14. Airway Management of Patients with Life Threatening Haemorrhage: Principles of Safe and Effective Care
KeywordsRapid sequence intubationIntubationAirwayVentilationPositive pressure ventilationExtraglottic airway deviceCricothyrotomy
Backwards upwards rightwards pressure
Extraglottic airway device
External laryngeal manipulation
Emergency medical services
End-tidal carbon dioxide
Helicopter emergency medical services
Laryngeal mask airway
Manual in line stabilisation
Medical treatment facility
Neuromuscular blocking agent
Pharmacologically assisted laryngeal mask
Rapid sequence intubation
Traumatic brain injury
Tactical combat casualty care
Tactical emergency casualty care
Airway care of the patient with life threatening haemorrhage has two fundamental objectives: to prevent respiratory insufficiency (hypoxaemia or hypercarbia ) and to facilitate damage control resuscitation interventions. Immediate care must ensure a patent airway, protection of the airway and lungs from contamination and when necessary, assistance with ventilation. This must be achieved from the onset of haemorrhage and may require a range of interventions from basic airway manoeuvres to advanced airway procedures. Subsequently, there may be a requirement to deliver general anaesthesia to permit invasive haemorrhage control procedures. In this chapter, we discuss the range of techniques to manage both phases of airway care safely and effectively in the presence of life threatening haemorrhage.
Airway Care in the Remote Damage Control Resuscitation (RDCR) Setting
Many of the studies of preventable deaths from trauma that highlight the importance of haemorrhage control also demonstrate that airway obstruction is a significant cause of preventable death in the pre-hospital setting [1, 2]. One extensive review of military battlefield trauma deaths concluded that airway obstruction represented the second most common category of death due to potentially survivable injury that occurred prior to arrival at a medical treatment facility (MTF) . It is therefore imperative that providers of care in the pre-hospital environment have the necessary skills to recognise and manage airway compromise in the presence of life threatening haemorrhage.
For many patients with life threatening haemorrhage, damage control resuscitation will start in the pre-hospital environment (remote damage control resuscitation). This environment may be an urban setting with short transport times to sophisticated medical facilities. In many parts of the world, however, pre-hospital care is delivered in remote, austere and sometimes dangerous environments. There are many challenges associated with delivering remote damage control resuscitation, including safe and effective airway care, in such settings. There may be a lack of monitoring, equipment, communications, transport and medical supplies. Extended evacuation times may necessitate that providers undertake not only the time-critical, life-saving, airway interventions but also provide ongoing protection of the airway en-route to appropriate medical facilities.
Who Provides Care?
Initial airway care of the patient with life threatening haemorrhage is not the exclusive domain of any given medical provider but will fall to whoever has the necessary skills to recognise and manage airway compromise. In some health care systems, particularly civilian Emergency Medical Services (EMS) and Helicopter Emergency Services (HEMS), a small cadre of highly trained paramedical or medical staff can be deployed to supplement the basic airway skills of other providers on the few occasions when more sophisticated interventions are required. In more hostile, military environments, this may not be feasible and so basic healthcare providers may need to have a wider range of airway skills appropriate to the casualties they may encounter. Military initiatives such as the Tactical Combat Casualty Care (TCCC) training program and the Civilian Tactical Emergency Casualty Care (C-TECC) program seek to address these problems and emphasise the time-critical nature of not only haemorrhage control measures but also airway interventions. Such courses and an investment in the overall doctrine necessary to deliver these skills have been shown to have a significant impact upon outcomes from trauma. One study of military trauma outcomes following the introduction of a TCCC program demonstrated a dramatic reduction of preventable deaths on the battlefield .
Airway Care in Life Threatening Haemorrhage
Principles of Safe and Effective Airway Care
Indications for Intervention
Many patients with life threatening haemorrhage need no immediate airway intervention, either in the pre-hospital setting or upon arrival at a medical treatment facility. Whilst basic airway skills can be delivered by providers with relatively limited training and experience, there are some patients who will need more sophisticated interventions. The proportion of patients requiring these advanced interventions varies by population studied. One review of 6875 combat casualties arriving at Combat Support Hospitals during Operation Iraqi Freedom found that 4.8% had undergone advanced airway interventions, delivered by a variety of providers, in the pre-hospital phase . In another study of pre-hospital airway interventions in UK civilian practice, a significant proportion (57%) of trauma patients who had undergone initial airway intervention by EMS personnel still had airway compromise (partial airway obstruction or evidence of airway contamination) on arrival of an advanced care team and required advanced airway interventions . Thus, providers of airway care in the pre-hospital environment must be trained not only in basic airway skills but also recognition of when more advanced interventions are required. Consideration needs to be given of which advanced airway skills and equipment will then be used and which providers will be required to deliver them.
Airway Assessment and Basic Care
All patients with haemorrhagic shock are at risk of developing airway compromise and therefore require rapid initial assessment and ongoing observation for impending airway compromise. The starting point of all airway care are the traditional methods of visual inspection of the airway and associated ventilatory efforts, listening for typical noises of airway obstruction and when necessary feeling for the movement of air. These methods may be more time consuming and inaccurate than generally realised, particularly in austere or hostile environments . Monitoring with continuous wave-form capnography will help assess the net results of airway patency and ventilatory effort and is essential if advanced airway interventions are subsequently performed . Pulse oximetry will provide information about oxygenation and circulation of blood although is often unreliable in the low flow states found in life threatening haemorrhage. Providers should avoid overreliance upon such adjunctive monitoring and be prepared to make repeated clinical assessments of airway patency, ventilatory effort and mentation. A stepwise approach to airway care should be used to ensure that simple strategies are the starting point after which an escalation of intervention can be employed to achieve a patent airway. Positioning of patients plays a vital role in initial airway care. In many settings, providers will want to position the patient in the supine position to facilitate airway care, interventions to address life threatening haemorrhage and casualty transport, but for many patients this represents a suboptimal position. Patients with life threatening obstetric haemorrhage may suffer aorto-caval obstruction when placed in the supine position and so should be managed in a tilted position. Patients with life threatening haemoptysis or haematemesis may aspirate blood if placed in the supine position. Similarly, patients with soiling of the airway or inability to maintain an airway in a supine position may be best managed in the lateral position to allow gravity to assist with postural drainage and opening of the airway. Many providers are naturally concerned about the potential risk of the lateral position for patients with suspected spinal injury, but a systematic review identified no evidence to suggest that placing patients with spinal injury into a lateral position carries a risk of neurological deterioration provided appropriate precautions are taken . Simple airway opening manoeuvres such as jaw thrust, chin lift or head tilt may be required in the presence of airway obstruction but only jaw thrust is suitable for trauma patients with suspected cervical spine injury. Numerous studies have shown that cervical spine injury is rare in the presence of penetrating neck injury or gunshot wounds to the head and that in such settings airway management should take priority over cervical spine immobilisation [11, 12].
In some patients, a patent airway can only be maintained by the use of simple airway adjuncts, either a nasopharyngeal (NPA ) or an oropharyngeal airway (OPA) . Nasopharyngeal airways have the advantage of being relatively easy to insert, are better tolerated in patients who are not completely obtunded (hence less likely to cause gagging or vomiting) and can be inserted when a patient has trismus. Conversely, there is some evidence that incorrectly sized NPAs are ineffective or can actually precipitate airway obstruction . Furthermore, there are case reports of intracranial passage of NPAs in patients with associated major head injury and of significant epistaxis with incautious insertion of the device [14, 15]. The relatively low risks of insertion must be balanced with the perceived benefits in each setting. OPAs are widely used as airway adjuncts but are usually only tolerated by deeply unconscious patients. In the event that these basic strategies fail then providers will need to escalate to more invasive methods of airway care.
Advanced Airway Care
Surgical Airways and Extraglottic Airway Devices (EADs)
Airway care in remote or austere settings often falls to relatively inexperienced providers with limited training or equipment and hence strategies to manage airway problems must take their level of training and experience into account. For this reason, many military organisations have chosen to train their pre-hospital medical providers in the skills required to perform surgical airway insertion (cricothyrotomy) when there are direct airway injuries or providers are unable to perform alternative advanced techniques such as the use of extraglottic airway devices (EAD) or drug-assisted endotracheal tube placement. There are many advantages of cricothyrotomy as an advanced airway intervention in an RDCR setting. It is a relatively easily learned and remembered technique that in its simplest form requires little equipment or post-procedural care . There are a variety of techniques from simple dissection and insertion of a cuffed tracheal tube (“scalpel, finger, bougie”) to Seldinger devices and techniques that require more equipment and training. There would currently appear to be no clear advantages of any given technique or equipment . Military studies have shown success rates of up to 93% [18–20]. A potentially compelling advantage is that this procedure can also be performed under local anaesthetic or with appropriate sedation (using agents least likely to cause hypotension or respiratory depression). When an airway has been secured, patients can be allowed to breathe spontaneously as muscle paralysis is not required to facilitate this procedure. There are clear haemodynamic benefits of spontaneous negative pressure ventilation over positive pressure ventilation for patients with life threatening haemorrhage. Cricothyrotomy is less widely used in civilian pre-hospital care settings due to lower rates of ballistic facial injury, concerns about potential harm of the procedure, increasing use of extraglottic airway devices and wider availability of drug- assisted intubation skills.
Another advanced strategy of airway care is the use of an extraglottic airway device (EAD) . Such devices are relatively easy to use and can be rapidly inserted with little risk of harm in deeply unconscious patients. They can be used for either spontaneous or assisted ventilation. They may require little or no ancillary equipment , particularly when a version is used that does not require cuff inflation after insertion. Although they all feature some sort of cuff or seal to limit the risk of aspiration of gastric contents or airway contaminants, they cannot be considered to offer a secure airway. Furthermore, to allow insertion, patients must either be deeply unconscious or drugs must be administered to obtund airway reflexes otherwise vomiting may occur. This can make them complex to employ in patients with dynamic airway compromise. Some providers suggest the use of pharmacologically assisted laryngeal mask (PALM) placement although this does expose the patient to all the risks of sedation or even paralysis without the advantages of achieving a secure, cuffed endotracheal tube . The safety and efficacy of this technique remain unclear. There is no doubt, however, that as rapidly inserted airway interventions for unconscious patients or as “rescue” devices in the case of failed endotracheal intubation, EADs have a role to play in the advanced airway care of patients with life threatening haemorrhage .
Endotracheal Intubation and Positive Pressure Ventilation
When Should Patients with Life Threatening Haemorrhage Be Intubated?
Patients with life threatening haemorrhage who are unable to be oxygenated by use of any of the basic airway manoeuvres or adjuncts described above, or whose airway cannot be protected from contamination of blood, debris or gastric contents will need placement of an endotracheal tube to maintain oxygenation. This is usually facilitated by a process of drug-assisted sedation and paralysis to achieve rapid sequence intubation (RSI) . Paralysed patients must then be ventilated by positive pressure ventilation. In the presence of haemorrhagic shock, any induction agent can exacerbate the hypotensive state and positive pressure ventilation will further reduce cardiac output. Given these risks, controversy exists about the efficacy of pre-hospital intubation, with some retrospective studies seeming to show that it confers no survival advantage whilst other prospective studies have suggested improved outcomes [23–25]. Furthermore, some studies have even suggested that a strategy of rapid transport to hospital by police or private transport rather than Emergency Medical Services is associated with lower mortality for trauma patients, perhaps highlighting the time-critical need to achieve haemorrhage control as the greatest priority [26, 27]. On arrival at a medical treatment facility, patients who have not already been intubated are likely to need rapid sequence intubation to allow invasive haemorrhage control procedures as part of a coordinated damage control resuscitation strategy. The significant risk of haemodynamic compromise of this procedure should be mitigated whenever possible by a policy of aggressive blood product resuscitation in the peri-intubation phase.
Indications for endotracheal intubation in RDCR
Failure to achieve oxygenation or ventilation by other techniques
Inability to protect airway
To perform damage control surgery/invasive haemorrhage control procedures
Impending airway obstruction, e.g. burns
To facilitate transfer
Combative head injury patients
Humanitarian – distressing multiple injuries
When Should Patients with Life Threatening Haemorrhage Not Be Intubated?
Life threatening haemorrhage is not in itself an indication for intubation and positive pressure ventilation despite the perception that this brings order to a sometimes chaotic and challenging situation. When undertaken in awake hypotensive trauma patients in the field, pre-hospital intubation and positive pressure ventilation have been shown to be associated with increased in-hospital mortality . Whilst many such patients will eventually require intubation to facilitate haemorrhage control procedures, this should be deferred, whenever safely possible, until the patient can be adequately resuscitated. Providers of airway care, particularly in remote settings where blood products may be less widely available, must therefore be trained in a range of appropriate airway strategies to manage the airway without resorting to intubation. Reduced level of consciousness due to life threatening haemorrhage should also not in itself mandate intubation in the pre-hospital setting as this does not necessarily correlate with ability to maintain an airway. If adequate oxygenation can be maintained and the airway protected from contamination using appropriate measures (e.g. postural drainage or suction) in a patient who is self-ventilating, then consideration should be given to transporting the patient to an appropriate medical treatment facility as rapidly as possible without performing intubation. When advanced airway practitioners are deployed into the pre-hospital environment, it must be recognised that they possess the vital skills and experience not only to perform intubation but also to identify when patients with life threatening haemorrhage can safely be managed without intubation. Providers must weigh the potential benefits of intubation and positive pressure ventilation against the significant risks of these procedures, particularly critical organ hypo-perfusion and cardiac arrest, in the presence of life threatening haemorrhage and consider whether alternative, lower risk, airway management strategies (including EAD placement or cricothyrotomy) can be employed pending the availability of more definitive resuscitation facilities.
Rapid Sequence Intubation in the Presence of Life Threatening Haemorrhage
If intubation must be performed in the presence of life threatening haemorrhage, there are specific considerations that minimise risk and optimise outcomes:
Blood Product Resuscitation
Given the hypotensive effects of induction agents and reduction of cardiac output caused by positive pressure ventilation, it is vital that patients with life threatening haemorrhage are resuscitated by blood product administration, whenever possible, prior to intubation and ventilation. If blood products cannot be made available, then crystalloid or colloids should be used to improve preload prior to intubation.
Patients with haemorrhagic shock will rapidly desaturate during the intubation process unless appropriate measures are taken to maximise pre-oxygenation and minimise the duration of apnoea. A strategy of effective pre-oxygenation (with associated denitrogenation) is vital to maximise the time until haemoglobin desaturation. In time-critical settings, this is best achieved by eight deep breaths within 60 seconds with high flow oxygen delivered using a non-rebreathing facemask although this technique may not be suitable for heavily pregnant or uncooperative patients . Studies have also suggested that the process of apnoeic oxygenation by delivery of high flow oxygen via nasal speculum during apnoea significantly delays onset of hypoxaemia [30, 31].
An opiate, usually fentanyl or remifentanil , is routinely used as a pre-treatment agent during RSI of haemodynamically stable patients to obtund the sympathetically mediated hypertensive reflex of endotracheal intubation. In the presence of haemorrhagic shock, these drugs carry significant risk of precipitating hypotension and should therefore be omitted.
All induction agents can provoke hypotension in the presence of life threatening haemorrhage . Ketamine or etomidate are commonly used as they cause less haemodynamic compromise than other agents and exert rapid effects, even in the presence of shock . One review of anaesthesia in haemodynamically compromised emergency patients concluded that ketamine represented the best choice of induction agent, particularly in austere and remote healthcare settings . Ketamine, although negatively inotropic in vitro, causes less hypotension than most other agents due to a mechanism of endogenous catecholamine release [35, 36]. Ketamine can, however, provoke hypotension in shocked patients who are catecholamine depleted and so induction doses must be reduced for such patients. One review of ketamine administration as an induction agent for pre-hospital RSI highlighted that patients with a shock index (heart rate/blood pressure) ≥0.9 pre-intubation, were more likely to become hypotensive than those with a lower shock index <0.9 . Etomidate is also widely used although it has been withdrawn from use in some countries due to concerns about adrenal suppression . Whichever agent is chosen, providers must be fully conversant with the safety profile and modifications of dose regimes required in the presence of haemorrhagic shock.
Administration of a neuromuscular blocking agent (NMBA) to achieve paralysis greatly facilitates laryngoscopy and passage of an endotracheal tube between the vocal cords. Indeed, trauma patients who are able to tolerate this procedure without drug administration have been observed to have dismal outcomes . The resultant apnoea carries the risk of respiratory acidosis, hypoxia during the intubation process and hypotension when positive pressure ventilation is initiated. Suxamethonium or rocuronium have the most rapid onset of action and hence are the neuromuscular blocking agents of choice for intubation of patients with life threatening haemorrhage. When given at appropriate doses both have similarly rapid onset of paralysis . In the shocked state, higher range doses are required to achieve rapid onset of paralysis. A Cochrane review found no statistical difference in intubation conditions when succinylcholine was compared to rocuronium at a dose of 1.2 mg/kg but concluded that succinylcholine was clinically superior as it has a shorter duration of action . This may be a disadvantage in some settings. Rocuronium has fewer contraindications, causes no muscle fasciculation (and hence no increase in oxygen consumption) and has a much longer duration of action. Resuscitation teams must decide whether a short acting agent that then allows resumption of spontaneous, negative pressure ventilation during transport would be advantageous in the context of life threatening haemorrhage or whether more prolonged paralysis (and hence maintenance of positive pressure ventilation) is required to facilitate transport or surgical intervention. Other important considerations include the availability of a reversal agent for rocuronium (sugammadex) and product storage requirements .
Laryngoscopy to achieve endotracheal intubation for patients with life threatening haemorrhage carries risk of direct airway injury or failure to achieve intubation. For trauma patients with potential associated cervical spine injury there is a requirement to maintain manual in line stabilisation (MILS) . The resulting suboptimal anatomical position of the airway may significantly impede direct visualisation of the glottic opening. This may be improved by use of external laryngeal manipulation (ELM) or the application of “backwards, upwards, rightwards pressure” (BURP) [43, 44]. Both techniques have potential to significantly improve visualisation of the vocal cords and a gum elastic bougie should routinely be used to guide endotracheal tube placement. Fibre optic and video laryngoscope devices may give better views than direct laryngoscopy but may not be available in austere settings or effective in the presence of significant contamination of the upper airway.
Cricoid pressure is traditionally applied during paralysis in an attempt to protect from regurgitation of gastric contents prior to ETI placement although some authors highlight potential risks of this manoeuvre . It is clear that delays incurred whilst trying to visualise the glottis or due to multiple attempts at laryngoscopy carry the risk of hypoxia and so multiple attempts (more than three) or unnecessary delays must be avoided . Choice of endotracheal tube size is also vital to ensure success and minimise risk of harm. Pregnant patients may have respiratory tract mucosal oedema and capillary engorgement that can reduce the size of the glottic opening and so smaller endotracheal tubes should be used. Confirmation of correct placement of the endotracheal tube is best achieved using continuous wave form capnography to measure end-tidal carbon dioxide (EtCO2) .  Whilst other techniques including auscultation may be employed, they carry significant risk of failing to identify oesophageal intubation.
Positive Pressure Ventilation
A key concept in the safe and effective management of the airway for patients with life threatening haemorrhage is the impact of positive pressure ventilation on intrathoracic pressure. The adverse effect of positive pressure ventilation on cardiac output is well described . Intrathoracic pressure becomes raised during the inspiration phase of positive pressure ventilation. In patients with haemorrhagic shock this will reduce the already compromised venous return and hence reduce right ventricular output, pulmonary blood-flow and cardiac output . In human models of simulated shock states, the advantages of negative pressure ventilation have been demonstrated using negative pressure impendence devices . In porcine models of haemorrhagic shock the impact of positive pressure ventilation on cardiac output has been explored and compared to spontaneous, negative pressure ventilation. In one model of haemorrhagic shock, intubated animals undergoing positive pressure ventilation were demonstrated to have greater reduction in cardiac output and body temperature than non-intubated, spontaneously breathing animals . There appeared to be no survival advantage from intubation and positive pressure ventilation, emphasising that intubation and ventilation are not treatments for haemorrhagic shock but the unavoidable consequences of advanced airway care. When positive pressure ventilation is initiated, providers must employ a ventilation strategy that minimises the impact upon cardiac output. One porcine model of ventilation strategies in severe haemorrhagic shock demonstrated that reduction of end expiratory pressure was the factor that had greatest influence upon haemodynamic stability although decreasing tidal volumes and increasing respiratory rates also had beneficial effects . Positive pressure ventilation in the presence of haemorrhagic shock has also been suggested to be an independent cause of a more pronounced systemic inflammatory response although the effect of this upon acute traumatic coagulopathy remains unclear .
Following successful intubation, patients with life threatening haemorrhage will need appropriate on-going care, monitoring and reassessment of the impact of this intervention. In RDCR settings there will be a priority to transport the patient to an appropriate medical facility during which time sedation will need to be maintained and consideration given to maintaining paralysis with a long acting NMBA. Sedation is typically maintained with further bolus administration of a sedative agent such as ketamine that will have least impact upon haemodynamic stability and also provide analgesia. Ventilator settings must be optimised to minimise impact upon cardiac output and confer lung protection. Low tidal volumes (6–8 ml/kg) are typically used and respiratory rates adjusted to maintain appropriate EtCO2 levels, with initial rates of 8–10 breaths per minute. Positive end expiratory pressure (PEEP) should be maintained at 0 mmHg pending adequate resuscitation, unless there is significant concomitant lung injury that requires PEEP to improve oxygenation. In this scenario the least amount of PEEP needed to maintain oxygen saturations above 90% is reasonable. Post-intubation care for patients intubated in a medical facility, or arriving from the field already intubated, will similarly require maintenance of sedation, paralysis and analgesia and careful management of ventilator strategies. When effective haemorrhage control and resuscitation have been achieved, administration of opioid agents such as fentanyl may improve tissue perfusion and protect from reperfusion injury by achieving dilation of the microcirculation .
Special Situations: Head Injury
Patients with life threatening haemorrhage who also have traumatic brain injury (TBI) present special challenges to providers of airway care and ventilatory support. Such patients may initially be combative and resistant to attempts to provide appropriate airway care and in some instances, may have trismus, making assessment and support of the airway extremely difficult. Simple airway manoeuvres may be adequate but there may be a need for pharmacological assistance to facilitate simple interventions. Despite historical concerns about the use of ketamine in head injured patients, available evidence suggests that it is safe for such patients and may even have a neuroprotective effect [54, 55]. Use of low dose ketamine may allow improved pre-oxygenation prior to progression to rapid sequence intubation. Hypotension associated with administration of induction agents for rapid sequence intubation and positive pressure ventilation has been shown to have a detrimental effect upon cerebral perfusion and survival following TBI. A single episode of hypotension below 90 mmHg has been shown to be independently associated with more than a doubling of mortality in the presence of TBI . Any hypoxaemia associated with onset of apnoea or attempts to secure endotracheal intubation has also been shown to have a significant effect upon survival, with a single excursion of oxygen saturation below 90% associated with more than a doubling of mortality . The combination of both hypotension and hypoxia has been demonstrated to be associated with a six-fold risk of mortality in TBI . Furthermore, any over-enthusiastic hyperventilation of patients with TBI following intubation will provoke hypotension and vasoconstriction and hence reduce cerebral blood flow with consequent detrimental impact upon outcome . Providers must be mindful of these pitfalls when performing airway care in the presence of suspected head injury for the patient with life threatening haemorrhage.
Impact of Airway Interventions in Life Threatening Haemorrhage upon Outcomes
There can be no doubt that rapid intervention with basic airway skills to maintain oxygenation in patients with severe haemorrhage can be life-saving, particularly in the presence of direct airway injury or reduced levels of consciousness due to head injury or poor brain perfusion. But more advanced interventions, particularly when performed prematurely in under-resuscitated patients, can have harmful consequences. Interpretation of outcomes for patients with life threatening haemorrhage who undergo advanced airway interventions are potentially confounded by uncertainty about the causation of poor outcomes. Are they due to the underlying haemorrhagic shock state and any associated injuries or pathologies or are they due to the dangers of the airway intervention process and any associated delays? Evidence of the impact of pre-hospital intubation in less critically injured patients illustrates the potentially harmful consequences of this intervention. In one retrospective database review, adult trauma patients who were intubated before arrival in hospital, but who on retrospective review were considered to be only moderately injured, were matched with similarly injured patients who did not undergo intubation . Intubated patients were found to have spent longer on scene, had more volume replacement, more coagulation derangement and lower haemoglobin concentrations than the non-intubated patients, suggesting that the potential harm of this intervention must be considered by providers. As long ago as 1943 the potential hazards of anaesthesia in the presence of haemorrhagic shock were emphasised in descriptions of the use of barbiturate anaesthesia in shocked trauma patients at Pearl Harbour . One retrospective database review of trauma patients who received massive transfusion on arrival in hospital attempts to compare outcomes of these patients with life threatening haemorrhage who received RSI before arrival in hospital with those who didn’t . The authors observed an association between pre-hospital RSI and higher risk of mortality and concluded that this effect was likely to be due to the effect of RSI and ventilation but noted that it may have been due to the patient factors that caused providers to perform intubation in the field rather than waiting until arrival at hospital. A systematic review and meta-analysis of pre-hospital intubation comparing mortality rates of adult trauma patients who underwent pre-hospital intubation with those who were intubated in the emergency department also noted an association between pre-hospital intubation and higher mortality rates .
Intubation of shocked trauma patients also carries risk when performed in hospital. A study of the outcomes for adult trauma patients intubated on arrival at hospital noted higher mortality rates for those who suffered post-intubation hypotension . Overall, these studies would seem to support concern that emergent intubation of patients with life threatening haemorrhage carries significant risk of harm and that consideration should be given to deferring intubation, in the absence of airway obstruction, evidence of hypoxaemia, hypercarbia or other compelling indications, until measures can be taken to resuscitate the patient.