Effects of Anaesthesia on Renal Function
- Anaesthesia and surgical stress can affect renal function and body fluid regulation indirectly as well as directly.
- Indirect effects occur through influences on haemodynamics, sympathetic activity and humoral regulation - more pronounced than the direct ones.
- Inhalational anaesthetics generally reduce glomerular filtration rate and urine output, mainly by extra-renal effects that are attenuated by pre-operative hydration.
- Opioids, barbiturates and benzodiazepines also reduce glomerular filtration rate and urine output.
- Regional anaesthesia has less effect than general anaesthesia and effects are related to changes in systemic haemodynamics. These peri-operative alterations of renal function are usually transient and clinically insignificant.
- Mechanical ventilation decreases urine volume and sodium excretion to an extent that depends on the increase in intrathoracic pressure, though ADH release, unloading of baroreceptors and activation of the renin-angiotensin system may also be involved.
- The direct effects of anaesthesia which are dose- and agent-dependent include effects on autoregulation of renal blood flow, alteration in the effect of ADH, and effects on tubular transport of sodium and organic acids.
- The only proven direct toxic effect of any anaesthetic agent is the fluoride-related toxicity of methoxyflurane.