Category Archives: All Updates

Acute Med, All Updates, ICU, Resus

Use a table for selecting PEEP in ARDS

Leave a comment

PEEPtable.001Selecting the right amount of PEEP to recruit collapsed alveoli in patients with ARDS is important but the best method isn’t proven. Using a table to select PEEP based on FiO2 was significantly but weakly associated with improved lung recruitability (on CT scan) when compare with other methods of selecting PEEP, and was the best method for avoiding higher PEEP in patients with lower recruitability.
This is a small study and the results do not necessarily translate to improved clinical outcomes, but they may be of interest to emergency and retrieval medicine physicians who require a simple and safe strategy when managing ARDS patients without the luxury of time or of access to highly sophisticated ICU ventilators.
Bedside selection of positive end-expiratory pressure in mild, moderate, and severe acute respiratory distress syndrome
Crit Care Med. 2014 Feb;42(2):252-64
[EXPAND Abstract]


OBJECTIVE: Positive end-expiratory pressure exerts its effects keeping open at end-expiration previously collapsed areas of the lung; consequently, higher positive end-expiratory pressure should be limited to patients with high recruitability. We aimed to determine which bedside method would provide positive end-expiratory pressure better related to lung recruitability.

DESIGN: Prospective study performed between 2008 and 2011.

SETTING: Two university hospitals (Italy and Germany).

PATIENTS: Fifty-one patients with acute respiratory distress syndrome.

INTERVENTIONS: Whole lung CT scans were taken in static conditions at 5 and 45 cm H2O during an end-expiratory/end-inspiratory pause to measure lung recruitability. To select individual positive end-expiratory pressure, we applied bedside methods based on lung mechanics (ExPress, stress index), esophageal pressure, and oxygenation (higher positive end-expiratory pressure table of lung open ventilation study).

MEASUREMENTS AND MAIN RESULTS: Patients were classified in mild, moderate and severe acute respiratory distress syndrome. Positive end-expiratory pressure levels selected by the ExPress, stress index, and absolute esophageal pressures methods were unrelated with lung recruitability, whereas positive end-expiratory pressure levels selected by the lung open ventilation method showed a weak relationship with lung recruitability (r = 0.29; p < 0.0001). When patients were classified according to the acute respiratory distress syndrome Berlin definition, the lung open ventilation method was the only one which gave lower positive end-expiratory pressure levels in mild and moderate acute respiratory distress syndrome compared with severe acute respiratory distress syndrome (8 ± 2 and 11 ± 3 cm H2O vs 15 ± 3 cm H2O; p < 0.05), whereas ExPress, stress index, and esophageal pressure methods gave similar positive end-expiratory pressure values in mild, moderate, and severe acute respiratory distress syndrome. The positive end-expiratory pressure selected by the different methods were unrelated to each other with the exception of the two methods based on lung mechanics (ExPress and stress index).
CONCLUSIONS: Bedside positive end-expiratory pressure selection methods based on lung mechanics or absolute esophageal pressures provide positive end-expiratory pressure levels unrelated to lung recruitability and similar in mild, moderate, and severe acute respiratory distress syndrome, whereas the oxygenation-based method provided positive end-expiratory pressure levels related with lung recruitability progressively increasing from mild to moderate and severe acute respiratory distress syndrome.

[/EXPAND]

All Updates, ICU, Kids, PHARM, Resus

i-STAT® analysis of intraosseous aspirate

Leave a comment

In the absence of vascular access we may resort to sending intraosseous aspirates for analysis, but in some laboratories there is concern that the samples can block autoanalysers.
A study on haematology/oncology patients undergoing diagnostic bone marrow aspiration showed clinically acceptable agreement between venous and intraosseous measurements for pH, base excess, sodium, ionised calcium and glucose using an an i-STAT® point-of-care analyser.
Key points are:

  • The first 1-2 ml should be discarded (as in this study)
  • Lactate hasn’t been assessed
  • These patients weren’t critically ill

Analysis of bloodgas, electrolytes and glucose from intraosseous samples using an i-STAT® point-of-care analyser
Resuscitation. 2014 Mar;85(3):359-63
[EXPAND Abstract]


BACKGROUND: Intraosseous access is used in emergency medicine as an alternative when intravenous access is difficult to obtain. Intraosseous samples can be used for laboratory testing to guide treatment. Many laboratories are reluctant to analyse intraosseous samples, as they frequently block conventional laboratory equipment. We aimed to evaluate the feasibility and accuracy of analysis of intraosseous samples using an i-STAT(®) point-of-care analyser.

METHODS: Intravenous and intraosseous samples of twenty children presenting for scheduled diagnostic bone marrow aspiration were analysed using an i-STAT(®) point-of-care analyser. Sample types were compared using Bland Altman plots and by calculating intraclass correlation coefficients and coefficients of variance.

RESULTS: The handheld i-STAT(®)point-of-care analyser proved suitable for analysing intraosseous samples without technical difficulties. Differences between venous and intraosseous samples were clinically acceptable for pH, base excess, sodium, ionised calcium and glucose in these haemodynamically stable patients. The intraclass correlation coefficient was excellent (>0.8) for comparison of intraosseous and intravenous base excess, and moderate (around 0.6) for bicarbonate, sodium and glucose. The coefficient of variance of intraosseous samples was smaller than that of venous samples for most variables.

CONCLUSION: Analysis of intraosseous samples with a bedside, single-use cartridge-based analyser is feasible and avoids the problem of bone marrow contents damaging conventional laboratory equipment. In an emergency situation point-of-care analysis of intraosseous aspirates may be a useful guide to treatment.

[/EXPAND]

All Updates, Guidelines, ICU, Kids, PHARM, Resus

Is 4 Joules per kg enough in kids?

Leave a comment

glash-sim-paed-face-smResearchers from the Iberian-American Paediatric Cardiac Arrest Study Network challenge the evidence base behind defibrillation shock dose recommendations in children.
In a study of in-hospital pediatric cardiac arrest due to VT or VF, clinical outcome was not related to the cause or location of arrest, type of defibrillator and waveform, energy dose per shock, number of shocks, or cumulative energy dose, although there was a trend to better survival with higher doses per shock. 50% of children required more than the recommended 4J per kg and in over a quarter three or more shocks were needed to achieve defibrillation.
 
Shockable rhythms and defibrillation during in-hospital pediatric cardiac arrest
Resuscitation. 2014 Mar;85(3):387-91
[EXPAND Abstract]


OBJECTIVE: To analyze the results of cardiopulmonary resuscitation (CPR) that included defibrillation during in-hospital cardiac arrest (IH-CA) in children.

METHODS: A prospective multicenter, international, observational study on pediatric IH-CA in 12 European and Latin American countries, during 24 months. Data from 502 children between 1 month and 18 years were collected using the Utstein template. Patients with a shockable rhythm that was treated by electric shock(s) were included. The primary endpoint was survival at hospital discharge. Univariate logistic regression analysis was performed to find outcome factors.

RESULTS: Forty events in 37 children (mean age 48 months, IQR: 7-15 months) were analyzed. An underlying disease was present in 81.1% of cases and 24.3% had a previous CA. The main cause of arrest was a cardiac disease (56.8%). In 17 episodes (42.5%) ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT) was the first documented rhythm, and in 23 (57.5%) it developed during CPR efforts. In 11 patients (27.5%) three or more shocks were needed to achieve defibrillation. Return of spontaneous circulation (ROSC) was obtained in 25 cases (62.5%), that was sustained in 20 (50.0%); however only 12 children (32.4%) survived to hospital discharge. Children with VF/pVT as first documented rhythm had better sustained ROSC (64.7% vs. 39.1%, p=0.046) and survival to hospital discharge rates (58.8% vs. 21.7%, p=0.02) than those with subsequent VF/pVT. Survival rate was inversely related to duration of CPR. Clinical outcome was not related to the cause or location of arrest, type of defibrillator and waveform, energy dose per shock, number of shocks, or cumulative energy dose, although there was a trend to better survival with higher doses per shock (25.0% with <2Jkg(-1), 43.4% with 2-4Jkg(-1) and 50.0% with >4Jkg(-1)) and worse with higher number of shocks and cumulative energy dose.

CONCLUSION: The termination of pediatric VF/pVT in the IH-CA setting is achieved in a low percentage of instances with one electrical shock at 4Jkg(-1). When VF/pVT is the first documented rhythm, the results of defibrillation are better than in the case of subsequent VF/pVT. No clear relationship between defibrillation protocol and ROSC or survival has been observed. The optimal pediatric defibrillation dose remains to be determined; therefore current resuscitation guidelines cannot be considered evidence-based, and additional research is needed.

[/EXPAND]

All Updates

Modernising ED sedation practice with evidence

Leave a comment

I think some EDs still have an overcautious ‘ASA 1 or 2 only’ criterion for procedural sedation, which makes no sense whatsoever when one considers the spectrum of cases in which emergent procedural sedation may be required.
Fortunately, the assumption that a higher ASA grade would be associated with increased complications has now been debunked by Edinburgh’s Emergency Medicine Research Group.
For more procedural sedation-related dogmalysis (such as pre-procedural fasting) check out EMCrit’s Practical Evidence Podcast that discusses the recently updated ACEP Policy.
Dawson, N., Dewar, A., Gray, A., Leal, A., on behalf of the Emergency Medicine Research Group, Edinburgh. (2014).
Association between ASA grade and complication rate in patients receiving procedural sedation for relocation of dislocated hip prostheses in a UK emergency department.
Emergency Medicine Journal 31(3), 207–209


OBJECTIVE: To determine the association between the American Society of Anesthiologists (ASA) grade and the complication rate of patients receiving procedural sedation for relocation of hip prosthesis in an adult emergency department (ED) in the UK.

DESIGN: Retrospective study of registry data from a large UK teaching hospital ED. Consecutive adult patients (aged 16 years and over) in whom ASA grade could be calculated, with an isolated dislocation of a hip prosthesis between 8 September 2006 and 16 April 2010 were included for analyses (n=303). The primary outcome measure was association between ASA and complication rate (any of desaturation <90%; apnoea; vomiting; aspiration; hypotension <90 mm Hg; cardiac arrest). Secondary outcome measures were relationship between ASA grade and procedural success, choice of sedative agent and sedation depth, and complications and choice of sedative agent, arrival time and sedation depth.

RESULTS: There was no significant difference between ASA grade and the risk of complication (p=0.800). Moreover, there was no significant difference between ASA grade and procedural success (p=0.284), ASA and choice of sedative agent (p=0.243), or ASA and sedation depth (p=0.48). There was no association between complications and sedative agent (p=0.18), or complications and arrival time (p=0.12). There was a significant difference between sedative depth and complications (p<0.001).

CONCLUSIONS: There is no clear association between a patient’s physical status (ASA grade) and the risk of complications, chance of procedural success or choice of sedative agent in relocation of hip prostheses. There is a higher rate of complications with higher levels of sedation (p<0.001).

Acute Med, All Updates, ICU, PHARM, Resus

The 'Magic Eye®' method of rhythm assessment

Leave a comment

Are you someone who tries to determine whether an ECG trace is ‘irregularly irregular’ by drawing little dots on a piece of paper level with the R waves to see if they are evenly spaced? I’d done that for years until I read this fantastic suggestion, which I’ve been following for over a year now.
In the 1990s there was a popular series of posters and books called ‘Magic Eye‘. These contained a ‘random dot autostereogram‘ which appeared as a mish-mash of coloured dots, but when you stared at it for a while the illusion of a 3D image would emerge. They looked a bit like this (although this one won’t work at such reduced resolution):

Image Credit: Wikimedia Commons
Image Credit: Wikimedia Commons

Dr Broughton and colleagues from Cambridge, UK, discovered that this technique, which involves forcing a divergent gaze to get repeating patterns to appear to overlap, can be applied to an ECG trace.
Stereoviewing an ECG trace causes successive QRS complexes to visually overlap and produce a new image. As Broughton and colleagues point out:
“When achieved, this will lead to one of three outcomes. Entirely regular rhythms will ‘click’ into place as a new image at fixed depth. Rhythms with only mild irregularity may be stereoviewable, and if so, will appear to show successive QRS complexes at subtly varying depths. Rhythms with marked irregularity will not be stereoviewable, instead (in our experience) merely giving the viewer sore eyes after several failed viewing attempts.”
The authors assert that this can be applied to continuous ECG monitors, although unless you are really good at stereoviewing while moving your head/eyes horizontally, you should really freeze the trace on the screen first.
The ‘Magic Eye®’ method of rhythm assessment
Anaesthesia. 2012 Oct;67(10):1170-1

Acute Med, All Updates, PHARM, Resus

Not finding a difference doesn't prove equivalence

Leave a comment

Image from http://www.physio-control.com/
The recent LINC trial was a randomised controlled trial comparing a mechanical chest compression device (LUCAS) with manual CPR(1). “No significant difference” was found for any of the main outcome measures considered.
So do you think the LINC trial demonstrated that mechanical CPR using the LUCAS device is equivalent, or at least not inferior, to manual CPR?
This was an interesting and important trial for those of us who manage prehospital cardiac arrest patients. In some social media discussions, it appears to have been interpreted by some as evidence that they are equivalent resuscitative techniques or that LUCAS is not inferior to manual CPR.

LINCdata

However, unless you see a p-value less than 0.05 in the table above, (issues of multiple hypotheses testing aside) no evidence of anything was demonstrated; not of difference and certainly not of equivalence. When faced with 2-sided p values >5%, investigators often conclude that there is “no difference” between the treatments, leading to an assumption among readers that the treatments are equivalent. A better conclusion is that there is “no evidence” of a difference between treatments (see opinion piece by Sackett, 2004(2)). In order to determine if treatments are equivalent, equivalence must be tested directly.
How can we test for equivalence?
First, we must define equivalence. It is crucial that this definition is provided a priori i.e. defined before the data are examined. As the focus of the LINC study was on superiority the investigators did not offer an a priori definition of equivalence. However, the CIRC study(3), conducted some time earlier and similar in design, did. (This study examined an alternative mechanical CPR device, the Zoll AutoPulse).
When establishing equivalence between treatments, instead of the more customary null hypothesis of no difference between treatments, the hypothesis that the true difference is equal to a specified ‘delta’ (δ) is tested (4).
To analyse the LINC results to look for equivalence, we can derive our delta values from the CIRC study, which as we’ve said did offer an a priori definition of equivalence. For the purpose of illustration, we will use the risk-difference stopping boundaries calculated for the CIRC study, rather than the odds ratio based equivalence margins, on the grounds of greater simplicity and clinical appropriateness. Therefore, we set our equivalence margins at -δ=-1.4% and δ=1.6%, meaning, where LUCAS fared no worse than manual CPR by 1.4% and no better by 1.6%, we will consider the two techniques equally efficacious. Thus, we will declare equivalence between LUCAS and manual CPR if the 2-sided 95% CI for the treatment difference lies entirely within -1.4% and 1.6%, and noninferiority if the one-sided 97.5% CI for the treatment difference (equivalent to the lower limit of the two-sided 95% CI) lies above -1.4%. (5).
These concepts and how they differ from a traditional comparison are more readily appreciated graphically (Fig. 1).
Figure 1. Two one-sided test procedure and the equivalence margin in equivalence/noninferiority testing between LUCAS and manual CPR
1a Traditional comparative study, such as the LINC trial, shows results with confidence intervals that show no evidence of a difference as they encompass 0.

LINCtradcomp

1b. Using equivalence margins (-δ and δ) derived from a similar study (CIRC), we show that the LINC trial does not demonstrate that LUCAS and manual CPR are equally efficacious, since the 95% CI do not lie completely within the equivalence margins.

LINCequiv
1c. The one sided CI lies above -δ for some outcomes, allowing us to declare non-inferiority on those measures.
LINCnoninf

Conclusion
The presentation of the LINC trial’s results shows no evidence of a difference in outcomes between mechanical and manual CPR, which is not the same as showing they are equivalent or that mechanical CPR is non-inferior. However if we re-examine their data using equivalence margins (-δ, δ) derived from a similar study (CIRC), there is some evidence that the LUCAS device is not inferior to manual CPR (but not necessarily equivalent) with respect to longer term good neurological outcome.

References
1. Rubertsson S, Lindgren E, Smekal D, er al. Mechanical Chest Compressions and Simultaneous Defibrillation vs Conventional Cardiopulmonary Resuscitation in Out-of-Hospital Cardiac Arrest
JAMA. 2014 Jan 1;311(1):53-61
2. Sackett D. Superiority trials, non-inferiority trials, and prisoners of the 2-sided null hypothesis
Evid Based Med 2004;9:38-39 [Open Access]
3. Lerner EB, Persse D, Souders CM, et al. Design of the Circulation Improving Resuscitation Care (CIRC) Trial: a new state of the art design for out-of-hospital cardiac arrest research
Resuscitation. 2011 Mar;82(3):294-9
4. Dunnett CW, Gent M. Significance testing to establish equivalence between treatments, with special reference to data in the form of 2X2 tables. Biometrics. 1977 Dec;33(4):593-602
5. Piaggio G, Elbourne DR, Pocock SJ, et al. Reporting of noninferiority and equivalence randomized trials: extension of the CONSORT 2010 statement. JAMA. 2012;308(24):2594-604. [Open Access]

Acute Med, All Updates, ICU, Resus, Ultrasound

Does RV enlargement on echo predict PE?

Leave a comment

A nice paper from Annals of Emergency Medicine showing the test characteristcs of some of the common signs we look for on basic 2D echo that suggest the presence of (sub)massive pulmonary embolism:
Right Ventricular Dilatation on Bedside Echocardiography Performed by Emergency Physicians Aids in the Diagnosis of Pulmonary Embolism
Ann Emerg Med. 2014 Jan;63(1):16-24
[EXPAND Abstract]


STUDY OBJECTIVE: The objective of this study was to determine the diagnostic performance of right ventricular dilatation identified by emergency physicians on bedside echocardiography in patients with a suspected or confirmed pulmonary embolism. The secondary objective included an exploratory analysis of the predictive value of a subgroup of findings associated with advanced right ventricular dysfunction (right ventricular hypokinesis, paradoxical septal motion, McConnell’s sign).

METHODS: This was a prospective observational study using a convenience sample of patients with suspected (moderate to high pretest probability) or confirmed pulmonary embolism. Participants had bedside echocardiography evaluating for right ventricular dilatation (defined as right ventricular to left ventricular ratio greater than 1:1) and right ventricular dysfunction (right ventricular hypokinesis, paradoxical septal motion, or McConnell’s sign). The patient’s medical records were reviewed for the final reading on all imaging, disposition, hospital length of stay, 30-day inhospital mortality, and discharge diagnosis.

RESULTS: Thirty of 146 patients had a pulmonary embolism. Right ventricular dilatation on echocardiography had a sensitivity of 50% (95% confidence interval [CI] 32% to 68%), a specificity of 98% (95% CI 95% to 100%), a positive predictive value of 88% (95% CI 66% to 100%), and a negative predictive value of 88% (95% CI 83% to 94%). Positive and negative likelihood ratios were determined to be 29 (95% CI 6.1% to 64%) and 0.51 (95% CI 0.4% to 0.7%), respectively. Ten of 11 patients with right ventricular hypokinesis had a pulmonary embolism. All 6 patients with McConnell’s sign and all 8 patients with paradoxical septal motion had a diagnosis of pulmonary embolism. There was a 96% observed agreement between coinvestigators and principal investigator interpretation of images obtained and recorded.

CONCLUSION: Right ventricular dilatation and right ventricular dysfunction identified on emergency physician performed echocardiography were found to be highly specific for pulmonary embolism but had poor sensitivity. Bedside echocardiography is a useful tool that can be incorporated into the algorithm of patients with a moderate to high pretest probability of pulmonary embolism.

[/EXPAND]

All Updates

How You Train is How You Fight

Leave a comment

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

Acute Med, All Updates, ICU, Resus

Sepsis research – let's get some answers

Leave a comment

There’s so much debate on which components of Early Goal Directed Therapy in sepsis really make a difference. The good news is that three randomised controlled trials in the UK, Australasia, and North America, aim to answer the question, and the study design from the outset has been a collaboration that will allow the results to be pooled.
ProMISe is taking place in the UK, ProCESS in the US, and ARISE in Australasia.

sepsistrialssm

The Australasian study (ARISE) and is nearing completion. If you can recruit patients then please do. Listen to a podcast on this fantastic study with lead investigator Dr Anthony Delaney.

All Updates, ICU, PHARM, Resus, Trauma

London Trauma Conference Day 4

Leave a comment

London Trauma Conference Day 4 by Dr Louisa Chan
It’s the last day of the conference and new this year is the Neurotrauma Masterclass running in parallel with the main track which focuses on in-hospital care.
We heard a little from Mark Wilson yesterday. He believes we are missing a pre-hospital trick in traumatic brain injury. Early intervention is the key (he has data showing aggressive intervention for extradural haemorrhage in patients with fixed dilated pupils has good outcomes in 75%).
Today he taught us neurosurgery over lunch. If you have a spare moment over then go to his website and you too can learn how to be a brain surgeon!
Dr Gareth Davies talks about Impact Brain Apnoea. Many will not heard of this phenomenon. Clinicians rarely see patients early enough in their injury timeline to witness
Essentially this term describes the cessation of breathing after head injury. It has been described in older texts (first mentioned in 1894!) The period of apnoea increases with the severity of the injury and if non fatal will then recover to normal over a period of time. Prolonged apnoea results in hypotension.
This is a brain stem mediated effect with no structural injury.
The effect is exacerbated by alcohol and ameliorated by ventilatory support during the apnoeic phase.
Associated with this response is a catecholamine surge which exacerbates the cardiovascular collapse and he introduces the concept of Central Shock.
So how does this translate into the real world?
Well, could we be miscategorising patients that die before they reach hospital as succumbing to hypovolaemic when in fact they had central shock?
These patients essentially present with respiratory arrest, but do well with supported ventilation. Identification of these patients by emergency dispatchers with airway support could mean the difference between life and death.
Read more about this at: http://www.sciencedirect.com/science/article/pii/S0025619611642547
Prof Monty Mythen spoke on fluid management in the trauma patient after blood (not albumin, HES or colloids) and Prof Mervyn Singer explained the genetic contribution to the development of MODS after trauma.
LTC-BrohiProf Brohi gave us the lowdown on trauma laparotomies – not all are the same! With important human factors advice:
1. Task focus kills
2. Situational awareness saves lives
3. The best communication is non verbal
4. Train yourself to listen
Prof Susan Brundage is a US trauma surgeon who has been recruited into the Bart’s and the London School of Medicine and the Royal College of Surgeons of England International Masters in Trauma Sciences for her trauma expertise.
She tells us that MOOCs and FOAM are changing education. Whilst education communities are being formed, she warns of the potential pitfalls of this form of education with a proportion of participants not fully engaged.
The Masters program is growing and if you’re interested you can read more here.
This has been a full on conference, with great learning points.
Hopefully see you next year!