Dyspnea in the ambulance - etiology, mortality, and point-of-care diagnostics

Morten Thingemann Bøtker

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling

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Abstract

Background
Dyspnea is a distressing subjective sensation of difficult,
labored, or uncomfortable breathing that can be caused
by a range of diseases – including heart and pulmonary
diseases. Patients suffering dyspnea in the ambulance
have a high risk of death compared to other patients that
are highly prioritized in emergency medical services –
including chest pain and trauma. Whether this increased
mortality can be ascribed to an older age and comorbidity
among patients suffering dyspnea, or if modifiable risk
factors are also present, is unsettled. Improving outcome
for patients suffering dyspnea in the ambulance requires
identification of high-risk groups and early correct
treatment. Bringing forward simplified versions of
advanced diagnostic modalities known from the hospital
as point-of-care diagnostics already in the ambulance may
aid the discrimination of underlying conditions causing
dyspnea and improve patient management and ultimately
outcome.

Aims
The aims of this thesis were 1) to compare mortality
among patients suffering dyspnea and other symptoms in
the prehospital setting, 2) to clarify whether the high
mortality in patients suffering dyspnea when compared
to patients with other symptoms in the ambulance are
due to unmodifiable patient characteristics only, 3) to
identify high-risk groups among those suffering dyspnea,
4) to evaluate the electrocardiogram-based telemedicine
in the ambulance for identification high-risk patients and
5) to evaluate whether addition of a point-of-care
examination for heart failure improves management of
patients suffering dyspnea because of heart disease
beyond usual care.

Methods
The thesis includes two register-based studies (Part 1)
and one interventional study (Part2). In Part 1, the risk of
death in patients suffering dyspnea was compared to that
in patients suffering chest pain and other symptoms in
two different patient populations. In the first study, we
included patients suspected of myocardial infarction and
undergoing electrocardiogram-based telemedical triage in
an ambulance in the Central Denmark region. In the
second study, we included all patients dialing the
emergency number (1-1-2) due to a medical emergency in
three of five Danish regions. For identification of highrisk
patients and evaluation of electrocardiogram-based
triage, we compared short-term mortality between
patients included in the first study based on the
interpretation of their electrocardiogram. In addition, we
compared short-term mortality between patients
diagnosed with different heart, lung, and other diseases
among patients included in the second study.
In Part 2 we conducted a randomized controlled study
examining whether addition of point-of-care N-terminal
pro-brain natriuretic peptide (NT-proBNP) measurement
to the routine diagnostic work-up by prehospital
physician improved triage and treatment of patients with
dyspnea caused by heart disease

Results and conclusion
Patients suffering dyspnea in the ambulance had higher
risk of death than any other group of patients in the
ambulance except patients resuscitated from cardiac
arrest in study 1 and unconscious/cardiac arrest patients
in study 2. The differences were independent of patient
age and underlying diseases, indicating a potential for
improving outcome among patients suffering dyspnea in
the ambulance. Electrocardiographic assessment leading
to suspicion of ST-elevation myocardial infarction or
bundle branch block myocardial infarction was useful for
identification of a small group of patients with very high
risk of death, emphasizing the importance of obtaining
an electrocardiogram in patients suffering dyspnea at any
doubt about the underlying cause. Patients suffering
heart failure, pneumonia and in particular those suffering
sepsis were identified as high-risk patients with potential
for improvement. A large group of patients with dyspnea
of other causes may contain subgroups of patients with
high-risk where outcome can be improved.
Supplementing the routine diagnostic work-up by
prehospital physician with NT-pro-BNP did not improve
management, treatment or patient outcome, but seemed
to improve rule-out of heart disease and rule-in of lung
disease. Other initiatives to facilitate a systematic
approach to diagnosis and treatment in patients suffering
dyspnea in the ambulance are warranted.
OriginalsprogEngelsk
StatusUdgivet - 14 okt. 2016

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