Is there evidence of benefit from using non-invasive cardiac output monitors in particular ICU cohorts? From peoples experience, is there a particular variable or question that is answered well and conversely poorly with these monitors e.g. fluid status better, cardiac function etc.?


I’ll start with a deliberately provocative opinion.

Within the realms of general ICU there is little to no value in these devices other than to the shareholders of the companies. I’m am not aware of any solid data to show improved outcome on ICU (happy to be corrected).Some are validated against PAC’s, which themselves have not been shown to improve outcome, some aren’t even consistent with that low bar.
Straight leg raise +/- FICE. Cheap, effective and accessible.
I do not think I have ever seen anyone change their mind when a NICOM provides numbers that run contrary to their clinical judgement.
I like this question!

Evidence? No, none that I’ve seen.
My use of these monitors over the years has been purely to measure (and occasionally try to predict) volume responsiveness.  I doubt we’ll ever see a RCT that tries to link this application to outcomes, as it forms just a small part of overall ICU management.  However, the physiology of this application is sound, and the likely consequence is that injudicious over-use of IV fluids will be avoided.
Over-transfusion of IV fluids is dangerous, and intensivists know this.  However, I still hear people say “I gave the patient 6 litres of fluid and didn’t see much difference”.  The possibility that 5 of those litres could have caused harm should concern us, and avoidance of that harm is sometimes made easier if we use a schema to diagnose euvolaemia.  A cardiac output monitor may help with this.  Personally, I have decided that I can diagnose euvolaemia without one.

I’m with A on this one.

What actually happens- “Put the LidCO on” = Take a really sick patient and give the nurse even more to do, then completely ignore the information it gives you.

What should happen- Ongoing bedside assessment during resuscitation to achieve euvolaemia, then de-escalation.

I suspect that much of the time, the initial resuscitation phase is done prior to arrival on crit care by health care professionals who don’t necessarily understand the consequences of excessive volume administration.


May be I should take the other side of the debate. I think Jame Sira’s question itself is biased in that

a.”Evidence of benefit in non-invasive cardiac output monitors in particular ICU cohorts”- Already a belief that in general it is not beneficial for all but may be in some…..

b. The Variable that is measured well or not –  overall  all equipment’s are the same….

I think these are 2 different questions

Evidence –  based on what we measure. Expecting a change between life and death in a disease  by a monitoring measure can’t and won’t “show  any difference”

Nurse and CO monitoring – It is clear from the amount of enthusiasm and number of “specialist nurse” that we have for the “Enhanced recovery program” for major surgery which is based on a “Kit” monitored by “nurses” is believed to have made a big impact compared to ” usual practise”

Which to me translates to “Nurses work better with monitoring that is more objective than getting instructions at unpredictable frequency”

In ICU where there are varying levels of expertise/opinions (depending on the time/patient group/trainee/speciality) – For a sick patient where a dilemma is between “fluid” or “Noradrenaline or dobutamine” – It is hard to imagine how we can defend ourselves for the decisions we make without objective measures as a wrong choice will be difference between life and dealth

I absolutely agree that we endup with giving too much fluid. Like many other interventions(including Protected ventilation ,ECMO  control arms etc) in such interventions it is the process rather than the “kit” that makes the difference to how much we give

I think we underuse it and should have clear protocols using non-invasive  cardiac output monitoring  that can be used by Nurses/ANP/ Juniors  when a sick patient turns up at any time  with of course close medical supervision to pick out whichever variables that needs special attention to keep the focus on the patient and not the numbers

Like the Enhanced recovery Program!


Is continuous cardiovascular monitoring worthwhile in those with an unstable cardiovascular system ?

In my view the answer is YES. Used properly it will help guide our trainees and nurses.

Which patients should we use it on ?

I think the issue is that those providing minute by minute care do not have the experience to know when to use the monitors. This means that optimal care can only be provided by monitoring everyone sick enough to need vasoactive agents.


Something like the Vigileo ……. might not be an idea monitor but better than an inexperienced guess !


I am so glad to see this discussed. as I’ve found little use for cardiac output monitors over the years, relying instead on history and clinical examination.

When I was a trainee, one of my bosses was a big fan of ‘BigToeCO’. It relied on feeling the big toe. Clearly, that’s not all it involved. It also relied on feeling the forehead. The algorithm was pretty basic. If the big toe is cold, then it’s nearly always one of 3 things:

  1. Cold toe & dry forehead – hypovolaemia with sepsis
  2. Cold toe, forehead clammy with blood on floor – hypovolaemia secondary to bleeding
  3. Cold toe, forehead clammy, no blood on floor – cardiac failure

It still works pretty well.


I agree about excessive fluid and I think that (alongside actually achieving 6ml/kg) should be our next major drive.

In terms of a package of care/process a la ERAS. All you have to do is mandate a SLR before a fluid challenge. Less than 10mmHg rise = do not give fluid challenge unless you think they’re very hypovolaemic.
Job done, without spending a fortune on expensive machines. I like Hamish’s protocol too though!

Two comments on Big Toe temp. I am sure it wont surprise you to find I am also a fan of this

1] Doesn’t work if there is a Bair Hugger on the big toe !

2] Peripheral skin temperature reading allows this parameter to be recorded on an ICU chart


So a couple of thoughts…

Any evidence?
Non that I am aware of but like A I’m happy to be corrected.
Do they have a role in critical care?
Firstly, like any modality of monitoring or investigation the most important thing is ‘what question are we asking?’ I’m not convinced that immediate routine application of cardiac output monitoring and generation of a string of numbers in all critical care patients will help anyone (apart from the company selling the device). However, in the context of an appropriately formulated clinical question maybe they have a place in my future practice. I agree this role is probably better fulfilled by clinical assessment and echocardiography, which leads me on to my second though…
In the current climate of increasing demand with decreasing resources (especially medical staffing) devices such as cardiac output monitoring in conjunction with robust protocols may offer the best way of ‘doing the most for the most’. I believe the optimum approach is likely to remain clinical assessment by a well trained and experienced professional (either medic or ANP) supplemented by clinical tests such echocardiography. However, in the future we may need to rely on monitoring, protocols and empowering our bedside nurses in the majority of cases so that our limited medical resources can be utilised in the situations when it really maters. For me the question of cardiac output monitoring with associated fluid and vasopressor protocols is more about non-inferiority rather than superiority. Contentious?
Echocardiography has been mentioned a couple of times as an alternative to cardiac output monitors in guiding fluid resuscitation.  A couple of points to be aware of are as follows:

  • Echocardiography cannot diagnose euvolaemia, nor can it differentiate euvolaemia from fluid overload particularly well.
  • TTE derived predictors of fluid responsiveness (IVC distensibility, VTi variability) are no better than the predictors offered by CO monitors, but have several disadvantages in that they are operator-dependent, cannot be used continuously, and require a fair amount of training to derive)
A FICE echocardiogram will usually give you useful information in a shocked patient.  It’s not much help in guiding therapy towards particular endpoints, so for that purpose ( if that is your purpose) it’s less accurate than a cardiac output monitor in measuring/deriving certain parameters.

To keep the flow

On PLR or SLR- It might be cheap but

The method for performing PLR is of the utmost importance
1.PLR should start from the semi-recumbent and not the supine position .Adding trunk lowering to leg raising should mobilize venous blood from the large splanchnic compartment, thus magnifying the increasing effects of leg elevation on cardiac preload and increasing the test’s sensitivity..

2.Technique used to measure cardiac output during PLR may vanish after 1 minute
3.Cardiac output must be measured not only before and during PLR but also after PLR when the patient has been moved back to the semi-recumbent position, in order to check that it returns to its baseline. Indeed, in unstable patients, cardiac output changes during PLR could result from spontaneous variations inherent to the disease and not from cardiac preload changes.
4..Pain, cough, discomfort, and awakening could provoke adrenergic stimulation, resulting in mistaken interpretation of cardiac output changes. Some simple precautions must be taken to avoid these confounding factors.

5.PLR must be performed by adjusting the bed and not by manually raising the patient’s legs. Bronchial secretions must be carefully aspirated before PLR. If awake, the patient should be informed of what the test involves. 3PLR is unreliable in the case of intra-abdominal hypertension

I am not a big fan of doing this in ICU


I think we are talking minutiae and niceties of volume assessment whilst the problem is actually a bit more gross and has already been pointed out- apparently random administration of large volumes of fluid in an uncontrolled and undirected manner leading to significant damage that is readily ignored as it is not immediately and directly measurable.

I have always just given 250-500ml of fluid as a ‘proper’ bolus (i.e. very quickly through a large drip- not on a pump through a central line). If the parameter I am interested in (BP, CO, PPV, SVV etc) doesn’t improve then I don’t chase it. This may differ from the more scientific approach taken by some, but the key point is that I don’t keep giving the fluid and expecting a different result if there was no discernible benefit to the first aliquot (isn’t the converse approach considered as the first sign of psychosis?)
I think NICOM can be used to direct this, and may be more sensitive and specific than my observation of more prosaic parameters, but my question then is how has it become routine practice to empty another 5 litres into he patient anyway? My perception is that there is an unnatural fear of renal failure and a drive to prevent this complication at all costs- even if the patient’s renal function is normal and the pursuit of vascular filling is clearly impairing organs that are known to be damaged (and not amenable to simple mechanical replacement).
There is no little understanding of the damage caused by overfilling, but a fear that underselling will be heavily criticised and renal replacement therapy amounts to professional failure. NICOM might be able to prevent some of this damage as it provides an objective value that can be used to ‘defend’ a decision not to flood the patient.


I –

Even in my short time as a trainee I have come across 4 or 5 different CO monitors used across different units and have yet been convinced by any of them (although if I ever need inspiration as to which lottery numbers to pick there is normally a plethora displayed on the monitor to choose from!).

The main advantage I can see as already mentioned is it highlights to us all that fluid balance is an important issue. A sign above the bed would I imagine be much cheaper in comparison.

My biggest dislike with them however is that they seem to make it even less likely for people to make a proper hands-on clinical examination of a patient’s fluid status instead relying heavily on a set of numbers written on the chart. This already happens on an already too frequent basis when the “overall fluid balance from admission” value is used to alter fluid status management. I fear if CO monitoring became commonplace we would create a generation of trainees who are even worse at assessing clinical fluid status than we already are. I am yet to see a case where the monitor has told me to do something that was not already clear from examining the patient (+/- a leg raise).

The other issue I see is that the majority of those 5–6L the patient has received has often occurred outside the ICU and CO monitors on the unit will not prevent this.


Regards the evidence.  Having being involved in the Optimise Trial, (which looked at intra and post op major intra-abdominal surgical patients, PI Andy Breen), first hand, anecdotally, I can see  that NICOM are particularly useful to guide fluid administration from a nurse led perspective.  The study did not show significance overall but some benefits were observed.  I appreciate that ICU septic/cardiac failure patients are a completely different group, but the ability to objectively monitor trends and acute changes is of definite benefit to the bedside nurse (after all that is what they do continuously) as well as trainees, ANP’s etc, in conjunction with clinical assessment of course.

I agree barriers are high cost and inexperience with the equipment, but seeing as the directorate has invested a large amount of funds in obtaining a number of these machines and their disposables………  why not?

From a nursing perspective.  Having worked at both sites, I have observed  how staff have become accustomed to their use at SJUH and less so at the LGI, probably due to patient cohort.  I believe that nursing staff do not feel them to be a huge amount of additional work once set up.  If we could empower the nursing staff to recognise and report/act on changes maybe fluid balance management could be improved.


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