IV-68 Circulation December 13, 2005 BRADYCARDIA Heart rate <60 bpm and inadequate for clinical condition Maintain patent airway; assist breathing as needed Give c Monitor ECG (identify rhythm), blood pressure, oximetry Signs or symptoms of poor perfusion caused by the bradycardia? (eg, acute altered mental status, ongoing chest pain, hypotension or other signs of sho Perfusion Pertusio Observe/Monitor Prepare for transcutaneous pacing use without delay for high-degree block (type ll second-degree block or third-degree AV block Consider atropine 0.5 mg IV while awaiting pacer, May repeat to a total dose of 3 mg. If ineffective, Consider epinephrine (2 to 10 ug/min) or dopamine (2 to 10 ug/kg per If pulseless arest develops, go to Pulseless Arrest Algorithm infusion while awaiting pacer or ir ute Search for and treat possible contributing factors: pacing ineffective Hypovolemia Tamponade, cardiac Hydrogen ion (acidosis)- Tension pneumothorax Hypo-/hyperkalemia- Thrombosis(coronary or pulmonary Prepare for transvenous pacing Trauma (hypovolemia, increased ICP) Treat contributing causes Consider expert consultation Fig aV blocks are classified as first, second, and third degre They may be caused by medications or electrolyte distur- In the absence of reversible causes, atropine remains the bances,as well as structural problems resulting from acute first-line drug for acute symptomatic bradycardia(Class lla) myocardial infarction and myocarditis. A first-degree AV In I randomized clinical trial in adults (Loe 2)5 and addi- block is defined by a prolonged PR interval(>0.20 second tional lower-level studies(LOE 4), 6.7 IV atropine improved and is usually benign. Second-degree AV block is divided heart rate and signs and symptoms associated with bradycar into Mobitz types I and Il. In Mobitz type I block, the block dia. An initial dose of 0.5 mg, repeated as needed to a total of is at the AV node; the block is often transient and may be 1.5 mg, was effective in both in-hospital and out-of-hospital asymptomatic. In Mobitz type II block, the block is most dycardia 5-7 Transcutaneous often below the Av node at the bundle of His or at the bundle pacing is usually indicated if the patient fails to respond to atropine, although second-line drug therapy with drugs such branches: the block is often symptomatic, with the potential atropine, although to progress to complete(third-degree) Av block. Third- as dopamine or epinephrine may be successful(see below) degree heart block may occur at the Av node, bundle of Hi Use transcutaneous pacing without delay for symptomatic high-degree(second-degree or third-deg gree)block. Atropine bundle branches. When third-degree AV block is present, sulfate reverses cholinergic-mediated decreases in heart rate no impulses pass between the atria and ventricles. Third- and should be considered a temporizing measure while degree heart block can be permanent or transient, depending awaiting a transcutaneous pacemaker for patients with symp on the underlying cause tomatic high-degree AV block. Atropine is useful for treating symptomatic sinus bradycardia and may be beneficial for any Therapy(Box 4) type of AV block at the nodal level. 7 Be prepared to initiate transcutaneous pacing quickly in The recommended atropine dose for bradycardia is 0.5 m patients who do not respond to atropine(or second-line drugs IV every 3 to 5 minutes to a maximum total dose of 3 mg if these do not delay definitive management). Pacing is also Doses of atropine sulfate of <0.5 mg may paradoxically recommended for severely symptomatic patients, especially result in further slowing of the heart rate. 8 Atropine admin- when the block is at or below the His-Purkinje level (ie, type for patients with poor perfusion istration should not delay implementation of external pacing II second-degree or third-degree Av block)AV blocks are classified as first, second, and third degree. They may be caused by medications or electrolyte distur￾bances, as well as structural problems resulting from acute myocardial infarction and myocarditis. A first-degree AV block is defined by a prolonged PR interval (0.20 second) and is usually benign. Second-degree AV block is divided into Mobitz types I and II. In Mobitz type I block, the block is at the AV node; the block is often transient and may be asymptomatic. In Mobitz type II block, the block is most often below the AV node at the bundle of His or at the bundle branches; the block is often symptomatic, with the potential to progress to complete (third-degree) AV block. Third￾degree heart block may occur at the AV node, bundle of His, or bundle branches. When third-degree AV block is present, no impulses pass between the atria and ventricles. Third￾degree heart block can be permanent or transient, depending on the underlying cause. Therapy (Box 4) Be prepared to initiate transcutaneous pacing quickly in patients who do not respond to atropine (or second-line drugs if these do not delay definitive management). Pacing is also recommended for severely symptomatic patients, especially when the block is at or below the His-Purkinje level (ie, type II second-degree or third-degree AV block). Atropine In the absence of reversible causes, atropine remains the first-line drug for acute symptomatic bradycardia (Class IIa). In 1 randomized clinical trial in adults (LOE 2)5 and addi￾tional lower-level studies (LOE 4),6,7 IV atropine improved heart rate and signs and symptoms associated with bradycar￾dia. An initial dose of 0.5 mg, repeated as needed to a total of 1.5 mg, was effective in both in-hospital and out-of-hospital treatment of symptomatic bradycardia.5–7 Transcutaneous pacing is usually indicated if the patient fails to respond to atropine, although second-line drug therapy with drugs such as dopamine or epinephrine may be successful (see below). Use transcutaneous pacing without delay for symptomatic high-degree (second-degree or third-degree) block. Atropine sulfate reverses cholinergic-mediated decreases in heart rate and should be considered a temporizing measure while awaiting a transcutaneous pacemaker for patients with symp￾tomatic high-degree AV block. Atropine is useful for treating symptomatic sinus bradycardia and may be beneficial for any type of AV block at the nodal level.7 The recommended atropine dose for bradycardia is 0.5 mg IV every 3 to 5 minutes to a maximum total dose of 3 mg. Doses of atropine sulfate of
0.5 mg may paradoxically result in further slowing of the heart rate.8 Atropine admin￾istration should not delay implementation of external pacing for patients with poor perfusion. Figure 1. Bradycardia Algorithm. IV-68 Circulation December 13, 2005