EMS is often criticized for not having the same evidence base as hospital-based medicine. Backboards, c-collars, and even ALS as a whole has been criticized as not efficacious. Here, we’ll debunk some recent EMS myths and examine the evidence (or lack thereof) behind them.
The myth: Prolonged CPR in out-of-hospital cardiac arrest does not lead to improved survival.
What the studies say: Several EMS systems have termination of resuscitation criteria (TOR) allowing EMS agencies to pronounce the patient dead in the field, avoiding transportation to the ED. Some studies, however, support prolonged ACLS efforts and always “loading and going.” Back in 2000, The National Association of EMS Physicians (NAEMSP) said 20 minutes of ACLS by EMS was an adequate effort for out-of-hospital cardiac arrest (OHCA) . The American Heart Association has no specific recommendations, and NAEMSP hasn’t continued to recommend termination of resuscitation since 2000. Some current studies emphasize criteria, whereas others still focus on time. A recent NEJM article claims 37 minutes for any patient is sufficient . After studying 9467 patients, it found 90% of patients with a good neurological outcome at discharge had return of spontaneous circulation (ROSC) within 20 minutes, and 99% had it within 37 minutes. Other studies go a step further and say TOR criteria work well for adults having OHCA from cardiac etiology, but they shouldn’t be used for children or non-cardiac etiologies (like presumed respiratory arrest preceding cardiac arrest in an asthmatic, for instance) . In contrast to the 37-minute rule, capturing 99% of patients with a good neurological outcome, a British Columbian study just published in Annals of Emergency Medicine found only a 2.1% false-positive rate after six minutes. While the statistics are not directly comparable, it certainly illustrates a large spectrum of time. The authors applied three TOR criteria to 6,994 patients: arrest not witnessed by EMS, no shocks delivered, and no prehospital ROSC. They found a 2.1% false-positive rate at six minutes resuscitation (The patient eventually had ROSC despite meeting all the criteria) . Most other studies incorporate those criteria, but also include bystander CPR and witnessed collapse.
Bottom line: Prolonged CPR is usually not helpful. Efforts are usually futile after 37 minutes (and maybe even after six). In certain cases and in areas where resources (like crew members, or ALS equipment) are scarce, it may make sense to transport and prolong efforts until more advanced and definitive care is available.
We do want to avoid futile resuscitations, perhaps especially those for whom a meaningful recovery is extremely unlikely. On the other hand, we should be aware the basis used by many practitioners is not scientific evidence but upon “gut” reactions and bad experiences from an older era of resuscitation when “everyone died.”
The myth: If the Cincinnati stroke scale is negative, there likely isn’t a stroke
What the studies say:
A 2015 study of 448 people found 93% sensitivity and 51% specificity of acute CVA using the Cincinnati stroke scale . The scale incorporates facial droop, pronator drift, and slurred speech. A 2011 AHA study said 1 of 3 of these findings mean there’s a 72% probability of stroke, and if all three are present, the probability is >85% .
Bottom line: The Cincinnati stroke scale is sensitive, but not sensitive enough to confidently rule out a stroke in the pre-hospital setting. As usual, these patients should be evaluated upon arrival with a full neuro exam to pick up on the subtler manifestations of stroke, so the decision to call “code stroke” can be made.
The myth: SL Nitro is a mainstay for chest pain, but inferior MIs should get fluid, not nitro.
What the studies say: Back in 1989 The American Journal of Cardiology said SL nitro can lead to >30mmHg drop in SBP in 60% of inferior MIs , but a 2016 Prehospital Emergency Care retrospective study of 1466 STEMIs (56% of which got SL nitro) says inferior infarcts aren’t at any higher risk for hypotension than any other infarct after getting SL nitro . The decision of whether or not to give nitro is further complicated by the fact that most BLS crews have SMOs that say to treat “chest pain” with aspirin and nitro, without a way of knowing what kind of MI they might be treating (RV or otherwise).
Bottom line: There is a paucity of data, but the latest study seems to say nitro is just as safe in inferior MIs as any other, and no nitro in inferior MIs may be a myth. Anecdotally, however, it seems that most cardiologists would not recommend giving it in inferior MIs, especially in pre-hospital settings where resources are limited compared to the ED.
The myth: D10 should be the gold standard for hypoglycemic adults
What the studies say: EPM wrote about this in 2015, arguing D10 is safer, more physiologic, less error prone, and equally effective as D50. A 2009 study claimed D10 had fewer adverse effects than D50 for adult hypoglycemia . D10 has less frequent rebound hyperglycemia compared to D50, and some studies argue we should “titrate to effect” with dextrose. A study on cats demonstrated hyperglycemic brain injury (neuronal necrosis) can happen in hypoxic, hypoglycemic brain injured subjects when their glucose is overcorrected . Needless to say, that study was not very meaningful, as it is 17 years old, had an n=21, and was on cats. A 2004 Journal of Trauma study on 516 brain injured patients found hyperglycemia (>200 mg/dL) to be linked to increased infection and mortality, with euglycemia having better survival and fewer infections . The same has been documented in patients after having a CVA ; however, both of these studies were in ICU patients and do not focus on patients with transient hyperglycemia in the emergency room specifically after getting D50 but rather long-term, stress-induced hyperglycemia.
A final argument for D10 is that it’s less viscous than D50 and therefore more compatible with smaller gauge IVs; hypokalemic patients can get more hypokalemic as hyperglycemia induces more insulin release.
Despite these arguments for D10, a 2016 review of 185 EMS agencies by Prehospital Emergency Care said 70% of the EMS agencies treating hypoglycemic patients use D50 only and 8% use D10 exclusively. So, should more EMS agencies be switching to D10 only?
While there may be rare, adverse effects in a certain demographics with D50, overall who cares if they have iatrogenic, transient hyperglycemia from D50? As long as we’re not talking about hypoxic, hypoglycemic, hypokalemic or brain injured patients with small IVs, the sugar should normalize with time and not cause any issues. In addition, there’s an extra safety zone if their blood sugar keeps dropping. If you only correct their blood sugar to 120, they have a much smaller distance to go before they’re at 39 and unconscious again. How many times have we seen a hypoglycemic patient get hypoglycemic again after D50 while we watch them in the ED? If they had gotten D10, they would have gotten hypoglycemic much sooner, and it may not have been detected in time with q1h accuchecks.
Bottom line: While there are a handful of studies voting for D10, a lot of the research hasn’t been done in the pre-hospital or ED population. The literature also hasn’t addressed the disadvantages of D10 compared to D50, like recurrent hypoglycemia which could lead to hypoglycemic brain injury. Most agencies are using D50, and until further research is done, that seems understandable.
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