The most useful part of an RSI is that it is a method of achieving a state of very quick unresponsiveness and paralysis to facilitate a fast and effective means to control an emergency airway.
Therefore the indications for RSI can be divided into reasons to achieve intubation quickly:
- Dynamically deteriorating clinical situation, eg. uncontrolled haemorrhagic shock
- Non-cooperative patient
- Severe hypoxia
- Severe ventilatory failure eg. life threatening asthma
- Extremely short safe apnea times eg. very high BMI, or a patient whose respiratory rate is 60+ whilst trying to compensate for a severe metabolic acidosis. Removing the respiratory compensation in this sort of scenario can be very dangerous.
And reasons to achieve intubation quickly whilst also avoiding regurgitation:
- Full stomach (increased risk of regurgitation, vomiting, aspiration)
- Secretions, blood, vomitus, and distorted anatomy around the airway eg. trauma or burns
- Any abdominal pathology leading to increased intraabdominal pressure, eg. bowel obstruction
- Pregnancy (after 1st trimester, although some textbooks would say any pregnant patient should have an RSI)
Should I do an RSI? A pro-con list
Think about your backup plan for these scenarios. Always call for help if you encounter these, but it is useful to have an idea of what the problem is and what needs to be done to achieve it. Best to think through it now than when you are in the situation.
Problem: Patient becomes very hypoxic immediately after induction (often before the paralysis has time to work)
Risk factors for this: High BMI, preexisting hypoxia, pregnancy, airway obstruction eg. with blood
Prevention: Consider how you will preoxygenate the patient – THRIVE/good seal on face mask, and consider when to start ventilating the patient – oxygen saturations often tell you what happened 10 seconds ago! and whether the RSI technique can be modified or whether it is required at all
Possible solutions: Face mask ventilation +/- guedel but watch for regurgitation and gastric insufflation, suction if you can see debris in airway. If difficult to ventilate, see next heading.
Unanticipated difficult ventilation (often in the setting of hypoxia after induction)
Problem: Patient is unexpectedly difficult to ventilate, and you would have started to try to ventilate usually because the patient had become hypoxic.
Risk factors for this: Inadequate pre-op assessment, inadequate muscle relaxation, high BMI, beard, NG tube or other tubes that cause leak around the face, facial trauma, neck trauma etc
Prevention: Good preoxygenation – never skimp on the 3-5 minutes. Have all your equipment ready and brief your assistant that you might need to ventilate and if this is difficult then please pass you a guedel/SGA as required.
Possible solutions: Use 2 handed mask ventilation with oral adjuncts, ensure adequately paralysed and sedated, consider supraglottic airway, and consider intubating.
Problem: Patient is coughing or in partial laryngospasm when you attempt to instrument their airway
Risk factors for this: Wrong estimation of body weight (more common in high BMI patients) and therefore inadequate drug given, cannula not patent or drug is sitting in the extension line of the cannula and not in the patient!
Prevention: Try to find out exactly what the patients’ body weight is to help plan your drug calculation, avoid inducing anaesthesia through the cannula extension lines – the author often removes these and connects fluids that are rapidly flowing to avoid this exact scenario. Flush whichever cannula port you’ve used for induction after the muscle relaxant even if you have fluids running. If there is doubt about the cannula patency, put one in yourself that you know is working before starting. You won’t regret it!
Possible solutions: Give more drug and flush the cannula (you may need to use a different drug if you have used suxamethonium previously). Ensure patient is adequately sedated (more propofol) as you will now have to wait another minute. You may already have intubated at this point despite the small cough, in which case ensure that you check the tube position because the patient may have coughed it out of position – and ensure you have adequate sedation.
Problem: Patient regurgitates stomach content/blood/debris into their airway
Risk factors for this: Pathology giving rise to gastroparesis or raised intraabdominal pressure eg. bowel obstruction, a lot of morphine use, hiatus hernia, variceal bleeding; pregnancy; unfasted patient eg. trauma/emergency theatre
Prevention: Make sure suction is ready under the pillow (and connected to the bottle which is connected to the wall and is on max and working) and tilt trolley is available. In pregnancy, sodium citrate can be given to the patient before going to sleep (it is a nasty tasting drink but the idea is that it neutralises the acidity of the stomach content to reduce chemical damage in the event of aspiration). Premedication with ranitidine can sometimes help those patients with gastrooesophageal reflux or hiatus hernia. If there is an NGT in situ or Ryles tube, aspirate this before starting induction – you may get a surprise 500ml of stomach content out even though it has been in free drainage.
Possible solutions: Suction visible debris, tilt table so patient is head down, left lateral position can help occasionally. Maintain oxygenation – it will be messy but don’t lose focus. Keep cricoid on if possible but if you are worried that it is doing more harm than good then you can instruct cricoid to come off once in head down position. If large solid debris in airway then you can use a Magills forceps to take this out. Intubate when it is safe to do so and ensure you have adequate cuff pressure. You can clean the patient (and yourselves!) once you have safely achieved a protected airway.
Problem: RSI takes longer than anticipated for whatever reason and patient does not have adequate sedation. Risk of awareness – the NAP 5 audit showed the below graph – RSI was used in 36% of the accidental awareness under GA cases in the report, and was over-represented as a component of anaesthesia.
Risk factors for this: Inadequate calculation of induction dose needed, or giving less because you are worried about blood pressure in sick patients, cannula not patent or drug sitting in the extension lines, lack of familiarity of using technique (eg if you are using thiopentone + suxamethonium, no opioids to induce for the RSI when you usually use fentanyl as a co-induction agent, you are likely to underestimate how much propofol is required), prolonged RSI for whatever reason (eg. hypoxia requiring ventilation, regurgitation, difficult intubation etc)
Prevention: Cannula precautions are easy to do (remove the extensions, ensure it is patent, put a new one in if necessary, attach to fast flowing fluids), weight based calculation of induction drug with more easily available (an extra vial of propofol in your drug tray is always a good idea), and then consider some bigger questions (these are suggested by NAP 5):
- Would administration of opioids (or other adjuncts) lower the risk of awareness under general anaesthesia (AAGA) while still achieving the goals of RSI?
- Is there time to assess the effect of induction agent, and provide more if needed?
- Can the administration of the rapidly acting neuromuscular blocking drug be delayed slightly to check conscious level (and/or even check the ease of bag-mask ventilation, itself a test of depth of anaesthesia)?
- Does thiopental have a place in modern anaesthetic practice, and what is that place?
- I would also add: consider using drugs that are familiar to you, eg. if you have never used thiopentone before, and you are by yourself with an unwell patient, should you be using this agent in this scenario?
Possible solutions: Ensure you have cycling blood pressure and you may need to give more agent than is required as top ups if the RSI is taking longer – but you may need to give metaraminol or ephedrine immediately after each bolus of agent to preserve blood pressure. Remember that transitioning from intravenous induction to inhalational maintenance is one of the other highlighted areas for risk of accidental awareness – once you have turned on the sevoflurane, make sure you have reasonable levels of sevoflurane in the patient before disconnecting and transferring into the operating theatre.
unanticipated Difficult intubation
Problem: Intubation may be unexpectedly difficult and you have given the patient a high dose of muscle relaxant and you may not know if the patient can be ventilated.
Risk factors for this: Inadequate pre-operative assessment, high BMI, obstructed airway (regurgitation, trauma, bleeding)
Prevention: The NAP 4 study on complications of airway management demonstrated that poor airway assessment, failure to plan for failure, and trying to solve difficult intubation by repeatedly trying to intubate were the most common causes of problems intubating. Thus it follows that good airway assessment, knowing the DAS guidelines (below) and having equipment ready in case things don’t go to plan can help prevent a bad situation. Consider awake fiberoptic techniques and if you are very worried about the airway, ask for help and consider how much this patient requires an RSI versus how likely it is that a difficult airway situation may arise.
Possible solutions: Follow local procedures and the DAS guidelines for unanticipated difficult tracheal intubation. Supraglottic airways can be a life saver. Know where your front of neck access kit is.
The Life in the fast lane page for RSI is good and has some mnemonics you can use to help remember what you need to prepare.