Emergency Medical Services – November

Maybe. Given the history provided as well as the flushed face and facial swelling, the patient may have gone into cardiac arrest due to anaphylaxis from bee stings. There are 3 ways that anaphylaxis can lead to cardiac arrest:

1) Upper Airway Obstruction – swelling of the tongue and upper airways can cause complete airway obstruction leading to hypoxia and death. The treatment for this is epinephrine. Epinephrine produces vasoconstriction in the tissues, decreasing swelling. For anaphylaxis where upper airway obstruction is suspected, consider intubation early, before the obstruction becomes completely occluded. It will be dicult or impossible to intubate or ventilate if progressive swelling completely occludes the upper airway. Consider intubation with a smaller tube than you would normally use for the patient’s size (for example a 7.0 instead of a 7.5) and have multiple sizes prepared prior to your attempt. If the airway is fully occluded and ventilation is impossible (low EtCO2 and flat/absent capnography waveform), transport to the MAR with CPR and ACLS care in progress.

2) Bronchospasm – Severe bronchospasm can lead to hypoxia and death. The treatment for this is medication with beta agonism. Activating beta receptors in the lung can cause bronchodilation and combat bronchospasm. Albuterol is traditionally given for bronchospasm in a living patient. However, epinephrine, which is a more potent beta agonist, should be prioritized in anaphylaxis, with albuterol administered after. Epinephrine is more effective to treat bronchospasm and delivers the medications through the bloodstream to all areas of the body. With severe bronchospasm, albuterol may not eectively reach the lungs until epinephrine starts combating the bronchospasm.

3) Vasodilation – Inflammation from the allergic reaction can lead to profound vasodilation, often demonstrated by flushed red or swollen skin. As the patient’s blood vessels expand, it creates a larger vascular volume “tank” to fill with blood. When the vascular volume increases but there is no additional fluid to fill that tank, blood return to the heart decreases, leading to severe hypotension. Low blood pressure causes altered mental status due to insufficient blood flow to the brain and a PEA rhythm, because the heart continues beating (for a while) but is pumping too little blood in each beat to create a palpable pulse. There may even be insufficient blood to perfuse the heart itself, leading to asystole. Treatment for vasodilation includes epinephrine and IV fluids. Epinephrine constricts the blood vessels to raise the blood pressure and decrease the vascular volume “tank”. IV fluids help fill up the expanded “tank”, increasing preload to the heart.

Visual inspection of the patient’s oral airway may reveal significant swelling if upper airway obstruction caused cardiac arrest. Ventilating the patient will also help clue you in. Stridor or inability to bag would be suggestive of upper airway swelling causing cardiac arrest. Wheezing or diculty bagging would be indicative of bronchospasm from anaphylaxis. Flushed skin may predict severe hypotension. Altered mental status can be found in all of the above. And a combination of two or more of the above situations can happen simultaneously.

The patient’s response to BMV and his EtCO2 waveform will both be important to determining the cause of the arrest and the appropriate treatment(s).

Question: Which of the following signs or symptoms is an indicator that vasodilation may have been the cause of a patient’s cardiac arrest?

1. Constricted pupils
2. Flushed skin
3. Stridor
4. Wheezing

Answer: 2. Dilated blood vessels cause increased blood flow to superficial tissues, leading to warm, flushed skin. Stridor implies upper airway obstruction while wheezing implies bronchospasm. Constricted pupils are non-specific but may imply opioid overdose rather than anaphylaxis.

Question: What does a “sharkfin” appearance of a capnography waveform indicate?

1. Bronchospasm or partial airway obstruction
2. Inadequate chest compressions
3. Severe sepsis with septic shock
4. Upper airway complete obstruction

Answer: 1. Bronchospasm or partial airway obstruction prolongs the exhalation phase, decreasing the slope of the upswing on the waveform and causing a “sharkfin” appearance.

As the paramedic, you are unlikely to be performing BMV yourself. It is very important for paramedics to ask the person who is ventilating how easy or hard it is for them to ventilate the patient, and for the paramedic to evaluate the capnography waveform.

• A patient with poor BVM compliance (“difficult to bag”) and a “squiggly line” or “flat” EtCO₂ waveform likely has a severe upper airway obstruction (as you would see in choking or “throat closing” in anaphylaxis). CO₂ is unable to return to the detector and implies minimal to no ventilation.
• A patient with poor BVM compliance and a  “sharkfin” EtCO₂ waveform is likely to have severe bronchospasm. The tightening of the lower airway means the exhalation is prolonged and slowly decreases causing the “sharkfin” appearance.
• A patient with good BVM compliance and a square-shaped “normal” waveform with low EtCO₂ is likely to have arrested from vasodilation-induced hypotension.
• If BVM compliance worsens after initiating ventilation, consider progressive gastric distension (from hyperventilation), accumulation of fluid in the lungs, or development of a tension pneumothorax. The capnograph waveform is typically normal in these cases but may vary.

Anaphylaxis compromises a spectrum of signs and symptoms. Remember that patients may have a mix of these symptoms at differing levels of severity.

Your EMT reports good compliance with BMV.  EtCO₂ is 9 with a flat-topped, square-shaped waveform. This patient is not difficult to ventilate and his waveform is normal, so it is unlikely that his airway is obstructed by angioedema or that he has severe bronchospasm. Thus he most likely arrested secondary to profound vasodilation from anaphylaxis. You administer epinephrine (0.1mg/mL) 1 mg IO every 5 minutes for two doses. Between doses, you attempt an IV but are unable to establish an IV due to swelling of his arms. You pressure-bag administer IV fluids through the IO.

After two doses of epinephrine and normal saline 500mL IO, the patient obtains ROSC.

Post-ROSC vital signs show sinus tachycardia with a rate of 140. BP is 80/40, SpO2 is 95% and EtCO₂ is 28 with a normal, square waveform.

You administer an additional 1L normal saline through the IO as well as push dose epinephrine with a goal of SBP > 90. It is important to administer fluids in patients with anaphylaxis and hypotension to help overcome the vasodilation. If administering IVF through the IO, you can use a large syringe to “push-pull” fluids from the normal saline bag, overcoming the resistance of the bone marrow.  Alternatively, you can use a a pressure bag to speed infusion. Be aware that there is no consensus as to flow rates whether allowing flow to gravity, using push-pull, or using pressure bags to IV or IO lines. This is especially true for IO lines, where the measured flow rates vary widely in different studies. But based on existing research, the following table shows estimated infusion rates through different methods (note: possible range is listed for IO lines with and without pressure bag).

*Assumes presence of saline “lock” on all IV/IO catheters.

Flow rates adapted from: Reddick, 2011 (IV), Gillis, 2018 (push-pull), Hammer, 2015 and Ngo, 2009 (IO).  See References, below, for full citations.

After administering two doses of push dose epinephrine, the patient’s BP improves to 94/60. A 12-lead

ECG demonstrates diffuse ST depressions. With the patient stabilized post-ROSC, you begin transport to the nearest SRC and contact the base to request a second liter of fluid and to alert them of the incoming patient. You are likely to need more fluids than written in protocol for this patient in anaphylaxis. Communicate why you want more fluids to the base hospital.

The treatment for anaphylaxis is epinephrine, either IM or IV. Reserve IV epinephrine for cardiac arrest or severe hypotension despite IM epinephrine. This patient has received IV epinephrine and may require more epinephrine if they become hypotensive again.

Epinephrine starts to improve symptoms very quickly after administration, often within seconds to minutes. Peak effect of epinephrine is 5-10 minutes after IM administration and will begin to wear off after approximately 20-30 minutes. IV epinephrine starts to produce effect in seconds, with peak effect in as little as one minute, and a half-life of less than 5 minutes.

Other field treatments for allergic reaction include diphenhydramine and albuterol. Per TP 1219, Allergy, diphenhydramine can be administered for itching and hives; its indication is for comfort and it does not confer any mortality benefit–it is not a “life-saving” medication. Albuterol may be administered for wheezing. In the setting of anaphylaxis, both treatments should only be given after epinephrine has been administered. Albuterol may be given inline through an ETT, CPAP, or BVM.  Here is a link to a picture that shows how it may be attached:

Airway: BVM with In-Line Nebulizer (click here)

Question: If this patient had significant stridor and difficulty with BVM ventilations with jaw thrust, what would be the best way to secure the airway?

1. BVM with oropharyngeal airway (OPA)
2. BVM with nasopharyngeal airway (NPA)
3. Endotracheal tube
4. Supraglottic airway device (e.g. iGel)

Answer: 3. An endotracheal tube is the definitive airway management to use in the case of upper airway compromise. It passes the swollen tissues to secure the airway. Oropharyngeal and nasopharyngeal airways are unable to overcome the swelling which is present in the upper airway. An SGA is not appropriate in cases of suspected or impending upper airway obstruction.

In addition to epinephrine (which in severe cases is given as an infusion), Emergency Department treatments for allergic reactions include steroids, diphenhydramine or other antihistamines, famotidine, and albuterol. None of these additional treatments will reverse anaphylaxis.

You continue to administer push-dose epinephrine intermittently throughout your transport due to low blood pressure. The patient is intubated by the emergency department team without difficulty. He is started on an epinephrine drip due to continued hypotension, and also receives steroids and additional IV fluids. He stabilizes on the epinephrine drip and is transferred to the ICU. He eventually stabilizes, is extubated, and has functional recovery.

• It is important for you to evaluate both BVM compliance and the capnography waveform in cardiac arrest as this information can help determine the cause of arrest and affect your intra-arrest and post-ROSC care.
• Anaphylaxis is a life-threatening condition that can be very rapid in onset, within a minute of allergen exposure, and should be managed aggressively.
• Epinephrine is the ONLY effective treatment for anaphylaxis, it should be your top priority for the anaphylactic patient.
• Scene safety considerations may prevent the rapid access and treatment of patients. Despite our desire to care for critical patients, the threat of a bee swarm must be mitigated prior to patient contact to decrease risk to providers.