Page 44 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 2: Measuring Quality 13

patients, those with specific conditions being cared for in a specialty Table 2-3 contains a list of selected processes of care indicators, with
ICU outside of the needs of the patient, may actually be harmed by validated outcomes summarized to guide in understanding expected
these models. benefits from these processes. The last column contains a description
■ PROCESS of the suggested quality indicator to be measured. The definitions are
intentionally broad to allow for local needs in defining eligible patients.

Given the limitations in studying outcomes or structure as measures of Given the state of evidence, it is entirely possible that some of these
evidence-based process measures will be under debate as you review
quality, process of care seems like an appealing option. Process measures this table.
have intuitive appeal to clinicians who may find data showing that they
than recommendations about structure of the ICU or risk-adjusted ■ OUTCOME
are not doing something they believe they should be more compelling
mortality. It also seems a clearer way to address a clinical behavior than Mortality, despite its limitations, will always remain high on the list of
other quality reports. Finally, for statistical reasons it is easier to moni- quality measures stakeholders request when discussing quality. For obvi-
tor changes in more common processes than in rare events like death or ous reasons, crude mortality is inadequate to assess this outcome, and
VAP. Selecting process measures, particularly in critical care, presents intensive care has led the field of risk adjustment for decades. 132-134 Scoring
some challenges. Ideally process measures should be linked with com- systems have helped us simplify our epidemiological description of criti-
pelling, usually randomized trial, evidence of a direct effect on outcome. cally ill patients and adjust for confounding due to severity of illness in
These evidence-based process indicators may be referred to as outcome research; however, they have not been validated to be used for (1) bench-
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validated and represent direct measures of quality. Unfortunately, marking or (2) identification of low performing units. One important
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there is scarce availability of indicators that have been robustly validated question remains to be answered: Is it useful to monitor mortality over
in critical care. Even processes of care based on large randomized clini- time as a quality improvement strategy in individual units? Intensivists
cal trials, such as low tidal volume ventilation for acute lung injury, advocate for several different methods of longitudinal follow-up, including
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have been disputed in the literature. This is the very nature of science serial standardized mortality ratios (SMRs), risk-adjusted p charts, risk-
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and to expect 100% agreement would break the safeguard against col- adjusted CUSUM charts, and other approaches. However, to date there
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lective error that derives from differences in opinion. Although not are no data to validate the use of longitudinal SMRs to monitor quality.
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unique to critical care, developing strict process measures of quality of What makes risk-adjusted mortality unsuitable to be used as a quality
care will always be difficult as the evidence base is modest and evolving. indicator?
Glucose control and renal dose dopamine are just a few of the treatments
that might have made excellent process measures of quality until they 1. SMRs can change due to factors unrelated to the quality of care,
were shown to be ineffective or harmful. such as the way laboratory values and vital signs are recorded. In an
There is a bit of confusion in the literature regarding what processes of elegant study, patients had laboratory values and vital signs recorded
care means. Examples of processes of care include deep venous throm- at ICU admission and then as per clinical indication (standard mea-
bosis prophylaxis, sedation interruption strategies, daily assessment of surement), concomitantly, the authors measured laboratory values
readiness to wean, head of bed elevation, assessment for early enteral every 2 hours and vitals whenever they were abnormal (intensive
nutrition, compliance with evidence-based protocols, use of continu- measurement). The intensive measurements led to absolute SMRs
ous subglottic aspiration, stress ulcer prophylaxis, and low tidal volume 10% lower than the standard measurements, in both APACHE II
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ventilation. Practices that are frequently cited as processes of care, but and SAPS II. An ICU using more intensive measurement will look
that we do not consider as such, include length of ICU stay, proportion better than one that uses standard measurement, even when no real
of occupied beds, duration of mechanical ventilation, plateau airway differences exist because the more intensive monitoring yields more
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pressures below 30 cm H O, and central venous saturation above extreme values for severity of illness variables.
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70%. The reason for not considering these as processes of care indica- 2. Differences in case mix may lead to differences in the estimate of
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tors is that they are confounded by patients’ characteristics and are not the SMR. Even though risk-adjusted models are supposed to deal
under the exclusive control of providers. It is easy to understand this with different patient characteristics, they are still far from perfectly
concept when we discuss ICU length of stay or duration of mechanical calibrated. In fact, changing the severity of the case mix leads to
ventilation. These end points are clearly influenced by more than just our differences in the SMR even when there are no real differences in
clinical processes of care and cannot be compared across patients and/ observed outcome per category. In one study, the SMR was catego-
or centers without appropriate risk adjustment. However, it is harder to rized by mortality risk, with a cutoff of 10% risk. Patients with
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understand why physiologic targets of appropriate treatments are not lower risk had SMRs above 2, while those with higher predicted
ideal process of care variables. For example, lung protective ventilation risk had SMRs close to 1. Obviously, units with higher percentage
for ARDS using one protocol prescribes the tidal volume and a target of low-risk patients may look worse than units that care only for
plateau pressure. The physician has complete control over setting the sicker patients. This effect is also expected with different popula-
tidal volume, however, the resulting plateau pressure reflects a complex tions where the model may calibrate differently in different patient
interaction between the process measure (tidal volume) and patient fac- subsets. Therefore, even though risk-adjustment models were devel-
tors like thoracic compliance. Ideally, the quality measure would capture oped to allow for comparisons of different groups of patients, their
the attempt of the physician to respond to the plateau pressure and imperfect calibration makes this use challenging.
titrate the tidal volume, but this is difficult to measure. There is nothing
wrong with including physiologic targets of evidence-based processes Nevertheless, it seems inappropriate to completely ignore the infor-
like plateau pressure, central venous saturation, or sedation scores as mation that may be present in risk-adjusted mortality data. The main
quality measures, however, they lack one of the basic advantages of concern is that the SMR and changes in it over time should prompt
process measures, specifically, insensitivity to patient factors and risk appropriate investigations. Hospitals with SMRs that indicate low mor-
adjustment. Therefore, if an ICU looks bad because their patients tend tality and good quality of care should not be overly confident that quality
not to achieve some physiologic targets, this might be due to failure is excellent anymore than hospitals with poor SMRs should be punished
to adequately implement the process of care or it might be due to age, for an isolated value.
obesity, severity of illness, or any of a number of patient factors. If physi- Recent years have been marked by an increasing interest in nosoco-
ologic targets of evidence-based process measures are included in qual- mial infections such as VAP and catheter-related blood stream infection
ity assessments, some thought should be given to the need to risk adjust (CR-BSI). Hospital-acquired infections are an exciting topic for many
the results to the patient population. stakeholders. They are thought to be preventable and causally linked

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