Arthur S. Palmer

Recombinant aprotinin in coronary artery bypass graft operations

OBJECTIVE To evaluate the role of recombinant bovine aprotinin in reducing blood loss in coronary artery bypass graft surgery. DESIGN An open-label, randomized, controlled study evaluating two dosage levels of recombinant aprotinin. SETTING Two acute care hospitals (Northwestern Memorial Hospital, Chicago, Ill., and the Scott & White Memorial Hospital, Temple, Texas). PATIENTS Patients undergoing primary and reoperation coronary artery bypass grafting were assigned to groups by means of a computer-generated table of random numbers. Treated (n = 48) and control (n = 36) patients did not differ significantly in age, sex, weight, number of grafts, or preoperative hemoglobin level. INTERVENTIONS Recombinant aprotinin was given at two dosages. Dosage level 1 consisted of a bolus of 2 mg/kg intravenously immediately after the induction of anesthesia, 1 mg/kg added to each liter of the oxygenator prime, and 0.5 mg.kg-1.hr-1 infused continuously during operation. At dosage level 2, doses were doubled. Intraoperative monitoring of anti-factor Xa activity was performed, and additional doses of heparin were given on the basis of anti-factor Xa results. MAIN OUTCOME MEASURES Preoperative and postoperative hemoglobin levels, amounts of autotransfusion device and chest tube drainage blood, and transfusions of allogeneic red blood cells. Adverse clinical events (alterations in renal function, graft thrombosis, myocardial infarction, and death) were recorded. RESULTS Additional heparin was given to 48% patients in the aprotinin group and to 44% of control patients. Overall red blood cell loss (in milliliters, mean +/- standard deviation [SD]) was decreased with aprotinin at dosage level 1 for reoperations (1040 +/- 162 vs 1544 +/- 198, p < 0.01), and at dosage level 2 for all operations (primary operations, 886 +/- 362 vs 1333 +/- 618, p = 0.02; reoperations, 1191 +/- 560 vs 1815 +/- 1116, p = 0.2). Fewer patients in the aprotinin than in the control group had transfusions of donated blood (6/48 vs 12/36, p = 0.02) or reinfusion of chest tube drainage blood (12/48 vs 20/36, p < 0.01). Among patients receiving dosage level 1, there were no myocardial infarctions or deaths. At dosage level 2, one patient had profound bradycardia and died on day 12 and two patients had late graft closures. Two control patients had hypotension after bypass necessitating intraaortic balloon pumps, and one of these patients died. Postoperative increases in blood urea nitrogen and creatinine levels were small in both aprotinin and control groups. No hypersensitivity or other allergic reactions occurred. CONCLUSION We conclude that, at the dosages given, recombinant bovine aprotinin decreases surgical blood loss and transfusion requirements in patients undergoing coronary artery bypass grafting, but its use requires appropriate monitoring of heparin use during bypass. Whether higher dosages of aprotinin increase the risk of graft thrombosis must be further assessed with a larger patient sample.

An Implantable Artificial Lung

Abstract Self-contained artificial lung prototypes were implanted in 8 dogs and a calf for periods up to eight days. Ventilation and perfusion of the artificial organ are provided by pressures available in the pleural cavity and the pulmonary artery through the use of a silicone rubber ventilating envelope and an efficient, low-pressure manifold system. The three units with the largest membrane area (0.208 to 0.832 sq. m. had flow rates of 65 to 240 ml. per minute and oxygen transfer rates of 1.4 to 13.0 cc. per minute with room air ventilation. Design characteristics and the problems with implantation and long-term function are discussed.

Compression Therapy of Limb Edema Using Hydrostatic Pressure of Mercury

A new apparatus for the treatment of edema of the extremities is described. The extremity is placed in a cylindrical vertical tank and isolated by a circum ferential synthetic rubber membrane. The equipment is programmed to create a mold of the extremity using a slurry of plastic granules from a reservoir. Mer cury is then pumped between the mold and the extremity, thereby exerting a pres sure gradient on the extremity equal to the hydrostatic pressure of the mercury column. A computerized program forms the mold and runs several compres sion cycles for each treatment session. Twelve patients were treated (8 upper extremities, 4 lower extremities) on a weekly or semiweekly basis. Progress was followed with computed axial tomog raphy scans, as well as measurements and photographs. Ten patients experienced significant immediate decrease in edema with each treatment. Wrapping or elas tic support was required to prevent the return of edema between treatments. No pain, skin injury, or other complication of treatment was noted. The apparatus can safely provide short-term, immediate, significant improve ment of extremity edema. Further studies will be necessary to determine long- term benefit.

Nuclear scanning with technetium-99m-sestamibi to evaluate ischemia in muscle flaps for cardiomyoplasty

Mobilization of the latissimus dorsi muscle from the chest wall for cardiomyoplasty interrupts part of its blood supply. The time required for adequate collaterals to develop from the thoracodorsal artery is unknown. In four dogs, the latissimus dorsi muscle was mobilized as for cardiomyoplasty and stimulating electrodes were implanted. The muscle was replaced on the chest wall over a sheet of Gore-Tex (W. L. Gore & Associates, Inc. Flagstaff, AZ) membrane to block growth of collateral vessels from the chest wall. The opposite latissimus dorsi muscle served as the control. After a delay of 2 weeks the latissimus dorsi was burst stimulated at a rate of 80 per min with two 100 msec bursts at 85 Hz and 25 Hz for 30 min. Technetium-99m-sestamibi scans were then done to detect ischemia. Serial studies were done during the next several weeks. Images at 4 weeks demonstrated maximum uptake in the mobilized muscle, which did not subsequently improve. The authors conclude that the mobilized latissimus dorsi muscle can be imaged with technetium-99m-sestamibi and evidence of ischemia resolves at 4 weeks. These findings suggest that collateral flow is adequate as early as 4 weeks after mobilization of the latissimus dorsi muscle for cardiomyoplasty.

Gas Tensions in Cardiac Lymph as a Reflection of the Interstitial Space of the Heart

The purpose of this study was to determine the feasibility of measuring partial pressure of oxygen (pO2), partial pressure of carbon dioxide (pCO2), and pH in cardiac lymph and to evaluate the relationship of these parameters to comparable measurements in arterial and coronary sinus blood in the normal heart under various respiratory conditions. In four anesthetized open-chest dogs, the principal cardiac lymphatic as well as the femoral artery and coronary sinus were cannulated. Ventilation was varied by changing oxygen concentration, tidal volume, and respiratory rate. PO2, pCO2, and pH were measured in the cardiac lymph, arterial blood, and coronary sinus blood after each change in venti lation. For pH and pCO2, good correlations were observed between the arterial blood and cardiac lymph, arterial blood and coronary sinus blood, and coronary sinus blood and cardiac lymph. The correlation between the pO2 measured in the arterial blood and the pO2 measured in the cardiac lymph was not as strong, and this may have been related to difficulty achieving a steady state. Gas tensions (pO2, pCO2, and pH) can be measured in cardiac lymph and may provide a window to the interstitial compartment of the heart. This is an additional tool for the laboratory study of ischemia and other forms of heart disease.

Method for removal of the St. Jude valve

A method is presented for removal of the St. Jude Medical valve when it must be replaced with another prosthesis. The sewing ring is transected in the radial direction, freeing the rigid portion of the valve. This is then removed, allowing the remainder of the sewing ring to be excised under direct vision. This method simplifies and increases the safety of this procedure.

Staging in tubular oxygenators — Experimental results

The oxygenation rate of blood flowing through permeable tubes can be increased by mixing or turbulence of the blood. Staging of the tubes has been suggested as one means of enhancing the oxygenation rate. A series of experiments has been performed to investigate the feasibility of staging and the results show a definite advantage in oxygen transfer compared with regular straight tubes.