Monitoring of cardiac output by thermodilution after open-heart surgery.

One hundred twenty-five separate cardiac output determinations were obtained after open-heart surgery in 10 patients by simultaneous use of thermodilution and dye-dilution techniques. Mean thermodilution cardiac output was 1.6 per cent greater than mean dye-dilution cardiac output (5.24 versus 5.16 L. per minute). Reproducibility of thermodilution cardiac output (coefficient of variation, 8.6 per cent) was superior to that of dye-dilution cardiac output (coefficient of variation, 12.3 per cent) for outputs ranging from 2.5 to 8.7 L. per minute (p less than 0.001). Linear regression analysis revealed a correlation showing that COtd = 0.86 COdye + 0.80 (r = 0.9, p less than 0.001) and indicating a similarity between thermodilution and dye-dilution output figures except in extremely low output states. In such cases, thermodilution cardiac output becomes progressively larger than dye-dilution cardiac output. The results indicate that thermodilution cardiac output is a valid method for determining cardiac output in the rapidly changing clinical setting following cardiopulmonary bypass. Clinical applications of this technique include evaluation of the efficacy of inotropic agents, effectiveness of intra-aortic balloon counterpulsation, and status of the low output syndrome postoperatively. Routine use in patients with Class III or IV cardiac disease appears justified.

Use of autologous fascia lata as a pericardial substitute following open-heart surgery.

Thirteen patients requiring repeat open-heart surgery had autologous free fascia lata grafts implanted to effect complete pericardial closure. In four patients, the graft was used to augment the pericardial space because of myocardial failure and enlargement. In the remainder, fascia lata was used because shrinkage, scarring, or absence of the pericardium from prior operation prevented primary closure. No hemodynamic problems related to implantations of the grafts were seen. The harvesting of the grafts produced no functional deficits, and complications at the donor site were insignificant. Complete pericardial closure with fascia lata protects underlying myocardial structures (i.e., saphenous vein grafts) in the event that further reoperation for bleeding or infection is required. In addition, it provides for compartmentalization of the mediastinum, allowing accurate assessment of the site of postoperative bleeding.

Cardiac output determination after cardiac operation. Lack of correlation between direct measurements and indirect estimates.

Ninety-two mean thermodilution cardiac indices were determined in 25 patients following cardiac operations. Arterial and venous blood gases, hematocrit, body temperature, central venous pressure, left atrial pressures, urine output, heart rate, and mean arterial pressure were simultaneously recorded. Six variables, arterial and venous pH, arterial and venous PCO2, venous PO2, and temperature, showed significant simple correlations with cardiac index, but the degree of correlation was inadequate for use of these variables as reliable indices of cardiac function. When stepwise multiple regression analysis was performed, two variables, venous PO2 and left atrial pressure were associated with the best correlation with cardiac index, such that CI = 0.073 PO2V -- 0.060 LAP + 1.39 (r = 0.60, p less than 0.001). When measured values for venous PO2 and left atrial pressure were substituted into this equation, a "predicted" value for cardiac index could be obtained with only slightly improved reliability. The data indicate that indirect estimation of cardiac output by measurement of the various laboratory parameters described above is not sufficiently reliable for clinical use. The importance of obtaining direct measurements of cardiac output by thermodilution or other means in order to properly evaluate postoperative cardiac function is stressed.

Effect of perioperative low-dose heparin administration on the course of colon cancer.

There is evidence that drugs that inhibit blood coagulation or platelet activity may retard or prevent the recurrence of cancer in experimental animals and in patients. The data for 230 patients who underwent surgical resection for primary adenocarcinoma of the colon (Dukes B and C) during 1973 to 1977 were studied retrospectively to determine whether low-dose heparin given for prophylaxis of thromboembolism altered the interval to or prevalence of recurrence. Perioperative low-dose subcutaneous heparin was given to 180 patients, and 50 patients received no heparin. The groups were comparable in age, sex, extent of disease, and use of adjuvant chemotherapy or radiation therapy. Disease recurred in 54 of 180 patients (30%) who received heparin and 18 of 50 patients (36%) who did not receive heparin. This difference was not significant (chi2 = 0.6551, P = 0.418). The interval from surgery to recurrence of cancer was slightly longer in the heparin group (790 days) than in the nonheparin group (638 days), but this difference was not statistically significant (P = 0.268). Life table analysis revealed a significantly lower overall mortality rate among patients who received heparin (P less than 0.05), although there was no difference between the two groups in rate of deaths from colon cancer.

Do patients with thromboembolic disease have circulating platelet aggregates?

Reports of circulating platelet aggregates (ie, microemboli) in thromboembolism and other vascular disorders are based on a method (Wu and Hoak , 1974) in which venous blood is collected via scalp vein needle and tubing into either formaldehyde, which fixes aggregates, or EDTA, which disperses them. The ratio of platelet counts in platelet-rich plasma (PRP) from the two blood samples after centrifugation is interpreted as a measure of platelet aggregates in the circulation in vivo. We compared this standard Wu and Hoak technique with a modified one, in which blood was drawn directly into a syringe, and with a third method that avoided centrifugation by counting single platelets in whole blood. Both modified techniques could detect aggregates generated in vitro with adenosine diphosphate (ADP). In 12 normal subjects, the three methods were equivalent, but in 37 patients with thromboembolic disorders, the standard Wu and Hoak method gave a lower ratio than the other methods. Similar results were found in a subset of eight patients with myocardial infarction. Heparin treatment of patients did not influence the results. The data suggest that formation of platelet aggregates occurred during venipuncture. Platelets may be hyperactive in patients with thromboembolic disease and may form aggregates in vitro during collection, but the concept of chronic microembolism in such patients should be reassessed.