Management options for aorto-oesophageal fistula: case histories and review of the literature.

OBJECTIVE: An aorto-oesophageal fistula is a rare clinical entity, leading to life-threatening gastrointestinal bleeding. Thoracic aortic aneurysms are the most common cause of aorto-oesophageal fistulae; further causes involve foreign body ingestion, trauma (in most cases iatrogenic), carcinoma or, very rarely, aortitis tuberculotica. METHODS: Due to its rarity, there are no large multicentre studies present to evaluate the efficacy of different therapeutic management options. Since it is associated with significant morbidity and mortality, we give a short summary of various treatment approaches performed in our clinical practice in the past three years. The most straightforward therapeutic option may be an endovascular aortic repair and subtotal oesophageal resection followed by gastro-oesophageal reconstruction, but other alternative treatment possibilities are also present, although with probable higher morbidity. CONCLUSIONS: Eliminating the source of bleeding as an emergency, resecting the oesophagus urgently to prevent sepsis and reconstructing the gastrointestinal continuity as an elective case after having the inflammatory processes settled seems to justify the endovascular aortic repair and subtotal oesophageal resection, followed by a gastro-oesophageal reconstruction, as an effective surgical approach.

Unoperated severe aortic stenosis: decision making in an adult UK-based population.

INTRODUCTION: Severe symptomatic aortic stenosis is associated with a poor prognosis, with most patients dying 2-3 years after diagnosis. We analysed the proportion of patients with severe aortic stenosis not referred for aortic valve replacement (AVR) in a UK-based population and the clinical factors contributing to this. METHODS: Retrospective analysis of patients with echocardiographic evidence of severe aortic stenosis was performed at a university teaching hospital. RESULTS: A total of 178 consecutive patients with severe aortic stenosis (AVA: <1 cm(2), mean pressure gradient: ≥40 mmHg, or visually severe on echocardiography) were included in the study. Eighty-three patients did not have AVR (95% confidence interval: 39-54%). The cohort included 146 symptomatic patients (82%) and 32 (18%) who were asymptomatic. The most common reason for non-referral in symptomatic patients was 'high operative risk' and in asymptomatic patients 'no symptoms'. Of the patients who did not have AVR, only 19% (n=16) were referred for a surgical opinion. None of the patients in the asymptomatic group underwent echocardiographic stress imaging. The thirty-day operative mortality rate in the AVR group was 2.3%. Symptomatic patients who underwent AVR had superior survival, even after adjusting for co-morbidities (p<0.001). CONCLUSIONS: A considerable proportion of patients with severe aortic stenosis are not referred for surgery although they have a clear indication for AVR. Patients are often estimated as being too high risk or having prohibitive co-morbidities. Among asymptomatic patients, stress imaging was rarely used despite its useful role prognostically and in deciding the best time for intervention.

Mitral valve reconstruction in the presence of infection.

Reconstruction of the mitral valve offers an alternative to replacement in the treatment of active infective endocarditis, with long term benefits for the patient.

Aortic root replacement in patients with Marfan's syndrome: the Southampton experience.

BACKGROUND: The purpose of this study was to evaluate the early and late clinical outcome after aortic root replacement (ARR) in patients with Marfan's syndrome. METHODS: A total of 65 consecutive patients with Marfan's syndrome (mean age 41.7 +/- 10.7 years, range 15 to 76 years) undergoing ARR between 1972 and 1998 in Southampton were studied. Of the patients, 45 had a chronic aneurysm of the ascending aorta and 20 had a type A dissection (16 acute and 4 chronic). The operations were elective in 38 and nonelective in 27 cases (emergency in 22 and urgent in 5). Mean size of the ascending aorta was 6.3 +/- 1.4 cm (3.8 to 12 cm). A Bentall procedure was performed in 62 and a homograft root replacement in 3 patients. Mean follow-up was 8 +/- 4.1 years (0 to 22.9 years). RESULTS: Operative mortality was 6.1% (4 deaths) (for the elective vs nonelective procedures it was 2.6% vs 11%, p = 0.2). The 10-year freedom from thromboembolism, hemorrhage, and endocarditis was 88%, 89.8%, and 98.4% (0.9%, 0.9%, and 0.2% per patient-year) and from late aortic events it was 86.3% (1.3% per patient-year). Aortic root replacement for dissection was an independent predictor of occurrence of late aortic events (p = 0.01). Five patients had a reoperation with one early death. The 10-year freedom from reoperation was 89.2% (1.1% per patient year) (for elective and nonelective procedures, 90.8% vs 84.6%, p = 0.6). The 10-year survival, including operative mortality, was 72.7% (for elective and nonelective procedures, 78% vs 66.5%, p = 0.6). Late aortic events was an independent adverse predictor of survival (p = 0.02). CONCLUSIONS: In patients with Marfan's syndrome, elective ARR, usually for chronic aneurysm, is associated with a low mortality, low rate of aortic complications, and good late survival. Nonelective ARR, mostly for dissection, has a greater operative risk and a significantly higher incidence of late catastrophic aortic events. Early prophylactic surgery in these patients is therefore recommended. Long-term clinical and radiologic follow-up to prevent or to treat late aortic events is highly desirable.

Autotransfusion decreases blood usage following cardiac surgery -- a prospective randomized trial.

INTRODUCTION: 10% of blood issued by the National Blood Service (220,000) is utilised in cardiac procedures. Transfusion reactions, infection risk and cost should stimulate us to decrease this transfusion rate. We tested the efficacy of autotransfusion of washed postoperative mediastinal fluid in a prospective randomized trial. PATIENTS AND METHODS: 166 patients undergoing coronary artery bypass grafting (CABG), valve or CABG + valve procedures were randomized into three groups. The indication for transfusion was a postoperative haemoglobin (Hb) < 10 g/l or a packed cell volume (PCV) < 30. When applicable, group A patients received washed post-operative drainage fluid. Group B all received blood processed from the cardiopulmonary bypass (CPB) circuit following separation from CPB and if appropriate washed post-operative drainage fluid. Group C were controls. Groups were compared using analysis of variance. RESULTS: There was no significant difference in age, sex, type of operation, CPB time and preoperative Hb and PCV between the groups. Blood requirements were as shown. [table - see text] Twelve patients in group A and 10 in group B did not require a homologous transfusion following processing of the mediastinal drainage fluid. CONCLUSION: Autotransfusion of washed postoperative mediastinal fluid can decrease the amount of homologous blood transfused following cardiac surgery. There was no demonstrable benefit in processing blood from the CPB circuit as well as mediastinal drainage fluid.

Sex differences in investigation results and treatment in subjects referred for investigation of chest pain.

OBJECTIVE: To evaluate differences in investigation results and treatment between men and women referred for diagnostic treadmill exercise testing and coronary arteriography. DESIGN: Cohort study. SETTING: Tertiary cardiology centre. SUBJECTS: 1522 subjects referred by primary care physicians to an open access chest pain clinic for initial investigation of chest pain, of whom 485 were subsequently referred for coronary arteriography; and a similar cohort of 107 subjects referred directly by secondary care physicians for diagnostic coronary arteriography. MAIN OUTCOME MEASURES: Rates of positive exercise tests and rates for referral for arteriography and revascularisation according to sex. RESULTS: Overall, women were less likely to be referred for arteriography and revascularisation than men. However, men were more likely to have positive exercise tests, and for various exercise test diagnostic end points men were also more likely to have significant coronary artery disease. After taking this into account, there was no sex difference in referral rates for arteriography or revascularisation. CONCLUSIONS: There was no evidence of a sex bias resulting in inappropriate underinvestigation or undertreatment of women. However, the positive predictive value of treadmill exercise testing is low for women and further research is needed into how best to investigate women with chest pain.

Aortic valve replacement for endocarditis: determinants of early and late outcome.

BACKGROUND AND AIM OF THE STUDY: The study aim was to determine risk factors for operative mortality, recurrent infection, reoperation and long-term survival following aortic valve replacement (AVR) for infective endocarditis. METHODS: Between 1973 and 1997, 109 patients (91 male, 18 female, mean age 52.6 years) underwent isolated AVR for infective endocarditis in our unit. Native valve endocarditis was present in 89 (81.6%) and prosthetic valve endocarditis in 20 (18.4%). Active culture-positive endocarditis was present in 53 (48.6%). Preoperatively, 99 patients (90.8%) were in NYHA classes III and IV. Indications for surgery included cardiac failure in 41 patients, valvular dysfunction in 38, vegetations in 18, sepsis in seven, abscess in six and embolism in four. Mechanical valves were implanted in 69 patients (63.3%) and bioprostheses in 40 (36.7%), including a homograft in 19 (17.4%). Follow up was complete (mean 5.8 years; range: 0-23.8 years; total 633.5 patient-years). RESULTS: The operative mortality was 10.1% (11 deaths). At ten years, freedom from recurrent infection was 94.2%, and freedom from reoperation 83.6%. Biological valve and younger age were significant adverse parameters for freedom from reoperation (p = 0.01 and p = 0.01). There have been 21 late deaths, 15 due to cardiac causes. Kaplan-Meier survival, including operative mortality, at five and ten years was 77.4% and 68.0%, respectively. On Cox proportional hazards regression, Staphylococcus aureus infection (p = 0.008) and older age (p = 0.04) were independent adverse predictors of survival. CONCLUSION: AVR for endocarditis carries a relatively high operative mortality, but can result in a satisfactory freedom from recurrent infection, reoperation and long-term survival. Analysis of our series demonstrates that implantation of a biological valve limits the freedom from reoperation and that infection by Staph. aureus reduces the probability of long-term survival.

Surgery for active culture-positive endocarditis: determinants of early and late outcome.

BACKGROUND: The purpose of this study was to describe a single unit experience in the surgical treatment of active culture-positive endocarditis and identify determinants of early and late outcome. PATIENTS AND METHODS: One hundred eighteen consecutive patients with positive blood culture up to 3 weeks before operation (or positive valve culture) and macroscopic evidence of lesions typical for endocarditis, undergoing operation between January 1973 and December 1996 in Southampton, were evaluated. The aortic valve was infected in 53 (48.9%), the mitral in 46 (39%), both aortic and mitral in 12 (10.1%), the tricuspid in 4 (3.9%), and the pulmonary valve in 3 (2.5%). Native valve endocarditis was present in 83 (70.3%) and prosthetic valve endocarditis in 35 (29.7%). Streptococci and staphylococci were the most common pathogens. Mean follow-up was 5.6 years (range, 0 to 25 years). RESULTS: Operative mortality was 7.6% (9 patients). Endocarditis recurred in 8 (6.7%). A reoperation was required in 12 (10.2%). There was 24 late deaths, 17 of them cardiac. Actuarial freedom from recurrent endocarditis, reoperation, late cardiac death, and long-term survival at 10 years were 85.9%, 87.2%, 85.2%, and 73.1%, respectively. On multiple regression analysis the following were independent adverse predictors: pulmonary edema (p = 0.007) and impaired left ventricular function (p = 0.02) for operative mortality; prosthetic valve endocarditis (p = 0.01) for recurrent infection; myocardial invasion by the infection (p = 0.01) and reoperation (p = 0.04) for late cardiac death; and coagulase-negative staphylococcus (p = 0.02), annular abscess (p = 0.02), and longer intensive care unit stay (p = 0.02) for long-term survival. CONCLUSIONS: Operation for active culture-positive endocarditis carries an acceptable mortality. Freedom from recurrent infection, reoperation, and long-term survival are satisfactory. In our data, patients' hemodynamic status at operation was the major determinant of operative mortality. Prosthetic valve endocarditis, coagulase-negative staphylococcus, and annular or myocardial infectious invasion were the critical adverse determinants of late outcome.

Surgical treatment of infective mitral valve endocarditis: predictors of early and late outcome.

BACKGROUND AND AIMS OF THE STUDY: The study aim was to review our experience in surgical treatment of infective mitral valve endocarditis, and to identify predictors of early and late outcome. METHODS: Ninety-one consecutive patients (52 males, 39 females, mean age 55.6 years) underwent surgery between 1973 and 1997 for endocarditis of isolated mitral (n = 65, 71%), mitral and aortic (n = 25, 28%) and mitral, aortic and tricuspid valves (n = 1, 1%). Native valve endocarditis (NVE) was present in 60 patients (66%) and prosthetic valve endocarditis (PVE) in 31 (34%). The main indications for surgery were heart failure in 32 patients, valve dysfunction in 23, vegetations in 21, and persistent sepsis in 11. Eighty-six patients (95%) were in NYHA classes III-IV, and 58 (64%) had active culture-positive endocarditis at surgery. Mechanical valves were implanted in 73 patients and bioprosthetic valves in 13; valves were repaired in five patients. The impact of 46 parameters on early and late outcome was defined by means of univariate and multivariate statistical analysis. Follow up was complete (mean 5.5 years; range: 0-23.1 years; total 507.3 patient-years). RESULTS: Operative mortality rate was 11% (n = 10). Recurrent infection was recorded in five patients (6%), and reoperation was required in eight (9%). Freedom from recurrent infection and reoperation at 10 years was 89.1% and 87.8% respectively. There were 22 late deaths, 15 from cardiac causes. Actuarial survival rates for all patients at 5, 10 and 15 years were 73.0%, 62.7% and 58.7% (for hospital survivors, the corresponding rates were 81.9%, 69.7% and 66.0%). On multiple logistic regression and Cox proportional hazards models, the following were independent predictors: preoperative pulmonary edema (p = 0.01) for operative mortality; PVE (p = 0.02) for recurrence; younger age (p = 0.02) and PVE (p = 0.02) for reoperation; male gender (p = 0.004) and longer ITU stay for survival (if all patients were included); male gender (p = 0.01) and myocardial invasion by infection (p = 0.02) for survival (if only the hospital survivors were analyzed). CONCLUSION: Surgery for infective mitral valve endocarditis carries a relatively high, though acceptable, risk but provides satisfactory freedom from recurrent infection, reoperation and improved long-term survival. Analysis of these data demonstrated that the preoperative hemodynamic status was the major predictor of in-hospital outcome, PVE increased the risk for recurrent infection and reoperation, whereas male gender and myocardial invasion by the infective process critically reduced the probability of long-term survival. The type of offending pathogen, the activity of infection and the involvement of more than one valve did not appear to influence early and/or late outcome.

Mid-term results with 1,503 CarboMedics mechanical valve implants.

BACKGROUND AND AIM OF THE STUDY: The CarboMedics bileaflet prosthetic heart valve was introduced in 1986, and first implanted by the authors in March 1991. The aim of this study was to analyze the authors' clinical experience with this valve. METHODS: Between March 1991 and October 1998, 1,503 valves were implanted in 1,350 patients (758 males, 592 female; mean age 62 +/- 13 years). Follow up was 99% complete and totaled 4,342 patient-years (pt-yr). RESULTS: The hospital mortality rate was 4.3% (59/1,350). Preoperative NYHA class (p = 0.012), emergency surgery (p = 0.03) and cardiopulmonary bypass time (p = 0.01) were significantly associated with increased risk of operative death (multiple logistic regression). Mean (+/- SEM) survival rates at one and five years were 92.0 +/- 0.7% (n = 1,109) and 80.0 +/- 1.3% (n = 335). Freedom from valve-related complications (linearized rate 5.6%/pt-yr) at one and five years was 89.5 +/- 0.8% (n = 1,031) and 76.3 +/- 1.4% (n = 284). Linearized rates for bleeding events were 2.19%/pt-yr, thromboembolic events 2%/pt-yr, operated valvular endocarditis 0.18%/pt-yr, valve thrombosis 0.14%/pt-yr and non-structural dysfunction 1.22%/pt-yr. Freedom from reoperation at one and five years was 98.5 +/- 0.3% (n = 1,107) and 97.3 +/- 0.5% (n = 334). CONCLUSION: Mid-term results demonstrate that the CarboMedics prosthetic heart valve exhibits a low incidence of valve-related complications.

A single-center experience with 1,378 CarboMedics mechanical valve implants.

BACKGROUND: The CarboMedics bileaflet prosthetic heart valve was introduced in 1986. We first implanted it in March 1991. The purpose of this study was to analyze our clinical experience with this valve. METHODS: Between March 1991 and December 1997, 1,378 valves were implanted in 1,247 patients, 705 men (56.5%) and 542 (43.5%) women with a mean age of 62 +/- 11.9 years (+/- the standard deviation). Follow-up is 99% complete and totals 3,978 patient-years. RESULTS: The early mortality rate was 4.4% (55/1,247). The survival rates at 1 year and 5 years were 91.8% +/- 0.8% (+/- the standard error of mean) (n = 1,062) and 79.2% +/- 1.4% (n = 281), respectively. Freedom from valve-related complications (linearized rate, 4.9% per patient-year) at 1 year and 5 years was 90.6% +/- 0.8% (+/- the standard error of the mean) (n = 996) and 80.6% +/- 1.4% (n = 243), respectively. Linearized rates for various complications were as follows: bleeding events, 1.73% per patient-year; embolic events, 1.76% per patient-year; operated valvular endocarditis, 0.18% per patient-year; valve thrombosis, 0.10% per patient year; and nonstructural dysfunction, 1.21% per patient-year. Freedom from reoperation at 1 year and 5 years was 98.6% +/- 0.3% (+/- the standard error of the mean) (n = 1,070) and 97.7% +/- 0.5% (n = 285), respectively. CONCLUSIONS: Midterm results demonstrate that the CarboMedics prosthetic heart valve exhibits a low incidence of valve-related complications.

Red blood cell stabilization reduces the effect of cell density on recovery following cryopreservation.

The relationship between red blood cell hematocrit and hemolysis during cryopreservation has been examined. Cells were frozen with glycerol, thawed, and deglycerolized in a model system based on the protocols used in transfusion medicine. Analysis included determination of hemolysis following thaw (Thaw) and deglycerolization (Overall) and osmotic fragility of the final cell suspensions. Results demonstrate that thaw hemolysis decreased with increasing hematocrit at all glycerol levels tested. Overall hemolysis increased with increasing hematocrit at low (15% w/v) glycerol and decreased with increasing hematocrit at high (40% w/v) glycerol levels. These results were paralleled by changes in the fragility index. Furthermore, these results indicate a distinction between freeze/thaw lysis and damage which leads to lysis during postthaw processing. To examine this further, a biochemical stabilizing solution, having no cryoprotective effects itself, was added to suboptimal glycerol concentrations. This addition resulted in hemolysis levels and fragility indices comparable to those using high (40% w/v) glycerol levels. Thus, the damage observed with increasing hematocrit is not necessarily a function of the packing on the volume of the ice-free zone, but rather an expression of cell damage. Furthermore, this damage is, in part, biochemical in nature and may be protected against through specific cellular stabilization prior to cryopreservation.

Replacement of the proximal aorta and aortic valve using a composite bileaflet prosthesis and gelatin-impregnated polyester graft (Carbo-Seal): early results in 143 patients.

OBJECTIVE: We report the combined early results from two centers in the United Kingdom using a composite conduit consisting of a bileaflet mechanical valve incorporated into a gelatin-impregnated, ultra-low porosity, woven polyester graft (Carbo-Seal; Sulzer Carbomedics, Inc, Austin, Tex). METHODS: Between August 1992 and March 1997, 143 patients underwent aortic root replacement with the Carbo-Seal composite prosthesis. The indication for surgery was acute type A dissection in 31 (22%), chronic type A dissection in 9 (6%), ascending aortic aneurysm without dissection in 100 (70%), and false aneurysm of the ascending aorta in 3 (2%). Twenty-seven patients (19%) had undergone previous sternotomy, and 40 (28%) were seen as emergencies. Concomitant procedures were performed in 38 (27%), including 18 aortic arch or hemiarch replacements. Total follow-up is 270 patient-years. Follow-up is 100% complete. RESULTS: The early (30-day) mortality was 7% (10 patients). Permanent neurologic events occurred in 2%. At a mean follow-up of 23 months, 94% of survivors were in New York Heart Association functional class I. Freedom from reoperation was 97.2% +/- 1.6% (1 standard error [1 SE]) at 12 months and 95.7% +/- 2.2% at 48 months. Including early mortality, survival was 90.1% +/- 2.6% at 12 months and 83.1% +/- 3. 5% at 48 months. CONCLUSIONS: Aortic root replacement with use of the Carbo-Seal prosthesis can be undertaken with a relatively low early mortality and morbidity. A low reoperation rate and high intermediate-term survival can be expected, but continued follow-up is needed to determine the long-term efficacy of this prosthesis.

Rest and exercise Doppler hemodynamics of the Medtronic Intact aortic bioprosthesis.

BACKGROUND AND AIMS OF THE STUDY: Exercise treadmill testing was used to evaluate the functional rest and stress hemodynamic profile of the Medtronic Intact aortic bioprosthesis. METHODS: A group of 93 patients (mean age at operation 72.9 years; range: 61-79 years) was studied. Mean time to follow up was 20.8 months. The preoperative diagnosis was aortic stenosis (AS; n = 66), aortic regurgitation (AR; n = 19) or AS/AR (n = 8). Left ventricular function was assessed as normal (n = 78), moderate (n = 14) or poor (n = 1). Patients received a range of valve sizes: 21 mm (n = 7); 23 mm (n = 41); 25 mm (n = 32); 27 mm (n = 7); and 29 mm (n = 6). RESULTS: For all valve sizes, Doppler-derived hemodynamics at rest and peak exercise, respectively were: mean aortic valve gradient (AVG) 13.2 +/- 5.2 mmHg and 22.2 +/- 8.9 mmHg; peak aortic valve gradient (AVG) 24.3 +/- 9.6 mmHg and 39.1 +/- 13.5 mmHg; effective orifice area (EOA) 1.39 +/- 0.49 cm2 and 1.38 +/- 0.5 cm2; and effective orifice area index (EOAI) 0.76 +/- 0.26 cm2/m2 and 0.75 +/- 0.26 cm2/m2. Mean and peak AVG decreased as valve sizes increased, while both EOA and EOAI increased as valve sizes increased. CONCLUSIONS: The Medtronic Intact aortic bioprosthesis provides good hemodynamics both at rest and exercise, across the range of implanted valve sizes.

Autotransfusion of washed shed mediastinal fluid decreases the requirement for autologous blood transfusion following cardiac surgery: a prospective randomized trial.

OBJECTIVES: The National Blood Service issues 2.2 million units of blood per year, 10% of these (220000) are utilized in cardiac procedures. Transfusion reactions, infection risk and cost should stimulate us to decrease this transfusion rate. We test the efficacy of autotransfusion following surgery in a prospective randomized trial. METHODS: One hundred and twelve patients undergoing CABG, valve or CABG + valve procedures were randomized into two groups. Group A received washed postoperative drainage fluid and group C were controls. The indication for transfusion was a postoperative haemoglobin (Hb) < 10 g/l or a PCV < 30. There was no significant difference in preoperative and operative variables between the groups. RESULTS: Twenty-eight patients in group A and 46 in group C required homologous transfusion (P = 0.0008). Group A patients required 298+/-49 ml of banked blood per patient, group C 508+/-49 ml (P = 0.003). There was no difference in total blood required (volume autotransfused + volume banked blood transfused) between the groups (group A 404+/-50 ml, group C 508+/-50 ml) or in mean total mediastinal fluid drainage (group A 652+/-51 ml, group C 686+/-50ml). The mean Hb concentration was significantly higher in group A on day 1 (11.2 g/dl+/-51 vs. 10.6 g/dl+/-13 (P = 0.002)). No morbidity was associated with autotransfusion. CONCLUSION: Autotransfusion can decrease the amount of homologous blood transfused following cardiac surgery. This represents a benefit to the patient and a decrease in cost to the health service.

Aortic rupture as a result of low velocity crush.

A case of aortic disruption in a 35 year old lorry driver is described. This occurred as a result of a low velocity crushing force. Clinicians should be aware that this mechanism of injury may result in aortic disruption as well as the more commonly mentioned severe deceleration force.

Enhanced circulatory parameters of human platelets cryopreserved with second-messenger effectors: an in vivo study of 16 volunteer platelet donors.

Platelet transfusion represents an important component of the therapy for thrombocytopenic patients. Prolonged storage capabilities for platelets would alleviate many problems associated with blood banking. Unfortunately, current cryopreservation methods are complex to implement and result in loss of cell number and functional activity. Previous in vitro studies have shown that the use of ThromboSolTM, a platelet-stabilizing formulation, in the cryopreservation of platelets results in significant retention of cell number and in vitro functional activities in addition to reducing the DMSO requirement to only 2%. We evaluated the in vivo circulatory parameters of platelets cryopreserved with ThromboSol. Single donor platelet units were obtained from healthy volunteers (n = 16); the units were then split and cryopreserved with either ThromboSol and 2% DMSO or 6% DMSO alone. Following storage at -80 degrees C for 7-10 d the samples were thawed, washed and radiolabelled with either 51Cr or 111In. The paired samples were then mixed and reinfused into the autologous volunteer. At various time intervals following transfusion a blood sample was drawn and the quantity of circulating labelled platelets was determined. The percent recovery and survival time was determined by multiple-hit analysis. The ThromboSol-treated platelets, as compared to the 6% DMSO-treated platelets, displayed statistically higher percent recovery (40.2% v 28.8%) and survival time (166.3 h v 152.1 h). These results demonstrated that platelets cryopreserved with ThromboSol displayed superior in vitro and in vivo characteristics as compared to the standard 6% DMSO method. The use of ThromboSol allowed for a 3-fold reduction in the DMSO concentration in conjunction with a 40% increase in circulating cell number and normal survival times.