Vascular ultrasound studies for the non-invasive assessment of vascular flow and patency in experimental surgery in the pig

Vascular ultrasound is a reliable non-invasive tool used for the routine assessment of vascular flow and patency in human recipients. We describe the use at three different time points (immediately, 1 week and 4 weeks postsurgery) of ultrasound studies and its validation by angiographic studies in 37 swine undergoing carotid graft replacement. We calculated predictive values (>92%), sensitivity (>85%) and specificity (>92%) with high results at all time points. Ultrasound appeared as an accessible non-invasive technique, providing rapid, safe, repeatable and reliable results. It is an excellent alternative to angiography, avoiding risks inherent to invasive methods and therefore contributing to animal welfare.

Prevention of cardiac allograft rejection by FK506 and rapamycin: assessment by histology and nuclear magnetic resonance

We assessed the effect of FK506 and rapamycin (RPM) in a heterotopic abdominal rat heart transplant model using a major histocompatibility mismatch (DA to LEW). The end-point of our study was the histologic grading of rejection (Stanford) and 31P magnetic resonance spectroscopy (MRS) at 1 week after transplantation. Two dosages of FK506 (2.0 and 8.0 mg/kg per os daily) and RPM (1.5 and 6.0 mg/kg intraperitoneally daily) were compared in allografts without and with cyclosporine (12.5 mg/kg per os daily) treatment. The results show: Weak heartbeat and full rejection at day 5 in all untreated allografts; severe rejection in groups on a low dose of FK506 and RPM; mild rejection in both high dose groups comparable to the results of the hearts treated with cyclosporine; MRS does not allow differentiation between no or mild forms of rejection. Energy-rich phosphates are near normal in the high dosage immunosuppression groups but show a significant reduction in the low dosage groups. We conclude that all three tested drugs can reduce the degree of rejection from severe (untreated allografts) to mild if given in an adequate dosage. MRS correlates well with the degree of histologic rejection but permits only the diagnosis of moderate or severe rejection.

Intra- and postoperative quality control in minimally invasive direct coronary artery bypass (MIDCAB) surgery

The introduction of new techniques allowing direct coronary artery revascularisation without sternotomy and extracorporeal circulation--called Minimally (or less) Invasive Direct Coronary Artery Bypass grafting (MIDCAB)--has opened up interesting perspectives for the treatment of patients with limited coronary artery disease. However, like any newer surgical technique, this approach to myocardial revascularisation requires a critical appreciation of the results which may be obtained; when introducing the MIDCAB technique in our institution we developed a quality control protocol based on intraoperative as well as early and late postoperative parameters. This protocol is designed to detect every significant adverse event, exercise capacity and quality of life of our patients. Moreover, several invasive parameters have to be recorded in the protocol, such as intraoperative flow in the internal mammary artery conduit, the angiographic verification of anastomotic patency at one-year follow-up and determination of coronary flow reserve. The results of the first 5 patients observed up to one year postoperatively are presented: all anastomoses were patent and the flow within the internal mammary artery was 69 +/- 40 ml/min at one-year follow-up angiography; this compares very favourably with the flow measured at the end of the operation, which was 31 +/- 8 ml/min. This demonstrates very clearly that internal mammary artery flow is recruitable and usually significantly increases within the first months postoperatively. Coronary flow reserve was 3.4 +/- 1.1 (normal value > 2.5). The results obtained in this pilot study, which was designed to establish a quality control protocol, are very satisfactory and confirm previous experience that this technique may be offered to selected patients with appropriate coronary anatomy.

Different techniques of distal aortic repair in acute type A dissection: impact on late aortic morphology and reoperation

OBJECTIVE

To compare three different techniques of distal aortic repair in acute type A (de Bakey type I) aortic dissection and to evaluate their impact on the late morphology of the aortic arch and descending aorta and on the incidence of reoperation.

METHODS

From 65 patients operated on due to an acute type A aortic dissection between 1989 and 1993, 54 long-term survivors underwent clinical and radiologic follow-up examination after a mean postoperative interval of 62+/-16 months. The surgical techniques of distal aortic reconstruction included closed repair using Teflon felt reinforcement under moderate hypothermic cardiopulmonary bypass (n = 20) and open repair in deep hypothermic circulatory arrest using either Teflon felt reinforcement (n = 16) or gelatin-resorcin-formaldehyde (GRF) glue (n = 18) to readapt the dissected aortic layers. In all patients, MR imaging was performed on a 1.5-T whole body imaging system for the evaluation of the morphology and function of the heart, aorta and supraaortic branches.

RESULTS

Overall hospital mortality following surgical repair of type A aortic dissection was 15.4% during this time period. The highest rate of persistent false lumen perfusion (17/20, 85%) and presence of an intimal flap in the aortic arch (13/20, 65%) was observed in patients following closed repair of acute ascending aortic dissection, whereas the lowest rate of such findings was demonstrated in patients who had undergone open distal aortic repair using biological glue (false lumen perfusion 10/18, 55% and intimal flap in the arch 2/18, 11%). Redo-surgery was significantly reduced in the open repair group using GRF glue (1/18, 5.5%) as compared with the Teflon felt repair group (3/16, 18%) and the closed repair group (6/20, 30%).

CONCLUSIONS

In patients with acute type A dissection, open distal aortic repair using GRF-glue favourably influences both (1) the severity of late morphologic alterations in the downstream aorta and (2) the incidence of reoperation.

Use of epoetin alfa in autologous blood donation programs for patients scheduled for elective cardiac surgery

The optimum dosage of subcutaneous (s.c.) epoetin alfa was assessed in a double-blind study in 31 patients scheduled for cardiac surgery. Patients received a total of four doses of either epoetin alfa 150 IU/kg (n = 11), epoetin alfa 300 IU/kg (n = 10), or placebo (n = 10) administered as single s.c. injections at weekly intervals starting 23 days prior to surgery. AB was collected with isovolemic replacement prior to each of the first three doses of medication. During the AB donation period, Hb levels decreased significantly (P < .05) from baseline to surgery in the placebo group (16.5%), compared with no significant decrease in either of the epoetin alfa groups (8.1% and 9.7% in the 150 IU/kg and 300 IU/kg groups, respectively). In addition, the difference between groups with regard to the decrease in Hb level reached statistical significance (P < .05) for the 150 IU/kg group versus placebo. Epoetin alfa treatment was also associated with significantly higher reticulocyte counts and serum erythropoietin levels in the preoperative period compared with placebo.

[Intraoperative aspiration and reinfusion of autologous blood in resection of abdominal aortic aneurysms with Solcotrans plus]

Quantitative and qualitative assessment of intraoperative aspiration and reinfusion of autologous blood with the Solcotrans was carried out in 11 males (52-79 years) undergoing elective resection of abdominal aortic aneurysms. Hematology, blood chemistry, coagulation parameters and complement activation were studied in the patient's blood at the following time points: preoperatively, before and after heparinisation, after retransfusion of the first and last Solcotrans, 6 and 20 hours postoperatively. In addition the same quality control was performed in the first and last Solcotrans blood. Results (mean values of 11 patients +/- 1 SD): Intraoperatively 2-3 Solcotrans units were salvaged (total 1039 +/- 565 ml) of which 805 +/- 487 ml were retransfused to the patients. As a mean patients required only 1 unit of homologous RBC's (395 +/- 781 ml) intraoperatively. Patient's intraoperative hemoglobin concentration amounted to 10 g/dl or more. Whereas the hemoglobin level in the Solcotrans attained only 8.2 g/dl. Thrombocyte counts (48 +/- 18 x 10(9)/l) and ionized calcium (0.2 +/- 0.4 mmol/l) were significantly depressed when compared to the preoperative patient values (p < 0.05). The protein concentration remained within normal limits in the patient's and in the Solcotrans blood. Complement activation (C4a, C5a [des Arg]) showed a significant increase after initiation of surgery and there was no significant difference between the solco- or patient blood. Whereas plasma free hemoglobin, coagulation and fibrinolysis parameters showed a significant elevation in the Solcotrans blood. In conclusion the solcotrans system offers a fast, efficient and simple method for salvage and retransfusion of intraoperative autologous blood.

Four-compartment fasciotomy and venous calf-pump function: long-term results

Twenty-one patients who underwent a four-compartment fasciotomy between January 1, 1986, and December 31, 1987, were revisited with respect to venous calf-pump function 32 to 56 months (mean, 46.2 months) after fasciotomy. Enrollment criteria consisted of an intact motor innervation, palpable pedal pulses, the absence of venous hypertension, and deep venous thrombosis before and during the treatment requiring fasciotomy and unimpaired ankle and knee joint function. None of the patients showed signs of chronic venous hypertension at assessment. Ambulatory strain-gauge plethysmography revealed no significant difference in recovery time and refilling volume values between the two limbs of each patient (p > 0.1) and between limbs in which fasciotomy was performed and those of normal subjects (p > 0.1). Color flow duplex scanning revealed patent popliteal veins with normal respiration-induced phasic flow pattern and absent reflux in all patients. All visible calf veins were patent, compressible, and without morphologic alterations. The fasciotomy wound was closed by delayed skin suture (the fascia remaining divided) in 48% and by skin grafts of the lateral incision in 52% of the patients, without significant difference in recovery time and refilling volume values (p > 0.1) at assessment. Fasciotomy does not lead to venous calf-pump dysfunction, irrespective of whether the wound is closed by delayed suture or skin grafts.

Influence of failed arterial reconstruction on the outcome of major limb amputation

BACKGROUND

Unsuccessful vascular repair may further preexisting limb ischemia and thus increase the risk of revascularization procedures.

METHODS

The results of 94 primary major amputations (group A) have been analyzed and compared with 112 secondary ablations (group B) carried out after failed revascularization efforts. All patients suffered from chronic critical ischemia (grades III and IV) of the lower extremities. In group A the severity of ischemic symptoms was more pronounced (trophic changes in 80% vs 66% in group B), and a preponderance for older age, diabetes mellitus, and incidence of cardiac failure and cerebrovascular insufficiency was evident.

RESULTS

In patients undergoing secondary amputation the final transection level was adversely affected by preceding unsuccessful reconstructive attempts. In spite of the better risk profile, 30% of patients in group B were subjected to above-knee amputation compared with 13% of patients in group A. The aggravated limb ischemia caused by graft failure is reflected by the decrease of the mean ankle systolic pressure index from 0.27 to 0.13 (before and after failed revascularization attempts). Although more amputations at the below-knee level were performed initially in group A, primary wound healing was obtained among these subjects in 68% of patients (compared with only 39% for patients in group B).

CONCLUSIONS

In a substantial number of cases preexisting limb ischemia may be promoted by failed attempts at vascular reconstruction, thus leading to severe wound healing complications and a higher level of amputation.

Assessment of new immunosuppressive drugs in a rat cardiac allograft heterotopic model

We assessed FK506 (FK) and rapamycin (RPM) in a heterotopic abdominal rat heart transplant model using a major histocompatibility mismatch (DA to LEW). The end point of our study was histologic grading of rejection (Billingham and working formulation) at 1 week. Two doses of FK (2.0 and 8.0 mg/kg p.o., q.d.) and RPM (1.5 and 6.0 mg/kg i.p., q.d.) were compared to allografts without and with ciclosporin (12.5 mg/kg p.o., q.d.) treatment. Results show: (1) weak heartbeat and full rejection on day 5 in all untreated allografts; (2) weak heartbeat and high degree of rejection in groups receiving low doses of FK and RPM; (3) strong heartbeat and mild rejection in both high FK and RPM dose groups comparable to the results of the hearts treated with ciclosporin; (4) 1 animal in each high FK and RPM dose group showed possible signs of toxicity, and (5) the strength of the heartbeat was not a reliable indicator of the efficacy of an immunosuppressive drug. We conclude that even in a major histocompatibility mismatch model at the time of the strongest immune response (1 week), all three tested drugs can reduce the degree of rejection from severe (untreated allografts) to mild if given in an adequate dosage.

[Accidental hypothermia in Switzerland (1980-1987)--case reports and prognostic factors]

This retrospective study comprises 234 cases of accidental hypothermia (core temperature less than 35 degrees C) hospitalized in 95 Swiss clinics between 1980 and 1987. The most frequent accidents were alpine (n = 78) in origin, followed by cold exposure after injuries (n = 63) and suicide attempts (n = 43). Hypothermia was induced by cold air in 129 cases and by water in 47 cases. Patients were divided evenly between the degree of hypothermia: 75 mild (32-35 degrees C), 79 moderate (28-32 degrees C) and 66 severe (less than 28 degrees C). Among the survivors the coldest patient had a core temperature of 17.5 degrees C and the longest cardiac arrest with a favourable outcome lasted 4.75 hours. Out of the 234 patients 68 died (29%). We assessed all variables relative to outcome, in particular the mechanism of the accident, the mode of cooling, temperature, circulation, age and sex, underlying diseases, rewarming methods, medication and complications during the hospital course. All variables were tested in two multiple regression analysis models (retrospective model n = 181: prospective model n = 128) with regard to significance (p less than 0.05) and survival. Results are expressed with ODD's ratios (OR). The negative survival factors are asphyxia (OR 30), invasive rewarming methods (OR 20), slow rate of cooling (OR 10), asystole on arrival (OR 9), pulmonary edema or ARDS during hospitalization (OR 8), elevated serum potassium (OR 2/mmol/l) and age (OR 1.03/year). The positive survival factors are rapid cooling rate (OR 10), presence of ventricular fibrillation in cardiac arrest patients (OR 9) and presence of narcotics and/or alcohol during hypothermia (OR 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium and catecholamines: relevance to cardiomyopathies and significance in therapeutic strategies

There are marked differences between human cardiomyopathies, especially of the hypertrophic variety, and animal models. There is no simple way in which a hyperadrenergic state can explain the contractile abnormalities, although additional effects of calcium overload or marked hypertrophy come somewhat closer to linking animal and human diseases. One of the best links between excess catecholamine stimulation and myocardial damage lies in the enhanced sarcolemmal permeability which is mediated by beta-adrenergic stimulation and calcium ions in an isolated rat heart model. The therapeutic success of beta-adrenergic blockade and especially calcium antagonists in no way provide firm evidence for a hyperadrenergic state nor for intracellular calcium overload. In human hypertrophic cardiomyopathy, these agents may be acting merely by enlarging cavity size. In dilated cardiomyopathy, the use of beta-adrenergic blockers is still highly controversial and calcium antagonists are not well tested. It is the lack of appropriate models for both hypertrophic cardiomyopathy and dilated cardiomyopathy which is holding up research in this important area.

[Reducing hemodilution through ultrafiltration following cardiopulmonary bypass]

Reduction of post-bypass-hemodilution by ultrafiltration was assessed. Five dogs were subjected to 1 hour of cardiopulmonary bypass and were hemodiluted with 2 liters of Ringer lactate solution to a hematocrit below 20%. An arterial hemofilter was then incorporated into the system and 1 liter of fluid was ultrafiltrated for 16 minutes during partial bypass. The filtrate was free of protein and hemoglobin. There was a significant increase of the hematocrit from 19 to 29%, and protein from 2,7 to 5,4 g%. No hemodynamic alterations were seen during or after filtration. Osmolality remained within normal limits (from 284 to 296 mOsm/kg). In addition, no electrolyte imbalance was found. The method is therefore safe for quick volume removal without the side effect of diuretics.

Hemodynamic changes after experimental reduction of the left atrium

Two experimental models were studied to determine the hemodynamic consequences of atrial volume reduction as observed after operative correction of transposition of the great arteries. The volume of the left atrium (LA) was reduced either by inflation of an intracavitary balloon (group A) or by surgical intervention (group B) to 50--60% of the control values as determined by angiography. The angiographic data correlated well with the true volumes obtained by water displacement. This major reduction of LA volume caused small but constant hemodynamic changes. Although the LA stroke volume decreased by 50% and the LA/LV volume relation was reduced by 50% (from 0.42 to 0.21), there was only a slight increase of pulmonary artery pressure (7% in group A and 14% in group B) and a slight decrease in cardiac index (13% in group A and 10% in group B) and in left ventricular end-diastolic pressure (9% in group A and 11% in group B). The reduction of atrial volume results in only minor functional alteration of the intact heart.

[Early scanning electron microscopy changes of the surface of the leaflets of orthotopic transplanted glyceraldehyd-conditioned conus-pulmonalis xenografts. An experimental study in dogs]

The surface of the leaflets of orthotopic transplanted glutaraldehyd-conditioned conus-pulmonalis xenografts show when analysed by a scanning microscope the following constant changes. Within seconds the surface of the leaflets is covered by a grainy layer of proteins followed by fibrin threads. Cellular elements of the blood--like platelets, white blood cells, macrophages and microthrombi--are incorporated in the fibrin network. This leads, after several weeks to a fibrous layer especially over the stiff parts of the valve. No endothelium was seen even after 6 months.