SILVERMAN-ANDERSON ASSESSMENT: WHAT IT IS FOR, CRITERIA, INTERPRETATION - MEDICINE - 2025

The Silverman-Anderson assessment, also known as the Silverman Scale, is a method of objective assessment of work of breathing in newborns.

Newborn respiratory distress is among the main causes of postpartum mortality, as well as admission to the neonatal intensive care unit, an early diagnosis being essential in order to establish the necessary therapeutic measures to avoid these problems.

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The Silverman-Anderson assessment is based on the objective evaluation of 5 easily quantifiable clinical parameters during the physical examination, which allow determining with certainty not only the presence but also the severity of respiratory distress in the newborn.

By means of this assessment, quick and accurate decisions can be made about the start of ventilatory support in neonates, thus reducing the rates of complications and improving the prognosis of those babies who present respiratory distress during the first hours of their life.

What is the Silverman-Anderson valuation for?

The transition from intrauterine to extrauterine life represents an extreme change during which the fetus (now baby) stops receiving oxygen through the umbilical cord, and must begin to extract it directly from the air it breathes.

Although it seems automatic and is taken for granted, the truth is that during the first hours of life the newborn's lung must begin to work efficiently. Otherwise, it does not take long before some respiratory distress occurs, and with it the decrease in the concentration of oxygen in the blood.

Because the complications associated with respiratory distress are very severe, it is essential to use a method that allows them to be identified early. In this way, corrective and support measures can be implemented as soon as possible, thus reducing the risk of complications and improving the patient's prognosis.

And it is precisely for this that the Silverman-Anderson Assessment serves, which evaluates a series of five clinical parameters in a very agile and fast way. This makes it possible to determine in less than 1 minute not only if a neonate has respiratory distress, but also allows the severity of it to be rated when it is present.

Although there are biochemical and gasometric parameters that could be used for the diagnosis of respiratory distress in the newborn, the truth is that all of them are invasive and take much longer than that used to calculate the Silverman index.

For this reason, with more than 50 years in use, today it is still the most widely used scale in the field of medicine to evaluate the respiratory work of the newborn.

Criteria evaluated

The ease and speed with which the Silverman-Anderson assessment is carried out is based on the fact that it measures 5 easily evaluable clinical parameters, assigning each one a score ranging from 0 (clinical sign absent) to 2 (clinical sign present unequivocally).

During a well-structured clinical examination, all variables to be assessed within the Silverman-Anderson assessment are examined in less than 30 seconds. As they are evaluated, they are assigned a score to obtain the final result in less than 1 minute.

The lower the result, the better the condition of the newborn's respiratory function and therefore its prognosis. The clinical parameters to be evaluated are the following: thoracic-abdominal movements, intercostal pulling, xiphoid retraction, nasal flutter, and expiratory grunting.

Thoracic - abdominal movements

This variable refers to the expansion of the thorax on inspiration and its retraction on expiration, which under normal conditions must be accompanied by an expansion of the abdomen during inspiration and its depression in the expiratory phase.

The normal thing is that the movement is presented as just described, in a rhythmic and harmonic way. When this happens, this variable is assigned a score of 0.

When the chest remains immobile and there are only abdominal movements, a score of 1 (abdominal breathing) is assigned. On the other hand, when the thoracic - abdominal movements are not harmonious and coherent (that is, the thorax expands while the abdomen contracts and vice versa), a score of 2 is assigned. This is known as thoracic - abdominal dissociation.

Intercostal pull

The formation of folds between the ribs during inspiration is known as intercostal pulling. The presence of these folds is due to the contraction of the intercostal muscles to aid in breathing, so that the skin "wrinkles" due to the contraction of the underlying muscle.

Under normal conditions, the intercostal muscles should not be used to breathe, therefore the draw does not exist. When this occurs, a score of 0 is assigned to this variable.

In cases of respiratory distress, the intercostal muscles begin to function as auxiliaries to the diaphragm, and therefore the presence of intercostal pulling begins to be evident.

When respiratory distress is mild, the intercostal pull is barely visible although it is present. In these cases a score of 1 is assigned.

In cases of severe respiratory distress, the intercostal draw is not only present but is also very marked and easy to detect, assigning in these cases a value of 2 points.

Xiphoid retraction

The xiphoid is the lowest end of the sternum, the bone located in the center of the chest. Under normal conditions this bone structure does not have any movement, or if it does, it is imperceptible.

However, when the muscles of breathing make a significant effort or are not properly coordinated, the xiphoid process begins to show visible movements. When these are barely detectable, they are assigned a value of 1.

On the contrary, when the xiphoid appendix presents a marked, marked and constant movement due to the energetic contraction of the respiratory muscles (which have part of their tendon attachments in this bone structure), it is assigned a value of 2 points.

Nasal flaring

The nostrils are the structures through which air passes into the lungs. Under normal conditions, its diameter is appropriate to allow the entry of enough air to breathe.

However, in cases of respiratory distress, not enough air reaches the lungs; And in an attempt to change that, the nostrils tend to open during inspiration, producing the phenomenon known as nasal flapping.

If there is no respiratory distress, there should be no nasal flutter (a value of 0 is assigned), while in cases where the newborn is breathing with difficulty, it can be seen how the wings of the nose begin to move with each inspiration (value 1). They can even have a marked expansion-contraction movement with each respiratory cycle, assigning in this case a value of 2.

Expiratory groan

This is a characteristic sound that air produces when it is expelled through a narrow airway. In normal conditions, it should not appear (score 0), establishing progressively as respiratory distress progresses.

At first, the expiratory grumble is detectable only during auscultation (score of 1), whereas in the most severe cases of respiratory distress it is audible without any device (score of 2).

Interpretation

Once the five clinical parameters have been evaluated, the score assigned to each of them must be added and the value obtained must be located in a table. The lower the number, the less severe the respiratory distress and the better the prognosis.

The interpretation is very simple:

- 0 Points = No respiratory distress

- 1 to 3 points = Mild respiratory distress

- 4 to 6 points = Moderate respiratory distress

- 7 to 10 points = Severe respiratory distress

Depending on the severity of each case, the best therapeutic option for each newborn will be decided. These can range from oxygen supplementation therapy to intubation and mechanical ventilation, to different options for respiratory support.

Who invented it

As its name suggests, the Silverman-Anderson test was created by Dr. William Silverman. This doctor, born in Cleveland Ohio, grew up in Los Angeles (California), where he graduated as a doctor from the University of California in the city of San Francisco.

In the 1940s he became a pioneer in neonatology, an area in which he worked throughout his life and in which he left a wide legacy, especially in the management of premature babies.

A man of lights and prominent scientist, Dr. Silverman served as director of the neonatology unit at Columbia Presbyterian Hospital (known today as Morgan Stanley Children's Hospital), and later was the chief of the neonatal intensive care unit at the San Francisco Children's Hospital.

His work is extensive and prolific; and even today many of the concepts developed by Dr. Silverman in the second half of the twentieth century are still in full force, being referred to daily in the practice of medicine.

References

1. Silverman WA, Andersen DA. (1956) A controlled clinical trial of effects of water mist on obstructive respiratory signs, death rate and necropsy findings among premature infants. Pediatrics; 17 (1): 1–10.
2. Mathai, SS, Raju, U., & Kanitkar, M. (2007). Management of respiratory distress in the newborn. Medical journal, Armed Forces India, 63 (3), 269.
3. Hedstrom, AB, Gove, NE, Mayock, DE, & Batra, M. (2018). Performance of the Silverman Andersen Respiratory Severity Score in predicting PCO 2 and respiratory support in newborns: a prospective cohort study. Journal of Perinatology, 38 (5), 505.
4. Shashidhar A, Suman Rao PN, Joe J. (2016) Downes Score vs. Silverman Anderson Score for Assessment of Respiratory Distress in Preterm Newborns. Pediatric Oncall Journal; 13 (3).
5. Donahoe M. (2011) Acute respiratory distress syndrome: A clinical review. Pulm Circ; 1 (2): 192–211. Dec 24, 2016