The ECC guidelines for bradycardia show that both IV adrenergics with beta accelerating effects and TCP have equal levels of recommendation and thus, based on that, one probably isn't better than the other. Based on my limited experience with pacing, I have noted a high degree of failed or false capture (which would be very easy to miss). In those cases, dopamine was rapidly effective. I have spoken to others who have had similar experiences anecdotally.
Do the medical directives for bradycardia require always trying TCP first before proceeding to dopamine, or is trying dopamine first reasonable?
Thank you for your question.
When we are presented with the symptomatic bradycardic patient, we can go down multiple treatment modalities – electrical or medical treatment arms.
Looking at the ALS PCS and the associated companion document, there are multiple options with respect to the medical arm – fluid bolus, atropine, and dopamine. Of note, it is highlighted in both of these documents that in the presence of a symptomatic bradycardic patient, the initiation of transcutaneous pacing should not be delayed with the insertion of an IV. Thus, it is reasonable to apply your electrical treatment arm before the medical treatment arm.
As you are aware, these are often complex and difficult patients to manage. Progressive bradycardia is a harbinger of death and often considered a peri-arrest situation. Immediate pad placement is of the upmost importance in these situations. Bradycardia also predisposes the patient to pause dependent arrhythmias and having pads on a patient is always a great idea.
The differential for bradycardia is broad and vast, thus it is hard to predict which patients will respond to medical or electrical therapies. These patients often proceed down both arms simultaneously.
When selecting your treatment, patient presentation and a good assessment is of the utmost importance. While heart rate and blood pressure are the main components of said assessment, the patient’s mental status and perfusion (e.g. skin) are also important measures. For patients with mild symptoms of bradycardia, a more gradual and stepwise approach may be most appropriate.
With respect to the treatment options, remember that atropine is unlikely to be effective in high degree AV blocks. Moreover, as per the most recent AHA guidelines, the administration of atropine is considered to have a moderate benefit class of recommendation (COR 2a), with non-randomized associated level of evidence (LOE B-NR). Thus, the treatment can be useful/effective/beneficial. The ACLS guidelines also recommend atropine as a first-line medication.
If atropine is ineffective, alternative medications and/or electricity are reasonable next steps. Dopamine is another tool in your toolbox for these patients. As with any medication we give, dopamine is not immune to negative side effects. Not only can dopamine cause necrosis, but it is also dose dependant, and at higher doses, may act as a vasoconstrictor – an undesirable effect. Not to mention, it is difficult to set up in the pre-hospital environment, difficult to regulate, and hard to accurately manage. The use of dopamine requires careful attention to the correct dosing and administration. As per the guidelines, the administration of IV adrenergic agonists with rate-accelerating effects has weak benefits over risk (COR 2b), with limited data to support it (LOE C-LD). Thus it may/might be reasonable/considered.
As was mentioned before, the guidelines are supportive of initiating transcutaneous pacing (TCP) for severe symptomatic bradycardia if no parenteral access is available. If no veins are visible/palpable and the patient's presentation is acute, delaying transcutaneous pacing for multiple attempts may increase the risk of deterioration.
TCP is often the fastest way to increase HR, and even if it doesn’t work, the painful stimulus might be enough to trigger a compensatory sympathetic response. In line with that, it’s important to consider sedation and analgesia in these patients. Keep in mind, there is no need to patch for sedation and/or analgesia if the patient’s vital signs return to meeting the directive parameters.
You mentioned the high rate of failure, or lack of capture. One of the best measures of success, is ensuring your defib pads are placed in the right configuration. The anterior pad is on the left side of the lower part of the sternum, and the posterior pad directly behind it. Air (lungs), are a poor conductor of electricity, so capturing myocardium is important. As per the Companion Document:
“Transcutaneous pacing is to be initiated at a rate of 80 bpm with milliamps (mAmps) then increased to obtain electrical capture. Capture is highly variable depending on patient size, weight, pad placement, skin condition, etc. It is difficult to state the target values for capture, however 80 to 100 mAmps is common. If unable to gain capture at maximum mAmps, pacing should be discontinued. Treatment should not be discontinued if the patient responds and develops an improved blood pressure”
As with any treatment, it’s important to confirm mechanical capture. This can be done by looking at the pulse oximeter, the monitor, and/or feeling for a pulse (preferably far away from the chest).
At the end of the day, patients may receive multiple interventions to maintain their heart rate and blood pressure. The treatment provided must be permitted time to take effect and to be evaluated before moving on to the next treatment. the management will depend on both the underlying cause and severity of the clinical presentation.
As was discussed with the RPPEO medical team, atropine should be your first line medication (quick and easy to administer). If atropine is not effective (which is likely in high degree AV blocks) dopamine and TCP are your two remaining options.
Ultimately, we suggest using TCP as opposed to dopamine. Dopamine is impractical to set up in the prehospital setting. It is challenging to titrate without a pump and can lead to some serious side effects. For these reasons TCP is likely a better option as your second line therapy, but both have been shown to be effective.
We hope that this assists you in your approach, but if you have any further concerns, do not hesitate to reach out for further discussion.