Can a Nerve Block in Shoulder Cause EKG Changes?
Yes, nerve blocks in the shoulder region can cause electrocardiogram (EKG) changes, particularly when the block affects the stellate ganglion or causes systemic effects from local anesthetic absorption.
Mechanisms of EKG Changes from Shoulder Nerve Blocks
- Shoulder region nerve blocks, particularly interscalene blocks, can affect the stellate ganglion, which plays a role in cardiac innervation and can lead to changes in repolarization patterns on EKG 1
- Blocks performed near the head and neck area may cause adverse reactions similar to systemic toxicity, including cardiovascular stimulation or depression that can manifest as EKG changes 2
- Intravascular injection of local anesthetics during shoulder blocks can lead to systemic toxicity with potential EKG manifestations 1, 2
- Phrenic nerve palsy, a common complication of interscalene blocks, may cause respiratory changes that indirectly affect cardiac function and EKG patterns 3
Types of EKG Changes That May Occur
- Primary repolarization abnormalities can occur due to sympathetic stimulation or ablation of the stellate ganglion, manifesting as ST-segment and T-wave changes 1
- Blocks near the brachial plexus can approach plasma concentrations that may lead to central nervous system toxicity and associated cardiac effects 2
- Potential EKG changes include:
Risk Factors for EKG Changes
- Pre-existing cardiovascular disease increases risk of EKG changes during nerve blocks 2
- Patients with impaired cardiovascular function may be less able to compensate for functional changes associated with prolongation of A-V conduction 2
- Patients on beta-blockers may not manifest expected heart rate changes but may show rises in systolic blood pressure 2
- High-dose local anesthetic administration, especially in highly vascularized areas like the shoulder region 2
Monitoring and Prevention
- Ultrasound guidance should be used to reduce the risk of local anesthetic systemic toxicity and inadvertent vascular injection 1
- Test doses containing epinephrine can help detect unintentional intravascular injection, which would manifest as increased heart rate and blood pressure within 45 seconds 2
- Continuous cardiac monitoring is recommended during and after shoulder nerve blocks, especially in high-risk patients 2
- Limiting local anesthetic dose and injection volume can reduce risk of systemic effects and phrenic nerve involvement 3
Clinical Considerations
- Alternative approaches like axillary or infraclavicular brachial plexus blocks may be preferred over supraclavicular or interscalene blocks to minimize respiratory and cardiovascular effects 1
- Targeting peripheral nerves supplying the shoulder (suprascapular and axillary nerves) may be an effective alternative to brachial plexus blockade in patients at high risk for cardiovascular complications 3
- The dose of pre-procedural sedation may need to be reduced to avoid respiratory compromise that could indirectly affect cardiac function 1
Management of EKG Changes
- If EKG changes occur during or after a shoulder nerve block, careful monitoring and assessment of hemodynamic stability is essential 2
- Resuscitative equipment and personnel should be immediately available when performing blocks in the head and neck area due to potential cardiovascular effects 2
- Most EKG changes are transient and resolve as local anesthetic levels decrease, but persistent or concerning changes warrant further cardiac evaluation 1
Special Considerations
- Patients receiving class III antiarrhythmic drugs (e.g., amiodarone) should have shoulder blocks performed with caution due to potential interaction effects 2
- Electrolyte imbalances can potentiate EKG changes from nerve blocks, particularly hypokalemia which can cause ST-segment depression and T-wave changes 4
- Patients with pre-existing bundle branch blocks or other conduction abnormalities may have more complex EKG interpretation challenges if changes occur during nerve blocks 1