Question 18.1

An 81 year old woman is admitted to the ICU with a 24 hour history of altered mental  state and confusion. She has a history of type II diabetes  managed with metformin. The following blood results were taken  on admission.

Arterial blood


Reference values





31 mmHg (4.0 kPa)

40 mmHg       (5.3-5.7 kPa)


90 mmHg (12.0 kPa)

80-100 mmHg (10.5-13.0 kPa)

HCO3 -


22-33 mmol/L



135 -145 mmol/L



3.2-4.5 mmol/L

Cl -


100-110 mmol/L



3.0-8.0 mmol/L



50-100 micromol/L



3.0-7.8 mmol/L



< 2 mmol/L

a. Which clinical condition  is most consistent  with the above data? - Justify your answer from the results provided.

b. List 3 complications of this condition.

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College Answer

a. Which clinical condition  is most consistent  with the above data? - Justify your answer from the results provided.

Answer: Non ketotic hyper osmolar state

•    Marked hyperglycaemia (higher than usually observed DKA) plasma glucose may be >55mmol/L.
•    Hyperosmolarity (by definition osmolarity should be >320)
•    Relatively normal pH/HCO3 suggesting non ketotic state. A small anion gap acidosis may be present secondary to lactate.

b. List 3 complications of this condition.

•    Cerebral oedema:
•    Vascular thrombosis:
•    Electrolyte derangements in particular hypokalemia, dysnatraemia.
Hyperchloremia from saline administration.
•    Intercurrent events such as sepsis, aspiration,  myocardial infarction, iatrogenic (
eg vascular access related complication)
•    Hypotension and shock due to intravascular volume depletion or inadequate resuscitation.


To analyase this gas, let us turn to the well-rehearsed bedside rules for blood gas compensation.

So, this appears to be a metabolic acidosis.

The respiratory compensation for a HCO3- of 20 should be (1.5 x 20)+8, or 38 mmHg; thus, there is also a mild respiratory alkalosis.

The anion gap is raised (18.9); the delta ratio is 1.7 suggesting that the metabolic alkalosis is almost entirely due to the unmeasured anions.

The lactate is raised (4.8) and this accounts for much of the rise in the anion gap. The rest can be blamed on the non-volatile acids retained in renal failure. There is probably little ketosis, as the pH is essentially normal (whereas in ketoacidosis one would expect a profound acidosis).

In summary, after reading the question again, one might come to the conclusion that this woman has the following combination of problems:

  • Hyperosmolar hyperglycaemic state
  • Metformin-induced lactic acidosis, due to decreased renal clearance of metformin, and probably also due to hypovolemic shock

The college did not give us a serum osmolarity, but we are expected to infer from the BSL that it is high.

Complications of HONK are discussed in greater detail elsewhere.

In brief summary, they are as follows:

  • Cardiac arrest
  • Cardiovascular collapse and shock
  • Myocardial infarction
  • Stroke
  • Cerebral oedema and brain injury
  • Venous thrombosis (particularly hideous is the possibility of dural sinus thrombosis)


Hyperglycemic Comas by P. VERNON VAN HEERDEN from Vincent, Jean-Louis, et al. Textbook of Critical Care: Expert Consult Premium. Elsevier Health Sciences, 2011.

Oh's Intensive Care manual: Chapter 58  (pp. 629) Diabetic  emergencies  by Richard  Keays

Umpierrez, Guillermo E., Mary Beth Murphy, and Abbas E. Kitabchi. "Diabetic ketoacidosis and hyperglycemic hyperosmolar syndrome." Diabetes Spectrum15.1 (2002): 28-36.

ARIEFF, ALLEN I., and HUGH J. CARROLL. "Nonketotic hyperosmolar coma with hyperglycemia: clinical features, pathophysiology, renal function, acid-base balance, plasma-cerebrospinal fluid equilibria and the effects of theraphy in 37 cases." Medicine 51.2 (1972): 73-94.