A multicenter, double-blind, placebo-controlled trial of aprotinin for reducing blood loss and the requirement for donor-blood transfusion in patients undergoing repeat coronary artery bypass grafting

The inflammatory response and extracorporeal circulation

Defining the cause of organ and tissue dysfunction associated with the use of perfusion systems will produce methods of prevention or treatment and improve patient outcome. The problem is the plethora of triggers, effectors, and mediators in this process, which can now be measured. Each new measureable compound becomes another biochemical "smoking gun" without physiological data to show any relevance to the human problem. This review critically compares and contrasts the role of certain, largely novel, initiation, amplification, and cytotoxic mechanisms in the inflammatory response of the myocardium and pulmonary systems after a period of cardiopulmonary bypass. The available evidence strongly points to the process being different for each of these tissue beds. These data suggest that ensuring normal lung and heart functions after surgery will require separate therapeutic strategies.

Ventricular fibrillation resulting from synchronized internal atrial defibrillation in a patient with ventricular preexcitation

This case describes ventricular proarrhythmia as a result of a synchronized internal atrial defibrillation shock in a 29-year-old man with Ebstein's anomaly referred for radiofrequency ablation of a right posterior accessory pathway. During the electrophysiologic study, atrial fibrillation was induced and 3/3 msec shocks of various strengths were delivered between two decapolar defibrillation catheters in the coronary sinus and right atrial appendage. A 2.0-J biphasic shock synchronized to an R wave after a short-long-short ventricular cycle length pattern with a preshock coupling interval of 245 msec induced ventricular fibrillation, which was externally defibrillated with 200 J. This observation has implications for the development of implantable atrial defibrillators.

Acute respiratory distress syndrome after aprotinin infusion

OBJECTIVE

To report a case of acute respiratory distress syndrome (ARDS) following first exposure to aprotinin.

CASE SUMMARY

A 24-year-old previously healthy white man was treated with aprotinin infusion because of bleeding following tonsillectomy. The patient had never been treated with aprotinin before, including local application of different hemostatics containing the aprotinin component. Two hours later, hypotension and severe ARDS developed. A full recovery was noted after discontinuation of the drug and prolonged ventilatory support.

DISCUSSION

To our knowledge, this is the first reported case of ARDS following first administration of aprotinin, although serious adverse effects at first exposure have been reported. We propose two possible mechanisms for this adverse reaction: a nonallergic or anaphylactoid reaction with direct degranulation of mast cells and basophils by aprotinin, and microthrombosis of the small pulmonary arterioles precipitated by aprotinin.

CONCLUSIONS

Most clinicians consider aprotinin to be a safe drug, especially if it has not been administered before. Reexposure carries a high risk of allergic reactions because of possible sensitization. Nonimmunologic, toxic, or idiosyncratic adverse reactions can be expected at first exposure to any drug, as well as to aprotinin.

Cardiopulmonary bypass and the inflammatory response: a role for serine protease inhibitors?

Cardiopulmonary bypass has been shown to activate various inflammatory cascades in the body, resulting in pathophysiological changes that may affect patient outcome after cardiac surgery. Many of these inflammatory cascades are enzyme mediated, involving serine proteases. This report reviews the mechanisms of bypass-mediated activation of the inflammatory cascades and outlines the role of serine protease inhibitors in ameliorating the consequences of the inflammatory response. Experimental data are reviewed on the action of aprotinin in inhibiting the intrinsic coagulation system and in limiting the contact activation of blood platelets and leukocytes. Also reviewed is the role of aprotinin in impacting the incidence of perioperative myocardial ischemia and the central nervous system dysfunction and stroke that are not infrequent complications of surgery with cardiopulmonary bypass.

Autologous vein graft-coated stents for the treatment of thrombus-containing coronary artery lesions

Recent studies have shown that stents may have a potential role in the treatment of thrombus-containing lesions. We report on the application of an autologous vein graft-coated stent (AVGCS) as the primary therapeutic modality for acute myocardial infarction in 10 patients. AVGCS delivery and deployment were successful and uneventful. Mean minimal lumen diameter and TIMI trial flow grade increased significantly (from 0.04 +/- 0.09 mm pre-AVGCS to 3.02 +/- 0.32 mm post-AVGCS, and from 10 patients with flow grade 0-1 pre-AVGCS to 10 patients with flow grade 3 post-AVGCS, respectively). Ten-day angiogram revealed maintenance of the immediate results. Nine patients had a negative exercise stress test 2 mo post-AVGCS, and at a mean follow-up of 30 +/- 7 weeks, all 9 were symptom-free. One patient, 3 wk after implantation and while being hospitalized for hypovolemic shock, developed recurrent infarction. These favorable preliminary outcomes suggest that AVGCS may play a useful role in the treatment of thrombus-containing lesions.

Prevalence of anaphylactic reactions to aprotinin: analysis of two hundred forty-eight reexposures to aprotinin in heart operations

The efficacy of aprotinin to reduce intraoperative bleeding tendency in cardiac operations has been demonstrated in several studies. Aprotinin is a polybasic polypeptide and has antigenic properties. Anaphylactic reactions to aprotinin have been described. The aim of the present study was to evaluate the prevalence of adverse reactions to reexposure to high-dose aprotinin. The clinical outcome of all patients undergoing heart operations in our institution between 1988 and 1995 with at least two exposures to aprotinin was investigated. There were 248 reexposures to aprotinin in 240 patients: 101 adult and 147 pediatric cases. The total aprotinin doses were 4.9 x 10(6) (interquartile range 2 x 10(6)) KIU (adults) and 1.3 x 10(6) (interquartile range 1.2 x 10(6)) KIU (pediatric patients). The time between the first and second aprotinin exposures was 344 (interquartile range 1039) days. Seven adverse reactions to aprotinin were found (2.8%). The severity of the reaction ranged from mild (no intervention) to severe (longer-lasting circulatory depression despite vasopressor therapy). All patients survived the event. Patients with an interval less than 6 months since the previous exposure had a statistically higher incidence of adverse reactions than patients with a longer interval (5/111 or 4.5% vs 2/137 or 1.5%, p < 0.05). Two patients reacted to a test dose of 10,000 KIU aprotinin. Pretreatment with antihistaminics was done in 60% of the patients. We recommend the following procedure for reexposure with high-dose aprotinin: (1) delay of the first bolus injection of aprotinin until the surgeon is ready to begin cardiopulmonary bypass, (2) test dose of 10,000 KIU aprotinin in all patients with aprotinin treatment, (3) H1/H2 blockade in known or possible reexposures, and (4) avoidance of reexposure within the first 6 months after the previous exposure to aprotinin. With these precautions a reexposure to aprotinin in patients with a high risk of bleeding is justified, because the benefits of aprotinin treatment outweigh the relative risk of a serious allergic reaction.

Aprotinin for primary coronary artery bypass grafting: a multicenter trial of three dose regimens

BACKGROUND

High-dose aprotinin reduces transfusion requirements in patients undergoing coronary artery bypass grafting, but the safety and effectiveness of smaller doses is unclear. Furthermore, patient selection criteria for optimal use of the drug are not well defined.

METHODS

Seven hundred and four first-time coronary artery bypass grafting patients were randomized to receive one of three doses of aprotinin (high, low, and pump-prime-only) or placebo. The patients were stratified as to risk of excessive bleeding.

RESULTS

All three aprotinin doses were highly effective in reducing bleeding and transfusion requirements. Consistent efficacy was not, however, demonstrated in the subgroup of patients at low risk for bleeding. There were no differences in mortality or the incidences of renal failure, strokes, or definite myocardial infarctions between the groups, although the pump-prime-only dose was associated with a small increase in definite, probable, or possible myocardial infarctions (p = 0.045).

CONCLUSIONS

Low-dose and pump-prime-only aprotinin regimens provide reductions in bleeding and transfusion requirements that are similar to those of high-dose regimens. Although safe, aprotinin is not routinely indicated for the first-time coronary artery bypass grafting patient who is at low risk for postoperative bleeding. The pump-prime-only dose is not currently recommended because of a possible association with more frequent myocardial infarctions.

The efficacy and cost of aprotinin in children undergoing reoperative open heart surgery

We performed a prospective, randomized, placebo-controlled, double-blind trial to assess the efficacy of aprotinin in 61 children (median age 3.7 yr) undergoing reoperative open heart surgery (OHS). Three demographically similar groups were studied: large-dose aprotinin (ALD), small-dose aprotinin (ASD), and placebo (P). Over the first 24 postoperative hours fewer patients in the aprotinin groups received packed red cells (ALD, 53%; ASD, 89%; and P, 95%; P = 0.001), platelets (ALD, 32%; ASD, 50%; and P, 65%; P = 0.04), and fresh frozen plasma (ALD, 16%; ASD, 17%; and P, 60%; P = 0.003) than placebo patients. Most importantly, aprotinin patients had fewer exposures to banked blood components (ALD, median 1 U; and ASD, median 2 U) than P (median 6 U; P = 0.001), with no difference in overall complication rate. Use of aprotinin was associated with a savings in the patient charges for blood components, operating room time, and duration of hospitalization. In conclusion, aprotinin decreased the number of units of banked blood components used during the first 24 postoperative hours in reoperative pediatric OHS. Aprotinin thus decreases the risks associated with exposure to banked blood components and reduces hospital charges.

Is the automatic atrial defibrillator a promising approach?

Atrial fibrillation is a common arrhythmia, accounting for more consumption of medical resources than any other arrhythmia. The impact of the disease results from the combination of a loss of atrial contraction, and atrial control over cardiac rate. Studies in animals demonstrated the basic feasibility of atrial defibrillation using electrodes passed intravenously. Subsequent studies in patients confirmed that low-energy shocks were effective in converting atrial fibrillation and were safe if delivered synchronous to the R wave in the absence of a short preceding RR interval. Preliminary experience suggests that a small implanted device might provide beneficial therapy for patients with recurring episodes of persistent, drug-refractory, atrial fibrillation.

Adenosine reduces postbypass transfusion requirements in humans after heart surgery

OBJECTIVE

The objective of this study was to determine the effect, if any, of adenosine blood cardioplegia on blood component usage after heart surgery.

SUMMARY BACKGROUND DATA

The most common cause of nonsurgical postcardiopulmonary bypass bleeding is platelet dysfunction. For this reason, pharmacologic agents are under investigation in an effort to reduce the need for transfusion in this setting.

METHODS

A posthoc analysis of blood product usage was performed in data obtained from a Phase I, single center, open label, randomized study performed in 63 patients. The trial was designed to test the safety and tolerance of adenosine when added to blood cardioplegia in increasing doses to enhance myocardial protection. The database provided information regarding the effect of adenosine cardioplegia on venous plasma adenosine concentrations, the amount of platelets, fresh frozen plasma and packed erythrocytes used, and the association between the adenosine dose and postoperative thoracic drainage.

RESULTS

The postoperative thoracic drainage at 6 hours, 24 hours, and at the time of chest tube removal in the high-dose adenosine cardioplegia group was 68%, 76%, and 75% of the placebo and low-dose adenosine cardioplegia group (p < 0.05). The highest dose of adenosine studied increased baseline adenosine venous plasma levels 360-fold, from 0.17 +/- 0.09 mumol/L to 42.30 +/- 11.20 mumol/L (p < 0.05). This marked increase was associated with a 68%, 56%, and 58% reduction in platelet, fresh frozen plasma, and packed erythrocyte usage, respectively (p < 0.05).

CONCLUSIONS

In addition to enhancing the heart's tolerance to ischemia, adenosine-supplemented cardioplegic solution also may reduce bleeding after cardiopulmonary bypass.

Aprotinin prolongs activated and nonactivated whole blood clotting time and potentiates the effect of heparin in vitro

This study was designed to evaluate the effect of aprotinin on activated versus nonactivated whole blood clotting time using two different on-site methods and to quantify these anticoagulant properties when compared to heparin in a controlled, in vitro environment. Blood specimens were obtained prior to heparin administration from 56 patients undergoing cardiac surgery. Specimens obtained from the first consecutive 20 patients were mixed with either normal saline (NS) or aprotinin (400 kallikrein inhibiting units (KIU)/mL), inserted into Hemochron tubes containing either NS or heparin (0.3 or 0.6 U/mL) and then used to measure celite-activated (celite ACT) and nonactivated whole blood clotting time (WBCT1) using four Hemochron instruments. Accordingly, specimens obtained from the second consecutive 20 patients were mixed with either NS or aprotinin, inserted into Automated Clot Timer cartridges containing either NS or heparin (0.06, 0.13, or 0.25 U/mL) and then used to measure kaolin-activated (kaolin ACT) or nonactivated whole blood clotting times (WBCT2) using four Automated Clot Timer instruments. Specimens obtained from the last 16 patients were mixed with either incrementally larger doses of aprotinin (0, 100, 200, 300, or 400 KIU/mL) or heparin (0, 0.12, 0.24, 0.36, 0.48, or 0.72 U/mL) and were then used for measurement of whole blood clotting time (WBCT2) using six Automated Clot Timer instruments. Aprotinin significantly prolonged activated or nonactivated whole blood clotting time and potentiated the prolongation of whole blood clotting time by heparin. The linear relationship between whole blood clotting time and either heparin concentration (WBCT2 = H x 357 + 280, mean adjusted r2 = 0.88) or aprotinin concentration (WBCT2 = A x 0.97 + 300, mean adjusted r2 = 0.94) was variable among patients. On average, 200 KIU/mL of aprotinin prolonged WBCT2 to the same extent as 0.69 +/- 0.28 U/mL of heparin using linear regression models within each patient. Aprotinin significantly prolongs activated or nonactivated whole blood clotting time measurements in a dose-dependent manner. Since prolongation of whole blood clotting time by heparin is potentiated by aprotinin in vitro, aprotinin's anticoagulant properties may in part account for the prolonged celite activated clotting time values observed in the presence of aprotinin.