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Biomedical subjects

B MacKinnon

Publications and source records attributed to B MacKinnon.

12 recordsLinked to original sources
PubMed2001

Prevention and treatment of postphlebitic syndrome: results of a 3-part study.

BACKGROUND: The true incidence of postphlebitic syndrome (PPS) following proximal deep venous thrombosis (DVT) and the efficacy of graduated compression stockings in preventing and treating PPS are unknown. METHODS: A 3-part study of 202 patients evaluated 1 year after proximal DVT: 2 randomized placebo-controlled trials of stockings and 1 prospective cohort of untreated patients. Patients were evaluated for PPS, using a standardized questionnaire, and for venous valvular incompetence, using photoplethysmography and venous Doppler. They were enrolled in study 1 or study 2 if they did not have symptomatic PPS and did not have or had venous valvular incompetence, respectively, and into study 3 if they had symptomatic PPS. Study 1 patients were left untreated and followed up for development of PPS every 6 months for a mean of 55 months. Study 2 patients were randomized to a below-knee stocking (20-30 mm Hg) or a matched placebo stocking, and followed up for development of PPS every 6 months for a mean of 57 months. Study 3 patients were randomized to an active stocking (30-40 mm Hg) or a matched placebo stocking and followed up every 3 months for treatment failure, defined a priori. RESULTS: In study 1, 6 (5.0%) of 120 patients were categorized as treatment failures, a rate similar to placebo-treated study 2 patients (P =.10). In study 2, 0 (0%) of 24 active and 1 (4.3%) of 23 placebo-treated patients were categorized as treatment failures (P =.49). In study 3, 11 (61.1%) of 18 active and 10 (58.8%) of 17 placebo-treated patients were categorized as treatment failures (P>.99). CONCLUSIONS: Most patients do not have PPS 1 year after proximal DVT, and do not require stockings. We failed to show a benefit of stockings in patients with PPS, but the small numbers preclude definitive conclusions.

Adolescent↗
PubMed2001

Repeated doses of porcine secretin in the treatment of autism: a randomized, placebo-controlled trial.

BACKGROUND AND OBJECTIVES: Anecdotal reports on the efficacy of secretin in autism raised great hopes for the treatment of children with this disorder. Initial single-dose, randomized, controlled trials failed to demonstrate any therapeutic effects of secretin. The present study is the first to test the outcome of repeated doses and to examine whether there is a subgroup of children who are more likely to achieve positive effects. METHOD: Sixty-four children with autism (ages 2-7 years; 55 boys and 9 girls) with a range of intelligence quotient and verbal ability were randomly assigned, in a double-blind manner, to secretin or placebo groups. Children received 2 doses of placebo or porcine secretin, 6 weeks apart. Assessments were performed at baseline and 3 weeks after each injection using several outcome measures. RESULTS: There were no group differences on formal measures of language, cognition, or autistic symptomatology. Subgroupings based on cognitive level, the presence or absence of diarrhea, or a history of regression failed to show any significant therapeutic effects of secretin. CONCLUSION: No evidence is provided for the efficacy of repeated doses of porcine secretin in the treatment of children with autism. The possible relationship between relief of biological symptoms and enhanced skill performance is discussed.

Analysis of Variance↗
PubMed2000

Postthrombotic syndrome after hip or knee arthroplasty: a cross-sectional study.

BACKGROUND: Although the incidence of the postthrombotic syndrome (PTS) has been addressed in patients with symptomatic deep vein thrombosis (DVT), less information is available on the incidence in patients who develop asymptomatic DVT after major hip or knee arthroplasty. OBJECTIVES: To determine whether symptomatic PTS occurs more frequently in patients who develop DVT after hip or knee arthroplasty than those who are free of DVT and to provide an estimate of the incidence of PTS in patients who had undergone major hip or knee arthroplasty and had proximal DVT, distal (calf) DVT, or no DVT. DESIGN AND SETTING: A cross-sectional study conducted at the Hamilton Health Sciences Corporation, Hamilton, Ontario, and the Academic Medical Centre, Amsterdam, the Netherlands. SUBJECTS AND METHODS: Two hundred fifty-five subjects who had undergone major hip or knee arthroplasty 2 to 7 years previously and had routine predischarge venography showing proximal DVT (n = 25), distal DVT (n = 66), or no DVT (n = 164) were enrolled from March 1993 through December 1998. The presence of symptomatic PTS confirmed by the presence of objectively confirmed venous valvular incompetence was ascertained. RESULTS: The rates of PTS were low and not significantly different among the 3 subgroups: 1 (4.0%, 95% confidence interval [CI] = 0.1%-20.4%) of 25 patients with proximal DVT, 4 (6.1%, 95% CI = 1.7%-14.8%) of 66 patients with distal DVT, and 7 (4.3%, 95% CI = 1.7%-8.6%) of 164 patients with no DVT. CONCLUSIONS: Symptomatic PTS is an uncommon complaint after major hip or knee arthroplasty. Patients who develop postoperative proximal or distal DVT and who receive 6 to 12 weeks of anticoagulant therapy are not predisposed to PTS.

Aged↗
PubMed1999

A comparison of three months of anticoagulation with extended anticoagulation for a first episode of idiopathic venous thromboembolism.

BACKGROUND: Patients who have a first episode of venous thromboembolism in the absence of known risk factors for thrombosis (idiopathic thrombosis) are often treated with anticoagulant therapy for three months. Such patients may benefit from longer treatment, however, because they appear to have an increased risk of recurrence after anticoagulant therapy is stopped. METHODS: In this double-blind study, we randomly assigned patients who had completed 3 months of anticoagulant therapy for a first episode of idiopathic venous thromboembolism to continue receiving warfarin, with the dose adjusted to achieve an international normalized ratio of 2.0 to 3.0, or to receive placebo for a further 24 months. Our goal was to determine the effects of extended anticoagulant therapy on rates of recurrent symptomatic venous thromboembolism and bleeding. RESULTS: A prespecified interim analysis of efficacy led to the early termination of the trial after 162 patients had been enrolled and followed for an average of 10 months. Of 83 patients assigned to continue to receive placebo, 17 had a recurrent episode of venous thromboembolism (27.4 percent per patient-year), as compared with 1 of 79 patients assigned to receive warfarin (1.3 percent per patient-year, P<0.001). Warfarin resulted in a 95 percent reduction in the risk of recurrent venous thromboembolism (95 percent confidence interval, 63 to 99 percent). Three patients assigned to the warfarin group had nonfatal major bleeding (two had gastrointestinal bleeding and one genitourinary bleeding), as compared with none of those assigned to the placebo group (3.8 vs. 0 percent per patient-year, P=0.09). CONCLUSIONS: Patients with a first episode of idiopathic venous thromboembolism should be treated with anticoagulant agents for longer than three months.

Anticoagulants↗
PubMed1999

Adrenal function in premature infants during inhaled beclomethasone therapy.

OBJECTIVE: We tested the hypothesis that inhaled beclomethasone therapy for prevention of bronchopulmonary dysplasia does not cause adrenal suppression. STUDY DESIGN: Infants receiving ventilatory support with birth weights </=1250 g and born at <33 weeks' gestation, age 3 to 14 days, were enrolled in a multicenter randomized trial to study the efficacy and safety of beclomethasone therapy versus placebo for prevention of bronchopulmonary dysplasia. Adrenal function was assessed on study day 21 (+/- 2 days) by determination of basal and stimulated plasma cortisol levels. Initially, cortisol response was assessed with insulin-induced hypoglycemia test (IIHT) (n = 63) until an interim analysis revealed insignificant cortisol response in both study groups. Thereafter, cosyntropin stimulation was used (n = 85). RESULTS: Beclomethasone therapy was associated with lower median basal cortisol levels (5 microg/dL beclomethasone, 6 microg/dL placebo, P =.04). IIHT revealed insignificant change in cortisol response within each group. Cortisol response to cosyntropin stimulation was similar for each group (17 microg/dL beclomethasone, 18 microg/dL placebo, P =.86). CONCLUSION: Beclomethasone therapy was associated with a small decrease in basal cortisol levels. There was no evidence of adrenal suppression in response to cosyntropin stimulation during beclomethasone therapy. Lack of cortisol response to hypoglycemia may reflect missed timing and/or decreased response of the premature infants' hypothalamic-pituitary-adrenal axis to hypoglycemia.

Administration, Inhalation↗
PubMed1998

Sensitivity and specificity of a rapid whole-blood assay for D-dimer in the diagnosis of pulmonary embolism.

BACKGROUND: Patients with suspected pulmonary embolism often have nondiagnostic lung scans and may present in circumstances where lung scanning is unavailable. Levels of D-dimer, a fibrin-specific product, are increased in patients with acute thrombosis; this may simplify the diagnosis of pulmonary embolism. OBJECTIVE: To determine the sensitivity and specificity of a whole-blood D-dimer assay in patients with suspected pulmonary embolism and in subgroups of patients with low pretest probability of pulmonary embolism or nondiagnostic lung scans. DESIGN: Prospective cohort. SETTING: Four tertiary care hospitals. PATIENTS: 1177 consecutive patients with suspected pulmonary embolism. MEASUREMENTS: All patients underwent an assessment of pretest probability by use of a standardized clinical model, a D-dimer assay, ventilation-perfusion lung scanning, and bilateral compression ultrasonography. Patients in whom pulmonary embolism was not initially diagnosed were followed for 3 months. Accordingly, patients were categorized as positive or negative for pulmonary embolism. RESULTS: Of the 1177 patients, 197 (17%) were classified as positive for pulmonary embolism. Overall, the D-dimer assay showed a sensitivity of 84.8% and a specificity of 68.4%. In 703 patients (3.4%) with a low pretest probability of pulmonary embolism, the likelihood ratio associated with a negative D-dimer test result was 0.27, resulting in a posterior probability of 1.0% (95% CI, 0.3% to 2.2%). In 698 patients with nondiagnostic lung scans (previous probability, 7.4%), the likelihood ratio associated with a negative D-dimer test result was 0.36, resulting in a posterior probability of 2.8% (CI, 1.4% to 4.8%). CONCLUSIONS: A normal D-dimer test result is useful in excluding pulmonary embolism in patients with a low pretest probability of pulmonary embolism or a nondiagnostic lung scan.

Algorithms↗
PubMed1997

Neonatal outcome of very premature infants from multiple and singleton gestations.

OBJECTIVES: Our purpose was to determine whether, in the era of surfactant treatment, very premature neonates from multiple gestations have outcomes similar to those of singletons. STUDY DESIGN: We collected data on 572 infants (369 singletons, 203 multiple gestation) born and cared for at a single institution from July 1, 1992, through Dec, 31, 1994, of gestational ages 24 to 32 weeks. We compared singleton infants with infants from multiple gestations within gestational age categories 24 to 26 weeks, 27 to 29 weeks, and 30 to 32 weeks. RESULTS: Infants of multiple gestations were more likely to have been born by cesarean section. The incidences of respiratory distress syndrome and bronchopulmonary dysplasia were similar, except that respiratory distress syndrome was more frequent in infants of multiple gestations at 30 to 32 weeks. Infants of multiple gestations from 27 to 29 weeks were more likely to have at least one of the following complications: patent ductus arteriosus, intraventricular hemorrhage, necrotizing enterocolitis, or retinopathy of prematurity. Further analysis suggested that this increase is unlikely to cause a difference in long-term outcome. The survival to discharge increased from 79% (multiples) and 81% (singletons) at 24 to 26 weeks to 98% (multiples) and 96% (singletons) at 30 to 32 weeks. CONCLUSIONS: Incidences of significant neonatal problems in very premature infants from multiple gestations who are born alive are little different from those of singletons. These data should have an impact on decision making in the perinatal and neonatal care of infants of multiple gestations.

Birth Weight↗
PubMed1994

Use of Hirulog in the prevention of venous thrombosis after major hip or knee surgery.

BACKGROUND: The study objective was to determine whether Hirulog, a direct thrombin inhibitor, has potential efficacy and safety in the prevention of deep vein thrombosis (DVT) in orthopedic patients. A phase 2 open-label, dose-escalating design was used to study 222 unselected patients undergoing major hip or knee surgery in tertiary-care, university-affiliated hospitals. METHODS AND RESULTS: Subcutaneous Hirulog was initiated postoperatively. Patients were evaluated for bleeding and symptomatic pulmonary embolism, and mandatory bilateral venography was performed before discharge. Dose escalations were made on the basis of observed rates of bleeding and venous thrombosis. There were five dosage regimens used: 0.3 mg/kg every 12 hours, 0.6 mg/kg every 12 hours, 1.0 mg/kg every 12 hours for 3 days followed by 0.6 mg/kg every 12 hours for up to 11 days, 1.0 mg/kg every 12 hours, and 1.0 mg/kg every 8 hours. One hundred seventy-seven patients who had technically adequate bilateral venography or objectively documented pulmonary embolism were included in the primary analysis of efficacy. The highest dosage regimen (1.0 mg/kg every 8 hours) provided the lowest rates of total DVT (17%) and proximal DVT (2%), both of which were significantly lower (P = .010 and P = .023, respectively) than the pooled rates of total (43%) and proximal (20%) DVT seen with the first four regimens. Bleeding rates were low (< 5%) with all regimens. CONCLUSIONS: This study demonstrates that 1.0 mg/kg Hirulog every 8 hours started postoperatively is potentially efficacious and safe for the prevention of DVT after major hip or knee surgery.

Aged↗
PubMed1994

Effects on thrombin generation of single injections of Hirulog in patients with calf vein thrombosis.

STUDY OBJECTIVE: To determine whether single injections of Hirulog, a direct thrombin inhibitor, can inhibit thrombin generation in patients with calf vein thrombosis and, if so, if the inhibition is sustained. DESIGN: Phase II open label cohort study. SETTING: Tertiary-care referral centres, university affiliated hospitals. PATIENTS: 10 patients with venographically-demonstrated calf vein thrombosis. INTERVENTION: Patients received a single injection of Hirulog, either 1.0 mg/kg subcutaneously or 0.6 mg/kg as a 15 min intravenous infusion. Prothrombin fragment (F1++2) levels, as an index of thrombin generation, were measured before as well as 6 h post- and 24 h post-Hirulog administration. Patients were followed with non-invasive tests to detect thrombus extension into the proximal veins. RESULTS: There was a significant reduction in the levels of F1+2 with both regimens, 6 h after Hirulog. The F1+2 levels 24 h post-Hirulog showed a significant increase relative to the 6 h post-Hirulog results. One patient developed thrombus extension into the popliteal vein and was treated with conventional anticoagulants. CONCLUSION: The single injections of Hirulog used in the study produced incomplete and temporary suppression of F1+2. Complete and permanent inhibition of thrombin generation with Hirulog in patients with calf vein thrombosis may require higher doses, multiple subcutaneous injections and/or prolonged intravenous infusion.

Aged↗
PubMed1988

The role of evidence in the consensus process. Results from a Canadian consensus exercise.

As part of a consensus conference on cesarean birth, the ten-member consensus panel rated 224 clinical scenarios on their appropriateness for a cesarean section. Ratings were obtained before and immediately after the consensus conference. The level of agreement (consensus) among panelists was assessed separately for scenarios with good research evidence (evidence scenarios) and for those with conflicting, poor, or no evidence (nonevidence scenarios). For each scenario, consensus between panelists was measured as total agreement, partial agreement, or disagreement on the appropriateness of a cesarean section. Before the conference, total or partial agreement existed for a larger percentage of evidence than nonevidence scenarios (85% vs 30%), with the pattern reversed for disagreements (15% vs 70%). After the conference, possible improvement in the level of consensus actually occurred for 71% of the evidence and only 24% of the nonevidence scenarios. Thus, the consensus process, as structured here, was sensitive to the availability of good evidence and suggests that aspects of both expert and public processes can successfully be combined. However, an improvement could be made in the process by grading final recommendations according to the availability of rigorous research evidence.

Breech Presentation↗
PubMed1988

On not harming: two traditions.

While ancient in origin, the principle, "Do No Harm," continues to occupy a prominent place in many present-day medical ethics codes. Of all the versions of the principle two distinct varieties can be distinguished. These parallel two ethical traditions. This paper develops the contrast between the two versions, relates them to the two ongoing ethical traditions, and then uses insights from contemporary ethical theory to demonstrate the significance of one of the versions. Finally it suggests some contemporary applications for a medical ethic and medical education.

Beneficence↗