Identification and Treatment of Unstable Bradycardia
Patients with a heart rate less than 60 are bradycardic. Some people can have a resting heart rate in the 40s without any compromise. For others, a heart rate of 50 or less could signify the need for immediate intervention and warrants additional assessment. Similar to the tachycardia algorithm, one of the first questions we should ask ourselves about a bradycardic patient with a heart rate less than 50 is, “Are they stable?” The identification and treatment of unstable bradycardia is today’s Pass ACLS tip topic.
Identification
We should assess our bradycardic patient’s vitals, level of consciousness, pulse ox, and perform a targeted history of the patient’s current condition.
Bradycardic patients with any of the following are considered unstable:
- hypotension as indicated by a systolic Blood Pressure below 90;
- a sudden decrease in level of consciousness;
- signs of shock – like cool, clammy, ashen to cyanotic skin, or delayed capillary refill;
- signs of acute CHF – such as SOB, edema, and wet breath sounds; or
- complaints of chest discomfort suggestive of possible cardiac ischemia.
If any of those exist, the patient should be considered unstable and have ACLS interventions started.
A 12 lead ECG should be obtained and a quick review of the patient’s medical history and current medications performed to determine if the bradycardia could be a toxicologic etiology. For example, Calcium channel blockers and beta blockers can cause bradycardia and may respond favorably to targeted treatment. Calcium in the case of calcium channel blockers and glucagon administration for beta blockers. (Tablets & Toxins are covered in a separate Pass ACLS Tip of the Day)
Treatment of Unstable Bradycardia
Patients with a SaO2 less than 90% should be started on Oxygen while we obtain an IV. Based on the patient’s history, a fluid bolus of 250-500 cc could be started. The IV should be kept at KVO for patients with renal failure or signs of acute CHF.
Administration of 1 mg of Atropine rapid IV Push is our first medication. This dose can be repeated twice in 3-5 minutes intervals to a maximum total dose of 3 mg. Atropine is unlikely to be effective for patients with a heart transplant or patients in a second degree type two or third degree heart block. If, after our first dose of atropine, we see an increased rate of P waves on the ECG but no increase in the patient’s pulse or QRSs, subsequent doses of atropine are unlikely to be effective and can be skipped.
Transcutaneous Pacing (TCP) should be started as soon as possible for unstable bradycardic patients refractory to Atropine.
If there’s a delay in getting TCP, an infusion of Dopamine or Epinephrine can be started. Dopamine at 5-20 mcg/kg/min or 2-10 mcg/min for an epi drip. If a dopamine or epi drip is started, we should begin at the lowest rate and slowly titrate up to a systolic BP of 90. These medications increase the workload of the heart and can worsen ischemia so use with caution and maintain close monitoring of these patients.
