Syncope at 30,000 Feet

Author:
John Riefler, MD, MS

Citation:
Riefler J. Syncope at 30,000 feet. Consultant. 2017;57(9):561.

Halfway across the Atlantic Ocean, on a night flight from Newark, New Jersey, to Birmingham, England, an announcement came over the intercom asking for a physician or nurse to make his or her presence known. I didn’t hesitate to respond. With heart racing, I stood up, went to the back of the airplane, and asked the flight attendant if I could help.

A 60-year-old man had fainted and had hit his head on the lavatory door. He was now sitting down and was receiving oxygen by mask. My physical examination found him to be alert but disoriented, with his pupils equal and reactive to light, and no scalp lacerations. His heart rate was 60 beats/min and regular, his blood pressure was 140/70 mm Hg, and his respiration rate was 18 breaths/min. Because of space limitations in the rear of the aircraft, and because the patient had fallen, I did not attempt to check for orthostatic changes.

His history included hypertension treated with indapamide and type 2 diabetes controlled with metformin. He had experienced 1 previous orthostatic hypotension episode, which he had attributed to indapamide. (Orthostatic hypotension as an adverse reaction to indapamide has an occurrence rate of less than 5%.¹)

The man had had a glass of wine earlier on the flight. He said that he had eaten earlier in the day, and he did not have symptoms of tremor, palpitations, anxiety, diaphoresis, or hunger.

After 5 minutes, the patient said he felt fine. He drank water and had no further symptoms in the final 4 hours of the flight.

A Common In-Flight Problem

Syncope is a sudden, brief loss of consciousness associated with a loss of postural tone from which a person recovers spontaneously.² It has 3 general categories: neural mediated syncope (reflex syncope), orthostatic hypotension, and cardiac syncope.²

Of the 11,920 in-flight medical emergency calls reported by 5 domestic and international airlines from January 1, 2008, through October 31, 2010, syncope or presyncope accounted for 37.4% of cases.³ On 1 major international carrier’s flights in the 6 months between June 2002 and December 2002, 507 voyage report forms were completed for in-flight medical emergencies.⁴ Syncope accounted for 25% of all incidents and 91% (128/140) of all new medical problems; this figure is comparable to the 35% incidence rate recorded in a previous 1996 report.⁴

At a cruising altitude of 36,000 to 40,000 ft, cabin pressure is maintained at the approximate equivalent of 6000 to 8000 ft above sea level,⁵ from 77 to 82 kPa. Given that standard barometric pressure at sea level is 101 kPa, only 76% to 81% of the oxygen that would be available at sea level is available aboard the aircraft.⁶ Accordingly, oxygen is the most commonly used medical therapy aboard commercial flights.³

Predisposing factors for syncope include motionless upright posture, intravascular volume depletion, alcohol ingestion, and hypoxemia.² Standing results in pooling of up to 1000 mL of blood in the lower extremities, accompanied by decreased venous return to the heart and diminished cardiac output and blood pressure.² On an airplane, most syncopal events occur when a person stands up after prolonged sitting.⁴ Thus, ankle and leg exercises should be done prior to rising from a seat to reduce the risk of syncope. The patient on my flight had not exercised his legs after having flown 2000 miles.

Guidance for a responding clinician includes blood pressure and pulse measurement, because intravascular volume depletion or bradycardia commonly cause syncope.⁷ Patients with persistent hypotension may need intravenous fluids. Risk stratification is crucial, especially for elderly passengers with cardiac disease; a responding clinician should consider recommending flight diversion in such cases given the increased risk of death.

A Happy Landing

I checked on the man several times during the rest of the flight. He had no further syncopal symptoms. When we landed, the flight crew thanked me for helping. A flight attendant told me that fainting episodes occur about once a month on her carrier’s flights, so health care providers should be aware that syncopal episodes are common during flights, and their assistance may be needed even halfway across the Atlantic Ocean. 

John Riefler, MD, MS, is director of medical monitoring and consulting at PSI Pharma Support America, a contract research organization in King of Prussia, Pennsylvania.

References:

1. Lozol [package insert]. Bridgewater, NJ: Aventis Pharmaceuticals Inc; 2005.
2. Freeman R. Syncope. In: Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J, eds. Harrison’s Principles of Internal Medicine. Vol 1. 18th ed. New York, NY: McGraw-Hill; 2012:171-178.
3. Peterson DC, Martin-Gill C, Guyette FX, et al. Outcomes of medical emergencies on commercial airline flights. N Engl J Med. 2013;368(22):2075-2083.
4. Qureshi A, Porter KM. Emergencies in the air. Emerg Med J. 2005;22(9):​658-659.
5. Cabin air pressure. In: World Health Organization. International Travel and Health: Situation as on 1 January 2012. Geneva, Switzerland: World Health Organization; 2012:14. http://who.int/ith/ITH_EN_2012_WEB_1.2.pdf?ua=1. Accessed July 13, 2017.
6. Altitude air pressure calculator. Altitude.org website. http://www.altitude.org/air_pressure.php. Accessed July 13, 2017.
7. Nable JV, Tupe CL, Gehle BD, Brady WJ. In-flight medical emergencies during commercial travel. N Engl J Med. 2015;373(10):939-945.