The following blood results are from a 78-year-old female with Type 2 diabetes and chronic renal failure presenting with breathlessness. Her GP has been treating her with flucloxacillin for cellulitis of her lower limbs.
Parameter |
Patient Value |
Normal Adult Range |
||
Urea |
15.3 mmol/L* |
3 – 8 |
||
Creatinine |
309 μmol/L* |
45–90 |
||
Sodium |
139 mmol/L |
134 – 146 |
||
Potassium |
4.4 mmol/L |
3.4 – 5.0 |
||
Chloride |
115 mmol/L* |
100 – 110 |
||
Glucose |
12.1 mmol/L* |
3.0 – 5.4 |
||
pH |
7.11* |
7.35– 7.45 |
||
PCO2 |
13 mmHg (1.7 kPa)* |
35– 45 (4.6 – 6.0) |
||
Bicarbonate |
4 mmol/L* |
22–27 |
||
Base Excess |
-24 mmol/L* |
-2 – +2 |
||
Lactate |
0.6 mmol/L |
< 2.0 |
||
Measured osmolality |
309 mOsm/L* |
280 – 300 |
a) Describe the acid-base abnormalities in the above results.
b) List three possible causes for this biochemical disturbance.
a) Severe compensated metabolic acidosis with a raised anion gap (! 20), normal osmolar gap and Δ gap 0.4 (Δ gap suggests mixed AG and NAG MA or renal failure)
b)Possible causes
Let us dissect these results systematically.
However, we are supplied with a measured osmolality, which is high - 309 mOsm/L. Is there an osmolar gap? If we calculate the osmolality from the EUCs, we arrive at a value of (139 × 2 + urea + glucose) = 305.4 mOsm/L. So... there is no osmolar gap.
Thus, the only possible explanations must be
Warnock DG. Uremic acidosis. Kidney Int. 1988 Aug;34(2):278-87.
Relman, Arnold S., Edward J. Lennon, and Jacob Lemann Jr. "Endogenous production of fixed acid and the measurement of the net balance of acid in normal subjects." Journal of Clinical Investigation 40.9 (1961): 1621.
Laffel, Lori. "Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes." Diabetes/metabolism research and reviews 15.6 (1999): 412-426.
Elisaf, Moses S., et al. "Acid-base and electrolyte disturbances in patients with diabetic ketoacidosis." Diabetes research and clinical practice 34.1 (1996): 23-27.
Dempsey GA Lyall HJ, Corke CF, Scheinkestel CD. Pyroglutamic acidemia: a cause of high anion gap metabolic acidosis. Crit Care Med. 2000Jun;28(6):1803-7.
Duewall, Jennifer L., et al. "5-Oxoproline (pyroglutamic) acidosis associated with chronic acetaminophen use." Proceedings (Baylor University. Medical Center) 23.1 (2010): 19.
Akhilesh Kumar and Anand K. Bachhawat Pyroglutamic acid: throwing light on a lightly studied metabolite ,SPECIAL SECTION: CHEMISTRY AND BIOLOGY. CURRENT SCIENCE, VOL. 102, NO. 2, 25 JANUARY 2012. 288