Low Blood Pressure During Dialysis

Ask Our Experts Dr. John Agar, Nephrologist
1

My mother is on hemodialysis. It does not happen often, but once in a while, dialysis has to be discontinued halfway into the session due to low pressure (e.g. 94/50 a few days ago). She did not experience any nausea or light headedness. She normally has blood pressure that is on the high side (140-160). I`ve read about some of the reasons why hypotension during dialysis may happen. As far as treatment, the dialysis clinic told me they used saline solution and oxygen but the pressure did not rise.

  1. If dialysis is stopped mid-way during the session, does the process of cleaning the blood continue and is just the process of removing excess fluid stopped? Or are these two processes interlinked/one and the same?

  2. Besides saline and oxygen, what other things can be done to raise blood pressure during dialysis?

  3. Can different kinds of saline have greater/lesser effect? I am reading that 7.5% hypertonic saline (30ml) is particularly effective

  4. Is Cool Dialysate effective for hypotension and does it have any risks associated with it?

  5. Is using bicarbonate buffered dialysate instead of acetate buffered dialysis fluid effective and what is the difference between these and Cool Dialysate?

  6. Does Midrodrine have an immediate effect or is it something that is used on an on-going basis between dialysis sessions?

Thank you.

2

Dear …Muraiken

There are several potential answers to your questions.

First, I would be wondering about whether her dry weight is correct. If her dry weight has been set too low and, thus, more fluid is being removed than her circulation is set to permit, then an exaggerated fall in blood pressure or a ‘crash’ is more likely. Certainly, in the general dialysis population, the removal of too much fluid – or, and I keep coming back to this point, its removal too quickly – is the commonest reason why blood pressure might fall or crash during dialysis.

You need to remember that patients change their base weight, just as you and I do. Just as we put on a kilo or two, and then take it off again, so, too, do dialysis patients. We, as the treating team, need to “roll” with these changes and make adjustments accordingly, otherwise we will be caught out by taking off too much fluid – or taking off too little. No patient sustains the same dry weight, week in, week out. Here, we are constantly looking at BP changes and other signs that might indicate a change in dry weight. This is probably the first thing I would be thinking about.

I am assuming that the BP you have given (140-160), is her pre-dialysis blood pressure. Though a little on the high side, this is not a blood pressure that would be troubling me too much as an entry (pre-dialysis) blood pressure – I would be more troubled by a blood pressure fall from this level to 94/50 during the dialysis treatment.

I wonder if she is on any blood pressure pills? Many of these have relatively long durations of action, and may interfere with the capacity of the vasculature to respond to fluid removal, accentuating any impact that this fluid removal may have on blood pressure. We certainly would tried to avoid any blood pressure medication in the hours leading up to dialysis.

I have referred before to the heart and the impact of dialysis fluid removal on a heart that is maybe not as strong as it might be. Sick hearts do not well-tolerate big fluid shifts on dialysis. You might want to read back over previous answers to others if you are unclear about this.

And, of course … and I feel like an old and worn-out record as I repeat this again and again … the best way of avoiding blood pressure pertubations during dialysis is to lengthen the treatment. Rapid fluid removal is simply not well tolerated by many – particularly older patients and particulary patients with ‘dicky’ hearts (or is that an Oz-ism?) – and it is the speed of fluid removal that causes the majority of trouble for most dialysis patients. I cannot emphasise this fact enough. I know I go on and on about this, but it is a simple fact yet so many seem to ignore its’ importance. I also know that US dialysis patients tend to be trated with short, hard, aggressive dialysis regimens when compared to their European, Japanes and Australian and New Zealand ‘cousins’ – a factor in the differences we see between US and other national dialysis morbidities.

As for saline administration, I simply abhor ever having to do this to a dialysis patient – yet, how often does it seem that it happens? It is so counter-productive and counter-intuitive to give salt and water to a patient where part of the whole raison d’etre for the dialysis is the removal of them? Think of it! Here we are, trying to remove fluid (and in my view, most try to do this too fast – hence my insistence on lengthening the time of dialysis), and, because fluid is being removed too fast, the BP crashes. What do we do? We give saline! But, isn’t that exactly what we’ve been trying to remove? It is nonsensical! Absolutely nonsensical! I know that if the blood pressure falls, saline administration may be the only choice we have in terms of resuscitation – it is simply that that resuscitation with saline should not have been necessary – is never necessary – with a longer, slower, gentler dialysis.

We use cool dialysate here – our standard is 35.5C. This is certainly has been shown to lessen the incidence of hypotension during dialysis but again, the main game is slower dialysis. All other ‘ploys’ are tricks to avoid ‘ the elephant in the room’, dialysis time!

I am surprised that you even raised the issue of bicarbonate versus acetate buffered dialysate. Certainly, we have not used acetate as a buffer here for more than 20 years. In the old days, when acetate was used as the buffer, it certainly was a contributor to circulatory instability during dialysis. Most dialysis systems and services would now use bicarbonate as a matter of course.

Midrodine (and other agents to support the blood pressure) are, in my view, agents of last resort, and not ones that I would think applicable to all but a tiny handful of patients – usually those with very advanced heart trouble.

In order, I would be ensuring she is not on pre-dialysis blood pressure medication, I would be trying to ensure that I had the correct dry weight estimate, I would be using cool, but not cold, dialysate and I would certainly be using bicarbonate buffered fluid. I would be avoiding drug therapy. Above all, however, I would be looking at lengthening the dialysis schedule.

I have written much on the issue of dialysis duration in these pages and I hope you will forgive me if I do not repeat these reasons here yet again. You may wish to turn back to previous questions and their answers – like the question posed by Jane late last year like “what factors determine optimal dialysis” – to reread some of this information.

This information is also available at my website http://www.nocturnaldialysis.org.

You will also find it discussed at the original Webinars I did for Dori at HDC on solute and fluid removal (see Part II).

Now, of course and finally - none of this may apply to your mother. I do not know her, know her case, know her dialysis details or know the circumstances of her care and management. Only your team can advise the applicability of any of the issues I have reaised in answer to your questions. I would suggest, if you are worried, that you let them know of your concerns and follow up with the team that cares for her. The comments I have made are meant as general comments and not as a specific response to your mothers’ case.

I hope this has been of some help.

John Agar

3

Dr.

Thanks for the detailed reply. One follow-up question - I understand that because the refill rate lags behind the ultrafiltration rate, blood pressure drops. I understand that dialysis machines are set to remove a certain amount of fluid per hour. Can most dialysis machines show you in real time how well your tissue is refilling and keeping up with the fluid changes in your bloodstream(i.e. how well the plasma refilling rate is keeping up with the ultrafiltration rate). If so, does the machine have the ability to slow down the fluid removal rate to stabilize things or at least give off a warning signal to alert the dialysis team? Can the dialysis team step in and lower the fluid removal rate to stabilize blood pressure? I dont quite understand why dialysis had to be stopped mid-way - couldnt they have intervened earlier when they saw signs of an imbalance between the PRR/UFR rates? Thank you.

4

No … machines can’t measure the plasma refill rate (except rather indirectly if a BVM is available - and, even then, by rather blunt and rather inaccurate estimation) … and no, machines dont ‘slow’ the fluid removal rate by themselves - though the nurse attendant (or home patient) can do so by altering/reducing the UF rate. So, yes, the dialysis team (or patient) can do that. I can’t answer your question why the dialysis was discontinued part way through - I suspect specific indications were occurring during that particular dialysis that may have led to this response but what these might have been and of what severity, I cannot answer.

John Agar

5

My question is that my father in law has Cancer and it’s on the kidney/liver/and spleen and on the vein from the Kidney.
He also is taking dialysis for Kidneys and has low blood pressure.
The Hospital had him on saline drip into a IV.
My question is that they wanted to take him off the IV drip and said he was going to die in 20 minutes after removal.
They also stopped the Kidney dialysis and saying that his blood pressure was too low to take it.
Are they trying to kill my father.

6

Dear emjean

My sincere apologies for missing this post till now. I hope it is not too late to be of some comfort (or explanation) to you.

No … I don’t think that’s what they are trying to do at all. I think that it may be that, recognising that your dad is nearing the end of his life, they are just trying to be compassionate in their care of him, allowing him to spend the last little time he may have left in dignity and with his family.

Perhaps the failing here - if there is one, and I do not know all the circumstances - is that no-one has fully explained the situation to you and worked through it with you and the family.

It is not uncommon, when the body is failing, for the blood pressure to fall and, in a dialysis patient, this can mean that the patient - here, sadly, your dad - simply cannot be dialysed. The blood pressure can fall to a point where, simply, dialysis is technically impossible. In addition, if your dad is near his end - as we all must be, sooner or later - it can be the compassionate thing, the kind thing, the right thing - to permit and provide a dignified passing without ‘urging’ to the very end. This is called, by some, a ‘good death’. No-one wants their dad, their mum, their loved one, to die. But, when that death seems inevitable and there is nothing left that can realistically be done, it behoves us all - wherever possible - to allow that passing to be gentle and to be in the presence of family and friends and not surrounded by now futile technology and machinery to the bitter end.

Perhaps the failing here, if indeed there has been one, is that no-one has taken you aside and talked about this aspect of his ‘care’ with you. Good ‘care’ not only means doing what can be done but, when all has been done that can be done, good ‘care’ extends to the humane management of the dying process.

Some doctors find the dying part of living very hard to handle. I don’t know why that is so, but we are much better at intervention - and the explanations around intervention - than we are at letting go. Yet, knowing how and when to let go, and then communicate that with empathy to a patient and his/her family, is just as important as knowing how to apply all the whiz-bangery of modern medicine.

A ‘good death’ is a good way, is the right way, to end a good life. I suspect it is what you would want for yourself. It is certainly what I will want for myself, when my time comes. I suspect your dad might, if he could, say the same.