Introduction The most appropriate advanced airway intervention in out-of-hospital cardiac arrest (OHCA) is unproven. This study reviews prehospital advanced airway management and its complications in OHCA patients.
Methods A 4-year, observational, retrospective case review. Patients attending the Emergency Department of the Royal Infirmary of Edinburgh, Scotland, with a primary diagnosis of OHCA were identified. Patient demographics, survival to admission, airway management technique and complication rates were identified.
Results Seven hundred and ninety-four cases were identified. The aetiology of cardiac arrest was medical in 95.2%, traumatic in 3.9% and unrecorded in 0.9%. Prehospital intubation was attempted in 628 patients. Prehospital intubation was successful in 573 patients. A significant complication (multiple attempts, displaced endotracheal tube or oesophageal intubation) occurred in 55 (8.8%) patients. 165 (20.8%) patients survived to hospital admission, of whom 110 had undergone prehospital intubation. 55 patients who did not undergo prehospital tracheal intubation survived to hospital admission.
Conclusion The optimal method of maintaining an airway and ventilating an OHCA patient has yet to be established. Prehospital tracheal intubation for OHCA is associated with significant complications and may reduce survival. The use of tracheal intubation as a routine intervention should be reconsidered. Ambulance services should consider adopting alternative strategies in airway management.
- Emergency ambulance systems
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Out-of-hospital cardiac arrest (OHCA) is a major cause of mortality and morbidity in the UK1, and 7.5% of Intensive Care admissions are due to OHCA.2 The introduction of paramedics by the ambulance service aimed to bring advanced life support to the patient including tracheal intubation. Paramedic intubation in the UK is usually limited to patients who do not require drug-assisted intubation—the majority of these have had an OHCA.
The most appropriate advanced airway intervention in OHCA is unknown. Tracheal intubation without anaesthetic drugs for OHCA is not associated with increased survival rates;3 yet currently tracheal intubation is a core skill on the paramedic syllabus.
There is a significant complication rate associated with prehospital tracheal intubation by paramedics,4 and other airway strategies have been suggested. Supraglottic airway devices are well established in anaesthetic practice and have been used successfully in OHCA patients.5 Supraglottic airways have recently been recommended by the Joint Royal College Ambulance Liaison Committee (JRCALC).
The objectives of this study are to review prehospital advanced airway management and its complications in patients following OHCA.
The Emergency Department (ED) of the Royal Infirmary of Edinburgh (RIE) is located in an urban setting and has approximately 120 000 attendances annually. Patients attending the ED between 1 August 2002 and 11 August 2006 with a primary diagnosis of OHCA were studied. Patients were identified by hand-searching the resuscitation room logbook and the ED electronic medical record.
The RIE ED intubation registry was also scrutinised to identify any patients who required reintubation or other airway interventions on arrival at the ED.
Data collected included age, sex, indication for intubation and complications (including unrecognised oesophageal intubation, endobronchial intubation, displacement of tube en route, failed prehospital intubation or need for reintubation in the ED). Survival to hospital admission from the ED was noted.
Seven hundred and ninety-four patients were identified. The mean patient age was 65 years. Seventy-three per cent were male. The aetiology of OHCA was identified as medical in 756 (95.2%) patients, trauma in 31 (3.9%) and unknown in seven (0.9%) patients. One hundred and sixty-five (20.8%) patients survived to hospital admission from the ED.
Prehospital tracheal intubation was attempted in 628 (79%) patients. Successful endotracheal intubation was achieved in three or fewer attempts in 573 (91.2%) of these patients. In 55 patients, tracheal intubation was associated with a significant problem (table 1). In 32 patients, prehospital tracheal intubation was abandoned after multiple attempts. In three patients, tracheal tubes were displaced on arrival at the ED. In three patients, bronchial intubation had been performed. In two patients, the tracheal tube cuff was situated above the vocal cords.
In 15 patients, unrecognised prehospital oesophageal intubation occurred. The aetiology of cardiac arrest in these cases was medical in 11 patients and trauma in four patients. All patients with traumatic OHCA aetiology died. Four of the 11 patients with medical OHCA aetiology survived to hospital admission from the ED.
Five hundred and seventy-four (91.4%) intubated patients arriving at the ED had documented verification of tracheal tube position in the ED notes. Table 2 demonstrates the techniques used to verify tracheal tube position.
One hundred and ten of 628 patients who underwent prehospital tracheal intubation survived to hospital admission from the ED. Fifty-five patients who did not undergo prehospital tracheal intubation survived to hospital admission. Survival to admission was higher in patients who did not have prehospital intubation performed (33.1 vs 17.5%, p<0.0001). The LMA was not used on any patients.
The management of OHCA is challenging. Tracheal intubation is frequently quoted as the ‘gold standard’ of airway management. Paramedics perform intubation presuming that this represents the most effective method of prehospital airway management in OHCA. Patients in cardiac arrest require adequate oxygenation which can be achieved by basic airway management. At-scene intubation has been shown to increase on-scene time, delaying patients' transfer to definitive care.6 7 Advanced airway skills utilised by paramedics confer no increased survival compared with patients attended by ambulance technicians with basic airway skills.7 8
In this study, tracheal intubation was attempted in 79% of OHCA patients and was successful in three or less attempts in 91.2% of these.
Fifty-five tracheal intubation attempts were associated with complications. This rate is similar to that of previous studies.6 Thirty-two patients had multiple attempts at tracheal intubation, and subsequent attempts were abandoned. All but one of the failed prehospital intubations were successfully intubated by medical staff in the ED. Repeated attempts at laryngoscopy or inability to intubate the trachea compromises oxygenation and ventilation, extends on-scene times and increases the risk of aspiration. Intubating patients post-traumatic OHCA may be challenging due to airway trauma and the need for cervical spine immobilisation.
Of concern are the 15 patients who were subjected to unrecognised oesophageal intubation. Only 91.4% of patients had documented confirmation of tracheal tube position on arrival at the ED. Given the demonstrated complications of prehospital endotracheal intubation, it is essential to undertake and document this. Most clinicians rely on a combination of direct vision and auscultation to confirm tracheal tube position. Capnography is the most reliable method of confirming tracheal tube placement in the prehospital setting9 10 but requires a specific electronic monitor. A number of simple devices are available to confirm tracheal placement including the Ambucheck device and colorimetry. Scottish Ambulance Service ambulances are not equipped with any such device. In patients in cardiac arrest, the delivery of carbon dioxide in the pulmonary circulation can be variable.11 Capnography can therefore be unreliable in confirming tube position in these patients and should therefore be used in conjunction with other confirmatory techniques.
In this study, prehospital tracheal intubation was associated with decreased rates of survival to admission. The reasons for this are likely to be multifactorial. Tracheal intubation may distract from providing good-quality basic life support, defibrillation and delay on scene times. Tracheal intubation and ventilation with oxygen will result in an inspired oxygen concentration of close to 100%. Ventilating cardiac arrest patients with 100% oxygen may increase oxidative stress and reactive oxygen species production, which can contribute to neuronal cell death.12
Tracheal intubation requires extensive training and retraining to avoid skill decay. Widespread utilisation of supraglottic airway devices and regional anaesthesia has reduced the opportunities for training in tracheal intubation. Currently, Scottish ambulance paramedics are required to insert up to 20 tracheal tubes during a 2-week in-hospital training module. Thereafter, they are likely to encounter fewer than five OHCA per year and do not undertake further in-hospital advanced airway training. Significant rates of serious complications are demonstrated, and these may be higher in practitioners using the technique infrequently.
A number of studies have examined the use of the Laryngeal Mask Airway (LMA) in OHCA.13 14 The LMA has a number of potential benefits: the need for relatively little training or ongoing competency requirements, ease of insertion and less risk of incorrect placement. Using an LMA in OHCA has few complications and has not been shown to impact negatively on survival when compared with basic airway management.14 15 The 2008 JRCALC guidelines16 include a recommendation that the use of supraglottic airway devices should be considered by ambulance crews.
The optimal method of maintaining an airway and ventilating an OHCA patient has yet to be established. Prehospital tracheal intubation for OHCA is associated with significant complications and may reduce survival. The use of tracheal intubation as a routine intervention should be reconsidered. Ambulance services should consider adopting alternative strategies in airway management.
The authors thank the Scottish Trauma Audit Group for facilitating access to the Emergency Department Intubation Registry and assistance with data searching.
Competing interests None.
Provenance and peer review Not commissioned; not externally peer reviewed.
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