Faint of heart

When the brain is not getting enough blood flow, it will do whatever it can to try to increase the flow and pressure. The easiest mechanism it has at its disposal to do that is to make the person lie down or “faint.” There are some other reasons why a person may “faint,” like a toxic chemical effect to the brain or a bleed, but I am only addressing the most common types such as vasovagal syncope.

The vagus nerve controls “automatic” functions like heart rate, dilatation of blood vessels, and digestion. Various neurologic inputs can cause vagus nerve stimulation which lowers blood pressure and may result in syncope. Pain is one of the most common causes of syncope. You may not think it occurs in the cockpit, but pain is the most frequent stimulus of fainting by passengers on airlines.

Most often, in-flight pain is from gastrointestinal distress. The stomach and intestines are very sensitive to stretching. Gas in particular, which increases with altitude even in pressurized aircraft, can cause the stomach and intestines to stretch, leading to significant pain and potentially resulting in syncope.

Obviously, this is of concern to the FAA especially when pilots are involved. If a pilot has a syncopal episode, in the air or the ground, the cause is important to identify. Although most syncope is related to the vasovagal response, it also could be caused by an irregular heartbeat or low blood pressure from medication or dehydration. Also, some people restrict salt to such an extent that even with lots of fluid intake, they will not “hold” fluid in their intravascular system, causing symptomatic low blood pressure even though they’re well hydrated.

The evaluation of a fainting episode involves taking a detailed history of the events leading up to the episode, the episode itself, and the person’s condition afterward. Most classic vasovagal episodes are diagnosed without any testing because of precipitating factors such as pain, receiving bad news, or a history of not eating or hydrating for extended periods of time.

Most vasovagal fainting is not serious or dangerous unless the person is unable to lie down, or if a fall to the ground causes trauma to the head or other parts of the body.

Syncope is of more concern when there are no precipitating factors or when it occurs multiple times. A serious problem called sick sinus syndrome occurs with the heart’s built-in pacemaker functions abnormally. This can cause very slow heart rates as well as long pauses—both of which can cause fainting. Fortunately, the installation of an artificial pacemaker cures this problem.

If a detailed history does not identify the cause of fainting, a physical examination may reveal low blood pressure, abnormal heart sounds suggesting a valve problem, or an irregular heart rhythm. If required, additional testing is generally done with an ultrasound of the heart, a 24-hour or longer monitoring of the heart rhythm, and sometimes an exam on a tilt table which is compared by some patients to a carnival ride.

When a heart valve problem is detected after fainting, it may be the first sign that a valve is not working properly and needs repair or replacement.

The best immediate treatment for fainting is to safely lay the person down and elevate their legs to increase blood return to the heart. The old-fashioned technique of putting one’s head between one’s knees while in a sitting position is not an effective measure.

Low blood sugar and some medications can precipitate fainting as well. Hydration as well as eating before and during flight helps prevent low blood sugar and dehydration. Pilots should always be cautious about medications, particularly if they are new medications. Pilots should not fly after taking new medications for the first few times. Remember that over-the-counter medications and supplements can cause side effects just like prescription medications. Also remember that altitude increases many of the neurologic side effects of medications.

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