Aortic stenting in the growing sheep causes aortic endothelial dysfunction but not hypertension: Clinical implications for coarctation repair.

BACKGROUND: Stent implantation is the treatment of choice for adolescents and adults with aortic coarctation (CoAo). Despite excellent short-term results, 20%-40% of the patients develop arterial hypertension later in life, which was attributed to inappropriate response of the aortic baroreceptors to increased stiffness of the ascending aorta (ASAO), either congenital or induced by CoAo repair. In particular, it has been hypothesized that stent itself may cause or sustain hypertension. Therefore, we aimed to study the hemodynamic and structural impact following stent implantation in the normal aorta of a growing animal. METHODS: Eight female sheep completed the study and a stent was implanted in four. Every 3 mo we measured blood pressure of the anterior and posterior limbs and left ventricular function by echocardiography. Twelve months later invasive pressure was measured under baseline and simulated stress conditions. Expression of genes indicating oxidative stress (OS), endothelial dysfunction (ED) and stiffness, as well as pathological examination were performed in ascending (ASAO) and descending aorta (DSAO). RESULTS: SOD1 and MMP9 gene expression were higher in ASAO of the stented animals, compared to DSAO and controls, while NOS3 was decreased. No differences were found in blood pressure and echocardiographic parameters. No histological differences were found in the aorta of the two groups of animals. CONCLUSIONS: Stent does not affect central and peripheral hemodynamics, cardiac structure and function even in the long term. However, the finding of markers of OS and increased stiffness of ASAO, proximal to the stent, points to molecular mechanisms for increased cardiovascular risk of patients with stented CoAo.

Clinical evaluation of an end-tidal target-controlled infusion closed-loop system for isoflurane administration in horses undergoing surgical procedures.

A new volatile anaesthetic agent delivery system was tested in 15 horses undergoing scheduled surgical procedures. The delivery system consisted of a laptop computer (with dedicated software), a computer-controlled syringe driver (loaded with liquid isoflurane) connected to the inspiratory arm of a large-animal circle breathing system and a respiratory gas monitor, providing isoflurane end-tidal concentrations (ET(measured)) every 20 s to the computer. Following induction and connection to the breathing system, mechanical ventilation was started. The bodyweight (BW), fresh gas flow, breathing system and ventilator volume, and end-tidal isoflurane target (ET(target)) were entered into the computer. Using Lowe's equation, the software calculated the prime dose to be delivered by the syringe driver over 2 min. After this, the system delivered each minute the amount of isoflurane as determined by the following equation: Isoflurane (mL) = {2 × λ(B/G) × (200 × BW(0.75)) × (ET(target) - ET(measured)) + (fresh gas flow - (BW(0.75) × 0.07)) × (ET(measured))}/206. A fresh gas flow of 4 L oxygen min(-1) was administered until the inspired fraction of oxygen reached 0.7, and was then decreased. A target of 1.5% end-tidal isoflurane was initially used and subsequently adjusted to the clinical requirements. The system performance was evaluated using the median prediction error (MDPE) and the median absolute performance error (MDAPE), which were -3.6% and 5.29%, respectively. It was concluded that this system was useful to achieve end-tidal target-controlled infusion of isoflurane during equine anaesthesia.