest of the body despite a seemingly normal mean blood pressure.

How should we interpret a narrow pulse pressure in a neonate?

A narrow pulse pressure, where systolic and diastolic pressures are close together, suggests that the heart is struggling to pump effectively against a higher afterload. This may indicate conditions like cardiac dysfunction or increased systemic vascular resistance, where the heart cannot generate sufficient cardiac output.

Does treating low blood pressure in neonates improve outcomes?

Treating low blood pressure based solely on the number may not necessarily improve outcomes. Studies have shown that there is a weak correlation between blood pressure and actual perfusion, especially in the first 24 hours. Treatment should be targeted based on signs of poor perfusion and oxygen delivery to tissues, such as high lactate levels, rather than just blood pressure alone.

What was the primary outcome of the HIP trial on treating low blood pressure in preterm infants?

The HIP trial found that infants treated with dopamine had slightly higher blood pressures, but there was no significant difference in the primary outcome of survival without severe brain injury compared to those who received a placebo. This suggests that treating low blood pressure with dopamine alone may not necessarily improve outcomes and highlights the need for individualized treatment approaches.

What are other indicators besides blood pressure that clinicians should consider when assessing neonatal perfusion and oxygenation status?

Clinicians should consider signs such as pallor, delayed capillary refill, decreased urine output, and increased lactate levels. These indicate poor perfusion and inadequate oxygen delivery to tissues. Additionally, monitoring for metabolic acidosis can provide clues about the baby’s oxygenation and perfusion status beyond just blood pressure readings.