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Biomedical subjects

C L Nelson

Publications and source records attributed to C L Nelson.

At least 19 recordsLinked to original sources
PubMed1992

Dietary fat and postmenopausal breast cancer.

BACKGROUND: Although the results of animal studies and cross-cultural comparisons generally support a role for dietary fat in the etiology of breast cancer, results of analytic epidemiology studies are equivocal. PURPOSE: The association between dietary fat and subsequent breast cancer was examined in a cohort of 34,388 postmenopausal women from Iowa. METHODS: Dietary habits were assessed by a food-frequency questionnaire mailed in January 1986. Through December 31, 1989, 459 incident cases of breast cancer occurred in this cohort. Proportional hazards regression was used to examine the dietary fat-breast cancer association while adjusting for potential confounders. The effects on this association of four analytic approaches to adjustment for energy intake were also considered. RESULTS: After adjustment for known determinants of breast cancer, a modest positive association of total fat intake with risk of breast cancer was seen. Polyunsaturated fat intake was also positively associated with breast cancer (relative risk from lowest to highest intake, 1.0, 1.25, 1.31, and 1.49; P for trend = .052). Different approaches to adjustment for energy intake, however, provided different impressions of the dietary fat-breast cancer association. One method, involving categorization of crude fat intake and inclusion of total energy intake in regression analysis, gave relative risk estimates from low to high fat intake of 1.0, 1.17, 1.25, and 1.38 (P for trend = .18). Another method, based on categorization of fat intake residuals in which the variation in fat due to total energy intake was removed, gave corresponding estimates of 1.0, 1.24, 1.30, and 1.16 (P for trend = .29). The former suggests increasing breast cancer risk with increasing fat intake; the latter suggests no association. CONCLUSIONS: These results are consistent with other cohort studies that have shown a weak association or no association between dietary fat and breast cancer. They are also consistent with studies suggesting that fat intake is a determinant of breast cancer, particularly after accounting for inaccuracies in dietary assessment. The effects of different energy-adjustment methods may account in part for the varying interpretations of four previous cohort studies of dietary fat and breast cancer. IMPLICATIONS: Further work is needed to clarify not only the nature of the dietary fat-breast cancer association, but also the impact of different analytic methods used in the investigation of diet-disease associations.

Aged↗
PubMed1992

Outcome of patients sustaining acute ischemic mitral regurgitation during myocardial infarction.

OBJECTIVE: To describe outcomes of patients sustaining an acute myocardial infarction complicated by mitral regurgitation managed with contemporary reperfusion therapies. DESIGN: Inception cohort case study. Long-term follow-up was obtained in 99% of all patients. SETTING: University referral center. PATIENTS: A series of 1,480 consecutive patients presenting between April 1986 and March 1989 who had emergency cardiac catheterization within 6 hours of infarction. Fifty patients were found to have moderately severe or severe mitral regurgitation. OUTCOME MEASURES: Mortality; follow-up cardiac catheterization in patients with regurgitation. RESULTS: Acute ischemic moderately severe to severe (3+ or 4+) mitral regurgitation was associated with a mortality of 24% at 30 days (95% CI, 12% to 36%), 42% at 6 months (CI, 28% to 56%), and 52% at 1 year (CI, 38% to 66%); multivariable analysis identified 3+ or 4+ mitral regurgitation as a possible independent predictor of mortality (P = 0.06). Patients with mitral regurgitation tended to be female, older, and to have cerebrovascular disease, diabetes, and preexisting symptomatic coronary artery disease. A physical examination did not identify 50% of patients with moderately severe to severe regurgitation. Acute reperfusion with thrombolysis or angioplasty did not reliably reverse valvular incompetence. In this observational study, the greatest in-hospital and 1-year mortalities were seen in patients reperfused with emergency balloon angioplasty, whereas patients managed medically or with coronary bypass surgery had lower mortalities. CONCLUSIONS: Moderately severe to severe (3+ or 4+) mitral regurgitation complicating acute myocardial infarction portends a grave prognosis. Acute reperfusion does not reduce mortality to levels experienced by patients with lesser degrees of mitral regurgitation nor does it reliably restore valvular competence.

Acute Disease↗
PubMed1992

Effect of family history, body-fat distribution, and reproductive factors on the risk of postmenopausal breast cancer.

BACKGROUND: A family history of breast cancer reflects shared cultural factors, genetic predisposition, or both. There is evidence that the estimated risk associated with a family history of breast cancer increases multiplicatively in combination with other risk factors. We examined the combined effect of family history and anthropometric and reproductive factors on the risk of breast cancer in postmenopausal women. METHODS: Using data from a prospective cohort study, we studied 37,105 women 55 to 69 years of age to determine whether known risk factors for breast cancer are modified by a reported family history at the time of entry into the study. RESULTS: During the first 4 years of follow-up, 493 new breast cancers were diagnosed. The association of the waist-to-hip ratio (the circumference of the waist divided by that of the hips) with the risk of breast cancer was limited predominantly to women with a family history of breast cancer; the age-adjusted relative risk of breast cancer for the women above the fourth quintile for waist-to-hip ratio as compared with those below the first quintile was 3.2 in women with a family history of breast cancer and 1.2 for women without such a family history. An interaction was observed between a family history of breast cancer and the number of live-born children; the protective effect of higher parity was observed primarily among women with a family history of breast cancer. Similarly, the age-adjusted relative risk of breast cancer associated with a late age at first pregnancy (i.e., greater than or equal to 30 years) was 5.8 for women with a family history of breast cancer and 2.0 for women without such a family history. CONCLUSIONS: The increase in the risk of breast cancer associated with a high waist-to-hip ratio, low parity, or greater age at first pregnancy is more pronounced among women with a family history of breast cancer. These findings suggest etiologic differences between familial breast cancer and the sporadic form.

Adipose Tissue↗
PubMed1992

Ergonovine maleate testing during cardiac catheterization: a 10-year perspective in 3,447 patients without significant coronary artery disease or Prinzmetal's variant angina.

The utility of ergonovine testing for coronary artery spasm was assessed in 3,447 patients with angiographically insignificant (less than 50% diameter stenosis) or no coronary artery disease. No patients clinically had Prinzmetal's variant angina. Overall, 4% had a positive ergonovine test result, defined by spasm causing greater than or equal to 75% focal stenosis. Complications related to ergonovine use occurred in 11 patients (0.03%). In a training sample of 1,136 patients (studied between 1980 and 1984), two independent predictors of spasm were found by using multivariate analysis: the amount of visible coronary artery disease on the coronary angiogram (p less than 0.0001) and a smoking history (p = 0.001). A model to predict spasm based on these variables was validated in a test group of 2,311 patients who received ergonovine from 1985 to 1989. This model allowed the identification of a subset of 400 patients in the validation sample who had a 10% positive test rate compared with a 2% positive test rate in the remaining patients. These results should permit clinicians who use provocative testing in the catheterization laboratory to reserve testing for the subset of this group of patients most likely to have abnormal findings.

Angina Pectoris, Variant↗
PubMed1992

Control of contamination of the operative team in total joint arthroplasty.

Reports of percutaneous transmission of blood-borne disease emphasize the need for control of intraoperative contamination. In a randomized prospective study, surgeons and surgical assistants involved in total hip and total knee arthroplasty adopted the following protocol: total body exhaust with hood, aspirator, knee-length impermeable gowns, foot covers, including knee-high covers and waterproof covers, and one of three combinations of gloving protocols: latex/latex changed hourly, latex/cloth, or latex/cloth/latex. All inner gloves were tested by a leak test. All needles and sharp instruments were passed on trays, and all contaminations and perforations were recorded. Each surgeon and assistant was inspected twice for contamination. There were no needle sticks, and only one of 267 personnel had head, neck, body, leg, or foot contamination. Perforation rates of inner gloves were 9.2% for latex/latex, 7.9% for latex/cloth, and 4.3% for latex/cloth/latex.

Blood↗
PubMed1992

Vena caval filter use in orthopaedic trauma patients with recognized preoperative venous thromboembolic disease.

This study comprises a series of 35 patients with pelvic or lower extremity fractures requiring surgery who also had a documented significant acute deep venous thrombosis (DVT). The authors treated these with low-dose Coumadin and 36 vena caval filters, which were used prophylactically prior to surgery. The patients received low-dose warfarin after placement of the vena caval filters and were maintained at 1.3-1.5 times the prothrombin control value for 6 weeks to 3 months. In this group of patients, there were no fatal pulmonary emboli and no clinically significant complications from filter placement. There were nine asymptomatic filter complications demonstrated radiographically in eight patients. Additionally, one patient with a tilted vena caval filter required placement of another filter. The combination of vena caval filters and low-dose warfarin appears to be a successful and relatively safe method of managing those patients who have acute DVT and require surgery for their pelvic or lower extremity fractures.

Combined Modality Therapy↗
PubMed1992

In vitro elution characteristics of commercially and noncommercially prepared antibiotic PMMA beads.

The successful treatment of osteomyelitis with commercially prepared gentamicin-polymethylmethacrylate (PMMA) (Septopal) beads and surgical debridement has led to the use of this technique in the United States. However, commercially prepared gentamicin-PMMA beads are not currently available to orthopedic surgeons in the United States. Therefore, these surgeons commonly manufacture their own antibiotic-containing cement beads in the operating room at the time of surgery. There is little data that compare the antibiotic elution characteristics of such preparations to commercially prepared gentamicin-PMMA beads. This study compares the measured amount of antibiotic elution of either gentamicin or tobramycin from laboratory manufactured Zimmer, Simplex, or Palacos beads to commercially prepared gentamicin-PMMA (Septopal) beads. During a 30-day study period, commercially prepared gentamicin-PMMA beads eluted more total antibiotic and maintain higher concentrations than did antibiotic acrylic composites manufactured in the authors' laboratory.

Bacteroides↗
PubMed1992

Is anticoagulation indicated for asymptomatic postoperative calf vein thrombosis?

The purpose of this study was to determine the effect of anticoagulation on the incidence of thrombotic propagation and pulmonary embolism in patients with calf vein thrombosis after total hip or total knee arthroplasty. Patients undergoing arthroplasties had prospective surveillance for postoperative deep vein thrombosis by both bilateral contrast venography and venous duplex scanning. Calf vein thrombosis was documented by venography in 42 patients (50 limbs), including 29 of 253 patients undergoing total hip arthroplasty (11.4%) and 13 of 99 patients undergoing total knee arthroplasty (13%). Of patients on whom follow-up duplex scans were performed, heparin followed by warfarin anticoagulation was used in 11 (13 limbs) and withheld in 21 (25 limbs). Propagation of thrombosis to the popliteal or superficial femoral vein or both was detected by serial duplex scanning in 3 of 13 treated limbs (23%) and 2 of 25 untreated limbs (8%), (p = 0.43). All thrombus propagations were detected within 2 weeks of the operative procedure. There were no pulmonary emboli or deaths. Propagation of asymptomatic calf vein thrombosis after arthroplasty was not influenced by anticoagulation, suggesting that postoperative calf vein thrombosis need not be routinely treated. Serial venous duplex scanning is useful to identify the occasional patient in whom thrombotic propagation requiring anticoagulation develops.

Aged↗
PubMed1990

The preoperative prevalence and postoperative incidence of thromboembolism in patients with hip fractures treated with dextran prophylaxis.

A prospective preoperative and postoperative venographic study of hip fracture patients has documented a significant preoperative prevalence and postoperative incidence of thromboembolic disease. A statistically higher incidence of deep-venous thrombosis is observed in patients with femoral neck fractures compared to patients with intertrochanteric fractures. A 9% (15 of 176) preoperative prevalence and an 11% (12 of 108) incidence of new postoperative thromboembolic disease were detected. There was a predilection for deep-venous thrombosis in the injured extremity compared to the noninjured extremity both preoperatively and postoperatively.

Adult↗
PubMed1979

Environmental bacteriology in the unidirectional (horizontal) operating room.

The continuing attempts to reduce bacterial contamination through clean air systems have been of special interest to surgeons dealing in joint replacement surgery. Although the definitive relationship between airborne contamination and surgical infections is not universally agreed on, there is little question that clean air systems reduce bacterial contamination of the surgical wound at the time of operation. This report reviews the history of surgical infections, presents statistical data that show the reduction of bacterial contamination by a clear air system, and suggests a pragmatic attitude regarding airborne bacterial contamination of surgical wounds.

Air↗
PubMed1979

Experimental reaming of the proximal femur and acrylic cement implantation: vascular and histologic effects.

The technique of microangiography and correlated histology was used, in experiments on the proximal femora of mature mongrel dogs, to study the effects of simple medullary reaming and of reaming followed by insertion of acrylic cement. The hip joints were not disturbed. A segment of Steinmann pin, representing the stem of a hip prosthesis, was inserted into the cement as it was polymerizing. The most significant results, after reaming alone, were devascularization and apparent necrosis of large areas of the cortex of the subtrochanteric femoral diaphysis. Full recovery was observed in 6 months. However, when acrylic cement was introduced following the reaming, extensive necrosis of the inner layers of the diaphyseal cortex was still present after a year, when the observations were terminated. The presence of necrosis of bone was judged by the lack of visible osteocytes in the lacunae. After the devascularization caused by filling the diaphyseal medulla with acrylic cement, the apparently necrotic cortex was revitalized without osteoclasia. That is in contrast to the results in another study in which osteoclasia and osteoneogenesis were required to restore cortex with empty cell lacunae. This raises the question of dormant osteonecrosis in contrast to total osteonecrosis. These studies show, in thin histologic preparations, acrylic bone cement in situ in the tissues. A fibrous membrane was found at the cement-bone interface in most areas. It was thicker in the diaphysis than in the metaphysis. The physiologic effects of acrylic cement implantation are considered to be likely factors in the loosening which is observed clinically when the femoral components of hip prostheses are under protracted stress.

Acrylic Resins↗
PubMed1978

Concentration of antibiotics in normal bone after intravenous injection.

The concentrations in serum, cancellous bone, and cortical bone of three antibiotics--nafcillin, cefazolin, and gentamicin--were measured in eleven normal dogs. All antibiotics rapidly penetrated into bone. The peak concentration in serum was reached within twenty minutes of intravenous injections, and the concentration in bone generally paralleled that in serum. Cancellous bone had higher concentrations than did cortical bone because of the admixture of blood.

Animals↗
PubMed1977

Current status of total knee replacement.

Correction of deformity and relief of pain in advanced arthritis of the knee joint can be obtained by implantation of a total knee prosthesis. For the painful, mildly damaged knee, the Charnley prosthesis may be used, while in the more moderately damaged knee, the geometric prosthesis may be indicated. For the unstable, severely damaged knee, a constrained prosthesis may be implanted. These knee prostheses can be used to treat knees which previously were not amenable to surgical correction, except by arthrodesis.

Humans↗
PubMed1977

Supracondylar fractures of the humerus: the role of dynamic factors in prevention of deformity.

In a retrospective survey of eighty-two children with supracondylar fractures of the humerus, forty were found to have sufficient clinical and roentgenographic data to classify the fractures as varus or valgus, and to determine the carrying angles at end result. The initial displacement (varus or valgus) of the distal fragment correlated with the final carrying angle, but the use of internal fixation, the adequacy of reduction achieved and the duration of traction or immobilization did not. The sixteen varus supracondylar fractures immobilized with the forearm in supination had a mean varus deformity of about 16 degrees, whereas the eight immobilized in pronation had a varus deformity of only 3 degrees. The findings in the few valgus fractures suggested that the valgus angulation was less at follow-up if they had been immobilized in supination. Dissection of eight cadaver limbs and electromyographic studies of one normal limb suggested that the position of the forearm affects the result by altering muscle tension.

Adolescent↗
PubMed1976

Mechanical strength of acrylic bone cements impregnated with antibiotics.

Admixing of several antibiotic powders which were insoluble in methyl methacrylate did not decrease the compressive and diametral tensile strengths of two acrylic bone cements when tested after setting for 1 day and after leaching 40 days in water at 37 degrees C. When antibiotics were added as water solutions, the included water resulted in a significant decrease in these bulk mechanical properties. Storage in water for 40 days caused surface irregularities only on specimens of the set antibiotic admixtures. Approximately 0.5% of the admixed dosage of these water-soluble antibiotics could be leached from the set cements. The observed surface channels, presumably left by the loss of antibiotic, suggest further study of surface-sensitive mechanical properties may be needed. The bulk mechanical strengths presented here are conclusive only for the particular combinations of antibiotics and cements investigated, and should not be generalized at this time to any or all antibiotic admixtures or other mechanical properties.

Anti-Bacterial Agents↗