How You Train is How You Fight

January 1, 2014 by  
Filed under All Updates

Simulation makes us more effective. I think it’s good to consider how one would deal with emergency situations in every day life, and practice the response. There are ALWAYS learning points.

My four year old son Kal brought along his rubber red bellied black snake on a New Year’s Day bush walk with my family. Too good an opportunity to miss, so we practiced managing a snakebite scenario. What we did and what we learned are summarised in this three minute video:

 
This was a worthwhile exercise. Learning points were:

1. Carry a knife to help cut up the teeshirt (if you don’t carry bandages)

2. Call for help early – it takes several minutes to apply the pressure immobilisation bandage, so ideally these things are done in parallel rather than series.

3. Know how to get your coordinates from your smart phone. Several free apps are available.
On an Apple iPhone, they are displayed on the ‘Compass’ app but ONLY if you have enabled location services (Settings->Privacy->Location Services->Compass)

location services compass-10

 

 

 

 

 

 

 

 

 

Learn more about pressure immobilisation technique and its indications from the Australian Resuscitation Council

London Trauma Conference Day 3

December 13, 2013 by  
Filed under Acute Med, All Updates, EMS, ICU, Resus, Trauma


Dr Louisa Chan reports on Day 3 of the London Trauma Conference

There was a jam-packed line up for the Pre-hospital and Air Ambulance Day which was Co-hosted by the Norwegian Air Ambulance Foundation.
 

My highlights were:

HEMS

Dr Rasmus Hesselfeldt works in Denmark where they have a pretty good EMS system with ambulances, RRV’s and PHC doctors. Road conditions are good with the longest travel distance of 114 miles. So would the introduction of a HEMS service improve outcomes? He did an observational study looking at year of data post-trial and compared this with 5 months pre-trial. Trauma patients with ISS > 15 and medical emergencies greater than 30 min by road to the Trauma Centre (TC). Primary endpoint was time to TC, secondary outcomes were number of secondary transfers and 30 day mortality.

Results: Increase in on scene time 20 min vs 28 min, time to hospital increased but time to TC was less – 218 min vs 90 min, reduced mortality, increased direct transfer to TC and fewer secondary transfers.

Full article here: A helicopter emergency medical service may allow faster access to highly specialised care. Dan Med J. 2013 Jul;60(7):A4647

 

Airway

Prof Dan Davis ran through pre-hospital intubation. It seems that this man has spent his life trying to perfect airway management. Peter Rosen was his mentor and imprinted on him that RSI is the cornerstone of airway management.

So surely pre-hospital intubation saves lives. The evidence however begs to differ, or does it? As with all evidence we need to consider the validity of the results and luckily Prof Davis has spent a lot of time thinking through the reasons why there no evidence.

During his research he opened a huge can of worms:
1. Hyperventilation was common – any EtCO2 <30mmHg lead to a doubling in mortality.
2. First pass intubation is great, but not if you let your patient become hypoxic or hypotension or worse still both!
3. Hospital practice had similar issues.

So really the RSI processes he was looking at weren’t great.

The good news is that things have improved and he can now boast higher first pass rates and lower complication rates for his EMS system. His puts this success down to training.

 

 

AIRPORT-LTCThe AIRPORT study was discussed at last years LTC. This year we have the results. 21 HEMS services in 6 countries were involved in the data collection including GSA HEMS. The headline findings are that intubation success rates are high (98%) with a complication rate of 10-12%. The more difficult airways were seen in the non-trauma group. 28.2% patients died (mainly cardiac arrest).

 

 

Matt Thomas reported on REVIVE – a pre-hospital feasibility study looking at airway management in OHCA (I-Gel vs LMA Supreme vs standard care). It was never powered to show a difference in these groups, the main aim was to see if research in this very challenging area was possible. And the answer is YES. The paramedics involved recruited more patients than expected and stuck to the protocol (prob better that docs would have!). A randomised controlled trial to look at the I-Gel vs ETT is planned.

 

(P)REBOA

ReboaLTCFinally, Pre-hospital Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) seems eminently possible – Dr Nils Petter Oveland showed us the training manikin they developed for training. Through training on this manikin they achieved an average skin to balloon time of 3.3mins. Animal data supports this procedure as a bridge to definitive care in non compressible haemorrhage.

London HEMS will be starting (P)REBOA in the New Year.

So now it’s stand up science, I’m off for my glass of wine…………….

Check out what they’re saying about the London Trauma Conference on Twitter

London Trauma Conference Day 2

December 12, 2013 by  
Filed under Acute Med, All Updates, EMS, ICU, Resus, Trauma

London Trauma Conference 2013 – Day 2  by Dr Louisa Chan

So I find myself torn today: do I join the the main track with a Major incident theme or the Cardiac Masterclass? I never liked the thought of missing out on anything so I went to a bit of both.

 
Cardiac Masterclass

A lot of people probably think that managing cardiac arrest isn’t challenging and a bit dull because the patient is dead. But the Cardiac Masterclass would inspire you to think of a bright future for cardiac arrest management.

Mark Whitbread reminded us of how important dispatch is in the chain of survival. How much focus do we put on improving bystander CPR rates? Dispatcher assisted CPR has been shown to improve outcomes and needs to be skilfully done.

Ajay Jain pushes for all OHCA patients to be taken to a Cardiac Arrest centre for PCI. Why? Because the results he has from his centre for PCI in OHCA patients results in 77% (101/132) patients surviving to hosp discharge, 65% neurologically intact.

He also tells us that the ECG post arrest is a very poor predictor of PCI findings (although STEMI predicts a positive result) so they all should have PCI.
Lyon-survivors

 

More data from TOPCAT shows us that non survivors of OHCA are easy to cool.

 

LTC-mice

 

 

And maybe we should be cooling DURING cardiac arrest to minimise the reperfusion injury.

 

 

For persistent VF Prof Redwood says revascularisation is the key; when that doesn’t work then reducing LV volume may help so aspiration or an Impella may work. Failing that – ECMO.

 
Major Incidents

Major Incidents by their nature do not happen every day, so experience in these incidents is limited. The challenge then is how can we learn from incidents?

A standardised reporting system for a major incident database would be a good idea – www.majorincidentreporting.org – is where you will find the standard report form and open access database.

And then all I can suggest is that you need to come to the LTC and listen to the accounts of those who have been there. We heard about the Tokyo Sarin attack, Mumbai, and a very compelling story of multiple drownings from Steen Barnung.

Lessons from Tokyo – Sarin attack:

It will happen again
It will be chaos
Crowds cannot be controlled
Comms will fail
Clinical diagnosis – need a senior clinician
Treatment must be immediately available – 3min to absorb sarin
Decontamination – get naked, 90% decon with clothes removal.
Stream casualties
Empower the man on the ground.

 

Gadgets

LTC-MSUThe great thing about the London Trauma Conference is that it’s not just about the content of the tracks, there’s the networking and the opportunity to see new pieces of equipment.

The Norwegians won on the equipment front with their Mobile Stroke Unit. It’s due to go on line in 2014.

So TTFN and more from me on Day 3 of #LTC2013

London Trauma Conference 2013

December 11, 2013 by  
Filed under Acute Med, All Updates, EMS, ICU, Resus, Trauma

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FDIA_ImageOur inside reporter Dr Louisa Chan provides an update from Day One of the London Trauma Conference:

At risk of sounding like a resuscisaurus, last year was my first foray into the world of blogging. I’m proud to say that the genetic make up of most emergency physicians allows us to adapt so that others do not die! And so here I am again, making my way into the big smoke to report on the great developments of 2013.

I’ve struggled in the past to prise myself away from the main trauma track, it is after all the London Trauma Conference, which has left me curious as to the content of the Cardiac arrest symposium, this year it has been integrated, so I finally get to scratch that itch.

 

Prehospital Cardiac Arrest Management in Scotland

The conference was kicked off by Richard Lyon‘s inspirational description of his TOPCAT study.

In Scotland, of 50 cardiac arrests, 6 will survive to hospital and only 1 will survive to hospital discharge. The survival to hospital discharge in the UK is getting worse (4.8% 1995- 0.7% 2007)

Spurred on by these dreadful figures and a personal quest to improve cardiac arrest care (his father succumbed to a cardiac arrest in his forties)

All in all he has studied 400 cardiac arrest patients pre hospital. So what has he learnt?

  • Precise application of the chain of survival to your own system is vital in the delivery of Quality CPR.
  • He started in the ambulance control room analysing calls (CPR starts at step 11 so more experienced dispatchers skip thee quicker) and worked his way through the chain of survival.
  • The TOPCAT study revealed a 3 min delay to compressions where early intubation and cannulation were performed. Through an education program delivering knowledge and skills with individualised feedback they were able to increase on-chest time.
  • LEADERSHIP was a big factor. Having a clinician dedicated to managing the team improved on chest time and is now delivered by paramedics manning a car response in Edinburgh.
  • Breaks in CPR during movement are overcome by a mechanical chest compression device on carry sheet.
  • Non technical skills are monitored by camera feed
  • These changes have led to a survival to hospital discharge rate of 38% for patients in VF
  • This could translate into an extra 300 lives saved in Scotland when these changes are rolled out nationally.
  • And now there is a move to transport patients who are in VF after the third shock then straight to cath lab.

 

Echocardiography in cardiac arrest

Prof Tim Harris spoke about his passion – echocardiography in resuscitation. If you were in any doubt before then you would leave convinced.

Of course echo should not interfere with CPR so it should be done during the rhythm check with a 10 sec count down.

He covered the usual uses; PEA vs EMD in prognostication (92% sensitivity and 82% specificity to ROSC), Circulation assessment and an estimation of EF (Normal function – anterior mitral valve leaflet hits the septum or is within 5mm , EF 30-45% between 5mm- 18mm and >18mm ant mitral valve leaflets – 30% EF)

 

Cardiogenic shock after cardiac arrest

Professor Deakin: optimising cardiac function after ROSC revolves around the three elements of preload, SVR and myocardial contractility. For those who can still remember how, he recommends preload should be optimised to a LA pressure 15-20mmHg (2-12 normal) with a Swan Ganz catheter.
SVR and contractility can be manipulated thereafter using traditional vasopressors and inotropes or more novel agents like Levosimendan.
Mechanical devices such as IABP, Impella, TandemSupport are useful if available.
Where does the future lie? Perhaps synchronised pacing, hypothermia, extrathoracic ventilation and gene therapy.

LTC-BrohiOpen chest cardiac massage

Prof Karim Brohi: external chest compressions have been around since the 1960′s. Without a doubt external compressions generate a cardiac output, but is this the best way?
Over the last 10 years the priorities in traumatic cardiac arrest have changed – chest compressions are not instituted until after reversible causes have been addressed.
In non traumatic arrest how could we improve?
In canine models coronary perfusion pressure is five times better with internal cardiac massage, providing better survival rates with intact neurology.
There are a few human studies showing marked differences in cardiac index: 1.31 in the open group vs 0.61 in the closed group. In a Japanese study (1993), ROSC was achieved in 58% in open vs 1% closed.
The technique is two handed and the same as that taught in thoracotomy training. The difference is that in medical cardiac arrest you can use a smaller incision ( left lateral).
Who should we use open cardiac massage on? Perhaps in tamponade and pulmonary embolism?

How about when? When 10-15min with “standard care” has failed?

Perhaps it is time for a trial?

Post cardiac arrest syndrome and neuro protective measures
Prof Simon Redwood and Matt Thomas had overlapping talks on this . The bottom line is don’t have too much or too little CO2 or O2. The therapeutic hypothermia debate continues, what is evident is that there should be temperature control to avoid hyperthermia but what temperature? And there may be other benefits to hypothermia eg. limitation of infarct size.

What has been evident from all the speakers today is that it is an integrated system that saves lives and in order to guide the development of your system you need data and the belief that you can improve cardiac arrest outcomes.

More from me tomorrow!

Louisa Chan

Guidelines on prehospital drug-assisted LMA insertion

December 9, 2013 by  
Filed under All Updates, EMS, Guidelines, Trauma

The UK’s Faculty of Prehospital Care has published a number of consensus guidelines in this month’s EMJ

Dr Minh Le Cong‘s PHARM blog has summaries of three of them:

The final one is the most contentious: Pharmacologically assisted laryngeal mask insertion: a consensus statement(1). Here is the summary:

  1. The PALM technique is an acceptable tool for managing the prehospital airway
  2. The PALM technique is indicated in a rare set of circumstances
  3. The PALM procedure is a rescue technique
  4. The PALM procedure should be checklist driven
  5. At least a second generation SAD should be used
  6. End-tidal CO2 monitoring is mandatory
  7. No preference is expressed for any particular drug
  8. No preference is expressed for any particular dosing regime
  9. Flumazenil is highly unlikely to have a role in managing the PALM patient
  10. The PALM procedure should only be carried out by practitioners of level 7 or above competences
  11. The availability of a trained assistant, familiar with the procedure would be advantageous
  12. The training required to achieve competency in performing the PALM procedure must include in-hospital insertion of SADs, simulation training and training in the transfer of critically ill patients
  13. Data should be collected and collated at a national level for all patients who receive the PALM procedure

They qualify the first point with the statement: The consensus group felt that, in the hands of a specific set of practitioners and in certain circumstances, patients would benefit from the technique. It was recognised that pre-hospital airway management can be very challenging, and deeming the technique unacceptable could deprive patients of a potentially life saving intervention. It was felt that having another tool available to clinicians which could potentially improve patient outcome was important. This was despite the lack of a robust evidence base. It was felt that the technique is indicated in, and should be limited to, a very specific set of circumstances as described below

The publication lists some ‘Organisations represented at the consensus meeting’, which include some commercial training and equipment companies.

It also states that ‘The Royal College of Anaesthetists, although represented at the initial meeting, was unable to support the outcomes agreed by the other represented organisations.

This is a very interesting development. I can see the pros and cons of this. Since practitioners are out there doing PALM anyway, it is in the interests of patients to produce a statement that encourages monitoring, checklists, training, and data collection. To meet all the requirements, one must undergo ‘training in the transfer of critically ill patients’, which would normally necessitate more advanced airway and anaesthesia skills anyway.

A tough one – what would you want if there was no RSI capability but you were hypoxic with trismus and basic airway maneouvres were failing? An all out ban on PALM, or PALM provided by someone trained in surgical airway if it fails (as per the consensus recommendations)?

This and some of the other statements can be downloaded in full at the Faculty of Pre-hospital Care site

1. Pharmacologically assisted laryngeal mask insertion: a consensus statement
Emerg Med J. 2013 Dec;30(12):1073-5

Prehospital ECLS – it’s happening

November 13, 2013 by  
Filed under Acute Med, All Updates, EMS, ICU, Resus

Patients with refractory (>30 mins) cardiac arrest underwent prehospital cannulation for extracorporeal life support in a French feasibility study. A physician-paramedic team responded by car in Paris to cardiac arrest cases that met inclusion criteria. Mechanical CPR devices (Autopulse or LUCAS) were applied during cannulation. Femoral venoarterial ECMO was instituted using a Maquet Cardiohelp system. Blood products and inotropes, echocardiography, and hypothermia were included in the prehospital management package.

Seven patients were treated, with a mean age of 42 (+/- SD of 16, no median given). ECLS was started an average 57 min (±21) after the onset of ACLS. One patient survived to discharge neurologically intact. Two brain dead patients became organ donors. The survivor had hypertrophic cardiomyopathy with refractory ventricular fibrillation.

Safety and feasibility of prehospital extra corporeal life support implementation by non-surgeons for out-of-hospital refractory cardiac arrest
Resuscitation. 2013 Nov;84(11):1525-9


BACKGROUND: Extra corporeal life support (ECLS) has been recently introduced in the treatment of refractory cardiac arrest (CA). Several studies have assessed the use of ECLS in refractory CA once the patients reach hospital. The time between CA and the implementation of ECLS is a major prognostic factor for survival. The main predictive factor for survival is ECLS access time. Pre hospital ECLS implementation could reduce access time. We therefore decided to assess the feasibility and safety of prehospital ECLS implementation (PH-ECLS) in a pilot study.

METHODS AND RESULTS: From January 2011 to January 2012, PH-ECLS implementation for refractory CA was performed in 7 patients by a PH-ECLS team including emergency and/or intensivist physicians and paramedics. Patients were included prospectively and consecutively if the following criteria were met: they had a witnessed CA; CPR was initiated within the first 5min of CA and/or there were signs of life during CPR; an PH-ECLS team was available and absence of severe comorbidities. ECLS flow was established in all patients. ECLS was started 22min (±6) after the incision, and 57min (±21) after the onset of advanced cardiovascular life support (ACLS). In one patient, ECLS was stopped for 10min due to an accidental decannulation. One patient survived without sequelae. Three patients developed brain death.

CONCLUSIONS: This pilot study suggests that PH-ECLS performed by non-surgeons is safe and feasible. Further studies are needed to confirm the time saved by this strategy and its potential effect on survival.

Trauma before and beyond the hospital

July 2, 2013 by  
Filed under All Updates, EMS, ICU, Podcasts, Resus, Trauma

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Sydney HEMS physician Dr Brian Burns talks about the prehospital care of trauma in this 20 minute audio podcast recorded at SMACC 2013

Further talks from the SMACC conference are available for free download on iTunes.

Here are the accompanying slides:

Traumatic cardiac arrest outcomes

February 25, 2013 by  
Filed under All Updates, EMS, ICU, Kids, Resus, Trauma

simEver heard anyone spout dogma along the lines of: “it’s a traumatic cardiac arrest – resuscitation is futile as the outcome is hopeless: survival is close to zero per cent”?

I have. Less frequently in recent years, I’ll admit, but you still hear it spout forth from the anus of some muppet in the trauma team. Here’s some recent data to add to the existing literature that challenges the ‘zero per cent survival’ proponents. A Spanish study retrospectively analysed 167 traumatic cardiac arrests (TCAs). 6.6% achieved a complete neurological recovery (CNR), which increased to 9.4% if the first ambulance to arrive contained an advanced team including a physician. Rhythm and age were important: CNR was achieved in 36.4% of VFs, 7% of PEAs, and 2.7% of those in asystole; survival rate by age groups was 23.1% in children, 5.7% in adults, and 3.7% in the elderly.

Since traumatic arrest tends to affect a younger age group than medical arrests, the authors suggest:

Avoiding the potential decrease in life expectancy in this kind of patient justifies using medical resources to their utmost potential to achieve their survival

Since 2.7% of the asystolic patients achieved a CNR, the authors challenge the practice proposed by some authors that Advanced Life Support be withheld in TCA patients with asystole as the initial rhythm:

had that indication been followed, three of our patients who survived neurologically intact would have been declared dead on-scene.”

I’d like to know what interventions were making the difference in these patients. They describe what’s on offer as:


In our EMS, all TCA patients receive ALS on-scene, which includes intubation, intravenous access, fluid and drug therapy, point-of-care blood analysis, and procedures such as chest drain insertion, pericardiocentesis, or Focused Assessment with Sonography for Trauma ultrasonography to improve the treatment of the cause of the TCA.

It appears that crystalloids and colloids are their fluid therapy of choice; unlike many British and Australian physician-based prehospital services they made no mention of the administration of prehospital blood products.

Traumatic cardiac arrest: Should advanced life support be initiated?
J Trauma Acute Care Surg. 2013 Feb;74(2):634-8


BACKGROUND: Several studies recommend not initiating advanced life support in traumatic cardiac arrest (TCA), mainly owing to the poor prognosis in several series that have been published. This study aimed to analyze the survival of the TCA in our series and to determine which factors are more frequently associated with recovery of spontaneous circulation (ROSC) and complete neurologic recovery (CNR).

METHODS: This is a cohort study (2006-2009) of treatment benefits.

RESULTS: A total of 167 TCAs were analyzed. ROSC was obtained in 49.1%, and 6.6% achieved a CNR. Survival rate by age groups was 23.1% in children, 5.7% in adults, and 3.7% in the elderly (p < 0.05). There was no significant difference in ROSC according to which type of ambulance arrived first, but if the advanced ambulance first, 9.41% achieved a CNR, whereas only 3.7% if the basic ambulance first. We found significant differences between the response time and survival with a CNR (response time was 6.9 minutes for those who achieved a CNR and 9.2 minutes for those who died). Of the patients, 67.5% were in asystole, 25.9% in pulseless electrical activity (PEA), and 6.6% in VF. ROSC was achieved in 90.9% of VFs, 60.5% of PEAs, and 40.2% of those in asystole (p < 0.05), and CNR was achieved in 36.4% of VFs, 7% of PEAs, and 2.7% of those in asystole (p < 0.05). The mean (SD) quantity of fluid replacement was greater in ROSC (1,188.8 [786.7] mL of crystalloids and 487.7 [688.9] mL of colloids) than in those without ROSC (890.4 [622.4] mL of crystalloids and 184.2 [359.3] mL of colloids) (p < 0.05).

CONCLUSION: In our series, 6.6% of the patients survived with a CNR. Our data allow us to state beyond any doubt that advanced life support should be initiated in TCA patients regardless of the initial rhythm, especially in children and those with VF or PEA as the initial rhythm and that a rapid response time and aggressive fluid replacement are the keys to the survival of these patients.

Advanced airways and worse outcomes in cardiac arrest

January 20, 2013 by  
Filed under Acute Med, All Updates, EMS, Resus

A new study demonstrates an association between advanced prehospital airway management and worse clinical outcomes in patients with cardiac arrest. Done in Japan, the numbers of patients included are staggering: this nationwide population-based cohort study included 658 829 adult patients. They found that CPR with advanced airway management (use of tracheal tubes and even supraglottic airways) was a significant predictor of poor neurological outcome compared with conventional bag-valve-mask ventilation.

Association of Prehospital Advanced Airway Management With Neurologic Outcome and Survival in Patients With Out-of-Hospital Cardiac Arrest
JAMA 2013;309(3):257-66


Importance It is unclear whether advanced airway management such as endotracheal intubation or use of supraglottic airway devices in the prehospital setting improves outcomes following out-of-hospital cardiac arrest (OHCA) compared with conventional bag-valve-mask ventilation.

Objective To test the hypothesis that prehospital advanced airway management is associated with favorable outcome after adult OHCA.

Design, Setting, and Participants Prospective, nationwide, population-based study (All-Japan Utstein Registry) involving 649 654 consecutive adult patients in Japan who had an OHCA and in whom resuscitation was attempted by emergency responders with subsequent transport to medical institutions from January 2005 through December 2010.

Main Outcome Measures Favorable neurological outcome 1 month after an OHCA, defined as cerebral performance category 1 or 2.

Results Of the eligible 649 359 patients with OHCA, 367 837 (57%) underwent bag-valve-mask ventilation and 281 522 (43%) advanced airway management, including 41 972 (6%) with endotracheal intubation and 239 550 (37%) with use of supraglottic airways. In the full cohort, the advanced airway group incurred a lower rate of favorable neurological outcome compared with the bag-valve-mask group (1.1% vs 2.9%; odds ratio [OR], 0.38; 95% CI, 0.36-0.39). In multivariable logistic regression, advanced airway management had an OR for favorable neurological outcome of 0.38 (95% CI, 0.37-0.40) after adjusting for age, sex, etiology of arrest, first documented rhythm, witnessed status, type of bystander cardiopulmonary resuscitation, use of public access automated external defibrillator, epinephrine administration, and time intervals. Similarly, the odds of neurologically favorable survival were significantly lower both for endotracheal intubation (adjusted OR, 0.41; 95% CI, 0.37-0.45) and for supraglottic airways (adjusted OR, 0.38; 95% CI, 0.36-0.40). In a propensity score–matched cohort (357 228 patients), the adjusted odds of neurologically favorable survival were significantly lower both for endotracheal intubation (adjusted OR, 0.45; 95% CI, 0.37-0.55) and for use of supraglottic airways (adjusted OR, 0.36; 95% CI, 0.33-0.39). Both endotracheal intubation and use of supraglottic airways were similarly associated with decreased odds of neurologically favorable survival.

Conclusion and Relevance Among adult patients with OHCA, any type of advanced airway management was independently associated with decreased odds of neurologically favorable survival compared with conventional bag-valve-mask ventilation.

Point of care analysis of intraosseous samples

January 2, 2013 by  
Filed under All Updates, EMS, Resus

Some good news for remote, rural, prehospital, and retrieval medicine clinicians who rely on point of care testing with the i-STAT® device. An animal study confirmed the reliability of testing aspirates from intraosseous samples taken from the tibia(1).

This is also good news for hospital practitioners when it comes to the acquisition of blood gas results, since there are concerns over the potential damage to blood gas analysers by bone marrow contents in the samples.

The researchers tested blood gases, acid–base status, lactate, haemoglobin, and electrolytes, and compared these with results from an arterial sample.

There was no malfunction of the equipment. Most of the acid–base parameters showed discrepancies between arterial and osseous samples: the average pH and base excess were consistently lower whilst pCO2 and lactate were higher in the intraosseous samples compared to the arterial. However the overall small degree and predictable direction of discrepancy in these values should preserve the clinical usefulness of intraosseous gases if these findings can be replicated in human subjects. pO2 was obviously very different between osseous and arterial samples.

They noted that aspiration of intraosseous samples was generally straightforward, especially immediately after placement of the cannulae, but on a few occasions more forceful aspiration was needed. They point out that this could possibly cause cellular lysis and affect the potassium analysis.

The authors consider the issue of how much aspirate should be discarded before taking a sample after intraosseous cannula insertion, and refer to a prior study which suggested that 2mL is adequate.

Summary
  • Intraosseous aspirate can be tested on an i-STAT® point-of-care analyser
  • Haemoglobin and electrolytes show good correlation with arterial samples
  • Acid-base, pCO2, and lactate differ slightly from arterial results but in a predictable direction and results are still likely to be clinically useful in an emergency
  • It may be worth discarding the first 2 ml of aspirate
  • These results require validation in human subjects

Analysis of intraosseous samples using point of care technology–an experimental study in the anaesthetised pig
Resuscitation. 2012 Nov;83(11):1381-5


BACKGROUND: Intraosseous access is an essential method in emergency medicine when other forms of vascular access are unavailable and there is an urgent need for fluid or drug therapy. A number of publications have discussed the suitability of using intraosseous access for laboratory testing. We aimed to further evaluate this issue and to study the accuracy and precision of intraosseous measurements.

METHODS: Five healthy, anaesthetised pigs were instrumented with bilateral tibial intraosseous cannulae and an arterial catheter. Samples were collected hourly for 6h and analysed for blood gases, acid base status, haemoglobin and electrolytes using an I-Stat point of care analyser.

RESULTS: There was no clinically relevant difference between results from left and right intraosseous sites. The variability of the intraosseous sample values, measured as the coefficient of variance (CV), was maximally 11%, and smaller than for the arterial sample values for all variables except SO2. For most variables, there seems to be some degree of systematic difference between intraosseous and arterial results. However, the direction of this difference seems to be predictable.

CONCLUSION: Based on our findings in this animal model, cartridge based point of care instruments appear suitable for the analysis of intraosseous samples. The agreement between intraosseous and arterial analysis seems to be good enough for the method to be clinically useful. The precision, quantified in terms of CV, is at least as good for intraosseous as for arterial analysis. There is no clinically important difference between samples from left and right tibia, indicating a good reproducibility.

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