An assessment of the bioavailability of persistent organic pollutants from contaminated soil.

A procedure to assess the bioavailability of persistent organic pollutants (POPs) from soil samples has been developed. The procedure is based on the use of simulated in vitro gastrointestinal extraction to remove POPs from soil matrices. The level of recovery, using this approach, is assessed following liquid-liquid extraction (LLE) and analysis by gas chromatography-mass selective detection (GC-MSD). The remaining soil residue is then extracted using pressurised fluid extraction (PFE) followed by GC-MSD analysis to assess the residual fraction. The residual fraction is monitored to determine the unavailable fraction i.e. not available for absorption in the gastrointestinal tract of humans. The procedure was applied to four soil samples i.e. an aged, spiked soil and three certified reference materials (CRMs) contaminated with POPs. Recoveries of pesticides (lindane, endosulfan I, endrin, DDE, DDD and endosulfan II), phenols (cresol, TCP and PCP), and base neutral compounds (hexachloroethane, acenaphthene, dibenzofuran, fluorene and hexachlorobenzene) from aged, spiked soil following extraction with gastric fluid ranged from 0.8 to 8.3% while following intestinal extraction ranged from 5.5 to 13.5%, irrespective of POP. Recoveries of pesticides (lindane, endosulfan I, endrin, DDE, DDD and endosulfan II) from CRM 805-050 following extraction with gastric fluid were below the limit of detection while following intestinal extraction ranged from 5.3 to 12.8%. Recoveries of phenols (cresol, TCP and PCP) from CRM 401-225 following extraction with gastric fluid ranged from 1.6 to 2.0% while following intestinal extraction ranged from 4.1 to 5.4%. Recoveries of base neutral acid analytes (hexachloroethane, acenaphthene, dibenzofuran, fluorene and hexachlorobenzene) from CRM 107-100 following extraction with gastric fluid ranged from 1.4 to 4.0% while following intestinal extraction ranged from 6.6 to 12.7%. It has been found that the majority of POPs present i.e. >75%, would be excreted if consumed and not be absorbed in the gastrointestinal tract of humans.

Characterisation and analysis of persistent organic pollutants and major, minor and trace elements in Calabash chalk.

Analysis of Calabash chalk has been done using energy dispersive X-ray fluorescence spectroscopy (EDXRF), X-ray diffraction (XRD) and pressurised fluid extraction (PFE) followed by gas chromatography (GC) with mass selective detection (MSD). It was found by XRD that the composition of Calabash chalk was an aluminium silicate hydroxide from the kaolin clay group with the possible formula Al(2)Si(2)O(5)(OH)(4). Multi-elemental analysis by EDXRF was able to quantify 22 elements in Calabash chalk including lead at a mean concentration of approximately 40 mg/kg. A range of persistent organic pollutants were identified and quantified in Calabash chalk including alpha lindane, endrin, endosulphan II and p,p'-DDD using PFE-GC-MSD.

Prophylactic carotid endarterectomy in patients with high-grade carotid stenosis undergoing coronary bypass: does it decrease the incidence of perioperative stroke?

The etiology of perioperative stroke in patients undergoing isolated coronary artery bypass grafting (CABG) is multifactorial. One significant cause is thought to be high-grade internal carotid artery stenosis. Between April 1992 and June 1995, 1686 patients undergoing isolated CABG underwent preoperative carotid duplex scanning. This represented 77% of patients who underwent CABG during that time period (2188 patients). Sixty-eight patients (4.0%) had 80%-99% stenosis of at least one carotid artery. Fifteen patients underwent CABG without carotid intervention (Group I) and 53 patients underwent either carotid endarterectomy prior to CABG or simultaneous with CABG (Group II). Age, sex, history of prior neurologic events, ejection fraction, number of distal bypasses performed, total pump time, and aortic cross clamp times were similar between the two groups. Three patients in Group I developed a permanent postoperative neurologic deficit (20%) and one patient developed a transient deficit. The defect was focal and ipsilateral to high-grade stenosis in three patients and global in one. No patient in Group II developed either a transient or permanent neurologic deficit. There was one death in Group I in the patient who developed a global neurologic deficit and one death in Group II 2 weeks after CABG in a patient who had undergone prophylactic preCABG-carotid endarterectomy. Statistical analysis (Fisher's exact test, 2-tail) demonstrated a significant decrease both in total neurologic events (p = 0.001) and permanent neurologic defects (p = 0.005) in those patient undergoing prophylactic CE (Group II). Patients with 80%-99% carotid stenosis undergoing CEA prior to or in conjunction with isolated CABG have a decreased incidence of neurologic events postoperatively.

Aortic regurgitation in coronary artery bypass grafting: implications for cardioplegia administration.

BACKGROUND: Echocardiography can detect aortic regurgitation (AR) that may interfere with the adequate delivery of cardioplegia solution to the myocardium during cardiac operation. When aware of this lesion, the surgeon can modify the operative technique accordingly. We sought to evaluate the ability of intraoperative transesophageal echocardiography to detect AR and to correlate the severity of the lesion with the need for retrograde cardioplegia administration. METHODS: Eighty-four consecutive patients undergoing coronary artery bypass grafting were evaluated. When AR was noted by intraoperative transesophageal echocardiography, a cannula was placed in the coronary sinus for possible retrograde cardioplegia administration. The surgeon was unaware of the severity of AR. After operation, the severity of AR was quantitated using the ratio of the regurgitation jet width to the left ventricular outflow tract diameter. RESULTS: The AR patients who required retrograde cardioplegia had a significantly higher ratio of regurgitation jet width to left ventricular outflow tract diameter than those AR patients who did not (0.36 +/- 0.06 versus 0.19 +/- 0.06, p < 0.005). CONCLUSIONS: Transesophageal echocardiography can provide accurate information regarding the presence and severity of AR. The calculated severity of AR on transesophageal echocardiography is associated with the need for retrograde cardioplegia administration.

Improved lung preservation using Euro-Collins solution for flush-perfusion.

Satisfactory extended preservation of the lung has been difficult to obtain. This study investigated the influence of different total volumes and flow rates during flush-perfusion of the lung, and their effect on pulmonary artery pressure, flow distribution, regional lung temperature and functional performance of the lungs following transplantation after 24 hours. Fifteen mongrel dogs served as donors of the heart and lung block. Cold modified Euro-Collins solution was used as flush perfusate. Pulmonary artery and perfusion-line pressures were measured. The regional lung temperature was measured at one minute intervals with 5 myocardial temperature probes. Flow distribution was determined with micro-aggregated albumin labelled with Technetium 99. The heart-lung block was harvested, the right lung removed, and samples taken for gamma-counting. The left lung was stored in cold Euro-Collins solution and then transplanted. The inspired oxygen fraction (FiO2) was set at 0.4 and was kept constant throughout the procedure and the entire postoperative course. There were 3 groups of 5 animals each. In group A, the flush perfusate was administered at a total volume of 20 cc/kg over a period of 6 minutes. In group B the same volume of perfusate was administered at a pulmonary artery pressure (PAP) of 18 to 20 mmHg, resulting in a considerably shorter perfusion time (1.3 minutes). In group C 60 cc/kg of perfusate were given at the same flow rate as in group B, also resulting in PAP of 18 to 20 mmHg, but the perfusion time was increased to 4 minutes. Thus, groups B and C investigated the effect of increased pressure and volume of perfusate, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute and chronic aortic dissections--determinants of long-term outcome for operative survivors.

A total of 135 survivors of surgical treatment of aortic dissection was followed for up to 15 years after surgery. Actuarial survival rates were 82 +/- 4% at 5 years and 64 +/- 6% at 10 years. There were no significant differences in long-term survival rates of patients in four subsets based on type and acuity of dissections. The incidence of late reoperation (dissection-related) was 13 +/- 4% at 5 years and 23 +/- 6% at 10 years; again, there was no significant difference among patients with different types or acuity of dissection. Multiple variables were investigated by multivariate discriminant analysis. Significant independent risk factors for late death included stroke, chronic renal dysfunction, remote myocardial infarction, and operation in the early years of this study. Younger age, site of intimal tear (arch), and cardiac tamponade portended a significantly higher likelihood of late reoperation. Except for stroke, no complication of the dissection or intraoperative factor significantly influenced late survival. Patients in whom the intimal tear was located in the aortic arch had the highest probability of late reoperation. Thus, dissection type, acuity, and distal extent, whether or not the tear was resected or concomitant aortic valve replacement performed, and a host of patient-related characteristics had no significant influence on the generally excellent long-term prognosis after surgical treatment. Indefinite surveillance of the remaining natural aorta is imperative (with reoperation when indicated) to attain such results.

Operative risk of mitral valve replacement: discriminant analysis of 1329 procedures.

The influence of 34 variables on the operative mortality rate for isolated mitral valve replacement (MVR) was assessed by univariate and multivariate logistic regression analysis. The physiologic lesions were classified as stenosis (20%, operative mortality rate 8 +/- 1%), regurgitation (44%, operative mortality rate 13 +/- 2%), and mixed (34%, operative mortality rate 8 +/- 1%). Functional class (NYHA), previous myocardial infarction, and hepatic dysfunction were powerful independent clinical determinants of operative mortality (p less than .001), along with age at operation and emergency operation (p = .001, p = .04). Concomitant coronary artery bypass grafting or tricuspid annuloplasty, angina, ischemic etiology, and physiologic lesion were not significant independent determinants of operative risk. Interestingly, year of operation, prosthetic valve dysfunction, and previous cardiac surgery had no important effect on operative mortality. Early operative risk for MVR was related to preoperative cardiac and hepatic function. Prior myocardial infarction substantially increased the risk even if the mitral valve disease was not ischemic in origin. Increased operative mortality rate in the subgroup with mitral regurgitation was related to advanced left ventricular failure and myocardial infarction rather than the etiology of the mitral regurgitation. These clinical factors coupled with more refined measurements of left ventricular systolic pump function (independent of loading conditions) should permit more intelligent decision making regarding the optimal timing of MVR, at least in terms of early operative risk.

Determinants of operative mortality for patients undergoing aortic valve replacement. Discriminant analysis of 1,479 operations.

The influence of 35 preoperative and intraoperative characteristics on operative mortality risk after 1,479 isolated aortic valve replacement procedures (1967 to 1981) was investigated utilizing univariate and multivariate logistic regression analyses. Mean age at operation was 58 +/- 13 years; 72% of patients were men. Physiology was classified as aortic stenosis (58%), regurgitation (30%), or both (9%). The overall operative mortality rate was 7% +/- 1%, but there were substantial differences in operative mortality rates among physiological subgroups (aortic regurgitation, 10% +/- 2%; aortic stenosis, 6% +/- 1%; stenosis/regurgitation, 5% +/- 2%). Independent determinants of operative mortality rate in the entire group were advanced New York Heart Association functional class, renal dysfunction, physiological subgroup, atrial fibrillation, and older age. In the aortic regurgitation subgroup, functional class, atrial fibrillation, and operative year were independent predictors. In the aortic stenosis subgroup, the significant determinants were functional class, renal dysfunction, age, prosthetic valve dysfunction, and absence of angina. Concomitant coronary bypass grafting, previous operation, endocarditis, and ascending aortic replacement had no independent predictive effect on operative mortality rate. Thus, the early results of aortic valve replacement can be related to several specific variables describing the functional and physiological status of the patient. Operative mortality rate is not independently related to previous operation or concomitant operative procedures. Specific differences in risk factors exist among the various physiological subgroups, probably reflecting the pathophysiology of the different hemodynamic lesions. This information should provide for a more rational approach to aortic valve replacement, at least in terms of early risk/benefit deliberations.

Twenty years of lung preservation--a review.

Preservation of the lung remains a major challenge and hinders the development of distant lung and heart-lung block procurement, limiting the clinical application of these modalities. The progress made in the field of lung preservation is reviewed and the many unanswered problems are presented here.

Long-term hemodynamics following combined heart and lung transplantation in primates.

To assess the long-term hemodynamic consequences of combined heart and lung transplantation, we investigated six rhesus monkeys 2.6 to 4.6 years (mean 4.0) after operation. Total follow-up was 24.0 primate-years. Autotransplantation had been carried out in four animals and allotransplantation in two, and the hemodynamic results were compared with those in three normal monkeys of similar size. Each animal underwent simultaneous right and left heart catheterization and pulmonary arteriography. Hemodynamic measurements were made at three levels of inspired oxygen. Arterial oxygen tension was within normal limits in all animals, and pulmonary artery pressure and pulmonary vascular resistance index did not change significantly with changes in the levels of inspired oxygen. Indices of left ventricular systolic function were normal in all animals. Values for pulmonary artery pressure and pulmonary vascular resistance index were similar in the autograft and normal groups: in the allograft group, the average pressure was 30/17 mm Hg (mean 24) and the index was 5.6 units . m2--both levels significantly higher than normal (pressure was 16/10 mm Hg, mean 13, [p less than 0.001] and index was 2.5 units . m2 [p less than 0.02]). Pulmonary arteriography in the allograft group with the highest pulmonary vascular resistance index (6.1 units . m2) was compatible with pulmonary vascular disease. Pulmonary arteriograms in the remaining eight monkeys were normal. Prolonged survival following combined heart and lung transplantation is possible in primates. Autotransplantation (and probable persisting denervation of the cardiopulmonary axis) does not necessarily result in abnormal long-term hemodynamics. The elevation in pulmonary artery pressure and pulmonary vascular resistance index in the allograft group may be related to previous episodes of pulmonary rejection, infection, or drug reaction.

Aneurysmal degeneration of Blalock-Taussig shunts: identification and surgical treatment options.

Many Blalock-Taussig shunts (subclavian to pulmonary artery anastomoses) have been created and a significant number are still being done. Two cases of aneurysmal degeneration of a Blalock-Taussig shunt and their management are described. Development of this rare complication may be related to large shunt flow and long duration. Large, symptomatic or enlarging aneurysms should be repaired and smaller ones studied by serial computed axial tomography. A simple and safe approach to correct this lesion is division and oversewing of the proximal subclavian artery through an anterior approach, assuming adequate pulmonary blood flow is already present or can be established concomitantly.

Hemodynamic effects of various modes of cardiac pacing after operation for idiopathic hypertrophic subaortic stenosis.

The hemodynamic effects of varying heart rate and pacing site were studied in 6 patients with idiopathic hypertrophic subaortic stenosis following operative relief of outflow obstruction. Ventricular pacing (117 beats per minute) resulted in a 26% decrease in cardiac output (p less than 0.02), a 54% increase in pulmonary capillary wedge pressure (p less than 0.03), and a 23% decrease in mean blood pressure (p less than 0.05), compared with normal sinus rhythm (88 beats per minute). Slow atrial pacing (112 beats per minute) did not significantly alter any hemodynamic variable compared with normal sinus rhythm. Rapid atrial pacing (143 beats per minute) produced a similar degree of hemodynamic impairment as ventricular pacing. This study demonstrates that ventricular pacing at heart rates commonly used clinically and rapid atrial rates result in a significant fall in cardiac output. Preservation of atrial systole at heart rates that allow adequate diastolic ventricular filling of a hypertrophied, noncompliant ventricle is stressed. In addition, atrial electrodes are useful to record atrial electrograms or induce rapid atrial stimulation to treat supraventricular tachyarrhythmias.

Limits of myocardial protection with potassium cardioplegia.

Preservation of left ventricular function with various potassium-based cardioplegic solutions has been considered to be effective for at least 60 minutes during occlusion of the ascending aorta. The purpose of this study was to define the limits of protection offered by potassium alone. A single bolus of 150 ml of potassium (24 mEq per liter) in normal saline solution at 30 degrees C was injected in the aortic roots of foxhounds at the initiation of periods of 45 minutes, 60 minutes, and 75 minutes of aortic occlusion at a core temperature of 30 degrees C. Data derived from postischemic recovery phase ventricular function curves and force-velocity relations demonstrated excellent protection during 45 minutes of ischemia, inconsistent protection at 60 minutes, and poor protection at 75 minutes.