The Approach To The Most Common Cardiac Dysrhythmia: 8 Causes of Sinus Tachycardia
Have you ever heard an entire lecture on sinus tachycardia? Neither have I. It is the most common cardiac dysrhythmia seen in critically ill adults and kids, but it is the least frequently talked about. Sinus tachycardia may not be the sexiest rhythm and we don’t think of cardioverting it or giving some new anti-arrhythmic drug, but it is a sign that something may be seriously wrong. To be fair, it’s not the sinus tachycardia we are really worried about, but rather what’s causing the sinus tachycardia that should be our main concern.
Sinus tachycardia, as one of my first ICU attending’s told me as an intern, is thinking mans (or women’s) rhythm. Sinus tachycardia is probably one of the most common reasons I was called to see a patient as a resident, but I did not have a systematic way to figuring out what could be causing it. As a critical care fellow, I was taught a simple and easy approach to sinus tachycardia by one of my favorite attendings, Paul Rogers MD.
This approach serves as a great start to figure out what could be seriously wrong with your patient and go through the most serious causes and moves down systematically. I hope this approach helps you as you care for critically ill adults and children in the future.
Note: This approach can be applied to patients with atrial fibrillation with rapid ventricular rate if they have chronic atrial fibrillation. New onset atrial fibrillation has a few different considerations. If your patient has chronic atrial fibrillation and they come in with a serious underlying medical condition they will have atrial fibrillation with rapid ventricular rate. Instead of quickly focusing only on trying to slow the rate, consider the underlying cause.
First, before we get into the causes of sinus tachycardia a small bit of physiology review. An understanding of how oxygen is distributed throughout your body is essential to understand the causes of sinus tachycardia. Cells need some very basic things to function properly, but nothing is more important to adequate cellular function than oxygen.
Oxygen needs to both be carried in the blood and adequately distributed to organs for optimal cellular function. This is exactly what the oxygen distribution equation (below) demonstrates.
This equation tells us what carries oxygen to cells:
- Adequate amounts of hemoglobin (Hb) are needed and the main way oxygen is carried to cells
- This hemoglobin needs to be saturated with oxygen (02 Saturation)
- PaO2-a small amount of oxygen is dissolved in plasma and carried to cells. In most cases this is not a significant amount of oxygen but optimizing a patients paO2 may be important especially in carbon monoxide poisoning or in severe anemia where Hb content is inadequate
It also tells us how oxygen is carried to cells:
- Cardiac Output: This is the means by which oxygen carried on hemoglobin and dissolved in the plasma reaches cells. Recall cardiac output is simply your heart rate multiplied by your stroke volume.
If your patient is in shock, from any cause they may have inadequate preload (hypovolemic shock from severe dehydration or hemorrhagic shock), or an obstruction of preload (obstructive shock), inadequate contractility (cardiogenic shock) or inadequate afterload (distributive shock). To maintain oxygen distribution to tissues in the setting of low stroke volume your patient may become tachycardic to maintain cardiac output. Your patient may be in early stages of shock, but able to maintain cardiac output, as well as, their blood pressure by increasing their heart rate.
Also notice if your patient becomes hypoxemic and they are now desaturating then unless you intervene for their hypoxemia with oxygen therapy and/or give positive pressure, the only way they may be able to increase oxygen distribution is to increase their heart rate.
Continuing to think of your patient in respiratory distress regardless of the cause, they will attempt to increase cardiac output to their lungs to improve perfusion. Additionally they will increase catecholamine release from the anxiety of their respiratory distress increasing their heart rate.
So the first three things that I assess in my patient with sinus tachycardia and that we have all been trained to assess is airway, circulation and breathing. These are my first 3 causes of sinus tachycardia.buyreplicawatches
To make my systematic approach to sinus tachycardia orderly I just keep adding letters…So after the A,B,C’s let’s examine D.
D is for Drugs and there are medications patients can take that can directly cause tachycardia and there are medications that patient may have stopped taking that can lead to tachycardia from withdrawal. I am not going to list all the drugs that directly cause tachycardia but some of the common ones I think of are: beta-agonist (albuterol), epinephrine, dopamine, dobutamine, amphetamines, cocaine, tricyclic antidepressants, and others. I also think about drugs that my patient may have recently stopped such as their alcohol (alcohol withdrawals), opiates, and benzodiazepines. Withdrawal especially from alcohol is always on my radar as alcohol withdrawal can carry a high morbidity and mortality even if caught early and treated adequately.
After D comes E and I go back to the oxygen distribution equation to understand the E.
E is for erythrocyte deficiency and the development of anemia regardless of whether it’s a rapid or slow process your patient may become tachycardic. If your patient develops anemia and has a decrease in hemoglobin, in order to compensate your patient will develop tachycardia in an attempt to increase cardiac output. Once again, if you look at the oxygen distribution equation (DO2), you can see that if your hemoglobin decreases, the only two thing that can increase to compensate for this are HR and SV.
F stands for fever, but truly anything that increases oxygen demands on the body may lead to increase in oxygen distribution, and once again your heart rate is usually to first to respond in attempt to increase cardiac output. There are countless causes of increase oxygen demands but the two I most commonly think about are fever and the possible development of infection or sepsis and hyperthyroid states.
G stands for glucose and if your patient develops hypoglycemia then they may have sympathoadrenal activation causing tachycardia as well as others symptoms such as tremors, diaphoresis, weakness, altered mental status and even seizures, coma and death.
And lastly, H or holy crap it hurts! Here I think of pain and anxiety as a cause of tachycardia but why put this last if it is so common? I do this on purpose as I never want to default to just simply thinking my patient is just in pain or anxious and giving analgesia or sedation without first thinking of more life threatening causes first.
Below are my 8 causes or categories that cause sinus tachycardia. I do realize this list is not completely exhaustive, but it is a nice comprehensive way to approach your undifferentiated patient that is tachycardic without an obvious reason.
This list may help you rule out some causes based on your history, exam, labs, and imaging and narrow it down to one or two causes. I hope this list gives you a systematic approach to helping your sick patient who presents with sinus tachycardia in the future.
As a critical care fellow, I was taught this simple and easy approach to sinus tachycardia by one of my favorite attendings, Paul Rogers MD.
Paul is a world-class medical educator, compassionate physician and friend. He inspired this post and has inspired countless medical students, as well as residents, fellows, and me over his many years of service.
Thank you Dr. Rogers!
For More on This Topic Checkout:
- Life In The Fast Lane: Sinus Tachycardia
Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)
The post The Approach To The Most Common Cardiac Dysrhythmia: 8 Causes of Sinus Tachycardia appeared first on REBEL EM - Emergency Medicine Blog.
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