Best practice advice on pre-hospital emergency anaesthesia & advanced airway management

EHAC MWG statement

It is well recognised that poorly performed tracheal intubation is associated with an increased morbidity and mortality [8, 9]. Repeated attempts at laryngoscopy increase the number of complications including severe hypoxia, regurgitation and aspiration, bradycardia and cardiac arrest [10, 11]. The minimum training requirement for pre-hospital practitioners delivering drug-assisted intubation remains controversial. Individual pre-hospital emergency care services should have pre-determined criteria for the minimum training requirements and competency levels before allowing personnel to practice PHEA. There is significant variation in intubation success rates for different groups of pre-hospital care providers with different skill mix. This was confirmed in a recent meta-analysis demonstrating a median intubation success rate for physicians of 99.1% compared with 84.9% for non-physician providers. In the non-physician group, PHEA significantly increased intubation success rate [12]. Prehospital tracheal intubation performed by the correct personnel, including experienced physician anaesthetists, nurse anaesthetists, or other appropriately trained healthcare providers, is associated with high success rates and a low incidence of complications [13]. One study suggested that a minimum of 57 intubations should be performed before providers are able to reliably perform successful tracheal intubation on a consistent basis. This study showed the intubation learning curve reached 90% success rate after a mean of 57 intubations but 18% of participants still required assistance after 80 intubations [14]. Available evidence for annual competency suggests there is a significantly higher incidence of difficult intubation amongst ‘proficient’ intubators who performed a median of 18 intubations per year, compared with ‘expert’ intubators who performed a median of 304 intubations per year (p < 0.05) [15]. EHAC MWG recommends that all practitioners in pre-hospital care should achieve a minimum of 80 supervised intubations, or spend the equivalent of one-year training in anaesthesia in a hospital setting before attempting pre-hospital drug assisted intubation. Maintaining currency in a pre-hospital environment can be challenging for any procedure [16]. All pre-hospital practitioners should routinely perform tracheal intubation within their regular professional capacity to ensure maintenance of essential skills.

EHAC MWG statement

All factors influencing the success of an intubation attempt should be optimised prior to the first attempt including access to the patient, assembly of all required equipment, full monitoring and a verbalised management plan and triage decision. Whilst movement of sick or injured patients should be limited, the EHAC MWG strongly recommends that the patient should be moved to an area with adequate space to permit 360-degree access prior to intubation. Intubation should be performed outside the aircraft unless adverse events such as bad weather, low outside temperatures, or suboptimal light are considered likely to reduce the chances of a successful intubation. The patient should be placed on an ambulance trolley at an optimum height prior to any intubation attempts. The quality of laryngeal view, intubation and first pass success rates have been demonstrated to be optimal when the trolley is placed at chest height for the intubating clinician [17, 18]. Once the patient has been intubated they should be loaded onto the aircraft ensuring adequate access to the patient is maintained, with essential ‘rescue’ airway equipment easily available. The clinical condition of the patient should be reassessed each time the patient is moved to ensure the tracheal tube has not been misplaced or any deterioration has occurred requiring further intervention prior to take-off.

EHAC MWG statement

All pre-hospital systems must have all the required equipment available for each intubation attempt. The service should carry a range of laryngoscope blades and tracheal tubes in different sizes, appropriate for both adult and paediatric intubation. The tube size should be calculated prior to intubation. The use of a challenge-response equipment checklist is recommended.

Videolaryngoscopy is used in an attempt to improve laryngoscopic view and increase the overall intubation success rate and first pass intubation rate. The purpose of videolaryngoscopy is to enable all medical personnel involved to observe visualisation of the glottis and participate in improving the view where possible with interventions such as external laryngeal manipulation and suction. Data on the performance of these devices in improving intubation success rates are limited in this role. Most studies suggest videolaryngoscopes offer a benefit in pre-hospital intubation [19, 20], though certain conditions, such as blood in the airway, may impair performance [21]. Use of an intubating bougie is advocated in the management of difficult airways, usually if the view at laryngoscopy is poor or after one failed attempt at normal laryngoscopy [22, 23]. Routine use of a bougie for every intubation can also be considered good practice as it may optimize the first attempt at intubation.

EHAC MWG statement

There is increasing evidence for the benefit of both checklists and SOPs for many complex interventions. The introduction of such documents into pre-hospital practice has been shown to be feasible [24], and result in positive behavioural change to achieve the desired standardised care [25]. It is likely to be associated with a reduced rate of failed intubation [5, 26].

PHEA drugs should include an induction agent, an opioid and a rapid-onset muscle relaxant Careful consideration should be given to the type and dose of PHEA drugs, especially in unstable patients. Induction agents can also be omitted in imminent risk of cardiac arrest. Where possible the choice of agents used within individual services should be limited to improve familiarity with the PHEA process, promote the use of reproducible techniques, and reduce human error.

Passive apnoeic oxygenation with high-flow (15 l/min) oxygen via nasal prongs (or alternative methods) is a low-risk procedure. It is currently practiced by a number of pre- and in-hospital services around the world with demonstrable benefit in sustaining SaO₂ above 95% during the apnoeic phase [27] and difficult laryngoscopy [28]. Nasal prongs should be applied to the patient in the preoxygenation phase in conjunction with a standard preoxygenation technique, and remain in situ during the period of drug-induced apnoea immediately prior to intubation. One pre-hospital service demonstrated a 6% reduction in patient desaturation rates during RSI following the implementation of apnoeic oxygenation [29]. Most studies demonstrate a benefit with apnoeic oxygenation, though some do not reflect this finding. A recent randomised controlled trial using 15 L/min of 100% oxygen via nasal cannulae compared to standard face mask preoxygenation failed to show any benefit [30] and the use of apnoeic oxygenation remains controversial.

The evidence for cricoid pressure is weak and relatively scarce. The authors recommend consideration of the use of cricoid pressure for PHEA under normal circumstances but practitioners should have a low threshold for removing it if the view at laryngoscopy is impaired.

External laryngeal pressure and manipulation may be of benefit when attempting to improve the view.

EHAC MWG statement

End-tidal carbon dioxide monitoring is mandatory for all intubated patients and lack of continuous capnography is considered to be associated with an increase in morbidity and mortality [9]. Inadequate (hypo- or hyper-) ventilation can be harmful in intubated trauma patients, and is believed to contribute to an increase in mortality in this patient group, particularly in patients with traumatic brain injury [31, 32]. Although outcomes for intubated ventilated trauma patients is undoubtedly multifactorial, good control of ventilation with prevention of hypoxia and hypo- or hypercapnia is likely to be of significant benefit.

Hypothermia in sick and injured patients is widely considered to be detrimental, contributing to systemic dysfunction. One study conducted in a pre-hospital setting observed higher rates of hypothermia (< 35 °C) in patients undergoing PHEA; the mortality rate was significantly higher in this patient group [33]. The presence of hypothermia in the pre-hospital setting is usually multifactorial and related to environmental exposure for the purposes of assessment and treatment, reduced metabolic function in skeletal muscle, and administration of intravenous fluids. Clinically significant effects on plasma coagulation and platelet function are seen at temperatures below 34 °C and the mortality from traumatic haemorrhage is markedly increased when core temperatures fall below 32 °C [34].

EHAC MWG statement

Full monitoring should be attached to the patient prior to induction of anaesthesia and a summary of the information obtained from the monitoring recorded in the patient’s documentation [35]. The temperature of the patient should be closely monitored to avoid unwanted hypothermia which may exacerbate acute traumatic coagulopathy [36], or for targeted measurement for patients in whom therapeutic hypothermia is considered to be of benefit.

Summary statement

EHAC MWG recommends a standardised approach to pre-hospital emergency anaesthesia and advanced airway management described in a clear and simple Standard Operating Procedure that is followed by competent clinicians. Only personnel with sufficient experience and expertise should deliver pre-hospital advanced airway management. Standards for the pre-hospital procedure should not be inferior to those found in-hospital regarding equipment availability, patient monitoring and post-intubation care. Continuous audit of the Key Performance Indicators is essential to maintain these standards.