Why staying cool is so vital

The great Winston Churchill once said: “I have nothing to offer but blood, toil, tears and sweat.” In international air ambulance operations at Unicair, we are slightly more optimistic on our portfolio; however, a good offering of blood en route is far from trivial. 

Case report

Unicair was tasked to evacuate a 55-year-old gentleman with a history of non-alcohol-induced liver cirrhosis from Port Gentil, Gabon, to Hamburg, Germany. The patient underwent emergency gastroscopy in Gabon and a diagnosis of a moderate upper gastrointestinal (GI) bleed with oesophageal varices was made. The bleeding was stopped, and the patient presented in a stable cardio-respiratory situation with an Hb of 7.8 g/dl and platelets of 198 G/l. Nevertheless, considering the long flight time of 7.5 hours in our CL604 and the limited diversion points en route, a decision was made to carry six blood group 0 Rh negative packed red cell concentrates (PRCs) to be able to stabilise the patient in the event of a re-bleed.

We used an APRU 6L Autonomous Portable Refrigeration Unit (APRU, Delta Development Team, Tucson, Arizona, US). This is a Food and Drug Administration (FDA) and Federal Aviation Administration (FAA) certified and approved device to store up to six 500ml PRC units at 4.5°C ± 0.8°C.

During the flight, the unit is running connected to the aircraft’s electrical system; at layovers, the unit can keep the internal temperature constant for 96 hours using integrated battery power. Temperature data is recorded and stored every four hours for a duration of 72 days. Accuracy is ± 1°C, class 2 (k=2) with an NIST traceable calibration. Hb measurements in-flight were enabled by an Abbott i-STAT point-of-care blood gas analyser with the respective cartridge while a Sengstaken-Blakemore sonde was available as ultima ratio in case of a catastrophic bleeding event.

At pick-up at the blood product service of the Frankfurt University Hospital, the PRCs were placed in the APRU, and the unit was delivered by a company driver to the aircraft. The aircraft was then pre-positioned to Libreville, Gabon (seven-hour flight), for an 18-hour crew rest. On the following day, the patient was transported with an uneventful air ambulance flight to Hamburg, where he reached his final destination in the University Hospital without the need for a transfusion while in transit.

Discussion

Over the last decade, the lifesaving impact of pre-hospital transfusion has been well established in emergency medical services (EMS), including helicopter-based aeromedical programmes (HEMS). Transfusion in long-range fixed-wing international missions, however, is hindered by additional challenges, which are mostly focused on adequate storage and temperature tracking of blood products over prolonged time periods, including long positioning flights and crew rest times at the patient’s pick-up location of up to 24 hours.

Passive cooling devices such as insulation boxes with cool packs are lightweight and suitable for HEMS operations but cannot keep a constant temperature over such extended mission profiles. We have used a combination of portable fridges, temperature tracking devices and battery packs in the past, but an integrated device offers better handling, superior safety and certification.

Also, in case of a well-documented, non-interrupted cool chain in a verified cooling device, unused PRCs might be returned to the hospital’s blood service to prevent wasting a limited and valuable resource, which justifies the considerable investment in acquiring such a unit.