HAIs: An even bigger problem than we thought?

Our fellow blogger, Eli, has co-authored an interesting study in this month’s Archives of Internal Medicine. Using a national administrative database that contains 69 million hospital discharges, the investigators examined the attributable outcomes associated with two hospital-acquired infections—sepsis and pneumonia. The outcomes were stratified as to whether they occurred in association with a surgical procedure or not. When sepsis occurred post-operatively, it added on average 11 days to the hospital stay and $33,000 to the cost of care, and carried a nearly 20% attributable mortality. Post-operative pneumonia on average added 14 days to the stay and $46,000 to the cost of care, and had an attributable mortality of 11%. For cases not associated with surgical procedures, when adjusted for the preinfection length of stay, sepsis on average added 2 days to length of stay at an additional cost of $6,000, and was associated with an attributable mortality of 16%. Hospital acquired pneumonia in nonsurgical patients added 4 days to length of stay on average, added $11,000 to the cost of care, and had an attributable mortality of 10%. Extrapolating to the US population, the investigators estimated that these two conditions account for over 2 million hospital days, $8 billion in costs, and 48,000 deaths.

Diving into the murky sea of administrative data is a perilous business, but the authors of this paper took great pains to use diagnoses for which validation has been shown to be high level and were careful in their methods to minimize bias and confounding (the methods section of the paper is about twice as long as the results). The incidence of each of these complications is about 1% or less, which makes it difficult for the average clinician to assess impact in their patients. Importantly, what this study does not tell us is the fraction of these cases that are preventable. However, even if only a quarter are preventable, this paper tells us that healthcare associated infections are a big, big problem, and those of us who work in infection prevention have a very long journey ahead. 

Lastly, this study should remind us that our targets should be infections not organisms. This problem is too big to tackle one organism at a time. To the patient with life-threatening sepsis, it matters little whether the cause is MRSA, MSSA, or a multidrug-resistant gram negative rod. Multipotent interventions driven to high levels of compliance will be necessary to ultimately bring these infections to the irreducible minimum.


  1. How do we not interpret pneumonia deaths as deaths from sepsis? How many sepsis cases were due to HAP? Are these cases defined as sepsis or pneumonia cases?

    Whatever the case, the data are compelling.

    Thanks in advance for the clarification.

  2. Thanks Chris; good question. Of course sepsis is not always in the causal pathway between pneumonia and death. For example, patients can die of respiratory failure without sepsis. For a bacteremia outcome, it is likely best not to exclude or control for shock or sepsis, since there are few other ways to die from bacteremia. (see my first ever publication: Clin Infect Dis. 2000 Nov;31(5):1311-3)

    However, if a case had codes for both sepsis and pneumonia, Mike Eber included the cases for both the sepsis estimates and the pneumonia estimates. He summarized the costs of cases with and without overlap in the discussion section (see below). In the aggregate estimates of costs, he used the patient-level costs of sepsis cases times the number of sepsis cases and added to this the patient-level costs of pneumonia cases recalculated to exclude sepsis cases times an estimate of the number of pneumonia cases excluding sepsis cases. (you have to read that at least twice before it sinks in)

    From the Discussion Section: Among invasive surgery patients, for example, sepsis associated with pneumonia had attributable mean LOS, hospital costs, and in-hospital mortality of 23.7 days, $80 000, and 27.9%, respectively, whereas these outcomes were 10.3 days, $30 800, and 18.7%, respectively, for cases of sepsis not associated with pneumonia. Outcomes in pneumonia cases that were not also coded as sepsis cases in the results were 12.5 days, $41 500, and 8.1%, respectively.


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