60% of patients in the United States who develop severe sepsis are older adults (age 65 and over) [1], and the mortality of severe sepsis increases steadily with age to nearly 40% in those over 85 [2]. There are many factors that make older adults more susceptible to sepsis, and that can also make sepsis more difficult to detect. Here are some tips to help explain why this is, and how you can identify it sooner.

Definitions

First, let’s recap some definitions of the systemic inflammatory response syndrome (SIRS) and sepsis spectrum.

The SIRS criteria are:

• HR >90
• Temp >38C or <36C
• RR >20 (or PaCO2 <32)
• WBC >12 or <4, or bands >10%

Sepsis = 2 SIRS criteria + a source of infection

Severe sepsis = sepsis + signs of end organ damage (elevated Cr, AMS, coagulopathy, elevated lactate, hypotension, oliguria, hypoxia, among others)

Septic shock = severe sepsis + hypotension despite fluid challenge

Why older adults become sick and why they worsen more quickly

Many different risk factors contribute to the high rates of severe sepsis in older adults. Some of the major factors include immunoscenescence (declining humoral and cell-mediated immune function) [3], functional limitations or bed rest, higher burden of chronic disease, and exposure to infectious in health care settings and nursing facilities [4]. Other factors that may contribute include poor nutrition, poor dentition, dementia, polypharmacy, and muscle atrophy and wasting [2]. Together these factors result in lower physiologic reserve in older adults. There is clearly a range of health among older adults, and we have all seen healthy 85 year-olds who look more vigorous than many 55-year olds. However, on average, the ability of the body to compensate to stressors such as illness and injury decreases with age. Consider this hypothetical graph of physiologic reserve and age. The same stressor in a 30 year old and a 75 year-old will bring the 75 year old closer to the point of being unable to physiologically compensate with mechanisms such as vasoconstriction, tachycardia, tachypnea, and a robust immune response. The older adult will reach the point of decompensation and multi-organ system failure earlier in the course of their illness.

SIRS criteria are not as sensitive in older adults

“Is this person sick or not sick?” is a fundamental question for emergency physicians. When a patient’s heart rate is 150 with a respiratory rate of 30 and a WBC of 18, it is easy to answer that question. With an older adult who may have normal vital signs but be ‘acting funny’ or feeling ‘weak and dizzy’ it can be harder to tell.

It is difficult to study “SIRS-negative” sepsis, since the very definition of sepsis includes the SIRS criteria, which can be problematic particularly for older adults. However, older adults can go from infection to severe sepsis and sometimes not meet SIRS criteria. Staying alert to the signs of end organ dysfunction or subtle vital sign irregularities may help you identify older patients who are on their way to decompensation, and allow you to intervene earlier.

In older adults, don’t exclude sepsis – even severe sepsis – simply because the patient does not meet SIRS criteria. Cardiac disease and beta blockers can both prevent a rise in HR that might normally occur. Older adults may not be able to mount a fever or an elevated WBC response to infection, particularly earlier on in the course of illness. Hypothermia rather than hyperthermia can often be an ominous sign of serious infection. Underlying COPD can mask what might otherwise be a low PaCO2. Studies have also shown that abnormal triage vital signs in adults 75 and over have poor sensitivity for predicting death or ICU admission (sensitivity 73%, specificity 50%) [7]. So be cautious.

Look for other signs in addition to the typical SIRS criteria, such as a relative increase in HR or RR compared with prior vital signs or another visit (the patient may report subjective shortness of breath), an increased oxygen requirement, confusion or delirium, reduced urine output, new urinary incontinence, or lab abnormalities such as new elevated INR, LFTs, creatinine, or lactate. Organ dysfunction is much more important for predicting mortality than SIRS criteria [5]. Mortality is not necessarily increased when SIRS criteria are present compared with suspected infection without SIRS [5], which highlights some challenges with using the SIRS criteria for sepsis [6].

Take home points

• Have a low threshold for considering sepsis and severe sepsis in older adults
• Be aware that the SIRS criteria may not identify older adults with severe infections with the same sensitivity as in younger adults.
• Use other criteria in addition to SIRS to make you think of sepsis or severe sepsis
  • Any signs of end organ injury
  • Elevated lactate or other lab abnormalities
  • Changes in mental status
  • Changes in urine output or continence
• Be aggressive with treatment when appropriate. Except in cases where the patient or family have indicated that they do not want certain treatments or aggressive therapies, or when it is clearly medically futile (a difficult thing to ascertain at times), treat sepsis and severe sepsis aggressively. The surviving sepsis campaign has detailed recommendations for time-based treatment targets, but the key points are:
  • Early identification
  • Early fluids
  • Early antibiotics and source control

References

1. Girard TD, Opal SM, Ely EW. Insights into severe sepsis in older patients: From epidemiology to evidence-based management. Clin Infect Dis. 2005;40(5):719-727. PMID 15714419
2. Destarac LA, Ely EW. Sepsis in older patients: An emerging concern in critical care. Advances in Sepsis. 2002;2(1):15-22.
3. Opal SM, Girard TD, Ely EW. The immunopathogenesis of sepsis in elderly patients. Clin Infect Dis. 2005;41 Suppl 7:S504-12. PMID 16237654
4. Girard TD, Ely EW. Bacteremia and sepsis in older adults. Clin Geriatr Med. 2007;23(3):633-47 PMID 17631238
5. Shapiro N, Howell MD, Bates DW, Angus DC, Ngo L, Talmor D. The association of sepsis syndrome and organ dysfunction with mortality in emergency department patients with suspected infection. Ann Emerg Med. 2006;48(5):583-90, 590.e1. PMID 17052559
6. Talan DA. Dear SIRS: It’s time to return to sepsis as we have known it. Ann Emerg Med. 2006;48(5):591-592. PMID 17052560
7. Lamantia MA, Stewart PW, Platts-Mills TF, et al. Predictive value of initial triage vital signs for critically ill older adults. West J Emerg Med. 2013;14(5):453-460. PMID 24106542

Image credit [1], [2 – C. Shenvi]

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