Hemodynamic effects of carbon dioxide during intermittent positive-pressure ventilation in horses
Search for other papers by Ann E. Wagner in
Current site
Google Scholar
PubMed
Search for other papers by Richard M. Bednarski in
Current site
Google Scholar
PubMed
Search for other papers by William W. Muir III in
Current site
Google Scholar
PubMed
SUMMARY
The hemodynamic effects of high arterial carbon dioxide pressure (PaCO2) during anesthesia in horses were studied. Eight horses were anesthetized with xylazine, guaifenesin, and thiamylal, and were maintained with halothane in oxygen (end-tidal halothane concentration = 1.15%). Baseline data were collected while the horses were breathing spontaneously; then the horses were subjected to intermittent positive-pressure ventilation, and data were collected during normocapnia (PaCO2, 35 to 45 mm of Hg), moderate hypercapnia (PaCO2, 60 to 70 mm of Hg), and severe hypercapnia (PaCO2, 75 to 85 mm of Hg). Hypercapnia was induced by adding carbon dioxide to the inspired gas mixture. Moderate and severe hypercapnia were associated with significant (P < 0.05) increases in aortic blood pressure, left ventricular systolic pressure, cardiac output, stroke volume, maximal rate of increase and decrease in left ventricular pressure (positive and negative dP/dtmax, respectively), and median arterial blood flow, and decreased time constant for ventricular relaxation. These hemodynamic changes were accompanied by increased plasma epinephrine and norepinephrine concentrations. Administration of the β-blocking drug, propranolol hydrochloride, markedly depressed the response to hypercapnia. This study confirmed that in horses, hypercapnia is associated with augmentation of cardiovascular function.
| All Time | Past Year | Past 30 Days | |
|---|---|---|---|
| Abstract Views | 0 | 0 | 0 |
| Full Text Views | 14246 | 14151 | 41 |
| PDF Downloads | 37 | 20 | 0 |
