Diamedica Draw-over Vaporiser: bench testing the UK Defence Anaesthesia System in the deployed environment.

INTRODUCTION: The Diamedica Draw-over Vaporiser 2 (DDV2) is the sevoflurane vaporiser used by the UK Defence Medical Services to provide deployed volatile general anaesthesia. The Defence Anaesthesia System employs the DDV2 with a turbine-driven ventilator as a 'push-over' vaporiser, a modification from the manufacturer's design. We investigated sevoflurane delivery at varying minute volumes (MVs), vaporiser settings and temperatures in this configuration. METHODS: A range of DDV2 settings (1%, 2%, 3%, 4% and induction) and MVs (2, 4, 6 and 8 L/min at 12 ventilations per minute) were tested at two ambient temperatures (20 and 30±3°C) over 30 min. A supplemental experiment, simulating anaesthesia during damage control surgery, was also completed, where he DDV2 was set to 2% with a 6 L/min MV for 90 min. RESULTS: In both experiments, two distinct phases of sevoflurane delivery were noted, a 'wash-in phase' followed by a 'maintenance period'. The wash-in phase normally lasted less than 5 min. During the maintenance period at low MVs and vaporiser settings the DDV2 delivered a constant output, while at higher MVs and settings vapour output fell predictably. At 20±3°C, using DDV2 settings likely to be encountered in clinical practice, sevoflurane delivery was within 20% of that set. Higher vaporiser settings, MVs and temperatures resulted in greater variation between vaporiser setting and agent delivery. This variation is explained by the incomplete temperature compensation of the DDV2. CONCLUSIONS: The DDV2 functions predictably at a range of settings, MVs and temperatures. Anaesthetic delivery in the defence anaesthesia configuration is like that previously described in the draw-over configuration. The equipment was found to be reliable and robust. This experimental work supports the continued use of the Defence Anaesthesia System for the delivery of and training in deployed general anaesthesia.

Geo-temporal provision of pre-hospital emergency anaesthesia by UK Helicopter Emergency Medical Services: an observational cohort study.

BACKGROUND: Pre-hospital emergency anaesthesia (PHEA) is frequently required for injured patients. National Institute for Health and Care Excellence (NICE) quality standards state that PHEA should be delivered within 45 min of an emergency call. We investigated whether there is geo-temporal variation in service provision to the UK population. METHODS: We retrospectivly audited the time of day when PHEA is provided by UK Helicopter Emergency Medical Services (HEMS), by recording PHEA provision on a randomly selected week and weekend day in 2018. Pre-hospital emergency anaesthesia in the United Kingdom: an observational cohort study retrospectively assessed the time from emergency call to pre-hospital emergency anaesthesia delivery by HEMS during a 1 yr period from April 2017 to March 2018. The population coverage likely to receive pre-hospital emergency anaesthesia in accord with NICE guidelines was estimated by integrating population data with the median time to PHEA, hours of service provision, geographic location, and transport modality. RESULTS: On a weekday 20 HEMS units (comprising from four to 31 enhanced care teams) were estimated to be able to meet NICE guidelines for delivery of PHEA to a poulation of 6.6-35.2 million individuals (at times of minimum and maximal staffing, respectively). At the weekend, 17 HEMS units (comprising from 5 to 28 enhanced care teams) were estimated to be able to meet NICE guidelines for PHEA deliveryto a population of 6.8-34.1 million individuals (minimum and maximal staffing, respectively). CONCLUSIONS: There is marked geo-temporal variation in the ability of HEMS organisations to deliver pre-hospital emergency anaesthesia in the UK.

Pre-hospital emergency anaesthesia in the United Kingdom: an observational cohort study.

BACKGROUND: Up to one in eight trauma patients arrive at a hospital with a partially or completely obstructed airway. The UK National Institute for health and Care Excellence (NICE) practice guidelines recommend that trauma patients requiring anaesthesia for definitive airway management receive this care within 45 min of an emergency call, preferably at the incident scene. How frequently this target is achieved remains unclear. We assessed the recorded time to pre-hospital emergency anaesthesia after trauma across UK helicopter emergency medical service (HEMS) units. METHODS: We retrospectively recorded time to pre-hospital emergency anaesthesia across all 20 eligible UK HEMS units (comprising 52 enhanced care teams) from April 1, 2017 to March 31, 2018. Times recorded for emergency notification, dispatch, arrival, and neuromuscular blocking agent administration were analysed. RESULTS: HEMS undertook 1755 pre-hospital emergency anaesthetics for trauma across the UK during the study period. There were 1176/1755 (67%) episodes undertaken by helicopter response teams during daylight hours. The median time to pre-hospital emergency anaesthesia was 55 min (inter-quartile range: 45-70); anaesthesia within 45 min of the initial emergency call was achieved in 25% cases. Delayed dispatch time (>9 min) was associated with fewer patients receiving pre-hospital anaesthesia within 45 min (odds ratio: 7.7 [95% confidence intervals: 5.8-10.1]; P<0.0001). CONCLUSIONS: The time to achieve pre-hospital emergency anaesthesia by UK HEMS frequently exceeds the recommended 45 min target. Reducing the time to dispatch of emergency medical teams may impact on the delivery of pre-hospital emergency anaesthesia.

A comparison of CT lung voxel density analysis in a blast and non blast injured casualty.

INTRODUCTION: Primary blast lung injury (PBLI) is a prominent feature in casualties following exposure to blast. PBLI carries high morbidity and mortality, but remains difficult to diagnose and quantify. Radiographic diagnosis of PBLI was historically made with the aid of plain radiographs; more recently, qualitative review of CT images has assisted diagnosis. METHODS: We report a novel way of measuring post-traumatic acute lung injury using CT lung density analysis in two casualties. One casualty presented following blast exposure with confirmed blast lung injury and the other presented following extremity injury without blast exposure. Three-dimensional lung maps of each casualty were produced from their original trauma CT scan. Analysis of the lung maps allowed quantitative radiological comparison exposing areas of reduced aeration of the patient's lungs. RESULTS: 45% of the blast-exposed lungs were non-aerated compared with 10% in the non-blast-exposed lungs. DISCUSSION: In these example cases quantitative CT lung density analysis allowed blast-injured lungs to be distinguished from non-blast-exposed lungs.