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R S Downey

Publications and source records attributed to R S Downey.

At least 19 recordsLinked to original sources
PubMed1992

Effect of an oxygen-enriched solution and multiple dosing of antegrade crystalloid cardioplegic solution on myocardial metabolism during coronary artery bypass graft operations.

The metabolic effect of excessive oxygenation and frequency of administration of antegrade crystalloid cardioplegic solution was assessed in 33 patients undergoing routine coronary artery bypass graft operations. Four patient groups were designed in which the initial aortic root injection was 1000 ml and then 100 ml administered through the vein grafts after completion of each distal anastomosis. The groups were divided as follows: group 1, single dose, normally oxygenated cardioplegic solution infused via the aortic root; group 2, single dose, high oxygen content cardioplegic solution infused via the aortic root; group 3, normally oxygenated cardioplegic solution with additional 250 ml doses via the aortic root every 20 minutes; group 4, high oxygen content cardioplegic solution with additional 250 ml doses via the aortic root every 20 minutes. In all groups myocardial mean septal temperature showed an immediate fall to approximately 11 degrees C with the initial aortic root doses and then a gradual rewarming to approximately 20 degrees C during the crossclamp period (mean 58.6 minutes). Metabolic parameters measured or calculated from the coronary sinus effluent were myocardial oxygen extraction, lactate production, base deficit, inorganic phosphate, glucose, potassium, creatine kinase (total and myocardial band fraction), and catecholamine production. There was no statistically significant difference in any of these determinations between each patient group. Furthermore, myocardial recovery, myocardial performance, and postoperative recovery characteristics were not different. We conclude that single or multidose aortic root crystalloid cardioplegic solution (either oxygen enriched or normally oxygenated) is equally effective in routine coronary artery bypass graft operations when septal temperatures are maintained between 15 degrees and 21 degrees C for a total arrest time of 60 minutes or less. In this study, increasing the volume cardioplegic solution given in multiple doses appeared to offer no significant metabolic or functional advantage in patients without complications who had satisfactory left ventricular function.

Cardioplegic Solutions↗
PubMed1990

Major retroperitoneal venous anomalies: surgical considerations.

Nineteen major anomalies of the vena cava or its branches were encountered in patients requiring abdominal vascular surgery and related procedures at Barnes Hospital during the past 5 years. The classification of these anomalies, their embryologic development, associated variants, and surgical considerations are discussed. Careful review of preoperative computed tomographic scans and familiarity with these anatomic variants may allow the surgeon effectively to avoid potentially disastrous intraoperative consequences.

Humans↗
PubMed1989

Use of multiple 13C-labeling strategies and 13C NMR to detect low levels of exogenous metabolites in the presence of large endogenous pools: measurement of glucose turnover in a human subject.

A significant problem which may be encountered in 13C NMR studies of metabolism is the contribution that background levels of 13C may make to the observed spectra when low or tracer levels of the 13C label are used. We propose that the introduction of two or more labeled sites in the same tracer molecule is an effective strategy for eliminating or reducing this difficulty and demonstrate its feasibility in an isotope dilution study of glucose turnover in a human volunteer. This approach has two significant advantages over the more common use of a singly enriched labeling strategy: (i) as a consequence of the scalar coupling interactions, multiple-labeled metabolites will yield spectra distinct from those containing natural abundance 13C, and (ii) at a 99% level of enrichment for the precursor, concentration levels which are approximately 1% of the endogenous pools can be detected with approximately equal sensitivity. As a demonstration of this strategy, glucose production in a human subject was determined by continuous infusion of tracer levels of [U-13C6]glucose over a 4-h period and subsequent analysis of plasma levels of the tracer in vitro by NMR. Mass spectroscopy was used on the same samples to provide a basis for comparison of the precision and accuracy of the NMR technique. The results demonstrate the feasibility of the multiply labeled approach for detection by NMR of tracer amounts of label in the presence of a much larger endogenous pool of glucose. The NMR and mass spectrometric data gave quantitatively identical results for the glucose production rate demonstrating that equivalent data may be obtained by both methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Large cell carcinoma of the lung: a highly aggressive tumor with dismal prognosis.

A retrospective review was made of 96 consecutive patients with large cell carcinoma of the lung admitted to Emory University Hospital over 10 years. Only 10 patients were seen with stage I lesions favorable for resection. The remainder were treated primarily with irradiation or chemotherapy. Mean survival for clinical stage I patients was 15.9 months; stage IIIA patients, 7.9 months; stage IIIB patients, 7.1 months; and stage IV patients, 5.8 months. Only 1 patient survived for 5 years. This distinct and highly aggressive form of lung cancer most commonly is seen at an advanced stage and is associated with an unusually dismal prognosis regardless of the method of treatment employed.

Carcinoma, Small Cell↗
PubMed1989

Esophageal carcinoma: surgery without preoperative adjuvant chemotherapy.

Our experience with 100 consecutive patients with esophageal carcinoma treated with surgical intervention as the primary method of therapy between 1967 and 1987 was reviewed. Preoperative chemotherapy was not administered by us. Follow-up was complete for all 100 patients. Twelve percent of tumors were in the proximal third of the esophagus, 21% were in the middle third, and 67% were in the distal third. Adenocarcinoma accounted for 44% of all tumors, squamous cell for 55%, and adenosquamous for 1%. Six patients were in stage I, 14 were in stage II, and 80 were in stage III; no patient was in stage IV. Surgical procedures included 85 esophagogastrectomies with primary anastomoses, 11 with colon interposition, and 4 with Roux-en-Y small-bowel interposition. Six patients had radical laryngopharyngo-esophagectomy with gastric or colopharyngeal anastomosis. Operative mortality was 3%. The mean survival of stage I patients was 182 months; stage II patients, 25 months; and stage III patients, 18 months. Our data show that surgical resection without preoperative adjuvant chemotherapy remains the cornerstone of therapy for patients with carcinoma of the esophagus.

Adenocarcinoma↗
PubMed1989

Managing the difficult pulmonary artery during completion pneumonectomy.

We describe two examples of successful management of a difficult PA. In the first, the posterior approach to the PA during completion pneumonectomy is demonstrated. In the second, the intrapericardial transection of the right PA is described when the tumor encroaches onto the right hilum. Maneuvers to ensure safe and continuous control of the PA have been previously described but never widely popularized or well illustrated.

Evaluation Studies as Topic↗
PubMed1987

Exenterative surgery for locally advanced rectosigmoid cancers. Is it worthwhile?

Among 1480 patients treated for cancers of the rectosigmoid over a 30-year period, 24 patients underwent total pelvic exenteration. These patients, 13 men and 11 women, had a median age of 64 years. Pathologic staging revealed 15 Dukes' B and nine Dukes' C lesions. For 17 patients, this operation was the only form of therapy. The operative mortality rate was 20.8%; however, the mortality rate has decreased to 13.3% during the past 20 years and to 9% in the past decade. Five complications occurred in the group surviving the procedure, resulting in a 26.3% morbidity rate. Three of the five complications occurred in patients who had previous radiation therapy or surgery. The overall 5-year survival rate was 41.6%. Those patients surviving the operation had 5- and 10-year survival rates of 52.6% and 31.5%, respectively. There were seven patients in whom the disease recurred at an average of 20.3 months after exenteration, and all died an average of 8 months later. The recurrence rate for patients with Dukes' B lesions was 27% compared with 57% for patients with Dukes' C lesions. The remaining 12 disease-free patients had a mean survival of 11 years. At present, four patients are alive and well 6 to 30 years after exenteration. The best predictor of morbidity was treatment before exenteration (p less than .005). Age older than 65 years and the presence of nodal metastases may contribute to increased mortality rates and recurrence, respectively, but these relationships were not statistically significant for the group. Total pelvic exenteration is advocated for selected primary, locally advanced, rectosigmoid lesions in good-risk patients; it can be achieved now with acceptable morbidity and mortality rates and a survival rate in excess of 40% at 5 years.

Aged↗
PubMed1986

Effect of tracer infusion site on measurement of bicarbonate-carbon dioxide metabolism in dogs.

Ten dogs were given a primed infusion of H13CO3- for 220 min while under general anesthesia. Isotopic steady state was reached within 60 min in exhaled CO2, femoral arterial blood HCO3-, and femoral venous blood HCO3-. Halfway through each infusion study, the site of tracer infusion was changed either from the central aorta to a peripheral vein, or vice versa. The mean HCO3(-)-CO2 flux measured from blood HCO3- enrichments was 15.7 +/- 2.1 (SD) mmol X kg-1 X h-1. The mean fraction of tracer recovered in exhaled CO2 was 79 +/- 7% (SD) of the infused dose. No significant difference in either HCO3- flux or recovery of tracer was found between the venous and arterial infusions of tracer. These results indicate that when venous administration of HCO3- tracer is compared with central arterial infusion, the initial loss of tracer into expired CO2 is an unimportant consideration in experiments measuring HCO3- kinetics.

Animals↗
PubMed1986

Benign extrinsic compression of the common bile duct: a case report.

Painless obstructive jaundice is usually the result of malignant compression of the distal common bile duct. Infrequently extrinsic benign lesions may also cause ductal obstruction and be mistaken for a malignant process. A case of compression of the distal common bile duct is described. Preoperative evaluation was most consistent with a cystadenocarcinoma of the head of the pancreas. At operation we found an enlarged and calcified periductal lymph node with associated fibrosis and compression and obstruction of the distal common duct. Massive dilatation of the distal common duct and the cystic duct remnant gave it the appearance of a cystic mass in the superior border of the head of the pancreas. Resection and choledochoduodenostomy were curative.

Aged↗
PubMed1986

Protein dynamics in skeletal muscle after trauma: local and systemic effects.

Injury is attended by accelerated skeletal muscle proteolysis. Accurate definition of this hypercatabolic response and its mediation is requisite for specific therapy. We measured protein dynamics in the incubated and intact epitrochlearis and soleus muscles excised from both forelimbs and both hindlimbs of rats 4 days after injury by either a single hind limb scald (90 degrees C water for 3 seconds; metabolic rate (MR) + 15%, urinary urea nitrogen (UUN) + 10%) or a 5% excision (dorsal skin removed to fascia; MR + 40%, UUN + 90%). Protein synthesis (3H phenylalanine incorporation) increased only in the injured soleus from the scalded hind limb (+100%). Actin and myosin breakdown (3-methylhistidine release) increased in all muscles tested and was consistently larger in epitrochlearis than in soleus muscles. Breakdown of the mixed protein pool (tyrosine release) increased but less so than 3-methylhistidine and did not reach significance in the uninjured soleus muscle of scalded rats. With respect to fiber type, white fiber epitrochlearis muscle demonstrated a more pronounced elevation of both measures of breakdown but at a lower metabolic rate than did red fiber soleus muscle. Increasing MR was associated with a linear increase in soleus proteolysis but no further change in epitrochlearis breakdown. We conclude that protein breakdown is increased in skeletal muscle distant from injury; however, even when metabolic stress is severe, synthesis is unchanged. Muscles of different fiber composition are not equally labile. Furthermore, myofibrillar protein is more labile than the mixed protein pool.

Actins↗
PubMed1984

Measurement of urea kinetics in humans: a validation of stable isotope tracer methods.

To define the importance of an accurate priming dose for measurement of urea production using a primed, short-duration (e.g., 4 h) infusion of labeled urea, [18O]- and [13C]ureas were infused simultaneously at two different prime-to-infusion (P/I) doses into five young adult men. The measured mean (+/-SE) urea production rates were 261 +/- 12 and 509 +/- 25 mumol X kg-1 X h-1 for P/I = 12.6-h and 5.0-h priming doses, respectively. In a second series of studies, a single dose of [18O]urea tracer was administered intravenously to four subjects, and the urea production rate was determined from the plasma urea tracer disappearance curve obtained over the following 6 h by fitting the data to a two-exponent curve. The mean urea production rate was 224 +/- 14 mumol X kg-1 X h-1. Because the fractional turnover of the body urea pool is slow, the priming dose strongly influences the "apparent" plasma urea enrichment plateau and, therefore, the measured urea production rate during short-duration infusions. Alternatively, the single-dose protocol can be applied to measure human urea production accurately in periods as short as 6 h.

Adult↗
PubMed1983

Echocardiographic assessment of cats anesthetized with xylazine-sodium pentobarbital.

Left ventricular echocardiographic parameters in cats were recorded, measured and analyzed to study the effects of a combination of xylazine and sodium pentobarbital on left ventricular function. The depressant effects of a combination of xylazine and sodium pentobarbital on the left ventricular dimension at end diastole, the percent change in minor diameter and the velocity of circumferential fibre shortening were compared to echocardiographic values of unanesthetized cats. No change in heart rate was noted. Stroke volume and cardiac output were depressed.

Anesthesia, Intravenous↗