Describe the role of the kidneys in the excretion of non-volatile acid.
This is a complex but essential area of physiology for intensive care practice. It was expected
candidates would indicate that non-volatile acids are those not able to eliminated by the lungs
(lactate, sulphate, phosphate and ketone bodies). The kidney plays a central role via bicarbonate
(resorbing filtered bicarbonate and generating “new” bicarbonate = acid excretion). It was
expected candidates could detail the processes in various parts of the renal tubules and the role
or urinary buffers (dibasic phosphate and ammonia).
While a number of candidates were able to provide some of the details of ion transports in the
kidney, few showed understanding of the overarching concepts of the proximal bicarbonate
reabsorption being necessary to allow the distal acid excretion.