The care provided by emergency medical services (EMS) varies widely in the United States. The Institute of Medicine report, “EMS at the Crossroads,” notes that an area of improvement for EMS is the need for more uniform quality care and the need to develop measures for EMS quality.¹ A major area of EMS quality that is difficult to measure is the prehospital protocols that EMS personnel follow while taking care of patients. These protocols vary widely between jurisdictions. In the state of California, EMS care is divided into 33 separate local EMS agencies (LEMSAs). These government agencies are a countywide or region-wide system of first responders and ambulance transporters that operate under one set of medical control policies.

We performed a literature review of the current evidence in the prehospital treatment of chest pain and augmented this review with guidelines from various national and international societies to create our evidence-based recommendations. We then compared the chest pain protocols of each of the 33 EMS agencies for consistency with these recommendations. The specific protocol components that we analyzed were use of supplemental oxygen, aspirin, nitrates, opiates, 12-lead electrocardiogram (ECG), ST segment elevation myocardial infarction (STEMI) regionalization systems, prehospital fibrinolysis and β-blockers.

Protocols for chest pain of suspected cardiac origin vary widely across the state of California. The evidence-based recommendations that we present for the prehospital diagnosis and treatment of this condition may be useful for EMS medical directors tasked with creating and revising these protocols.

Clinical Question

Does the prehospital administration of oxygen to patients with chest pain and normal oxygen saturations improve outcomes in cases of suspected acute coronary syndrome (ACS)?

Current Prehospital Treatment Recommendation

There is no evidence that the routine use of oxygen to patients with normal oxygen saturations provides any benefit, but may cause harm.

Level A Recommendations

We recommend against routine oxygen supplementation in normoxic patients (oxygen saturation of 94% or greater) with suspected ACS.⁹ We recommend using supplemental oxygen for those patients with suspected ACS and signs of heart failure or shock.⁹

Level B Recommendations

None given.

Level C Recommendations

Oxygen saturations should be titrated between 94%- 98% (consensus).

No Recommendation

N/A

Summary of Current Evidence

There have been few randomized controlled studies that have attempted to answer this question. A study in 1976 by Rawles et al. randomized patients to oxygen or air and found more deaths in the oxygen group, although not clinically significant.³ A more recent trial addressing this question was in 2012 by Ranchord et al. showing no difference in mortality between a titrated oxygen group and a high-flow oxygen group, but with a very small sample size.⁴ The ILCOR ACS guidelines in 2010 do not find sufficient evidence to support the use of oxygen in suspected ACS, but do not find evidence of harm.⁵ A meta-analysis by Cochrane review (updated in 2013) showed no evidence of benefit and, in fact, showed possible harm with routine oxygen administration in suspected ACS, but noted that the analysis lacked the power to substantiate or refute the use of oxygen in these cases.⁶ A recent multicenter, prospective, randomized, controlled trial compared prehospital oxygen (8L/min) with no supplemental oxygen in patients with ST segment myocardial infarction (STEMI) and oxygen saturation of 94% or greater.⁷ The authors demonstrated that supplemental oxygen in this group increased early myocardial injury and was associated with larger myocardial infarct size and a higher rate of re-infarction. The DETO2X-AMI trial is ongoing and will examine this question among patients with suspected ACS and should be adequately powered to address this question.⁸

Clinical Question

Does the prehospital administration of aspirin to patients with suspected ACS improve outcomes with an acceptable rate of adverse events?

Summary of Current Evidence

There is high-quality evidence demonstrating benefit of aspirin administration (162.5mg) in improving mortality among patients with an acute MI.^{5,6,7,8,9,10,11} This reduction in long-term mortality is greatest when the aspirin is administered early.^12,13

Current Prehospital Treatment Recommendation

Level A Recommendations

We recommend the administration of aspirin to adults with chest pain due to suspected ACS. In making this recommendation, we place a higher value on the benefits of aspirin (decreased mortality and decreased complications of MI), which outweigh the risks of adverse effects (gastrointestinal bleeding). Aspirin is contraindicated in the setting of known aspirin allergy.

Level B Recommendations

None given.

Level C Recommendations

None given.

No Recommendation

N/A

Clinical Question

Does the administration of nitroglycerin in the prehospital setting to patients with suspected ACS improve outcomes when compared to not using nitrates?

Summary of Current Evidence

There have been no trials to specifically evaluate the usefulness of nitrates in the field or in the emergency department (ED) among patients with chest pain of suspected ACS.⁵ A reduction in infarct size (using creatinine kinase as a surrogate measure) was noted in those treated within three hours of symptoms in three studies of intensive care unit patients.^14,15,16 There have been two trials showing that combined treatment with nitroglycerin and fibrinolytics may have a detrimental effect on reperfusion.^17,18 There is currently not enough evidence to suggest clinical benefit or harm of nitroglycerin use in the prehospital setting.

Current Prehospital Treatment Recommendation

Level A Recommendations

None given.

Level B Recommendations

None given.

Level C Recommendations

If nitroglycerin is used, then the following contraindications should be part of the protocol (expert consensus):

• Contraindications with hypotension, defined as a systolic blood pressure less than 90mmHg, by expert consensus.
• Contraindications with suspected right side/inferior infarct.
• Contraindication with the recent use of phosphodiesterase-5 inhibitors for erectile dysfunction or pulmonary hypertension.

No Recommendation

Although it is reasonable to consider the early administration of nitroglycerin in selected patients without contraindications, insufficient evidence exists to support or refute the routine administration of nitroglycerin in the ED or prehospital setting in patients with suspected ACS.⁵

Clinical Question

Does the administration of opiates to patients with suspected ACS improve outcomes when compared to not using opiates?

Summary of Current Evidence

Clear benefit to opiate administration is unclear. There is a single study that suggested mortality and rates of infarction are more prevalent in patients who receive morphine with Non STEMI.^5,19 No studies have been done with fentanyl among patients with chest pain of suspected cardiac etiology.

Current Prehospital Treatment Recommendation

Level A Recommendations

None given.

Level B Recommendations

None given.

Level C Recommendations

If opiates are used, they should be administered intravenously and titrated to pain relief (consensus). Contraindications with hypotension, defined as a systolic blood pressure less than 90mmHg.

No Recommendation

Although it is reasonable to consider the early administration of opiates in selected patients without contraindications, insufficient evidence exists to support or refute its routine administration in the ED or prehospital setting in patients with chest pain of suspected ACS. There is only one poor quality study that demonstrated harm.

Clinical Question

Does the prehospital use of a 12-lead ECG increase the diagnostic sensitivity and specificity of STEMI among patients with chest pain of suspected ACS when compared to not using a prehospital 12-lead ECG?⁵

Summary of Current Evidence

Several studies have demonstrated that prehospital 12-lead ECGs can improve the recognition of STEMI with reasonable sensitivity and specificity.^{20,21,22,23,24,25,26} Repeat prehospital or ED 12-lead ECGs may be helpful.^21,27 The timely notification of the STEMI center is helpful in reducing door-to-intervention times.²⁸ The research on computer-interpreted electrocardiography has been mixed but seems to be generally accurate and had a greater influence on non-expert performance.^5,29 There has been limited research in the effectiveness of transmission of the 12-lead ECG.³⁰

Current Prehospital Treatment Recommendation

Level A Recommendations

In patients with suspected ACS, a 12-lead ECG should be acquired and interpreted by prehospital or emergency providers as soon as possible after first patient contact. The interpretation should be used in conjunction with the clinical signs and presentation for diagnosis and triage, including destination decisions.

Level B Recommendations

Repeated prehospital 12-lead ECGs may improve diagnostic accuracy of STEMI. Transmitted 12-lead ECGs may be useful in decreasing door-to-intervention times. The timely notification of the STEMI-receiving center is helpful in decreasing door-to-intervention times. Prehospital activation of the catheterization lab may also help to decrease door-to-intervention times. Computer interpretation of 12-lead ECGs may help to increase the specificity of the diagnosis, especially with less experienced paramedics.

Level C Recommendations

None given.

No Recommendation

N/A

Clinical Question

Does the regionalization of STEMI care lead to decreased door-to-intervention times and improved patient outcomes in prehospital patients with STEMI when compared to a non-regionalized program?

Current Prehospital Treatment Recommendation

Level A Recommendations

There is a large body of evidence suggesting that primary PCI is superior to thrombolytics. There is also evidence suggesting benefit of STEMI regionalization programs in decreasing door-to-intervention times. We recommend EMS systems employ a regionalization program for STEMI patients that provide direct transport to PCI capable centers. In cases where timely transport to a PCI center is not possible (>90min), transport to a facility that can provide thrombolytic therapy is reasonable.

Level B Recommendations

None given.

Level C Recommendations

None given.

No Recommendation

N/A

Summary of Current Evidence

It has been shown in multiple studies that primary PCI is the ideal method of reperfusion in patients presenting with STEMI.³¹ Timely PCI leads to decreased morbidity and mortality in this patient population.^32,33 Current AHA recommendations call for a first medical contact to intervention time of less than 90 minutes and additionally note that the EMS system can play a large role in decreasing not only D2B time, but “total ischemic time,” as well.^11,34,35 The AHA also recognizes that PCI is not always available and in these cases thrombolytics may be required.¹¹ Regionalization of STEMI care does lead to decreased door-to-intervention times.^36,37 The evidence for improvements in mortality and other clinical outcomes among STEMI patients are less well studied.

Rapid inter-facility transfers of patients with STEMI presenting to a non-PCI hospital can reduce time to treatment. STEMI systems should include an organized inter-facility transfer process that includes inter-hospital agreements and ambulance dispatch protocols designed to minimize transfer time.

Clinical Question

In patients with STEMI and a prolonged time to primary PCI, does the use of prehospital fibrinolytics improve outcomes?

Summary of Current Evidence

There is a significant body of high-quality evidence describing the benefit of fibrinolytic therapy given to patients with STEMI when it is anticipated that primary PCI cannot be performed within 120 minutes of first medical contact.^10,11,38,39 If prehospital fibrinolysis is chosen as the reperfusion strategy, there should be well-established protocols with a competency training program, performance improvement, and robust medical oversight. This is not currently in the scope of practice for paramedics in the state of California.

Current Prehospital Treatment Recommendation

Level A Recommendations

None given.

Level B Recommendations

None given.

Level C Recommendations

For those patients with a STEMI, onset of ischemic symptoms within the previous 12 hours and primary PCI cannot be accomplished within 120 minutes of first medical contact, prehospital fibrinolytics can be considered. There should be considerable oversight for any prehospital thrombolytic program. Because it is not in the current scope of practice for paramedics in California, this could only be done as a pilot study with approval from the EMS Authority.

No Recommendation

N/A

Clinical Question

Does the prehospital administration of a β-blocker to patients with an acute STEMI improve outcomes?

Summary of Current Evidence

Current recommendations by the AHA are that a β-blocker be administered in the first 24 hours after an acute MI.⁴⁰ There is evidence to show that early β-blocker administration may improve infarct size and left ventricular ejection fraction.⁴¹ There has been one study comparing prehospital metoprolol administration to patients with STEMI to those receiving metoprolol 12 to 24 hours later. The prehospital patients, in this study, showed smaller infarct sizes and improved ejection fractions.⁴²

Current Prehospital Treatment Recommendation

Level A Recommendations

None given.

Level B Recommendations

None given.

Level C Recommendations

None given.

No Recommendation

While the prehospital administration of β-blockers does seem to show promise, there are insufficient studies at this time to make a prehospital treatment recommendation regarding their use in the field.

The chest pain protocols reviewed varied greatly in content and structure between LEMSAs in California. These government agencies consist of either a county or region that develops a system of care that include first responders, ambulance transporters, and specialty receiving facilities. These systems reflect the needs and demographics of that county or region and operate under one set of medical control policies.

A similar variation among protocols was seen in a recent study on state wide EMS protocols.⁴³ The National Association of EMS Officials recently published model EMS guidelines that could be used to decrease this variability.⁴⁴

Many agencies use some sort of titration language for oxygen use but only four restricted use with normal saturations. The current evidence seems to point towards more restrictive language for our protocols. Aspirin use, while universal, varied considerably in dosing and many agencies did not have contraindications clearly noted in their protocols. Local training could address these issues, even if not explicitly stated in the protocols themselves. Recent studies have demonstrated low rates of prehospital aspirin administration despite being almost universal in our protocols.⁴⁵

Nitroglycerin is used by every agency with a wide variability noted in delivery route. Few agencies noted a contraindication with right-sided infarcts, with one agency not allowing nitrates in any patient with STEMI to avoid this potential contraindication. Most agencies did caution use with PDE5 Inhibitors. Holding nitroglycerin for hypotension was universal, but the systolic blood pressure cut-off varied. Our recommended cut-off is a systolic blood pressure of 90mmHg.

Opiates were also found to be used in all protocols with many agencies preferring fentanyl over morphine. It should be noted that studies with fentanyl for ischemic chest pain are not available to specifically recommend this agent for suspected ACS.

Twelve-lead ECGs were used in all but one agency. The technique used to interpret STEMI varied between agencies with some using computer interpretation, medic interpretation or both. Most agencies notified receiving centers of their potential STEMI and many have transmission capabilities.

Prehospital fibrinolytics, while not employed at any agency, may still have a place for some rural systems without timely access to regionalized STEMI centers. Currently, paramedics in California do not have this in their scope of practice. If such a system were to be put in place it would require a trial study and substantial medical oversight.

While many states have mandatory protocols in place for their providers, California has allowed the individual agencies to develop and implement their own protocols. While this has allowed for flexibility among regions with different populations and financial and geographic restrictions, it may also contribute to health outcome disparities among the agencies. A study by Kupas et al. coined the term “model” protocols, which were found to be present in 17 states.⁴³ In contrast with mandatory protocols, which require local agencies to adopt the state protocols, model protocols are in place as an option for local use, but not required. This respects the local agencies’ autonomy, but also provides a standard that can be adopted should a local agency need to create or change its protocols.