The patient is a 69 year old woman admitted with abdominal pain and nausea. She may have lost weight. She has no known past medical history and is taking no medications. Her labs give many clues:
| Electrolyte panel | |||||
|---|---|---|---|---|---|
| Na | 142 | Cl | 113 | BUN | 106 |
| K | 6.5 | HCO3 | 11 | creat | 9.1 |
| Blood Sugar | 79 |
Alb 3.2; Calcium 5.1
ABG on room air
| ABG | |
|---|---|
| pH | 7.23 |
| pCO2 | 23 |
| pO2 | 80 |
| HCO3 | 10 |
So please address these questions: 1. What is the acid-base disorder? 2. Predict other laboratory testing? 3. What would you do at admission?
{ 5 comments… read them below or add one }
This new acid base problem seems to fall under the category of an old acid base problem with a twist.
Calculations:
1. Metabolic acidosis by ABG
2. AG –> 18
3. Delta –> 20 (with adjustment for albumin nl AG = 9)
4. Expected resp compensation (PCO2) –> 23
5. Corrected Ca –> 5.7
Basic Acid Base Conclusion: Gap acidosis with underlying nongap acidosis with appropriate respiratory compensation.
Comments: Renal failure driving gap acidosis and given degree of low corrected calcium & acidosis, I suspect phos will be ~12. Underlying nongap acidosis due to renal bicarb loss and points more toward component of acute renal failure as no diarrhea mentioned. Abdominal pain & nausea likely early symptoms of uremia.
She needs an ECG with K >6.0. I would also get a urinalysis (if RBCs & protein present spin urine to look for RBC casts), place a foley (vs in & out cath for post void to r/o obstruction), renal US (to look at kidney size), check CK, & obtain records to get info on previous BUN/Cr. I would contact the nephrology fellow for dialysis, place access, and temporize K and HCO3 with kayexalate and bicarb gtt.
If suspected need for longterm HD, over the next few days I’d get Fe studies, HbsAg, iPTH.
Thanks for this case, I look forward to reading your solution.
1) anion gap metabolic acidosis (appropriate resp compensation) with uraemia
Note: hyperkalaemia, severe hypercalcaemia with a corr Ca of 5.7 (!), severe renal impairment (?acute on chronic)
Is the hypercalcaemia causing profound volume loss, abdo pain & vomiting leading to ARF? Or is CRF causing the hypercalcaemia? -> PTH levels are a way to help differentiate this.
2)
anion gap acidosis:
- need to measure lactate, ketones (is this multifactorial?)
- exclude over the counter medications, drugs, etc by taking a history (eg aspirin, vitamin D, antacids)
renal failure:
- work out if it is pre-, post- or intra-renal
-> IDC first followed by renal USS & doppler would be helpful
-> CVP measurement and patient response to filling are both a therapeutic and diagnostic manoeuvre
-> urinalysis, microscopy & culture to look for nephritis, infection, proteinuria, casts are mandatory
-> septic screen, LFT, drug screen
hypercalcaemia:
- the main concern would be malignancy (myeloma, bony mets, PTHrP/paraneoplastic syndromes) especially given the Ca of 5.7 and history of weight loss vs primary hyperparathyroidism (seems unlikely given the extent of hypercalcaemia, but possible) vs tertiary hyperparathyroidism (due to CRF & metabolic bone diseases). Consideration shoudl be given to rarer causes such as hypocalciuric hypercalcaemia, vit D ingestion etc due to just how severe the hypercalcaemia is
- It is mandatory to check a phosphate level to see where in the and a Bone Alkaline Phosphatase (look for increased bone turnover eg myeloma, bony mets & Paget’s)
- PTH level would differentiate [malignancy & rare causes] from [primary/tertiary hyperparathyroidism]
- urine calcium, parathyroid scan, myeloma workup and measurement of PTHrP are probably valuable
3)
A, B: she is mildly hypoxic and profoundly acidotic, so some oxygen would probably make her more comfortable!
C: the priorities then are to measure, monitor & correct volume state- the patient is likely to be severely hypovolaemic given the degree of hypercalcaemia and renal impairment- though this cannot be simply assumed. Large bore cannula, in-dwelling catheter for urine output, a central venous catheter are required for how unwell this patient is, as well as the consideration of the need for dialysis or haemofiltration. Continuous ECG monitoring should be started and regardless of the current 12 lead ECG, insulin, dextrose and resonium should be administered. Calcium gluconate is contraindicated in the situation of hypercalcaemia.
Next, the hypercalcaemia should be corrected with intravenous bisphosphonate. Work up shoudl be done for CRF & dialysis including FBE & film, mag & phos, TTE, 24hr urine electrolytes, protein, creatinine.
So as it turns out I was using Australian units for calcium, thus hypocalcaemia!
That makes things much easier.
The hypocalcaemia is probably due to 2o hyperPTH because of chronic renal disease. the acidosis is also probably uraemia + CRF.
My guess is that the phosphate would be high though i’m nto sure HOW high.
On admission, I suppose workup for dialysis, CXR, 24hr urine collection to ascertain accurate renal function & quantitate protein, urinalysis, an IDC and CVC to measure volume state
(also give some IV sodium bicarb for the acidosis & give insulin, dextrose & resonium)
The patient has acute renal failure with hyperkalemia and metabolic acidosis (HCO3 of 11 mmol/L). She has partly compensatory respiratory alkalosis (pCO2 of 23 mm Hg and pH of 7.23). Despite increased respiratory effort, her pO2 is only 80 mm Hg. The hyperkalemia indicates a significant degree of tissue acidification. She could have some ketoacidosis if she hasn’t been eating much due to her GI problem.
Hyperkalemic renal failure metabolic acidosis typically exhibits negative calcium balance. I predict:
hyperuricemia
hypocalcemia
euphosphatemia or mild hyperphosphatemia
elevated PTH appropriate for the low ionized calcium concentration
urinary pH >7
urinary ketones
urine sediment with renal tubular epithelial cells and possibly tubular casts
Without knowledge of urinary output, I cannot predict plasma or urine osmolalities.
Admission tasks:
electrocardiographic monitoring (hyperkalemia)
glucose and insulin on standby in case or cardiac complications
intravenous bicarbonate to partly reverse metabolic acidosis
intravenous calcium based on ionized calcium result
assessment of oxygenation and pulmonary function
thorough abdominal examination
adbominal imaging and/or ultrasound studies
drug use history (as possible cause of renal failure)
preparation for hemodialysis
comprehensive metabolic panel
nutritional assessment (look for negative nitrogen balance)
serum and urine protein electrophoreses if >1+ protein on dipstick