All About Apgar - @ JEMS.com


All About Apgar


 
 

Howard Rodenberg, MD | | Monday, November 26, 2007


It's often surprising where you can find useful information. The television just told me that Michael Jackson may have some issues (who knew?), and I've learned from the Internet that I can get Xanax from Canada. My six-year-old son is also a continual fountain of wisdom. I never knew that a Pokemon could only say its name until he was kind enough to let me know (the only exception is Meowth, a large-headed cat with a New Jersey timbre. The lot of them Charmander, Machop, Diglett, Psyduck are pretty limited. But you'd be amazed how many ways there are to say Pikachu).

Medical knowledge often arises from a similar unexpected source. Remember the Apgar score? You'll recall that we use it to calculate the status of the newborn at one and five minutes after birth. The use of the score has changed, with profound implications for epidemiology, record-keeping and public health. I know this not from the EMS world, but from a random glance at a newsletter issued by the Office of Vital Statistics at the Florida Department of Health.

Before we get into the score, let's take a brief foray into the life of one Virginia Apgar, MD. By any standard, she was a remarkable woman. In an age when few women went beyond high school, Dr. Apgar graduated from Mount Holyoke College in 1929. The Great Depression briefly interrupted her further studies, and she supported herself by catching cats for a physiologic laboratory Matriculating at Columbia University's College of Physicians and Surgeons in 1933, she ventured into surgical training, but quickly learned that to be a woman surgeon in this era was not economically viable. She then focused her efforts on anesthesiology (a specialty I've heard described as "years of tremendous tedium punctuated by moments of sheer terror" or, more derisively, as "passing gas.").

Apgar's time in obstetric anesthesia gave rise to an interest in neonatal assessment, cumulating in the 1953 landmark article "A Proposal for a New Method of Evaluation of the Newborn Infant." It's of interest to note that her idea was not to use the score to predict neonatal outcomes as we use it today, but to assess differences in obstetric practice, maternal anesthesia and neonatal resuscitation using uniform measures of an infant's status. In fact, the original article spends much of the text comparing scores in infants born through different obstetrical techniques and varying anesthetic practices. There is only a brief mention at the end of the paper noting that infants with a score of 2 or less had a mortality rate of 14%, and those with 8 or higher had a 0.13% risk of death (remember that this is in the early 1950s; given 50 years of progress in patient care, current rates are much lower). The original research was also based only on a one-minute calculation. Nevertheless, from this short work an institution was born.

The rest of her career was marked by similar success. Working with the National Foundation for Infantile Paralysis, she helped the organization focus on the prevention of birth defects in the post-polio era as the renamed March of Dimes. A woman of many talents, she was also an accomplished fisherman (fisherwoman? fisherperson?), a stamp collector, and a violin and cello player who learned to construct her own instruments. She was reportedly a fast talker, a trait that caused one colleague to comment, "Some people believed she had another hole for breathing." Following her death in 1974, Dr. Apgar was later memorialized on a 1994 United States postage stamp and inducted into the National Women's Hall of Fame the following year. All in all, not a bad run.

Back to today. The Apgar score measures neonatal status in the first few minutes of life. It is derived from five components, each of which may be assigned a score from zero to two. Therefore, the total Apgar score ranges from 0 to 10. The word "Apgar" is not only a medical eponym in homage to the score's development, but also serves as a mnemonic to the score's components. These include Appearance (color), Pulse, Grimace (reflex irritability), Activity (muscle tone) and Respirations. The full Apgar scoring system is illustrated in the following table:

Score 0 Points 1 Point 2 Points

Component

Appearance (color) Blue or pale Body pink, extremities blue Completely pink

Pulse rate Absent < 100 > 100

Grimace (reflex irritability) No response Grimace Cries

Activity (muscle tone) Limp Some flexion Active flexion and extension

Respirations Absent Weak cry, hypoventilation Good cry, breathing well

(Maybe WE don't always calculate them, but we hope somebody does. When my son was born, his Apgar score was the last thing on my mind. There was the obstetrician asking if I wanted to help with the delivery, to whom I replied, "That's why I'm paying you real money." There was my son's mother swearing at me in Italian in the throes of labor, a language which I don't speak, but could recognize the intent. There was the moment I recognized that women in labor have no sense of humor, when I placed a children's ED sticker proclaiming "I Got a Shot" over the site of her Demerol injection. And there was the fact that I got to hold my son before anyone else, and that after I looked at him and he looked at me, he shut his eyes tightly and began to cry in what I can only attribute to his good sense, and that despite the entreaties of the nurses to let him rest in the nursery I was bound and determined to never let him go. What an interesting evening. Wouldn't trade it for the world.)

Traditionally, we've used the Apgar score to assess the infant's status at one and five minutes after birth. However, it's crucial to note the underlying assumption behind our use of the score. The first is that abnormalities in the Apgar score are produced by fetal asphyxiation (with associated hypoxia, hypercarbia and acidosis). The second is that the Apgar score can be used to predict fetal outcomes.

The reassessment of the Apgar score is predicated on a more enlightened view of these underlying beliefs. A low Apgar score may not, in fact, be a reliable indicator of asphyxia. A host of other factors may influence the score. The neurologic status of the newborn is in large part dependent upon physiologic maturity, and a preterm infant might be expected to have a lower score than a full-term birth even under normal circumstances. Fetal infection, underlying cardiac or respiratory disease, or maternal drug use (recreational or iatrogenic) may also contribute to a diminished score. So while the Apgar does help to determine fetal status, a low score is not necessarily diagnostic of asphyxia. Instead, the Apgar score simply presents a "snapshot in time" of fetal status.

We've also been taught that the Apgar score is a useful measure of fetal outcome. However, the evidence is fairly clear that the one-minute score does not correlate with an infant's actual prognosis. Even the five-minute score is of dubious prognostic value. According to a Joint Policy Statement of the American Academy of Pediatrics and the American College of Obstetrics and Gynecology, a low five-minute score (< 3) correlates poorly with neurologic outcome and is linked to an increased incidence of cerebral palsy (the end result of fetal cerebral asphyxia) of only of 0.3 1.0%. Five-minute scores from 4 to 6 fail to serve as an effective marker of future neurologic problems, and scores of 7 to 10 are considered clearly "normal." The unreliability of the Apgar score in predicting outcomes is demonstrated by noting that 75% of children with cerebral palsy had normal Apgar scores at birth.

We've previously mentioned the "snapshot" role of the Apgar score. It's within this framework that the score holds its power, for the strength of the score lies in changes over time. It's been demonstrated that changes between one- and five-minute scores are useful measures of the effectiveness of neonatal resuscitation. Infants with point totals of <3 at five minutes, but 4 or above at 10 minutes, have a 99% chance of not having cerebral palsy later in life. And when there is no change, when the picture in motion becomes a still life, the Apgar has meaning. When low scores are prolonged at 10, 15 and 20 minutes, neurologic outcome is at risk.

The unreliability of the one-minute score coupled with the real value of changes in the point totals has led to new recommendations in the use of the Apgar scheme. Although no one will argue with the calculation of a one-minute score, validity is found in the five-minute score and, if required, subsequent scores to gauge the progress of an infant at risk. That's why the birth records in Florida are being changed to reflect the five- and 10-minute scores (the latter only as required in the face of an initial value < 5), and why I learned about this from the Vital Statistics Newsletter and not one of the usual medical sources. It pays to keep your eyes open.

They say that in comedy, love and hand grenades, timing is everything. If I've gauged it right, this column is likely to run during the first couple of weeks of the New Year. If the beginning of 2004 can be considered a one-minute score, I'll grant us a score of 10. My wish for all is that we never sink to single digits throughout the coming year.


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