Really dumb question, but I'm sort of failing to see the importance of saying someone is in SIRS and how that affects management/diagnosis. For instance, Patient A has clinical symptoms of typical comm-acquired pneumonia, along with leukocytosis. Now let's say they get a fever or get tachycardic. Now they're in SIRS. What does this change about dx/managment/Tx? Everytime I present a case involving some sort of infection my resident asks me: "do they meet the criteria for SIRS?" and I always answer yes/no, but that never seems to change how we manage the patient. So what's the utility of saying they're in SIRS if it doesn't change anything? I realize this probably has an obvious and simple answer, but bear with me--I'm only in my 2nd week of IM
This is literally one of the most painful points of my life. Attendings... ATTENDINGS don't get it. I've had people admitted to my service for a heart rate of 91 and a WBC of 12.1. No symptoms. No complaints. ALREADY on outpatient IV antibiotics. I mean... seriously?
easy way to say it is that if you have an infection, if you meet SIRS criteria you have sepsis, not SIRS. SIRS itself rarely guides management where as sepsis vs. no sepsis does often guide management.
You need SIRS with a source to have sepsis. If you have no more sense than a 3rd year in the 2nd week of IM, you might think that SIRS directs medical decision making. It doesn't. It does (or should) direct clinical reasoning... look for a cause of the syndrome, one cause of which might be an infection. Its a useful exercise to have medical students do, because you are going to start associating certain patterns more closely with each other, and you start to see syndromes rather than discrete vitals. It moves from "Differential of fever + differential of tachy + differential of tachypneic" to "differential for SIRS positive"
SIRS criteria is used to identify the presence of inflammation in the body. When associated with either a fever or leukocytosis, the chances that the immunocompetent patient is infected is high, and they would likely benefit from antibiotics. This is a sensitive test, not a specific one. Which means that if no SIRS, probably don't need antibiotics, and NOT if SIRS then do need antibiotics.
Interestingly enough, when you have trouble ventilating, your respiratory rate and pulse tend to increase, and the SIRS criteria is very easy to reach on those two points.
In fact,
SIRS criteria without fever or leukocytosis in an
immunocomeptent patient has a positive likelihood ratio less than one. Which means finding tachycardia and tachypnea makes it LESS likely they are infected (as long as fever and leukocytosis are absent). If you don't believe me, look around the next time you're at the gym. Tachycardic? Tachypneic? You should be, if you're doing anything at all, other than posing in the mirror. How many of those people have a need for antibiotics (other than Gc or Chla)? How many of those people even have systemic inflammation?
The reason why Tachycarida and Tachypnea are SIRS criteria is because people who are
immunocompromised (chemo, AIDS, transplant, immunosuppresion) may not have the immune system to mount a leukocytosis or a fever. Not that they will necessary be low (that is also criteria), its just that their immune system is not robust enough to show you an infection. In fact, they wont consolidate on a chest x-ray when bacteria are there, it won't burn when they pee, and they may not even have signs of meningeal irritation. The point is, if you see
any SIRS in immunocompromise you must at least think of an infection because the clinical presentation is often deceiving. These people have a much lower threshold for needing antibiotics; especially when initial diagnostics for a source are underway (cultures will be positive eventually).
So what's the point to SIRS?
1. Don't miss someone who could benefit from antibiotics
2. Recognize that immunocompromised patients are sicker than they appear
3. Fever or Leukocytosis is "required" (practically) in immunocompetent patients
4. If they are SIRS positive but ROS negative, consider another inflammatory disorder that does not have to do with infections or antibiotics.
Billing
1. Hospital gets paid more if there is "Sepsis 2/2Pneumonia" than for just "Pneumonia."
For a medical student perspective: know if SIRS yes or no.
See how long that took? Its actually much more complicated than people realize, and much more complicated than people care to learn. Which is why people meet "admission criteria" even though they probably could just go home. See that 60 minutes special on HMA. The computer flags someone as ill because they meet criteria. Dumb-dumbs (or money hounds) will obey the computer; clinicians will weight what that actually means relative to a vast number of other factors.
