Background We aimed to test if impaired oxygenation or major hemodynamic instability at the time of emergency intensive care transport between hospitals are predictors of long-term mortality.
Methods From a regional hospital intensive care transport research database, the study cohort was identified as those emergency intensive care cases transported in fixed-wing air ambulance from outlying hospitals to a regional tertiary care center during 2000–2016 for adults (16 years old or older). Impaired oxygenation was defined as oxyhemoglobin % - inspired oxygen fraction ratio (S/F ratio) < 100. Major hemodynamic instability was defined as need for treatment with noradrenaline infusion to sustain mean arterial pressure (MAP) at or above 60 mmHg or having a mean MAP < 60. All-cause mortality at 3 months after transport was the primary outcome, and secondary outcomes were all-cause mortality at 6 and 12 months. Multivariate cumulative survival and hazard analysis was performed for intervals 3, 6 and 12 months.
Results There were 2142 patients included in the analysis. The S/F ratio < 100 was associated with increased mortality risk compared to S/F > 300 at all time-points, with hazard ratio (HR) 2.9 (1.9–4.4 95% CI, p < 0.001) at 12 months. Major hemodynamic instability during ICU transport was associated with increased HR of all-cause mortality up to one year with hazard ratio 1.9 (1.5–2.5, p < 0.001).
Conclusion Major impairment of oxygenation and/or major hemodynamic instability at the time of ICU transport to get to urgent tertiary intervention is strongly associated with reduced survival at least up to one year after the transport, in this cohort. These findings support the conclusion that these conditions are markers for many fold increase in risk for death notable already at 3 months after transport for patients with these conditions. How much this risk is modifiable is not assessable in this analysis.