As you roll into your night shift, getting briefed and handed the urgent pager, you exit the briefing room and go into the hum of the neonatal intensive care unit. The familiar beeps of monitors and the soft cries of a premature infant fill the air, but then—a sharp, unusual beep cuts through.
Moments later, a nurse calls, “Doctor, could you check this blood pressure?”
Approaching the bedside, you discover a 24-week-old baby, now four weeks old, showing a MAP of just 24, down from the usual 38-42 range noted during the day.
You attempt to fetch the registrar for help, only to find they’re tied up in an emergency next door, leaving you to conduct the initial assessment alone… you can do this!
Let’s talk about hypotension.
Neonatal hypotension is generally defined based on blood pressure readings that fall below the 10th percentile for the neonate’s gestational age, postnatal age, and weight.
Clinically, it is associated with signs of poor perfusion, including prolonged capillary refill time, oliguria, and metabolic acidosis. I will also mention here that in most cases if you are dealing with hypotension, you should look for signs that were present before the episode of low blood pressure. Relying on the mean BP as the marker of haemodynamic compromise would exclude all other factors that can impact neonatal tissue perfusion and cellular metabolism.
Epidemiology in the United Kingdom
In the UK, the incidence of neonatal hypotension is notably high among very preterm infants, where it affects approximately 20-25% of this group.
Various studies, such as those pooling data from the National Neonatal Research Database, indicate that the incidence of hypotension varies based on neonatal age, with the highest rates observed immediately post-birth and within the first days of life.
Epidemiology in Australia
In Australia, the reported prevalence of neonatal hypotension in preterm infants is like that in the UK, with around 20-30% of very low birth weight infants experiencing significant hypotension during their initial hospital stay. Research and guidelines from Australian centres, like those published by the Australian and New Zealand Neonatal Network (ANZNN), emphasize early detection and management to improve outcomes.
Studies such as those by the ANZNN detail the risk factors and outcomes associated with neonatal hypotension, noting a strong correlation with adverse neurological outcomes and increased rates of mortality, particularly in the smallest and most premature infants.
Pathophysiology
I know we all tend to skip the pathophysiology bit when revising (or maybe it was just me) but bear with me, I promise it will make treating hypotension a little easier.
Neonatal hypotension can result from inadequate cardiac output, low systemic vascular resistance, or a combination of both, which are influenced by:
- Cardiac Output: Neonates, particularly preterm ones, may have compromised cardiac output due to myocardial immaturity, leading to reduced stroke volume and heart rate.
CO = SV x HR
SV is Stroke Volume (the amount of blood ejected with each heartbeat).
HR is heart rate (number of heartbeats per minute), but you know that already.
- Systemic Vascular Resistance (SVR): Neonatal immature autonomic regulation can lead to failures in vascular tone maintenance, resulting in low SVR.
- Blood Volume: Hypovolemia, whether due to inadequate placental transfusion at birth, haemorrhage, or sequestration of blood in the capillary bed, can precipitate hypotension.
- Neuroendocrine Regulation: The immature adrenal response can affect cortisol and catecholamine production, which are crucial for maintaining vascular tone and cardiac function.
There are formulas out there to understand the physiology behind hypotension in neonates. For ease, the one that helps me remember:
Blood pressure = CO x SVR
Causes of neonatal hypotension
- Prematurity: The most prevalent factor due to the underdevelopment of heart muscle, neuroendocrine system, and autonomic nervous control.
- Sepsis: This can induce widespread vasodilation and capillary leak, exacerbating hypotension. It is one of the leading causes of hypotension in the neonatal population admitted to our units or presenting in A&E.
- Perinatal Asphyxia: This leads to systemic hypoperfusion and myocardial dysfunction, significantly affecting blood pressure.
- Intraventricular Haemorrhage: Common in very low birth weight infants, leading to sudden drops in blood pressure.
- Medications: Certain drugs used in the NICU, like sedatives or analgesics, can lower blood pressure as a side effect.
- Congenital Heart Disease: Structural heart defects can directly impair cardiac output and effective circulation. This is one of the situations where you must not forget to feel for femoral pulses.
The other important moment to always think of the heart (sorry, cardiologists, I don’t think about the heart 24/7) is when a collapsed neonate presents to your emergency department, especially if blood pressure is present.
Diagnosis of Neonatal Hypotension
Blood Pressure Measurement
Neonatal blood pressure can be measured using either invasive or non-invasive methods.
Noninvasive methods typically involve oscillometric devices. These are easy to use and safe, and so they are the preferred method.
Invasive methods involve arterial lines. They provide continuous and accurate blood pressure readings but carry risks such as infection and arterial injury. However, most preterm infants in the first day of life have an umbilical artery catheter in situ, which can be used to monitor blood pressure.
Normal Blood Pressure Ranges
Blood pressure in neonates varies with gestational and postnatal age. Multiple charts and calculators are available online to help you determine whether your patient is hypotensive.
One of the quickest ways to assess hypotension is to compare it with the gestational age. The mean should be around the G). However, with BP having ranges, I would suggest doing a more in-depth assessment.
Clinical Assessment
Diagnosis of hypotension involves looking at the blood pressure reading and clinical signs. Think about:
- Skin perfusion: Prolonged capillary refill time (>2 seconds), cool extremities, and pale or mottled skin
- Decreased urine output (less than 1 mL/kg/hour)
- Poor muscle tone, lethargy, or a decreased level of consciousness (late signs)
- Echocardiography is useful for evaluating cardiac function, structural abnormalities, and cardiac output (you remember all the formulas above; this is when they become useful).
- Blood Tests: Can help identify underlying causes such as infection (sepsis), anaemia, or electrolyte imbalances.
However, if you take one thing from this, please let it be that the diagnosis of neonatal hypotension must considered in the context of the individual neonate’s clinical situation, including recent surgeries, their fluid status, and the presence of congenital conditions. Clinicians must balance the risks and benefits of diagnostic procedures, especially invasive ones, in this delicate population.
Treatment of Neonatal Hypotension
Treating neonatal hypotension requires a multilayered approach. It focuses on both the immediate restoration of adequate blood pressure and addressing underlying causes. Treatment typically involves fluid management, pharmacological interventions, and supportive care tailored to the individual neonate.
Some conditions need specific management that, if not identified earlier, can cause treatment-related complications. These include:-
In the First 24 Hours of Life
- Delayed Transition: Premature infants, especially those born before 32 weeks, may experience delayed transition from fetal to neonatal circulation. This can manifest as hypotension. However, if the infant is well-perfused, cardiovascularly stable, and showing no signs of organ dysfunction, active treatment may not be necessary. Observation and supportive care are often sufficient, as many of these infants stabilize independently as they adapt to extrauterine life.
- Meconium Aspiration Syndrome (MAS): MAS can lead to significant respiratory distress and, in severe cases, pulmonary hypertension, which in turn can cause hypotension. In these situations, it’s crucial to focus on treating the underlying respiratory issue—ensuring adequate oxygenation and ventilation and possibly using inhaled nitric oxide for pulmonary hypertension—rather than just addressing the low blood pressure. Effective management of MAS will often result in the stabilization of blood pressure.
- Hypothermia: Newborns, particularly preterm infants, are prone to hypothermia. This can lead to peripheral vasoconstriction and hypotension. Before considering fluid resuscitation or inotropes, it is essential to correct the infant’s body temperature. Using warmers, heated humidified gases, and ensuring proper environmental temperature can help resolve the hypotension. Warming the infant should always be the first step in managing cold-related hypotension.
- Perinatal Blood Loss: Significant blood loss during delivery, whether due to placental abruption, vasa previa, or traumatic delivery, can result in anaemia and subsequent hypotension. Check the haemoglobin and haematocrit levels early in these cases. If anaemia is confirmed, a blood transfusion may be necessary to restore adequate circulatory volume and improve oxygen-carrying capacity.
After 24 Hours of Life
- Congenital Adrenal Hyperplasia (CAH): Although rare, CAH can present with an adrenal crisis within the first few days of life. This condition often manifests as hypotension accompanied by hyponatremia and hyperkalaemia due to the lack of cortisol and aldosterone production. Check electrolytes and consider the diagnosis, especially if the infant shows signs of shock or has a family history suggestive of CAH. Early recognition and treatment with hydrocortisone and appropriate electrolyte management are crucial to prevent life-threatening complications.
- Sepsis: The risk of sepsis increases after the first 24 hours, particularly in preterm infants. Hypotension in the setting of sepsis may be one of the first signs of a systemic infection. Evaluate for other signs of sepsis, such as temperature instability, lethargy, feeding intolerance, and respiratory distress. Prompt initiation of antibiotics and supportive care, including fluids and possibly inotropes, is necessary to manage sepsis-related hypotension.
- Patent Ductus Arteriosus (PDA): In preterm infants, a hemodynamically significant PDA can lead to hypotension after the first 24 hours of life. The ductus arteriosus may remain open, leading to a left-to-right shunt, which can cause pulmonary over-circulation and systemic hypoperfusion. Management may include fluid restriction, diuretics, or pharmacologic closure with agents like indomethacin or ibuprofen. In some cases, surgical ligation may be required.
- Necrotising Enterocolitis (NEC): NEC typically presents after the first 24 hours of life and can cause systemic inflammation and sepsis, leading to hypotension. Early recognition and intervention are crucial.
Fluid Management
- Volume Expansion: Initial treatment often includes isotonic crystalloid solutions to correct hypovolemia. A typical starting dose is 10 mL/kg, which may be repeated based on response and clinical assessment.
- Blood Products: In cases of significant blood loss or severe anaemia, packed red blood cells may be administered to increase oxygen-carrying capacity and blood volume.
Supportive Care
- Mechanical Ventilation: Ensures adequate oxygenation and reduces the workload on the heart in neonates with respiratory distress or failure.
- Monitoring: Continuous monitoring of vital signs, urine output, and blood gases is critical to assess the effectiveness of the treatment and make necessary adjustments.
- Temperature Regulation: Maintaining normothermia helps reduce metabolic demands and stabilize cardiovascular function.
Inotropes
Dopamine
Dopamine is typically used for neonatal hypotension if you suspect low systemic vascular resistance. It improves cardiac contractility and renal blood flow. Contraindications include tachyarrhythmias and hypersensitivity to the drug. Caution is needed in neonates with pheochromocytoma due to the potential for excessive catecholamine release, not that you find that many neonates with pheochromocytoma.
Special Considerations: Dopamine’s effects are dose-dependent. Low doses (1-5 µg/kg/min) stimulate dopaminergic receptors, enhancing renal perfusion, while higher doses (5-20 µg/kg/min) stimulate beta-1 and alpha receptors, increasing cardiac output and systemic vascular resistance, respectively.
It is generally safe for short-term peripheral administration, but central access is preferred for prolonged use to minimise the risk of tissue necrosis.
Dobutamine
Dobutamine is indicated for hypotension primarily due to poor cardiac output with preserved blood pressure, as it effectively increases heart rate and myocardial contractility. It should be used cautiously in cases of idiopathic hypertrophic subaortic stenosis due to the risk of increasing outflow resistance.
Dobutamine is generally preferred when increasing cardiac output is more important than elevating systemic vascular resistance. It has minimal effects on heart rate and oxygen demand and is Safe to give peripherally (for a short time)
Adrenaline
Adrenaline is used in severe hypotension and cardiac arrest scenarios. It effectively stimulates alpha and beta-adrenergic receptors, enhancing myocardial contractility, heart rate, and vascular resistance. It is contraindicated in hypothermic patients and those with hyperthyroidism, as it may precipitate arrhythmias. Caution is necessary in patients with hypertension.
Due to its potent effects, adrenaline must be titrated carefully. Blood pressure, heart rate, and metabolic parameters must be continuously monitored to avoid complications. Low doses can be given peripherally; however, central administration is preferred.
Noradrenaline
Due to its potent vasoconstrictive effects, noradrenaline is indicated for severe hypotension and shock, particularly when it does not respond to other inotropes. However, it is contraindicated in patients with hypotensive shock with low cardiac output and in those with peripheral vascular thrombosis, as it may exacerbate these conditions.
It is primarily an alpha-adrenergic agonist with minimal beta-adrenergic activity. It should be used cautiously to avoid excessive vasoconstriction, which can reduce cardiac output and organ perfusion. Continuous cardiovascular monitoring is essential.
It must be administered centrally due to the risk of severe vasoconstriction, which can lead to, yep, you guessed it, tissue necrosis.
Vasopressin
Vasopressin is used in neonatal hypotension resistant to other vasopressors. It is particularly useful in septic shock and should be considered when vasoplegia (low systemic vascular resistance) does not respond adequately to catecholamines.
Use with caution in neonates with coronary artery disease or chronic nephropathy due to the risk of ischemia and reduced renal blood flow.
Vasopressin acts on vascular smooth muscle to induce vasoconstriction and is less likely to produce tachycardia. It is a powerful antidiuretic, so fluid balance, serum sodium, and osmolality must be monitored closely. It should be administered centrally. It is also important to note that there is a severe risk if extravasation occurs.
Milrinone
Milrinone is an inotrope that increases cardiac contractility and decreases pulmonary vascular resistance. It is mostly prescribed by cardiologists and in intensive care settings. It is useful in cases of myocardial dysfunction and low cardiac output, particularly when both inotropic support and afterload reduction are needed.
Continuous haemodynamic monitoring is necessary when administering milrinone. It requires central administration and is highly risky for extravasation.
Commonly Used Steroids
Hydrocortisone
The most common steroid for managing neonatal hypotension. It is preferred due to its minimal mineralocorticoid effects compared to other steroids. Its efficacy is related to its ability to make the body more sensitive to the actions of other inotropes administered.
Steroids are commonly used when you are adding a second inotrope to the management of hypertension, the proposed mechanisms of action include:
Enhancing Catecholamine Responsiveness: Steroids increase the synthesis of catecholamine receptors on blood vessels, which enhances the vasopressor effect of naturally occurring catecholamines and administered inotropes.
Stabilizing Cellular Membranes: Steroids stabilize cellular membranes and decrease capillary permeability, reducing the likelihood of oedema and improving circulatory volume.
Now, let’s go back to what you do with your little hypotensive friend that is hypotensive.
Step 1: Don’t Panic—Prioritise Assessment and Stabilization
- Take a deep breath. Remember, even when faced with the unknown, your first step is always to assess the ABCDE
- Quickly evaluate the baby’s overall status. Is this just a transient dip, or are there signs of poor perfusion? Your clinical assessment is as valuable as the monitor reading.
Step 2: Context is Key—Consider the Whole Picture
- Think about this baby’s journey so far. Prematurity at 24 weeks, now four weeks old, places them at risk for several complications. What’s changed since the last time they were stable?
- Look back at the trends. Have there been any recent interventions, like fluid changes or medications, that could have tipped the balance?
- Always check the blood pressure cuff. In the last week alone, I have fixed a sudden “drop” in blood pressure by replacing the cuff.
Step 3: Respond—But Remember Less Can Be More
- Start with the basics. If you suspect hypovolemia, a careful fluid bolus is reasonable. This does not mean that fluids fix everything, but sometimes they can help.
- You can carefully start an inotrope, but I would probably advise this to be done after discussion with someone, especially if you are not confident with starting inotropes normally.
Step 4: … and breath!!!
- Even when the registrar is tied up, you’ve got a whole team around you. Call on the nurses, ask for their insights, and keep everyone in the loop. This is about shared decision-making, and if it gets to the point where you have given the fluids with no response and you are wondering what the next steps will be, don’t forget that you can use your “call a friend” card and give the consultant a quick ring.
- After any stressful situation, don’t forget to debrief.
References for Further Reading
Australian and New Zealand Neonatal Network (ANZNN), Annual Reports on Neonatal Hypotension and Outcomes.
Smith, J. K., and Roberts, N. “Epidemiology of Hypotension in Neonates,” Journal of Perinatology, 2023.
Batton, B., Li, L., & Newman, N. S. (2023). “Diagnostic Approaches to Hypotension in Neonates,” Journal of Perinatal Medicine.
Kleinman, M. E., & de Caen, A. R. (2022). “Practical Aspects of Blood Pressure Management in Neonatal Intensive Care Units,” Pediatric Critical Care Medicine.
Davis, A. L., & Carcillo, J. A. (2024). “Comprehensive Review on the Diagnosis of Neonatal Hypotension,” Neonatology.
Sharma, V., & Berkelhamer, S. (2021). “Neonatal Hypotension: Bridging Pathophysiology and Treatment,” Neonatology Today.
Rios, D. R., & Bhattacharya, S. (2023). “Cardiovascular Physiology in Neonates: Implications for Hypotension Management,” Clinical Neonatology
Kleinman, M. E., & de Caen, A. R. (2023). “Management of Hypotension in Neonatal Intensive Care,” Journal of Perinatology.
Patel, A., & Fanaroff, J. M. (2022). “Pharmacologic Support in Neonates with Cardiovascular Insufficiency,” Neonatal Network.
El-Khuffash, A. F., & McNamara, P. J. (2017). “Hemodynamic assessment and monitoring of premature infants.” Clinics in Perinatology, 44(2), 377-393.
Fernandez, E. F., and Watterberg, K. L. (2022). “Role of Hydrocortisone in Treating Neonatal Hypotensive Shock,” Journal of Pediatrics and Neonatal Care.
