Upcoming SMACC Talk 2016
"DAS GUIDELINES EXPLAINED" will be delivered by Dr. Ellen O’Sullivan

The Difficult Airway Society is a UK-based medical specialist society formed to further management of the airway of patients by anaesthetists and other critical care practitioners.

It publishes updated guidelines on the management of difficult airways, of interest are fiberoptic intubations, the main algorithm in adults and in paediatrics. 

A full list of the guidelines for INTUBATION, EXTUBATION, PAEDS & OBSTETRIC patients - click here.

My infogram based on the DAS 2015 Guidelines is seen below. 

I am looking forward to Dr. O'Sullivan's session to explore the guidelines and how they relate to clinical practice.

Upcoming SMACC Talk in 2016
"SO YOU THINK YOU’RE A RESUSCITATIONIST…?" will be delivered by Dr. Victoria Brazil

Well - I think we are about to find out if we are or not! 

A simple definition of resuscitation might be: to bring (someone who is unconscious, not breathing, or close to death) back to a conscious or active state again (Merriam-Webster Dictionary)

I think we can all identify with this simple definition - but in this modern age, the term is breathed freely into a lot of aspects of emergency medicine, anaesthetics, intensive care and acute medicine and even beyond.

'Resuscitationist' is a term that has garnered a lot of chat recently. People refer to themselves as 'avowed' resuscitationists, learners of resuscitation or imply that it is part of their work on a daily or frequent basis. It certainly gathers a lot of kudos and frequently conjures images of 'sexy medicine', adrenaline fuelled CPR, central lines, resuscitative thoracotomies, chest drains and scalpels. Given the amount of people we routinely 'resuscitate' to prevent further system collapse or arrest, for example, early-on in Sepsis - this is clearly not always the case.

So, who or what is a Resuscitationist? Perhaps that is what Dr Brazil partially seeks to answer. It is likely that everyone involved with sick people is a resuscitations to some degree and has a role to play in being a life saver.

In our minds however, it most frequently it includes those involved in dealing with trauma patients, cardiac arrest, respiratory arrest, airway disasters, massive haemorrhage, traumatic brain injuries, nursing, paramedicine, 'resus' room in the ED, ICU, theatre patients who are very sick, laparotomies, pre-surgical resuscitation and much more.

It also implies a lot of team work and interaction - which another SMACC talk seeks to address also.

I think this is going to prove to be an excellent talk and provide excellent discussion points. Dr Brazil is a wonderful speaker. Many of us feel we are directly connected to a field of resuscitation, so there ought to be learning points for everyone.

Things to probably bear in mind with resuscitation in general are (not necessarily in order):
1. Team work
2. Skill set (Senior Team vs Junior Team vs Skills)
3. Training/Education Opportunities (courses/FOAMed etc)
4. Location (ED/ICU/Theatre/Wards/OOH etc)
5. Mindset of the team leader and members
6. What investigations are commonly needed/done?
7. Procedures to be done?
8. What are we seeking to achieve?
9. Appropriateness of actions (DNAR/Condition/Trauma)
10. Destination (What is happening to the patient and where are they going? Scans etc.)

RESOURCES:
EMCrit does a good Podcast on 'The Mind of a Resuscitationist' - about how we agonise over difficult decisions (with Dr. Cliff Reid)

Obviously, resuscitation involves elements of Advanced Life Support, BLS, APLS etc. (Click Here)

There are many Trauma Courses that offer training in advanced techniques. An excellent resource with FOAM-based material is the ATACC course - with a free manual (Click Here)

It is a wide misconception that #FOAMed is just for people interested in emergency and prehospital medicine. It is true that large areas of the movement are dedicated to those specialties, but there is a vast amount of other specialties that use #FOAMed to broadcast, discuss and develop ideas and improve their skills.

This guide is for all of you out there who want a bit of a helping steer towards discovering the #FOAMed movement for yourself. Maybe you wish to get involved in the 24h news cycle of your specialty, or perhaps you wish to contribute. In 2016, it could’t be easier.

1. It’s free.
2. It’s easy to use.
3. It’s the future of medical education

How to get started

1. Gettwitter. Sign up for a free account and use the #FOAMed tag to discover people to follow.
2. Get twitter on your phone. You’ll see updates from those you follow about your specialty.
3. Create a list (bookmarks) of your favourite blogs or websites that utilise #FOAMed.
4. Try to google #FOAMed and your specialty to see the results.
5. Use LinksMedicus website to find your specialty’s #FOAMed pages as well as other amazing links!
6. Involve yourself in conversations using the #FOAMed hashtag on twitter
7. Start conversations about anything medical using the #FOAMed hashtag and maybe #radiology for example
8. Invite colleagues to do the same - friendly faces with lots to add.
9. Put your presentations online using SlideShare or similar, it’s free. You can link to it on Twitter!
10. If you have lots of material or presentations, start a free blog on WordPress or similar and put it online!

Here are some more #FOAMed Search Tools
1. Google FOAM 
​2. FOAM for GP 
3. LITFL - Top Blog List
4. EM and CC Entire Blog List

Welcome to all of you coming from the #WeNurses 'Prevention of Dehydration' Discussion on 21/4/16

#WeNurses have put together a great summary here.

Hypovolaemia/dehydration can lead to serious problems across all patient groups - community and hospital.

Dehydration can lead to acute kidney injury, high sodium levels, brain swelling, seizures, hypotension and can be fatal.

Below are some resources I have gathered for us to have a look at to help our discussions this evening.

Click on the links below to view the content:
Nursing Times Article on Recognition & Prevention
​Nursing Times - Why is Dehydration Still A Problem?
Prevention of Dehydration - Mayo Clinic
Dehydration Clinical Presentation - How do they look?
Help Elderly People Avoid Dehydration
Identify & Prevent in Elderly People in Long Term Care
​Rehydration Project
NHS Choices - Preventing Dehydration

Introduction to IV fluids for medical students
IV Fluids Tutorial 
World Kidney Day - ABCD AKI Checklist
Assessing Dehydration & Shock in Children
Paediatric Dehydration Assessment

If you have any clinical questions about IV fluid management - you can tweet to me @Gas_Craic

ATLS is getting on a  bit in years. Viewed by some to be biased toward a surgical viewpoint and orientated around an US Trauma Team system, the ATACC course was pioneered by the #FOAMed community at large and a course is available from the team in Liverpool. It's 9 years old and the manual is already in its 6th edition - updated yearly.

They have produced a phenomenal, FREE, manual to rival the ATLS approach and is considered by many to be a much more pragmatic and up-to-date course. Trauma care is rapidly advancing and changing in many ways, so take a look at ATACC. It is accredited by the Royal College of Surgeons, London.

I have attached the ATACC manual below in low-definition, there is a HD link below (large file)

ATACC Website
​High Definition Manual here (105mb)

(A quick search on SlideShare, I'm sure, will show you an ATLS manual in its current form - Copyright ACS)

 iEThe wonderful Barbara Stanley FRCA (@TheNeuroSim) is a popular figure on Twitter and a neuroanaesthetist in England. Her team convene excellent courses in high fidelity scenarios involving neurocritical patients via www.theneurosim.com

She has kindly provided a wonderful list of #FOAMed presentations on aspects of neurocritical care and considerations in neuroanaesthesia. 

We are teaming up to bring #FOAMed a number of infograms on head injury management in anaesthesia and ICU - so keep a look out!

Ketamine, Collars, Evidence Controversies and an International Dialogue on Traumatic Brain Injury
Intracranial Haemorrhage
Monitoring the Injured Brain
The Difficult Airway
Transfer of the Head Injured Patient

Some other topics:
​Ethical Case Studies in ICU
The Problem with Evidence Based Medicine
Education and the use of Social Media
Preparing for Consultant Interview

From Life in The Fast Lane 

Reviewed and revised 10 January 2016
OVERVIEW
Apnoeic oxygenation is used to extend the ‘safe apnoea time’ beyond that which can be achieved by preoxygenation alone

• Apnoeic oxygenation is merely an adjunct, it is not a substitute for effective preoxygenation
• Apnoeic oxygenation is most commonly provided using nasal cannulae in addition to a face mask
  
  

SAFE APNOEA TIME
Safe apnoea time is the duration of time until critical arterial desaturation (SaO2 88% to 90%) occurs following cessation of breathing/ventilation

• an alternative term in use is duration of apnoea without desaturation (DAWD)
• SaO2 88% to 90% marks the upper inflection point on the oxygen-haemoglobin dissociation curve beyond which further decreases in PaO2 leads to a rapid decline in SaO2 (~ 30% every minute)
• In a healthy preoxygenated patient the safe apnea time can be up to 8 or 9 minutes, compared to ~1 min if they were breathing room air
• In critically ill patients critical desaturation can occur almost immediately despite optimal attempts at preoxygenation
  
  

Factors that decrease safe apnoea time include:

• inadequate preoxygenation
• airway occlusion (see below)
• pulmonary shunt
• increased oxygen consumption (VO2) (e.g. high metabolic rate, fasciculations from suxamethonium)
• critical illness
• obesity
• pregnancy
• small children

In patients who develop airway occlusion, desaturation will occur more rapidly due to loss of functional residual capacity (FRC)

• FRC usually decreases by 200-250 mL during the first minute after airway occlusion in a healthy adult patient
• This occurs due to resorption atelectasis as oxygen transfers from the lungs into the pulmonary circulation
• Pulmonary shunting (blood flow to the non-oxygenated, collapsed lung units) can now occur resulting in much more rapid desaturation than otherwise predicted — even when effective preoxygenation is performed
  ​
  

PHYSIOLOGY OF APNOEIC OXYGENATION
Alveoli will continue to take up oxygen even without diaphragmatic movements or lung expansion

• In a healthy apnoeic patient, ~200-250 mL/min oxygen will move from the alveoli into the bloodstream
• Only ~8-20 mL/min of carbon dioxide moves into the alveoli during apnea, with the remainder being buffered in the bloodstream given the high water solubility of CO2
• This causes the net pressure in the alveoli to become subatmospheric, generating a mass flow of gas from pharynx to alveoli

In healthy people under ideal circumstances, PaO2 can be maintained at >100 mm Hg for up to 100 minutes without a single breath, although the lack of ventilation will eventually cause marked hypercapnia and significant acidosis

• this assumes effective preoxygenation, ongoing provision of high flow oxygen and maintenance of a patent airway

Nasal cannulae can be used for apnoeic oxygenation because the pharynx fills with high FiO2 gas and functions as an oxygen reservoir, even when the mouth is open (a patent airway must be maintained!)
PROCEDURE

• ensure patient is preoxygenated with nasal cannula in situ (15 L/min oxygen flow rate) (see Preoxygenation)
• administer induction agent
• maintain the nasal cannula flow rate to 15 L/min and adminster oxygen via non-rebreather mask or BVM as well
• If SpO2 <95% consider apneic oxygenation with positive pressure
  • CPAP or with BVM with PEEP valve with coexistent administration of oxygen at 15 L/min via nasal cannulae
  • alternatively, abandon apnoeic oxygenation and provide 6 gentle ventilations/minute (<15cmH20) if the risk:benefit of apnoea is unfavourable)
• maintain a patent airway until the time of intubation using:
  • 2-handed face-mask technique with jaw thrust
  • nasopharnygeal airway(s)
  • oropharyngeal airway
• remove the mask at the time of intubation, but continue to oxygenate via the nasal cannulae
  • this has been termed “NO DESAT” (nasal oxygen during efforts securing a tube) by Rich Levitan

EVIDENCE
Tracheal oxygenation

• Half a dozen observational studies with small numbers of patients showing that safe apnoea times can be prolonged up to 55 minutes with apnoeic oxygenation provided by tracheal catheters or equivalent devices
• This technique is widely used in ICU patients during the apnea test for brain death
• More recently Rudlof and Hohenhorst (2013) found that apnoeic oxygenation via a tracheal catheter was well tolerated during ENT procedures for up to 45 minutes in over 40 patients. Exceptions were 2 patients where the technique was not performed correctly and 1 obese pateint who could not be adequately oxygenated

Additional studies of apnoeic oxygenation using nasal cannulae are described below.
FELLOW trial, 2015

• Single-centre, randomised controlled trial
  • Allocation concealment, treating clinicians non-blinded
  • Data collection was by independent observers unaware of the study design
  • intention to treat analysis
• Population
  • n=150 Medical ICU patients at Vanderbilt 18+ years old intubated by a pulmonary and critical care medicine fellow
  •  Additional 46 were excluded
    • 23 required intubation too urgently, 18 were felt to require video or FO intubation, 1 was felt to require direct laryngoscopy, 1 was felt to require apneic oxygenation, 3 excluded for unknown reasons.
• Intervention/ Comparison
  • apneic oxygenation (n=73)
  • usual care (n=73)
  • patients were also randomised to video laryngoscopy or directed laryngoscopy
• Outcomes (apox vs usual care)
  • No statistically significant difference in:
    • Median lowest arterial oxygen saturation: 92% vs  90% (95% CI 1.6 – 7.5%; p = 0.16)
    • Incidence of oxygen saturation <90%: 44.7% vs 47.2% (p = 0.87)
    • Incidence of oxygen saturation <80%: 15.8% vs 25.0% (p = 0.22)
    • Incidence of decrease in oxygen saturation >3%: 53.9% vs 55.6% (p = 0.87)
    •  duration of mechanical ventilation, ICU length of stay, and in-hospital mortality
• Commentary and criticisms:
  • Study design
    • Pragmatic design with other treatments left to treating physicians
    • had 80% power to detect a mean lowest arterial oxygen saturation difference of 4.6%
    • Lack of blinding (could not be avoided)
  • High likelihood of selection bias due to difficult airways/ sicker patients being excluded from the trial:
    • patients deemed to benefit from a particular strategy (e.g. suspected difficult airways or prolonged intubation times – the precise patients expected to benefit from apnoeic oxygenation)
    • true emergencies and could not be randomised were excluded
    • 75% of intubations were rated “easy” – these patients are unlikely to benefit from apnoeic oxygenation
  • Lack of external validity
    • Most patients in both arms were not truly apnoeic prior to laryngoscopy
      • 73% of patients received either BVM or NIV up until laryngoscopy
      • this is a critical flaw – these patients clearly will not benefit ‘apnoeic oxygenation’ as they are being ventilated!
    • Airway patency must be strictly maintained during apnoeic oxygenation for it to work, specific measures on how to achieve this was not part of the protocol and data on airway patency is not provided for the ~2/3 patients who were not receiving NI
    • May not be generalisable outside of PulmCCM Fellow led medical ICUs (patient and skill mix)
    • A study powered to detect differences in reaching critical desaturation, rather than absolute difference on SpO2, may be more clinically relevant
• Conclusion
  • This study found no benefit or harm with using nasal cannulae for apnoeic oxygenation in medical ICU patients requiring intubation. Apnoeic oxygenation is only likely to benefit patients with difficult airways and prolonged intubation times who are truly apnoeic prior to intubation. These patients were under-represented in this study which greatly limits it’s external validity.

Dyett et al, 2015

• prospective observational study of intubations outside of the operating theatre
• no episodes of hypoxaemia in the 31 patients that used apnoeic oxygenation with nasal prongs, whereas 10 of 60 patients that did not have apnoeic oxygenation developed hypoxaemia
• The calculated NNT for apnoeic oxygenation is 6
• There may be important confounders, given the observational design of this study

Wimalesena et al, 2015

• Retrospective analysis of 9,901 NSW HEMS missions
• 728 rapid sequence intubations (310 pre- and 418 postapneic oxygenation)
• introduction of apneic oxygenation (with nasal prongs) was followed by a decrease in desaturation rates from 22.6% to 16.5% (ARR=6.1%; 95% CI 0.2% to 11.2%)
• Subject to multiple confounders due to retrospective study design

THRIVE, 2014

• 25 patients who underwent general anaesthesia for hypopharyngeal or laryngotracheal surgery; included 12 obese patients and 9 patients were stridulous
• patients had “Transnasal Humidified Rapid-Insufflation Ventilatory Exchange”: continuous delivery of transnasal high-flow humidified oxygen, initially to provide pre-oxygenation, and continuing as post-oxygenation during IV induction of anaesthesia and neuromuscular blockade until a definitive airway was secured. Airway was kept open with jaw thrust
• The median apnoea time was 14 (5-65) min, no patient experienced arterial desaturation < 90%

Ramachandran et al, 2010

• RCT of obese operative patients, n=30
• Nasal cannula attached to 5 L/min 100% FiO2 versus room air
• Apnoeic oxygenation group had significant prolongation of SpO2 ≥95% time (5.29 versus 3.49 min), a significant increase in patients with SpO2≥95% at the 6-min mark (8 patients versus 1 patient), and significantly higher minimum SpO2 (94.3% versus 87.7%)
• not blinded

Taha et al, 2006

• RCT, n=30
• Nasal catheters attached to 5L/min of 100% FiO2 versus room air
• No desaturation during the course of the 6-min predetermined stopping point in patients receiving apnoeic oxygenation, whereas the control group desaturated to the study cutoff of 95% in an average of 3.65 min
• not blinded

Teller et al, 1988

• RCT, blinded, crossover trial, n=12
• Nasopharyngeal catheters attached to 100% FiO2 at 3 L/min versus room air
• None of the patients in the insufflation arm desaturated below 98% during the 10 min

Evidence for apnoeic oxygenation in humans prior to 2012 is summarised here (from Levitan and Weingart, 2012)
OTHER INFORMATION
In addition to intubation, apnoeic oxygenation is also used in other circumstances:

• during brain death studies
• during bronchoscopy
• at the end of elective anestheisa cases when allowing CO2 to build up and stimulate spontaneous breathing

Nasal cannula

• Nasal cannulae at 15 L/min has no significant adverse affects in the sedated patient with short term use, and is even well tolerated in awake patients (Brainard et al, 2015). The desiccating effect is uncomfortable in the longer term in awake patients.
• Although flow meters for wall oxygen have 15 L/min as the maximum setting (gives FiO2 0.6 via non-rebreather) if over-dialed up to 30-60 L/min flow can be achieved (gives FiO2 0.8-0.9 via non-rebreather mask)
• If nasal cannulae compromise the seal of the face mask, they can be placed above the face mask until just prior to attempting laryngoscopy, at which point they are placed in the nares
• High flow nasal cannulae  have been used for apnoeic oxygenation (e.g. THRIVE study) however they are more likely to impair face mask seal during preoxygenation and some devices do not generate high enough FiO2.

Bag-Valve-Mask (BVM) with PEEP valve for apnoeic oxygenation

• A BVM with a PEEP valve will only provide PEEP when the patient expires, so positive pressure is not provided in apnoeic patients.
• If the patient is ventilated PEEP will only be transiently applied as the patient expires.
• However, continuous positive airways pressure (CPAP) (approx 6 cmH2O) is generated when 15L/min O2 via nasal cannulae are applied to an apnoeic patient in addition to a BVM with a PEEP valve set at 10 cm H20. This is shown below:

Capacity is the efficiency of storing charge without raising voltage (much). 

The most important component of a defibrillator is a capacitor that stores a large amount of energy in the form of electrical charge, then releases it over a short period of time. A capacitor consists of a pair of conductors (e.g. metal plates) separated by an insulator (called a dielectric). Conductors lose and gain electrons easily, and therefore allow current to flow; whereas insulators do not lose their electrons, and hardly allow any current to flow. 

​Capacity's SI is a FARAD.
One farad is 1 coulomb per volt. A coulomb is a unit of charge and is one ampere-second.

Capacitors can be used to store a lot of energy (start motors etc). Made of multiple materials.
It is really just two pieces of metal. Variable capacitors can tune circuits to change output and used for frequency-tuning.

Charge is the amount of electricity going through a circuit. Symbolized q, is a characteristic of a unit of matter that expresses the extent to which it has more or fewer electrons than protons.

Capacitance is charge over voltage - this is very misleading! Seems to imply if you put more charge, it's capacitance will increase. Capacitance however, is the only thing that cannot change in the equation.  Might it be better to say that Charge is capacitance multiplied by voltage. 

​INDUCTANCE
In electromagnetism and electronics, inductance is the property of an electrical conductor by which a change in current flowing through it induces an electromotive force in both the conductor itself and in any nearby conductors by mutual inductance. It is the change in current as time goes on.

Unit of Henry = Volt-seconds divided by amps.
​
Inductor is a solenoid for example. A current through a solenoid creates a magnetic field. 

As the current gets bigger, the magnetic field gets bigger. The loop is creating and changing the field. This is called self-inductance. It doesn't want the current going through it when the current has gone through it... so it basically looks like a battery facing the opposite way to current. So, it will prevent current - a 'bad battery'.  As more and more current begins to flow - eventually the circuit will ignore this bad battery. 

DEFIBRILLATORS
For successful defibrillation, the current delivered must be maintained for several milliseconds. However, the current and charge delivered by a discharging capacitor decay rapidly and exponentially. Inductors are therefore used to prolong the duration of current flow. They are coils of wire that produce a magnetic field when current flows through them. When current passes through an inductor, it generates a flow of electricity in the opposite direction which opposes current flow as predicted by Faraday’s law of electromagnetic induction. This opposition to current flow is called inductance (L) and is measured in henries (H). Inductors typically have values of microhenries (µH).

​

Power supply

Step-up transformers are used to convert the mains voltage of 240 V AC to 5000 V AC. This is then converted to 5000 V DC by a rectifier. In practice, a variable voltage step-up transformer is used so that different amounts of charge may be selected by the clinician. The control switch is calibrated in energy delivered to the patient (J), because this determines the clinical effect. If a mains supply is unavailable, most defibrillators have internal rechargeable batteries. These supply DC, which is then converted to AC by means of an inverter, and then amplified to 5000 V DC by a step-up transformer and rectifier as above.

eg) If there were 250v going in, with 20 turns on the primary coil - there would need to be 200 turns on the secondary coil to get the voltage to 2500v.

AC/DC Power Supply
Home and office outlets are almost always AC. This is because generating and transporting AC across long distances is relatively easy. At high voltages (over 110kV), less energy is lost in electrical power transmission. Higher voltages mean lower currents, and lower currents mean less heat generated in the power line due to resistance. AC can be converted to and from high voltages easily using transformers.
AC is also capable of powering electric motors. Motors and generators are the exact same device, but motors convert electrical energy into mechanical energy (if the shaft on a motor is spun, a voltage is generated at the terminals!). This is useful for many large appliances like dishwashers, refrigerators, and so on, which run on AC.

DC is quicker delivery and obviously, DIRECTLY applied - like via a battery. There have been trials which have concluded DC is superior to AC in defibrillation settings, presumably due to the time it takes to deliver a precisely timed shock, that does not oscillate in the delivery of power.