International Prehospital Medicine Institute Literature Review, February 2025

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1. Naloxone and Patient Outcomes in Out-of-Hospital Cardiac Arrests in California. Dillon DG, PhD; Montoy JCC, Nishijima DK, et al. JAMANetworkOpen.2024;7(8):e2429154; published on-line, full text available at: https:// doi:10.1001/jamanetworkopen.2024.29154

2. The impact of using time critical intervention-based dispatch thresholds on lowering lights and siren use to EMS 911 incidents. Jarvis JL, Johns D, Jarvis SE, Knipstein M, Ratcliff T. JACEP Open 2024;5:e13232. published on-line, full text available at: https://doi.org/10.1002/emp2.13232.

3. Prehospital Treatment of Atrial Fibrillation: Infusion Pump for Bolus and Infusion? Berkenbush M, Sherman N, Jain N, Cosmi P. Prehospital Emergency Care, 2025;29:85-88.

4. Prehospital Partial Resuscitative Endovascular Balloon Occlusion of the Aorta for Exsanguinating Subdiaphragmatic Hemorrhage. Lendrum RA, Perkins Z, Marsden M, et al. JAMA Surg. 2024;159(9):998-1007


International Prehospital Medicine Institute Literature Review, January 2025


1. Naloxone and Patient Outcomes in Out-of-Hospital Cardiac Arrests in California. Dillon DG, PhD; Montoy JCC, Nishijima DK, et al. JAMANetworkOpen.2024;7(8):e2429154; published on-line, full text available at: https:// doi:10.1001/jamanetworkopen.2024.29154

The opioid epidemic has dramatically increased out-of-hospital cardiac arrest (OHCA) associated with opioid overdose. In the last 10 years, the increase is estimated to involve approximately 10 percent of all OHCAs. Naloxone administration has been demonstrated to reverse the effects of opioids in pre-arrest scenarios. However, there is little evidence demonstrating the efficacy of OHCA although the American Heart Association recommends considering naloxone for opioid-associated OHCA. The authors of this retrospective cohort study evaluate if the use of naloxone in the presence of OHCA affects patient outcomes.

The data was gathered from a retrospective review of the cardiac arrest registry from 2015-2023 from three large northern California counties. Those eligible for enrollment into the study included patients over the age of 18 years of age with non-traumatic cardiac arrest. The primary study outcome was discharge from the hospital, with a secondary outcome of return of spontaneous circulation (ROSC). During the study period, 8339 individuals were treated for non-traumatic cardiac arrest. One hundred twenty-two (122) patients were excluded due to age, and twenty-two (22) were excluded for incomplete data. In all, 8195 patients were enrolled and evaluated by the authors.

EMS providers administered naloxone to 1165 patients (14.2%). The patients who received naloxone were more likely to be younger, male, and presumed to have a drug-related cardiac arrest. The naloxone group was more likely to have ROSC (34%) compared to the non-naloxone group (22%). Survival to hospital discharge in the naloxone group was 15.9% compared to 9.7% in the non-naloxone group.

The authors note limitations to the study, including the observational nature of the study and biases in the data. Although adjustments were made, the authors say full adjustments and comparisons were not possible. In addition, they did not have information on route of administration (IV, IO, or nasal) as well as the timing of administration.

The authors concluded that in patients with OHCA, EMS administration of naloxone was clinically significant for both ROSC and hospital discharge. Opiate-related issues are encountered on a daily basis by EMS providers and sometimes, these encounters involve cardiac arrest. While this study has limitations, currently, no prospective studies have been conducted evaluating naloxone administration in cardiac arrest. Since naloxone administration has no demonstrated downsides, consideration for its use should be evaluated in cardiac arrest patients. Further studies, including prospective randomized studies, should be conducted and evaluated.

2. The impact of using time critical intervention-based dispatch thresholds on lowering lights and siren use to EMS 911 incidents. Jarvis JL, Johns D, Jarvis SE, Knipstein M, Ratcliff T. JACEP Open 2024;5:e13232. published on-line, full text available at: https://doi.org/10.1002/emp2.13232.

Lights and Sirens (L&S) are used by ambulances in between 86% and 97% of 911 responses. With the use of lights and sirens being associated with a 50% increase in ambulance crashes, and the majority of fatal ambulance crashes involving ambulances using lights and sirens, the authors suggest limiting the use of lights and sirens to the 7% of 911 responses known to require Time Critical Interventions (TCI).

The authors sought to develop a TCI threshold-based dispatch model using historical data from their EMS system to establish whether Lights and Sirens should be used on each 911 response and to determine the effect Lights and Sirens or no Lights and Sirens had on dispatch accuracy and response times. A TCI was defined as an intervention “reasonably expected to reverse a critical condition or rapidly improve hemodynamic stability.” The authors created a list of potential TCI’s and then assembled a panel made up of EMS clinicians including field clinicians, senior medical officers, field training officers, field commanders, office based clinical practices staff (paramedics promoted to administrative roles), the system medical director and EMS director. They also invited each of the first responder agencies involved to send a representative for this review. The panel met virtually and communicated via e-mail.

A separate consensus panel was then assembled to determine a TCI threshold “above which call natures should be assigned an L&S response.” The EMS Director and Medical Director, each Fire Chief, County Commissioners and EMS field commanders were invited to participate.

All EMS interventions were categorized as to whether it was a TCI or non-TCI event and determined a TCI threshold above which lights and sirens would be used. The list of time critical interventions was as follows:

AED defibrillation

Amiodarone      

Amiodarone infusion

BiPAP/VPAP

Cardioversion

CPAP

CPR

Dual Sequence Defibrillation

Epi 1:100,000

Epi 1:1,000

Epi 1:10,000

Epi infusion

iGel

Magill Forceps

Manual defibrillation

Mechanical CPR

Narcan

NPA

OPA

Pacing

Pericardiocentesis

Pleural decompression

Rocuronium      

Simple thoracostomy

STEMI alert

Stroke alert

Suction

Surgical cricothyroidotomy

Tourniquet

Trauma Alert

Video laryngoscopy

They then compared the EMS agencies response data before and after implementation of their TCI-based dispatch thresholds. There were 13,879 total responses in the before group and 14,117 in the after group. The rate of L&S use was reduced from 56.2% to 27.6% in the after group. TCI’s were performed in 6.9% of the before group and 7.6% of the after group and accuracy increased from 48.8% to 75.1%. The median response time increased from 8.3 to 8.4 min.

Limitations of this study include the fact that their determination of TCI’s and TCI thresholds was subjective. Other panels of experts might come up with different TCI’s and thresholds. Since this was a retrospective study, it was dependent on the clinical documentation and therefore is subject to errors.

The authors believe these results support the use of their methodology to determine EMS Response modes. They concluded that “L&S use can be objectively assigned to those calls in which time critical interventions are most likely to occur. Doing so can reduce L&S use and increase dispatch accuracy with small marginal increases in response times.”

3. Prehospital Treatment of Atrial Fibrillation: Infusion Pump for Bolus and Infusion? Berkenbush M, Sherman N, Jain N, Cosmi P. Prehospital Emergency Care, 2025;29:85-88.

Diltiazem, a slow channel calcium blocker, is often used by both hospital and prehospital providers to decrease heart rates due to atrial fibrillation with rapid ventricular response. Diltiazem is typically given via slow IV bolus over two to four minutes. Reoccurrence of a rapid heart rate or hypotension due to a too rapid IV bolus are side effects of diltiazem administration. An alternate method of diltiazem administration is via an IV pump- controlled bolus over two to four minutes immediately followed by a continued IV infusion. The authors of this article attempted to compare the incidences of hypotension, post diltiazem administration, in a single EMS agency that encourages the use of IV pumps to bolus and infuse diltiazem for atrial fibrillation with rapid ventricular response.

This is an institutional review board approved retrospective review study with waiver of consent. By protocol, paramedic providers in this two-tiered system (BLS transport / ALS non-transport) are allowed to administer diltiazem 0.25 mg/kg IV bolus followed by an infusion of 10 mg/hr. The intent of this study was to compare the dosage, time of administration, rate control and the presence of prehospital hypotension between patient groups that received diltiazem via bolus and IV pump. The authors reviewed data from EMS patients that received diltiazem in the field between 1/01/2018 and 12/31/21. Four hundred eighty-five patients were initially identified. After propensity-matching this group was culled down to 314 patients with an additional 23 patients excluded due to non-accessibility of their hospital charts. There were 145 patients in the bolus only group (BO) in which the medication is administered manually and 146 in the bolus and infusion group (BI) which had both the bolus and the infusion given via pump.

There was no significant difference in mean heart rate change between the two groups (BO 38 vs. BI 34), nor was there a significant need for an additional bolus of diltiazem within the first hour after arrival at the hospital (BO 9.7% vs. BI 11.6%). Despite receiving lower initial boluses (BO 14.2 mg vs. BI 17.4 mg), patients in the bolus only group experienced hypotension (systolic blood pressure less than 90 mm Hg) more frequently than those in the bolus infusion group (BO 17.2% vs BI 8.2%). Patient demographics were closely matched between the two groups.

There are multiple self-identified limitations of this study. This is a one agency, one data set study. The authors also opined that the EMS system design may have limited the study. Paramedics in a one-tiered system may have a greater number of acutely ill patient contacts resulting in greater familiarity with IV infusion pumps. Weight based dosing calculations may have contributed to the variance in rate control between the two groups. Generalizing this study to other EMS systems may be difficult as many EMS agencies do not use infusion pumps. Lastly, it was difficult to determine the exact length of time for manual administration of diltiazem in the bolus only group (less than or greater than the protocol specific 2-4 minutes).

The authors concluded that patients that received diltiazem via manually administered bolus were more likely to experience post bolus hypotension. They also noted no difference in rate control or need for subsequent hospital doses of diltiazem between the two groups, BO and BI. It makes sense for prehospital providers to use all available resources to prevent future harm or the potential for future harm while treating patients. The use of IV infusion pumps to accurately control medications that directly alter a patient’s blood pressure is a reliable way to reduce harm and medication calculation errors.

4. Prehospital Partial Resuscitative Endovascular Balloon Occlusion of the Aorta for Exsanguinating Subdiaphragmatic Hemorrhage. Lendrum RA, Perkins Z, Marsden M, et al. JAMA Surg. 2024;159(9):998-1007

Uncontrolled hemorrhage is the most common cause of preventable death following injury, typically occurring within 30 minutes of injury and before the patient reaches the hospital. Any adjunct which can decrease preventable prehospital death from hemorrhage should be studied for potential effectiveness.

In many hospitals, the Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) is a procedure used to occlude the thoracic aorta to prevent exsanguinating hemorrhage in the abdomen or lower extremities. The technique involves percutaneous access of the femoral artery at the groin and placement of a sheath, through which a catheter is inserted and fed through the aorta to above the diaphragm in the chest. At this point the balloon on the catheter is inflated and distal blood flow stops.

This then allows time for definitive hemorrhage control in the operating room or interventional radiology suite. There are three zones of deployment of the REBOA. Zone 1 (Z1) is in the chest in the thoracic aorta and is analogous to aortic cross-clamping during resuscitative thoracotomy. Zone 2 is the anatomic area between the celiac artery and inferior mesenteric artery and is never utilized. Zone 3 (Z3) is the infrarenal aorta and occludes flow to the pelvis and lower extremities but maintains flow to the abdominal organs. Zone 3 deployment is done when the injury is known to be only in the pelvis or lower extremities.

Zone 1 deployment, while the most definitive position for hemorrhage control, also stops blood flow to the intestines and is typically only done for up to 30 minutes. Zone 3 deployment has been studied in the prehospital setting, but Zone 1 deployment has not. Additionally, partial REBOA (pREBOA) deployment is a newer technique allowing partial balloon inflation and allowing some distal blood flow to the intestines.

This study had three aims. The first objective was to determine the feasibility of prehospital Z1 REBOA use in critically bleeding trauma patients. The second objective was to determine the feasibility of using pREBOA in the prehospital setting. The third objective was to study the potential impact of Z1 pREBOA on prehospital and in-hospital outcomes and safety. This was a prospective observational study of Z1 pREBOA in a physician-led advanced urban prehospital system (London Air Ambulance and the London Ambulance Service). Patients were followed until discharge, death, or for 90 days from the date of their admission to the hospital. Eligible patients were any trauma patient above the age of 16 attended by London’s Air Ambulance with a clinical diagnosis of exsanguinating subdiaphragmatic hemorrhage or with recent or imminent risk of hypovolemic cardiac arrest.

During the 21-month study period, prehospital femoral artery access for REBOA was attempted in 16 patients. The majority of patients suffered from blunt injuries (81%). The median time from injury to arrival of London’s Air Ambulance on scene was 21 minutes (16-28 min). The cohort of patients was severely injured, with a median Injury Severity Score (ISS) of 50 (39-57) and were profoundly hypotensive with a median initial systolic blood pressure (SBP) of 58 mm Hg (47-82). Three patients were in traumatic cardiac arrest (TCA). Of the 16 patients, 2 had improvement in their clinical condition and REBOA was not attempted, so 14 patients had Z1 REBOA attempted.

Of those 14 patients, 8 were in TCA at the time of attempted REBOA. Three patients (all in TCA) had a failed attempt at prehospital femoral artery access and underwent immediate resuscitative thoracotomy. The remaining 11 patients had REBOA catheters inserted (including 5 in TCA). The median time from injury to balloon inflation in Z1 was 57 minutes (54-67 min). All procedures were performed on-scene except one, which was done during ambulance transport to the hospital. The median SBP improvement was 40 mm Hg. pREBOA was utilized in 8 of the 11 patients who underwent Z1 placement. Proximal hemodynamic stability was maintained in 7 of the 8 patients. In all patients, the median time from injury to arrival at the emergency department was 89 minutes (82-108 min).

Once at the hospital, immediate definitive hemorrhage control either in the operating room or interventional radiology suite was completed in 9 of 11 patients. Ten of the 11 patients undergoing Z1 REBOA placement survived for more than 3 hours. Eight patients survived for 24 hours and 2 patients survived for 30 days and to discharge. Multiple organ dysfunction syndrome occurred in 10 patients. Acute kidney injury was noted in 7 patients and acute intestinal ischemia requiring bowel resection was reported in 2 patients. Two patients had distal arterial thrombus formation requiring thrombectomy and 2 additional patients required bilateral above-knee amputation but had severe extremity injuries which was the ultimate indication for the amputations.

This study demonstrates that prehospital Z1 REBOA and pREBOA is feasible for severely injured trauma patients, with several very important caveats. All patients demonstrated a positive hemodynamic response to Z1 REBOA but the overall survival rate was still very low. The procedure of placing the REBOA added an average of 20 minutes to scene time and had an increased 90-day mortality. This finding is important. The increased scene time to perform REBOA increased the time to definitive hemorrhage control and potentially increased the death rate. Conversely, one could argue that many of those patients would have died anyway without the attempt at REBOA.

There are several limitations to this study. The study population is small, with only 14 patients ultimately being studied. The London EMS system is highly advanced and physician led. Their system is not applicable to the U.S. EMS system, or to many other EMS systems around the world. Prehospital trauma care in the U.S. emphasizes short scene times and rapid transport to a trauma center. The scene times in this study were quite long by U.S. standards. Arterial access and subsequent placement of the catheter is challenging for physicians in a controlled setting and is not done routinely by paramedics at this time.

This reviewer finds the study to be interesting but not terribly applicable to most EMS systems. The long scene times are concerning, which indicates a delay to definitive hemorrhage control. This would not be considered in the U.S. Additionally, the mortality rate in these patients was quite high and also shows the downstream affect of the prolonged scene time. This study could lead the way to additional studies on prehospital REBOA use, which could be a possibility in the distant future.

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