This occurs when the brain does not receive enough oxygen. It may occur
secondary to respiratory failure. It may be preceded by being unconscious
or by feeling faint. The criterion is
brain O2 delivery < 60 ml/min
This occurs when osmosis causes cells to expand; commonly secondary to
hyponatraemia. It may be preceded by confusion. The criterion is
ICF volume > 45 litres.
Often fluid overload can lead to a very high right atrial pressure; according to the
Starling curve's shape, this compromises cardiac output, and leads
to heart failure and cardiogenic shock.
The criterion is
brain O2 delivery < 60 ml/min and RAP > 9 mmHg
Dehydration may lead to low blood volume, and this decreases the
right atrial pressure. This impairs ventricular filling, decreases cardiac
output, and leads to cardiogenic shock. It is preceded by tachycardia,
hypotension and fainting.
The criterion is
Brain O2 delivery < 60 ml/min and RAP < 2.5 mmHg
If the blood pressure is too high, a haemorrhagic stroke is likely; it
may be precipitated by fluid overload or sympathetic overactivity.
It may be preceeded by headache. The criterion is
Arterial pressure > 220 mmHg
The brain cannot function when deprived of both glucose and ketones.
A hypoglycaemic episode usually follows an insulin overdose (relative
to glucose intake and requirement). It is preceded by feeling faint and
unconsciousness. The criterion is
blood glucose < 0.2 mmol/L