Prehospital emergency anesthesia (PHEA) is a procedure that brings a hospital level of emergency care to a critically-ill or injured patient in the prehospital environment.

It is a high stakes, highly skilled procedure that can only be performed by appropriately trained and skilled individuals – usually critical care trained doctors in conjunction with trained assistants. It is very much a ‘team sport’.

In our service, helicopter emergency medical services (HEMS) doctors (anesthetists or emergency medicine doctors) do the intubating, assisted by specially trained HEMS paramedics.

The stakes are high because, if it all goes well, the patient is getting a gold standard level of care at the roadside. However, if performed badly, it has the potential to worsen the patient’s outcome or, in a worst-case scenario, kill them.

What is it?

Simply put, PHEA is the administering of anesthetic drugs to a patient to facilitate endotracheal intubation, ventilation and then onward transfer of a patient to definitive care by air or road.

Benefits

Using an AB(C)D approach to describe the benefits of PHEA:

• Airway – Intubation ‘secures’ the airway and protects the lungs from blood, vomit and secretions
• Breathing – By paralyzing the patient’s muscles and artificially controlling the patient’s ventilation, optimal oxygenation is assured and the level of carbon dioxide can be altered at will – crucial for a patient with a head injury
• Circulation – PHEA is not indicated for patients with primary cardiovascular problems (eg hypovolemic shock) and, in fact, it has the potential to adversely affect the cardiovascular system – especially if performed with a heavy hand.
• ‘Disability’ (ie reduced consciousness level) – Patients who are completely unconscious lose their protective airway reflexes and are at risk of inhaling blood or stomach contents into their lungs. PHEA and intubating the trachea reduces the risk of this. Anesthetizing patients with head trauma makes them easier to assess and treat (especially if uncooperative or combative) and has benefits including optimizing oxygenation, ventilation and helping to ‘rest’ the injured brain. Transporting an agitated, combative patient with a head injury by air would be a nightmare for the team, and could potentially endanger the aircraft.

PHEA has many potential benefits for the critically-injured patient; however, it is not without risk. If done poorly it can have an adverse effect on the patient, worsening their outcome – the last thing the HEMS team is aiming to do.

Risks

If the HEMS team is then unable to manage the airway and ventilate the patient, the patient is likely to die

• Once the patient is anesthetized and paralyzed, they stop breathing. If the HEMS team is then unable to manage the airway and ventilate the patient, the patient is likely to die
• If patients are cardiovascularly unstable – eg due to bleeding – performing a PHEA may make them even more unstable or even cause cardiac arrest
• Any drop in oxygen levels (due to delays in intubating) or drops in blood pressure (caused by the drugs or positive pressure ventilation) are widely believed to worsen the outcome of patients with head injuries.

When a HEMS team might look to perform a PHEA

Airway problems

If a patient has actual or impending airway compromise:

• An unconscious patient who has an airway that is soiled with blood or vomit
• A patient with airway burns.

Recently, a patient who had attempted to hang himself had an airway obstruction due to swelling from the ligature – although difficult to intubate, he would probably have died if his airway had not been secured before being transferred to hospital.

Breathing problems

These could be due to chest injuries or due to medical problems such as severe asthma.

Recently, a motocross rider fell and sustained multiple bilateral painful rib fractures and was unable to breathe. His oxygen levels were deteriorating – the PHEA enabled us to optimally oxygenate him, package him and transfer him to the trauma center.

Cardiovascular problems

These are not of themselves usually an indication for PHEA and may make the patient worse.

Disability (‘brain problems’)

The most common reason that I tend to perform PHEA is for patients with head injuries. Head injury really refers to brain injury. Road traffic collisions and falls from height are very common causes. I’ve seen a lot of injured motorcyclists recently, not something I particularly like as I have three motorbikes myself!

Some patients with a head injury may not be completely unconscious but, as a result of their injury, may be agitated, combative and uncooperative. To begin optimal ABCD treatment and ensure safe and timely transfer to a trauma center, they may need PHEA.

Other indications

• These include humanitarian reasons (eg a patient with extensive severe burns or a patient who has undergone a prehospital amputation). A recent case involved a man who fell in a tank full of boiling water in a factory setting – he had 90 per cent burns. He was in agony – it was the kindest option to anesthetize him
• Anticipated clinical course – a patient who is almost certain to be going straight for computed tomography and/or to the operating theatre on arrival at hospital.

HEMS team approach

Our HEMS team at the Yorkshire Air Ambulance consists of a doctor and two paramedics. We will have agreed roles either earlier at the base or in the air. The doctor will be the intubator and prepares and checks the anesthetic drugs, one paramedic will be designated to prepare the ‘kit dump’ of PHEA equipment, and the remaining paramedic will assist with other necessary preparation.

A competent road crew can do a huge amount to help their patient get the PHEA they need

Pre-arrival preparation of the patient by road crews can be incredibly variable. A competent road crew can do a huge amount to help their patient get the PHEA they need. In an ideal world, when the HEMS team arrive on scene, the patient will be breathing 100 per cent oxygen, have a hard collar removed, be packaged on an ambulance trolley with 360 degree access all around, have two working drips in situ, and have monitoring attached, with suction nearby.

In a worst case scenario, the road crew may be so overwhelmed by the situation
and the patient’s injuries that they will not have been able to do any of these preparations after requesting HEMS. In this scenario, the PHEA and transfer to hospital may be delayed as the HEMS team will have to start the patient’s assessment and treatment from scratch.

There have been recent efforts to educate the paramedic crews in the region as to how they may help speed up the PHEA by preparing and packaging the patient pre-HEMS arrival.

Once the patient has been reassessed and the HEMS team agrees that the patient needs PHEA, the team splits into roles. PHEA is a team sport – the whole team needs to be in agreement that the patient needs PHEA and understands their role.

• HEMS Doctor: Draws up the intubation drugs, manages the patient’s airway and intubates the patient
• HEMS Paramedic (1) PHEA assistant: Prepares a ‘kit dump’ of the airway and ventilation equipment immediately adjacent to the patient.
• HEMS Paramedic (2): PHEA preparation.

The ‘kit dump’ is prepared so that the intubating assistant and the intubation equipment are to the doctor’s immediate right. The equipment includes emergency airways devices to be used if intubation proves to be impossible and includes a surgical airway kit.

We have tried to standardize our range of drugs and their doses to reduce cognitive load on the team and increase situational awareness – the whole team will be familiar with the agents and typical doses. We use prefilled syringes for the anesthetic drugs to reduce errors that may occur when drawing them up. We use:

• Fentanyl (opioid): to reduce the body’s sympathetic nervous system response to intubation (which may potentially harm the patient)
• Ketamine: to put the patient ‘to sleep’ and reduce brain oxygen consumption
• Rocuronium (muscle relaxant): paralyses the patient, making it easier to intubate the patient and stops them breathing so we can ventilate them mechanically.

The doses are standardized but may be reduced according to ‘gut instinct’ of the doctor. Typically, when patients are frail, elderly or highly unstable.

Although there are several anesthetic drugs in common use, we use ketamine as it tends to maintain the patient’s blood pressure. Most other anesthetic drugs tend to drop the blood pressure – potentially disastrous if the patient already has a low blood pressure as a consequence of their injuries.

The ‘kit dump’ is prepared using a checklist. Cognitive aids may be used, such as a shadow board – a sheet of plastic with the pictures of the equipment laid out on it. This reduces cognitive load in what may be very stressful, time-pressured circumstances.

Equipment must be present and checked. After the drugs have been given and the patient has stopped breathing is not the time to discover absent or failed airway equipment.

The remaining HEMS paramedic ensures the patient is packaged and prepared for rapid sequence intubation (RSI). The patient must:

• Be off the ground (preferably on an ambulance trolley) – intubating on the ground is much more difficult
• Have two working drips: ‘two is one and one is none’
• Be breathing 100 per cent oxygen – to create an ‘oxygen reserve’ that buys time to intubate once the patient is paralyzed and has stopped breathing

  Suction must be running and immediately available in case the airway is soiled

• Have monitoring attached and be visible at all times to the HEMS doctor operator. A full set of observations must be completed immediately before and after the PHEA is performed to see what effect the PHEA is having on the patient’s cardiorespiratory system
• Suction must be running and immediately available in case the airway is soiled
• The ventilator (Oxylog 3000) must be prepared and set up.

Once the patient is prepared, a challenge response checklist is used to confirm that this is the case, and the necessary equipment and drugs are checked and immediately available.

Depending on available personnel, there may be paramedics or other competent individuals asked to perform manual inline immobilization of the patient or cricoid pressure.

Controversies

Manual inline immobilization of the neck

If there is a suspicion that the patient may have a spinal injury (especially likely if the patient has sustained a head injury), then a spare paramedic (or other competent person) may be delegated to hold the patient’s head still during intubation. It’s important that they keep out of the operator’s way and don’t accidentally hold the patient’s mouth shut.

Manual inline immobilization is a controversial topic. Increasingly, people are de-emphasizing it – the theory is that any significant spinal injury occurs at the time of injury and small movements during intubation are unlikely to have a significant impact. Movement of the neck may be necessary to intubate the patient. As a colleague once explained, it’s not a success if the patient has a pristine neck but died because no one could manage the airway successfully!

A pragmatic approach is to minimize moving the patient’s neck as much as possible while recognizing that securing the airway is the main priority and may require a degree of neck motion.

Cricoid pressure

Cricoid pressure is when a trained assistant exerts pressure on the front of the neck (on the cricoid cartilage) during intubation. The idea is that pressure on this cartilage compresses the adjacent esophagus and thus reduces the chance of stomach contents coming up into the mouth and then down into the lungs before the trachea has been protected by intubation.

This is also a controversial topic. Although traditionally performed as part of hospital emergency anesthesia for decades, there is no strong scientific evidence supporting it. However, there is a lot of evidence showing that cricoid pressure makes all phases of airway management (including intubation) more difficult!

There are concerns, however, that it is currently a standard of care in the UK, and that not performing cricoid pressure could potentially result in criticism.

One pragmatic approach is to start with cricoid pressure and if it is making intubation or ventilation more difficult ask for it to be released immediately – at least you’ve ticked the box.

After the checklist has been completed, I’ll ask the team if we’re all happy to proceed. On occasion I may request silence from the other emergency services present – it can be very distracting having generators running, power tools operating or loud conversations going on nearby when you are about to intubate.

Intubation is confirmed by looking for CO2 on the monitor and listening to the patient’s chest bilaterally

The patient breathes oxygen for three minutes to create an oxygen reserve, the drugs are given and, all being well, the patient is intubated and attached to the ventilator by the doctor. Intubation is confirmed by looking for CO2 on the monitor and listening to the patient’s chest bilaterally. A set of observations is performed and if the patient is stable, they are transferred to an appropriate vehicle for onward transfer. We are now in total control of the patient’s airway and breathing.

What if the patient is difficult to intubate?

If there is difficulty intubating, the operator (doctor) will declare to the team: “This is a difficult intubation.”

They will have three attempts to intubate, each time trying something to optimize the view of the vocal cords and trachea. If, after three attempts, they are still unable to intubate the patient, the focus then becomes on oxygenating and ventilating the patient by any means possible. A sequence of airway ‘Plans’ is worked through:

• Plan A – intubating the patient.

If this fails:

• Plan B – using an iGel airway to ventilate the patient. This is usually successful.

However, if this fails:

• Plan C – using oral/nasal airways and bag valve mask to ventilate the patient.

If this fails:

• Plan D – perform an emergency surgical airway making hole in the neck with a scalpel and intubating the hole.

If this fails:

• The patient will die.

Common errors

The key to PHEA is getting the basics right. I have learned the hard way that in particular:

Don’t try to intubate with the sun in your eyes

• Don’t try to intubate with the sun in your eyes – you can’t see anything. Position the patient so the sun is at your back or be in the shade
• Never trust a drip you haven’t put in (or at least checked) yourself. We have had a few patients over the years who didn’t get anesthetized after the drugs were given – it was always the drip not being correctly sited that was the issue
• “Two is one and one is none.” Always have two drips – one will always fall out while transferring to a vehicle.

Helicopter vs road transport

The decision to transport via road or air may be a difficult one and is multifactorial. Questions that I ask myself are:

• Are there any secondary transfers? It’s no advantage to be able to fly at 150kn if you need to transfer the intubated patient via ambulance or long carry to the aircraft followed by landing in a field near a hospital and waiting for an ambulance to transfer you from the aircraft 100m to the emergency department. Secondary transfers kill the time advantage of using aircraft except for very long journeys

  If the patient is likely to require any interventions en route, road transfer may be preferable

• How stable is the patient? If the patient is likely to require any interventions en route, road transfer may be preferable. Assessing a patient in an aircraft is much more difficult due to the noise and vibration. Assessing a chest with a stethoscope, performing or re-fingering thoracostomies, or reintubating a patient may be very challenging. If there are doubts about the patient’s stability, road transport may be a better option
• How far away is definitive care? If an ambulance journey may be prolonged due to a remote location then air transport may be preferable – even if the patient is not stable.

These decisions often need a team discussion and local knowledge. There are often no absolute rights or wrongs – except in retrospect.

Aftermath

PHEA should only be undertaken by organizations with a robust governance system. All personnel must be appropriately skilled, trained and signed off – including PHEA assistants. Regular simulation training as a team is especially important and may uncover potential weaknesses.

In our service, each PHEA is reviewed by the team at our six-weekly governance meeting. We discuss scene time, drug doses, and adverse events, and look at the pre- and post-PHEA observations.

Decision making may be examined in a spirit of trying to learn and improve for the future.

Summary

PHEA is a high-stakes, highly skilled procedure that must be performed by a team with appropriate training and skills.

It has the potential to provide a subset of critically-ill or injured patients with hospital levels of care – however, if performed badly, it may adversely affect the patient’s outcomes.

Drugs, equipment and procedures should be standardized and drilled in a simulated environment.

Checklists should be used pre- and post-intubation to reduce cognitive load in this high pressure situation.

PHEA must take place within a robust governance framework.