Dr Shah M. Rahman; Dr Dani Hall
Sedation is a spectrum of clinical effects (intentionally reducing consciousness) brought about by one or more drugs, in order to facilitate a treatment or procedure. Ketamine has a special place in sedation with its own category – ‘dissociative sedation’.
With some training, supervised practice and reflection, the art and science of sedation with ketamine can be acquired – where you can legally push drugs to kids, and give them some of the best analgesia the NHS can provide. Awesome!
By the end of this article, you should be able to:
- Describe the effects and characteristics of Ketamine
- Know the indications and contraindications of Procedural Sedation and Analgesia (PSA)
- Understand the adverse effects of Ketamine and how to respond to them
- Describe the process of running a sedation
Ketamine is a derivative of phencyclidine (‘angel dust’ for the street drug uninitiated), which has dose dependant effects ranging from analgesia and sedation to anaesthesia; the latter with a dissociative state (dissociation of the thalamo-cortical from the limbic system): effectively, separation of higher function from sensory stimuli. Ketamine is a non-competitive antagonist of the NMDA receptor, and also has some noticeable anticholinergic effects.
It comes in different strengths including: 10, 50 and 100mg/mL strengths. This is a significant potential source of error with dosing, particularly in the paediatric population, so needs careful checking when drawing up and labelling. Thankfully, it’s a Controlled Drug (CD), so the process of signing it out means the concentration is double (potentially triple) checked as doses are drawn up. There are also ‘special order’ prefilled syringes of the 10mg/mL concentration which can help if your department regularly uses ketamine.
Quick thought: What is the main colour used in the NHS for labels indicating induction/hypnotic agents (hint: ketamine is one of them, others include propofol and thiopentone)?
Administration and Dosing:
Intravenously, the analgesic dose is 0.1-0.2mg/kg, sedation 0.5-1.0mg/kg and induction of general anaesthesia in the non-shocked patient is 2mg/kg.
Particularly for PSA, the IV dose should be given over a minute, to reduce the risk of apnoea. Onset starts at around 30s (clinically noticeable with nystagmus and increased heart rate). The duration of action is 5-10 minutes (15-20 minutes if 1mg/kg is used) and the initial bolus dose can be followed with another if clinically indicated. Intramuscular use is possible more often used in adults (mainly for acute agitation). The IM doses are higher for the various intended clinical effects, as well as having a longer onset of action and variable clinical response. For these reasons, IM use is not in vogue for paediatric sedation practice.
Clinical Effects on Systems
- CVS – tachycardia and increased blood pressure, secondary to catecholamine release
- RS – preserved airway reflexes, bronchial smooth muscle relaxation, usually no reduction in respiratory drive.
- CNS – dissociative state, analgesia, nystagmus, pupil dilatation and increased cerebral blood flow and pressure
- GI – increased secretions
We’ve covered the concept of PSA and Ketamine. When would you use it?
It’s best suited to short (<20 minute) procedures where other analgesics are either unsuitable, have already been attempted or planned to be used in conjunction. For example, orthopaedic procedures including fractures requiring reduction for neurovascular injury and plaster application or analgesic purposes e.g. suturing and dressing changes or even when a patient needs to be immobile for a period of time such as foreign body removal or wound closure.
- Reasonable alternative procedure or medication e.g. LAT (Lignocaine-Adrenaline-Tetracycline) gel to anaesthetise wounds, ring blocks to anaesthetise fingers, Entonox for sedation, or, if a general anaesthetic is thought to be more appropriate
- Learning disability – dependant on the nature and degree
- Known misuse of drugs of addiction – only really applicable in adult practice, where introducing a patient to ketamine may trigger further drug seeking behaviour e.g. the recurrent shoulder dislocator who says ‘ketamine is the only thing that works…’ at triage.
- Age – check your local policy for lower age limit
- Lack of appropriate personnel or facilities
- Refusal to consent
- High risk of apnoea or laryngospasm e.g. ongoing respiratory tract infection, sleep apnoea, significant tonsillar hypertrophy. Sleep apnoea may not have been formally diagnosed yet so focused questions can help assess risk.
- Allergy/adverse reaction to proposed agents
- Reduced GCS
- CSF flow obstruction
- Cardiovascular compromise e.g. hypovolaemic shock
Less relevant for the paediatric population, but for completeness
- Severe cardiovascular disease
- Raised intraocular pressure e.g. globe injury, glaucoma
- Psychotic illnesses
Verbal consent is a given, and realistically should be written, for both the procedure as well as the sedation itself. Explain everything in terms that patients and relatives can comprehend. Ideally your trust should have a proforma for this – if it doesn’t, I spy a QUIP ahoy…
Hint: The Royal College of Emergency Medicine (RCEM) has an audit standard for sedation – the fields for this can be easily bootlegged for sedation preparation paperwork so that when it comes to audit time you can be 100% compliant!
The sedation process can be chronologically broken down, as well as split into domains of scene, self, staff, patient and family.
Quick thought: Where is your PSA checklist kept?
Sedation should be delivered in a clinical area where there are full resuscitation facilities available, practically a procedure room in the Paediatric ED or Resuscitation area. Ideally, it needs to be somewhere where lighting and environmental noise can be controlled, as well as entry e.g. door or clearly marked cubicle indicating a sedation is taking place.
The Association of Anaesthetists of Great Britain and Northern Ireland have previously published on the minimum standards of monitoring, and these are taken as the standard to safely sedate:
- Continuous Pulse Oximetry – ideally on the opposite limb to a BP cuff
- Capnography – the CO2 trend is most important, indicating adequacy of ventilation, breathing rate and early indication of apnoea; measured through either dedicated nasal cannulae or ‘capnomasks’ to an in line monitor
- Non-invasive Blood Pressure – an initial measurement, followed by a values cycling every few minutes, is a handy way of automatically generating observations.
- ECG – three lead will do
You’ll be occupied for usually thirty minutes, as the sedationist shouldn’t leave the patient until recovery is underway. Make sure other clinical staff know not to disturb you unless absolutely necessary. Inform your senior so that supervision is present – either direct, locally or offsite, as per your trust’s policy. If you haven’t done a PSA in a while, have a quick read of your local policy or guideline. Here’s an example.
At least three: Sedationist, Procedurist and an appropriately experienced Nurse or other Healthcare Professional. This is necessary for the separation of roles and concurrent activity e.g. drug administration, patient assessment, monitoring and observations, record and time keeping; in addition to the procedure itself. All three staff (and others helping or observing) need to have a collective mental model of anticipated course of events and actions on encountering any issues. As sedationist, your responsibility is the patient’s safety – so don’t be rushed to undertake anything you aren’t happy with. The initial briefing you give, as well as the checklist, will help everyone safely partake in the ketamine experience.
Individual experience of hospitals, injuries and drugs varies considerably. Part of the ‘art’ of sedation lies in preparing both patient and family for what may be their first exposure to
both Ketamine and Procedural Sedation. This really helps in relaxing the patient, addressing concerns and explaining the anticipated effects. If you have a play specialist available, their input here is invaluable.
The presence of family is usually a given in paediatric practice, however patients may present from school or sporting events, so may be worth waiting for a family member to arrive before starting. Explain to the parent what they will see. Their child is going to look spaced out, might twitch a bit, start drooling and tears form in their eyes (this is NOT crying – it is just a ketamine side effect). Some kids also make some groaning noises while they are sedated, but this does not mean they are in pain. Once properly sedated, the child may still have their eyes open which, if you don’t warn of this beforehand, can lead a parent to think their child is still awake. Consider the squeamish rating of the procedure and fainting tolerance of those around you. It may be worthwhile agreeing with family to leave after onset of sedation (in advance) so that you can focus on the task at hand.
The ‘sterile cockpit’ starts here. Simple things like ‘do not disturb – sedation in progress’ signs and having your drugs already drawn up as well as ancillaries (suction, oxygen, bag-valve-mask or anaesthetic circuit, emergency drugs) help to speed up the process.
Go through your pre-sedation checklist. Then start your bolus and timer. Use the opportunity to chinwag with the patient and/or family and put them at ease as well as continuing your clinical assessment – observing the patient’s eyes for nystagmus, a finger on the pulse (temporal works well at the head end for your inner ‘Sedation Yoda’), and noting their breathing rate and efficacy.
During this time, your colleague should be noting timings and observations from the monitor (ideally you’ll both be at a vantage point to observe it) and the procedurist will be preparing their equipment. Once happy that sedation is in effect, give the nod to go ahead, and enjoy the great feeling that comes with another happy customer.
If all is not going to plan…
- This is usually prevented with a decent period of pre-oxygenation (a non re-breathe mask giving an FiO2 of ~0.8) as well as nasal cannulae and the slow injection of ketamine with a free-running crystalloid drip helping it along on the journey (don’t forget the dead space!)
- Should it occur, aim for a breathing rate of 10-12 and/or adequate CO2 – being wary that if it’s not invasive, the figure may not be a true representation of end tidal, so the trend is more important.
- Give slow and gentle breaths with a bag-valve mask or anaesthetic circuit
Laryngospasm – remember, if the chords need a hand from you to get them open, you probably need a hand too, ask for help!
Ensure the upper respiratory tract and head is positioned for best flow, and see if pressure at the ‘laryngospasm notch’ helps.
You can then consider what the issue is whilst potentially attempting to ‘break’ the laryngospasm with increasing positive pressure (an anaesthetic circuit with a PEEP valve is your friend). If irritation, remove secretions, if incomplete sedation, consider supplementing it. If needed, use a rapid onset muscle relaxant e.g. suxamethonium, but be really wary of bradycardia (given the risk of hypoxia already ensuing) and the need for more help – if you haven’t asked for it already!
Bradycardia – this can either be tackled prophylactically or reactively. Anticholinergics such as glycopyrronium (4-10mcg/kg IV) and atropine (20mcg/kg IV, minimum dose 100mcg) should be drawn up in advance, but remember to consider the underlying cause of the bradycardia rather than just treating the number on the screen.
Nausea and Vomiting – consider using Ondansetron 0.1mg/kg IV. For a more detailed review of ondansetron in ketamine sedation, check out this BestBET.
Emergence Phenomenon (inc. hallucinations and delirium) – this can be a difficult and potentially upsetting time for a patient, but is influenced by pre-sedation state of mind, suggestion and atmospherics. This, combined with calm and reassuring words help with the Special K experience! Remember, the patient’s perception of time may be distorted, so regular reassurance will help. If patients have emergence phenomenon despite your preparations, don’t despair; consider using midazolam.
Recovery – after the drugs have done their thing, you need to ensure offset has begun, and that you are able to safely leave the patient’s immediate vicinity. This usually means that their airway and breathing is self-supported, that the dissociative effects have worn off and that they have returned to a more responsive state. Their verbal GCS score may still be a 3 or 4, but you need to be confident they are on a positive trajectory away from the effects of the good stuff. Ketamine has a predictable profile when given IV so you’re unlikely to get into issues once the effects have started to wear off.
Aftercare and Information If going home from ED, the patient and family should be reminded about what to expect. Give them an information leaflet (and run through it verbally too) noting the need to have supervision and to avoid safety critical tasks in the next few hours. This is especially important if you’ve been extra generous with a helping of benzodiazepines.
Notes and Reflection – make sure your notes are complete. Get someone to witness and sign off the CD’s being disposed of. Pop a note in your logbook and pat yourself on the back on a job well done! Make sure that as a junior, you’re using a logbook to help document your progression in sedation experience – consider the use of a ‘Procedural Passport’ locally or ensure PSA is discussed at supervisor meetings so that your progress can be formally documented.
Shah M. Rahman, Registrar in Emergency Medicine, Wexham Park Hospital; Dani Hall, Consultant in Paediatric Emergency Medicine, Evelina London Children’s Hospital