Two-dimensional in vivo pressure/diameter relationships in the canine main pulmonary artery.

Ultrasonic measurement of blood flow within the main pulmonary artery (MPA) requires a precise knowledge of the mean blood velocity within this vessel and the cross-sectional area (CSA). Small conformational changes in the elliptical shape of the MPA have substantial effects on the calculation of CSA and, subsequently, flow. We examined the extent of these changes by measuring the pulsatile and mean elliptical dimensions of the MPA in nine anaesthetised, open-chested, mechanically ventilated mongrel dogs using two pairs of 10 MHz ultrasonic, piezoelectric crystals. These custom-made devices were sutured to the PA adventitia along the long and short cross-sectional axes 2 cm distal to the pulmonary valve. Axial dimensions were collected during normal, elevated (via noradrenaline and fluid additions) and reduced (via exsanguination) PA pressures. We confirmed the linear pressure/diameter response in 15/18 axial data sets (r greater than 0.80). Further, the linear axial responses of the long and short diameters were parallel (7/9, p less than 0.05) and have different zero-pressure intercepts (7/9, p less than 0.0001). A mathematical consequence of this parallelism is predictable, although non-constant, eccentricity. Finally, error analysis of multi-axial measurement techniques were shown to improve CSA accuracy by as much as 50% when compared with uni-axial determinations.

Velocity profile in the main pulmonary artery in a canine model.

The velocity profile of the main pulmonary artery was determined in nine adult, open-chested, mechanically ventilated mongrel dogs using an intraluminal, needle-mounted, range-gated, pulsed Doppler technique. Mean phasic point velocities were determined at 2 mm intervals across the lumen of the vessel, 2 cm above the pulmonary valve, by recording the Doppler shift of an activated 20 MHz piezoelectric crystal, range-gated 3.5 mm in the direction of the pulmonary valve. Mean Reynolds numbers from the main pulmonary artery ranged from 275 to 1140. Radially normalised intraluminal distance versus mean phasic point velocity plots were constructed which demonstrated a curved profile in all 9 dogs. First order regression analysis demonstrated a poor fit (r: 0.05-0.68). Second order (r:0.61-0.97) and third order (r:0.72-0.99) regression analyses markedly improved the fit, confirming the non-linear nature of the velocity profile. Step-wise third order regression analysis to determine the importance of the entry sequence demonstrated that the most important term for determining the regression coefficient was the X2 term in six dogs. In addition, the velocity profile was noted to be shifted, with the highest velocities recorded between the centre of the vessel and the anterior wall in eight of nine dogs (location of highest velocity: +0.26 radius +/- 0.25 (mean +/- SD).

The velocity profile in the canine ascending aorta and its effects on the accuracy of pulsed Doppler determinations of mean blood velocity.

The velocity profile in the ascending aorta, which has been variously reported as parabolic, skewed or flat, was measured using an intraluminal probe equipped with a miniature piezoelectric crystal activated by a 20 MHz pulsed Doppler with a 1 mm3 sample volume size. Phasic velocities, determined via spectral analyses, were obtained at 2 mm intervals across the aortic lumen of anaesthetised open-chest dogs by sequentially moving the crystal between posterior and anterior walls, maintaining the ultrasound beam parallel to the flow axis. Range-gating allowed data acquisition 3.5 mm proximal to the crystal, thus eliminating probe induced turbulence. Time and spatial distributions of velocities over the cross-section were computed. Expected errors in vessel mean velocity estimates based on point measurements were calculated. Analysis of phasic waveforms showed increased posterior velocities during systole but third order regression analysis of normalised point mean velocities across the lumen showed the best fit was a statistically flat straight line. Centreline referenced analyses indicated the expected difference between point mean velocity and vessel mean velocity was maximal (19.3 +/- 10.1%) 4 mm toward the posterior wall and minimal (4.7 +/- 9.1%) 5 mm toward the anterior wall. Anterior posterior wall referenced analyses indicated the most reliable position for estimating vessel mean velocity from point mean velocity along this axis was 5 mm from the anterior wall.

Endothelial cell preservation using organ storage solutions.

The development of organ preservation solutions has been primarily accomplished in whole organ animal models. This study examines the toxicity of commonly used organ preservation solutions on endothelial cells in vitro. Primary human umbilical-vein endothelial cell cultures were incubated at 4 degrees C in solutions of 0.9% saline (NS), EuroCollins, ViaSpan (Belzer UW) (VIA), or Hank's balanced salts with 5% polyethylene glycol (PEG). Endothelial cell viability was ascertained by colormetric measurement of mitochondrial reduction of 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) to purple 1-(4,5-Dimethylthiazol-2-yl)-3,5-diphenylformazan. After exposure to hypothermic storage, cells were incubated at 37 degrees C in media with MTT, and the amount of reduced formazan present was quantified using a micro-ELISA spectrophotometer. Higher absorbance values were indicative of better cellular preservation. Cells stored in PEG displayed the highest viability at all time periods. ViaSpan provided better cellular protection than EC at longer storage intervals. This model allows for rapid assessment of preservation-induced endothelial cell injury and may aid development of improved storage techniques.

Improvement of endothelial cell viability at 4 degrees C by addition of lazaroid U74500A to preservation solutions.

Lazaroids are potent inhibitors of lipid peroxidation. Endothelial cell damage has been shown to occur during cold storage preservation of lung and liver. This study examines the effects on endothelial cell viability of the addition of four lazaroids, U74006F, U78518F, U74500A, or U75412E to preservation solutions. Human umbilical vein endothelial cell cultures were stored at 4 degrees C for 48 and 96 hr in EuroCollins or 5% polyethylene glycol in buffered saline (PEG). U78518F, U74500A, U74006F, U75412E, or dexamethasone (each 50 microM) was added to EC (n = 32) or PEG (n = 32) and compared with control solutions of EC or PEG alone. Endothelial cell viability was determined by measuring cellular reduction of 3-[4,5-dimethylthiazol-2-yl]-2,3-diphenyltetrazolium bromide to a purple formazan dye. The reduction occurs only in viable cells and requires mitochondrial dehydrogenase activity. Results were quantified by measuring dye absorbance (Ab) with a micro-ELISA spectrophotometer. Absorbance values were compared by ANOVA and reported as mean values +/- standard deviation. Addition of U74500A to EC (Ab = 0.474 +/- 0.055) and PEG (Ab = 0.462 +/- .005) improved viability at 48 hr when compared with EC (Ab = 0.289 +/- 0.069) and PEG (Ab = 0.287 +/- 0.052) alone (P less than 0.05). At 96 hr, addition of U74500A resulted in improved viability in both EC (Ab = 0.377 +/- 0.068) and PEG (Ab = 0.195 +/- 0.09) or PEG alone (Ab = 0.212 +/- 0.1) (P less than 0.05). Other lazaroids tested were also effective in improving cellular viability, but to a lesser degree than U74500A. This study demonstrates that the addition of lazaroids to organ preservation solutions improves endothelial cell viability.

Maturation of pulmonary input impedance spectrum in infants and children with ventricular septal defect.

To determine whether pulmonary vascular disease can be detected in infants with ventricular septal defect (VSD) by the presence of an increase in the frequency of the impedance modulus minimum of the pulmonary input impedance spectrum, as has been implied for older children, spectra of 25 infants (2 years or younger) (group 1) were compared with spectra of 20 children (ages 2 to 7 years) (group 2). Groups were subdivided according to mean pulmonary artery (PA) pressure: those with moderate pressure levels (35 mm Hg or less, groups 1A and 2A) and those with high pressure levels (at least 40 mm Hg, groups 1B and 2B). Pulmonary vascular resistance, characteristic impedance and frequency of the modulus minimum were significantly lower in group 2A than in group 1A. The decrease in pulmonary vascular resistance and characteristic impedance with increasing age was consistent with body surface area increases; however, the shift in frequency of the modulus minimum could be more easily related to a decrease in the pulse wave velocity than to a shift in the primary reflection site. Pulmonary vascular resistance, characteristic impedance and the frequency of the first modulus minimum were comparable in groups 1B and 2B; however, none of the patients in group 1B had evidence of pulmonary damage, whereas 3 of 4 group 2B patients had microscopically apparent pulmonary vascular disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Constant postoperative monitoring of cardiac output after correction of congenital heart defects.

A new method has been developed that permits constant postoperative monitoring of mean and phasic cardiac output in patients after correction of congenital heart defects. A miniature ultrasound probe is attached to the adventitia of the ascending aorta at the conclusion of the operative procedure. This is connected to the monitoring equipment by means of polyurethane-covered wires that exit the chest wall through a small stab wound. The probe can easily be removed by gentle traction when the patient's condition is stable. The technique was developed, validated, and refined in extensive animal studies, and this report describes the first series of 20 consecutive human implants, performed between August 1984 and September 1985, in which the absolute cardiac output determination obtained with the ultrasound probe at the time of its application was correlated with cardiac output as measured with a standard electromagnetic flow probe. Fourteen male and six female patients (mean age 5.5 years) were studied. Operations performed included eight atrial septal defect repairs, four procedures for tetralogy of Fallot, three ventricular septal defect repairs, three stenotic valve corrections, and two Senning operations. One operative death occurred, but no complications were related to probe application or removal. The average cardiac output in the 20 patients as measured with the ultrasound probe was 2.2 +/- 1.1 L/min (range 0.67 to 5.27 L/min). This is nearly identical to the results noted with the electromagnetic flow probe, where the mean cardiac output was 2.3 +/- 1.2 L/min (range 0.7 to 6 L/min). Regression analysis revealed a high linear correlation (r = 0.9) between the two techniques. A monitor can display the cardiac output trend with 1 minute updates, which greatly enhance management of intravenous drug therapy and volume administration. In conclusion, this new extraluminal removable probe allows virtually continuous monitoring of the postoperative cardiac output after correction of congenital heart defects and should become a standard technique in the postoperative care of these patients.

Innominate artery occlusive disease: management with central reconstructive techniques.

BACKGROUND: The purpose of this study was to review our experience with central vascular reconstruction for innominate artery occlusive disease. Eighteen patients underwent central reconstruction for innominate artery (IA) occlusive disease during an 8-year period (1986 to 1994). Mean age was 59 years (range, 36 to 77 years). Women outnumbered men 12 to 6. All patients had symptoms including amaurosis fugax 55%, transient ischemic attacks 44%, vertebrobasilar insufficiency 44%, and arm claudication 33%. The IA was occluded in three patients and stenotic in 15. Three patients underwent previous extrathoracic bypass procedures for IA lesions that failed. METHODS: Operations performed through a median sternotomy included aortocarotid bypass with reimplantation of the subclavian (n = 10) and aortoinnominate bypass (n = 7). Transection and oversewing of the IA was performed in all but one patient, in whom ligation of the IA was performed. One patient with severe chronic obstructive pulmonary disease and previous coronary artery bypass grafting underwent retrograde-transluminal IA angioplasty with endovascular stent placement via a carotid approach. Four patients underwent concomitant carotid endarterectomy). Two patients underwent concomitant coronary artery bypass grafting at the time of IA reconstruction. RESULTS: There was one operative death from myocardial infarction. Perioperative morbidity included dysrrhythmia (three), respiratory insufficiency (three), subendocardial myocardial infarction (two), cerebrovascular accident with complete recovery (two), hemorrhage (one), and acute graft occlusion (one). All grafts remained patient at a mean follow-up of 21 months (range, 8 to 60 months). The only patient who underwent ligation of the IA required a subsequent revision of the IA to transection and oversewing for an embolic event at 4 months status-post aortocarotid bypass. The patient who underwent angioplasty remained asymptomatic with a patient IA at 12 months. Average length of stay for transthoracic repair was 14 days and for transluminal angioplasty 2 days. CONCLUSIONS: Innominate artery bypass based on the ascending aorta is effective in providing relief of symptoms and has a high patency rate. Because of the significant morbidity, these procedures should be reserved for patients with symptoms. The IA should be transected and oversewn to prevent recurrent embolism. Transcarotid, retrograde angioplasty provides an alternative approach to stenotic lesions located in the IA or proximal common carotid artery. An aggressive approach directed at defining coronary artery disease is an invaluable adjunct to the proper treatment of this patient population.

Objective measurement of limb perfusion by dermal fluorometry. A criterion for healing of below-knee amputation.

Quantitative fluorometry has been recommended as an accurate adjunct to clinical judgment in the preoperative assessment of lower-extremity amputation level. In this prospective study of 56 patients who had below-knee amputation, clinical judgment was used as the sole criterion for site selection. Quantitative fluorometry was compared with clinical judgment in a prospective, blinded study. All patients were studied before amputation with administration of intravenous fluorescein. Fifteen minutes after injection, objective measurement of dye fluorescence was performed at multiple sites with a quantitative fluorometer, and a dye fluorescence index was derived. All limbs undergoing amputation were ischemic, manifested by rest pain, nonhealing ulcers, or gangrene. Five patients (8.7%) failed to heal at the below-knee level. The mean dye fluorescence index for the group that healed was 81 +/- 51 (range, 13 to 259) and for the group that failed to heal, 110 +/- 49 (range, 70 to 195). Objective measurement of fluorescein perfusion did not correlate with amputation healing at the below-knee level in our patient population.

Aneurysms of the abdominal aorta. Incidence in blacks and whites in North Carolina.

We examined race and sex relative to the unexpected finding of an abdominal aortic aneurysm (AAA) at 1,665 autopsies plus 545 abdominal computed tomographic scans in subjects over the age of 50 years. We compared our demographic data with those of North Carolina and our hospital to determine if the data base was representative. White males had a higher incidence (4.2%) of AAA than any other group of race and sex (1.2% to 1.6%) or combination of groups. Although whites (2.9%) had a higher incidence than blacks (1.5%) and males (3.4%) had a higher incidence than females (1.3%), this can be attributed to the influence of the white male. The demographic data of the group studied were similar to those of our institution's admissions and to the North Carolina population. We conclude that (1) there is an increased incidence of AAA in the white male compared with the white female, black male, and black female in North Carolina; (2) there is no difference in the incidence of AAA in the white female, black male, and black female; (3) race alone may not influence the incidence of AAA as there was no difference between white and black females.

Oculoplethysmography/carotid phonoangiography: its value as a screening test in patients with suspected carotid artery stenosis.

A review of 291 carotid arteries that were subjected to both oculoplethysmography/carotid phonoangiography (OPG/CPA) and arteriography showed that although 84% of the vessels that were narrowed less than 40% were properly categorized by the noninvasive test, there was poor grading ability for lesions 40% or greater, and an unacceptably high (40%) false-negative rate for marked carotid stenoses. This has been confirmed by others. Analysis of a 15-item questionnaire that was returned by 12 clinicians showed an unwarranted reliance on the OPG/CPA as a screening test in those patients without transient ischemic attacks. A large majority of responding physicians favored endarterectomy in asymptomatic patients with lesions greater than 70%, and the use of OPG/CPA prevented a substantial number of affected individuals from undergoing angiography and subsequent corrective surgery.

Management of aortobronchial fistula with graft replacement and omentopexy.

Massive hemoptysis due to a recurrent aortobronchial fistula after repair of a thoracic aortic aneurysm developed in a 64-year-old woman. The infected aortic tissue was resected and replaced with an in situ Dacron graft covered by omentum. The patient is alive and well 15 months later.

Endothelial cell thromboxane production and its inhibition by a calcium-channel blocker.

Vascular endothelium has been established as a major source of prostacyclin production. Whether endothelial cells are also capable of synthesizing thromboxane A2 remains controversial. Suppression of such endothelial thromboxane synthesis would be beneficial for short-term patency of vascular grafts. This study examined the production of thromboxane A2 by endothelial cells and its modulation by the calcium-channel blocker nifedipine in vitro. The results indicate that (1) endothelial cells spontaneously secrete thromboxane A2, (2) this production can be enhanced severalfold in the presence of arachidonic acid, and (3) the calcium-channel blocker nifedipine significantly inhibits thromboxane production without demonstrable toxicity to the endothelial cells.

Oxygen free radical scavengers decrease reperfusion injury in lung transplantation.

An in vivo canine model was used to assess the ability of an oxygen free radical scavenger to decrease reperfusion injury in lung transplantation. In 12 dogs, the left lungs were transplanted after they had been preserved for 24 hours at 4 degrees C after pulmonary artery flushing with modified Eurocollins solution. In 6 dogs, dimethylthiourea, a potent oxygen free radical scavenger, was added to the flush solution and was also given to the recipients just before reperfusion. In all animals, the contralateral pulmonary artery and bronchus were ligated and lung function was assessed for 12 hours or until death. Three dogs died prematurely in the control group, whereas only 1 dog died prematurely in the dimethylthiourea group. This resulted in a statistically significant difference in the average length of survival (p less than 0.05). Pulmonary artery and right atrial pressures were significantly lower in the dimethylthiourea group during the first 6 hours (p less than 0.05). Treatment with dimethylthiourea resulted in a significantly higher arterial oxygen tension at 4 hours, and intrapulmonary shunt tended to be lower. Thus, it would appear that dimethylthiourea has a protective effect on lungs preserved for 24 hours before transplantation in dogs.

Enhanced pulmonary function using dimethylthiourea for twelve-hour lung preservation.

Current preservation techniques for lung transplantation limit ischemic time to 6 hours. The purpose of this study was to evaluate the ability of dimethylthiourea, a low molecular weight free radical scavenger, to prolong this interval. An in vivo canine transplantation model was used to assess lung function. At harvest and after circulatory arrest, the donor lung was flushed with modified Euro-Collins solution (50 mL/kg). In a blinded fashion, dimethylthiourea (5 g) or saline solution was added to the flush solution at harvest and also infused (20 g over 2 hours) at reimplantation. Harvested lungs were stored for 12 hours at 4 degrees C. Allotransplantation was performed in recipient dogs ventilated with 40% O2. After 1 hour, the contralateral pulmonary artery was ligated, forcing the dog to be dependent on the transplanted lung. Twelve dogs were studied, with 6 randomly assigned to each treatment group in a blinded fashion. Measurements were recorded for 8 hours, keeping the inspired oxygen fraction constant at 0.40. All dimethylthiourea-treated dogs survived the observation period, whereas one third of the dogs that received saline solution died. Dimethylthiourea-treated dogs had significantly greater arterial oxygen tension and significantly less pulmonary vascular resistance compared with control animals. These results suggest that treatment of the lung with a free radical scavenger (dimethylthiourea) improves pulmonary function after reimplantation in a canine model after 12-hour hypothermic storage.

Surgical management of symptomatic pulmonary aspergilloma.

Pulmonary aspergilloma is a potentially life-threatening disease resulting from the colonization of lung cavities by the ubiquitous fungus Aspergillus fumigatus. Complex aspergilloma, characterized by thick-walled cavities with surrounding parenchymal inflammation, is a risk factor for increased morbidity and mortality. Fifteen patients with symptomatic aspergilloma underwent major thoracic procedures at North Carolina Memorial Hospital between January 1, 1972, and December 31, 1983. Twelve of the patients had hemoptysis; in 7 it was recurrent and in 5, life threatening. Tuberculosis and sarcoidosis were the most common underlying causes of lung disease, and more than half of the patients had other coexistent serious medical illness. Eleven of the 15 patients were seen with complex aspergilloma; all of the 4 major complications and the 2 deaths occurred in these patients. Bronchopleural fistula with persistent air space was the most common serious complication, and required thoracoplasty in 3 patients. Nine patients, including 5 with complex aspergilloma, had no postoperative complications, and there were no recurrent symptoms in any of the 13 operative survivors over a mean follow-up of five years. It is concluded that aggressive pulmonary resection can provide effective long-term palliation in critically ill patients with symptomatic pulmonary aspergilloma.

The acute effects of pneumonectomy on pulmonary vascular impedance in the dog.

Pulmonary vascular impedance is a measure of the pulsatile characteristic of pressure and flow that occurs in the proximal pulmonary arteries. Pulmonary vascular resistance (PVR) is most influenced by the distal circulation of the lung. This study was performed to evaluate the changes that occurred in pulmonary vascular impedance, as well as in other hemodynamic variables, following pneumonectomy by a closed-chest method in 10 anesthetized dogs. The following observations were made (numbers compare mean values for the 10 dogs before and after pneumonectomy): (1) PVR increased from 447 to 761 dyne sec cm-5 (p = .02); (2) the oscillatory work of the right ventricle increased from 1.23 to 1.76 J/min (p = .006); (3) the mean pulmonary artery pressure increased from 14 to 18.8 mm Hg (p = .0001); and (4) cardiac output and heart rate remained unchanged. Surprisingly, the estimated characteristic impedance (the impedance to oscillatory flow in the proximal bed) did not change significantly (279 to 296 dyne sec cm-5). This observation cannot be explained by the usual lumped compartmental models classically used to characterize the pulmonary vascular bed.

Flow cytometric analysis of organ preservation-induced endothelial cell membrane damage.

Organ preservation for transplantation is associated with endothelial cell damage. This vascular injury results in increased capillary permeability, graft edema, and early graft dysfunction. This damage may be the limiting factor in preservation of these organs. This study uses flow cytometric assessment of membrane integrity to examine the effects of various organ preservation solutions on human umbilical vein endothelial cell cultures. Confluent plates of human umbilical vein endothelial cells were incubated at 4 degrees C for 24, 48, and 72 hours in commonly used preservation solutions. After cold incubation, the cells were harvested and stained with propridium iodide and fluorescein diacetate. Cells were examined using a flow cytometer for membrane integrity and cytosolic activity. When examined after 24, 48, and 72 hours, cells stored at 4 degrees C in a 5% polyethylene glycol salt solution were significantly less damaged than those stored in any other solution (p less than 0.05). After 48 and 72 hours at 4 degrees C, cells stored in ViaSpan were significantly more intact than cells stored in EuroCollins and 0.9% saline solution (p less than 0.05). This study demonstrates that endothelial cell damage occurs during cold storage and that a polyethylene glycol-based solution showed superior cellular preservation.

Reperfusion injury in the lung preserved for 24 hours.

The left lower lobes of 28 canine lungs were isolated, preserved, and then reperfused for 150 minutes. Five groups of lobes were studied: group 1, control (n = 5); group 2, one hour of warm ischemia (n = 5); group 3, one hour of warm ischemia + oxygen free radical scavengers (n = 5); group 4, 24 hours of cold ischemia (n = 8); and group 5, 24 hours of cold ischemia + oxygen free radical scavengers (n = 5). Oxygen free radical scavengers consisted of superoxide dismutase and catalase (100 micrograms/mL) given at the moment of reflow. Extravascular lung water (grams per gram of blood-free dry lobe weight) after reperfusion was 2.75 +/- 0.19, 5.46 +/- 0.60, 4.08 +/- 0.37, 9.43 +/- 0.98, and 6.91 +/- 0.95 for groups 1 through 5, respectively (p less than 0.05, groups 2 through 5 versus group 1; p less than 0.05, group 2 versus group 3 and group 4 versus group 5). Lung tissue lipid peroxidation, measured as thiobarbituric acid reactive material, was 117 +/- 14, 314 +/- 19, and 163 +/- 25 nmol/g dry lobe weight for groups 1, 4, and 5, respectively (p less than 0.05, group 4 versus group 1 and group 4 versus group 5). The data suggest that oxygen free radical scavengers attenuate reperfusion injury after long-term hypothermic lung preservation.

Selective application of fundoplication in achalasia.

Although esophagomyotomy alone may effectively relieve dysphagia in patients with achalasia, utilization of a complementary fundoplication procedure should be considered for selected patients. Fundoplication is a sensible addition to myotomy in circumstances that suggest high risk for the development of reflux esophagitis. Also, in complicated achalasia, relief of esophageal obstruction by simple myotomy may not be achieved safely. Identification of those pathological features associated with achalasia that merit consideration of fundoplication should improve operative results and reduce morbidity. This paper examines the application of a complementary fundoplication procedure in the operative management of 21 patients with achalasia over a ten-year period.