Metabolism
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Life-threatening acidosis in an alcoholic - and in a hunger striker given intravenous glucose
PC is a 50 year old man, 174 cm tall and weighing 105 kg. He is an engineer, and works on secondment in one of the strict Islamic states in the Gulf, where alcohol is prohibited.
At the beginning of August he returned to England for his annual leave. According to his family, he behaved as he usually did when on home leave, consuming a great deal of alcohol and refusing meals. He was known to be drinking 2 litres of whiskey, two or three bottles of wine, and a dozen or more cans of lager each day; he refused most meals and his solid food consisted mainly of sweets and biscuits.
On September 1st he was admitted to the Emergency Department of University College Hospital, semi-conscious, and with a rapid respiration rate (40 /min). His blood pressure was 90/60 and his pulse rate was 136 /min. His temperature was normal (37.1 °C). Emergency blood gas analysis revealed severe acidosis: pH 7.02 and base excess -23.
(The base excess is the amount of acid required to return blood pH to the normal range of 7.35 - 7.45 - a negative base excess indicates acidosis)
Why do you think he was breathing rapidly?
The usual response to acidosis is to increase the rate of breathing, so as to expel carbon dioxide, and so shift the equilibrium below to the left, lowering the hydrogen ion concentration in the bloodstream, and so raising plasma pH.
He was transferred to ITU and given intravenous bicarbonate.
Why do you think was he given intravenous bicarbonate?
Providing bicarbonate will permit the equilibrium above to shift to the left, providing carbon dioxide to be exhaled, and so raising plasma pH.
His pulse rate remained high, and his blood pressure low, so emergency cardiac catheterisation was performed; this revealed a cardiac output of 23 litres /min (normal 4 - 6). A chest X-ray show significant cardiac enlargement.
Why do you think his blood pressure was so low?
Both alcohol and acidosis cause vasodilatation, so that the blood pressure falls as blood is pumped by the heart into a arteries that are wider, and so offer less resistance to blood flow.
Why do you think his pulse rate and cardiac output were so high?
This is to compensate for the lower blood pressure caused by vasodilatation - pumping faster, and with a greater stroke volume, will permit a higher blood pressure to be achieved.
Why do you think he showed cardiac enlargement?
This is again compensation / adaptation. We have to assume that he has been drinking heavily for a considerable time (probably also when not on leave, even though it was illegal). Consequently his heart has been pumping harder and faster in an attempt to maintain blood pressure, and this has led to hypertrophy of cardiac muscle and hence enlargement of his heart.
The following results (all as mmol /L) were reported by the Clinical Chemistry laboratory, on a blood sample taken when he arrived in the Emergency Department:
PC |
reference range |
|
| glucose | 7.6 |
3.5 - 5.0 |
| sodium | 142 |
131 - 151 |
| potassium | 3.9 |
3.4 - 5.2 |
| chloride | 91 |
100 - 110 |
| bicarbonate | 5.0 |
21 - 29 |
| lactate | 18.9 |
0.9 - 2.7 |
| pyruvate | 2.5 |
0.1 - 0.2 |
His fasting blood glucose is above normal, which might indicate diabetes mellitus (which might be expected in an obese middle aged man), but we have no further evidence, and the most striking abnormalities are the low chloride and bicarbonate and very high lactate and pyruvate.
The low plasma bicarbonate is the result of hyperventilation in an attempt to compensate for the acidosis, as discussed above.