All Updates, ICU, PHARM, Resus

Difficult airways can't be reliably predicted

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This paper1 proves what Rich Levitan has been saying (and writing) for years – that there is no method of prediction of difficult intubation that is both highly sensitive (the test wouldn’t miss many difficult airways) and highly specific (meaning those predicted to be difficult would indeed turn out to be difficult). Most importantly, this means one should always have a plan for failure to intubate and failure to mask-ventilate regardless of how ‘easy’ the airway may appear.
This study of a large prospectively collected database captured anaesthetists’ clinical assessment of likelihood of difficult intubation and difficult mask-ventilation, and compared them with actual findings. These studies are always difficult, due in part to the lack of standard definitions of difficult airways, but the take home was clear – the large majority of difficulties were unanticipated and not suspected from pre-operative clinical assessment.
This issue was brilliantly summed up by Yentis in a 2002 Editorial2:
“I dare to suggest that attempting to predict difficult intubation is unlikely to be useful – does that mean one shouldn’t do it at all? To this I say no, for there is another important benefit of this ritual: it forces the anaesthetist at least to think about the airway, and for this reason we should encourage our trainees (and ourselves) to continue doing it.”
1. Diagnostic accuracy of anaesthesiologists’ prediction of difficult airway management in daily clinical practice: a cohort study of 188 064 patients registered in the Danish Anaesthesia Database
Anaesthesia. 2014 Dec 16. doi: 10.1111/anae.12955. [Epub ahead of print]
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Both the American Society of Anesthesiologists and the UK NAP4 project recommend that an unspecified pre-operative airway assessment be made. However, the choice of assessment is ultimately at the discretion of the individual anaesthesiologist. We retrieved a cohort of 188 064 cases from the Danish Anaesthesia Database, and investigated the diagnostic accuracy of the anaesthesiologists’ predictions of difficult tracheal intubation and difficult mask ventilation. Of 3391 difficult intubations, 3154 (93%) were unanticipated. When difficult intubation was anticipated, 229 of 929 (25%) had an actual difficult intubation. Likewise, difficult mask ventilation was unanticipated in 808 of 857 (94%) cases, and when anticipated (218 cases), difficult mask ventilation actually occurred in 49 (22%) cases. We present a previously unpublished estimate of the accuracy of anaesthesiologists’ prediction of airway management difficulties in daily routine practice. Prediction of airway difficulties remains a challenging task, and our results underline the importance of being constantly prepared for unexpected difficulties.

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2. Predicting difficult intubation–worthwhile exercise or pointless ritual?
Anaesthesia. 2002 Feb;57(2):105-9

All Updates, ICU, PHARM, Resus

High flow systems for apnoeic oxygenation

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nascaniconApnoeic oxygenation during laryngoscopy via nasal prongs has really taken off in the last couple of years in emergency department RSI, and is associated with decreased desaturation rates in out-of-hospital RSI.
More effective oxygenation and a small amount of PEEP can be provided by high flow nasal cannulae with humidified oxygen (HFNC)
A logical step in the progression of this topic is to consider HFNC for apnoeic oxygenation, and Reuben Strayer wrote about this nearly three years ago.
In a Twitter conversation today, Dr Pete Sherren highlighted a new article describing its use in anaesthesia for patients with difficult airways. This is labelled Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE). A reply from Dr Neil Brain points out that when used in kids, the bulkiness of the apparatus may get in the way of bag-mask ventilation (if that becomes necessary).
But does HFNC apnoeic oxygenation confer any advantages over standard nasal cannulae?
In an apnoeic patient, 15l/min via standard cannulae should fill the pharyngeal space with 100% oxygen, and you can’t improve on 100%.
HFNC provide some continuous positive pressure, but this may be cancelled by the necessary mouth opening for laryngoscopy.
One issue with apnoea is of course a rise in carbon dioxide with consequent acidosis. The authors of the THRIVE paper (abstract below) point out that in previous apnoeic oxygenation studies, the rate of rise of carbon dioxide levels was between 0.35 and 0.45 kPa/min (2.7-3.4 mmHg/min), whereas with THRIVE the rise was 0.15 kPa/min (1.1 mmHg/min). They suggest that continuous insufflation with high flow oxygen facilitates oxygenation AND carbon dioxide clearance through gaseous mixing and flushing of the deadspace.
So should we switch from standard nasal cannula to high flow cannulae for apnoeic oxygenation? I think not routinely, but perhaps consider it in patients:
(1) with pressure-dependent oxygenation (eg. ARDS) although I’m not sure any CPAP effect would be sustained during laryngoscopy
and
(2) in patients with significant acidosis in whom a significant rise in carbon dioxide could be detrimental (eg. diabetic ketoacidosis).
I look forward to reading more studies on this, and to hearing from anyone with experience of this technique in the comments section.
Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE): a physiological method of increasing apnoea time in patients with difficult airways.
Anaesthesia. 2014 Nov 10. doi: 10.1111/anae.12923. [Epub ahead of print]
[EXPAND Abstract]

Emergency and difficult tracheal intubations are hazardous undertakings where successive laryngoscopy-hypoxaemia-re-oxygenation cycles can escalate to airway loss and the ‘can’t intubate, can’t ventilate’ scenario.
Between 2013 and 2014, we extended the apnoea times of 25 patients with difficult airways who were undergoing general anaesthesia for hypopharyngeal or laryngotracheal surgery. This was achieved through continuous delivery of transnasal high-flow humidified oxygen, initially to provide pre-oxygenation, and continuing as post-oxygenation during intravenous induction of anaesthesia and neuromuscular blockade until a definitive airway was secured. Apnoea time commenced at administration of neuromuscular blockade and ended with commencement of jet ventilation, positive-pressure ventilation or recommencement of spontaneous ventilation. During this time, upper airway patency was maintained with jaw-thrust.
Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) was used in 15 males and 10 females. Mean (SD [range]) age at treatment was 49 (15 [25-81]) years. The median (IQR [range]) Mallampati grade was 3 (2-3 [2-4]) and direct laryngoscopy grade was 3 (3-3 [2-4]). There were 12 obese patients and nine patients were stridulous. The median (IQR [range]) apnoea time was 14 (9-19 [5-65]) min. No patient experienced arterial desaturation < 90%. Mean (SD [range]) post-apnoea end-tidal (and in four patients, arterial) carbon dioxide level was 7.8 (2.4 [4.9-15.3]) kPa. The rate of increase in end-tidal carbon dioxide was 0.15 kPa.min(-1) .
We conclude that THRIVE combines the benefits of ‘classical’ apnoeic oxygenation with continuous positive airway pressure and gaseous exchange through flow-dependent deadspace flushing. It has the potential to transform the practice of anaesthesia by changing the nature of securing a definitive airway in emergency and difficult intubations from a pressured stop-start process to a smooth and unhurried undertaking.

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Acute Med, All Updates, Guidelines, ICU, PHARM, Resus, Trauma

London Cardiac Arrest Symposium 2014

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The focus of the entire day is cardiac arrest and this is the second day of the London Cardiac Arrest Symposium.

Professor Niklas Nielsen kicked off with a presentation of his Targeted Temperature Management trial.  It seems that even now there is uncertainty in the interpretation of this latest study. I take heart from the knowledge that Prof Nielsen has changed the practice of his institution to reflect the findings of his study – I have certainly changed my practice. But we need to remain aware that there is more work to be done to answer the multiple questions that remain and the need for further RCTs is recognised.

The management of Cardiac arrest after avalanche is not a clinical scenario that I imagine I’ll ever find myself in. The management is well documented in the ICAR MEDCOM guidelines 2012. Dr Peter Paal reminded us that you’re not dead until you’re rewarmed and dead unless: with asystole, CPR may be terminated (or withheld) if a patient is lethally injured or completely frozen, the airway is blocked and duration of burial >35 min, serum potassium >12 mmol L(-1), risk to the rescuers is unacceptably high or a valid do-not-resuscitate order exists.

The age old question about prognostication after cardiac arrest was tackled by Prof Mauro Oddo. He covered the evidence for clinical examination, SSPE, EEG, and neurone specific enolase. Bottom line, all of these modalities are useful but none are specific enough to be used as a stand alone test so multiple modalities are required.

SAMU is leading the way with prehospital ECMO. They have mastered the art of cannulation (in the Louvre no less!) but there haven’t enough cases to demonstrate a mortality benefit. The commencement of ECMO prehospital reduces low flow time and theoretically should improve outcomes. This is begging for a RCT.

The experience of the Italians with in hospital ECMO shoes a better survival rate for in-hospital rather than out of hospital cardiac arrests, explained Dr Tomasso Mauri. They treat patients with a no flow time of <6min and low flow rate of <45min and had a 31% ICU survival rate. If you want to learn more about ED ECMO go to http://edecmo.org.

VA-ECMO

The Douglas Chamberlain lecture this year was Selective aortic arch perfusion presented by Prof James Manning. He spoke about the use of this technique in cardiac arrest and also in trauma (where it is known to you as Zone 1 REBOA).

image-1

In cardiac arrest the aim is to improve coronary perfusion, to preserve perfusion to the heart and the brain, offer a route of rapid temperature control and offer a direct route of administration of adrenaline. Coronary perfusion is seen to be supra normal after SAAP. And the suggested place for SAAP is prior to ECMO.

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It’s more familiar ground talking about SAAP in trauma. This Zone 1 occlusion preserves cerebral and cardiac perfusion while blood loss is limited and rapid fluid resuscitation can occur.

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You can hear Prof Manning on SAAP over at EMCrit (of course!). 

It’s been another great conference. Put the dates for next year’s London Trauma & Cardiac Arrest Conferences in your diary: 8th-10th December 2015!

Happy Holidays & Keep Well

Louisa Chan

 

 

 

 

 

All Updates, Resus, Trauma

London Trauma Conference 2014 Part 2

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Day three is Air Ambulance and pre-hospital day and the great and the good are here en mass.
The heavy weights are coming out to make their points…..
selfUnarguably the best lecture of the day was delivered by our very own Cliff Reid on prehospital training. Using Sydney HEMS induction training he highlighted the challenges posed to prehospital services training doctors and paramedics rotating through the service.
Turning a good inhospital doctor into a great prehospital one in the space of an induction program requires focus. Knowledge is therefore not the focus of training, performance is. Often doctors already possess the clinical skills and knowledge and it is the application of these pre existing skills in challenging environments when cognitively overloaded that is the key.
 
The Sydney HEMS program provides the mindware and communication skills the practitioner needs to do this and drills these skills in simulated environments. He uses perturbation, so like the Bruce protocol exercise test the simulations just get harder until you are at the very limits of your bandwidth. Debriefing of course is important but the recommended protracted debrief is often impractical and unnecessary so simulations designed with cognitive traps are used to highlight learning points and are drilled until the message is received. In this way tress exposure enhances cognitive resilience. And importantly they use cross training, so the doctors and the paramedics undergo the same program so each member of the team understands the challenges faced by the other.
Does this sound like fun? For the shrinking violets out there it could be seen as threatening. But for the adrenaline junkies…….hell yeah!
It’s truly a training ethos that I buy into and I’d love to be able to achieve that standard of training in my own service.

SydneyHEMStops
Sydney HEMS Friends and Colleagues at the LTC

 
mwaveMicrowaves seem to be the future if diagnostic testing. This modality is fast, is associated with a radiation dose lower than that of a mobile phone, non invasive, portable and has been shown to provide good information. It can be used on heads for intracranial haemorrhage and stroke or chests for pneumothorax detection. It’s all in the early stages but seems like it will be a viable option in the future.
For further reading check out:
Diagnosis of subdural and intraparenchymal intracranial hemorrhage using a microwave-based detector
Clinical trial on subdural detection
Pneumothorax detection
 
How would you transfer a psychotic patient requiring specialist intervention that can only be received after aeromedical transfer? Stefan Mazur of MedSTAR, the retrieval service in South Australia shared their experience with ketamine to facilitate the safe transfer of these patients with no reports of adverse effects on the mental state of the patient, as first described by Minh Le Cong and colleagues. Is there no end to the usefulness of this drug? No wonder we’re experiencing a supply issue in the UK!
And finally, the ultimate reflective practice should include the post mortem of our critically sick patients. The approach the forensic pathologist takes is similar to a clinician (with the time pressure removed). They read the scene and use this information to predict injuries (sound familiar?). Post mortem CT scanning with recon provides yet another layer of information. We are missing a trick if we don’t seek this feedback to correlate with our clinical findings. Even better, rare practical skills are often routinely performed as part of the post mortem – we should be making use of this opportunity to train.

All Updates, Resus, Trauma

London Trauma Conference 2014 Part 1

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I’ve travelled almost the entire length of England to get to the London Trauma Conference this year. What could be more important than attending one of the best conferences of the year? Examining for the DipRTM at the Royal College of Surgeons in Edinburgh
So was it worth the 4am start? Absolutely!
tomMy highlights would be Tom Evens explaining why trauma can be regarded like an elite sport. His background is as a sports coach in addition to his medical accomplishments and walking us through the journey he went through with the athlete he was coaching demonstrates the changes that need to occur when cultivating a performance culture and the results speak for themselves.
I can see similarities in the techniques used by athletes and those we are using in medicine now. Developing a highly performing team isn’t easy as anyone involved in the training of these teams will know.
 
 
jerry3Dr Jerry Nolan answered some questions about cervical spine movement in airway management. The most movement is seen in the upper cervical spine and there is no surprise that there is an increased incidence of cervical spine injury in unconscious patients (10%). The bottom line is that no movement clinicians will make of the cervical spine is greater than that at the time of injury. And whether it be basic airway manoeuvres, laryngoscopy or cricoid pressure the degree of movement is in the same ball park and unlikely to cause further injury. He states that he would use MILS like cricoid pressure and have a low threshold for releasing it if there are difficulties with the intubation. Of course many of us don’t use cricoid pressure in RSI anymore………..
 
After watching Tom and Jerry we heard that ATLS has had its day. Dr Matthew Wiles implores us to reserve ATLS for the inexperienced and move away from this outdated system and move to training in teams using local policies. The Cochrane reviewers found an increase in knowledge but no change in outcomes.
And finally Dr Deasy has convinced me that I will be replaced by a robot roaming around providing remote enhanced care. On the up side I might be the clinician providing that support.
More from me on this fantastic conference soon. In the meantime follow it on Twitter!
telemed
 

All Updates, ICU, Kids, PHARM, Resus, Trauma

Bilateral fixed dilated pupils? Operate if extradural!

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Almost two-thirds of patients with extradural haematoma and bilateral fixed dilated pupils survived after surgery, with over half having a good outcome

 
pupilsiconNeurosurgeon, HEMS doctor, and all round good egg Mark Wilson was on the RAGE podcast recently and mentioned favourable outcomes from neurosurgery in patients with extradural (=epidural) haematomas who present with bilateral fixed dilated pupils (BFDP). Here’s his paper that gives the figures – a systematic review and meta-analysis.
A total of 82 patients with BFDP who underwent surgical evacuation of either subdural or extradural haematoma were identified from five studies – 57 with subdural (SDH) and 25 with extradural haematomas (EDH).
In patients with EDH and BFDP mortality was 29.7% (95% CI 14.7% to 47.2%) and 54.3% had a favourable outcome (95% CI 36.3% to 71.8%).
Only 6.6% of patients with SDH and BFDP had a good functional outcome.
Clearly there is potential for selection bias and publication bias, but these data certainly suggest an aggressive surgical approach is appropriate in some patients with BFDP.
The authors comment on the pessimism that accompanies these cases, which potentially denies patients opportunities for recovery:


“We believe that 54% of patients with extradural haematoma with BFDPs having a good outcome is an underappreciated prognosis, and the perceived poor prognosis of BFDPs (from all causes) has influenced decision making deeming surgery inappropriately futile in some cases.”

Scotter J, Hendrickson S, Marcus HJ, Wilson MH.
Prognosis of patients with bilateral fixed dilated pupils secondary to traumatic extradural or subdural haematoma who undergo surgery: a systematic review and meta-analysis.
Emerg Med J 2014 e-pub ahead of print Nov 11;:1–7
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Primary objective To review the prognosis of patients with bilateral fixed and dilated pupils secondary to traumatic extradural (epidural) or subdural haematoma who undergo surgery.

Methods A systematic review and meta-analysis was performed using random effects models. The Cochrane Central Register of Controlled Trials and PubMed databases were searched to identify relevant publications. Eligible studies were publications that featured patients with bilateral fixed and dilated pupils who underwent surgical evacuation of traumatic extra-axial haematoma, and reported on the rate of favourable outcome (Glasgow Outcome Score 4 or 5).

Results Five cohort studies met the inclusion criteria, collectively reporting the outcome of 82 patients. In patients with extradural haematoma, the mortality rate was 29.7% (95% CI 14.7% to 47.2%) with a favourable outcome seen in 54.3% (95% CI 36.3% to 71.8%). In patients with acute subdural haematoma, the mortality rate was 66.4% (95% CI 50.5% to 81.9%) with a favourable outcome seen in 6.6% (95% CI 1.8% to 14.1%).

Conclusions and implications of key findings Despite the poor overall prognosis of patients with closed head injury and bilateral fixed and dilated pupils, our findings suggest that a good recovery is possible if an aggressive surgical approach is taken in selected cases, particularly those with extradural haematoma.

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All Updates, Guidelines, ICU, Resus, Trauma

Early femur fixation recommended

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The Eastern Association for the Surgery of Trauma recommends early (<24 hours) open reduction and internal fracture fixation in trauma patients with open or closed femur fractures.
They acknowledge the strength of the evidence is low, but suggests a trend toward lower risk of infection, mortality, and venous thromboembolic disease.
They conclude: “the desirable effects of early femur fracture stabilization probably outweigh the undesirable effects in most patients”
Check out the rest of the EAST Trauma Guidelines
Optimal timing of femur fracture stabilization in polytrauma patients: A practice management guideline from the Eastern Association for the Surgery of Trauma
Journal of Trauma and Acute Care Surgery 2014;77(5):787-795
[EXPAND Abstract]


BACKGROUND
Femur fractures are common among trauma patients and are typically seen in patients with multiple injuries resulting from high-energy mechanisms. Internal fixation with intramedullary nailing is the ideal method of treatment; however, there is no consensus regarding the optimal timing for internal fixation. We critically evaluated the literature regarding the benefit of early (<24 hours) versus late (>24 hours) open reduction and internal fixation of open or closed femur fractures on mortality, infection, and venous thromboembolism (VTE) in trauma patients.

METHODS
A subcommittee of the Practice Management Guideline Committee of the Eastern Association for the Surgery of Trauma conducted a systematic review and meta-analysis for the earlier question. RevMan software was used to generate forest plots. Grading of Recommendations, Assessment, Development, and Evaluations methodology was used to rate the quality of the evidence, using GRADEpro software to create evidence tables.

RESULTS
No significant reduction in mortality was associated with early stabilization, with a risk ratio (RR) of 0.74 (95% confidence interval [CI], 0.50–1.08). The quality of evidence was rated as “low.” No significant reduction in infection (RR, 0.4; 95% CI, 0.10–1.6) or VTE (RR, 0.63; 95% CI, 0.37–1.07) was associated with early stabilization. The quality of evidence was rated “low.”

CONCLUSION
In trauma patients with open or closed femur fractures, we suggest early (<24 hours) open reduction and internal fracture fixation. This recommendation is conditional because the strength of the evidence is low. Early stabilization of femur fractures shows a trend (statistically insignificant) toward lower risk of infection, mortality, and VTE. Therefore, the panel concludes the desirable effects of early femur fracture stabilization probably outweigh the undesirable effects in most patients.

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All Updates, Resus

SMACC Chicago – don't miss the boat!

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smacc chicago.002sm
If you’ve attended a SMACC conference or heard anything about them, you will be aware that it is the most exciting, inspiring, interesting, and educational critical care conference ever.
It is a non-profit venture dedicated to getting the best educators, clinicians, and researchers in intensive care, emergency medicine, prehospital/retrieval medicine and anaesthesia to share their knowledge, for free, through the medium of FOAM, embracing physicians, nurses, paramedics, and students.
You can access most of the content through podcasts after the event, but there is NOTHING like actually BEING THERE to experience the vibe.
And in 2015 it’s in Chicago. In the United States. It will be AMAZING.
You can’t look at the program without being blown away. Just look at the preconference workshops and you’ll become vertiginous trying to get your head around the the fact you can’t be in two places at once.
Why am I raving about this? What’s in it for me?
Like the other presenters I make no money from this – I dedicate my time, energy and passion for critical care and am so privileged to be a part of it. But as a do-everything-at-the-last-possible-minute emergency physician, registering for a conference is the kind of thing I’m often inclined to leave a few weeks until I can get round to it. But you CAN’T AFFORD to do that for SMACC Chicago. Not only will you waste money by missing the early registration discount, you might miss out completely: I anticipate registrations will be oversubscribed fast (this is the most anticipated conference EVER) and if you leave it too late you won’t be able to come and will be confined to the crowd who are forced to hear how great it was after the event from the people who were organised enough to actually get there.
So don’t miss out! You’ll feel like a muppet! Treat yourself to the best education at the best conference ever – pull your finger out now and register. And I’ll see you there.

Acute Med, All Updates, ICU, Resus

Left Ventricular Assist Device for Cardiac Arrest?

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LVADguyiconAn interesting case report by Dr Heidlebaugh and colleagues from the Department of Emergency Medicine at the William Beaumont Hospital describes a 72 year old marathon runner who arrested during cardiac catheterisation. It suggests a possible novel alternative to ECMO for cardiac arrest.
The patient became bradycardic then asystolic during catheterisation of his right coronary artery. High quality CPR was initiated and an Impella LV assist device was placed. This restored cardiac output which was followed by episodes of venticular fibrillation and then ROSC. His initial low ejection fraction of 15% recovered after targeted temperature management on ICU to 50% and he fully recovered neurologically.
This patient already had femoral arterial access for introduction of the Impella, since he was in a cath lab. He also had immediate CPR on arresting, and was an abnormally fit 72 year old. It remains to be seen whether this procedure can be applied to other patients in cardiac arrest. The authors state:

“..until ECLS is readily available, poor survival and neurological outcome after cardiac arrest might be avoided in many patients by the use of pLVAD to offload the LV and enhance perfusion. Furthermore, there may be a subset of patients, in whom the support that pLVAD offers is sufficient to optimize hemodynamic parameters and bridge to ROSC, thus reducing the need for ECLS.”

This video by Dr. I-Wen Wang from the Barnes-Jewish Hospital explains how the Impella is inserted and how it works.
 

 
Full Neurologic Recovery and Return of Spontaneous Circulation Following Prolonged Cardiac Arrest Facilitated by Percutaneous Left Ventricular Assist Device
Ther Hypothermia Temp Manag. 2014 Sep 3. [Epub ahead of print]
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Sudden cardiac arrest is associated with high early mortality, which is largely related to postcardiac arrest syndrome characterized by an acute but often transient decrease in left ventricular (LV) function. The stunned LV provides poor cardiac output, which compounds the initial global insult from hypoperfusion. If employed early, an LV assist device (LVAD) may improve survival and neurologic outcome; however, traditional methods of augmenting LV function have significant drawbacks, limiting their usefulness in the periarrest period. Full cardiac support with cardiopulmonary bypass is not always readily available but is increasingly being studied as a tool to intensify resuscitation. There have been no controlled trials studying the early use of percutaneous LVADs (pLVADs) in pericardiac arrest patients or intra-arrest as a bridge to return of spontaneous circulation. This article presents a case study and discussion of a patient who arrested while undergoing an elective coronary angioplasty and suffered prolonged cardiopulmonary resuscitation. During resuscitation, treatment included placement of a pLVAD and initiation of therapeutic hypothermia. The patient made a rapid and full recovery.

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Image is of M. Joshua Morris, a happy LVAD recipient (not the patient in the described study) who kindly alerted me to this article. Used with permission.

Resuscitation Medicine from Dr Cliff Reid