The effect of continuous digital hypothermia on lamellar energy metabolism and perfusion during laminitis development in two experimental models

Background: Continuous digital hypothermia (CDH) prevents lamellar failure in the euglycaemic hyperinsulinaemic clamp (EHC) and oligofructose (OF) laminitis models, but the mechanisms remain unclear. Objectives: To evaluate the effects of CDH on lamellar energy metabolism and perfusion in healthy horses and during EHC and OF laminitis models. Study design: In vivo experiment. Methods: Archived samples were used from Standardbred geldings that received no treatment (CON) (n = 8) or underwent EHC (n = 8) or OF (n = 6) laminitis models. Both forelimbs were instrumented with a lamellar microdialysis system, and one forelimb was cooled (CDH) with the other maintained at ambient temperature (AMB). Microdialysate was collected every 6 hours and analysed for glucose, lactate and pyruvate concentrations and lactate to pyruvate ratio (L:P). Microdialysis urea clearance was used to estimate lamellar tissue perfusion. Data were analysed using a mixed-effects linear regression model. Results: Glucose did not change in CDH limbs relative to AMB in CON (P =.3), EHC (P =.3) or OF (P =.6) groups. There was a decrease in lactate (P <.001) and pyruvate (P <.01) in CDH limbs relative to AMB in all groups. L:P decreased in CON CDH relative to CON AMB (P <.001) but was not different in EHC (P =.6) and OF (P =.07) groups. Urea clearance decreased in CDH limbs relative to AMB in CON (P =.002) and EHC (P <.001), but not in OF (P =.4). Main limitations: The EHC model may not mimic natural endocrinopathic laminitis. Conclusions: CDH caused a marked decrease in lamellar glucose metabolism (CON, EHC and OF) and perfusion (CON and EHC) without affecting lamellar glucose concentration. Although cellular energy failure is not a primary pathophysiological event in EHC and OF laminitis models, CDH may act by limiting energy supply to pathologic cellular processes whilst preserving those critical to lamellar homoeostasis.