Outline the methods available to estimate fluid balance in the critically ill patient and briefly discuss their advantages and limitations. (You may tabulate your answer).
Method |
Advantages |
Limitations |
Clinical – oedema, JVP, |
Simple, easily done by the |
Lack specificity |
Intake–output chart |
Simple method, reasonably |
Labour intensive, |
Body-weight |
May be useful in |
Not routinely used in all |
CVP/ PCWP/Echo |
Used to predict |
Significant limitations |
EVLW |
Shown to be of value in a trial comparing it with PAC |
Invasive technique |
Research methods include |
Research tools, do not lend |
This tabulated reponse is difficult to improve upon. It is reasonably comprehensive, and it remains within the realms of the achievable for a crazed exam candidate.
The college answer seems to ask about the estimation of total body water, rather than any other sort of fluid-related assessment. The candidate who carried on about estimation of fluid responsiveness would have been penalised.
The table mentioned above could be treated in a slightly more granular fashion, and I will attempt to do this with some references, expanding on some omitted details (for instance, it is perhaps insufficiently enlightening to simply say that the pulmonary artery catheter and CVP have "significant limitations").
Method |
Advantages |
Disadvantages |
Clinical estimates |
|
|
Fluid balance chart |
|
|
Daily weights |
|
|
CVP |
|
|
PAWP |
|
|
TTE |
|
|
PAC or PiCCO EVLW |
|
|
Bioimpedance |
|
|
Tritium indicator dilution |
|
|
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