Los Angeles Ballroom

19. Traumatic Aortic Rupture: A Five Year Experience

STEPHEN Z. TURNEY, SAFUH ATTAR, ROBERT AYELLA*,

R. ADAMS COWLEY and JOSEPH McLAUGHLIN, Baltimore, Maryland

In the five year period ending October 1975, 31 consecutive patients with traumatic rupture of the thoracic aorta underwent surgery at the University of Maryland Hospital or the Maryland Institute for Emergency Medicine. All cases were confirmed by preoperative aortogram. Rupture was confined to one or more sites in the descending thoracic aorta at or distal to the origin of the left subclavian artery. The age range was 15 to 67 years with a mean of 26 years. Operation was done within an average of 18 hours of injury. Significant non-thoracic injuries were present in every case. Six patients with positive peritoneal lavage underwent exploratory laparotomy prior to thoracotomy because of shock.

Surgical repair was done using left heart bypass in 2 cases (1 death), a passive aorto-aorto shunt in 23 cases (5 deaths) and without shunt or bypass in 6 cases (no deaths). An end-to-end tubular dacron graft was used to reconstruct the aorta in all but one patient.

Overall survival rate was 25 of 31 patients (81%). Paraplegia developed in one patient in the aorto-aorto shunt group. Renal failure developed in three patients (2 deaths, v.i.), all in the aorto-aorto shunt group and all with a prolonged period of preoperative hypotension. Hypertension was present preoperatively and lingered for several days postoperatively in 18 (72%) of the survivors. Left recurrent laryngeal nerve palsy persisted in 8 (32%) of the survivors. Two of the deaths were related to technical problems of the shunting procedure and two to intra-pleural exsanguination before proximal aortic control could be achieved. Two other deaths occurred 3 days postoperatively from associated cerebral trauma and renal failure.

This series lends support to the rigorous aortographic search for ruptured thoracic aortas in trauma patients with widened mediastinum since good overall survival can be achieved even in the face of multiple trauma. Once experience has been gained using shunting techniques, repair of descending thoracic aortic tears may be safely carried out without shunt if done expeditiously.

*By invitation

20. The Contribution of Anticoagulants to Platelet Dysfunction with Extracorporeal Circulation

HERBERT W. WALLACE, HELENE BROOKS*, THOMAS P. STEIN*

and NANCY J. ZIMMERMAN*, Philadelphia, Pennsylvania

The problem of platelet dysfunction and loss during and following extra-corporeal circulation remains an enigma. The results of this investigation which evaluates the effects of anticoagulants on platelet function causes concern about those studies of platelet function performed directly on patients undergoing extracorporeal circulation. Fresh human blood from 40 non-medicated volunteers was anticoagulated with 4.3 units/ml heparin and/or ACD (1:9). Retention of platelets from whole blood on glass beads was performed by the method of Bowie. Platelet retention of heparinized blood, as expected, averaged 88.1 ± SE 1.5%. However, ACD platelets averaged only 24.6 ± SE 2.8%. Platelet retention with CPD and EDTA yielded similar low values (26.0 ± 3.9% and 19.1 ± 7.5% respectively). The addition of ACD to heparinized blood also decreased platelet retention (19.7 ± 3.1%). The addition of heparin to ACD or CPD blood did not alter the original decreased retention. Calcium added (even in excess) to blood containing heparin and ACD did not reverse the depressed retention (29.3 ± 4.6%). The substitution of CPD gave similar results. Utilizing mixtures of separately collected ACD blood and heparinized blood, depression of platelet retention was directly proportional to the amount of ACD blood present. Altering the pH of the ACD blood did not affect its depressed retention of platelets. Neutralizing heparinized blood 50% with protamine or polybrene also significantly depressed platelet retention (51 ± 1.3% and 35.5 ± 4%). Neither protamine nor polybrene had any effect upon ACD blood. These data indicate that anticoagulants may play a significant role in the depressed platelet function observed during and following extracorporeal circulation. The presence of adequate numbers of platelets in the circulation does not assure that their function is physiologically normal. Platelets exposed to anticoagulants and other agents during ECC do not provide the ideal model for the study of platelet dysfunction.

*By invitation

21. Effects of Pulsatile and Nonpulsatile Coronary Perfu-sion on Canine Left Ventricular Performance

SALEM M. HABAL*, MELVIN B. WEISS*, HENRY M. SPOTNITZ*,

EDUARDO N. PARODI*, MARIANNE WOLFF*, PAUL J. CANNON*,

BRIAN F. HOFFMAN* and JAMES R. MALM, New York, New York

The effects of pulsatile (P) versus nonpulsatile (NP) coronary perfusion (CP) on myocardial protection were studied during normothermic cardiopulmonary bypass. NP perfusion was done in 7 dogs with beating hearts (BH), Group A, and in 7 during spontaneous ventricular fibrillation (Fib), Group B. P perfusion was done in 8 other animals with Fib, Group C. Two additional dogs in each group were used for histological studies. For 120 minutes CP was regulated at a mean pressure of 100 mmHg for NP and 80 mmHg for P (110/40 phasic). Before and after CP a 25 ml intraventricular balloon was used to measure isovolumic pressure, peak dp/dt and compliance (DV/DP). Regional myocardial blood flow (MBF) was measured using 8-10u radioactive microspheres. Total coronary blood flow, myocardial oxygen consumption (MVO₂) and lactate extraction were measured at 30 minute intervals.

Results were compared by analysis of variance. After 120 minutes of CP, Group B (NP/Fib) when compared to Group A (NP/BH) showed no significant change in peak dp/dt, a 50% decrease in compliance (3.3 to 1.6 ml/mmHg, p<0.01), a greater MVO₂ (3.6 ± 2.8 vs o.83 ± .64 ml/min/100g, p<0.05) and a decrease in lactate extraction (1.9 ± 2.8 vs 5.2 ± 3.3%, p< 0.05). Total L.V. MBF was not different in the two groups, but the endocardial/epicardial flow ratio was lower in Group B (1.06 ±.16 vs 1.37 ± .37 ml/min/g, p < 0.05). Histological study of Group B demonstrates subendocardial ischemic changes and focal hemorrhage, whereas Group A showed midmyocardial linear condensation of sarcoplasm.

In Group C (P/Fib) after 120 minutes, peak dp/dt actually increased (2274 ± 889 to 3086 ± 1023 mmHg/sec at 25ml, p < 0.01) where as compliance remained unchanged with time (2.6 to 2.4ml/mmHg). Although total L. V. MBF was reduced (1.03 ± .23 ml/min/g, p<0.01), MVO₂ was not significantly different from Group B, because of a 70% increase in oxygen extraction, p < 0.05. Lactate extraction was also increased (9.28 ± 3.7%, p < 0.01) above Group B and the LV endocardial/epicardial flow ratio was greater in Group C (1.21 ± .23, p < 0.05). Histological study demonstrated limited patchy midmyocardial condensation of sarcoplasm but no evidence of subendocardial ischemia.

The results demonstrate the superiority of pulsatile CP in preserving ventricular performance during prolonged ventricular fibrillation. The increased MVO₂ of ventricular fibrillation is associated, during pulsatile CP, with increased myocardial O2 extraction and lower total MBF prevening subendocardial ischemia and hemorrhage.

*By invitation

22. Clinical and Hemodynamic Criteria for Use of Intra-Aortic Balloon Pump (IABP) in Cardiac Surgery Patients

HOOSHANG BOLOOKI, RICHARD J. THURER*, ABELARDO VARGAS*,

WILLIS H. WILLIAMS*, GERARD A. KAISER, FRANK MACK*,

ALI GHAHRAMANI* and ADRIANE FRIED*, Miami, Florida

Application of IABP for heart failure in cardiac surgical patients (pts) has been the subject of recent controversy. In order to establish criteria for use of this modality a retrospective study of 42 pts who required IABP because of inability to be weaned from cardiopulmonary bypass was done. Patients in cardiogenic shock pre-operatively were excluded. The 42 pts included 23 (Group A) who had severe preoperative (preop) left ventricular (LV) dysfunction with cardiac index (CI) < 1.8 L min/m², ejection fraction (EF) < 30%, end-diastolic pressure (EdP) > 25mmHg and 19 (Group B) who had a combination of moderate cardiac dysfunction (CI < 2.2, EF < 40, EdP > 18} in the presence of severe LV hypertrophy, acute infarction, severe aortic stenosis (gradient > 85mmHg) with or without coronary disease. There was an inverse relation between survival and delay from completion of operation to the use of IABP. 32 of 42 pts were weaned off bypass and were balloon assisted for 24-96 hours postop; 22 pts were discharged (52%). In Group A 14 of 23 (60%) and in Group B 8 of 19 (36%) survived. Based on these findings during 74-'75, 22 pts were operated with elective use of IABP along with serial hemodynamic studies. 12 had preoperative severe LV dysfunction similar to Group A arid 10 had moderate dysfunction in combination with pathology similar to Group B. Fifteen of these pts were hemodynam-ically unstable at the time of arrival to operating room and received IABP under local anesthesia. Twenty pts (90%) received IABP for 12-36 hours postop and were hospital survivors. In Group A (12 of 12) and in Group B 8 of 10 were among survivors. Criteria for use of IABP in cardiac surgery should include severe preop LV dysfunction and the combination of moderate dysfunction with LV hypertrophy, coronary and valvular pathology.

3:30 P.M. Executive Session (Limited to Active and Senior Members)

Los Angeles Ballroom

*By invitation

SATURDAY EVENING, APRIL 24, 1976

7:00 P.M. President's Reception

Beverly Hills Ballroom

8:00 P.M. President's Dinner and Dance

Beverly Hills Ballroom

Attendance open to all physicians and their ladies. Tickets must be purchased at the registration desk by 5:00 P.M. on Friday, April 23. Dinner dress preferred.