Fluid resus in sepsis

This month’s question concerns fluid administration in patients with septic shock. Are the surviving sepsis guidelines suggestion of an initial “rapid bolus of 30ml/kg crystalloid” in those patients with hypotension and lactate>4mmol/L  more harmful than useful?

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A  – I always think the proposal to limit fluid resus is pragmatically difficult, but it may well be a valid improvement in care.

We all know that a fair proportion of septic patients come into A&E hypotensive, get 2 or 3 l fluid and never require critical care. If we suddenly put all these people on pressors instead we’d have to significantly increase our level 2 capacity. We also then expose these people to the potential complications of critical care. Arterial lines and CVC’s are not harm free interventions, nor is peripheral phenylephrine for that matter.

I’ve definitely come round to thinking >30ml/kg is likely to be harmful in many/most though.

B –  A couple of points.

A ‘rapid’ bolus could well be harmful, as quickly filling the central compartment leads to an increase in Pc and Jv, causing more tissue oedema, and increasing the need for further fluid.  Maybe the medics have got it right all along with their 8 hourly bags of fluid?

In terms of optimal treatment, the NHS is not adequately staffed to provide ED/ crit care discussion and review at a senior level for all the hypotensive ‘septic’ patients who come through the door.  We certainly do not have the staff and bed resource to provide timely review and vasopressor therapy to all these patients, as may happen in a trial setting.  I think a large cohort of patients avoid crit care admission with probably a bit too much fluid and a slightly inadequate blood pressure.   What that does to their length of stay, nephron numbers and mortality is uncertain.

Does small volume tissue oedema cause harm?  I think it does in post operative patients where the majority of oedema is focused around the injured area, for example the anastomosis, and increased oedema increases oxygen diffusion distance.  I wonder who the surgeons blame when an anastomosis breaks down- the equipment, the epidural, the patient, (themselves??), or do they look at the fluid prescription?  However, in patients with sepsis, I think the harm is smaller, and to some extent acceptable.

 

C – I think sensible fluid administration in the initial presentation of sepsis is probably ok. However there are lots of reasons why ongoing high volume IV fluids in this patient group are a bad thing. What I find a bit of an issue in the initial fluid resuscitation is that fluids are generally prescribed in litres with probably little regard for the patient’s weight. There is usually also little consideration of the other sources of fluid that are administered to the patient e.g. antibiotics. What is probably being given to the majority of patients is actually well over 30ml/kg. This may be something worthwhile auditing in order to direct people towards more tailored fluid therapy.

I agree that the current critical care capacity in the UK won’t be able to support an increase in numbers of patients having early vasopressor support in sepsis, however this may be something that could be solved by the current discussion of the level 1.5 patient. There are programs at the moment trialling nurse-led ward-based care in postoperative patients (e.g. York) so there is no reason why it couldn’t be extrapolated to this patient group as well.

 

D – The prevalence of responsiveness to initial fluid challenge among hypotensive sepsis patients is unclear. To avoid fluid overload, and unnecessary treatment, it is important to differentiate these phenotypes

Most evidence against the efficacy of fluids for sepsis patients addresses harms from long-term positive fluid balance , an outcome probably distinct from rapid initial fluid resuscitation. Evidence suggests the latter is protective.

There is a lack of any randomized investigations for either intervention in defined sepsis populations. In fact patients in the three recent goal-directed therapy trials received comparable initial fluid volumes in similar times.What is still needed is to refine and validate the baseline predictors of the initially fluid refractory phenotype until then we have to guess for each patient

Not helped by the fact that in the current framework defining sepsis as “dysregulated host response to infection,”  any broad modulation of this system could logically predispose or exacerbate a state of dysregulation. Endothelial activation and damage are pivotally implicated in sepsis, which could explain connection between coagulopathy and initial blood pressure responsiveness.

The size of the bolus and the duration for resuscitation is to tailor made for each patient as it is both beneficial and potentially harmful

 

E – Do any of you FICE competent folks ever scan the IVC in A&E etc…? Is it a tool used routinely as part of your assessment pre and post fluid bolus if you have the skills?

 

F – I write this in simplistic words as it makes sense in my head…

I feel that I would open myself up to criticism if sepsis was suspected and I did not resuscitate with fluid.

For me, I feel that fluid is harmful when given in uncontrolled volumes and a response is not monitored at the end of the bed.

In many cases of sepsis, we are informed that the patient has had 5 litres of fluid and we find them in a hypotensive state and would probably benefit from peripheral phenylephrine. These high volumes of fluid with no/minimal response are those which I feel cause harm.

Where I  am unsure and would call upon expert advice would be for those patients with cardiac failure and chronic kidney disease in cases where they are anuric (not through AKI). There are also many other cases to seek advice on but those are the obvious that come to mind.

G –  I do feel that that the rapid 30ml/kg advice is potentially harmful (looking at up to 3L in a significant proportion of our population given the 70kg man and 60kg woman were left back in 1981) if only because it perpetuates the notion that sepsis is primarily a hypovolaemic rather than a vasoplegic state. Obviously this is a spectrum when you consider those who have significantly reduced PO intake and losses (pyrexia, D&V etc.) associated with an infection.​Kumar makes a valid point about separating this from persistent and aggressive fluid resuscitation where there does seem to be accumulating evidence that it is associated with worse outcomes (obviously the more extreme examples of this are the FEAST trial NEJM 2011 and more recently  SSSP2 in JAMA end of last year).

I do worry that we focus on arterial pressure and extrapolate that to stroke volume and cardiac output when fluid resuscitating (a jump in itself), completely ignoring the venous portion of the system and the inevitable venous hypertension and reduction in organ perfusion (particularly of capsular organs) even though the systolic BP reads higher. However I’m not entirely sure how to combat this except by advising aliquots of fluid depending on size and co-morbidities and frequent assessment with a view to stopping the administration of fluid boluses when this response is blunted or absent, although this later part is a contentious issue in itself…….

Regarding the IVC collapsability/distensibility I do remain to be convinced of it’s use outside of extremes in much the same way we use CVP to be honest!

 

A – Agree with G on IVC assessment.

All the fluid debates end the same way unfortunately. “How much fluid should we give a septic patient?” “Well it depends” “On what?” “Lots of things!”. The heterogeneity of preceding factors, comorbidity, pathology and genetics make it very tricky. Overall 30ml/kg isn’t an awful marker to make you reconsider what you are doing and if it’s working.

In a vaguely similar (massive SIRS response) sense look at the post liver tx patients. Some seem to need absolutely drowning in fluid, some don’t. I remain unable to explain this.

H – I agree with pretty much all that has been said- the situation is far from clear and I doubt that there is a generalizable approach to sepsis resuscitation other than to state that it may include a significant volume of fluid and that it needs to be individualised with repeated reassessment. Experience suggests that it is this reassessment that is more routinely lacking at ward level, and my concern with the guidance offering a potential requirement in mls per kg is that it becomes a headline in the treatment pathway and may encourage a prescribe and leave approach.

 

I don’t think anybody could be criticised for resuscitating with any particular volume as long as their approach is rational and based on repeated assessment of response.

I do think the bigger problem for us on the unit is the perception that repeated boluses of fluid are entirely benign and the repeated dosing whenever the urine output drops below some arbitrary threshold is without harm.

I –

I had optimism about the use of sequential measurements of the velocity time integral (VTI) across the left ventricle outflow tract (LVOT) on trans thoracic echo. When I tried to do this, it became apparent in my eyes, this would not be a realistic technique for regular practice.

Then I got interested by Marik paper (see below) My interest shifted to the carotids. Dynamic assessment of the carotid flow/ velocity/ flow time to a straight leg rise is interesting and makes sense to me. (I accept the evidence base is sparse)

I had a go at measuring carotid blood flow but I found that unlike the LVOT area which is fixed, the carotids require 2 diameter measurements. This adds hassle, and potential error in the diameter measurement and can give misleading results. There can also be faff with getting the doppler insonation angle correct.

Now I have become more interested in carotid corrected flow time for fluid responsiveness, mainly because it is really quick and easy. (I accept the evidence base is sparse) It is quite interesting to put the USS doppler over the carotids, just before your central line, then I ask the nurse to do a straight leg raise, and look at the dynamic change in carotid flow time.

G –

I do think this is an interesting method at helping guide fluid but as you say unproven. I know that other POCUS (point of care ultrasound) advocates are looking at this from a different angle, using US to determine when a patient has had too much fluid searching for sonographic evidence of increased extravascular lung water and changes in portal vein flow. I wonder if a combination of these will be protocolised and trialled in the near future.

Interestingly I met Prof Andrew Rhodes (talking through Surviving Sepsis Guidelines 2016/17) at critical care reviews and asked him why despite the general reduction in how aggressively SSG suggest we resuscitate people  (from Rivers supraphysiology circa 2004) the initial fluid bolus has increased from 20ml/kg to 30ml/kg and he seemed to suggest that this was in view of the initial resuscitation volume that patients tended to get in the relatively recent RCTs e.g ARISE, PROMISE (prior to randomisation) rather than any specific evidence to show a larger volume was better. Make of that what you will…………………………

J –

The current trials remain confusing as it is such a heterogeneous patient group. I remain convinced however that both under resuscitation (too little too slow) and over resuscitation are harmful (too much OR too fast through different mechanisms including endothelial sheer and accelerated value also damage).  Do you central problem as we have not yet defined of the goal of resuscitations is to target the central circulation and major organs, or the wider microvasculature, with the risk of increased tissue oedema. The aims of resuscitations of the two strike me as fundamentally incompatible.

K –

I asked Prof Dellinger (previous 1st author SSC guidelines) a similar question a while ago and his answer was more or less in the same line: he pretty much said that they had increased the suggested initial bolus to 30 ml/kg in the hope they would achieve the desired 20 ml/kg in clinical practice.

He also said something that I think is important: These guidelines were not created for experts. So if, as a clinician, you are worried about how much fluid you are giving to your patient and are using echocardiography, US or other dynamic assessments of fluid responsiveness to try and adjust fluid resuscitation to your patient needs… well, you are probably doing fine without having to focus particularly on that number.

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