For each case of coma A–E, select the most appropriate option from the following list

A. Option 2 Hypothermia. ‘Accidental’ hypothermia tends to affect people of all ages when immersed in cold water or exposed on land to low temperatures without adequate insulation; it also occurs in elderly people during cold weather, usually when they have suffered an illness such as a stroke which means they lie poorly insulated in a relatively low temperature. Diagnosis requires a low reading thermometer, usually inserted rectally, since a clinical thermometer is shaken down to an initial temperature around 35–36°C and this may be taken as the temperature even though the True temperature is 5–10 degrees below this. The markedly cold skin is an important clue. Treatment of such patients is often unsuccessful since they have the damage produced by hypothermia added to the underlying condition such as a stroke in this case.

B. Option 11 Brainstem death. This diagnosis is only made after careful repeated expert examination and after reversible causes such as Options 2, 8 and 9 have been excluded. Survival of the brainstem would be indicated by preservation of the brainstem corneal and pupillary reflexes, by the presence of nystagmus (jerky eye movements) provoked by stimulation of the vestibular system by the icy saline and by spontaneous breathing movements in the presence of a high carbon dioxide level. (The pre-oxygen fills the functional residual capacity with oxygen to prevent hypoxic damage during removal from the ven-tilator.)

C. Option 6 Diabetic ketoacidosis. This is a typical history of childhood-onset of insulindependent diabetes mellitus. Lack of insulin’s action leads to failure to assimilate absorbed glucose and other nutrients into the body cells, with resulting malnutrition and glycosuria leading to polyuria. In the absence of adequate intracellular glucose, energy produc-tion relies excessively on fat as a substrate and this leads to ketones and a huge excess of hydrogen ions (severe metabolic acidosis with pH 7.1 and bicarbonate down to about a third of normal due to buffering). This in turn leads to vomiting, coma and hyperventila-tion to compensate to some degree for the acidosis by lowering the carbon dioxide level. The blood glucose level would be 5–10 times normal.

D. Option 7 Hypoglycaemia. This patient contrasts with the previous one in that he is known to be a diabetic and his condition suggests a low blood sugar. This is suggested by the hyperdynamic circulation, a compensation for hypoglycaemia (in contrast, ketoacidosis is associated with a weak pulse and circulatory failure). The sweating is also a sympathetic autonomic response to hypoglycaemia. The initial treatment is an intravenous injection of concentrated glucose. Such patients not uncommonly have repeated episodes of unconsciousness due to hypoglycaemia and become known to ambulance personnel.

E. Option 4 Hepatic failure. The major clue here is the jaundice (yellow discolouration) which suggests a hepatic cause of coma. Hepatic failure often causes in the early stages a state similar to alcoholic intoxication and indeed the two could co-exist as excessive alcoholic consumption is a common cause of hepatic failure. However, in this case vomiting of blood has occurred (common in hepatic failure complicated by portal hypertension and oesophageal varices). It is likely that some of the blood lost will have been digested and the products of digestion absorbed from the gut. Digestion and absorption of this high protein load could cause hepatic coma to develop precipitated by toxic products of pro-tein digestion which cannot be eliminated by the liver.