Pre-hospital endotracheal intubation in severe traumatic brain injury: ventilation targets and mortality-a retrospective analysis of 308 patients

Prehospital invasive arterial blood pressure monitoring in critically ill patients attended by a UK helicopter emergency medical service- a retrospective observational review of practice

BACKGROUND

Accurate haemodynamic monitoring in the prehospital setting is essential. Non-invasive blood pressure measurement is susceptible to vibration and motion artefact, especially at extremes of hypotension and hypertension: invasive arterial blood pressure (IABP) monitoring is a potential solution. This study describes the largest series to date of cases of IABP monitoring being initiated prehospital.

METHODS

This retrospective observational study was conducted at East Anglian Air Ambulance (EAAA), a UK helicopter emergency medical service (HEMS). It included all patients attended by EAAA who underwent arterial catheterisation and initiation of IABP monitoring between 1st February 2015 and 20th April 2023. The following data were retrieved for all patients: sex; age; aetiology (medical cardiac arrest, other medical emergency, trauma); site of arterial cannulation; operator role (doctor/paramedic); time of insertion and, where applicable, times of pre-hospital emergency anaesthesia, and return of spontaneous circulation following cardiac arrest. Descriptive analyses were performed to characterise the sample.

RESULTS

13,556 patients were attended: IABP monitoring was initiated in 1083 (8.0%) cases, with a median age 59 years, of which 70.8% were male. 546 cases were of medical cardiac arrest: in 22.4% of these IABP monitoring was initiated during cardiopulmonary resuscitation. 322 were trauma cases, and the remaining 215 were medical emergencies. The patients were critically unwell: 981 required intubation, of which 789 underwent prehospital emergency anaesthesia; 609 received vasoactive medication. In 424 cases IABP monitoring was instituted en route to hospital.

CONCLUSION

This study describes over 1000 cases of prehospital arterial catheterisation and IABP monitoring in a UK HEMS system and has demonstrated feasibility at scale. The high-fidelity of invasive arterial blood pressure monitoring with the additional benefit of arterial blood gas analysis presents an attractive translation of in-hospital critical care to the prehospital setting.

Agreement between arterial and end-tidal carbon dioxide in adult patients admitted with serious traumatic brain injury

BACKGROUND

Low-normal levels of arterial carbon dioxide (PaCO2) are recommended in the acute phase of traumatic brain injury (TBI) to optimize oxygen and CO2 tension, and to maintain cerebral perfusion. End-tidal CO2 (ETCO2) may be used as a surrogate for PaCO2 when arterial sampling is less readily available. ETCO2 may not be an adequate proxy to guide ventilation and the effects on concomitant injury, time, and the impact of ventilatory strategies on the PaCO2-ETCO2 gradient are not well understood. The primary objective of this study was to describe the correlation and agreement between PaCO2 and ETCO2 in intubated adult trauma patients with TBI.

METHODS

This study was a retrospective analysis of prospectively-collected data of intubated adult major trauma patients with serious TBI, admitted to the East of England regional major trauma centre; 2015-2019. Linear regression and Welch's test were performed on each cohort to assess correlation between paired PaCO2 and ETCO2 at 24-hour epochs for 120 hours after admission. Bland-Altman plots were constructed at 24-hour epochs to assess the PaCO2-ETCO2 agreement.

RESULTS

695 patients were included, with 3812 paired PaCO2 and ETCO2 data points. The median PaCO2-ETCO2 gradient on admission was 0.8 [0.4-1.4] kPa, Bland Altman Bias of 0.96, upper (+2.93) and lower (-1.00), and correlation R2 0.149. The gradient was significantly greater in patients with TBI plus concomitant injury, compared to those with isolated TBI (0.9 [0.4-1.5] kPa vs. 0.7 [0.3-1.1] kPa, p<0.05). Across all groups the gradient reduced over time. Patients who died within 30 days had a larger gradient on admission compared to those who survived; 1.2 [0.7-1.9] kPa and 0.7 [0.3-1.2] kPa, p<0.005.

CONCLUSIONS

Amongst adult patients with TBI, the PaCO2-ETCO2 gradient was greater than previously reported values, particularly early in the patient journey, and when associated with concomitant chest injury. An increased PaCO2-ETCO2 gradient on admission was associated with increased mortality.