UMEM Educational Pearls - EMS

The typical bag valve mask ventilator (BVM) for adults has a reservoir volume between 1500-2000 mL depending on the manufacturer while the volume is between 500-1000 mL for a pediatric BVM.  When trying to obtain the recommended tidal volume of 6-8 mL/kg (500-600 mL for the typical adult), one thought was that a pediatric BVM could be used with adult patients so as to avoid iatrogenic barotrauma.  This has been studied on manakins using an oral pharyngeal airway, supraglottic airway and endotracheal tubes (ETT) and has been successful.  This study attempted to obtain the same results in the back of a moving ambulance.  Paramedics and EMTs, squeezing pediatric and adult BVMs with one hand, bagged adult manakins in the back of a moving ambulance (without lights and sirens).  The average tidal volume was recorded using various types of airways (i-gel, King airway and ETT).

Volumes delivered with the pediatric BVM were significantly lower than the tidal volumes with adult BVMs across all airway types suggesting that in the moving ambulance, using pediatric BVMs on an adult patient would not be appropriate.

The I-Gel and King airway provided similar tidal volumes which were not statistically different than volume delivered through the ETT.

EMTs consistently delivered 50% less tidal volumes compared to paramedics. The authors suggested that perhaps the additional training and pathophysiology knowledge that paramedics have could also be important with a skill that is considered basic. 

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BACKGROUND:
Emergency Medical Services (EMS) systems, especially those within urban jurisdictions, struggle to effectively meet the needs of patients experiencing complications of substance use. The exceedingly high burden of disease, coupled with potentially life-threatening sequelae of substance use stresses EMS systems beyond capacity. The current paradigm of naloxone administration and subsequent refusal of care places patients at an increased risk of death and other complications such as aspiration. EMS agencies, in collaboration with area hospitals, public health experts, and addiction medicine specialists are devising novel mitigation strategies to reduce morbidity and mortality. “Leave behind” naloxone, peer outreach, and 911 diversion programs are part of a more over-arching strategy that links patients to longer term, definitive health care resources within the community. EMS-administered buprenorphine has emerged as a novel treatment modality for prehospital patients. This study examined outcomes of patients who were a) experiencing symptoms of opiate withdrawal and b) given buprenorphine by a credentialed EMS paramedic. Patients included in the buprenorphine cohort scored >5 on the clinical opiate withdrawal scale (COWS), regained “full decisional capacity” after being resuscitated from an overdose, and were > 18 years of age. The study excluded pregnant patients and those who took methadone within 48 hours prior to an EMS encounter. After consultation with an EMS physician, patients received 16 mg of sublingual buprenorphine. Paramedics could administer ondansetron and an additional 8 mg of buprenorphine for continued symptoms. Finally, the study cohort was matched to a similar group of patients who were treated by “non buprenorphine equipped” ambulance. Outcomes of interest included: rates of repeat overdose, likelihood of transport, and follow up with addiction medicine/substance use resources. The study was conducted in an urban EMS system with robust EMS physician oversight and advanced life support transport units.

RESULTS:
Patients receiving buprenorphine did not experience a reduction in repeat overdose. However, they were less likely to be transported. The buprenorphine cohort, predictably, was much more likely to be enrolled in a substance use treatment program within 30 days of the initial encounter. Paramedics spent more time on scene with the buprenorphine cohort.  Though far from a conclusive study, the manuscript adds to a growing body of literature that attests to the feasibility of paramedic administered buprenorphine.

BOTTOM LINE:
Though far from a conclusive study, buprenorphine administration by EMS paramedics is feasible. The increased linkage to care and decreased rates of transport will hopefully motivate EMS systems to consider novel strategies for harm reduction. The study authors opine that buprenorphine may “be a promising…link to long term recovery.”

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Patient restraint is a high risk, high liability encounter for all levels of emergency medical practitioners. Often, acutely agitated patients benefit from de-escalation. This can be difficult to achieve in a resource limited setting. McDowell et al (2023) performed a comprehensive review of patient restraint encounters. Their work describes risk factors linked to adverse outcomes. Specifically, highly agitated patients who are physically and chemically restrained can experience clinical deterioration. The review also highlighted risks to EMS clinicians as well such as: needle stick, physical inury, and downstream litigation. 

Bottom line: 

Patient restraint represents a high risk encounter. 

• De-escalation is preferred vs. physical restraint 
• Chemical restraint likely preferred vs. physicial restraint 
• Restraint can worsen agitation and contribute to acidosis, positional asphyxia, cardiac arrest, and other untoward outcomes
• DO NOT place restrained patients in the prone position 
• Policies for restraint should be vetted, socialized, and regularly reviewed with all stakeholders 

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Bystander CPR increases out-of-hospital CPR survival and direction by 911 telecommunicators increases the frequency of bystander CPR.  The majority of 911 centers use Medical Priority Dispatch System which walks 911 telecommunicators through a series of questions that give different instructions based on the caller's answers.  Studies have shown out-of-hospital cardiac arrests are only recognized between 79-92% of the time and telecommunicator instructions for CPR can take between 176-285 seconds.

This study reviewed recorded 911 calls of patients who were found to be in cardiac arrest. Calls where the caller was not with the patient and confirmed overdoses were some of the call types that were excluded.

Out of 65 reviewed calls, 28% were not recognized during the actual call.  When they were reviewed, 8/18 of the calls were deemed to be recognizable.  Themes that were noted were: incomplete or delayed recognition assessment (ie uncertainty in breathing), communication gaps (callers were confused with instructions or questions), caller emotional distress, delayed repositioning for chest compressions, non essential questions and assessments, and caller refusal/hesitation or inability to act.

Bottom line: In addition to bystander CPR training, education on the process and questions involved in calling 911 could be helpful in an emergency.  

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There is room for improvement with respect to rates of meaningful neurological survival in patients experiencing out of hospital cardiac arrest. Post resuscitation blood pressure goals remain a matter of debate. Though a MAP of >65 mm Hg is often cited as "desirable" in the post cardiac arrest setting, some experts have advocated for a higher MAP goal to increase cerebral perfusion pressure and improve outcomes. 

This study was a retrospective review and meta-analysis that examined post cardiac arrest patients with MAP goals < 70 mm Hg and > 70 mm Hg. Over 1000 patients were included in the final meta-analysis. The primary outcome was pooled mortality. Secondary outcomes included neurologically meaningful survival, dysrhythmia, and acute kidney injury. The study detected no statistically significant difference in survival. Neurological outcomes were also similar between the two groups of resuscitated patients with out of hospital cardiac arrest. However, the study revealed statistically significant decreases in ICU length of stay and mechanical ventilation time. 

As with any retrospective review, there are important limitations to consider. Among them: Few RCTs were included and all of them were conducted in European countries. Generalizability may be limited given the differences in emergency medical services systems and resuscitation protocols. 

Study authors recommend tailoring resuscitation goals to the individual patient since arrest physiology, comorbidities, and other factors influence a patient's post cardiac arrest course. 

Bottom line: 
There is insufficient evidence to recommend arbitrary MAP goals in patients resuscitated from out of hospital cardiac arrest. 

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