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Biomedical subjects

B R Wilcox

Publications and source records attributed to B R Wilcox.

At least 73 records · Page 4Linked to original sources
PubMed1984

Esophagogastrectomy as palliative treatment for esophageal carcinoma: results obtained in the setting of a thoracic surgery residency program.

The palliative treatment of esophageal carcinoma has included intubation, bypass, dilation, irradiation, and esophagogastrectomy. The last has been criticized by some on the basis of high operative morbidity and mortality. To assess the success of this method at our institution, we reviewed the 60 consecutive resections performed for carcinoma of the esophagus from January, 1972, through June, 1983. Forty-six patients had squamous cell tumors and 14, adenocarcinomas. There were 47 men and 13 women, and the mean age was 59.9 years (range, 38.5 to 78.9 years). The most frequent preoperative findings included dysphagia (55), weight loss (34), chest pain (22), and vomiting (49). Fifty (83%) out of the 60 resections were performed by the resident staff under the supervision of an attending surgeon. Four patients died within 30 days of operation, an operative mortality of 6.7%. Immediate causes of death included respiratory failure, myocardial infarction, hemorrhage, and renal failure. One of the patients who died and 3 of the survivors had an anastomotic leak. There were 27 additional complications in 24 patients: respiratory problems (8), arrhythmias (5), pleural effusion (4), gastric outlet obstruction (2), wound infection (2), and 1 each of pulmonary embolus, acute brain syndrome, congestive heart failure, myocardial infarction, chylothorax, and empyema. The one-, two-, three-, and five-year actuarial survival rates were 46%, 27%, 10%, and 5%, respectively. Mean survival for the 46 patients dead at the time of this study was 13.5 months. Outpatient follow-up data were available on 53 (95%) of the operative survivors and showed an absence of dysphagia in 87.5% during most of the follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1984

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).

Animals↗
PubMed1984

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.

Animals↗
PubMed1984

A review of morbidity and mortality in elderly patients undergoing pulmonary resection.

The morbidity and 30-day operative mortality were reviewed in the 43 patients 70 years of age or older who underwent pulmonary resection between June 1976 and May 1981. In addition to their surgical illness, many of these patients had pre-existing medical conditions including: coronary artery disease (8), hypertension (14), diabetes (4), and congestive heart failure (5). The mean preoperative 1 second forced expiratory volume (FEV1) was 1.7 liters and 17 patients had an FEV1 of less than 1.5 liters. The operative mortality was 2.3% (one patient), the average duration of postoperative hospital confinement was 9 days, and 39 of 42 (93%) of the patients were discharged within 2 weeks of their operation. There were 38 postoperative complications in 25 of the 42 survivors, most of which were minor and all of which were resolved. Problems included: air leak (13), atrial fibrillation or flutter (3), myocardial infarction (1), respiratory difficulties (9), hemorrhage (2), mental confusion (3), hyperpyrexia (3), difficult-to-manage diabetes (1), and social problems (3). Only two patients required prolonged mechanical ventilation. The low operative mortality, the short postoperative stay, and the minimal number of serious complications is contrasted with other published reports describing a high-operative mortality in elderly patients. The improvement may be related to recent advances in postoperative management and anesthetic techniques. These data suggest that advanced age is not a contraindication to curative pulmonary resection.

Age Factors↗
PubMed1983

Surgical anatomy of double-outlet right ventricle--a reappraisal.

In light of the recent developments in surgical treatment of double-outlet right ventricle, the anatomic observations on this lesion were reevaluated. For this review, double-outlet right ventricle was diagnosed when more than half of both arterial valves were connected to the same ventricle, although appreciating the reasons for using, in a clinical context, a "90% rule" rather than the "50% rule" used in this review. Although this ventriculo-arterial connection can exist with any segmental combination, most often it is found in the setting of usually arranged atrial chambers (solitus) and atrioventricular concordance. Categorization of this subset is then done on the basis of the relationships of the arterial trunks. Three main groups stand out: intertwining arterial trunks and "normally related" arterial valves, and parallel trunks, but with the aortic valve to the right side or left side. These groupings give information concerning the site of the ventricular septal defect, which in any group may be perimembranous, muscular or be doubly committed and subarterial. Infundibular morphology is also variable, and the proximity of the arterial valves to the roof of the defect is largely determined by the extent of the ventriculo-infundibular fold.

Heart Defects, Congenital↗
PubMed1983

Correlation of preoperative pulmonary function testing with clinical course in patients after pneumonectomy.

Postoperative morbidity and mortality were correlated with the preoperative results of three widely used tests of pulmonary function in 90 patients who underwent pneumonectomy for carcinoma of the lung. Factors analyzed following operation included thirty-day mortality, the incidence of arrhythmias, the frequency of respiratory complications, and the number of individuals requiring prolonged mechanical ventilation. Fourteen patients had a forced vital capacity (FVC) of 70% or less of predicted normal value. Eleven had a one-second forced expiratory volume (FEV1) of 1.5 liters or less, and 32 had an FEV1 of less than 2 liters. Twenty-six had an FEV1/FVC ratio of 0.6 or less. There were no differences in morbidity or mortality between these individuals and the patients whose test scores exceeded these criteria. As a general rule, decisions regarding operability and extent of resection cannot be made solely on the basis of the three spirometry tests reviewed.

Adolescent↗
PubMed1983

The transmitral approach to left ventricular outflow tract obstruction.

Left ventricular outflow tract obstruction is a particularly vexing problem in patients with complete transposition (atrioventricular concordance and ventriculoarterial discordance) and intact ventricular septum. Previous techniques, such as resecting the obstructive lesion through the pulmonary valve or bypassing the obstruction, have not given entirely satisfactory results. An alternative approach of resection through the left atrium and the retracted mitral valve has recently been proposed. We have used this new technique to achieve excellent relief of this condition in three patients with different types of obstruction.

Cardiomyopathy, Hypertrophic↗
PubMed1983

Interrupted aortic arch--anatomical features of surgical significance.

Analysis of 26 autopsy specimens with interruption of the aortic arch has led to a clearer understanding of the vital importance of associated cardiovascular abnormalities. In all cases there was an associated patent ductus arteriosus "supporting" the distal systemic circulation. "Proximal" septal defects, 22 ventricular septal defects and 3 aorto-pulmonary windows, were found in all but one specimen. The infundibular component of the ventricular septum was displaced posteriorly and leftward in 9 hearts resulting in significant left ventricular outflow obstruction in 8. In one specimen the infundibular septum was displaced anteriorly giving the effect of a "Fallot type" obstruction to the right ventricular outflow tract. Abnormal ventriculo-arterial connections were found in 7 hearts; 2 with discordant connection, 2 with double outlet, and 3 with single outlet of the heart. In 6 specimens there was an aberrant origin of the right subclavian from the distal aorta passing behind the esophagus to the right side. Various other arterial abnormalities were identified including a truncus arteriosus with separate but "transposed" origins of the pulmonary arteries. In short, in these hearts there were no examples of the rare situation where aortic arch interruption exists in isolation. This study therefore makes it very clear that a detailed understanding of associated anatomical abnormalities must accompany any attempt at surgical correction. Certainly in many of these cases management of the associated lesion will present more of a challenge than the difficult problem of dealing with the interrupted arch itself.

Abnormalities, Multiple↗
PubMed1983

Clinical experience with the Hall pivoting disk valve.

One hundred seventy-two patients have had Medtronic-Hall pivoting disk valves implanted at the University of North Carolina since April, 1978 as a primary procedure or in combination with other cardiac surgery. One hundred twenty-three patients (31 combined) had aortic valves implanted, 32 patients (3 combined) had mitral valves implanted, and 17 patients (7 combined) had aortic and mitral valves implanted. The actuarial survival at 4 1/2 years, excluding the operative mortality, is 100% for all patients with mitral valve replacement and 91% for all patients with aortic valve replacement. The actuarial survival at 2 1/2 years for all patients with aortic and mitral valves replaced is 88%. None of the patients had clinical evidence of hemolysis. The average LDH value was 531 +/- 240 IU/L. Eighty percent of the surviving patients were totally asymptomatic, 19% were symptomatic with moderate exertion, and only 1% were unchanged or worse. Four cerebrovascular accidents occurred in this group of patients for a 1.1/100 patient years incidence of cerebrovascular accidents in the aortic group and a 3.8/100 patient years incidence in the mitral group. Two of the mitral valves were replaced because of thrombosis and one aortic valve was found to be thrombosed at autopsy in a late death for an incidence of 0.6/100 patient years in the aortic group and 3.8/100 patient years in the mitral group. Hemodynamic measurements performed intraoperatively showed that only the smallest valve size, #21, was somewhat stenotic, with the average valve area being 1.3 cm2 for that size. There were no structural valve failures observed in this group of patients.

Aortic Valve↗
PubMed1983

Identification of internal carotid artery stenosis in coronary artery bypass candidates.

Identification of stenotic internal carotid arteries in neurologically asymptomatic coronary artery bypass candidates is difficult. We correlated carotid arteriograms with carotid bruits in 422 vessels and demonstrated a sensitivity of 79% and a specificity of 65% with regard to the bruit's identification of vessels with a 50% or more reduction in angiographic diameter. The noninvasive duplex scan, used in conjunction with Fast Fourier Transform spectral analysis, had a sensitivity and a specificity of 90% in this same regard. Since there is only a 6% incidence of significant internal carotid stenosis in bypass candidates, Bayes' theorem used in conjunction with our findings showed that a carotid bruit was an incorrect predictor of internal carotid stenosis 87% of the time. The duplex scan was somewhat better, but still inaccurate 64% of the time. Thus neither parameter alone has a high enough predictive value to determine whether preoperative carotid angiography is necessary. However, if one limits duplex scanning to patients with a carotid bruit, the predictive value is raised to 92%. At the same time, there is minimal increase in the number of undiagnosed patients. Thus far this combined approach is recommended for preoperative evaluation of patients scheduled for coronary artery bypass.

Angiography↗
PubMed1983

A removable extraluminal Doppler probe for continuous monitoring of changes in cardiac output.

To address the problem of monitoring cardiac output in postoperative cardiac patients, a removable, extraluminal pulsed Doppler probe has been constructed which continuously reflects changes in cardiac output by monitoring blood velocity in the ascending aorta. Velocity is related to the frequency of the Doppler shift and the angle at which the ultrasound beam intersects the vessel. A 1 mm2 piezoelectric crystal mounted at a 45 degree angle on the tip of the probe is activated with a 20-MHz range-gated pulsed Doppler, and velocity is determined from Fourier analysis of quadrature data using computer software with a 50-KHz processing range. The device is designed for application to the ascending aorta at the conclusion of a cardiac surgical procedure; and, since mean diameter changes in the ascending aorta have been shown to be very small over a wide range of mean aortic pressures, cardiac output is linearly related to velocity. To test this technique, simultaneous recordings were made from the pulsed Doppler probe and an electromagnetic flow probe in five mongrel dogs over a range of cardiac outputs from 0.5 to 6 l/min for a total of 136 data points. Excellent correlation was found between the electromagnetic flow probe and pulsed Doppler probe data (average r = .98 +/- .006). Average slope between the two was 1.004 and average zero intercept was -0.025 l/min. The catheter is small, stable, has no baseline drift, and continuously and accurately reflects pulsatile changes at high and low flows.

Animals↗
PubMed1983

Effects of pneumonectomy on pulmonary input impedance.

The long-term effects of pneumonectomy on the pulmonary circulation quantifiable through pulmonary input impedance analysis were studied. Excision of the left lung was performed in purebred beagle dogs aged 6 to 10 weeks (n = 6 group I) or 1 year (n = 8 group II). Unoperated beagles served as controls (n = 8 group III). When the dogs were 5 years of age, pulmonary pressure and flow were measured and the impedance spectra calculated. Characteristic impedance (Zo) (indicative of changes in proximal vessel physical properties) and pulmonary vascular resistance (PVR) (indicative of the distal response) were estimated. In group III the cardiac output (CO) was 1.7 +/- 0.4 L/min, mean pressure 16 +/- 5 mm Hg, PVR 605 +/- 448 dyne-sec/cm, and Zo 204 +/- 76 dyne-sec/cm. Group I results exhibited bimodal distributions that were not statistically different from results of groups II or III; four dogs had spectra comparable to those of group III, while two dogs had developed moderate hypertension and high PVR and Zo. Group II results were more normally distributed, and comparison with group III indicated statistically significant differences (P less than 0.05) in CO (1.1 +/- 2 L/min), PVR (1396 +/- 573 dynes-sec/cm), and Zo (543 +/- 273 dynes-sec/cm). Doubling of PVR and Zo in group II indicated that proximal vessel compliance and peripheral perfusion radius had not increased following pneumonectomy in adult beagles. Group I results indicate that marked facilitory adaptation can occur when pneumonectomy is performed in puppies; however, the adaptation may not be based on true lung growth and, therefore, may not be sustained indefinitely.

Adaptation, Physiological↗
PubMed1982

Bronchial carcinoma and the lymphatic sump: the importance of bronchoscopic findings.

The lymphatic sump of Borrie is an important area of regional node metastasis in each lung. The sump area is of increased importance on the right side, since bilobectomy has been recommended to ensure complete removal of lymphatic disease in patients with lower or middle lobe carcinoma. The role of bronchoscopy in assessing lymphatic metastasis of bronchial carcinoma was investigated in 42 patients at the North Carolina Memorial Hospital. Because of the high incidence of associated lymphatic metastases, bilobectomy is indicated for right lower or middle lobe lesions observed at bronchoscopy. Simple lobectomy may be utilized when bronchoscopic findings are negative and when there is no involvement of the lymph nodes of the sump of Borrie at the time of operation. If there is gross nodal involvement of the lymphatic sump, pneumonectomy will be required.

Bronchoscopy↗
PubMed1982

Structural changes in the canine lung and pulmonary arteries after pneumonectomy.

The study set out to describe the structural changes in the remaining lung of beagle dogs after left-sided pneumonectomy, performed at 6-10 wk or 1 yr of age. After a 5-yr postoperative recovery, lung volume and weight had increased in the operated groups, though only the latter was significant in comparison with 5-yr-old controls. In both operated groups, total alveolar number in the right lung was normal. The total volume of alveolar ducts, mean linear intercept, and (in the young operated group) mean alveolar volume were increased, indicating a compensatory enlargement of distal air spaces. Lobar differences reinforced these conclusions. In the 1-yr operated group, medial hypertrophy was present in preacinar arteries, with a similar trend in intra-acinar arteries where peripheral extension of medial smooth muscle was also present. Despite the lack of structural change in their pulmonary arterial system, the young operated group had right ventricular hypertrophy. Previously reported evidence of alveolar proliferation shortly after pneumonectomy probably represents a speeding up of normal developmental patterns, but after prolonged recovery the final alveolar number is no greater than normal.

Animals↗
PubMed1981

Forced oscillatory resistance and compliance parameters following pneumonectomy in beagle dogs.

Forced oscillatory resistance (RFO) and compliance (CFO) were measured in 3 groups of adult beagle dogs. Group I (n = 12) had undergone a left pneumonectomy at 6-10 weeks of age; group II (n = 11) underwent a similar procedure at 1 year of age; and group III (n = 8) served as unoperated controls. The mean value of RFO for group II was significantly higher than corresponding values for groups I and III. Similarly, the mean value of CFO was significantly lower for group II. Mean values for RFO and CFO between groups I and III were not statistically different. When RFO and CFO were normalized by functional residual capacity, mean values for all three groups were similar. However, when RFO and CFO were normalized by body weight, mean values for groups I and II were significantly different from those of group III. These findings cannot be explained directly by postoperative hyperinflation of the remaining lung. They suggest that there is an adaptive change in the mechanical characteristics of the remaining lung following pneumonectomy and that the degree of adaptation varies with the age of the animal undergoing resection.

Adaptation, Physiological↗
PubMed1981

Surgical anatomy of double-outlet right ventricle with situs solitus and atrioventricular concordance.

Sixty-three hearts with situs solitus, concordant atrioventricular connection, and more than half of both great arteries connected to the right ventricle have been studied to delineate their surgically important features. Specifically noted were the relationship of the arterial valves to each other and the type and position of the ventricular septal defect with special reference to the conduction tissue location. Infundibular morphology was ascertained and other congenital abnormalities were recorded. An estimate was made of the surgical options available given the various anatomic abnormalities present. The aorta was most commonly in the right posterior position but could be found anywhere in the arc extending to left anterior position. The septal defects were most frequently in subaortic position (34/65) and were usually of perimembranous type (45/65). Three hearts had two defects each and one heart had an intact ventricular septum. Identifying the type of defect was helpful in locating the conduction tissues. In addition, there were numerous associated anomalies, including 19 hearts with coronary artery malformations. Retrospective analysis of the surgical options suggested that 36% of the hearts would not have been operable during life. Approximately another third could have been corrected by use of an intraventricular tunnel from the ventricular septal defect to the aorta, and the remaining third would have needed more complex procedures. In the final analysis it was concluded that hearts with the ventriculoarterial connection of double-outlet right ventricle, though so varied as to preclude "standardization," did permit anatomic analysis and description in clear and consistent terms.

Coronary Vessels↗