Factors influencing patient thermomgulation in flight

Introduction: Endogenous control of core temperature (CT) is taxed during serious illness or injury. Temperature extremes increase morbidity and mortality. This prospective study sought to identify risk factors associated with decreases in patient CT during rotor-wing (RW) transport. Setting: The study was conducted at a Midwestern, hospital-based RW flight program completing more than 1,200 missions annually. Two BK-117 helicopters staffed by flight nurse/flight physician and flight nurse/flight paramedic configurations were used. Methods: Rectal temperature probes were secured. Patient, cabin and ambient temperatures were recorded on liftoff (LO), at 15-minute intervals after LO, and on landing. Also recorded were Glasgow Coma Score (GCS), Revised Trauma Score (RTS) when applicable, transport time, time subjects were uncovered, total intravenous (IV) fluid and blood infused, use of neuromuscular blockade (NMB), exposure to moisture, and any warming aids used during flight. Results: Of 75 patients, 66 had temperature changes (ΔT). Five (6.7%) had clinically significant (ΔT ≥0.5 °C) transport changes, the greatest ΔT = −1.2 °C. Fifteen (20%) were hypothermic (<35 °C) on LO. Nine of these had further −ΔT in flight, four with −ΔT ≥0.5 °C. No patient who was not initially hypothermic dropped below 35 °C. Spearman rank correlation indicated that initial hypothermia (p = 0.006), time uncovered (p = 0.02) and NMB (p = 0.05) were significantly correlated with −ΔT. Wilcoxon rank-sum tests revealed patients with temperatures ≤35 °C had significantly lower GCS (p = 0.006) and RTS (p = 0.04). Warming aids were not significantly correlated with +ΔT. Conclusions: Factors associated with −ΔT in flight include initial hypothermia, NMB and exposure. Clinically significant −ΔT in this setting are rare and are associated with initially hypothermic patients. Patients with accidental hypothermia tend to have lower GCSs and RTSs. Nonhypothermic patients do not develop hypothermia during RW transport of relatively short duration when standard measures to prevent heat loss are employed.