Wednesday, January 4, 2012

Is the glass half empty or half full?

Recently, we were asked to see a patient on the consult service with a rising creatinine, a BUN of close to 200 and decreased urine output. The patient was a diabetic who had an STEMI several months previously complicated by pneumonia and cardiogenic shock. He was cachectic, did not have any edema or ascites and because of his trach-collar, I put “unable to assess JVD” in my note. His BUN had been high (above 100) for more than 4 weeks (not on TPN, steroids, no GI bleeding) as he was aggressively diuresed for heart failure and his creatinine had been rising slowly which, given his low muscle mass, indicated a significant reduction in GFR. My attending also assessed the patient and felt that his JVP was elevated and recommended diuresis. The primary team, in contrast, felt that his JVP was low and they recommended fluids. The assessment of the JVD is a notoriously difficult exam and very hard to master if one does not do it appropriately as described in a previous post. The patient received 2 liters of fluid and his cardiac status worsened so he was started on dialysis several days later for worsening renal function and volume removal.

This case illustrates the difficulty in accurately assessing volume status in patients in general.

When was the last time you assessed a JVD comfortably? We often say "this patient is dry" or that he needs diuresis but how accurate are our assessments based on the clinical exam alone?

A previous post discussed the JVP and its use as a tool for volume status assessment and cited a systematic review stating that there is a “poor relationship between the isolated inspection of CVP and prediction of blood volume and fluid responsiveness.” One of my attendings gave me an article on this topic several weeks ago: "Clinical assessment of extracellular fluid volume in hyponatremia". The article assessed the clinical judgment of volume status by one of the authors (including cardiac parameters, JVP, orthostatic changes, skin turgor, moisture in the axillae, hydration of mucous membranes) and volume status was 'objectively' assessed by spot urine samples of sodium and creatinine and BUN, norepinephrine and plasma renin concentrations. The clinical assessment was only able to identify 47 % of hypovolemic patients and 48% of normovolemic patients whereas the spot urine sodium clearly separated hypovolemic from normovolemic patients.

The "Bible" of physical examination - Evidence Based Physical Diagnosis by Steven McGee - attributes a low sensitivity or specificity or both to the most common findings used when assessing hypovolemia (the highest likelihood ratio was 2.8 for a dry axilla; in contrast, dry mucous membranes, tongue furrows, sunken eyes, confusion, weakness or unclear speech did not have a significant likelihood ratio). Capillary refill time has been compared only once to a diagnostic standard and was found to have no diagnostic significance.

An intriguing series in JAMA about the rational physical exam stated in the conclusion that "in patients with vomiting, diarrhea, or decreased oral intake, few findings have proven utility, and clinicians should measure serum electrolytes, serum blood urea nitrogen, and creatinine levels when diagnostic certainty is required."

The bottom-line I learned from all of this is: our examination at the bedside is notoriously unreliable in making accurate statements about a patient's volume status and objective parameters need to be taken into account to get a complete picture. A previous post discussed the use of urine electrolytes as a more objective tool for assessing volume status in addition to clinical examination.

Posted by Florian Toegel


Francesco Iannuzzella said...

In this setting, bioimpedance analysis may be helpful, particularly in pts on diuretic therapy. Both single and multiple frequency BIA may be adopted at the bedside. SF-BIA may be used to monitor volume status changes during fluid administration. MF-BIA provides rapidly available information on volume status and body composition. Yet, do not forget CXR.

Anonymous said...

Another article trying to debunk physical examination.

Trying to attach evidence base to physical examination is a circular argument. We have trained a generation of physicians who are incompetent in physical exam and then use them to generate 'evidence' for physical exam.

This is a self fulfilling prophecy. As times gone and this skill dies one can generate more evidence that physical exam is useless. And then continue teaching that there is no evidence that physical exam is useful!!

On another note... there are older and better 'Bibles' for physical exam. One such 'Bible' is Hutchison's Clinical Methods. This is a 100 year old 'Bible'!!

Anonymous said...

Agree with previous comment. Physical exam of volume status is difficult and needs careful mastery of techniques. We rarely taught our trainees as we don't know ourselves. Most of us who do more than half of time in basic research don't have time to master these techniques. When done with right set of clinical data and urine chemistry physical exam including JVD is remarkably useful and easy to perform. Let's not forget use of FeUrea, very useful but forgotten urinary indice.

Just not forget the time spent in performing physical exam is also time directly observing patient, time getting non verbal clues and opportunity to talk to housestaff and nurses caring for patients. This is one area of medicine which makes me humble everyday and I am constantly trying to improve.

Anonymous said...

Having trained in countries where physical exam is a significant part of the training curriculum, (and Hutchison's clinical methods was indeed the Bible!) I agree with the author about the difficulties in accurate assessment of volume status, especially the intravascular volume status in obese, malnourished, edematous patients with cardiac dysfunction. Just as in the case described, you debate about diuresis vs fluid almost everyday!

Anonymous said...

This is an interesting article pertaining to the topic under discussion:

Anonymous said...

In 201X I find insufficient relying just on physical examination to assess a patient's volume status.

I find very useful an ultrasonographic examination, which is an easy and fast (for trained physicians of course) way to obtain accurate informations i.e.

- The presence of Lung Comets to diagnose Interstitial Syndrome and fluid overload
- Inferior Vena Cava with the substernal approach in TTE
- The presence of Pleural Effusions bilaterally (US is much more Sensitive than Standard Chest X Ray)

Anonymous said...

This is one of the most frustrating issues around in clinical medicine. Just my two cents:

1) I agree completely with one of the comments - poor teaching of physical exam means more evidence for it being useless.

2) The "objective" electrolytes often don't help - i.e. a low FENa or FEurea is due to low effective circulating volume which may be due to congestion (give diuretics) or overdiuresis (give fluid or hold diuretics).

3) The JVP may be best assessed with the patient sitting up. This essentially gets rid of the sternal angle to RA distance issue. If its above the clavicle sitting up, its elevated.

4) Physical signs such as turgor, dry mucous membranes, dry axilla, etc. are measuring different things. Turgor and possibly tongue furrows measure interstitial fluid - these are theoretically useful for hypovolemia but may not be as much in CHF given the probable alteration in intersitial-vascular dynamics (ofcourse the usual age related decline in skin turgor is another issue as well). The other signs are essentially markers for ADH - hence they are more sensitive for hypernatremia than for volume depletion.

JMLAWMD said...

Although still a nephrologist I spend most of my time in critical care. Accurate assessment of volume status is crucial in this setting. I have found US evaluation of the IVC and internal jugular vein to be incredibly helpful and quite easy to master if done frequently.