One of the more difficult things to relate to new EMTs who are just cutting their first patient assessment teeth is putting assessment finding in context. Frequently, while teaching a new batch of EMT students patient assessment, I’m peppered with questions like these:
“How fast does the pulse have to be before you consider the possibility of shock?”
“Do you always put someone on oxygen when they have pale skin?”
“How slow does a person have to breathe before we should start breathing for them?”
“So if the blood pressure is low, that means that they are bleeding?”
“If the patient doesn’t have pinpoint pupils, should I still give Narcan?”
“What does the Glasgow need to be before we decide to go emergent?”
All of these questions have a simple desire at their core. The desire to know, with certainty, that a single assessment can give us the answer to our treatment questions. We want patient care to be simple. If then, then this. The less experience we have, the more cook-book we want patient care to be.
The unfortunate truth that our new EMTs are (hopefully) quick to learn is this, patient assessment is never quite that simple. Everything needs to be taken in context. Respiratory rate is inseparably bound to tidal volume. Pallor is dependent on the patients baseline. Some abnormal findings aren’t abnormal for patients with congenital pupil abnormalities or naturally pale skin. The unsatisfying answer to many of these questions is, “It depends.”
One of the more difficult aspects of patient assessment is being able to step back and put it all together. What do all these symptoms, when taken together, mean to me as a caregiver? What does the current constellation of symptoms mean?
To that end, I think it’s useful to understand the shock index. The shock index s a simple calculation, based on the heart rate and the systolic blood pressure, that uses the coloration between those two numbers to try to identify potential shock patients. Understanding the shock index helps us understand how multiple vital signs can be evaluated in combination to increase our index of suspicion for certain occult injuries or disease processes. (In this case, shock.)
Here’s how we calculate the shock index. We take our patients systolic blood pressure and we divide it into the heart rate in beats per minute. Under normal conditions, we will tend to get a number between .5 and .8. (Yes, you can do this on your smart phone if you, like me, are mathematically challenged. As a for-instance, when the classic vital findings of HR = 80BPB and a Blood pressure = 120/80.
Our shock index calculates a comfortable .67. When the systolic blood pressure and the pulse become equal (for instance HR = 100BPM, BP = 100/60) our shock index reaches an uncomfortable 1.0. The farther we climb above that number, the higher our index of suspicion for an underlying shock state.
This holds true for all of our shock presentations including those sometimes cryptic presentations like sepsis and occult bleeding. This is where recognizing the concept behind the shock index can be a powerful tool in your physical assessment arsenal.
One of the powerful things about calculating the shock index is that it keys us in to the critical association between vital signs.
Vital signs don’t exist in a vacuum. None of our assessments live in a vacuum. We must consider them in association with the entire clinical picture.
Research suggests that calculating the shock index might help us identify the presence of occult traumatic bleeding even when one of the two vital signs in question remain within a normal range (for any number of reasons). But even more than that, understanding how the shock index works can help us become more in tune to the relationship between all of the vital signs…even when we don’t take the time to calculate it. And that’s where it might prove its real value.
I’m not yet ready to recommend calculating the shock index as part of a standard trauma assessment. While it could be used on the fly in limited clinical presentations, I’d prefer to see EMTs play with it retrospectively and prospectively to better understand how these two vital numbers work in combination to help us identify underlying shock states.
Have fun with it and let me know how it goes.
Now it’s your turn. Have you experimented with the shock index? Did you find it useful? Leave us a comment and let everyone know what you think.
