Question 9.1

A 75-year-old patient presents with diarrhoea, vomiting and abdominal discomfort. There is a history of previous ingestion of a homemade health tonic.

a)    Explain the following results and provide a rationale for the abnormalities.    (30% marks)


Patient Value

Adult Normal Range





7.35 – 7.45


101 mmHg (13.4 kPa)


20.0 mmHg (2.6 kPa)*

35.0 – 45.0 (4.7 – 6.0)




6.0 mmol/L*

22.0 – 26.0

Base Excess

-22 mmol/L*

-2 to +2


1.0 mmol/L

0.5 – 1.3


120 mmol/L*

135 – 145


5.1 mmol/L*

3.5 – 5.0


90 mmol/L*

95 – 105


41.7 mmol/L*

3.0 – 8.0


1284 μmol/L*

45 – 90

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College answer

Not available.


This homemade tonic. Was it antifreeze? Be honest. Whatever it was, it has caused acute renal failure and severe metabolic acidosis, which means the possibilities are endless.

These results demonstrate:

  • A relatively normal oxygenation
  • There is a severe metabolic acidosis
  • The CO2 is appropriately depressed (the expected CO2 is around 18 using the SBE method, or (1.5×6)+8 = 17 using the classical Boston calculations). 
  • The anion gap is raised,  (120-(90+6) = 24
  • The delta ratio is therefore (24-12)/(24-6) = 0.66, i.e. a mixed metabolic acidosis exists (both high and normal anion gap components are present)
  • There is renal failure, which is clearly subacute, in the sense that it takes a few days for the urea to climb to 40.

This does not fall neatly into any specific toxidrome, except perhaps for ethylene glycol toxicity, where there would be both renal failure and a high anion gap. But that would typically give a spuriously elevated lactate, and anyway people do not usually regard antifreeze as a "health tonic", suggesting some other explanation is required. Salicylate toxicity is probably a better choice, as it could legitimately occur as the result of drinking an infusion of willow bark, which probably contributed to the death of Ludwig von Beethoven.

Broadly, there are two possibilities: either something has either attacked the kidneys directly, or merely caused diarrhoea and vomiting so severe that the patient is severely dehydrated and has developed pre-renal failure. In case the reader is interested,  Gabardi et al (2007) and Claure-Del Granado et al (2021) list numerous nephrotoxic complimentary medicines, such as:

  • Chromium picolinate
  • Creatine monohydrate
  • L-lysine
  • Larrea tridentate (Chaparral)
  • Pausinystalia yohimbe (Yohimbe)
  • Salix daphnoides (Willow Bark)
  • Tripterygium wilfordii (Thunder God Vine)
  • Uncaria tomentosa (Cat's Claw)

Thus, a plausible rationale for the abnormalities could be:

  • Self-poisoning with a nephrotoxin
  • Acute renal failure due to this
  • A period of dehydration due to diarrhoea and vomiting which has exacerbated this


Gabardi, Steven, Kristin Munz, and Catherine Ulbricht. "A review of dietary supplement–induced renal dysfunction." Clinical Journal of the American Society of Nephrology 2.4 (2007): 757-765.

Claure-Del Granado, Rolando, and María Espinosa-Cuevas. "Herbal Nephropathy." Nephrology and Public Health Worldwide 199 (2021): 143-154.