Renal perfusion, oxygenation, and sympathetic nerve activity during volatile or intravenous general anaesthesia in sheep

Background: Global and intra-renal perfusion and oxygenation may be affected by the choice of anaesthetic. We compared the effects of isoflurane with those of propofol and fentanyl on renal blood flow (RBF) and intra-renal perfusion and oxygenation, and assessed how these were associated with renal sympathetic nerve activity (RSNA). Methods: A renal artery flow probe and laser Doppler and oxygen-sensing probes were surgically implanted in the renal medulla and cortex in 20 Merino ewes. RSNA was measured in 12 additional ewes. We compared the effects of volatile or i.v. anaesthesia on global RBF, renal oxygen delivery (RDO ₂ ), intra-renal perfusion, and RSNA with the non-anaesthetised state on postoperative day 3 as control reference. Results: Compared with a non-anaesthetised state, volatile anaesthesia reduced global RBF [–76 (82–68)%], RDO ₂ [−76 (83–71)%], and cortical [–68 (74–54)%] and medullary [–76 (84–72)%] perfusion. I.V. anaesthesia reduced RBF [–55 (67–38)%], RDO ₂ [–55 (65–44)%], and cortical [–27 (45–6)%] and medullary [–35 (48–30)%] perfusion, but to a lesser extent than volatile anaesthesia. Renal PO ₂ was not influenced by anaesthesia, whilst RSNA was elevated during volatile, but not during i.v. anaesthesia. Conclusions: Volatile and i.v. general anaesthesia markedly reduced global RBF, RDO ₂ , and regional kidney perfusion. These effects were greater with volatile anaesthesia, and were paralleled by an increase in RSNA. Our findings suggest a neurogenic modulatory effect of anaesthetics on renal perfusion and oxygenation.