Hemodynamic effects of carbon dioxide during intermittent positive-pressure ventilation in horses.

摘要: The hemodynamic effects of high arterial carbon dioxide pressure (PaCO2) during anesthesia in horses were studied. Eight anesthetized with xylazine, guaifenesin, and thiamylal, maintained halothane oxygen (end-tidal concentration = 1.15%). Baseline data collected while the breathing spontaneously; then subjected to intermittent positive-pressure ventilation, normocapnia (PaCO2, 35 45 mm Hg), moderate hypercapnia 60 70 severe 75 85 Hg). Hypercapnia was induced by adding inspired gas mixture. Moderate associated significant (P less than 0.05) increases aortic blood pressure, left ventricular systolic cardiac output, stroke volume, maximal rate increase decrease (positive negative dP/dtmax, respectively), median flow, decreased time constant for relaxation. These changes accompanied increased plasma epinephrine norepinephrine concentrations. Administration beta-blocking drug, propranolol hydrochloride, markedly depressed response hypercapnia. This study confirmed that horses, is augmentation cardiovascular function.