Jugular Venous PRESSURE- so why do we use it to assess volume?

There is perhaps no physical exam sign more enthused about by consultants and more bluffed by students than the jugular venous pressure (JVP). While initially I was not a believer, I have come recently to appreciate its usefulness. This epiphany did not occur without significant time spent perusing the literature and finally coming to understand what the JVP does and does not tell you.

The first point to make abundantly clear is that JVP is simply a surrogate for central venous pressure (CVP). This roughly estimates the right atrial pressure. The obvious first question a sceptic would ask is how good a job it does at this?

Well, if we refer to the JAMA rational clinical exam series from 2009 (1), a systematic review of sorts on different examination findings, we see that the JVP, and hepatojugular reflux, correlates reasonably well with invasively measured CVP. The table of likelihood ratios below combines findings from the three studies addressing this question, including one where hilariously medical students were better at estimating CVP than staff physicians.

JVP
Credit: Reference (1)

When it comes to the diagnosis of left sided ventricular dysfunction in a dyspneic patient, the JVP has a high positive likelihood ratio of 5.1, and an OK negative likelihood ratio of 0.66. Hepatojugular reflux has an even higher positive likelihood ratio of 6.4 (1). In another review (2) JVP was found to have excellent specificity and sensitivity in the detection of elevated left atrial pressure (which is an estimate of left ventricular filling pressure), which is elevated in left ventricular dysfunction.

So there we have it; JVP is correlated with central venous pressure and is helpful in the diagnosis of heart failure. So what exactly is the point of this blog post?

The point is that somewhere along the way, in a move that would make a physicist balk, people started using the JVP as a surrogate for volume. The everyday applications for the JVP seem to be along the lines of “the JVP is low, he needs more fluid” or “the JVP is high, we can’t give fluid, or we need to give more frusemide”.

This 2013 systematic review (3) analysing 43 studies pretty conclusively demonstrates nearly zero correlation between the central venous pressure or the change in central venous pressure with fluid administration and blood volume. There is also no correlation between CVP and fluid responsiveness (defined as increase in cardiac output or stroke volume with fluid administration). This rather famous study led to widespread abandonment of CVP monitoring in many ICUs. Although studies directly correlating clinical JVP with volume status are difficult to come by, the one I could find (4) concluded the same thing.

It makes physiologically no sense to use the JVP, a pressure indicator, solely to guide volume assessment. It would be rather like seeing a high reading on your fuel pressure gauge, and assuming that your vehicle had somehow acquired too much fuel in the tank. There is a missing link between volume and pressure, and that is the compliance of the venous system, which can vary dramatically in different physiological states. In fact, in a healthy person the venous system contains 70% of blood volume. Other factors that affect the central venous pressure include ventricular function and compliance, intrathoracic pressure, pericardial pressure, and pulmonary arterial pressure (5).

This is why the JVP is helpful in heart failure- not because it indicates hypervolemia, but because it indicates elevated filling pressures from low cardiac output (even in left ventricular failure elevated left sided filling pressures are often transmitted to right sided pressures (2,5)).

For sure the JVP is a useful clinical sign- but only when you take into account all the factors that affect it and remember that is an indicator of pressure, not volume. Therefore an elderly patient with cor pulmonale and a high JVP may still benefit from fluid in the right situation while a healthy 30 year old bloke with a low JVP may not need any fluid at all. “The only reason to give a fluid bolus is to cause a clinically significant increase in stroke volume” (6). Therefore what matters more than trying to guess someone’s volume status is to observe the effect of either fluid or diuresis on clinical parameters and re-evaluate your therapy frequently along the way.

 

References:

  1. Simel DL, Rennie D. The Rational Clinical Examination: Evidence-Based Clinical Diagnosis. JAMAevidence 2009.
  2. Rame JE, Dries DL, Drazner MH. The Prognostic Value of the Physical Examination in Patients With Chronic Heart Failure. CHF 2003;9(3).
  3. Crit Care Med. 2013 Jul;41(7):1774-81. doi: 10.1097/CCM.0b013e31828a25fd. Does the central venous pressure predict fluid responsiveness? An updated meta-analysis and a plea for some common sense. Marik PE1, Cavallazzi R.
  4. Malar J. 2013 Oct 1;12:348. doi: 10.1186/1475-2875-12-348. The reliability of the physical examination to guide fluid therapy in adults with severe falciparum malaria: an observational study. Hanson J1, Lam SW, Alam S, Pattnaik R, Mahanta KC, Uddin Hasan M, Mohanty S, Mishra S, Cohen S, Day N, White N, Dondorp A.
  5. Venous Function and Central Venous Pressure: A Physiologic Story. Simon Gelman, M.D. Ph.D. Anesthesiology 4 2008, Vol.108, 735-748. doi:10.1097/ALN.0b013e3181672607
  6. A rational approach to fluid therapy in sepsis . P. Marik Bellomo. BJA: British Journal of Anaesthesia, Volume 116, Issue 3, 1 March 2016, Pages 339–349.

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