What is the best course of treatment for a patient experiencing nausea and bradycardia (abnormally slow heart rate)?

Management of Nausea and Bradycardia

Immediate Treatment Algorithm

Administer atropine 0.5-1 mg IV as first-line therapy for symptomatic bradycardia, repeating every 3-5 minutes up to a maximum total dose of 3 mg, while concurrently treating nausea with antiemetics such as metoclopramide 5-10 mg IV. 1, 2, 3

First-Line Intervention

• Atropine is the initial drug of choice for symptomatic bradycardia with a starting dose of 0.5-1 mg IV push 1, 2, 3, 4
• Repeat atropine every 3-5 minutes as needed, up to a maximum cumulative dose of 3 mg 1, 2, 3
• Critical warning: Doses less than 0.5 mg may paradoxically worsen bradycardia through a transient vagal stimulation effect and must be avoided 2, 3, 4

Concurrent Nausea Management

• Administer antiemetics concurrently with opioids or atropine, specifically metoclopramide 5-10 mg IV 1
• Important consideration: If the patient received opioids (morphine 4-8 mg IV) for pain relief, nausea is a known side effect that typically responds to antiemetics 1
• The combination of nausea and bradycardia may indicate opioid-induced vagal stimulation, which responds well to atropine 1

Second-Line Therapies (If Atropine Fails)

Chronotropic Infusions

• Dopamine 5-10 mcg/kg/min IV infusion is the preferred second-line agent, titrated every 2 minutes by 5 mcg/kg/min increments based on heart rate and blood pressure response 1, 2
• Dopamine provides dose-dependent chronotropic and inotropic effects at 5-20 mcg/kg/min, with lower doses (1-2 mcg/kg/min) causing vasodilation 1, 2
• Alternative option: Epinephrine 2-10 mcg/min IV infusion if dopamine is ineffective or if severe hypotension requires both strong chronotropic and inotropic support 1, 2

Transcutaneous Pacing

• Initiate transcutaneous pacing immediately in unstable patients who do not respond to atropine, particularly those with hypotension (systolic BP <80 mmHg) or signs of shock 1, 2, 3
• Transcutaneous pacing serves as a temporizing measure while preparing for definitive therapy and may require sedation/analgesia due to discomfort in conscious patients 2, 3
• Do not delay pacing while administering multiple atropine doses in hemodynamically unstable patients 2, 3

Critical Clinical Considerations

Effectiveness Based on Rhythm Type

• Atropine is most effective for sinus bradycardia, AV nodal block, or sinus arrest 2, 3
• Atropine may be ineffective in type II second-degree AV block or third-degree AV block with wide QRS complex, where the block is in non-nodal (infranodal) tissue 2, 3
• In these cases, proceed directly to transcutaneous pacing or chronotropic infusions rather than repeating atropine 2, 3

Special Populations and Contraindications

• Heart transplant patients: Avoid atropine as it may cause paradoxical high-degree AV block or sinus arrest due to lack of vagal innervation; use epinephrine instead 1, 2
• Acute coronary ischemia/MI: Use atropine cautiously as increased heart rate may worsen ischemia or increase infarct size; limit total dose to 0.03-0.04 mg/kg in patients with known coronary artery disease 1, 2, 3

Common Pitfalls to Avoid

• Never administer atropine doses <0.5 mg as this can paradoxically slow heart rate further through initial vagal stimulation 2, 3, 4
• Do not exceed dopamine doses of 20 mcg/kg/min as higher doses cause excessive vasoconstriction and increase arrhythmia risk 1, 2
• Avoid NSAIDs for pain relief in this setting due to potential prothrombotic effects 1
• Atropine administration should not delay implementation of transcutaneous pacing in patients with poor perfusion 2, 3

Monitoring and Supportive Care

• Maintain patent airway and provide supplemental oxygen (2-4 L/min) if the patient is hypoxemic or shows signs of respiratory distress 1, 2
• Establish continuous cardiac monitoring to identify rhythm changes and monitor blood pressure and oxygen saturation 2, 3
• Establish IV access immediately for medication administration 2, 3
• Obtain a 12-lead ECG to identify the specific type of bradycardia and guide treatment decisions 1, 2

Disposition and Escalation

• Transfer to ICU or step-down unit is necessary if the patient requires continuous chronotropic infusions (dopamine or epinephrine) as these medications mandate continuous cardiac monitoring 2
• Bradycardia with hypotension and signs of shock is associated with increased mortality and requires aggressive treatment and higher level of care 2
• Place transcutaneous pacing pads prophylactically in high-risk patients even if not immediately pacing 2