| Popis: |
Summary Current methods for monitoring the coronary circulation employ two techniques: (1) measurement of coronary sinus blood flow and content of substances known to be altered (for example, venous oxygen content) or produced (for example, lactate ion) during episodes of myocardial ischemia, or (2) use of radioisotopes to measure changes in coronary perfusion to areas of the myocardium at risk for ischemia. The first method, employing the coronary sinus thermodilution catheter, suffers from a lack of specificity for blood flow in regions of myocardium, but is sensitive for ischemia of sufficient global magnitude to cause changes in coronary sinus content of the measured variables. Data provided by this monitor are retrospective in nature, since the intraoperative assay of substances such as lactate ion is not widely available. Nevertheless, the information has been useful in determining which anesthetic drugs and combinations have the potential to exacerbate or avoid ischemia in patients at risk. Its future use will likely be directed at the further investigation of effects of various anesthetic agents and surgical interventions on the production of myocardial ischemia and as a tool to compare the sensitivity of other monitors for the detection of myocardial ischemia. Radioisotope flow scanning is both sensitive and specific for the presence of myocardial ischemia, but complex requirements for the use of a radioactive isotope restrict its general applicability. |
