Helicopter Transfer Offers a Potential Benefit to Patients With Acute Stroke
Background and Purpose—Rapid transport of patients to specialized centers is widely used in the management of myocardial infarction, trauma, and more recently, acute stroke. We evaluated the role of helicopter transportation as it relates to the availability of acute stroke therapies and patients’ perceptions of care.
Methods—We reviewed records of all patients transferred to a university hospital within 24 hours of stroke onset from January 1996 to December 1997. Data were collected on demographics, neurological deficit, treatment, and outcome. In addition, a questionnaire was sent to all patients with items about perceived reasons for helicopter transfer, expected and actual treatment, outcome, and overall impression.
Results—Helicopter transfer was used for 73 stroke patients. Before transfer, 8 patients (11%) received tissue plasminogen activator (tPA). On arrival, no patient received tPA, 38 patients (52%) were enrolled in acute stroke studies, and 35 patients (48%) received no specific medication. All but 2 patients were managed in a specialized stroke unit. Of the 35 patients who received no specific therapy, 24 (69%) were ineligible for treatment or study enrollment owing to 1 or more exclusion criteria, but rarely (3%) because of time. Of the 45 respondents to the survey, most (84%) were transferred at the suggestion of the physician at the originating hospital because of a possible treatment that was unavailable there. Most patients (93%) believed that there was a benefit from emergent helicopter transfer to a stroke center, although 40% of respondents received no specific therapy.
Conclusions—Interhospital transfer by air may benefit a substantial number of acute stroke patients by offering potential therapies and intensive management not available elsewhere.
The treatment of acute ischemic stroke is an exquisitely time-dependent process. Although the merit of many of the innovative treatment strategies remains unproven and the extent of the potential therapeutic time window is uncertain, it is widely agreed that early treatment is essential. The only approved therapy is intravenous tissue plasminogen activator (tPA), which must be given within 3 hours of stroke onset.1 However, many hospitals do not offer such therapy or may not have the neurointensive care services to support patients after they have been given tPA.2 Trials of experimental drugs for acute stroke therapy are usually only available in experienced stroke centers and also have narrow time windows. Therefore, community hospitals often transfer acute stroke patients to tertiary-care centers for further management. Transportation of medical patients by air is widely used in the management of acute myocardial infarction and trauma.3 4 5 6 Although the impact of this practice on clinical outcome remains controversial, the speed of air versus ground transport is believed to offer an advantage in management.6 The use of helicopters for stroke patients may be increasing, although no data exist to demonstrate its utility. The expense may be prohibitive,3 and patients may be responsible for a major portion of the transportation costs if their insurance carriers deem the transfer to be unjustified.
It is difficult to compare the care provided to patients who are transferred from primary- to tertiary-care centers with the care given to those who remain at primary-care centers, because the underlying characteristics of the patients and the severity of their disease may differ dramatically. Furthermore, an evaluation of helicopter and ambulance transfers to address their relative safety and efficacy would also be severely biased by the unmeasurable differences in stroke severity and acuity between patients transported by either method. A randomized study to address these issues might also be considered unethical because of the risks of delayed therapy. Our study therefore examines only transfer by helicopter to evaluate its efficiency in terms of patient treatment and perceived utility in terms of patient satisfaction.
Subjects and Methods
This retrospective case series was performed at a university hospital after review and approval by the institutional review board were obtained.
Stroke patients were selected and triaged for transfer to the university hospital on the basis of a telephone conversation between the referring physician at the community hospital and the neurologist at the university hospital. Inquiries were made about the severity of symptoms, time of onset, and other relevant medical history. The decision of whether to accept the patient for transfer was then made based on the availability of a treatment or experimental protocol that could possibly benefit the patient.
We included all patients transferred with a diagnosis of acute ischemic stroke within 24 hours of the onset of symptoms between January 1996 and December 1997. Ninety patients were identified by a review of both the helicopter transfer log and the neurology/stroke inpatient log, and all of the medical records for these patients were reviewed. Twelve patients were referred to the university hospital for ongoing tertiary care between 2 and 5 days after the onset of symptoms rather than for early management and were therefore excluded from the study. Four additional patients with a diagnosis of subarachnoid or intracerebral hemorrhage (diagnosed before transfer) were erroneously recorded as ischemic stroke and were also excluded. In 1 additional patient, we were unable to determine the timing of symptom onset relative to the transfer from the medical record. Seventy-three patients remained eligible for this study.
Medical records were reviewed in detail and abstracted for demographic information, insurance status, comorbid medical illnesses (including previous history of cerebrovascular disease), baseline neurological status, treatment, outcome, and stroke subtype (according to the TOAST [Trial of Org 10172 in Acute Stroke Treatment] classification).7 Baseline neurological status was assessed by use of the National Institutes of Health Stroke Scale (NIHSS), either as recorded in the chart or as estimated by the chart reviewer from the reported neurological examinations on admission and discharge.8 Potential interventions included treatment with tPA within the 3-hour time window, other thrombolytic protocols, neuroprotective clinical trials, and admission to the stroke unit. For patients who received no specific therapy other than use of the stroke unit, we identified the reason for failure to treat or enroll in a clinical trial.
We sent a questionnaire to the patients to assess their reactions to the helicopter transfer. The questionnaire was pretested in other stroke patients to assess readability and content validity and was revised accordingly. The questionnaire was also sent to a family member or other proxy for each patient who was involved in the process of interhospital transfer at the time of the stroke. We sent a total of 3 questionnaire mailings to maximize the rate of response. The questionnaire asked about prior knowledge of potential stroke treatments, how the decision to make a helicopter transfer was made, what type of treatment was expected at the university hospital, and the overall impression of treatment received and of the helicopter transfer (Table 1⇓; full questionnaire available on request from the corresponding author). If only 1 of these 2 questionnaires was returned, it was used in all analyses. If both were returned, they were compared to determine the reliability between responses by patients and proxies, but only the patient’s response was used in further analyses. Interrater reliability for patient and proxy responses to each question was measured with the κ statistic.
Statistical analysis was performed with Stata version 5.0 (Stata Corporation). Bivariate comparisons between questionnaire respondents and nonrespondents were made with χ2 or Student’s t tests, as appropriate.
The characteristics of the 73 ischemic stroke patients transferred by helicopter and included in the study are summarized in Table 2⇓. All of the patients were diagnosed with stroke or transient ischemic attack. There were no patients who were found to be misdiagnosed with a cerebrovascular syndrome before transfer. The mean age was 62 years, and 55% of the patients were male. Initial symptoms ranged from mild to very severe according to the NIHSS, but small-vessel (lacunar) strokes were relatively underrepresented (12%) compared with larger cohorts of patients with acute ischemic stroke.1 9
Based on comparison of NIHSS scores on admission and discharge, 22% percent of patients showed clinical improvement during the hospitalization, 53% of patients had no significant change in their clinical condition, and 25% of patients worsened or died. The overall in-hospital mortality rate was 18%.
Thirty patients and 42 proxies responded to the questionnaire, with 27 sets of responses from both patient and proxy. In total, 45 (62%) of the 73 patients were represented in the survey. There were no differences between patient and proxy responses when both were returned (κ between 0.6 and 0.9 for all questions, which indicates good to excellent agreement), so proxy responses were assumed to be representative of the patient response if only the proxy response was returned. Characteristics of respondents and nonrespondents are summarized in Table 2⇑. Respondents and nonrespondents to the questionnaire were similar in terms of age, sex, NIHSS score on arrival, vascular territory of stroke, and stroke subtype. Respondents and nonrespondents received similar acute management on arrival at the university hospital. In addition, there was no significant difference between the 2 groups in NIHSS scores at discharge or in mortality.
Use of Helicopter
Stroke patients traveled between 12 and 90 nautical miles between hospitals, with in-flight times between 6 and 45 minutes. Typical ground transport times for these hospitals range from 30 to 150 minutes, respectively.
Of the 45 respondents to the questionnaire, 39 (87%) reported that the decision to transfer was made by the doctor at the referring hospital, and only 5 (11%) were transferred at their or their family’s request. For 34 patients (76%), the apparent reason for transfer was because of a possible treatment that was not available at the referring hospital, whereas the remainder were transferred because of hospital reputation or prior care of the patient at the university hospital.
Of the 45 respondents, 12 (27%) expected to receive treatment with tPA or a “clot buster,” 14 (31%) expected to be enrolled in a study drug protocol, 2 (4%) only expected care in a specialized stroke unit, and 17 (38%) did not know what type of treatment they expected to receive. Of the 73 patients transferred, 8 (11%) received tPA before transfer. On arrival, no patient received tPA, 38 (52%) were enrolled in acute stroke study drug protocols, and 35 patients (48%) received neither thrombolytics nor experimental therapies. All but 2 patients were managed in a specialized stroke unit. Of the 65 patients who did not receive tPA, 40 (62%) arrived >3 hours after the onset of symptoms, 15 (23%) failed to meet eligibility criteria, and 6 (9%) patients had complete or near-complete resolution of the deficit within 3 hours. Only 1 (2%) eligible patient refused treatment with tPA. Reasons could not be identified in the remaining 3 patients (5%). Of the 35 patients who received neither tPA nor a study drug, 24 (69%) failed to meet eligibility criteria, 5 (14%) had complete or near-complete resolution of symptoms, 1 (3%) refused to be in a study, 1 (3%) did not arrive in time, and for 4 patients (11%), the reason could not be determined from chart review.
Among the 45 respondents to the questionnaire, 42 (93%) believed that they benefited from emergent transfer and the treatment they received after transfer, although 18 (40%) of these patients received neither tPA nor study drug. Because the overwhelming majority of patients reported a benefit, further analysis to determine the factors that contributed to perception of benefit could not be performed.
The benefit of helicopter transfer has been studied extensively in cardiac and trauma patients; helicopter transfer been found to reduce time to definitive treatment and specialized care, and it may improve patient outcome.6 10 Helicopters are able to fly a direct route between hospitals at ≈120 mph (200 km/h), although they may be unable to fly in inclement weather.6 Ambulances can only travel at the legal speed limit and may be constrained by indirect routes, traffic congestion, road conditions, and inclement weather.6 The potential advantage of helicopter transfer is therefore considerable for stroke patients, because treatment is extraordinarily time dependent.
The use of helicopters to transfer stroke patients in rural areas was recently evaluated and found to increase the availability of thrombolytic therapy for patients transferred from moderate distances.11 In the present study, no patient received tPA within the approved 3-hour time window after transfer. Despite the rapidity of helicopter transport, the major obstacle to tPA administration after transfer was time. We were unable to ascertain the reasons that patients did not receive tPA at the originating hospital. It seems unlikely that helicopter transfer will make tPA available for many more patients. Eligible patients should be appropriately treated with proven and approved therapies as early as possible and should not require transfer to a university setting solely for the administration of tPA. However, tPA was initiated at the referring hospital before transfer in some patients, and we were able to assist in their acute management by providing specialized and dedicated neurointensive care services. In this small group, air transport of patients after administration of tPA appeared to be safe, but a larger sample is required for further study.
The majority of recent and ongoing stroke clinical trials require enrollment within 6 to 24 hours of symptom onset. We found that ≈50% of stroke patients transferred by helicopter to a university hospital were enrolled in a clinical trial of a drug that was not available at the referring community hospital. Although experimental protocols cannot be equated with proven therapies, they represent a potential adjunct to conservative stroke management and may have an effect on real and perceived outcomes. However, the fact that nearly half of the patients did not receive tPA or a study drug (usually because of time delays or ineligibility) suggests that the current system of telephone triage is relatively inefficient. Patient selection may be improved with the use of clinical acute stroke scales12 13 or computer and Internet-based telemedicine protocols.14 Eligibility for study protocols may be determined before transfer by specifically reviewing the inclusion and exclusion criteria, as well as by faxing the consent form to the patient and family at the referring hospital before transfer. These methods may improve the selection efficiency of interhospital transfer, but they may add a minor delay to the transfer process.
Patient satisfaction has recently been demonstrated to correlate with actual intensity of care and may be an indirect measure of patient outcome.15 In the present study, ≈50% of the patients received no specific acute therapy, and even among those enrolled in clinical trials, ≈50% may be assumed to have received placebo. Furthermore, only 22% of patients demonstrated improvement in the NIHSS on discharge. Nevertheless, an overwhelming majority of patients/proxies who responded to the questionnaire believed that they benefited from the helicopter transfer to a tertiary-care center. The respondents were similar to nonrespondents with regard to all measured characteristics, and they were therefore thought to adequately represent the total cohort. Although the reasons for this perception of benefit cannot be assessed directly, there is mounting evidence that admission to a stroke unit may reduce both disability and mortality.16
Our study was limited by its relatively small sample size, which prohibited us from performing additional subgroup analyses. Moreover, responses to the questionnaire could have been affected by recall bias, as well as by previous and subsequent experiences at the university hospital and the eventual health outcome of the patient. It is also likely that patients/proxies who consented to the initial transfer between hospitals probably had a relatively positive bias toward the university hospital, which further affects our findings. We attempted to assess patient satisfaction through a variety of questions and response options, but it may be difficult to accurately describe or quantify all of the possible elements that could influence a patient’s recall or feelings about the care received. Furthermore, because patients transferred by helicopter could not be compared with similar patients who remained at the originating hospital because of the inherent bias, the relative effectiveness of transfer could not be addressed.
In conclusion, helicopter transfer to tertiary-care hospitals with specialized stroke services can offer potential benefits for patients with acute ischemic stroke. Patients may receive not only advanced care but also potential therapies in the form of clinical trials that are not available at most community hospitals. In addition, most patients perceive a benefit related to helicopter transfer to a tertiary-care center.
The authors thank Susan Conroy for her support in the layout and design of the questionnaire and Colleen Walsh, Mary Elizabeth DeSanto, and Jaime McKeown for their assistance with survey administration.
- Received August 12, 1999.
- Revision received September 14, 1999.
- Accepted September 23, 1999.
- Copyright © 1999 by American Heart Association
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