Miriam E Tucker

May 27, 2016

Air travel across multiple time zones may require adjustment of diabetes medications, a new analysis of the literature finds. The issue is of most importance for those with type 1 diabetes or type 2 diabetic patients using insulin.

Results from the review of 13 articles, along with recommendations based on that information, were presented May 27 here at the American Association of Clinical Endocrinologists 2016 Annual Meeting by Rahul Suresh, MD, a second-year internal medicine and aerospace medicine resident at the University of Texas Medical Branch, Galveston.

"Travelers with diabetes face a lot of risks as far as managing their diabetes, especially with long-haul travel across time zones. They have to be prepared in advance, and that requires adjusting their insulin or oral diabetes medicines. With proper adjustments, we think we can help people avoid complications like hypoglycemia and have a safe trip," Dr Suresh told Medscape Medical News in an interview held prior to a press briefing where he discussed his findings.

The literature is limited and much of the evidence is anecdotal, but data suggest that up to 10% of people with diabetes encounter complications during travel, most commonly hypoglycemia. And of all medical emergencies requiring diversion of aircraft, up to 2% are due to diabetes.

"So it is a significant issue," Dr Suresh said during the briefing.

Ascent and Descent Tricky, Direction of Travel Important

Of particular concern is the situation when patients who take insulin are traveling east; they can develop hypoglycemia if they take their doses based on the time at origin, then shift to the new later time zone and therefore end up "stacking" their doses with so little time between meals. Conversely, when traveling west, the day lengthens and can result in gaps in medication dosing and hyperglycemia, he explained.

Insulin pumps on airplanes pose an additional danger — during ascent, the drop in ambient pressure can produce bubbles in the tubing or reservoir, resulting in inadvertent bolusing due to displacement of the insulin by the bubble. And on descent, insulin delivery may be blocked.

Studies in hyperbaric chambers have demonstrated that the amount of over- or underdelivery can total as much as a unit of insulin. And the rare event of rapid decompression can result in delivery of more than 8 extra units of insulin, Dr Suresh explained.

Asked to comment, Robert E Ratner, MD, chief scientific and medical officer of the American Diabetes Association, told Medscape Medical News that the increased use of long- and short-acting analogue insulins has made dosing adjustment less of an issue than in the past when NPH and regular insulins were used, but that "stacking" of short-acting insulin when flying east remains a problem.

"That's the circumstance where you want the shortest-acting insulin possible, or don't eat," he observed.

Dr Ratner added that he hadn't personally had patients report problems with pumps on airplanes, but that very long flights could be a concern. However, he has encountered patients on insulin pumps who experience problems due to air bubbles in areas of high altitude. "You tend to see high glucose levels when people go from sea level to high altitude and stay there."

Recommendations Based on Anecdotal Experience, Expert Opinion

Dr Suresh and colleagues identified 13 peer-reviewed articles or abstracts that provided recommendations pertaining to diabetes and air travel. Of those, 11 were based on expert opinion. Of the other two, one was a prospective cohort study and the other a cross-sectional survey of travelers with diabetes. Very few data were available on insulin-pump management or newer diabetes medications.

Based on that information, they devised several sets of recommendations for multiple-time-zone travel. Dose adjustments aren't necessary for prandial insulin (short/rapid-acting insulin) or insulin sensitizers. However, secretagogues (sulfonylureas and glinides such as repaglinide) should be held during eastward travel and sodium glucose cotransporter 2 (SGLT2) inhibitors held during all airline trips because they could increase the risk for dehydration, Dr Suresh advised.

For injected basal insulin (intermediate/long-acting insulins), different adjustments are needed, depending on whether the patient takes once or twice-daily dosing:

  • For passengers heading eastward (hypoglycemia risk), basal insulin dose should be reduced in proportion to hours lost. For single daily dosing, the traveler should reduce the dose (normal dose x 1.0 minus ([the number of time zones crossed]/[the number of hours between basal insulin doses]) at the normal time in the departure time zone, then set the clock to the destination time and give the full normal dose when due.

  • For twice-daily dosing heading east, the patient should take a reduced amount of the first dose (based on the above formula) at the normal time at departure. Then they should set their clock to destination time and give the full normal dose when due.

  • During westward travel (hyperglycemia risk), correction-scale insulin with rapid-acting insulin can be used or the dose to be administered during travel can be given as divided doses to span the longer travel day.

  • For those used to single dosing,the advice is to take half the normal dose when it is due in the departure time zone. Then, patients should immediately set their clocks to the destination time zone and take the second half of the dose when it would normally be due.

  • For patients who take basal insulin twice a day traveling westward, the normal morning dose should be taken the day of travel, then half of the second dose when it is due at the departure time. Then, after setting their clock to the destination time zone, they should give the remaining half of the second dose when due at the destination time.

For insulin-pump users, Dr Suresh and colleagues recommend the following:

  • No adjustments are needed in total daily dose.

  • The pump-clock time should be set to the destination time.

  • To avoid air bubble over- or underdelivery, pumps should be turned off and the cartridge disconnected during take-off. (Note: This isn't possible with the Omnipod [Insulet]. For that, Dr Ratner suggested using injected insulin the day of travel.)

  • Upon reaching cruising altitude, visible bubbles should be removed before reconnecting the pump cartridge, and the cartridge should only be filled with 1.5 mL of insulin during the flight.

  • Upon landing, the pump tubing should be disconnected and primed with 2 units of insulin prior to reconnection.

  • Patients should be advised to carry a supply of basal and prandial insulin as backup.

Dr Ratner commented that although these algorithms make sense, they may need to be tweaked and may not work for everyone.

"This is clinical judgment. This is going to change depending upon what your current regimen is, and it needs to be individualized for every single trip."

Indeed, Dr Suresh acknowledged, "Well-designed observational studies are needed to validate current recommendations."

Neither Dr Suresh nor Dr Ratner have relevant financial relationships.

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Endocr Pract. 2016;22 (Supp 2);73-74. Abstract 281

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