Biomedical subjects

C Kearon

Publications and source records attributed to C Kearon.

60 records · Page 4Linked to original sources

PubMed1993

Factors determining pulmonary function in adolescent idiopathic thoracic scoliosis.

Adolescent idiopathic thoracic scoliosis may lead to severe pulmonary impairment and early death, but the responsible factors are poorly understood; pulmonary function is only weakly related to the angle of scoliosis. We performed a cross-sectional study using multivariate analysis to identify the individual and additive influence of different features of spinal deformity and nonstructural factors on pulmonary impairment. Pulmonary function was assessed by measuring lung volumes and diffusing capacity, with a priori selection of vital capacity (expressed as percentage of predicted, % VC) as the primary index of pulmonary impairment. Radiologic and physiologic measurements were made independently in 66 subjects who had not previously had spinal surgery. Angle of scoliosis (p = 0.01) was one of four features of spinal deformity associated with reduced % VC; greater number of vertebrae involved (p = 0.007), cephadal location of the curve (p = 0.04), and loss of the normal thoracic kyphosis (p = 0.002) made an equal and additive contribution to pulmonary impairment. Spinal deformity led to reductions in VC, primarily by reducing TLC. Spinal column rotation, respiratory muscle strength, and duration of the curvature were not related to pulmonary function (p > 0.05). We conclude that features of the spinal deformity are the major determinants of pulmonary impairment in idiopathic thoracic scoliosis but that the relationship between deformity and impairment is complex. The severity of pulmonary impairment cannot be inferred to a clinically useful extent from the angle of scoliosis alone.

Adolescent↗

PubMed1993

Factors influencing work capacity in adolescent idiopathic thoracic scoliosis.

The factors contributing to reduced work capacity (disability) in adolescent idiopathic thoracic scoliosis are poorly understood. We performed a cross-sectional study using multivariate analysis to identify the individual and additive influence of spinal deformity, pulmonary impairment, and muscular function on work capacity in 79 subjects with idiopathic scoliosis (angle of scoliosis 45 +/- 18.5 degrees, SD). Work capacity was measured using an incremental cycle test, and the cardiorespiratory response to exercise was compared with that of normal subjects. Work capacity was reduced (% Wcap, 86%; 95% CI 81.9 to 89.7), indicating significant disability. The % Wcap was unrelated to the nature and extent of spinal deformity (p > 0.05). Leg muscularity and pulmonary impairment had an additive influence on work capacity, the relationship with muscularity being the stronger of the two. Independently of muscularity and pulmonary impairment, a high heart rate response at submaximal work rates was also associated with a reduced work capacity. Ventilation was normal for metabolic demands. During exercise, the tidal volumes of scoliotic subjects were reduced in proportion to the vital capacity. We conclude that disability occurs with mild to moderate idiopathic scoliosis and appears to be related to a combination of reduced ventilatory capacity, reduced muscularity, and cardiovascular deconditioning. These findings suggest that physical activity should be encouraged in subjects with idiopathic scoliosis to maintain peripheral muscle and cardiovascular conditioning, thereby minimizing disability.

Adolescent↗

PubMed1989

An approach to dyspnea in cancer patients.

There are many potential causes of dyspnea in the patient with cancer. Ultimately, a sense of increased respiratory effort is common to all of these diverse situations. An organized approach to dyspnea in the cancer patient is presented based on psychophysical principles, and treatment modalities are suggested.

Airway Resistance↗

PubMedDate not supplied

The diagnosis of pulmonary embolism.

Although clinical diagnosis of pulmonary embolism (PE) is not sufficiently reliable to determine management, it is valuable for stratifying patients into high, intermediate, and low clinical suspicion of embolism. Clinical assessment can then be combined with lung scanning to identify groups of patients with a sufficiently high or low probability of PE that a decision to anticoagulate or withhold therapy can be made. Approximately half of patients with suspected PE will fall into one of these categories. Thrombosis in the deep veins of the leg (DVT) can be detected by noninvasive tests in approximately 50%, and by bilateral venography in approximately 70% of patients with PE, and provides grounds for anticoagulation of some patients with nondiagnostic combinations of clinical and lung scan assessments. Failure to detect DVT makes it less likely but does not exclude the possibility that the patient had a PE. Preliminary evidence suggests that the majority of patients with nondiagnostic combinations of clinical assessment, lung scanning, and negative noninvasive tests for DVT can safely be managed without anticoagulation, provided serial noninvasive tests for DVT remain normal over a 2-week period. Pulmonary angiography may be advisable in patients with nondiagnostic combinations of the above tests in whom (a) the probability of PE remains high (e.g. 30-80%), (b) cardiopulmonary reserve is poor, (c) serial follow-up is not feasible, or (d) future management (e.g. subsequent pregnancy) would be influenced by the result. D-Dimer measurements are sensitive but nonspecific for PE and therefore may have a high negative predictive value, further simplifying the diagnostic approach to PE.

Hematologic Tests↗

PubMedDate not supplied

[Optimal duration of anticoagulant treatment of venous thromboembolism].

RECURRENT THROMBOSIS VERSUS ANTICOAGULANT-RELATED BLEEDING: The optimal duration of anticoagulation for venous thromboembolism depends on the balance between the risk of thrombosis if anticoagulation is stopped, and the risk of bleeding if patients remain on treatment. In the past decade, five large well designed trials have been completed which have compared different durations of anticoagulation for the treatment of various categories of patients with venous thrombosis. In conjunction with the findings of a number of other prospective studies, these trials have helped to identify risk factors for recurrent venous thrombosis and anticoagulant-related bleeding, and have led to a better understanding of the optimal duration of therapy for individual patients. RISK OF RECURRENT THROMBOSIS: The risk of recurrent thrombosis is low if thrombosis was precipitated by a major reversible risk factor such as surgery. Patients with idiopathic thrombosis (no apparent risk factor) and those with persistent risk factors (e.g., cancer), have a high risk of recurrence. Some hereditary (e.g., protein C, S or antithrombin deficiency) and acquired (e.g., antiphospholipid antibodies) thrombophilic states are risk factors for recurrence independently of whether thrombosis was, or was not, provoked by a major risk factor. DURATION OF THERAPY: Patients with a low risk of recurrence should be anticoagulated for three months. Others should be treated from 6 months to indefinitely, depending on the balance between the risk of recurrence and the risk of bleeding in each individual patient.

Anticoagulants↗

PubMedDate not supplied

The relation between the activated partial thromboplastin time response and recurrence in patients with venous thrombosis treated with continuous intravenous heparin.

BACKGROUND: It is unknown whether the true risk of recurrent venous thromboembolism (VTE) is increased in patients with proximal deep vein thrombosis who are treated with continuous intravenous heparin and fail to reach a therapeutic activated partial thromboplastin time (APTT) within 24 to 48 hours of initiation of treatment. METHODS: To compare the risk of recurrent VTE in patients with early subtherapeutic APTT results and those with APTT results above the lower limit of the therapeutic range, we performed a formal review of the literature. We examined all available studies that provided information on the relation between the risk of recurrent VTE and the APTT response to heparin when initiated as a bolus followed by a continuous intravenous infusion of at least 30 000 U/24 h. RESULTS: Five studies were included in the final analysis. The overall recurrence rate was 6.3% in patients whose APTT results were subtherapeutic for the first 24 to 48 hours and 7% in patients whose APTT results were above the lower limit of the therapeutic range, providing a pooled odds ratio of 0.89 with a 95% confidence interval of 0.2 to 4.0. CONCLUSIONS: In patients with VTE who are treated with a bolus of heparin followed by a continuous intravenous infusion of at least 30 000 U/24 h, no convincing evidence shows that the risk of recurrent VTE is critically dependent on achieving a therapeutic APTT result at 24 to 48 hours.

Heparin↗