Chung-Yuan Lin

Monitoring of Heparin-induced Anticoagulation with Kaolinactivated Clotting Time in Cardiac Surgical Patients Treated with Aprotinin

High-dose aprotinin appears to enhance the anticoagulant effects of heparin, as documented by increases in the activated clotting times (ACTs) during cardiopulmonary bypass; hence, some authorities have advocated reducing the dose of heparin in patients treated with aprotinin. An in vitro study by our group suggested that the increase of the ACT in the presence of aprotinin and heparin may be due to the use of celite as surface activator. We compared celite and kaolin as surface activators for the measurement of the ACT in cardiac surgical patients treated with aprotinin and in patients given no aprotinin. This double-blind, randomized, placebo-controlled study included 30 patients, of whom 14 received aprotinin and 16 received a placebo. Before, during, and after cardiopulmonary bypass, the ACT was measured with two Hemochron 400 systems with 12 mg of either celite (C-ACT) or kaolin (K-ACT) used as surface activator and with one Hepcon HMS system (HR-ACT), which uses kaolin as activator. The latter also was used for measurement of the blood heparin concentration. The ACTs of blood without heparin did not differ between aprotinin and control patients. During anticoagulation with heparin and cardiopulmonary bypass, the average C-ACTs were 784 +/- 301 s (aprotinin) and 496 +/- 120 s (control) (P < .001); the K-ACTs were 502 +/- 131 s (aprotinin) and 458 +/- 101 s (control) (P > .05); the HR-ACTs were 406 +/- 87 s (aprotinin) and 423 +/- 82 s (control) (P > .05), which was consistently less than C-ACT and K-ACT.(ABSTRACT TRUNCATED AT 250 WORDS)

Thromboelastogram fails to predict postoperative hemorrhage in cardiac patients

To determine the clinical usefulness of the thromboelastogram in the prediction of postoperative hemorrhage in cardiac patients, we related the results of routine coagulation tests (RCTs) and thromboelastography with the amount of chest tube drainage postoperatively in 101 patients requiring cardiopulmonary bypass. Our data indicated that there was no correlation between RCT results and thromboelastographic variables. No single variable of RCTs and thromboelastography correlated well with the amount of chest tube drainage postoperatively. Before the onset of cardiopulmonary bypass, the most frequent abnormalities detected by thromboelastograms were fibrinolysis and hypocoagulability resulting from factor deficiency. Hypercoagulability detected by thromboelastograms occurred in 13% of patients after cardiopulmonary bypass and usually was not detected by RCTs. The incidence of false-negative thromboelastograms and RCT results in patients who had excessive hemorrhage of unknown cause was 46% and 52%, respectively. The incidence of fibrinolysis as detected by thromboelastograms was similar before and after bypass, but only 2 of the 18 patients with fibrinolysis had excessive hemorrhage postoperatively. Our results indicate that neither RCTs nor thromboelastography predicts the likelihood of excessive hemorrhage in patients after cardiopulmonary bypass. The thromboelastographic results should be interpreted cautiously because of the high rate of unreliable results.

Comparison of high-dose thrombin time with activated clotting time for monitoring of anticoagulant effects of heparin in cardiac surgical patients

The activated clotting time (ACT) is routinely used for monitoring of heparin effects during cardiopulmonary bypass (CPB). However, ACT is not a specific assay for heparin and may be influenced by several other factors, which may be misleading with regard to the proper administration of heparin and protamine. In this pilot study, we compared a new test, the high-dose thrombin time (HiTT), with the conventional ACT test for both in vitro and in vivo heparin-induced anticoagulation. Our in vitro results showed that there were heparin dose-dependent increases in ACT and HiTT. Data on 30 adult cardiac patients indicated that HiTT correlated well with heparin concentration both after initial heparin administration and during CPB (r = 0.645 and 0.515). Hypothermia and hemodilution occurring during CPB did not alter HiTT results. ACT also correlated well with both heparin concentration and HiTT before CPB, but the linear relationship was lost during CPB. Our results suggest that HiTT is a useful assay for monitoring heparin effects during cardiac surgery, even during hypothermia and hemodilution.

Experimental treatment of corrosive esophageal burns

Summary Experimental lye burns of the esophagus were produced in 72 cats. Each cat was placed in one of four study groups: Control group; corticosteroid-treated group; group treated with intraluminal splint for 2 wk; and group treated with intraluminal splint for 3 wk. Severe esophageal stricture was observed in the first three groups at 2 wk, 4 wk, and 12 wk after lye burn. No differences in the degree of stricture was observed in control, corticosteroid-treated, or intraluminal-splint (2 wk) groups when comparing stricture formation at 2 and 12 wk after lye burn. In the group treated with an intraluminal splint for 3 wk, stenosis of the esophagus was 1% at 3 wk (at time of removal of splint). At 12 wk, the cats that survived and were killed showed no clinical evidence of esophageal obstruction, and gross examination of the burned area showed an overall stenosis of 3%. Except for a slight mural fibrosis, the histologic picture is that of a well-healed and normal-appearing esophageal tissue. These studies would suggest that treatment with an intraluminal esophageal splint for 3 wk after full-thickness esophageal lye burn would be an effective method of preventing stricture.

In vitro determination of accuracy of cardiac output measurements by thermal dilution

The accuracy of cardiac output (C.O.) measurements by the thermodilution method was evaluated in an in vitro model within a flow range from 1 to 5 liters/min. For C.O. determinations, a 5F Swan-Ganz balloon-tipped thermodilution catheter and a 9520 Edwards computer were used. We made 420 measurements at known flow rates. In serial determinations, we achieved an overall accuracy of 86 to 93% compared to the reference flow; for single determinations, the accuracy ranged from 75 to 85%. The indicator volume (3, 5, or 10 cc) had no influence on the results. The thermodilution determinations at each flow rate were reproducible at between 2.5 and 8.5%. There was no difference in accuracy or reproducibility when ice-cold or room temperature saline was used. Caution in the interpretation of single C.O. determinations in low-flow states, i.e., in pediatric patients, is recommended.

The Prosthetic (Teflon) Central Aortopulmonary Shunt for Cyanotic Infants Less Than Three Weeks Old: Results and Long-Term Follow-up

The expanded microporous polytetrafluoroethylene (PTFE) 4 mm vascular prosthesis has been used to create a central aortopulmonary shunt in 20 critically ill infants less than 3 weeks old. The infants ranged from 1 to 18 days old (5.25 days), and from 1.5 to 4.0 kg (2.9 kg). Conduit length ranged from 2 to 6 cm (4 cm). Sixteen patients had atresia of the tricuspid or pulmonary valve. There were 6 early deaths (30%), only 1 of which was shunt related. The mean preoperative arterial oxygen saturation was 62% (range, 33 to 80%), and mean postoperative saturation was 87% (range, 78 to 90%). There were 5 late deaths, 1 probably caused by shunt failure. Nine long-term survivors have done well. Follow-up ranges from 1 to 36 months (18 months). Factors influencing conduit function are length, technical considerations, and pulmonary vascular resistance. Late restudy in 5 of 9 survivors confirms patency and demonstrates bidirectional pulmonary blood flow. Since PTFE shunt flow capability is fixed, the infant may require repair or a second shunt within 24 months of the initial procedure.

Mechanical Circulatory Assistance for the Treatment of Complications of Coronary Artery Disease

Surgery has become an accepted method of treatment for coronary artery disease and its complications. Revascularization results in significant improvement in symptoms for patients with angina pectoris. Occasionally, patients requiring surgery for angina pectoris will sustain reversible ischemic damage during operation; such patients can be successfully weaned from cardiopulmonary bypass with full recovery when intra-aortic balloon counterpulsation is used. Arrhythmias associated with ischemic damage to the myocardium also can be controlled when IABCP is used for physiologic assistance. Patients in cardiogenicshock of pulmonary edema after acute myocardial infarction have an ominous prognosis. When decompensation occurs, IABCP may be used to stabilize the patient and to allow study and corrective surgery if possible. The prognosis is better for patients with ventricular septal defect, although selected patients without a mechanical defect of the myocardium can be salvaged if the response to IABCP is favorable. Counterpulsation has also been shown to be useful in achieving pulsatile cardiopulmonary bypass and in assisting high-risk patients through operation. External pressure circulatory assist (EPCA) is less effective than IABCP in assisting the failing myocardium; however, the external device is noninvasive and may be a useful adjunct in situations where IABCP is not feasible.

Leakage of disposable breathing circuits

STUDY OBJECTIVE To determine the sites and rates of the leakage of disposable breathing circuits. DESIGN Nonclinical, experimental study. SETTING Experimental laboratory. INTERVENTIONS To identify in vitro the leakage sites by bubble test and to measure the leakage rate by the increased oxygen (O2) flow needed to maintain the circuit pressure provided by an anesthesia machine previously verified to have no leaks. Breathing circuit pressures measured with a sphygmomanometer of 30, 50, 70, and 100 mmHg were studied. MEASUREMENTS AND MAIN RESULTS Ninety-seven disposable and three reusable breathing circuits from seven manufacturers were investigated for leakage. There was a linear relationship between the circuit pressure and O2 flow at which leaks occurred. No leakage was detected in reusable circuits at 30 mmHg of circuit pressure. Leakage was found in two of the six junctions between the patient adapter and the corrugated tubing in the reusable breathing circuits at a circuit pressure of 100 mmHg. In 90% of the disposable circuits tested, the leakage rate was less than 75 ml/min at 30 mmHg of circuit pressure, but there was a wide variation in the amount of leakage among the circuits of different companies. Almost all the leakage sites were located at connections in the circuit and not in the corrugated tubing. The most common site of leakage in the disposable circuits was the junction between the patient adapter end and the corrugated tubing (57%) rather than the swivel piece (40%). CONCLUSIONS Most disposable breathing circuits can be used safely for closed-circuit anesthesia, as the leakage volume is too small to be of clinical importance. The variation in the leakage rates stresses the importance of quality control of the connector seals.

Cardiovascular Responses to PEEP and CPAP Following Repair of Complicated Congenital Heart Defects

Fourteen infants and children ranging in age from 7 months to 8 years were studied in a hemodynamically stable condition following repair of various heart defects. Changes in cardiac index, stroke index, heart rate, systemic vascular resistance, mean arterial pressure, and central venous pressure were evaluated at levels of 0, 5, and 10 cm H2O using positive end-expiratory pressure (PEEP) in 14 patients and continuous positive airway pressure (CPAP) in 3 patients. No significant changes were found in any of the measurements taken at the different levels.

Avoiding Postoperative Dysrhythmias and Venous Obstruction Following Mustard's Operation: Technical Considerations

Abstract Five infants with uncomplicated transposition of the great arteries underwent correction during which special care was taken to avoid unfavorable hemodynamic and rhythm abnormalities. The late rhythm was sinus in all but 1 patient, who developed atrial flutter three years after operation; the flutter was converted to sinus bradyarrhythmia with dc countershock. Intracardiac electrograms showed normal sinus node function and normal intraatrial conduction despite division of the posterior internodal tracts. Cardiac catheterization done in 3 patients one to three years after operation showed widely patent channels into the systemic venous atria, and contractility studies demonstrated that the right ventricle functioned well as a systemic pump.