Describe the physiological consequences and responses after an acute haemorrhage of 2.0 litres in a healthy 70kg adult if there is no immediate fluid resuscitation.
To adequately answer this question, candidates must be able to demonstrate that they
recognised this to be a major haemorrhage. When a weight and a volume are supplied it is
expected the percentage blood loss would be calculated and the shock graded or the
haemorrhage at least described as severe. Often the consequences were omitted.
Consequences were best described in organ systems e.g. CV, renal, metabolic. Many
candidates failed to mention the patient would be hypotensive and tachycardic.
A good answer should include mention, and provide explanations, of the mechanisms for the
following compensatory responses:
· Activation of both baroreceptors and chemoreceptors and their consequences
· The sympathetic nervous system response
· Fluid shifts
· Renal effects - most candidates mentioned the urine output would be decreased but
did not provide a mechanism for this
Endocrine effects, eg secretion and actions of ADH, ACTH/Cortisol
Reference: Textbook of Medical Physiology, Guyton and Hall, Foundations of Anaesthesia:
Basic Clinical Science, Hemmings and Hopkins