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Biomedical subjects

M Stoddard

Publications and source records attributed to M Stoddard.

13 recordsLinked to original sources
PubMed2005

Epidemiology of cystic fibrosis-related diabetes.

OBJECTIVES: Cystic fibrosis-related diabetes (CFRD) has emerged as an important complication of CF. To better understand who is at risk of developing CFRD, to gain insight into the impact of CFRD on pulmonary and nutritional status, and to assess the association of CFRD with various practice patterns and comorbid conditions, we characterized the Epidemiologic Study of Cystic Fibrosis (ESCF) patient population. STUDY DESIGN: Analyses were performed on the 8247 adolescents and adults who were evaluated at one of 204 participating sites during 1998. CFRD was defined as the use of insulin or an oral hypoglycemic agent at any time during the year. RESULTS: Previously reported risk factors for CFRD including age, gender (female), and pancreatic insufficiency were confirmed in this study. Patients with CFRD had more severe pulmonary disease, more frequent pulmonary exacerbations, and poorer nutritional status as compared with those without diabetes. CFRD also was associated with liver disease. CONCLUSIONS: CFRD is a common complication in adolescents and adults that is associated with more severe disease.

Adolescent↗
PubMed1997

Preconditioning of human myocardium with adenosine during coronary angioplasty.

BACKGROUND: It is unknown whether adenosine can precondition human myocardium against ischemia in vivo. METHODS AND RESULTS: Thirty patients were randomized to receive a 10-minute intracoronary infusion of adenosine (2 mg/min) or normal saline; 10 minutes later, they underwent percutaneous transluminal coronary angioplasty (PTCA; three 2-minute balloon inflations 5 minutes apart). In control patients, the ST-segment shift on the intracoronary ECG was significantly greater during the first inflation than during the second and third inflations, consistent with ischemic preconditioning. In contrast, in adenosine-treated patients, there were no differences in ST-segment shift during the three inflations. The ST-segment shift was significantly smaller in the adenosine-treated group compared with the control group during all three inflations. The reduction in ST-segment shift afforded by adenosine during the first inflation (-72% versus first inflation in control subjects) was greater than that afforded by ischemic preconditioning in control subjects (-52% during the third versus first inflation). Measurements of chest pain score paralleled those of ST-segment shift. Adenosine had no effect on baseline regional wall motion as determined by quantitative two-dimensional echocardiography. Thus, intracoronary infusion of adenosine before PTCA rendered the myocardium remarkably resistant to subsequent ischemia. Judging from the intracoronary ECG, the protection provided by adenosine was even superior to that provided in control subjects by the ischemia associated with the first two balloon inflations. Infusion of adenosine had no major adverse effects in patients undergoing PTCA of the left anterior descending or circumflex arteries. CONCLUSIONS: Adenosine preconditions human myocardium against ischemia in vivo. Pretreatment with adenosine is remarkably effective (even more effective than ischemic preconditioning) and could be used prophylactically to attenuate ischemia in selected patients undergoing PTCA of the left anterior descending coronary artery. Whether adenosine can be safely infused into the right or the circumflex coronary artery in the presence of a temporary pacemaker remains to be established.

Adenosine↗
PubMed1994

Temperature may be an appropriate sensor for chronotropically incompetent patients with postural syncope.

Chronotropically incompetent patients benefit most from sensor driven rate response during exercise. Postural syncope may occur despite the chronotropic response because of the failure of currently available sensors to respond physiologically to postural changes. Seven chronotropically incompetent patients with postural syncope who had a dual chamber rate adaptive pacemaker (Circadia) that modulates heart rate in response to temperature change were studied with respect to: (1) response to exercise; and (2) head-up tilt (HUT). During exercise, continuous-wave Doppler of aortic velocities and two-dimensional echocardiographic derived measurements of left ventricular systolic function were used to assess cardiac function. Patients exercised longer (by an average of 168 sec) in the DDDR compared to the DDI mode (P = 0.013). Increase in exercise duration was due mostly to the sensor driven increase during DDDR pacing. During DDDR pacing, heart rate increased from 71 +/- 6 to 121 +/- 17 ppm compared to 70 +/- 1 to 103 +/- 21 ppm for the DDI pacing (P = 0.038). Stroke volume as assessed by Doppler derived stroke distance (SD) contributed more significantly to the cardiac output increase during exercise in the DDI mode (SD increased from 13.4 +/- 4 to 18 +/- 7 cm in DDI compared to 13 +/- 4 to 14 +/- 2 cm in DDDR mode), although these mechanisms were insufficient to fully compensate for failure of appropriate chronotropic response. In response to the HUT, right ventricular temperature increased from 36.78 degrees C +/- 0.29 degrees C to 36.89 degrees +/- 0.28 degrees C (P = 0.0002), and heart rate increased from 54 +/- 3 to 71 +/- 8 ppm (P = 0.0003) in the DDDR mode. No significant change in heart rate occurred in the DDI mode in response to the HUT. Strong positive correlation of temperature and heart rate was noted in all patients in response to HUT (P = 0.001, R2 = 0.755-0.976). We conclude that temperature sensor responds physiologically to exercise and HUT. Therefore, temperature sensing rate adaptive dual chamber pacing may be appropriate for chronotropically incompetent patients with posture related syncope.

Aged↗
PubMed1991

Infections in open fractures of the hand.

We reviewed one forty-six consecutive cases of patients with open fractures of the hand to identify factors that predict infection and poor outcome. The incidence of infection was 11%. The infection rate in type 1 open fractures was 0%; in type 2, 9%; and in type 3, 14%. Infection occurred in 20.5% of grossly contaminated wounds (p less than 0.02), and was most common in patients with extensive soft tissue and skeletal injury. Delay in treatment did not increase the incidence of infection or affect outcome. Functional outcome was highly correlated with the initial fracture type and with the presence of infection. Preoperative wound cultures were of no value in predicting the risk of infection or the nature of the likely pathogen. Patients with severe open fractures should be warned of the risk of infection, prolonged convalescence, and permanent impairment.

Adolescent↗
PubMed1990

Stroke volume measurements by electrical bioimpedance and echocardiography in healthy volunteers.

To evaluate the validity of three equations for estimation of thoracic electrical field size in a new bioimpedance algorithm, stroke volume (SV) as calculated by these equations was compared with that calculated by Doppler echocardiography in 48 healthy volunteers, both lean and obese. When the volume of electrically participating tissue was estimated from body height (modified Sramek) or body height corrected for body habitus (Sramek-Bernstein), there was considerable variation between bioimpedance and Doppler stroke volumes. When the volume of electrically participating tissue was estimated from the actual measurement of the height of the thorax and the circumference at the base of the thorax, the variation in SV differences decreased substantially (Sramek equation), although still considerable for clinical use, and there was no relationship between SV thus obtained and body habitus. Analysis of calculated stroke indices derived by our Doppler echocardiographic standard, as compared with values in the literature, revealed a systematic underestimation. We conclude that the original Sramek equation systematically underestimates SV by 15% to 20%, and the modified Sramek and Sramek-Bernstein equations systematically underestimates SV by 15% to 20%, and the modified Sramek and Sramek-Bernstein equations systematically overestimate SV in females by about 15%, but provide SV values in males in the predicted range. Further studies on the current assumption that the electrical field size is a truncated cone may improve precision of the bioimpedance method.

Adult↗
PubMed1981

Percutaneous transluminal angioplasty in patients with renal artery stenosis: follow-up studies.

Fifty renal artery stenoses in 38 hypertensive patients were treated with percutaneous transluminal angioplasty. Follow-up over a period of 1 to 24 months (mean, 9 mo.), including angiography, renal vein renin determinations, and radionuclide flow studies, were performed in 24 patients (32 stenoses). The initial dilatation was successful in 90% of stenoses and redilatation was necessary in 22% with a success rate of 84%. The mean systolic pressure decreased by 65.83 mm Hg and the mean diastolic pressure by 35.88 mm Hg in response to the treatment. Sixteen patients were cured, 18 were felt to have better control of blood pressure on medication, and 4 were not helped. Percutaneous transluminal angioplasty appears to be a technically feasible and clinically effective method of treating renovascular hypertension.

Adolescent↗
PubMed1975

Kinetic studies on the mechanism of pepsin action.

The linear noncompetitive inhibition of the pepsin-catalyzed hydrolysis of Ac-Phe-Phe-Gly at pH 2.1 by L-Ac-Phe, L-Ac-Phe-NH2, and L-Ac-Phe-OEt has been claimed to substantiate the ordered release of products specified by the amino-enzyme mechanism for pepsin action. According to this interpretation, the binding of inhibitor to free enzyme and the amino-enzyme intermediate (Scheme I) generates the observed inhibition pattern. The proposition is valid only if a simple alternative explanation for the kinetic data, Scheme II, can be disproved. Scheme II attributes the inhibition pattern to the binding of inhibitor to free enzyme and the enzyme-substrate (Michaelis) complex. The experiments reported here have enabled us to distinguish between the two mechanisms. The pepsin-catalyzed hydrolyses of Ac-Phe-Trp, Z-H'IS-Phe-Trp, Z-Gly-His-Phe-Trp, and Z-Ala-His-Phe-Trp at pH 1.8 occur exclusively at the Phe-Trp bond and must yield the same amino-enzyme, E-Trp, if it is implicated. Under these circumstances, Scheme I requires that a plot of 1/kc vs. (I)o for the four substrates and a given noncompetitive inhibitor provide a set of four parallel lines. Scheme II predicts that the four lines generally will not be parallel. L-Ac-Phe, L-Ac-Phe-NH2, L-Ac-Phe-OMe, and D-Ac-Phe act as linear noncompetitive inhibitors for the pepsin-catalyzed hydrolysis of the four Trp-containing substrates. The plot of 1/kc vs. (I)o for each inhibitor results in a set of four nonparallel lines. Therefore Scheme II must be correct and the detection of noncompetitive inhibition accompanying the pepsin-catalyzed hydrolysis of peptides offers no insight into the merits of the amino-enzyme hypothesis.

Binding, Competitive↗
PubMedDate not supplied

The costs and effects of switching calcium channel blockers: evidence from Medicaid claims data.

This study used Medicaid claims data from Pennsylvania to examine the costs and effects of changing calcium channel blocker therapies. Specifically, we compared Procardia XL with Adalat CC. They are the only once-daily-dosed, extended-release forms of nifedipine available. These drugs were interesting to compare for several reasons. First, because the frequency of treatment regimens has been shown to be the most important determinant of long-term compliance with calcium channel blocker medications, it was desirable to compare drugs having identical dosing regimens. Second, switching from one to the other should be quite feasible in most patients. Third, Adalat CC is priced (ie, average wholesale price) less than Procardia XL. The results indicate that prescription prices were lower when patients were switched from Procardia XL to Adalat CC, with no apparent effects on blood pressure control, the incidence of adverse drug reactions, or nonprescription health care costs. The potential savings to Medicaid from switching patients from Procardia XL to Adalat CC appears to be large, more than $2.5 million annually for Procardia XL-treated Medicaid patients in the state of Pennsylvania. Our study also demonstrates that large retrospective databases can be used to evaluate economic and clinical outcomes for specific therapy alternatives. Such evaluations are increasingly relevant to third-party payers, health maintenance organizations, and other parties involved in managed care.

Cohort Studies↗