CRDIOVASCULAR SEQUENCE. B.Basiri Associated professor of neonatology Hamadan University of Medical Science

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Associated professor of neonatology Hamadan University of Medical



Educational objectives

• Upon completion of this chapter, you will be able to:

• • Identify infants who require cardiovascular stabilization.

• • Apply the Acute Care of at-Risk Newborns (ACoRN) Cardiovascular Sequence.

• • Assess adequacy of circulation and end-organ perfusion.

• • Recognize and manage circulatory shock.

• • Recognize and manage cyanosis.

• • Know how to perform and interpret a critical congenital heart disease (CCHD) screen.

• • Recognize and manage supraventricular tachycardia (SVT).

• • Recognize when to exit the Cardiovascular Sequence to other

ACoRN sequences


Key concepts

• 1. Shock, cyanosis unresponsive to oxygen, and tachycardia all indicate cardiovascular instability.

• 2. Initially, infants with underlying congenital heart disease (CHD) can appear well.

• 3. Routine screening for CCHD identifies infants who require assessment to rule out severe or cyanotic CHD.

• 4. The underlying cause of shock can be difficult to ascertain at

presentation, but all causes are characterized by underperfusion of vital organs. Always consider volume expansion while establishing a diagnosis.

• 5. Cardiovascular instability and shock may be the initial presentation of sepsis. These infants should be treated with antibiotics as soon as possible after stabilizing the systems identified by the ACoRN Primary Survey.

• 6. Cyanosis and shock may both be present with duct-dependent CHD.

• 7. Prostaglandin E1 (PGE1) is the life-saving treatment in duct-dependent CHD.

• 8. Consider SVT when an infant’s heart rate (HR) is more than 220 bpm.



• • Clinical assessment of circulation

• • Appropriate administration of cardiovascular medications

• • Performing a hyperoxia test

• • CCHD screening


The key function of the cardiovascular system

• is to deliver oxygen to the tissues

• . • Oxygen delivery depends on the oxygen content of blood and the cardiac output.

• • The oxygen content of blood depends on hemoglobin concentration and the oxygen saturation (SO2) of hemoglobin.

• • Cardiac output depends on stroke volume (the

volume ejected by each cardiac contraction) and HR.

• Stroke volume depends on preload (filling), cardiac contractility, and afterload (vascular resistance

affecting the ability of the heart to pump blood



• Decreased oxygen delivery to the tissues due to respiratory causes is addressed in the ACoRN Respiratory Sequence.

• Decreased oxygen delivery to the tissues in the ACoRN Cardiovascular Sequence is caused by one or more of the following mechanisms:

• • Insufficient circulating blood volume or oxygen- carrying capacity (anemia).

• • Poor heart muscle function (myocardial dysfunction).

• • Anatomical abnormalities of the heart and great vessels (cyanotic and acyanotic CHD).

• • Abnormal heart rhythms (tachyarrhythmia or



Alerting Signs

• Alerting Signs An infant showing one or more of the following Alerting Signs enters the ACoRN Cardiovascular Sequence:

• Pale, mottled, grey*

• Weak pulses or low blood pressure*

• Cyanosis unresponsive to O2

• Failed CCHD screen

• Heart rate > 220 bpm


• Being pale, mottled, or grey is a critically important sign because it indicates inadequate end-organ perfusion and serious circulatory instability. For such infants, assume shock or impending shock.

• Weak pulses are also important, particularly when the femoral or peripheral pulses are difficult to palpate.

• Low blood pressure (BP) can be a sign of low vascular tone, volume, or decreased cardiac output. This Alerting Sign must be interpreted and addressed with caution.

Ten percent of normal, stable infants have a mean BP

below the 10th percentile. Conversely, infants can have

normal BP despite low cardiac output. Blood pressure

must be interpreted in context with other indicators of

end-organ perfusion


• Cyanosis that is unresponsive to oxygen identifies infants with clinical cyanosis or hemoglobin desaturation

despite the administration of 100% oxygen. This is an important sign of congenital cyanotic heart disease, especially when it occurs in the absence of respiratory distress. Cyanosis only becomes readily apparent when desaturated hemoglobin levels reach 50 g/L. Therefore, the infant with a hemoglobin of 200 g/L would only

appear cyanosed when SpO2 levels dropped below 75%,

and the infant with a hemoglobin of 150 g/L would not

be visibly cyanosed until SpO2 dropped to 67%. When

significant anemia is present, hypoxemic neonates may

appear pale rather than cyanosed.


• Suspicion of cyanosis requires confirmation by pulse oximetry. Assessing skin colour is

challenging and made more difficult by factors

such as lighting, temperature, and infant skin

tone. Appearing ‘dusky’ or ‘not pink’ are key

signs of central cyanosis but can be missed.


CCHD screen

• A CCHD screen should be performed for all term and late preterm newborns at 24 to 36 h of age.

A failed CCHD screen requires prompt investigation.

A failed screen occurs when the SpO2 in an infant’s

right hand or either foot is less than 90% on a single

reading. The infant also fails when SpO2 is between

90% and 94% in the right hand and foot, OR when

the difference between the right hand and foot is

more than 3% on 3 separate readings taken 1 h

apart. Early diagnosis of CCHD is crucial because

delays in detection and management increase risk

for morbidity and mortality


• Routine screening with pulse oximetry is safe,

noninvasive, easy to perform, and widely available.

It has been shown to enhance detection of CCHD, with a reported specificity of 99.9% and a

moderately high sensitivity (76.5%).

• CCHD screening is performed by placing one pulse oximeter probe on the right hand and one on either foot and recording the readings.

• The results of screening are reported using the

algorithm shown in the following figure. The

screening test is declared a ‘pass’ or a ‘fail’.


• When an infant’s HR is greater than 220 bpm, the ACoRN provider should consider

tachyarrhythmia. Infants who are distressed can have HRs of 160 bpm to 200 bpm (sinus

tachycardia), but rarely have HRs over 220 bpm.

SVT should be suspected when HR is greater than 220 bpm with lack of variability, in

episodes that start and stop suddenly


Core Steps

• The essential Core Step in the ACoRN

Cardiovascular Sequence is to assess the presence and degree of cardiovascular

instability, using Table 4.1: Clinical Assessment

of Circulation


Tone, activity, and alertness

• Abnormal tone, activity, and level of alertness are critical signs of inadequate cerebral

perfusion in the ACoRN Cardiovascular

Sequence. Conversely, having normal tone,

being active and alert, and looking well indicate adequate cerebral perfusion. Altered levels of tone, activity, and alertness, as signs of

cardiovascular instability, may be confounded by

co-morbid conditions such as neurologic injury

or infection


Critical perfusion

• Being pale, mottled, or grey are critical signs of inadequate end-organ perfusion. Being pale but well perfused is not a sign of circulatory




• Assessing pulses is an acquired skill. ACoRN

providers should routinely palpate brachial and femoral pulses in healthy infants to become

familiar with their characteristics, and regularly compare upper and lower limb pulses.

• When a diminished femoral pulse is found, confirmation (by a second individual or a

repeated attempt) is strongly recommended.


Blood pressure

• Considered alongside mean BP, the systolic BP provides information on the contractility of the

heart and the output of the left ventricle. A drop in systolic BP indicates reduced stroke volume due to altered left ventricular preload, contractility, or


• The diastolic BP provides information on the resting pressure of blood against vessel walls. A drop in

diastolic BP indicates decreasing vascular resistance or blood volume. Diastolic hypotension is a common cause of low mean BP in preterm infants. In

otherwise well infants, treatment should not be

guided by BP measurement alone


Capillary refill time Capillary refill time

• (CRT) is measured by pressing the skin of the infant’s sternum and foot or hand for 5 sec, then counting the seconds it takes for the skin to refill with capillary blood. The normal CRT is less than 3 sec in both central and peripheral locations. Record the CRT in seconds (e.g., ‘4 sec’ or ‘less than 2 sec’) rather than using terms such as ‘prolonged’.

• While a CRT of greater than 3 to 4 sec is a reliable sign of circulatory deterioration, a normal CRT test should not, by itself, be relied upon to rule out

serious illness.


Skin temperature

• Warm skin, including feet and hands, suggests good skin perfusion. Cool feet and hands

compared with a warm trunk may be a sign of low peripheral perfusion. This indicator can be masked when newborns are cared for on a

radiant warmer. Cool feet and hands and

peripheral cyanosis (acrocyanosis) are common during transition and can be caused by sluggish peripheral circulation, peripheral vasomotor

instability, or cold stress.


Heart rate

• The normal HR in term newborns is between

100 bpm and 140 bpm. In premature newborns, HR is normally between 120 bpm and 160 bpm.

Heart rate can be impacted by medications,

pain, agitation, and temperature. An HR that is persistently greater than 180 bpm should be

investigated. A lower resting HR (80–100 bpm) in the sleeping term infant is common in the first few days postbirth and is not by itself



Urine output

• Normal urine production depends on adequate

blood perfusion to the kidneys. Low urine output

can be a sign of insufficient circulation but only

after 24 h of age, as many infants do not void in

the first 12 to 24 h.


Organization of Care

• Care in the ACoRN Cardiovascular Sequence is organized based on whether the infant has:

• • Shock,

• • Circulatory instability without shock,

• • Cyanosis unresponsive to O2,

• • A failed CCHD screen, or

• • A HR greater than 220 bpm.



• Infants are identified by the Clinical Assessment of Circulation as having shock when abnormal

neurologic signs (decreased tone, activity, or

alertness) are present in the context of low perfusion (pale, mottled, or grey). These signs of shock may

also co-exist in infants presenting with severe cyanosis or tachycardia.

• An infant with signs of shock is critically ill by definition, and the management of shock is a medical emergency.

• When shock is suspected, immediate supportive

measures must be instituted, regardless of cause.


Circulatory instability without shock

• These infants are identified by the Clinical

Assessment of Circulation Table as having weak pulses, low BP, prolonged CRTs, cool

extremities, or a HR greater than 180 bpm, but without having altered neurologic status. In

infants older than 24 h, urine output may be less than 1 mL/kg/h. Infants who have signs of

circulatory instability may become critically ill

and need ongoing monitoring and support.


Cyanosis unresponsive to O2

• A low SpO2 or arterial PO2 is needed to confirm the presence and degree of central cyanosis.

With significant arterial desaturation, oxygen delivery to the tissues is compromised and

metabolic acidosis develops. Table 4.2 shows

how different levels of SpO2 are tolerated.


Failed CCHD screen

• Newborns who fail their CCHD screen may be clinically stable, have cyanosis outside the visual threshold, and may or may not show other signs of circulatory instability. These infants may

become critically ill and need urgent assessment


Heart rate greater than 220 bpm

• An infant with a HR greater than 220 bpm at rest is suspected to have SVT. Most inpatient

newborns with new onset SVT can tolerate a HR of up to 250 bpm for several hours, allowing

time for consultation before initiating medical treatment. Without treatment, a sustained

tachyarrhythmia eventually progresses to heart failure. Outpatient infants with SVT generally have signs of decompensation at time of

presentation to hospital.


Next Steps

• Next Steps in the ACoRN Cardiovascular Sequence are to obtain a

• focused history,

• conduct a physical exam,

• order diagnostic tests,

• establish a working diagnosis,

• and obtain an urgent consultation (if not

already done).


Focused history

• Essential information to gather during a focused cardiovascular history includes the following:


• Intrapartum

• Neonatal


Focused physical examination

• In addition to the examination conducted during the ACoRN Primary Survey, a focused cardiovascular examination should include the following:

• Observation

• • Colour

• • Level of alertness and activity

• • Resting posture and tone

• • Respiratory effort and rate (e.g., increased due to pulmonary congestion)

• • Dysmorphic features suggestive of chromosomal abnormalities (trisomy 21, 13, or 18), or genetic

syndromes. Genetic abnormalities significantly increase

the risk for CHD.



• • Check 4-limb BPs. It is normal for the BP to be slightly higher in the legs than the arms. Systolic BPs that are greater than 10 mm to 15 mm higher in the right arm compared with the left arm or legs is abnormal and may indicate coarctation of the aorta. • Check for peripheral edema.

• • Compare temperature of the infant’s feet and hands with temperature over the trunk.

• • Compare pulses palpated in the upper and lower extremities.

• • Palpate for an active precordium or high cardiac

impulse over the sternum (right ventricle) or apex (left

ventricle), which suggests CHD


• • Auscultate for abnormal heart sounds and

murmurs, keeping these considerations in mind: ◦ Soft murmurs at the apex or over the large vessels are common in well term newborns. ◦ A murmur can be transitional or a sign of cardiac disease. ◦ Severe CHD can exist without a murmur. ◦ A ‘galloping’

rhythm can indicate heart failure.

• • Check for hepatomegaly (i.e., the infant’s liver is palpable 3 cm or more below the right costal

margin). ◦ In lung disease with hyperinflation, the liver may be displaced downward. ◦ In cardiac

disease, hepatomegaly can indicate heart failure.


Diagnostic tests

• • Chest radiograph,

• blood gas,

• and complete blood count and differential







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