5.
Prehospital Issues
5.1. Emergency Medical Services Systems
Class I
1. All EMS first responders who respond to patients with
chest pain and/or suspected cardiac arrest should be trained and
equipped to provide early defibrillation. (Level of Evidence:
A)
2. All public safety first responders who respond to patients with
chest pain and/or suspected cardiac arrest should be trained and
equipped to provide early defibrillation with AEDs. (Provision of
early defibrillation with AEDs by non–public safety first
responders is a promising new strategy, but further study is needed
to determine its safety and efficacy.) (Level of Evidence: B)
3. Dispatchers staffing 9-1-1 center emergency medical calls should
have medical training, should use nationally developed and maintained
protocols, and should have a quality-improvement system in place
to ensure compliance with protocols. (Level of Evidence: C)
EMS systems vary considerably among communities in their ability
to evaluate and treat suspected patients with STEMI, with some providing
little beyond first aid and early defibrillation, whereas others
have highly trained paramedics with sophisticated technology and
advanced protocols.
EMS systems have 3 traditional components: emergency medical dispatch,
first response, and EMS ambulance response.
Emergency Medical Dispatch. Early access to EMS is promoted
by a 9-1-1 system currently available to more than 90% of the United
States population. Enhanced 9-1-1 systems provide the caller’s
location to the dispatcher, which permits rapid dispatch of prehospital
personnel to locations even if the caller is not capable of verbalizing
or the dispatcher cannot understand the location of the emergency.
A major challenge is the widespread proliferation and use of cell
phones. Current cell phone technology does not provide the location
of the caller to an enhanced 9-1-1 center. Instead, such calls are
usually answered by the state police, who then attempt to determine
the location of the emergency and forward the call to the appropriate
9-1-1 center. Such additional steps often result in substantial
delays in the dispatch of emergency units to the scene. Several
technological solutions to this problem exist but have not yet been
implemented by the cell phone industry. EMS healthcare workers should
encourage enhanced cell phone technology to identify caller location
on 9 1-1 systems.
In
most communities, law enforcement or public safety officials are
responsible for operating 9-1-1 centers, because in most locations,
85% of calls are for police assistance, 10% are for EMS, and 5%
are for fire-related emergencies. Dispatchers who staff 9-1-1 centers
typically have only minimal medical background and training and
usually operate by following written cards and protocols that in
many cases are designed and updated locally. High-performance centers
employ EMTs and/or paramedics who are specially trained and certified
as emergency medical dispatchers. They, too, operate under written
protocols, but such protocols are usually developed and upgraded
at the national level. Such centers typically have intense quality-assurance
programs to ensure that emergency medical dispatchers follow protocols
and procedures correctly and consistently. This is particularly
true for the prearrival instructions that are given to cardiac arrest
bystanders to instruct them on how to perform CPR while awaiting
arrival of emergency personnel (phone CPR) (136).
Efforts to shorten the time for contact of the STEMI patient with
the medical system are likely to require expansion of the number
of trained emergency response personnel and consideration of streamlining
methods for distinguishing emergency calls for medical assistance
from other emergencies using separate phone numbers, as is the practice
currently in some European countries.
First
Response. To minimize time to treatment, particularly for cardiopulmonary
arrest, many communities allow volunteer and/or paid firefighters
and other first-aid providers to function as first responders, providing
CPR and, increasingly, early defibrillation using AEDs until EMTs
and paramedics arrive. AEDs have been shown to be safe and effective
when used by trained first responders with a duty to act (137-139).
Systems that incorporate AEDs to shorten response times are highly
desirable. Ideally, there should be a sufficient number of trained
personnel so that a trained first responder can be at the victim’s
side within 5 minutes of the call.
Another
popular community approach to increase the number of out-of-hospital
VF patients who receive early defibrillation is public access defibrillation
(PAD), so named because the intent is to have laypersons perform
early defibrillation. Experience thus far has been favorable in
terms of efficacy and safety when trained public safety laypersons
(e.g., flight attendants or security officers) have been allowed
to use AEDs to treat cardiac arrest victims (131,140,141).
Provision of early defibrillation with AEDs by non–public
safety first responders is a promising new strategy to prevent sudden
cardiac death after the onset of STEMI, but further study is needed
to determine its safety and efficacy (142-147)
(Ornato JP; oral presentation, American Heart Association 2003 Annual
Scientific Sessions, November 2003, Orlando, FL).
EMS
Ambulance Response. Most cities and larger suburban areas provide
EMS ambulance services with providers from the fire department,
a private ambulance company, and/or volunteers. The most common
pattern is a tiered system in which some of the ambulances are staffed
and equipped at the basic EMT level (which includes first aid and
early defibrillation with AEDs) and other units (either transporting
or nontransporting) are staffed by paramedics or other intermediate-level
EMTs (who can, in addition to basic care, start intravenous [IV]
drips, intubate, and administer medications).
In some systems, the advanced providers can also perform 12-lead
ECGs, provide external pacing for symptomatic bradycardia, and utilize
other techniques. Some high performance EMS systems have only advanced
life support–staffed ambulances (all-ALS systems). Advantages
of such systems are that they provide a uniform standard of care
and, surprisingly, can actually lower cost by eliminating the need
to dispatch 2 units in response to calls in which it is not clear
to dispatchers initially that the patient needs advanced life support
(149). The potential disadvantage
of such models is that they typically have a relatively large number
of paramedics, each of whom gets to perform their advanced skills
less frequently than the smaller number of paramedics typically
found in tiered systems (150).
Rural areas typically provide primarily basic life support ambulance
services, usually by volunteers supplemented by a relatively small
number of ALS units. In some cases, ALS is provided by paramedics
or helicopter personnel who respond to the scene in addition to
the basic life support ambulance.
5.2. Prehospital Chest Pain Evaluation
and Treatment
Class I
Prehospital EMS providers should administer 162 to 325 mg
of aspirin (chewed) to chest pain patients suspected of having STEMI
unless contraindicated or already taken by the patient. Although
some trials have used enteric-coated aspirin for initial dosing,
more rapid buccal absorption occurs with non–entericcoated
formulations. (Level of Evidence: C)
Class IIa
1. It is reasonable for all 9-1-1 dispatchers to advise patients
without a history of aspirin allergy who have symptoms of STEMI
to chew aspirin (162 to 325 mg) while awaiting arrival of prehospital
EMS providers. Although some trials have used enteric-coated aspirin
for initial dosing, more rapid buccal absorption occurs with non–enteric-coated
formulations. (Level
of Evidence: C)
2. It is reasonable that all ACLS providers perform and evaluate
12-lead ECGs routinely on chest pain patients suspected of STEMI.
(Level of Evidence: B)
3. If the ECG shows evidence of STEMI, it is reasonable that prehospital
ACLS providers review a reperfusion “checklist” and
relay the ECG and checklist findings to a predetermined medical
control facility and/or receiving hospital. (Level of Evidence:
C)
Because the potential benefits of early aspirin use are great and
the risks and costs are low, it is reasonable for physicians to
encourage the prehospital administration of aspirin via EMS personnel
(i.e., EMS dispatchers and providers) to patients with symptoms
suggestive of STEMI unless its use is contraindicated (151).
The AHA chest pain algorithm can be adapted for use by prehospital
emergency personnel. This protocol
recommends empirical treatment of patients with suspected STEMI
with Morphine, Oxygen, Nitroglycerin, and Aspirin (MONA) (102).
Although short-acting nitroglycerin is often administered for temporary
symptomatic relief, it can precipitate hypotension (especially if
right ventricular [RV] infarction is present), and long-term nitrates
have not been shown to decrease mortality in patients with STEMI
(152). To facilitate earlier aspirin
administration, it is reasonable that 9-1-1 dispatchers advise non–aspirin-allergic
patients with symptoms of STEMI to chew 162 to 325 mg of aspirin
while awaiting arrival of prehospital EMS providers. In the absence
of instructions by emergency medical dispatchers, prehospital EMS
providers (under medical direction) should administer an aspirin
en route to the hospital as noted above. Although some trials have
used enteric-coated aspirin for initial dosing, more rapid buccal
absorption occurs with non–enteric-coated formulations.
The
AHA (102), the 31st Bethesda Conference
of the American College of Cardiology (153),
and a technology review supported by the NHLBI’s NHAAP (154)
strongly encourage the use of 12-lead ECGs by paramedics to evaluate
all patients with chest discomfort suspected to be of ischemic origin
in the prehospital setting (Figure
6) (Table 3) (155).
This requires providing training and 12-lead ECG equipment to all
ACLS personnel.
For patients who have ECG evidence of STEMI, it is reasonable that
paramedics review a reperfusion checklist and relay the ECG and
checklist findings to a predetermined medical control facility and/or
receiving hospital (Table 3). The
checklist should be designed to determine the presence or absence
of comorbid conditions and underlying conditions in which fibrinolytic
therapy may be hazardous. The checklist should also facilitate detection
of patients with suspected STEMI who are at especially high risk
(see Table 3), including those with
severe heart failure or cardiogenic shock, for whom primary PCI
is generally the preferred reperfusion strategy. (See Section
6.3.1.6.4.2.)
Active involvement of local healthcare providers, particularly cardiologists
and emergency physicians, is needed to formulate local EMS protocols
for patients with suspected STEMI, provide training, and secure
equipment. In the future, regional centers of excellence for care
of patients with STEMI may facilitate improvement of EMS protocols
(56-58).
5.3. Prehospital Fibrinolysis
Class IIa
Establishment of a prehospital fibrinolysis protocol is
reasonable in 1) settings in which physicians are present in the
ambulance or 2) well-organized EMS systems with full-time paramedics
who have 12-lead ECGs in the field with transmission capability,
paramedic initial and ongoing training in ECG interpretation and
STEMI treatment, on-line medical command, a medical director with
training/ experience in STEMI management, and an ongoing continuous
quality-improvement program. (Level of Evidence: B)
The
selection of reperfusion strategy is discussed in Section
6.3.1.6.2 and involves assessment of the time from onset of
symptoms, risk of STEMI, risk of bleeding, and the time required
for transport to a skilled PCI lab. This section discusses issues
related to prehospital fibrinolysis, which may bear on the timing
and selection of reperfusion therapy.
Randomized
controlled trials of fibrinolytic therapy have demonstrated the
benefit of initiating fibrinolytic therapy as early as possible
after onset of ischemic-type chest discomfort (155-157)
(Figure 6). It seems reasonable
to expect that if fibrinolytic therapy could be started at the time
of prehospital evaluation, a greater number of lives could be saved.
In Assessment of the Safety and Efficacy of a New Thrombolytic Regimen
(ASSENT)-3, 53% of patients received prehospital fibrinolysis within
2 hours after symptom onset (158).
The value of reducing delay until treatment depends not only on
the amount of time saved but also on when it occurs. Available data
suggest that time saved within the first 1 to 2 hours has greater
biological importance than time saved during the later stages of
STEMI (156,157,159-164).
Several randomized trials of prehospital initiated fibrinolysis
have advanced our understanding of the impact of early treatment
(Table 4) (159,165-174).
Acquisition of 12-lead ECGs in the field and use of a reperfusion
checklist (Table 3) lead to more
rapid prehospital and hospital care (159,175).
Although none of the individual trials showed a reduction in mortality
with prehospital-initiated fibrinolytic therapy, a meta-analysis
of all available trials (before the Comparison of Angioplasty and
Prehospital Thrombolysis in Acute Myocardial Infarction trial [CAPTIM],
which was performed after the meta-analysis) (173)
demonstrated a 17% relative improvement in outcome associated with
prehospital fibrinolytic therapy compared with in-hospital fibrinolytic
therapy (95% CI 2% to 29%) (171).
In the CAPTIM trial, patients randomized less than 2 hours after
symptom onset had a strong trend toward lower 30-day mortality with
prehospital fibrinolysis than did those randomized to primary PCI
(2.2% versus 5.7%, p equals 0.058) (176).
Similarly, patients in PRimary Angioplasty in patients transferred
from General community hospitals to specialized PTCA Units with
or without Emergency thrombolysis (PRAGUE-2) who were randomized
within 3 hours of symptom onset (n equals 551) had no difference
in mortality whether treated by fibrinolysis (7.4%) or transferred
for PCI (7.3%) (177). Systems that
have extensive experience with prehospital fibrinolysis with physician
attendance in the ambulance and a well-integrated mechanism for
obtaining and transmitting a 12-lead ECG continue to show excellent
short- and long-term mortality results with prehospital fibrinolysis.
Using data from a national registry, investigators in France reported
1-year mortality from STEMI of 6% in patients receiving prehospital
fibrinolysis compared with 11% in patients receiving inhospital
fibrinolysis or primary PCI; the survival difference in favor of
prehospital fibrinolysis persisted after adjustment for baseline
characteristics (Danchin N; oral presentation, American Heart Association
2003 Annual Scientific Sessions, November 2003, Orlando, FL).
The
difference between time to fibrinolytic therapy in the prehospital
setting versus the hospital setting can be minimized by improved
hospital triage with a decrease in doorto-needle time to within
30 minutes (179) (Figure
7) (180). However, only a small
percentage (5% to 10%) of patients with chest pain in the prehospital
setting have STEMI and are eligible for fibrinolytic therapy (159,181,182).
Ensuring proper selection of patients for therapy can be difficult,
and administration of therapy when it is contraindicated has important
medical, legal, and economic implications. For these reasons, a
general national policy of prehospital fibrinolytic therapy cannot
currently be advocated. Prehospital fibrinolysis is reasonable in
those settings in which physicians are present in the ambulance
or prehospital transport times are more than 60 minutes in high-volume
(more than 25 000 runs per year) EMS systems (102).
Other
considerations for implementing a prehospital fibrinolytic service
include the ability to transmit ECGs, paramedic initial and ongoing
training in ECG interpretation and MI treatment, online medical
command, and the presence of a medical director with training/experience
in management of STEMI and full-time paramedics (183).
An example of the time saved by prehospital fibrinolysis is illustrated
in a report from Scotland. The National Health Service in the United
Kingdom established the standard that patients thought to be suffering
from STEMI should receive fibrinolysis within 60 minutes of calling
for medical assistance (http://www.doh.gov.uk/nsf/coronarych3.htm).
Three groups of patients in Scotland were studied: group 1 consisted
of patients (n equals 107) within an urban area who received fibrinolytic
therapy in the hospital, group 2 consisted of patients (n equals
43) from rural areas who received fibrinolytic therapy in the hospital,
and group 3 consisted of patients (n equals 28) in a rural area
who received fibrinolytic therapy (tenecteplase) in the ambulance
by trained paramedics who were supervised by a medical control officer
(183). Administration of prehospital
fibrinolytic therapy resulted in a median time savings of 73 minutes
compared with patients from rural areas and 28 minutes compared
with patients from urban areas (p less than 0.001). A greater proportion
of patients who received prehospital fibrinolytic therapy
were in compliance with the National Health Service standard of
“call-to-needle” of 60 minutes (Figure
8) (183).
5.4. Prehospital Destination Protocols
Class I
1. Patients with STEMI who have cardiogenic shock and are less than
75 years of age should be brought immediately or secondarily transferred
to facilities capable of cardiac catheterization and rapid revascularization
(PCI or CABG) if it can be performed within 18 hours of onset of
shock. (Level of Evidence: A)
2. Patients with STEMI who have contraindications to fibrinolytic
therapy should be brought immediately or secondarily transferred
promptly (i.e., primaryreceiving hospital door-to-departure time
less than 30 minutes) to facilities capable of cardiac catheterization
and rapid revascularization (PCI or CABG). (Level of Evidence:
B)
3. Every community should have a written protocol that guides EMS
system personnel in determining where to take patients with suspected
or confirmed STEMI. (Level of Evidence: C)
Class
IIa
1. It is reasonable that patients with STEMI who have cardiogenic
shock and are 75 years of age or older be considered for immediate
or prompt secondary transfer to facilities capable of cardiac catheterization
and rapid revascularization (PCI or CABG) if it can be performed
within 18 hours of onset of shock. (Level of Evidence: B)
2. It is reasonable that patients with STEMI who are at especially
high risk of dying, including those with severe congestive heart
failure (CHF), be considered for immediate or prompt secondary transfer
(i.e., primary-receiving hospital door-to-departure time less than
30 minutes) to facilities capable of cardiac catheterization and
rapid revascularization (PCI or CABG). (Level of Evidence: B)
Every community should have a written protocol that guides EMS system
personnel in determining where to take patients with suspected or
confirmed STEMI. Active involvement of local healthcare providers,
particularly cardiologists and emergency physicians, is needed to
formulate local EMS destination protocols for these patients. In
general, patients with suspected STEMI should be taken to the nearest
appropriate hospital. However, patients with STEMI and shock are
an exception to this general rule (Table
3).
Emergency revascularization improves 1-year survival in patients
with STEMI complicated by cardiogenic shock (184).
Subgroup analysis suggested a differential treatment effect, with
the clearest benefit for those under 75 years of age. Therefore,
whenever possible, patients with STEMI less than 75 years of age
with shock should be transferred to facilities capable of cardiac
catheterization and rapid revascularization (PCI or CABG). On the
basis of observations in the SHOCK Trial Registry and other registries,
it is reasonable to extend such considerations of transfer to invasive
centers for elderly patients with shock (see Section
7.6.5). Patients with STEMI who have contraindications to fibrinolytic
therapy and an especially high risk of dying, including severe CHF
or cardiogenic shock, should be brought immediately or secondarily
transferred promptly (i.e., primary-receiving hospital door-to-departure
time less than 30 minutes) to facilities capable of cardiac catheterization
and rapid revascularization (PCI or CABG). Given the importance
of avoiding delays in time to reperfusion (see Section
6.3.1.6.3.1), direct transport to a facility capable of rapid
revascularization is strongly preferred to interhospital transfer.
|
