Northwestern University Feinberg School of Medicine
Does volume of emergency department sepsis
experience impact inpatient sepsis mortality?
Emilie S Powell, MD MBA
Rahul K Khare, MD
D Mark Courtney, MD
Joe Feinglass, PhD
Background: Sepsis
• Overwhelmingg systemic
y
infection
Infection  Sepsis  Severe Sepsis  Septic Shock
• Increasing Incidence:
- over 500,000
,
emergency
g y department
p
visits/year
y
- 20% of all intensive care unit admissions
- over 200
200,000
000 deaths each year
• Cost: $16.7 billion annually
• Mortality of 50-60% once shock is present
Angus, Crit Care Med, 2001. Wang, Crit Care Med, 2007.
Role of the Emergency Department
• Approximately half of all septic patients are admitted
via the Emergency Department (ED)
• Difficult to diagnose, treat, and resuscitate
• Validated resuscitation methods: Institute for
Healthcare Improvement Surviving Sepsis Campaign
• Aggressive resuscitation in the ED has been shown to
d
decrease
mortality
t lit by
b as muchh as 35%
Dombrovskiy, Crit Care Med, 2007. Rivers, NEJM, 2001.
Volume-Outcome Relationship
• Successful implementation and patient outcomes could
depend on ED sepsis case volume, experience-level
• Explored extensively in the surgical literature
• Higher case volume = improved outcomes
• Has not been examined in an ED setting, or in the
diagnosis and resuscitation of sepsis
Birkmeyer, NEJM, 2001. Luft, HSR, 1987.
Hypothesis
• Hospitals with higher ED sepsis case volume will have
superior outcomes:
• lower overall inpatient sepsis mortality
• lower
l
early
l inpatient
i ti t sepsis
i mortality
t lit
Study Design
• Cross sectional analysis
• 2007 Healthcare Cost and Utilization Project
Nationwide Inpatient Sample (NIS)
- Largest publicly available all-payer inpatient database
- Discharge records:
- 8,043,415 admissions
- 1044 hospitals
- 40 states
Sample Selection
• Inclusion
I l i Criteria
C it i
• All Adult Patients admitted through the ED with a principal
diagnosis of sepsis: 92,616 patients
• Exclusion Criteria
• Patients admitted through an ED with a very low annual
p case volume: 2,468
,
patients
p
sepsis
• Patients transferred to another hospital: 3,272 patients
• Final Sample: 87,166
87 166 patients from 551 Hospitals
Patient and Hospital Variables
Patient Variables
Hospital Variables
Age and sex
Bed-size
R
Race
andd ethnicity
h i i
U b vs. rurall location
Urban
l
i
Principal diagnosis
Teaching status
In-hospital mortality
Primary payer source
Median income by zip code
Elixhauser co-morbid conditions
Annual ED sepsis case volume
ED Sepsis Case Volume
• Each p
patient assigned
g
annual ED sepsis-case
p
volume
according to the hospital of admission
• Records from hospitals with <25 sepsis cases removed
• Records divided into quartiles
Statistical Analysis
• Demographic data & Unadjusted Analysis
• Categorical
C t
i l variable:
i bl chi-square
hi
t t
test
• Continuous variable: t-test
• Adjusted analysis:
• Population
Population-averaged
averaged logistic regression model
• adjusted for: age, sex, significant co-morbid conditions,
payer-status,
paye
status, income-level,
co e eve , hospital
osp ta ssize,
e, urban/rural,
u ba / u a ,
teaching status
ED sepsis case volume
Key Outcome Measures
• Overall Inpatient Mortality
• Early Inpatient Mortality: within two days of admission
o e directly
d ec y examine
e
e impact
p c of
o ED sepsis
seps s care
c e
• More
• Minimize delayed confounding effects
• Evaluate at a fixed interval to limit length of stay bias
Results: Patient Characteristics
• Quartiles
Q til are similar
i il with
ith respectt to
t
• Age
• Gender
• Proportion of patients with Medicaid / Self-Pay
• Higher volume centers have a greater proportion of:
• Black and Hispanic patients
• Patients in the highest income quartile
Patient Co-morbid Conditions
• A greater proportion of patients at higher volume
centers have:
• Cancer
• Weight Loss
• Congestive
g
Heart Failure
y Disorder
• Fluid & Electrolyte
• Liver Failure
• Coagulopathy
• Peripheral Vascular Disease
• Pulmonary Circulation
Disorder
• Renal Failure
Hospital characteristics
• Higher volume centers were more likely to be:
• Urban-centers
g bed-size hospitals
p
• Large
• Teaching institutions
Unadjusted volume-mortality association
20
18
16
14
12
10
8
6
4
2
0
18.9
18 2
18.2
18.7
16.4
7.8
7.1
7.1
5.8
Overall
O
ll Mortality
M t lit
Early Mortality
Adjusted volume-mortality association
Projections: Adjusted mortality rate
• Adjusted
Adj t d overall
ll inpatient
i ti t mortality
t lit = 17.2%
17 2%
• If all hospitals operated at the level of the highest
sepsis volume centers, overall mortality = 15%
• Potential for 9,400 lives saved annually
Limitations
• Administrative data:
- reliance on principal diagnosis coding
- limited information on disease severity
- co-morbid condition codingg bias
• Early diagnosis bias at high volume centers
Conclusions
• There is a significant relationship between ED sepsis
case volume and inpatient sepsis mortality.
• ED patients with sepsis treated at high volume sepsiscenters experienced significantly lower mortality.
- 27% lower odds of overall inpatient mortality
- 31% llower odds
dd off early
l iinpatient
ti t mortality
t lit
Implications for Policy, Delivery, & Practice
• O
Opportunities
i i to researchh & understand
d
d best
b practices
i
in sepsis care among high volume centers
• Research opportunities:
• determine
dete
e tthee feasibility
eas b ty oof ddisseminating
sse
at g best practices
p act ces
to lower volume centers
pp
to increasing
g sepsis
p
• discover novel approaches
experience in lower volume centers
• Target lower volume centers to improve care delivery
• early recognition and diagnosis of sepsis
• resuscitation
i i andd technical
h i l aspects off care
Thank You
• This research was conducted while a National
Research Service Award postdoctoral fellow at the
Institute for Healthcare Studies at Northwestern
University under an institutional award from AHRQ:
T-32 HS 000078, PI: Jane Holl, MD MPH
Questions
ED Sepsis Case Volume
• Data analyzed by hospital
• Each admission assigned
g
annual ED sepsis-case volume
• Records from hospitals with
<25 ED sepsis cases removed
• Records divided into quartiles
ED Sepsis Case Volume Quartiles
25 - 145 146 – 248 249 – 371 >371
Patient Characteristics
Hospital Characteristics
Results:
Adjusted analysis of overall mortality
Results:
Adjusted Analysis- Hospital Factors