Hepatic and renal disease

Low albumin can lower oncotic pressure and leave more unbound drug in blood. The effect depends on the drug; opioids and benzodiazepines are not all equally protein-bound.

My notes and the book favour morphine, hydromorphone and oxymorphone because conjugation avoids the P450 route. That does not guarantee normal clearance in liver disease. Cats have limited morphine glucuronidation, and pathways differ between drugs. Remifentanil is broken down by blood and tissue esterases.

The book favours midazolam over diazepam because its metabolites are less active. Diazepam has potent active metabolites. Propofol redistributes rapidly and may have extrahepatic metabolism. Low albumin may reduce the dose needed when it is titrated to effect. Modern inhalants undergo little hepatic metabolism and leave mainly through the lungs; blood flow and pressure still matter.

Ketamine forms active norketamine, and renal elimination matters. Effects may last longer with CKD. My cat “50% unchanged” cue comes from the book. Ketavet's label says almost exclusively unchanged; the exact fraction remains uncertain.

The book allows selected ketamine use when obstruction will be relieved promptly; ketamine does not remove it. Ketavet's label contraindicates pre-existing hepatic or renal pathology. Alpha-2 agonists increase urine output and are relatively contraindicated if the animal cannot void.

The blanket NSAID warning needs context. Chronic use in selected stable CKD cats has been studied, with proteinuria and gastrointestinal concerns.

Sevoflurane plus soda lime can form compound A, a vinyl ether. My note says cats; the book and SevoFlo leaflet describe rat nephrotoxicity. The book advises avoidance in severe renal disease or higher fresh gas flow. The leaflet warns against long-duration low-flow use and calls for careful monitoring with renal insufficiency.

References

Johnston & Tobias, 2nd ed., Chapters 21–22; van Beusekom et al. 2014; KuKanich et al. 2021; VMD Ketavet/SevoFlo; FDA ULTIVA.