Passing out (syncope) is an incredibly common cause for an ER visit or hospital admission. There are many causes. Often the diagnosis is a retrospective best-guess based on the totality of circumstantial evidence. Fundamentally someone passes out when the whole brain suddenly loses blood flow (as opposed to a stroke where part of the brain loses blood flow; not the entire brain).
Syncope generally falls into a few large categories:
- Orthostatic – this is when someone stands up. Blood pressure from veins to the heart is suddenly reduced by gravity. Everyone has experience this. Ever stood up too quick and felt dizzy or lightheaded? That’s orthostasis. The body compensates for this (by a faster heart beat and blood vessel moderation), which is why after a few seconds you feel better; had it not you would have passed out. Anything which reduces the pressure in the venous system, or the heart’s compensation, contribute. Common culprits:
- Dehydration / Volume depletion – the “drier” you are the more it will happen. Reduced eating/drinking, sweating, taking fluid pills (diuretics), infection, etc.
- Medications – most medications which treat high blood pressure (hypertension) or the heart can cause orthostasis. Certain prostate medications (tamsulosin / Flomax, others in same group) are notorious for it. Certain psychiatric medications can also. When evaluating someone for orthostasis medications are my first stop. It is very common medications taken for different problems all cause additive side effects leading to a large drop in blood pressure.
- Primary medical conditions – many medical conditions cause orthostasis as part of the disease process. Parkinson’s disease is great example. Neuropathy (usually diabetic) also does.
- It is very common that multiple reasons come together to cause syncope. For example: an elderly man with Parkinsons and a big prostate taking Flomax and a fluid pill for his blood pressure didn’t eat well for a day and stood up from bed and passed out.
- Urinating or stooling – in order for us to release our urine or stool the body has to send a specific signal to allow the muscles to relax. This same signal causes blood pressure to drop some. Passing out from urinating is called micturation syncope. Common scenario: someone goes to the bathroom, urinates, stand up and passes out. Waiting 15-30 seconds after you finish urinating before standing up to wipe can avoid this.
2. Vasovagal – this type of syncope is caused by the vagus nerve. This nerve is more active for “rest and digest,” and thus it slows heart rate and blood pressure. Generally an unpleasant stimulus causes a sudden “fight or flight” impulse to start and the vagus nerve activates to counteract it. In vasovagal syncope the countering impulse overrides and abruptly reduces the blood pressure and slows the heart rate causing blood flow to the brain to suddenly drop and one passes out. If someone hears bad news in the movies and passes out this is why. Sudden pain and especially nausea are common causes. Most feel a sequence of warm, flushed, nausea/queasy, sweating, tunnel vision and then passing out. Some people have specific phobias that trigger it (like seeing blood). Humans are wired this way and there isn’t something “wrong.” It’s the impulse that precipitated it.
3. Cardiogenic – this type of syncope comes from the heart. Usually, an arrhythmia that suddenly changed the heart’s electrical signal to either too fast or too slow. This sudden change causes blood pressure to plummet. Cardiogenic syncope is the most concerning type and can be a harbinger for future events. In the hospital we monitor heart electrical signal (telemetry) for any types of arrhythmias which cause syncope. An ultrasound video of the heart (echocardiogram) is also frequently performed. This gives information on how the heart beats, chamber size, any valve problems and other information. The weaker or more diseased a heart is, the higher the risk for arrhythmias.
4. Seizure – while not an actual cause of syncope when someone loses consciousness we must determine if it was because a seizure or syncope. Some people twitch when they pass out leading to an erroneous diagnosis of seizure; and not everyone who has a seizure convulses.
5. Shock (distributive) – shock is when there is a severe drop in blood pressure. Infections (septic), pulmonary embolism, pericardial tamponade, hemo/pneumothorax (blood or improper air in lung) and other conditions can cause. These generally cause persistent low blood pressure when one passes out, it doesn’t resolve in a few minutes.
As you can see the differential diagnosis from syncope is vast and not always straight forward. Like patients, every case is different.
A common scenario for treatment is the administration of intravenous fluids to hydrate, hold or adjust offending medications, avoid patients standing up too quickly to see how they respond as we conduct other test to look for causes and give the body time to correct itself.
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