Concerns About Slow Heart Rate During Regional Anesthesia

Q: Concerns About Slow Heart Rate During Regional Anesthesia

Hello Mr. <br>Zhang： Your question can be answered in two parts. <br><br>1. <br>Does spinal anesthesia cause a slower heart rate? Spinal anesthesia involves administering medication into the spinal canal, which blocks sensory nerve transmission while also affecting motor nerve fu

Bradycardia during anesthesia

I would like to ask the doctor, I am scheduled for a surgery with regional anesthesia soon, but when I measure my blood pressure at home, I sometimes record a heart rate of only 40 to 50 beats per minute.
Will my heart rate become even slower during anesthesia, and is this dangerous? Thank you.

Xiao Zhang, 40~49 year old female. Ask Date: 2014/05/04

Dr. Lin Xiuying reply Anesthesiology

Hello Mr.
Zhang: Your question can be answered in two parts.

1.
Does spinal anesthesia cause a slower heart rate? Spinal anesthesia involves administering medication into the spinal canal, which blocks sensory nerve transmission while also affecting motor nerve function.
Spinal anesthesia typically lasts for 4-6 hours and is generally recommended for lower body surgeries.
For surgeries above the umbilicus, it is less advisable due to the broader range of anesthetic effects and higher physiological impact, unless the anesthesiologist has specific considerations.
The extent of the anesthetic's effect depends on how far the medication spreads within the spinal canal; if it reaches the upper thoracic region, the heart rate may slow down because it affects the nerves that regulate cardiac rhythm.
2.
What are the risks of a slower heart rate? The primary risk associated with heart rate is whether it can maintain the metabolic demands of peripheral cells in conjunction with the cardiac output.
If the cardiac output is sufficient, the heart rate does not need to be excessively fast, which is why some athletes have a lower resting heart rate.
However, it cannot be too slow; as previously mentioned, it must sustain physiological metabolism.
Otherwise, physiological changes may occur, such as decreased blood pressure, dizziness, nausea, or even shortness of breath.
The aforementioned points outline the risks related to heart rate during spinal anesthesia.
For you, if your heart rate is currently slower (I wonder if you are an athlete or have a regular exercise routine?), and if this heart rate can maintain your normal physiological metabolism, it indicates that your cardiac output is adequate.
If, after anesthesia, your heart rate remains within about 10% of your usual slower range and blood pressure does not fluctuate significantly, it should be safe (though this still depends on real-time physiological responses, as monitoring is crucial).
If there is a tendency for both heart rate and blood pressure to decrease, the anesthesiology staff will assess the situation and may administer appropriate cardiovascular medications to ensure the patient's physiological stability and safety.
Patients can remain awake under spinal anesthesia, and any physiological changes (uncomfortable sensations) can be communicated to the anesthesiology staff, which is a good way to enhance your safety during anesthesia.
Finally, I wish you a "smooth surgical anesthesia." If you have any further questions, feel free to inquire again at "Taiwan e-Hospital." Thank you!

Reply Date: 2014/05/04

More Info

When preparing for a procedure involving regional anesthesia, it is essential to consider your baseline heart rate and any underlying health conditions that may affect your cardiovascular response during the procedure. A heart rate in the range of 40 to 50 beats per minute (bpm) can be concerning, particularly if it is accompanied by symptoms such as fatigue, dizziness, or shortness of breath. However, in some individuals, especially those who are physically fit or athletes, a lower resting heart rate can be normal and not indicative of any underlying pathology.

During regional anesthesia, the anesthesiologist will closely monitor your vital signs, including heart rate and blood pressure. If your heart rate is already on the lower side, there is a possibility that it could decrease further during the procedure, particularly if the anesthetic affects the autonomic nervous system, which controls involuntary bodily functions, including heart rate. This is especially true if the anesthesia leads to vasodilation (widening of blood vessels), which can lower blood pressure and potentially cause reflex bradycardia (a slower heart rate).

Your history of sinus bradycardia (slow heart rate) and any existing heart conditions, such as mitral valve prolapse or sinus node dysfunction, should be communicated to your anesthesiologist. They may take extra precautions, such as administering medications to stabilize your heart rate or ensuring that you are adequately hydrated before the procedure. Additionally, they may choose to monitor you more closely during the surgery to detect any significant changes in your heart rate or blood pressure.

It is also worth noting that the heart rate can be influenced by various factors, including anxiety, pain, and the body's response to anesthesia. If you have experienced episodes of fatigue or weakness associated with your low heart rate, it is crucial to discuss these symptoms with your healthcare provider before the procedure. They may recommend further evaluation, such as an echocardiogram or a Holter monitor, to assess your heart's function and rhythm more comprehensively.

In summary, while a heart rate of 40 to 50 bpm can be concerning, especially in the context of undergoing regional anesthesia, it is essential to have a thorough preoperative assessment. Your anesthesiologist will take your baseline heart rate and any underlying conditions into account to ensure your safety during the procedure. Open communication with your healthcare team about your concerns and symptoms will help them provide the best care tailored to your needs.

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