Concept Map: Low Anion Gap

Here is a summary of various causes and mechanisms of a Low Anion Gap

Clinical Case 91: Answer and Discussion

A twitter poll question I had asked


https://twitter.com/kdjhaveri/status/1033699053043949568

Which one of these interferes with plasma and urine catecholamines assay?

— Kenar Jhaveri (@kdjhaveri) August 26, 2018

The answer is all of the above. There are several agents that interfere the workup for pheochromocytoma and can interfere with the catecholamine and dopamine pathway. The comprehensive list is listed below.

Tricyclic antidepressants, phenoxybenzamine, labetelol can affect the measurement of both catecholamines and metanpehrines

Monoamine oxidase inhibitors and buspirone affects mainly the metanephrine measurements

Caffeine, L-Dopa, Carbidopa mainly affect the catecholamine assays

Concept Map: OSA and HTN

 

Reference: http://cjasn.asnjournals.org/content/6/5/954.full

 http://cjasn.asnjournals.org/content/6/5/986.abstract

Topic Discussion: Phosphorus content of prescription Medications

There is a source of dietary phosphorus that has been noted but is largely unrecognized and unquantified—the phosphorus content of prescription medications. That drugs may contain phosphorus is clear, as it is indicated on the list of inert ingredients reported on their package label. Sherman et al few years back did an amazing study that showcased that medication preservatives might have phosphorus content that we don’t recognize. This might be also causing some phosphorus rises in our patients and need for increased binders.

Medication and dose	Manufacturer	Phosphorus content	Amt of Phos binders required additional
Lisinopril 10mg	Qualitest	40.1mg	2
Lisinopril 10mg	Blue Point labs	32.6mg	1.5
Amlodipine 10mg	Greenstone	27.8mg	1
Amlodipine 10mg	Lupin	8.6mg	-
Paroxetine	Glaxosmith Kline	111.5mg	5
Paroxetine	Cadila	22.7mg	1
Renavite	Cypress	37.7mg	1
Renocaps	Nnodum	1.7mg	-

How do we help our patients with this information? Better would be some way of making prescribers aware that their prescribed medications may be high in phosphorus—they are not ‘dialysis safe’. 

Perhaps creating a database of all drugs and their phosphorus content might be useful.  Or is this not consequential to our patients as diet is the biggest factors… the above is just the sample of drugs the author had inquired.. imagine the rest of the medications and other chemotherapy and other anitbiotics we give our patients.

Topic Discussion: ECMO and the Kidney

Extracorporeal membrane oxygenation (ECMO) is an effective therapy for patients with reversible cardiac and/or respiratory failure. AKI  often occurs in patients supported with ECMO; it frequently evolves into chronic kidney damage or end-stage renal disease and is associated with a reported 4-fold increase in mortality rate. What are the mechanisms of injury of AKI with ECMO?

This table below summarizes what might be the potential causes.

Here is a nice reference

Patient-related variables
Pretreatment factors	Hypoperfusion, loss of autoregulation Hypoxia
	Nephrotoxic drugs Systemic inflammation
ECMO-related variables
Hemodynamic factors	Blood flow alterations
Hormonal factors	Renin-angiotensin-aldosterone dysregulation ANP downregulation
ECMO-related	Blood shear stress
Systemic inflammation	Exposure to a non-self membrane Blood/air interface
Organ crosstalk	Cardio-renal syndrome
Circuit-related factors	Hypermyoglobinemia
	Embolism
	Hemolysis

Hemolysis is an interesting cause. This is an image of a patient getting CRRT on ECMO.  CRRT was on a zero K bath and high clearance rates. Within hours of starting CRRT, effluent bags of the CRRT turn red. Despite being on max CRRT,  patient’s potassium rose to 9mmol/L. This is hemolysis and can be reported in 18% of cases with ECMO.  Rhabdomyolysis can also be noted in some cases. Checking a free Hgb and effluent myoglobin can aid diagnosis for both entities. In addition, classic markers for hemolysis such as LDH, haptoglobin, anemia and so forth should be checked regularly. 

 https://www.ncbi.nlm.nih.gov/pubmed/26606144

 https://www.ncbi.nlm.nih.gov/pubmed/28470926

Topic Discussion: Non-nephrogenic calciphylaxis

Calciphylaxis in Patients With Normal Renal Function is usually unusual as most of the cases we encounter as nephrologists are in ESRD and or CKD patients

A recent review and literature update by the MGH researchers defined concomitant risk factors, treatment, and outcomes for patients with nonnephrogenic calciphylaxis.

116 patients today were reviewed.  Vitamin K antagonism and obesity were the most common concomitant factors. In the literature review, lower age and higher body mass index  were associated with the central location of lesions, whereas vitamin K antagonism was associated with the peripheral locations.  None of the treatments were associated with lesion improvement or survival.

As summarized by the authors: the risk factors are the 4Ws:- Warfarin, White race, Women and overWeight in patients with normal renal function. Interesting that warfarin is a risk factor in both renal and non renal calciphylaxis. It’s perhaps about time the renal community embrace apixaban over warfarin

A larger set of risk factors exists that were mentioned in the recent NEJM review in 2018 that also add: ESRD( what we see), hypercalcemia( probably in setting of CKD as pure – not really evident), DMII, hyperparathyroidism( we have seen this), Vitamin K deficiency, Autoimmune disorders, metastatic cancers, rapid weight loss, skin trauma to name a few.

Check out this interesting tweetorial from ISN education on this topic