Acute but not chronic metabolic acidosis potentiates the acetylcholine-induced reduction in blood pressure: an endothelium-dependent effect

Metabolic acidosis has profound effects on vascular tone. This study investigated the in vivo effects of acute metabolic acidosis (AMA) and chronic metabolic acidosis (CMA) on hemodynamic parameters and endothelial function. CMA was induced by ad libitum intake of 1% NH4Cl for 7 days, and AMA was induced by a 3-h infusion of 6 M NH4Cl (1 mL/kg, diluted 1:10). Phenylephrine (Phe) and acetylcholine (Ach) dose-response curves were performed by venous infusion with simultaneous venous and arterial blood pressure monitoring. Plasma nitrite/nitrate (NOx) was measured by chemiluminescence. The CMA group had a blood pH of 7.15±0.03, which was associated with reduced bicarbonate (13.8±0.98 mmol/L) and no change in the partial pressure of arterial carbon dioxide (PaCO2). The AMA group had a pH of 7.20±0.01, which was associated with decreases in bicarbonate (10.8±0.54 mmol/L) and PaCO2 (47.8±2.54 to 23.2±0.74 mmHg) and accompanied by hyperventilation. Phe or ACh infusion did not affect arterial or venous blood pressure in the CMA group. However, the ACh infusion decreased the arterial blood pressure (ΔBP: -28.0±2.35 mm Hg [AMA] to -4.5±2.89 mmHg [control]) in the AMA group. Plasma NOx was normal after CMA but increased after AMA (25.3±0.88 to 31.3±0.54 μM). These results indicate that AMA, but not CMA, potentiated the Ach-induced decrease in blood pressure and led to an increase in plasma NOx, reinforcing the effect of pH imbalance on vascular tone and blood pressure control.

Modelo animal experimental para adiestramiento en realización anastomosis extra intraracraneales e intracraneales, con técnicas microquirúrgicas / Experimental animal model for training in performing extra-intracranial and intracranial anastomosis, using microsurgical techniques

Las técnicas de anastomosis extra e intracraneales se han utilizado desde los aٌos 70 para el manejo de diferentes patologيasvasculares, que van desde la enfermedad cerebrovascular hasta la exclusiَn de aneurismas y malformaciones arteriovenosasde la circulaciَn o el manejo de condiciones como la enfermedad de Moya Moya. Si bien se ha cuestionado su aplicaciَnen algunas de estas patologيas hoy en dيa se sabe que constituyen una opciَn terapéutica. Las técnicas descritas requierende un entrenamiento especializado del Neurocirujano en el laboratorio de microcirugيa, entrenamiento que no siempre estلal alcance de todos los residentes. Existen dilemas éticos en cuanto al uso de animales y es poco probable que durante losaٌos de formaciَn el residente tenga la oportunidad de realizar anastomosis vasculares en el quirَfano dada la complejidadde estos procedimientos. En el presente artيculo se describe la técnica quirْrgica y microquirْrgica para la realizaciَn de unbypass extra e intracraneal en un modelo animal (cabeza de cerdo), donde se describe paso por paso el procedimiento ylos utensilios con los que debe contar el estudiante. Se hace una revisiَn de la literatura acerca de la patologيa vascular, lastécnicas de bypass y las particularidades de la anatomيa de estos animales.

Extracranial-intracranial bypass techniques have been used since the 70’s for the handling of different vascular diseases, fromcerebrovascular disease to the exclusion of aneurysms and arteriovenous malformations from the circulation or the managementof conditions such as Moyamoya disease. Although its application has been questioned in some of these diseases weknown now that this technic constitutes a therapeutic option. The described techniques require specialized training of the neurosurgeonin the of microsurgery laboratory, training that is not always available to all residents. There are ethical dilemmasregarding the use of animals and it is unlikely that during the formative years the resident may have the opportunity to performvascular anastomosis in the operating room because of the complexity of these procedures. In this article we describe thesurgical and microsurgical techniques for carrying extra- intracranial bypass in an animal model (pig’s head), and outline stepby step the procedure and utensils which the student must have. It is a review of the literature on vascular disease, bypasstechniques and peculiarities of the anatomy of these animals.