You almost pass out with diarrhea because severe fluid loss causes dehydration and low blood pressure, reducing blood flow to the brain, while the intense straining during bowel movements can trigger a vagal response (vasovagal syncope), overstimulating the vagus nerve, slowing your heart rate, and causing a sudden drop in blood pressure, leading to dizziness and fainting.
Based on your description, some possible conditions could include: Severe dehydration from prolonged diarrhea. Viral or bacterial gastroenteritis. Inflammatory bowel disease (like Crohn's or ulcerative colitis)
Vagal Response During Bowel Movements
To prevent this from happening, try to keep yourself relaxed. Sit on the toilet with your head down and your legs crossed. This may help to keep your blood pressure steady.
Vasovagal syndrome (neurocardiogenic syncope).
It's caused by a problem with overstimulating the nerves that have direct input on the heart and blood vessels. This is the most common cause of syncope and can follow periods of extreme emotion.
As well as more common GI symptoms, IBS is also thought to give rise to a number of non-GI symptoms including dizziness. Dizziness can be described as a feeling of unsteadiness, light-headedness or feeling faint.
More than one third of patients with defecation syncope die within 2 years of complications of their underlying diseases. Alcohol intake is an important precipitating factor for micturition syncope in younger patients (less than 55 years of age), but it is rarely a factor associated with defecation syncope.
Bowel infections can be caused by viruses, bacteria and parasites. Severe symptoms include ongoing diarrhoea, fever, blood or mucus in your poo and dehydration.
Symptoms of Syncope
Vasovagal syncope usually occurs during upright posture, but Jardine et al. have described a variant that occurs at night. During “sleep syncope”, patients are awakened from sleep with nausea, abdominal cramping or a sense of impending diarrhea, get up, and faint in the bathroom.
Vasovagal syncope may have a genetic predisposition. It has a high prevalence in some families, and children of a fainting parent are more likely to faint than those without a parent who faints. Having two fainting parents or a fainting twin increases the likelihood even further.
Straining during a bowel movement, particularly if the stool is hard or large, increases pressure in the abdomen and chest. This increased pressure can stimulate the vagus nerve, triggering a vasovagal response.
Vasovagal syncope is the most common cause of fainting. It happens when the blood vessels open too wide or the heartbeat slows, causing a temporary lack of blood flow to the brain. It's generally not a dangerous condition. To prevent fainting, stay out of hot places and don't stand for long periods.
In patients with POTS, during upright tilt, sympathetic tone increases, there is an early and sustained tachycardia, and patients complain of presyncope without frank syncope. In contrast, patients with VVS experience delayed symptoms and abrupt drops in BP and HR and are more likely to lose consciousness.
If you pass out, you should receive emergency medical care right away. Serious or life-threatening conditions can cause vasovagal syncope. A healthcare provider should examine you right away to determine if a more severe condition caused you to faint.
Dumping syndrome is a condition in which food moves from the stomach into the small intestine too quickly after eating, more commonly seen after certain surgeries. It's sometimes called rapid gastric emptying. Dumping syndrome most often happens after surgery on the stomach or esophagus.
While occasional loose stools are usually harmless, the following warning signs indicate you should schedule an evaluation:
Diarrhea can have many causes, including infections of the digestive tract, irritable bowel syndrome, food poisoning, or antibiotic use. Likewise, fainting can have many causes including low blood pressure, abnormal heart rhythms, dehydration, and other conditions.
During a vasovagal syncope episode, your heart rate slows, and the blood vessels in your legs widen. This allows blood to pool in your legs, which lowers your blood pressure. The drop in blood pressure and slowed heart rate quickly reduce blood flow to your brain, and you faint.
Dizziness or fainting. Hoarseness, wheezing or loss of voice. Loss of appetite, feeling full quickly or unexplained weight loss. Nausea and vomiting.
Presyncope is staying conscious while feeling like you're about to faint. Some providers call this common condition near syncope. Syncope is a medical term for fainting. Presyncope (pree-sing-kuh-pee) can last a few seconds to a few minutes.
Reflex syncope is the most frequent cause of fainting. Vasovagal syncope — the common faint — occurs in one third of the population. It is by far the most common form of reflex syncope. Vasovagal syncope is often triggered by a combination of dehydration and upright posture.
This can happen when the vagus nerve is overstimulated. Vasovagal symptoms include dizziness, lightheadedness, nausea, and sweating. Severe cases may cause syncope, or loss of consciousness. Pain, nausea, fear, and straining for a bowel movement are common causes of vasovagal syncope.
These symptoms can happen with all forms of gastroenteritis (both viral and bacterial). High fever and bloody diarrhea are more common with bacterial gastroenteritis. The symptoms of bacterial gastroenteritis may look like other medical conditions or problems. Always talk with your healthcare provider for a diagnosis.
The main symptoms of ulcerative colitis are:
Consult your health care provider if you notice unusual or unexplained changes in your bowel movements, such as: