Temperature change in the helicopter transport of trauma patients Hypothermia at admission is an independent predictor of mortality 1 and multiple organ dysfunction. 2 Helicopter retrieval reduces the time to definitive care, 3 but providing optimal care in helicopters is difficult. Ambient air temperature decreases rapidly with altitude (20°C at sea level will drop to 10°C at altitude of 5500 feet). 4 We hypothesized that trauma patients transported by helicopter experi- enced a significant decrease in temperature during inter-hospital transfer. This is a retrospective study of adult trauma patients transferred by helicopter from level 3 and 4 hospitals to a level 1 trauma centre during the period from 1 January 2006 to 31 December 2008. The Hunter New England Human Research Ethics Committee provided an ethics waiver for the conduct of this study. The John Hunter Hospital (JHH) is the only major trauma service (level 1) in New South Wales outside Sydney. The service consists of this single level 1 trauma centre with a number of (level 3/4 equivalent) regional hospitals outside a 60 min transport time. 5 The trauma service catch- ment has a varied climate with a minimum mean inland temperature of 2.9°C and a maximum mean coastal temperature of 25.2°C. 6 The helicopter service does not currently apply any form of active or passive rewarming technique consistently during helicopter transfer. Eligible patients were identified from the helicopter service data- base. Data were retrieved from the trauma registry and the area health service’s electronic medical records. Age, gender, mechanism of injury, fluid resuscitation, injury severity score (ISS), intensive care unit (ICU) length of stay, mortality, flight time, pre-flight and post-flight temperature were collected. The primary outcome was a temperature change during the inter-hospital transfer. Secondary outcomes were mortality and ICU length of stay. Categorical independent variables were analysed using the χ 2 test. The paired Student’s t-test was used to analyse change in tempera- ture. A P-value of less than 0.05 was considered statistically signifi- cant. Pearson’s correlation was used to assess the relationship between continuous variables. Numerical data are reported as mean ± standard deviation. Hypothermia was considered at the tempera- ture of less than 36.0°C. 7 Data analysis was performed using SPSS version 19 (Chicago, IL, USA). The helicopter service transferred 745 patients over the study period. Sixty-seven of these were trauma patients. Eleven patients were excluded due to incomplete data. Fifty-six patients were iden- tified for analysis. There were more males (82%, n = 46) than females, with a mean age of 47 ± 19 years (range 17–87). The mechanism of injury was primarily blunt trauma (93%, n = 52), with 23% of these having head injury (n = 12). Patients were severely injured with a median ISS of 19 (interquartile range 16–26). Mean ICU length of stay was 5 ± 4 days (median: 4 days). Mortality was 13% (n = 7). There was no statistical difference between pre-flight (36.67° ± 0.89°C) and post-flight (36.75° ± 0.71°C) temperatures (P = 0.543) during the mean flight time of 68 ± 27 min. There was no correlation between change in temperature in-flight and flight time (r = 0.03, P = 0.82), age (r =-0.03, P = 0.82) or ISS (r = 0.18, P = 0.18). Seven patients (13%) were hypothermic on arrival at the trauma centre. The hypothermic patients experienced significant decrease in tem- perature over the duration of the flight of 0.49°C (95% CI of differ- ence: 0.07–0.90°C, P = 0.030). These patients were also colder before departure compared to patients that were normothermic on arrival (36.16°C versus 36.71°C, 95% CI of difference: 0.04°C– 1.14, P = 0.036). There were no differences found between demo- graphic, resuscitation or injury factors between the hypothermic and normothermic groups. Overall, there was no significant fall in temperature among adult trauma patients undergoing inter-hospital helicopter transport. Patients that were hypothermic on arrival to the trauma centre had experienced a significant fall in temperature over the duration of the transfer. Hypothermic patients already had significantly lower tem- peratures on departure. The challenge remains to identify this sub- group of patients before departure, to allow heat conservation and rewarming measures. Our results suggest that patients arriving at the trauma centre with body temperatures of less than 36.0°C have undergone heat loss that has been continued during helicopter transport. This loss of heat likely began at injury (reduced pre-flight temperature). The hypothermia experienced in trauma is most commonly a product of shock. 8 As a result of a decrease in peripheral perfusion, insufficient heat production occurs secondary to reduced oxygen delivery causing failure of aerobic metabolism. 8 Studies to date have reported conflicting temperature changes in trauma patients requiring helicopter transfer. Watts et al. found a reduction in temperature, 9 while Hatfield and Sookram reported no significant relationship between air transportation and temperature change. 10 Our subgroup of patients that did undergo heat loss are a cause for concern, mirroring the findings of Watts et al. 9 The known benefits of centralized trauma care will continue to increase the demand for helicopter retrieval. Our results highlight the need to assess each patient’s likelihood of hypothermia and use this as a prompt to optimize the patients’ resuscitation before and during their transfer to definitive care. §These authors contributed equally to this work. This study was presented at the 80 th Annual Scientific Congress of the Royal Australasian College of Surgeons in Adelaide, Australia on the 5 th of May, 2011. PERSPECTIVES ANZJSurg.com © 2013 The Authors ANZ Journal of Surgery © 2013 Royal Australasian College of Surgeons ANZ J Surg 83 (2013) 894–899