Nonfreezing cold injuries among long-distance polar rowers

IntroductionNonfreezing cold injury (NFCI) is a peripheral cold injury that occurs when the extremities are exposed to cold temperatures, at or near the freezing point, for sustained periods of time (48–96 h at temperatures of usually around 0 to 6°C with associated wind chill). Although NFCI often goes unreported and may be underdiagnosed, it is a cause of significant morbidity in those working in cold conditions, particularly those in the military. Thus, further research into the prevention, recognition, and treatment of NFCI is warranted.MethodsThe height, body weight, and body composition of 6 rowers taking part in 1 or 2 legs of the 2017 Polar Row expedition were measured. The weather conditions of the 2 legs of the journey were recorded, and symptoms relating to NFCI were documented.ResultsAll incidences of NFCI occurred during Leg 2 of the expedition, which was colder and wetter. Of the Leg 2 rowers, those who developed NFCI had a trend toward higher pre-row body weight and body mass index and a trends toward losing more weight and body water relative to those who did not.ConclusionsThe main factor contributing to the incidence of NFCI appeared to be weather; NFCI only occurred during the colder and wetter leg of the expedition. We also tentatively suggest that nutrition and dehydration may be linked to the incidence of NFCI as predisposing factors. More work, with sample sizes greater than those reported here, is required to investigate these associations to further characterize risk factors.</div

Cerebral artery dilatation maintains cerebral oxygenation at extreme altitude and in acute hypoxia : an ultrasound and MRI study

Transcranial Doppler is a widely used noninvasive technique for assessing cerebral artery blood flow. All previous high altitude studies assessing cerebral blood flow (CBF) in the field that have used Doppler to measure arterial blood velocity have assumed vessel diameter to not alter. Here, we report two studies that demonstrate this is not the case. First, we report the highest recorded study of CBF (7,950 m on Everest) and demonstrate that above 5,300 m, middle cerebral artery (MCA) diameter increases (n=24 at 5,300 m, 14 at 6,400 m, and 5 at 7,950 m). Mean MCA diameter at sea level was 5.30 mm, at 5,300 m was 5.23 mm, at 6,400 m was 6.66 mm, and at 7,950 m was 9.34 mm (P<0.001 for change between 5,300 and 7,950 m). The dilatation at 7,950 m reversed with oxygen. Second, we confirm this dilatation by demonstrating the same effect (and correlating it with ultrasound) during hypoxia (FiO2=12% for 3 hours) in a 3-T magnetic resonance imaging study at sea level (n=7). From these results, we conclude that it cannot be assumed that cerebral artery diameter is constant, especially during alterations of inspired oxygen partial pressure, and that transcranial 2D ultrasound is a technique that can be used at the bedside or in the remote setting to assess MCA caliber

Are some strokes preventable? The potential role of transcranial doppler in transient ischaemic attacks of carotid origin

Transient ischaemic attacks (TIA) are more than just ministrokes. The high frequency of early stroke following TIA has resulted in the recent publication of guidelines in the UK. The guidelines recommend that patients attend a neurovascular clinic within 7 days of the index event to expedite investigation and treatment and so reduce the risk of a subsequent (potentially more serious) neurological event. After a TIA or stroke caused by carotid-artery disease, there is an increase in cerebral microemboli detectable by transcranial doppler (TCD). High microembolic loads appear to be surrogate markers for future neurological events, and the pharmacological efficacy of therapeutic interventions can now be rapidly and non-invasively assessed in the clinic or at the bedside. Medical treatments can now be optimised, avoiding the need for urgent or emergency carotid surgery and therefore allowing patients to undergo safer elective surgery when appropriate