A previously well 10 year old boy presented to the emergency department following a 6 hour period of vomiting. His parents say that he has been feeling generally unwell for the last week and has lost some weight. On examination he is found to have "sighing" hyperventialtion and to have a reduced level of consciousness - only responding to a sternal pressure by moaning. Urgent blood tests show the following:
Blood test results
Haematology
Biochemistry
Venous Blood Gas
Hb 17.5 g/dl
Na 136
pH 7.06
WBC 23.4 x 109/l
K 6.4
Bicarb 9.2
Plt 429
Ur 12.5
Base Excess -14.8
Cr 112
Glucose 33.5 mmol/l
Q1. What is the diagnosis?
Q2. Why is he hyperventilating?
Diabetic ketoacidosis.
Kussmaul respiration (secondary to acidosis.)
Diabetic ketoacidosis (DKA) is a life-threatening emergency and unfortunately is a common presentation of type 1 diabetes. Lack of insulin causes hyperglycaemia and eventually an uncontrolled catabolic state with the production of ketone bodies. DKA can be precipitated by an intercurrent illness.
The blood test clues to the diagnosis are a low pH (acidosis). The acidosis is metabolic as shown by the low bicarbonate and large base excess (large negative). Hyperglycaemia is shown by the high blood glucose. The high serum potassium is frequently found in DKA (although total body potassium is usually depleted). Finally the high white blood cell count is a well recognised feature of DKA and does not necessarily indicate infection.
A deep "sighing" respiration can be seen in DKA (and other conditions that cause a metabolic acidosis). This is called Kussmaul respiration. It is an attempt to compensate for the acidosis by "blowing-off" carbon dioxide.
