Rapid Sequence Induction ======================== þ Quick and Dirty RSI, Keith's Airway Card text: þ Intubation options, if have time: - lidocaine 1.5 mg/kg + blunts reflexes that cause increased ICP, but of questionable significance + also reputedly blunts cardiovascular effects of intubation, again questionable clinical significance See also: - atropine 0.5-1 mg + decreases secretions + decreases vagal stimuli and decreased HR, especially in kids/infants + ALWAYS use if kids less than age 6 - topical neosynephrine/lidocaine + for nasal intubation + or cocaine 4% þ Paralysis Options: þ Sedation options: - Versed (midazolam) + slow onset, intermediate in duration - Thiopental (Pentothal) + has an excellent cerebral protective effect + is a cardiovasular depressant; drops BP so avoid in multiple trauma - Ketamine (Ketalar): + increases BP, so no good with head injury, CVA, SAH ruptured eye globe, but OK in trauma - Fentanyl (Sublimaze): can be used as a single agent for both sedation and paralysis in large doses, but when given in large fast doses, can cause spasm of the chest muscles unresponsive to Narcan; blunts increased ICP effect of intubation - etomidate: works similarly to barbiturates such as thiopental, also drops BP so contraindicated in multiple trauma patients þ Nice email summary of RSI Date sent: Fri, 5 Mar 1999 13:15:07 +1030 Send reply to: "EMED-L -- a list for emergency medicine." From: Derek Louey Subject: Re: EI not RSI To: EMED-L@ITSSRV1.UCSF.EDU I have been lurking with great interest regarding the discussion on rapid sequence induction (RSI). I am not quite sure where the true argument lies, although I do appreciate that we do not always adhere to the standard concept of a RSI in the Emergency Department (ED). Here RSI can be simply defined as essentially preoxygenation, rapid bolus thiopentone, rapid bolus suxamethonium (scoline), cricoid pressure on, keep mask on without manual ventilation, wait for fasciculation, orally intubate. (I have deliberately omitted adjunts such as lignocaine, defasciculating doses of non-depolarising agents etc. which I do not believe is part of the usual formula). In constrast, the other major form of intravenous induction is elective induction which involves IV anaesthetic agent (e.g. thiopentone, propofol), non-depolarising muscle relaxant, bag-mask ventilation, wait for relaxation, intubate. As a purist, I believe there is only one definition of RSI regardless of the geographical location it is practised.. Therefore, any differences practised whether in the pre-hospital scenario, ED or OT should not be labelled as RSI. Furthermore, although there is a distinct difference between the meaning of 'induction' and 'intubation', performing a RSI usually implies that the airway will be secured by oral endotracheal intubation. As a consequence, there should be no difference in the application of RSI per se between the OT and ED. Having said this, there are definite variations to RSI which are employed in the ED. However, these techniques are not only solely practiced in that setting. In Australia, anaesthetists and intensivists still participate in the trauma team and ward arrest ('code','crash') team. They would similarly modify their approach to induction for critically ill patients. These include unstable patients preparing for emergency surgery, patients on high dependency/intensive care units and acutely unwell patients who have deteriorated on general wards. Perhaps in the United States the system differs, where these other specialties are not exposed to these particular problems. In which case, there may something said about Emergency Physicians (who frequently are confronted with these issues) refining and developing these alternative techniques. The standard recipe for RSI is based on the best use of current pharmacological knowledge to achieve a particular goal. It has its particular indications but also has distinct disadvantages. Therefore, the concept of RSI is dynamically evolving in response to pharmacological advances. Nevertheless, despite the development of new induction agents, muscle relaxants and other adjuncts, no other combination of drugs have clearly demonstrated to be definitely superior to the method I have described. As a result, there has not been any reason to modify the existing formula for routine anaesthetic practice. Other methods to allow intubation that may be considered within the ED setting include: * 'Cold' intubation - without the benefit of medications, often done in the field, in arrested or obtunded patients * Gaseous induction - uses inhalational anaesthetic agent, useful for partial upper airway obstruction e.g.epiglottiis; allows for spontaneous ventilation * Awake intubation with or without sedation - preserves ventilation, includes a variety of techniques - local anaethesia to airway, fibre-optic intubation, blind nasal intubation etc. The ideal induction should have these characteristics: * obtundation of airway reflexes to allow direct laryngoscopy and intubation (technically this is the only requirement and can be achieved solely with a muscle relaxant) * produce amnesia and remove awareness * reduce the sympathetic response to intubation (which may be detrimental in those with diseased myocardium) * prevent abnormal rises in intracranial pressure (which may be detrimental in those with intracranial pathology e.g. head injuries) * minimal side effects - no prolonged apnoea, cardiovascular stability, prevent aspiration The indications for RSI are: * achieving intubating conditions so that the airway and/or ventilation can be rapidly secured * preventing vomiting and aspiration in high risk patients e.g. unfasted, obese, acute abdomen * minimising the time of maintaining a potentially difficult airway by bag-mask ventilation Therefore, an ideal RSI should also have these qualities: * rapid onset and offset * minimizing risk of aspiration At present there is no single drug or combination of drugs that can achieve all of the above goals. Under ideal conditions standard RSI achieves these aims in the following ways: * preoxygenation reduces the need for assisted ventilation during apnoea * thiopentone has a rapid onset (arm-brain circulation time = 20s) * suxamethonium has a rapid onset (30s) * thiopentone reliably produces amnesia and loss of awareness * suxamethonium completely obliterates airway reflexes * cricoid pressure and avoidance of manual ventilation prevents gastric insufflation and risk of aspiration * thiopentone has rapid offset * suxamethonium has a rapid offset (5 min) The criticisms of RSI are: * preoxygenation may not prevent the need for assisted ventilation if the patient has impaired pulmonary function or is hypermetabolic * thiopentone in standard doses can cause hypotension which is exacerbated in shocked patients * suxamethonium increases intragastric pressure and intracranial pressure and can produce bradycardia and bronchospasm * suxamethonium may cause a dangerous rise in serum potassium * thiopentone and suxamethonium still can cause apnoea for a sufficient duration of time that manual ventilation may be required * thiopentone does not completely obliterate the sympathetic response to intubation or prevent rises in intracranial pressure Furthermore, there are certain problems more commonly seen in the ED compared to elective surgical patients. These include: * acute airways obstruction - e.g. epiglottitis, foreign body, * acute respiratory failure - e.g. asthma, chronic airways disease * acute circulatory failure - e.g. unstable arrhythmias, cardiogenic shock, hypovolaemia * acute raised intracranial pressure - e.g. subarachnoid haemorrhage, meningitis * acute trauma - e.g. hypotension, head injuries, oral maxillofacial trauma * unfasted state * inadequate time to perform a careful assessment of a potentially difficult airway These may have the following implications: * awareness issues may have to sacrificed if airway and ventilation needs to be immediately secured * the cardiovascular status of the patient may not tolerate standard doses of induction drugs * there may not be the luxury of time to stabilise the patient and induce the patient prior to intubation * the onset of action of all medications are significantly reduced in circulatory failure * the induction sequence may precipitate transtentorial herniation * most patients should be considered to be at high risk of aspiration In response to these problems, variations on the RSI theme have been proposed and employed. Nevertheless, each of these have their own distinct advantages and disadvantages. ALTER INDUCTION AGENT Propofol * Pros - obtunds airway reflexes better than thiopentone * Cons - cause more hypotension, slightly slower onset than thiopentone, causes apnoea Midazolam * Pros - more cardiovasculary stable, produces amnesia, less respiratory depression * Cons - incompletely reduces awareness Ketamine * Pros - more cardiovascularly stable, does not cause apnoea, bronchodilator * Cons - increases intracranial pressure, emergence phenomena Etomidate * Pros - dose not cause rise in intracranial pressure, more cardiovascularly stable * Cons - not widely available, (the concerns about adrenal insufficiency and death when used for long term sedation has caused it to be banned here in Australia and other countries) Rapidly acting opiates e.g. alfentanil * Pros - rapid onset, obliterates sympathetic response to intubation, rapid offset, more cardiovascularly stable * Cons - produces apnoea, may cause hypotension, may not produce amnesia or loss of awareness (NB fentanil has slower onset, produces prolonged apnoea at doses to obliterate sympathetic response to intubation) Gaseous induction * Pros - less likely to cause prolonged apnoea, spontaneously ventilating patient * Cons - slow onset (excepts perhaps sevoflurane), causes hypotension, excitement phase, higher risk of aspiration ALTER MUSCLE RELAXANT Pretreatment with non-depolarising muscle relaxant * Pros - prevent rise in intracranial pressure or gastric pressure due to suxamethounium without altering the speed of onset and duration of suxamethonium * Cons - need to allow a few minutes before suxamethonium is administered, may cause hypoventilation and weakness in the interim Rapidly acting non-depolarising muscle relaxant e.g. rocuronium * Pros - rapid intubating conditions at high doses, no rise in ICP or gastric pressure * Cons - prolonged duration ADJUNCTS TO REDUCE SYMPATHETHIC RESPONSE TO INTUBATION OR PREVENT RISE IN INTRACRANIAL PRESSURE High dose opiates: * Pros: rapid onset and offset (only with alfentanil, sufentanil) * Cons: prolonged apnoea (if fentanyl or morphine used), may be hypotensive Rapidly acting beta blockers e.g. esmolol * Pros: rapid onset and offset * Cons: bronchospasm, hypotension, bradycardia, heart block Lignocaine * Cons: arrhythmogenic, delayed onset of action Taking all of this into account, if I need to intubate somebody my practice in most circumstances I would use a classical RSI with alfentanil/fentanyl with the following variations: * Partial airways obstruction - gaseous induction OR awake intubation OR classical RSI (with cricothryroidotomy tray at hand) * Acute asthma - ketamine, suxamethonium OR high dose rocuronium * Chronic airways disease (pre-arrest) - classical RSI OR awake intubation * Hypotensive patients - low dose thiopentone OR midazolam +/- alfentanil/fentanyl, suxamethonium * Obtundation secondary to circulatory failure - midazolam +/- alfentanil/fentanyl +/- suxamethonium * Coma (raised ICP) - alfentanil/fentanyl, wait, low dose thiopentone or midazolam, suxamethonium OR high dose rocuronium * Coma (normal ICP) - low dose thiopentone, suxamethonium * Cardio-respiratory arrest - cold intubation In conclusion, although a classical RSI is not always performed in the ED, in Australia the variations outlined are not the sole domain of Emergency Physicians but are actually part of the repertoire of techniques employed by all those involved in critical care. Finally, the appropriateness of who and how intubation should be performed should involve a careful risk:benefit analysis to the patient and not related to 'turf wars' between groups competing for the procedure. This involves a complex interaction between the operators knowledge, experience and technical skill; and the geographical location in which he practises - the difficulties and restriction it places on him, and the resources available. Personally, despite successfully performing over 1000 intubations as a trainee, I recognise that complications can and do occur with possibly disastrous consequences. I recall my superiors telling me about an unfortunate case they were involved in, in which a patient required emergency intubation - as the suxamethonium was administered, one consultant remarked whilst she was applying cricoid pressure, 'Hey , X isn't that a tracheostomy scar?!'. (The patient finally required fibreoptic intubation by an anaesthetist despite several attempts by Emergency physicians and senior anaesthetists). It also illustrates the point that in the ED setting there may also be less time to perform an adequate assessment for a potentially difficult airway. Therefore, one should always provide for a suitable back up plan particularly for the dreaded scenario of 'CVCI' (cannot ventilate, cannot intubate). Derek Louey Advanced Trainee in Emergency Medicine South Australia AUSTRALIA