EFFECTS OF RESIDENTS ON EFFICIENCY IN AN EMERGENCY DEPARTMENTJ. Silberholz, D. Anderson, E. Sze, J. Lim, E. Taneja, E. Tao, B. Kubic, K. Johnson, D. Kalowitz, J. Kellegrew, A. Simpson, M. Harrington, Dr. Jon Mark Hirshon,Dr. Bruce Golden

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Overview

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Broad HealthcareLandscape

-Health Care Reform Bill, 2010-Americans spent $2.3 trillion on health care in

2007-Hospitals are one of the least efficient sectors

University of MarylandMedical Center (UMMC)

UMMC UMMC ED

800 beds1,182 doctors742 residents

55 beds20% admission rate

46,000 patients/year

Residency Model

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Research Question

What effects do residents have on the efficiency of the emergency department?

• Total throughput• Patient waiting time

Residents are in the hospital to learn

One conjecture is that the teaching of residents takes time away from patient care and negatively affects efficiency

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Resident Seminars• Residents absent every Wednesday morning for a

seminar• No replacement workers hired• Wednesday mornings provide a representative sample of

all emergency department activity• Wide range of arrival rates • All types of patients and severities• Congestion levels vary as well

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Simulation Model Overview

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Patients Generated

•Poisson process with varying rates

Triage Nurse

•Severity and treatment parameters assigned

Waiting Room

•Patients held until called back

Bed and Treatment

•Patients called back according to Analytic Hierarchy Process

•If the patient has not left before being seen, they are taken to a bed to be treated

•Treatment time drawn from empirical distribution for this patient’s category

Discharge

•Patient either discharged or admitted as an inpatient

•Once the bed has been cleaned, a new patient is chosen by the AHP

Patient Arrivals• Nonhomogenous Poisson Process

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Patient Attributes

• Sent to ambulatory zone?• Severity Score: 1(high) to 5(low)• Admitted to inpatient ward?• Triage time• Labs needed (Yes/No)?• Drawn from historical data

• (database data Oct 2009 – Jan 2010)

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Patient 1 2

Sent to AZ? No No

Severity? 2 4

Admitted? Yes No

Triage Time? 4 min. 8 min.

Labs Needed? Yes No

Patient Bed Selection• Analytic Hierarchy Process (AHP) used to determine

which patient is chosen for next available bed• Pairwise comparisons between all combinations of

solutions• Each admission from database examined• Decision made based on severity level of patient and

number of times passed over

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  0 Losses 1 Loss 2-3 Losses 4+ Losses

Severity N/A 5.89 1.58 0.58 0.18

Severity 1-2 5.19 3.25 2.07 0.52

Severity 3 3.11 1.91 1.26 0.63

Severity 4-5 0.64 0.31 0.32 0.19

AHP scores from 1/9 (lowest priority) to 9 (highest) based on severity

Abandonment• Patients sometimes

leave before they are called back

• Simulation determines abandonment probability based on a function of severity score and time in waiting room

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Patient Categories for Treatment Time

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YesNo

Yes No

Model Validation• Compared patients per bed per day, abandonment rate,

average time until first bed and total time in system statistics from simulation to those from historical hospital data

• Also Kolmogorov-Smirnov test comparing total time in system distributions found no difference (p = .18)

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Metric Historical Value Our Value

Patients Per Bed Per Day

2.35 2.39

Abandonment Rate 8.02% 7.76%

Time to First Bed 80.3 minutes 81.1 minutes

Experimental Design

• Alter percent of both high and low priority patients seen by residents to test how decreasing resident activity affects the efficiency of the system

• Performance metrics used• Time to Bed• Total Time in System• Throughput

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Effect on Throughput

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Increasing resident presence from 0 to 100% increases throughput by 5%

Effect on Total Time In System

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Increasing resident presence from 0 to 100% decreases total time in system by 11%

Effect on Waiting Time

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Increasing resident presence from 0 to 100% decreases waiting time by 25%

High Severity vs. Low Severity

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Vertical contour lines imply that percent of high severity treated is the driving factor in efficiency gains – most of the patients treated are high severity

Effects on Time in System

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Again, the vertical contour lines imply percent of high severity patients seen is the driver for gains in efficiency

Results

• Residents do have an impact on the efficiency of the ED

• Contrary to our original intuition, residents add efficiency to the system

• Strong linear relationships found between percent of patients seen by residents and throughput metrics

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Discussion• Strong linear trends showing increasing efficiency with residents present

• Most important for high severity patients to be seen by residents

• Decreases patient service times slightly, which leads to significant decrease in time to bed for low priority patients, as there is more slack in the system

• Contradicts the notion that residents themselves are a source of inefficiency – we do not compare them to other healthcare workers

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Future Work

• Quantify effect of each additional healthcare worker and compare nurses and nurse practitioners to residents

• Model doctor decisions explicitly, show how they move through ED

• Identify bottlenecks in the system• Include data gathered in person to help model doctor movement

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