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
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
A diagnostic observational study.
19 Intensive care patients with septic shock and non-liable blood pressure
2 French Intensive care unit in
Left ventricle end-diastolic area and peak velocity of flow of blood through aorta.
Cardiac index as measured via echocardiography
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
In mechanically ventilated septic shock patients, the end diastolic left ventricle volume is strongly related to effects of volume expansion on cardiac output.
· Standardised patient groups
· Reasonable exclusion criteria
· Gold standard is well described and appropriate
· 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
· Causes of sepsis and definition widely used therefore more generalisable
· Use of starch (now outdated)
· Transoesophageal echo not a very widespread skill
· Only a single unit trial and small number of patients
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.