Military Forward Aeromedical Evacuation and civilian Helicopter Emergency Medical Services are widely used to conduct Primary Aeromedical Retrieval. Crew composition in Primary Aeromedical Retrieval missions varies considerably. The ideal composition is unknown. Thus, we conducted a descriptive systematic review on mortality and other outcomes for different Primary Aeromedical Retrieval crew compositions.

Medline, Embase, and Cochrane Controlled Trials Register were searched up to January 2020. Results were reported per Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Studies of adult trauma air transported by different crews were included. Population, injury severity, crew composition, procedures, and outcomes, including mortality, were abstracted. Risk of bias was assessed using previously validated tools. A lack of reported effect measures precluded a quantitative analysis.

Sixteen studies met inclusion criteria (3 prospective studies, 1 case-control, and 12 retrospective). Overall, studies reported a mortality benefit associated with advanced health care providers. This was most apparent in patients with severe but survivable injuries. In this population, early rapid sequence induction, endotracheal intubation, mechanical ventilation, thoracostomies, blood products transfusion, and treatment of hemorrhagic shock are better performed by advanced providers and may improve outcomes. The quality of evidence reported a moderate risk of bias in the included studies.

Overall, findings were divergent but showed a trend to decreased mortality in patients treated by advanced providers with interventions beyond the basic paramedic level. This trend was most significant in patients with severe but survivable injuries. These results should be cautiously interpreted because most studies were observational, had small sample sizes, and had a high potential for confounding factors.

Prehospital ultrasound (PHUS) assessments by physicians and non-physicians are performed on medical and trauma patients with increasing frequency. Prehospital ultrasound has been shown to be of benefit by supporting interventions.

Which patients may benefit from PHUS has not been clearly identified.

A multi-variable logistic regression analysis was performed on a previously created retrospective dataset of five years of physician- and non-physician-performed ultrasound scans in a Canadian critical care Helicopter Emergency Medical Service (HEMS). For separate medical and trauma patient groups, the a-priori outcome assessed was patient characteristics associated with the outcome variable of “PHUS-supported intervention.”

Both models were assessed (Likelihood Ratio, Score, and Wald) as a good fit. For medical patients, the characteristics of heart rate (HR) and shock index (SI) were found to be most significant for an intervention being supported by PHUS. An extremely low HR was found to be the most significant (OR=15.86 [95% confidence interval (CI), 1.46-171.73]; P=.02). The higher the SI, the more likely that an intervention was supported by PHUS (SI 0.9 to<1.3: OR=9.15 [95% CI, 1.36-61.69]; P=.02; and SI 1.3+: OR=8.37 [95% CI, 0.69-101.66]; P=.09). For trauma patients, the characteristics of Prehospital Index (PHI) and SI were found to be most significant for PHUS support. The greatest effect was PHI, where increasing ORs were seen with increasing PHI (PHI 14-19: OR=13.36 [95% CI, 1.92-92.81]; P=.008; and PHI 20-24: OR=53.10 [95% CI, 4.83-583.86]; P=.001). Shock index was found to be similar, though, with lower impact and significance (SI 0.9 to<1.3: OR=9.11 [95% CI, 1.31-63.32]; P=.025; and SI 1.3+: OR=35.75 [95% CI, 2.51-509.81]; P=.008).

In a critical care HEMS, markers of higher patient acuity in both medical and trauma patients were associated with occurrences when an intervention was supported by PHUS. Prospective study with in-hospital follow-up is required to confirm these hypothesis-generating results.

O’DochartaighD, DoumaM, AlexiuC, RyanS, MacKenzieM. Utilization Criteria for Prehospital Ultrasound in a Canadian Critical Care Helicopter Emergency Medical Service: Determining Who Might Benefit. Prehosp Disaster Med. 2017;32(5):536–540.

Non-invasive positive pressure ventilation (NIPPV) is used to treat severe acute respiratory distress. Prehospital NIPPV has been associated with a reduction in both in-hospital mortality and the need for invasive ventilation.

The authors of this study examined factors associated with NIPPV failure and evaluated the impact of NIPPV on scene times in a critical care helicopter Emergency Medical Service (HEMS). Non-invasive positive pressure ventilation failure was defined as the need for airway intervention or alternative means of ventilatory support.

A retrospective chart review of consecutive patients where NIPPV was completed in a critical care HEMS was conducted. Factors associated with NIPPV failure in univariate analyses and from published literature were included in a multivariable, logistic regression model.

From a total of 44 patients, NIPPV failed in 14 (32%); a Glasgow Coma Scale (GCS) <15 at HEMS arrival was associated independently with NIPPV failure (adjusted odds ratio 13.9; 95% CI, 2.4-80.3; P=.003). Mean scene times were significantly longer in patients who failed NIPPV when compared with patients in whom NIPPV was successful (95 minutes vs 51 minutes; 39.4 minutes longer; 95% CI, 16.2-62.5; P=.001).

Patients with a decreased level of consciousness were more likely to fail NIPPV. Furthermore, patients who failed NIPPV had significantly longer scene times. The benefits of NIPPV should be balanced against risks of long scene times by HEMS providers. Knowing risk factors of NIPPV failure could assist HEMS providers to make the safest decision for patients on whether to initiate NIPPV or proceed directly to endotracheal intubation prior to transport.

LeeJS , O’DochartaighD , MacKenzieM , HudsonD , CouperthwaiteS , Villa-RoelC , RoweBH . Factors Associated with Failure of Non-invasive Positive Pressure Ventilation in a Critical Care Helicopter Emergency Medical Service. Prehosp Disaster Med2015; 30(2): 1–5