Why pain cannot be a vital sign

There’s been a movement afoot for several years now to quantify pain as the so-called “Fifth Vital Sign.” It all started as a well-intentioned effort to raise the level of awareness of inadequate pain control in many patients, but has gotten way out of hand.

The problem is that the word “sign” has a specific meaning in medicine that, by definition, cannot be applied to pain.

When you hear us medicos talk about “signs and symptoms” of a disease, it turns out that they are not the same thing. “Symptoms” are things the patient experiences subjectively; “signs” are things that can be observed objectively by another person. Headache is a symptom; cough is a sign. Itching is a symptom; scratch marks over a blistery linear rash are a sign. Vertigo, the hallucination of movement, is a symptom; nystagmus, the eye twitching that goes with inner ear abnormalities that can cause vertigo, is a sign. If someone other than the patient can’t see, hear, palpate, percuss, or measure it, it’s a symptom. Anything that can be perceived by someone else is a sign.

The traditional “vital signs,” four in number, are measurements of bodily functions: temperature, pulse, respiratory rate, and blood pressure. Technically one could also include weight, height, head circumference, waist circumference, urine output, etc. Vital signs are measured, two of them with specific instruments, and yield numeric results. Normal ranges are defined; values that fall outside those normal ranges are described with specific words (eg, bradycardia, tachypnea, hypothermia, hypertension).

What about pain? It is subjective by definition. If someone says they have a fever, we can measure their temperature. If it is below 99 degrees F, we can say they do not have a fever. If a patients says his or her heart is racing and we count only 80 pulse beats over one minute, he or she is not tachycardic. Not so with pain. If a patient tells us they are having pain, we are supposed to believe them (because they usually are), but we cannot measure or observe it. Sure, there are so-called “pain behaviors”, holding the affected part, writhing, moaning, etc., but as is correctly impressed upon us, the absence of those findings — those signs — does not imply the absence of pain.

It has become fashionable to ask patients to grade their pain on a scale from 1 to 10. It seems so logical. Pain is a 7; give drugs; pain goes down to a 3; success. Much as been written about this ridiculous formulation. Pain is so multidimensional that assigning a single number to it, even subjectively, is nigh impossible. I’m not saying that pain shouldn’t be assessed (serially when administering medications for it), merely that reducing it to a single numerical value is clinically ludicrous.

However you look at it, pain cannot be considered a “vital sign”; not the fifth, nor the twentieth nor the fiftieth. I agree with the importance of assessing pain. It’s right up there with the importance of assessing possible exposure to intimate violence, and the importance of asking if a patient has had a flu shot or a mammogram or a colonoscopy; ad infinitum.

But trying to style “pain as the fifth vital sign” is nothing but an ill-conceived PR campaign.

Lucy Hornstein is a family physician who blogs at Musings of a Dinosaur, and is the author of Declarations of a Dinosaur: 10 Laws I’ve Learned as a Family Doctor.

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