Sequence patterns in the resolution of clinical instabilities in community-acquired pneumonia and association with outcomes

Abstract

Background: In patients hospitalized with community-acquired pneumonia (CAP), indicators of clinical instability at discharge (fever, tachycardia, tachypnea, hypotension, hypoxia, decreased oral intake and altered mental status) are associated with poor outcomes. It is not known whether the order of indicator stabilization is associated with outcomes.

Objectives: To describe variation in the sequences, including whether and in what order, indicators of clinical instability resolve among patients hospitalized with CAP, and to assess associations between patterns of stabilization and patient-level outcomes. DESIGN/PARTICIPANTS / MAIN MEASURES: Chart review ascertained whether and when indicators stabilized and other data for 1,326 adult CAP patients in six U.S. academic medical centers. The sequences of indicator stabilization were characterized using sequence analysis and grouped using cluster analysis. Associations between sequence patterns and 30-day mortality, length of stay (LOS), and total costs were modeled using regression analysis.

Key results: We found 986 unique sequences of indicator stabilization. Sequence analysis identified eight clusters of sequences (patterns) derived by the order or speed in which instabilities resolved or remained at discharge and inpatient mortality. Two of the clusters (56% of patients) were characterized by almost complete stabilization prior to discharge alive, but differing in the rank orders of four indicators and time to maximum stabilization. Five other clusters (42% of patients) were characterized by one to three instabilities at discharge with variable orderings of indicator stabilization. In models with fast and almost complete stabilization as the referent, 30-day mortality was lowest in clusters with slow and almost complete stabilization or tachycardia or fever at discharge [OR = 0.73, 95% CI = (0.28-1.92)], and highest in those with hypoxia with instabilities in mental status or oral intake at discharge [OR = 3.99, 95% CI = (1.68-9.50)].

Conclusions: Sequences of clinical instability resolution exhibit great heterogeneity, yet certain sequence patterns may be associated with differences in days to maximum stabilization, mortality, LOS, and hospital costs.

Figure 1

Basic sequential patterns of stabilization of discharge criteria. This figure shows the graphical scheme used in subsequent figures, with different shades of color assigned to the orders of stabilization, panel A. The rank order of stabilization is shown in a left to right sequence corresponding to the order in which each indicator is stabilized. The order displayed here and in subsequent graphics (BP = blood pressure; MS = return to baseline mental status; OI = ability to feed by oral intake; RR = respiratory rate; T = temperature; HR = heart rate; O2 = Blood oxygen saturation) corresponds to the overall average resolution pattern in our data, so this “baseline” order is adopted for convenience. Several indicators can have the same rank, since multiple indicators can be recorded as stabilized at the same observation point. For example, in panel B, three indicators were stabilized at observation point 1, so they were all ranked “1st.” Varying shades of green = stabilized n^th or tied for n^th. In addition to the instability resolution coding, we added three additional codes to our data and graphical displays: White = Indicator stable at admission; Purple = Indicator not stabilized before discharge; Orange = Patient died in-hospital before indicator stabilized.

Figure 2

Proportional distributions of the rank order of indicator stabilizations ( N  = 1,326). This figure shows the proportional distributions of the rank orders of indicator stabilization as stacked bars, with different shades of color assigned to each order of stabilization. For example, the white bars show that the BP and MS instabilities were most often (73 % and 59 %, respectively) already recorded as stable at admission. The palest green bars show that the OI and O2 instabilities were most often (28 % and 35 %, respectively) resolved first or tied for first in rank order of resolution of all seven instabilities. The darkest green portion of the O2 saturation instability shows that O2 was resolved last (or 7th) for about 13 % of patients, and the purple portion shows that it remained unstable on discharge for about 23 % of patients. White = indicator stable at admission; Varying shades of green = stabilized n^th or tied for n^th; Purple = Indicator not stabilized before discharge; Orange = Patient died in-hospital before indicator stabilized. BP = blood pressure; MS = return to baseline mental status; OI = ability to feed by oral intake; RR = respiratory rate; T = temperature; HR = heart rate; O2 = Blood oxygen saturation.