Effective and timely airway management is a priority for sick and injured patients. The benefit and conduct of pre-hospital emergency anaesthesia (PHEA) and advanced airway management remains controversial but there are a proportion of critically ill and injured patients who require urgent advanced airway management prior to hospital arrival1 and the evidence shows us the benefits of this procedure when carried out with the appropriate training, education, robust competency framework and overarching clinical governance. It is a challenging procedure, and repeated attempts endotracheal intubation is associated with increased morbidity and mortality. It follows that this is a skill that should only be performed by appropriately trained and competent practitioners working in a properly structured prehospital system. This includes the mandatory use of standardised RSI checklists which have been proven to reduce cognitive load, eliminate individual practitioner variability, reduce error, and confirm availability of equipment, doses of drugs and failed intubation management plans.
Standards of practice and monitoring should be similar to those recommended for in-hospital anaesthesia.
Emergency anaesthesia is carried out to facilitate control of the airway and ventilation of critically ill patients. There are four broad indications for the procedure:
- Failure of airway maintenance or protection
- Failure of oxygenation or ventilation
- Predicated clinical course/humanitarian reasons
- To facilitate safe transportation
The decision to perform prehospital anaesthesia should be based on a thorough consideration of the RISKS vs BENEFITS to the individual patient. This should take into account:
- Estimated transfer time to definitive care
- Clinical indications for performing prehospital anaesthesia
- Skill set available
- Relevant patient comorbidities
- Alternatives
| Factors in favour of on-scene intubation | Factors against on-scene intubation |
|---|---|
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Time pressures in the pre-hospital environment mean practitioners rarely have the luxury of performing a comprehensive airway assessment. Tools such as the Aintree six-step approach to potentially difficult airways highlight the following important questions to ask prior to setting up for an RSI/DSI:
- How much time do I have?
- What access to the airway is available?
- How compromised is the airway?
- What fascial planes are involved?
- What management plan best fits the circumstances?
- Could I make the situation worse? If so, how?
Additionally, cognitive aids such as the Airway Assessment chart displayed, take from The Vortex approach, provide a simple way of approaching an airway assessment.
- Always use the RSI checklist to facilitate set up and preparation
- Establish bilateral IV/IO access
- Establish monitoring (SpO2, ETCO2, NIBP – cycling every 3 minutes, ECG)
- Assemble dump kit
- Prepare pre-drawn RSI medication and doses
- VAPORS assessment
- Establish failed intubation plan and equipment
- Optimise patient environment
- Upright position if possible or 30 degree tilt
- OOPS ("Oxygen On, Pull mandible forward, Sit upright if possible")
- C-spine conisiderations
- Check IV/IO access patent
- Prehydration with fluid +/- blood
- Optimise haemodynamics
- Consider inotropic support
Preoxygenation is vital for safe prehospital anaesthesia and should proceed through the entire preparation phase. A variation to RSI is that of DSI or Delayed Sequence Induction, which is generally described as the process of pre-oxygenation with sedation in advance of paralysis.
The table below illustrates a guide for the most appropriate form of preoxygenation for different patient groups as per their risk category:
Table 1: Risk categorization of patients during preoxygenation
Risk Category Based on pulse oximetry whilst receiving high flow oxygen | Preoxygenation Period (3 minutes) | Onset of muscle relaxation (~ 60 seconds) | Apnoeic period (Variable duration dependent on airway difficulty, ideally <30 seconds) |
|---|---|---|---|
| Low risk (SpO2 96-100%) |
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| High risk (SpO2 91-95%) |
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| HYPOXAEMIC (SpO2 <91%) |
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- Consider fluid challenge (blood or crystalloid) and/or inoptropic support for haemodynamically compromised.
- Fentanyl
- 2-3mcg/kg IV / IO
- Indicated in raised ICP and cardiovascular disease (e.g. great vessel rupture/dissection, aneurysmal disease, IHD)
- Helps decreases catecholamine discharge secondary to intubation, thus decreasing risks associated with increases in blood pressure in patients with cardiovascular disease, aortic dissections etc.
- Ketamine
- 1-2mg/kg IV / IO
- Indicated for any RSI.
- Use cautiously with active cardiovascular injury (MI) or heart failure.
- Ketamine exerts complex pharmacological actions including inhibition of biogenic amine uptake, binding to opioid receptors. Synergistic effect with opioids to produce desired sedation and analgesia.
- Apnea is a rare side effect of ketamine.
- Midazolam
- 0.03 mg/kg
- Indicated for patients with ketamine sensitivity or contraindications to same. (Thyroid replacement therapy or known allergy.)
- Use cautiously due to vasodilator and respiratory depression.
Pre-drawn RSI drugs in standardised concentrations have been introduced as a means of reducing drug related errors.
- Fentanyl: 500mcg in 20ml (25mcg/ml)
- Induction dose of 1-3mcg/kg
- Ketamine: 200mg/20ml (10mg/ml)
- Induction dose of 1-2mg/kg
- Rocuronium: 200mg in 20ml (10mg/ml)
- Induction dose of 1.2-2mg/kg
- Consider BURP/bimanual laryngoscopy to facilitate passing the tube
- Maintain sight of tube passing through cords and position appropriately
- Confirm placement by visualization, auscultation, etCO2 (6 non diminishing wave forms)
- Use of RSI post intubation checklist
- Note position of ETT at teeth
- Secure tube (consider tape in head injured/children)
- Secure all lines/equipment
- Appropriate sedation and paralysis
- Establish appropriate ventilator settings for patient condition
- Check VBG to titrate settings to clinical condition
- Use of Pre-scene departure checklist for packaging and final checks
Table of initial ventilator settings and tips for titrating
| Parameter | Normal lungs | ARDS/ALI | Asthma/COPD | Metabolic Acidosis | Head Injury | Severe obesity | |
|---|---|---|---|---|---|---|---|
| Aim | Lung protective strategy | Recruitment, shunt retention, avoid atelectic trauma, achieve adequate oxygenation | Oxygenation, adequate exhalation avoiding breath stacking and volutrauma | Ensure adequate respiratory rate to maintain and even improve compensation for metabolic acidosis | Avoid reduced venous return by avoiding high intrathoracic pressures | Avoid atelectasis and shunting due to obesity | |
| Position | 20-30 degree head up unless hypotensive and reduced cerebral perfusion a concern | ||||||
| Mode | VC (SIMV) | VC (SIMV) | PC (APRV equiv.) | VC (SIMV) | VC (SIMV) | VC (SIMV) | VC (SIMV) |
| VT (mL/kg) | 8 | 6 | monitor | 5-8 | 8-10 | 6-8 | 8-10 |
| Respiratory rate | 14 | 14 | 14 | 8-10 | 20-30 | 16 | 14 |
| I:E Ratio | 1:2 | 2:1 | 2-4:1 | 1:4-1:5 | 1:1-1:2 | 1:2 | 1:1-1:2 |
| Pinsp (cmH2O) | - | - | 25-30 | - | - | - | - |
| PEEP (cmH2O) | 5 | 10-15 | 10-15 |
| 5 | 5 | 10-15 |
| FiO2 | Start at 100% and rapidly titrate down, ideally achieving FiO2 0.4. Avoid significant hyperoxia. Aim for oxygen saturations > 95%; pO2 >80. Aim Pplat <30. | ||||||
| Other | Adjust parameters to ensure O2 and CO2 within normal limits | Watch pressures; may need to lower Vt and accept higher CO2. Titrate FiO2 and PEEP | Minimise derecruitment | Minimise derecruitment, i.e. minimise suctioning and disconnection. Consider recruitment manoeuvres | Watch for breath stacking and volutramua or barotrauma. Consider permissive hypercapnia. pH >7.15. May need to accept higher peak pressures in asthmatics. Aim Pplat <30 | Avoid high PEEP if possible. Aim PCO2 35-40. Tape rather than tie ETT to avoid impeding jugular vein flow. | Minimise decruitment, i.e. minimise suctioning and disconnections |
Christine M. Groth, Nicole M. Acquisto, Tina Khadem. Current practices and safety of medication use during rapid sequence intubation,Journal of Critical Care,Volume 45,2018,Pages 65-70,ISSN 0883-9441,https://doi.org/10.1016/j.jcrc.2018.01.017.
Brandon G. Santoni, Ph.D. ; Bradley J. Hindman, M.D. ; Christian M. Puttlitz, Ph.D. ; Julie B. Weeks, M.P.T. ; Nathaniel Johnson, B.S. ; Mazen A. Maktabi, M.D. ; Michael M. Todd, M.D.Manual In-line Stabilization Increases Pressures Applied by the Laryngoscope Blade during Direct Laryngoscopy and Orotracheal Intubation. Anesthesiology January 2009, Vol. 110, 24–31.https://doi.org/10.1097/ALN.0b013e318190b556
Jeffrey L. Jarvis, MD. 2016. Using DSI to Prevent RSI from Becoming RSD (Rapidly Sequenced Death). Williamson County EMS. http://txemsa.com/using-dsi-to-prevent-rsi-from-becoming-rsd
Manoach, Seth & Paladino, Lorenzo. (2007). Manual In-Line Stabilization for Acute Airway Management of Suspected Cervical Spine Injury: Historical Review and Current Questions. Annals of emergency medicine. 50. 236-45. 10.1016/j.annemergmed.2007.01.009.
Robitaille A, Williams SR, Tremblay MH, Guilbert F, Thériault M, Drolet P. Cervical spine motion during tracheal intubation with manual in-line stabilization: direct laryngoscopy versus GlideScope videolaryngoscopy. Anesth Analg. 2008 Mar;106(3):935-41, table of contents. doi: 10.1213/ane.0b013e318161769e. PMID: 18292443.
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