Reducing Door-to-Needle Times Using Toyota’s Lean Manufacturing Principles and Value Stream Analysis
Background and Purpose—Earlier tissue-type plasminogen activator (tPA) treatment for acute ischemic stroke increases efficacy, prompting national efforts to reduce door-to-needle times. We used lean process improvement methodology to develop a streamlined intravenous tPA protocol.
Methods—In early 2011, a multidisciplinary team analyzed the steps required to treat patients with acute ischemic stroke with intravenous tPA using value stream analysis (VSA). We directly compared the tPA-treated patients in the “pre-VSA” epoch with the “post-VSA” epoch with regard to baseline characteristics, protocol metrics, and clinical outcomes.
Results—The VSA revealed several tPA protocol inefficiencies: routing of patients to room, then to CT, then back to the room; serial processing of workflow; and delays in waiting for laboratory results. On March 1, 2011, a new protocol incorporated changes to minimize delays: routing patients directly to head CT before the patient room, using parallel process workflow, and implementing point-of-care laboratories. In the pre and post-VSA epochs, 132 and 87 patients were treated with intravenous tPA, respectively. Compared with pre-VSA, door-to-needle times and percent of patients treated ≤60 minutes from hospital arrival were improved in the post-VSA epoch: 60 minutes versus 39 minutes (P<0.0001) and 52% versus 78% (P<0.0001), respectively, with no change in symptomatic hemorrhage rate.
Conclusions—Lean process improvement methodology can expedite time-dependent stroke care without compromising safety.
Clinical outcomes are improved as a function of earlier tissue-type plasminogen activator (tPA) delivery.1,2 Therefore, national guidelines have encouraged rapid evaluation and treatment of patients with acute ischemic stroke. Stroke-specific American Heart Association’s “Get With The Guidelines” (GWTG) were created to ensure that evidence-based practices were adopted by hospitals and incorporated into stroke patient care.3 One GWTG metric is a goal time from patient arrival to treatment with intravenous tPA (door-to-needle time [DNT]) of ≤60 minutes. Despite the known time-dependence of tPA efficacy, only 27% of 25 000 tPA-treated patients within the GTWG database received tPA within 60 minutes of hospital arrival.4
Lean manufacturing principles were originally pioneered by Taiichi Ohno, father of the Toyota Production System, who aimed to eliminate inefficiencies within automobile production, leaving only the crucial steps that added value to the customer.5 After 5 decades of use in the manufacturing sector, lean principles have been recently applied to health care, leading to shorter emergency department (ED) wait times and improved procurement of endovascular stents within radiology departments.6,7
In early 2011, we assembled a multidisciplinary team to use a common lean tool known as value stream analysis (VSA) to improve DNTs for patients with stroke receiving intravenous tPA. The “current-state analysis” mapped out wasteful operations and those that added value. A “future-state analysis” removed wasteful steps and retained value-added steps. An “action plan” was created to implement the streamlined protocol and provide feedback for continued improvement. The protocol’s efficiency and safety metrics were compared before and after implementation.
Data were prospectively collected as part of the Cognitive Rehabilitation Research Group Stroke Registry developed at Washington University in 1998. This registry includes patients with stroke admitted to an urban, tertiary care hospital admitting 1500 patients with stroke annually. In the current study, tPA-treated patients with stroke were included with the following clinical information: demographics, medical history, admission National Institutes of Health Stroke Scale, DNT, onset-to-needle time, door-to-CT completion, and door-to-laboratory completion times; discharge location; 90-day modified Rankin Scale; and length of hospital stay. Symptomatic intracerebral hemorrhage (defined as in the National Institute of Neurological Disorders and Stroke tPA trial as intracerebral hemorrhage within 36 hours of symptom onset that correlated with any decline in neurological status) and stroke mimics (defined as a discharge diagnosis other than ischemic stroke) were retrospectively collected from the patients’ charts.
Lean Improvement Process and VSA
Beginning in 2006, the hospital’s leadership made a commitment to improving the “flow of value” to patients by applying lean principles. Lean performance engineers used several lean tools for process improvement directed at multiple disease processes, one of which was stroke. We present the results of one of several lean strategies, known as VSA, which was used to expedite tPA delivery to patients with acute stroke arriving in the ED.
Briefly, a lean engineer, ED and neurology physicians, ED nurses, patient care and radiology technicians, and an ED pharmacist met over the course of 2 days to perform a VSA that involved 4 steps: (1) “current-state analysis”: each step of the tPA protocol was identified as a source of lost productivity (ie, waste) or a step that “added value”; (2) “future-state analysis”: a “lean” process was formulated to minimize any wasteful operations; (3) an “action plan” was created for rapid implementation of the new protocol; and (4) a “feedback loop” was instituted to continuously identify and eliminate waste over time (online-only Data Supplement).
The “pre-VSA” epoch (January 1, 2009, to February 28, 2011) was compared with the “post-VSA” epoch (March 1, 2011, to March 1, 2012) with regard to baseline characteristics, protocol metrics, and clinical outcomes. Wilcoxon rank sum and Fisher exact tests measured differences in continuous and binary data, respectively (P<0.05 required for significance). To adjust for imbalances in baseline characteristics, analysis of covariance was performed including all imbalanced variables as covariates and pre- versus post-VSA as a fixed effect on DNTs. Kruskal-Wallis analysis of variance measured differences in DNT over the 4 quarters post-VSA to determine if DNTs were sustained. To assess which baseline or protocol-related variables predicted DNT post-VSA, a linear regression model was created with predictors selected using a forward stepwise procedure (P≤0.20 required for entry; P≤0.05 required to be retained). Predictors considered for the model included door-to-CT time and all baseline characteristics (VSA was not included as a variable because door-to-CT was a major change within the VSA).
Streamlined Protocol Resulting From the VSA
The VSA identified several barriers preventing rapid tPA treatment including: (1) inefficient patient flow, requiring a patient to be routed by emergency medical services to the trauma bay, then to CT, then back to the room; (2) serial processing of multiple tasks and inefficient use of available staff; and (3) delays in laboratory processing in patients suspected of being on anticoagulation (Figure). After the VSA, the streamlined acute stroke protocol addressed these sources of waste at the same time as retaining value-added steps (Figure): (1) patients were taken directly to the CT scanner by emergency medical services and then brought to the trauma bay; (2) the ED and neurology residents were assigned distinct and parallel tasks: obtaining the brief history and performing the National Institutes of Health Stroke Scale; a pharmacist and social worker were added to the team to calculate and prepare tPA dose and bring witnesses to the bedside (or by phone) for physicians to determine time of onset; and (3) point-of-care testing for international normalized ratio was implemented.
In the pre-VSA and post-VSA epochs, 132 and 87 patients with ischemic stroke were treated with intravenous tPA, respectively (Table 1). Shorter onset-to-arrival time and arrival “off-hours” (Friday 5 pm to Monday 7 am) have been associated with longer tPA delivery and did not differ between the 2 cohorts.2,4,8
Protocol Metrics and Clinical Outcomes
Compared with pre-VSA, DNTs and percent of patients treated ≤60 minutes from hospital arrival were improved post-VSA: 60 minutes versus 39 minutes (P<0.0001) and 52% versus 78% (P<0.0001), respectively (Table 2; online-only Data Supplement I through V). After adjustment for imbalanced baseline characteristics, the post-VSA epoch continued to demonstrate significantly lower DNTs (F=32.4, P<0.0001). The frequency distribution shifted to shorter DNTs post-VSA with fewer outliers beyond 100 minutes (online-only Data Supplement V). DNT improvement also translated to improved onset-to-needle times (P=0.016).
To determine if improved DNTs were sustained throughout the post-VSA year and were not initially reduced due to the novelty of the protocol, the quarterly DNTs were compared and did not differ across the year (P=0.88; online-only Data Supplement I). Moreover, the volume of tPA-treated patients did not appear to adversely affect DNTs because a consistent increase in volume was seen in the post-VSA epoch (online-only Data Supplement II).
As head CT became the first step in the protocol, door-to-CT times were lower post-VSA (P<0.0001). To determine if routing patients directly to CT contributed to lower DNTs, linear regression for prediction of DNT was performed. The final model included door-to-CT time (regression coefficient, β [SE]=0.76 [0.20]; P<0.0001) and onset-to-arrival time (β [SE]=−0.098 [0.046]; P=0.035). Thus, shorter door-to-CT and longer onset-to-arrival times were associated with shorter DNTs.
To determine if the protocol’s efficiency was at the expense of patient safety, clinical outcomes were compared. There were no differences in symptomatic intracerebral hemorrhage, discharge location, 90-day modified Rankin Scale, length of hospital stay, or stroke mimic rate between the 2 epochs.
The current study examined the application of “lean” toward quality improvement for expediting tPA administration at an urban, tertiary care hospital. With key members of the stroke team present at a 2-day VSA, several unnecessary and redundant operations were identified and eliminated, leading to lower DNTs with 78% of patients receiving tPA within 1 hour of hospital arrival. Post-VSA, the tPA frequency distribution shifted left on the time axis and became more narrowly distributed with fewer outliers, suggesting not only shorter treatment times, but also less variability in treatment times (online-only Data Supplement V). This protocol change did not compromise patient safety, because symptomatic intracerebral hemorrhage rates and clinical outcomes did not differ.
Our data suggest that removing the additional transportation step (having emergency medical services route patients directly to head CT; Figure) played a large role in the shorter DNT post-VSA (Table 2; linear regression model showing door-to-CT times independently predicted DNTs). Another variable that predicted shorter DNTs was greater onset-to-arrival times, which has been found in several large intravenous tPA data sets2,4 and indicates an additional educational opportunity to avoid “exhausting” the tPA window when a patient arrives early.
These data come from a single center with small patient numbers, thus limiting our ability to detect potential differences in clinical outcomes. Although the majority of data were prospectively collected, historical controls were used for the comparison cohort, and time-dependent variables unrelated to protocol changes could affect results. The stroke mimic rate did not significantly differ between the 2 cohorts but was 11.5% post-VSA with increased diagnoses due to conversion disorder (online-only Data Supplement III). Although within the range of other studies reporting stroke mimic rates in tPA-treated patients,9–11 expediting tPA may increase the number of stroke mimics treated and warrants continued monitoring of clinical outcomes and rate of symptomatic intracerebral hemorrhage. Of note, both pre- and post-VSA stroke mimic rates may appear falsely low because some physicians may be reluctant to change the discharge diagnosis to stroke mimic if the patient has been treated with tPA.
Lean manufacturing principles were applied to expedite intravenous tPA delivery with dramatic reduction in DNTs and without compromising patient safety. Future studies may determine if this intervention is sustainable across various hospital settings.
We acknowledge the Washington University neurology and ED residents, Barnes -Jewish Hospital ED nurses, radiology, and patient care technicians, and the St Louis area emergency medical service providers. We acknowledge Brian Hoff, Lean Performance Engineer at Barnes-Jewish Hospital, for reviewing the article for overall accuracy with regard to lean process improvement.
Sources of Funding
This study was supported by NIHK23NS069807 to Dr Ford, the Specialized Programs of Translational Research in Acute Stroke (SPOTRIAS) grant, NIH5P50NS055977, to Dr Lee and Dr Panagos and the Institute of Clinical and Translational Sciences at Washington University, UL1 TR000448.
↵* Drs Panagos and Lee contributed equally.
The online-only Data Supplement is available with this article at http://stroke.ahajournals.org/lookup/suppl/doi:10.1161/STROKEAHA.111.670687/-/DC1.
- Received July 18, 2012.
- Accepted August 21, 2012.
- Final version accepted August 24, 2012.
- © 2012 American Heart Association, Inc.
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