Fancy intensive care echo

This very technical article is summarised better with the bottom line crew here

But If you wish to follow me trying to stumble through the murky world of critical care POCUS read on here is appraisal of a study looking to trans-oesophageal echo measurements and fluid responsiveness- A area I am currently trying to get my head around.

 

Respiratory Changes in Aortic Blood Velocity as an Indicator of Fluid Responsiveness in Ventilated Patients with Septic Shock

 

Feissel M1, Michard FMangin IRuyer OFaller JPTeboul JL.

 

Objectives

To investigate if changes in blood velocity secondary to respiratory and left ventricular end diastolic pressure can predict haemodynamic effects of fluid in septic patients as measured by transoesphageal echocardiography

Design

A diagnostic observational study.

Population

19 Intensive care patients with septic shock and non-liable blood pressure

Setting

2 French Intensive care unit in

Methods

Test

Left ventricle end-diastolic area and peak velocity of flow of blood through aorta.

Gold standard

Cardiac index as measured via echocardiography

Results

A linear relationship between peak velocity and response to fluid challenge (correlation of co-efficient of 0.83 and p <0.001) but end -diastolic volume was not (r2= 0.11 p value = 0.17). This led to sensitivity of 100% and specificity of 89% if threshold of 12 percent change in peak flow was used to identify non-responders to fluid

Conclusion

In mechanically ventilated septic shock patients, the end diastolic left ventricle volume is strongly related to effects of volume expansion on cardiac output.

 

Internal validity

Pros

·         Standardised patient groups

·         Reasonable exclusion criteria

·         Gold standard is well described and appropriate

 

Cons

·         No power calculation, difficult to comment on type 2 error

·         Correlation not causation

·         Same examiner taking both index test and gold standard, potential for bias

·         No clear primary outcome; potential to increased positively result by chance                       

 

 

External Validity

Pros

·         Causes of sepsis and definition widely used therefore more generalisable

 

Cons

·         Use of starch (now outdated)

·         Transoesophageal echo not a very widespread skill

·         Only a single unit trial and small number of patients

 

My conclusion

As I try and begin to decipher the world of intensive care the identification of fluid responders and non-responders seems difficult. This is one more method to add into the pile and suggests using trans-oesophageal echo can be useful if aortic flow can be identified. However, I am not sure the effort in skill investment is worth it quite yet when there are other methods which are less invasive and require less specialist skill.

Shock and POCUS

So, after attend a course in critical appraisal (the “Brighton” method) and with an exam coming up I bring you a more structured criticism of a very interesting paper.

 

Randomized, controlled trial of immediate versus delayed goal-directed ultrasound to identify the cause of nontraumatic hypotension in emergency department patient

https://www.ncbi.nlm.nih.gov/pubmed/15286547

Bottom line; Ultrasound is useful in undifferentiated shock.

Objective

To examine if focused bedside ultrasound could narrow the differential diagnosis in undifferentiated non traumatic shock

Design

A randomised “quasi cross over” controlled trial

Setting

Urban 800 bed teaching hospital’s emergency department

Population

202 Adult patients presenting to the emergency department with systolic bp <100 and a symptoms suggested acute pathology.

Method

Subjects randomised either to standard care or standard care with ultrasound assessment. A list of diagnosis was suggested at 15 minutes. The control group then received focused ultrasound at 15 minutes. A second revised list of diagnosis was suggested.  

Intervention

Bedside focused ultrasound

Control

Standard care

Outcome

Primary outcome measure was accuracy of initial diagnosis as compared to a panel of experts with pre-defined definitions

Results

In intervention group correct diagnosis obtained in 80% (CI 70-87) and in the control group 50% (CI 40-60%). A significant absolute difference of 30 %. After cross over with ultrasound correct diagnosis increased to 78%

Conclusion

That early goal directed ultrasound can positively affect the differential diagnosis for undifferenced shock.

 

Internal Validity

Strengths

·         Creative use of cross over designed helped to reduce bias that could have occurred from differences between intervention and control group. Also, as pointed out in conclusion, allowed ethically for all the get presumed best treatment (ultrasound)

·         Use of absolute risk reduction; less data manipulation occurred.

·         Power calculation undertaken

·         It could be argued primary outcome was patient orientated- knowledge of diagnosis important

·         Pragmatic exclusion criteria excluded those with obvious cause of shock

·         Randomisation eliminating cofounding factors.

Weaknesses

·         Could have used secondary measurements of “hard “outcomes i.e. mortality to ensure correct diagnosis helped patient outcome. Did point out that lack of previous studies to demonstrate this.

·         Single centre study in the United States, lack of generalisability.

·         Somewhat subjective enrolment criteria could have led to allocation bias.

·         Unable to blind treating physician or patient by definition- however study design accounted for this.

 

External validity

Strengths

·         Use of broad range of doctors who were not “experts “in ultrasonography- had levels similar to FICE in the UK.

·         Mixed of diagnosis seemed fairly similar to what we see locally

·         Study use residents, not being 100 % familiar with the system I assume this is roughly analogues with middle grades, a pragmatic approach.

Limitations

·         Amount of time taken not documented – this can be a significant limiting factor in UK emergency departments.

·         use of 100 systolic blood pressure as cut off- definition of shock used is generally 90 systolic

·         level of ultrasound skill significant above that of the average emergency doctor in the UK. This would need significant training to be widely adopted as practice.

 

Conclusion

This is a interested study highlighting the utility of ultrasound in a specific cohort of patients. Those who are not arrested and have no clear cause of shock. I would to see this study replicated in other populations and like to know the frequency of this type of patient attending our department before embarking on the significant challenge of up skilling UK emergency department doctors. However, from a personal perspective in prompts me to continue to improve my bedside echo in the shocked patient as this is the most challenging of the ultrasonographic views obtained.

Maybe slightly less painful the worthing way

I have struggled with haematoma blocks, they seem a bit variable. A ongoing straw poll seems my senior colleges seem to also have variable opinions of these. 

Sometimes those colles' fractures are reduced without a bother, sometimes they seem to cause a unacceptable amount of pain. 

I think the age of Bier's block has gone, I have only learnt about them in exams and never seen one. 

Maybe there's another way, no full on studies, but a well described procedure to guide that needle into the haematoma. Again, it just makes sense, why guess when you can see you way in?

But anyway, the times I tried this I have largely failed to actually see the needle, but everyone was very impressed with my fancy machine and until shawn teaches me this probably I have to rely on the powerful placebo of posh technology. . . but hey that the most powerful analgsic going.

pain free the Worthing way

The research I want to be linking to here doesn't exist. I wish I was linking to a double blinded randomised control trial comparing ultrasound guided fascia illiac block to the "pop pop " anatomical method. But it doesn't exist (yet)

Instead this article is a pilot comparing the two, so maybe soon. 

However it does suggest with some more people in the study it could have prove this. So why I am bothering to write about a pilot study. Well, for me, it instinctively makes sense in our lovely local A/E ultrasound blocks are the way to go. 

The fascia illiac block is a distributive block; this means you need a large volume to be effective. I am nervous about injected more than 20mls with the pop pop method. It just feels wrong. However if I can visualize the needle going it and actually see the femoral nerve as well as the fascia illiac space expanding as I inject this has got to be better. 

If you are familiar with ultrasound (as we are all going to be after the launch of ultrasound club ), it isn't that difficult to undertake- a simple guide can be found here. Admitted it takes a little bit more time to rally the relevant equipment. But it all exists in the department currently

But considering our population, we are going to treat more and more elderly people with painful fractures. Hopefully the worthing way will be the most effective analgesia possible. 

 

Why is this elderly chap more short of breath. . .

Welcome to my first blog post on some evidence base behind Ultrasound. There is a lot out there in foam community. I have seen lots of sexy images of lives saved with echos demonstrating cardiac tamponade and the like. 

I do not see lots of tamponade in our local A/E. I've never seen a clam-shell thoractomy let alone done one. Most of us don't. What we do see is lots of Short of breath elderly people. This is our bread and butter, we deal with it well. Easy right?

One decision I find difficult is the old fluids vs furosemide dilemma. Is this patient septic and dry needing a little fluid. Or is this person heart failure slightly worse due to their chest infection and need a little more diuretic. I'm sure it ain't just me. 

This paper shows how the magical properties of Ultrasound can help (for those who have time to read full studies, here you go) 

This paper, and indeed this type of study was introduced by the fantastic chaps as resus rooms podcast. They basically meta-analyis compares history, examination, lab and radiological findings and see which of these are the most predictive of a certain decision. This is something that was not mentioned in medical school. Where all tests where created equal and only the "classical presentation" was mentioned. As A junior doc trying to make my mind up regarding if I should request this test and when it comes back what one earth I should do with it this type of study is really useful. 

The reality is very different. We are a little suspicions, we have a limited array of tests that can bump us to a more of less likely diagnosis, or we remain unsure and refer for help. But furosemide vs fluids cannot wait til the next morning. 

So this study demonstrated nicely that demonstrating lung fluid on the bedside ultrasound helps you the most in confirming acute heart failure. With a likelihood ratio of 7.4 (don't understand Likelihood ratios- you should- this changed the way I think about diagnosis- check out this article).

Basically if you find at effusion on lung ultrasound you can times the amount of suspicion you have by 7. Also makes logical sense, if you have fluid on the lungs, don't give them more fluid. This is significantly better than out standard cxr (which is pretty useful) for those old school docs. Disappointingly, ultrasonic B lines ain't as useful. 

Also it is easy. Just bang the probe on the lung bases and bob's your uncle. This isn't working out someone's ejection fraction on echo- which is both technically very difficult and less useful (according to this study).

Not the mention the possibility of confirming that pneumonia as well...  

There you have it, proof of a easy, bedside method to confirm a everyday clinical dilemma. Emergency ultrasound, an everyday useful tool.