Monday, July 23, 2012

Mysterious Hypotension

I found this very useful.  I will explain in the following post.  Please read Dr. Agar and his comments here.
  1. Dr. Agar, one of our IHD members is having a problem with hypotension that has become quite debilitating for her. She has given me permission to share with you the link to her forum post about this problem:

    I have met Desert Dancer, and she is the picture of health. She is our poster child for good dialysis. She does NHHD. She had a parathyroidectomy at around the new year. She has been on dialysis for only two years. You can read her history in her signature.

    It would not be ethical to ask you to diagnose her from half a world away, and her nephrologist is doing her best, I'm sure, to figure out what's going on. But we are all rather stumped, and I wondered if you've ever had a patient like our Desert Dancer who has had the same difficulty with hypotension. Any ideas you might have would be greatly appreciated. Thank you.

Re: Mysterious hypotension
  1. Dear Desert Dancer (via Moose Mum) … sorry, but I do not know what other name to call you by …

    You sound as if you have had a terrible time since your parathyroidectomy ~4months ago and, reading through your clinical sequence at the IHD site, it does seem pertinent that the problems surfaced following, and have persisted since this procedure.

    The gist of the problem seems to be a BP ranging 70s/40s coupled with constant dizziness.

    I am pleased you have had an echocardiogram and that this has been stated as normal … this is a very helpful thing to know … and that all the usual things have been tried. I, too, would have bet on too low a dry weight as the most likely problem … though one might have expected, if anything, a little peri-operative 'weight loss' rather than peri-operative ‘weight gain’ and thus, if anything, a little more volume to remove in the post operative days, not less. But, you have tried raising your dry weight – quite significantly – to no avail.

    Anti-hypertensive drugs (eg: atenolol) were (wisely) ceased – also to no avail. Midrodrine, an anti-hypotensive drug that causes vasoconstriction and that helps to raise blood pressure was tried (also without apparent effect) … though I am glad the echocardiogram had been done to ensure good LV function first, as it (midrodrine) is a drug that demands much respect and needs to be used carefully in well selected hypotensive dialysis patients. It is a drug which I have to say I try not to use at all.

    I am also glad you are having thyroid function tests done – these are important to know and be sure that they remain normal – though it would be unusual to find acute thyroid insufficiency after parathyroid surgery.

    The same can be said for checking adrenal function – though, again, why sudden low adrenal gland function should suddenly occur post-parathyroidectomy is a little obscure.

    I note that sodium modeling has been considered (fairly) but rejected (also fairly), for the reasons you state.

    I can also understand your (sensible) anxiety about this affecting your fistula, vision or other complications from it.

    Indeed, it sounds like Desert Dancer has a caring nephrologist who has done all the things that would be done by us all in these circumstances.

    While the temporal association of the onset of your 'troubles' with your parathyroid surgery is hard to deny, I am sure your nephrologist has considered both the possibilities of (1) a relationship and (2) co-inicentality … though I, too, would still be favouring an inter-relationship with the surgery, given your prior excellent health, BP’s and course.

    Turning back to the parathyroidectomy … as this seems to me where the answer may best lie … there are a few 'observations to make. However, it must please be remembered these following comments are made without any knowledge of the patient and thus must be interpreted only as 'thoughts' - and not as fact or informed opinion.

    That said, there have now been several reports of a 'partner syndrome' to the well known ‘hungry bone syndrome' post-parathyroidectomy.

    I will copy below the text of an abstract which was presented under the internet address of the International Society for Hypertension ... though tbis site does not give the authors names nor their institution … so I must note that (1) an unauthored/undirected abstract should be interpreted with care, however, (2) I believe the context of it is good (ie: the ISH) and (3) I must apologise to the authors for not quoting and acknowledging their names and/or their institution(s), but I could not locate these.


    Objective: Secondary hyperparathyroidism and hypercalcemia have been associated with mild hypertension , while parathyroidectomy usually causes a few mmHg drop in blood pressure (BP). We noticed an unusual (and yet unpublished) occurrence of acute severe hypotension immediately after total or subtotal parathyroidectomy, in severely hyperparathyroid and hypertensive patients on hemodialysis. The hypotension becomes longlasting, sometimes disabling. Our aim was to collect clinical data on these cases in order to understand their pathophysiology.

    Design and Methods: We reviewed dialysis recordings of 5 dialysis centers, looking for symptomatic hypotensive patients who were hypertensive before parathyroidectomy. Three patients were detected: patients were interviewed, their medical charts were analyzed, and sitting and standing blood pressure were measured. For two patients we added measurements of central blood pressure and pulse wave velocity (PWV) using SphygmoCor device.

    Results: Patient characteristics and BP measurement done by us are shown in Table 1. All three patients were on Hemodialysis from young age due to congenital or primary glomerular disorders. All had many years of severe tertiary hyperparathyroidism with resultant Ca++ above 9mg/dl despite treatment. Two patients had BP values around 170-200mmHg systolic despite multiple medications. All three showed abrupt fall in blood pressure, that persisted for months, and in one case for 10 years. Currently,two patients have severe symptomatic hypotension, and one patient has borderline hypotension,and doesn't need his blood pressure medications. On average Ca++ dropped about 3mg/dl after surgery. Patients have evidence of preserved cardiac output, decreased systemic vascular resistance, and, despite being on hemodialysis many years,low PWV, reflecting good arterial elasticity.

    Conclusion: We describe a novel clinical presentation of "hungry bone and dilated vessels" syndrome.We found no evidence of orthostatism or autonomic failure,nor a surgical disruption of the carotid sinus.We documented increased arterial elasticity and decreased resistance. A possible change in intracellular calcium, calcium sensing receptor sensitivity or PTH receptor can explain the hypotension. Thus,calcium supplementation or infusion might be of clinical benefit.

    The abstract is, however, interesting. It cites a review of 5 centres and the identification of a ‘syndrome’ … a syndrome is a word for a grouping of similar, likely related findings … where in 3 patients, severe, long-lasting hypotension post-parathyroidectomy was (1) identified and (2) characterized. These authors (unknown to me) described the findings nicely … and it may be worth your showing this particular abstract to your nephrologist.

    The authors of this report conclude that the profound vascular relaxation and blood vessel dilatation may be in response to changes in intracellular calcium or to changes (a resetting) of calcium sensor sensitivity and that calcium supplementation or calcium infusion might be of benefit … though the abstract does not describe this action as having been either taken nor whether, if it was, if it was a successful measure.

    I have not come across this response myself. However, your description is consistent with the syndrome described by the authors, and the theoretical cause and the solution provided by the authors of the abstract seem plausible.

    ‘Hungry bone syndrome’ is well known. Perhaps these authors are describing a parallel ‘hungry vessel syndrome’ with a profound intra-cellular calcium deficit in the endothelium as the cause.

    Interesting ... and I am grateful to Desert Dancer and MooseMum for raising the topic ... for, even if no certain answer can be given, it is great to have to think about it - and to then try to give a sensible response.

    Up-To-Date gives a reference (from a Japanese group: Shinoda et al: Nephron 1992. 60 (4): 482) … a similar report … and again a calcium-based cause was postulated.

    Other references dot the literature – mainly as case reports or in experimental animal work – that attest to the rare but seemingly substantiated occurrence of a profound and lasting ‘hungry vessel syndrome' (my words) … just like as we see with the much more common and well known ‘hungry bone syndrome’.

    Several questions aren’t answered in any of Desert Dancers ‘posts’ … and these all pertain to her calcium status. Did she indeed have hungry bones? What was the level of calcitriol and calcium replacement post operatively? … a process that we routinely protocol-ise and ensure is renal-physician/endocrinologist supervised and not left to the surgical service alone, aggressively ensuring that all post-parathyroidectomy patients receive Ca ++ and Vit D … noting that, sometimes, extraordinary demands and made for (and supplementation needed) to ensure calcium and active vitamin D replacement is adequate – sometimes for months.

    Finally, we (but, more importantly, Chris Chan and his Canadian team who first described it … see Nephrol Dial Transplant (2004) 19: 714–719) have noted a significant increase in the occurrence of delayed graft function and intra- and post-operative hypotension in the days immediately post transplantation in patients who have been on frequent nocturnal HD (extended hour and frequency) dialysis.

    This is a most interesting finding – and is one that seems quite consistent across the experience of the (now) many units who encourage this dialytic modality.

    The question is … why? The postulates (unproven) as to the cause take two main directions: (1) that only these patients among all dialysis patients are in true sodium balance … all others being in a state of chronic sodium overload … and (2) that ‘something’ that affects vascular tone is ‘different’ – with the postulates centering around 3 potential substances: endothelin, nitric oxide … and calcium!

    Not enough is known to take this further, but it is one little added ‘snippet’ that attests to the vital role that endothelial intra-cellular calcium plays in vascular tone and where disturbances of calcium balance can have profound effects on blood pressure regulation – and , especially in these instances, hypotension.

    One aspect I have not dealt with is a 'solution'!

    I note with interest that she is on NHHD.

    We do not know her dialysis fluid (aka - incorrectly - the dialysate) calcium. This is important.

    We commonly use high calcium 'dialysate' ... with a 'bath' Ca++ concentration of 1.5 or 1.6 mmol.L = I think equivalent to a 3.0 - 3.2 mg/dl. Indeed I would go so far to say that it is mandatory to do so and that 'normal' dialysis fluid calciums of 1.3 mmol/l (? 2.6 mg/dl) are way too low for NHHD and will produce a significantly negative Ca++ balance and a toal calcium deficit. This may not always be seen at the macro-level of the serum but may be only at a cellular calcium level.

    I apologise for my mmol/l v mg/dl problems but the US is the only country in the world that does not use international unit system based on mmol/l and I have trouble with conversions to your older system..

    I presume she is on at least a 1.5 mmol/l (3.0 mg/dl) Ca++ fluid.

    Even more, I would expect her to need even more - probably a 1.75 mmol/l (equivalent, I think, to 3.5 mg/dl) dialysis fluid Ca++ concentration. We have not uncommonly used a 1.75 mmol/l = 3.5 mg/dl concentration as our standard 'bath' for NHHD ... aiming for a pre-dialysis Ca++ level of around 2.45 mmol/l (? is that 4.9 mg/dl) and a post-dialysis Ca++ level of ~2.65 mmol/l (? 5.3 mg/dl) ... ie: mild hypercalcaemia.

    The calcium bath of NHHD must be higher than it is for standard 'conventional' dialysis! No if's, no but's ... must be.

    If she is on a normal 1.3 mmol/l (2.6 gm/dl) ... may I hope not ... or even a 1.5 mmol/l bath Ca++, then her 'hungry bones/hungry vessels' will never have had a ghosts chance of recovery and she will be in continuous negative Ca++ balance. I

    f this is what is happening ... though I suspect she already will be on a high Ca++ dialysate ... then she is likely profoundly hypocalcaemic - if not clinically, at a cellular level - and I would not then be surprised at all by her persisting hypotension!

    We need to know this information to know whether all that 'matters' in this particular case ... or whether it is just comment.

    One final feature of Desert Dancer's symptoms that suggests calcium may be the basic issue here is her observation that

    "... things that used to take me an hour or two now take all day long because I have to rest every 15-20 minutes. I can't talk or chew for more than a minute or so before my throat seizes up ..."

    Calcium plays an important role in muscle function ... and low intracellular calcium is associated with muscle fatigue and with laryngeal spasm or weakness. It also can cause cramp-like spasms in the fingers and toes with exertion - carpo-pedal spasm - and sometimes numbness and tingling sensations in the peripheries and around the lips - though none of these are essential for the diagnosis. It might be interesting to know if she has been checked for a positive Trousseau's sign ... a curling-like spasm in the fingers and at the wrist +/- numbness and tingling in the fingers if a BP cuff is inflated to greater than systolic pressure for a few minutes.

    Do I know the answer for Desert Dancer? … no, I do not.

    Can I make an educated guess that it may lie within this issue … well (a qualified) yes, I think I can ... or have.

    This should be discussed with your managing team. As observed in the referral of this question, no internet answer – patient unseen – should be taken as ‘gospel’ . Only broad concepts (even if then) can be discussed. But, I hope this answer may be of some value to Desert Dancer.
    Last edited by John Agar; April 23, 2012 at 02:43 AM.