BP, blood pressure; HR, heart rate; K, potassium; ICP, intracranial pressure; IOP, intraocular pressure; PRN, as needed; RSI, rapid sequence induction

Suctioning

Suctioning is an adjunct to manoeuvres to open or maintain the airway. It is used to remove tracheobronchial secretions via an endotracheal tube.

Yankauer sucker is used to remove secretions, blood, vomitus or foreign body from mouth and pharynx. In the unintubated patient, turn the patient on the side during suctioning.

Y-suction catheter with a soft tip is used for nasopharyngeal and tracheobronchial secretions. Catheter diameter should not be more than half the diameter of the endotracheal tube.

Preoxygenate and bag-valve-tube ventilate the patient before and after suctioning to prevent hypoxaemia and pulmonary collapse.

Oxygenation and ventilation

Ventilator settings require decisions about minute ventilation, respiratory rate, inspired oxygen concentration, peak airway pressure and the use of positive end-expiratory pressure. (See the section ‘Choosing initial settings for ventilation’ in this chapter.)

Monitor peak airway pressure as well as oxygen saturation, capnography and blood gases. Aim for oxygen saturation above 95% and mild hypocapnia.

A disconnection alarm must be used during mechanical ventilation.

Complications of intubation

• During intubation: trauma to any structure from lips to the trachea; inability to oxygenate, ventilate or intubate; exacerbation of spinal cord injury; aspiration; haemodynamic collapse.

• While tube is in place: misplacement; blockage; problems related to the ventilator.

• After extubation: laryngospasm; aspiration; complications of trauma.

Extubation

1. The patient must be fully awake and have a gag reflex before extubation.

2. Non-depolarising neuromuscular blockade can be reversed with neostigmine (an anticholinesterase) and atropine (prophylactic antimuscarinic). Antagonists to midazolam and morphine are only rarely required.

3. Preoxygenation, suctioning of pharynx, trachea and intragastric tube should precede extubation, which is performed at the peak of inspiration.

4. Ensure oxygenation after extubation with a bag-valve-mask or a non-rebreathing mask.

Alternative airway techniques

Nasotracheal intubation. Can be performed without direct laryngoscopy in the non-apnoeic patient (the ‘blind’ technique). It is an appropriate alternative to orotracheal intubation in confirmed unstable cervical spine injury or spinal cord injury, in severely dyspnoeic awake patients who can be intubated in the sitting position, and in patients unable to fully open their mouth. It is contraindicated in patients with maxillofacial and anterior cranial fractures, and with conditions such as nasal polyps, upper airway foreign bodies and retropharyngeal abscesses.

Laryngeal mask airway. Consists of airway with elliptical cuffed ‘mask’ on distal end which rests over the larynx when inserted. Low pressure ventilation may be performed, but it does not reliably prevent aspiration. Is quicker and an easier technique to learn than endotracheal intubation. Has an established role to provide an airway in the fasted patient during anaesthesia. Is a useful temporising technique if intubation skills are not available. When direct laryngoscopy and intubation fails it may serve to provide a functional airway until definitive intubation by cannulation of the trachea through the mask is performed.

Oesophageal–tracheal airway (‘combitube’). Consists of twin-lumen tube with one lumen inserted into the oesophagus and the other lying above the trachea. A pharyngeal balloon provides a seal to enable ventilation. A distal balloon seals against gastric inflation and aspiration. Is an alternative to laryngeal mask airway if intubation skills are not available.

Airway bougie. An extension of the use of an ‘introducer’, this is used for a ‘difficult’ intubation. A long semi-rigid bougie is inserted between the vocal cords and the endotracheal tube is then passed over the bougie into the trachea. The bougie is then removed.

Transillumination intubation. Useful when a ‘difficult’ intubation is predicted. May be combined with rapid sequence induction. Distal end of tube is bent and a rigid lighted stylet is used to guide the tube into the larynx and signify correct placement. The rigid trocar is removed for nasotracheal intubation. Requires minimal training to use.

Fibre-optic intubating laryngoscope. Alternative to transillumination intubation if rapid sequence induction is contraindicated. Intubation is performed under local anaesthesia, preferably via the nasotracheal route. The laryngoscope is directed into the larynx and then acts like a guidewire for the tube. Requires a significant amount of training and is not in widespread use. Devices aiding view and intubation via a visual monitor are increasingly available as back-up.

Translaryngeal oxygenation. Indicated when non-surgical airway management has failed, is contraindicated or is not available (total upper airway obstruction). Preferred to cricothyroidotomy in child under 8 years of age. Temporising oxygenating procedure, does not prevent aspiration, may lead to hypercarbia and is not effective if a foreign body is present below the cricoid cartilage.

Cricothyroidotomy. Alternative to translaryngeal oxygenation. May be used after temporising with translaryngeal oxygenation. Preferred to tracheostomy, which should be reserved for the operating room. Percutaneous approach (Seldinger technique) is easiest and fastest. Using a surgical approach, insert a small endotracheal tube or tracheostomy tube. When the patient is stable, convert to tracheostomy or orotracheal tube.

Guidelines for ‘difficult’ intubation

1. If ‘difficult’ intubation is predicted but is not urgent, seek assistance from an experienced operator.

2. Assemble the available ‘difficult’ airway equipment. In many institutions it is thought that direct visualisation of the larynx with a standard laryngoscope handle and blade in the management of the anticipated difficult airway is no longer acceptable. Consideration of tools such as the Glidescope or fibreoptic bronchoscope is strongly recommended in such situations. Use of these devices in routine securing of the airway results in proficient use in the emergency situation.

3. Assess whether successful bag-valve-mask ventilation is likely.

4. Use an airway bougie (or transillumination intubation if available) if ‘difficult’ intubation is predicted.

5. Nasotracheal intubation, awake intubation or use of the fibre-optic intubating largyngoscope are options if successful bag-valve-mask ventilation is considered unlikely.

6. Avoid use of muscle relaxants if successful bag-mask-valve ventilation is considered unlikely.

7. If the initial attempt at orotracheal intubation fails and the patient has been paralysed, institute bag-valve-mask oxygenation and ventilation, then use BURP or an airway bougie and re-attempt intubation.

8. A ‘difficult’ intubation occurs if orotracheal intubation cannot be achieved after two attempts under direct laryngoscopy. Resume bag-valve-mask oxygenation and ventilation. Then re-attempt intubation using BURP or an airway bougie, or consider using a laryngeal mask airway, an oesophageal–tracheal airway or transillumination intubation.

9. If attempts at bag-valve-mask oxygenation and ventilation fail, escalate the use of a laryngeal mask airway or oesophageal–tracheal airway to reoxygenate. Consider passing airway bougie or endotracheal tube though the laryngeal mask.

10. Translaryngeal oxygenation or cricothyroidotomy are indicated when non-surgical airway management fails.

The difficult airway trolley

It is essential that all emergency departments have a difficult airway trolley. It should be well-organised and have clearly labelled contents. The exact contents of a difficult airway trolley may vary but should include a limited selection of tools to assist in securing the airway. The field of airway management is changing rapidly with new and, sometimes, improved devices becoming available. The trolley should reflect this. Its contents should be revised regularly and, if necessary, updated.

• laryngeal mask airways

• supraglottic devices, such as combitube

• lighted stylet, such as Trachlight

• flexible fibre-optic laryngoscope

• surgical airway, including commercial devices to perform cricothyroidotomy with a modified Seldinger technique.

SURGICAL AIRWAY

Refer to Chapter 3, ‘Resuscitation and emergency procedures’.

VENTILATORS

(Judy Alford)

Ventilators are used in the emergency department to assist or control the respiration of patients. Patients needing invasive ventilation need an artificial airway, most commonly an endotracheal tube. The level of ventilatory support needed by a patient varies widely. Some have essentially normal lungs (e.g. sedative overdose), while others have severe respiratory failure.

Indications for ventilation fall into three broad categories:

1. Respiratory failure

• Airway obstruction

• Neuromuscular weakness (spinal cord injury, myasthenia gravis, organophosphate poisoning, exhaustion)

• Chest wall disorders (deformity, flail chest, morbid obesity)

• Pleural disease (massive effusions, pneumothorax or haemothorax)

• Parenchymal lung disease (infection, adult respiratory distress syndrome (ARDS), pulmonary oedema, fibrosis, asthma, chronic airflow limitation (CAL))

2. CNS disease

• Poisoning

• Trauma

• Cerebrovascular accident (CVA)

• Infections

3. Circulatory failure

• Hypovolaemia

• Sepsis

• Cardiogenic shock

The type of ventilator used in the emergency department is usually small and portable. The range of ventilatory modes available varies, but is usually less than is available on more complex machines in the ICU. Nonetheless most patients can be managed in the short term.

Choosing initial settings for ventilation

Initially, ventilator settings are estimated; adjustments should be made according to the patient’s clinical progress and serial blood gas measurements.

Is the patient breathing spontaneously?

Spontaneously breathing patients are ventilated using a mode that assists each inspiratory effort by providing extra pressure or volume. Examples are continuous positive airway pressure (CPAP) and pressure support. Some ventilators and their circuits increase the work of breathing significantly and spontaneous breathing may not be tolerated. In these cases, the patient may need to be sedated and fully ventilated.

The patient who is not breathing adequately needs a mode that does all the work for them. Intermittent positive pressure ventilation (IPPV) or intermittent mandatory ventilation (IMV) provides a breath at a preset rate regardless of the patient’s respiratory effort. Some ventilators can deliver a breath synchronised to an inspiratory effort; this is known as synchronised intermittent mandatory ventilation (SIMV).

How much oxygen does the patient need?

In all cases, start ventilation with 100% oxygen and titrate downwards according to the patient’s arterial blood gases (ABG) results. Some ventilators have limited options in selecting an inspired oxygen level. In patients who are inadequately oxygenated, postive end-expiratory pressure (PEEP) can increase the arterial oxygen tension for a given level of inspired oxygen.

How much gas should the patient receive?

The minute volume is the amount of gas moved every minute:

The arterial tension of carbon dioxide is sensitive to changes in minute volume. Increasing the minute volume reduces the partial pressure of CO₂ (PaCO₂) and decreasing the minute volume raises PaCO₂. In patients with raised intracranial pressure, it may be necessary to deliberately hyperventilate to maintain a modest decrease in PaCO₂. In some patients with lung injury, trying to deliver a ‘normal’ minute volume may pose a risk of barotrauma. In these cases, the PaCO₂ may be allowed to rise quite significantly, an approach called permissive hypercapnia.

The ventilators in common use apply positive pressure to the lungs to enable gas movement. The amount of gas moved per breath depends on the ventilator settings and the lung compliance.

Ventilators can be set to deliver a given tidal volume at each breath. This mode is called volume control and is available on even the most basic machines. It may be possible to limit the delivery of the set volume if the airway pressures exceed a limit chosen by the operator (pressure-regulated volume control (PRVC) mode).

Pressure control is a mode commonly used in the ICU but not always available on smaller ventilators. A constant airway pressure is provided during inspiration, with the tidal volume varying. This approach is often used where barotrauma is a concern.

Lung compliance is the change in lung volume for a given change in transpulmonary pressure. Diseased lungs often have abnormal compliance (e.g. in pulmonary oedema the lung is less compliant or ‘stiffer’). Trying to deliver a ‘normal’ tidal volume to a poorly compliant lung can cause high airway pressures, increasing the risk of pneumothorax. Overdistension can worsen lung damage. The approach to ventilating is usually one of providing limited tidal volumes (6–8 mL/kg, sometimes less) with PEEP. This can be done using either volume or pressure control.

The choice of initial tidal volume depends on the clinical situation. In patients with respiratory failure or shock, a volume of 6–8 mL/kg is safest. Patients with normal lungs may tolerate tidal volumes of 10 mL/kg. Inspiratory pressures should not exceed 30 cmH₂O.

Positive end-expiratory pressure (PEEP)

PEEP leaves a constant pressure on the lungs at the end of expiration, preventing the collapse of alveoli. Constant opening and closing of alveoli can damage them. Using PEEP may prevent further lung injury as well as maintaining functional residual capacity. As noted earlier, PEEP has a positive effect on oxygenation. However PEEP has a negative effect on cardiac output because high intrathoracic pressures impede venous return. High levels of PEEP may not be tolerated in haemodynamically unstable patients. Another factor to be considered is ‘auto-PEEP’. This is the pressure difference between the alveoli and the proximal airway at end-expiration, which can be raised in conditions with air-trapping, such as severe asthma. ‘Auto-PEEP’ can contribute to haemodynamic instability in some patients. Prolonging expiration may help to reduce air-trapping in affected patients.

Choosing a level of PEEP

PEEP of 5 cmH₂O is tolerated by most patients. In patients with severe lung disease, increases in PEEP up to about 12 cmH₂O may be needed. PEEP may not be tolerated in patients with haemodynamic instability. Another group of patients who may not tolerate PEEP have raised intracranial pressure. In some cases the reduction in cerebral venous return may be enough to exacerbate the increase in intracranial pressure.

Special situations

Asthma

Use low respiratory rates with a prolonged expiratory phase to limit gas-trapping. Auto-PEEP may be significant, so additional PEEP may lead to hypotension. Avoid large tidal volumes. Permissive hypercapnia may be needed.

Raised intracranial pressure

Avoid hypercapnia. Maintain PaCO₂ between 30 and 35, using end-tidal monitoring and ABG. High levels of PEEP should be avoided.

Adult respiratory distress syndrome (ARDS)

ARDS is a difficult problem. The ideal ventilatory strategy is controversial. In the emergency department the key points are: 1) to avoid barotrauma by using small tidal volumes and avoiding high airway pressures; 2) to use PEEP as tolerated and tolerate a high PaCO₂. Paralysis may be necessary. Frequent adjustments to tidal volume and respiratory rate may be needed.

Troubleshooting

• Ask for advice early.

• Never assume the monitor is the thing not working.

• If there is difficulty ventilating the patient, immediately remove the patient from the circuit and commence bag ventilation with 100% oxygen. Check the endotracheal tube for kinking, displacement (in or out), obstruction and leaking. Examine the patient for equal and adequate breath sounds. Check the trachea is midline. If breath sounds are diminished, suction for mucous plugs and consider treating for a pneumothorax. Treat bronchospasm or pulmonary oedema if present. Get a chest X-ray. Consider bronchoscopy.

• If all of the above are normal, the problem may be with the machine. The ventilator may be disconnected (from the circuit, the gas supply or the power supply). There may be leaks in the tubing or valves, or tubing may be obstructed. Consider changing the circuit.

Non-invasive ventilation

Non-invasive ventilation using positive pressure via a face or nasal mask has become widely used in emergency departments. Most commonly a bi-level positive airway pressure (BiPAP) machine is used, although conventional pressure cycled ventilators can also be used.

The machine delivers a constant low level of positive pressure, which is increased upon sensing the patient’s inspiratory effort. This increased inspiratory pressure is equivalent to pressure support ventilation but, when setting the machine, the inspiratory positive airway pressure (IPAP) should be set at a level equal to the sum of PEEP and pressure support (e.g. an IPAP of 15 and an expiratory positive airway pressure (EPAP) of 5 is equivalent to pressure support of 10 and PEEP of 5).

Indications

• Acute respiratory failure due to pulmonary oedema, CAL, asthma, pneumonia

• Chronic respiratory failure due to neuromuscular conditions

• Obstructive sleep apnoea

Contraindications

• Apnoea or impending cardiorespiratory arrest

• Haemodynamic instability

• Risk of aspiration

• Decreased level of consciousness

• Inability to cooperate with mask

Problems with BiPAP

The mask may not be tolerated for the following reasons:

1. skin irritation and pressure necrosis

2. conjunctival irritation or injury

3. aspiration

4. gastric over-distension

5. hypotension due to raised intrathoracic pressure

6. progressive respiratory failure despite BiPAP, which is an indication for intubation.

PROCEDURAL SEDATION

Procedural sedation (also known as conscious sedation) refers to administration of sedative drugs to facilitate performance of a distressing or painful procedure. The level of sedation required varies with the procedure and the individual patient. The level of sedation falls short of general anaesthesia. The patient should retain the ability to respond to stimulus and airway reflexes should be maintained.

Requirements

Procedural sedation should be undertaken in an area with working suction and oxygen. Pulse oximetry should be used. Continuous ECG and blood pressure monitoring may be used in selected patients (e.g. older or with cardiac history). Ready access to resuscitation equipment and emergency drugs is essential. At least one person should be present who has skills to manage any complications, including airway obstruction and cardiac arrest. All patients should have details recorded on a standard form. See Figure 2.4.

Figure 2.4 Anaesthetic procedural sedation assessment

Fasting status does not necessarily preclude the use of sedation, but does influence the depth of sedation induced.

Drugs

The ideal drug for procedural sedation has rapid onset and offset, has no significant side effects, preserves airway reflexes and is easily titrated. Some commonly used agents are found in Table 2.2.

Table 2.2 Drugs used in procedural sedation

Drug	Dose	Duration
Midazolam	0.02–0.1 mg/kg IV 0.05 mg/kg PO (onset about 20 minutes)

30 minutes IV

45–60 minutes PO

Fentanyl 2–3 μg/kg IV 20–30 minutes Propofol 0.5–1 mg/kg IV 10 minutes Ketamine

Nitrous oxide

Given as 30–50% mix in oxygen

Causes expansion of gas-filled structures (e.g. pneumothorax)

5 minutes

Aftercare

The patient should be monitored until they have emerged from sedation. It is not uncommon for patients to become more deeply sedated once painful stimulus has ceased.

Patients should not be discharged from the emergency department until they have returned to their baseline mental state, are ambulant and have safe transport and supervision. Patients with poor social circumstances may require a longer period of observation.

EDITOR’S COMMENT

In the management of an urgent airway problem, always have a prepared back-up plan in case the current manoeuvre is unsuccessful.

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