Objective: After severe (primary) brain injury, Dutch physician-based helicopter emergency medical services start therapy to lower the intracranial pressure (ICP) on scene to stop or delay secondary brain injury. In some cases, helicopter transportation to the nearest level 1 trauma center is indicated. During transportation, the head-down position may counteract the ICP-lowering strategies because of venous blood pooling in the head. To examine this theory, we measured the optic nerve sheath diameter (ONSD) during helicopter transport in healthy volunteers.
Methods: The ONSD was measured by ultrasound in healthy volunteers during helicopter liftoff and acceleration in the supine position or with a raised headrest.
Results: In this proof-of-principle study, the ONSD increased during helicopter acceleration (-9° Trendelenburg, mean = 5.6 ± .3 mm) from baseline (0° supine position, mean = 5.0 ± .4 mm). After headrest elevation (20°-25°), the ONSD did not increase during helicopter acceleration (mean ONSD = 5.0 ± .5 mm).
Conclusion: ONSD and ICP seem to increase during helicopter transportation in -9° head-down (Trendelenburg) position. By raising the headrest of the gurney before liftoff, these effects can be prevented.
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