Biomedical subjects

P C O'Brien

Publications and source records attributed to P C O'Brien.

At least 199 records · Page 11Linked to original sources

PubMed1993

A 4, 2, and 1 stepping algorithm for quick and accurate estimation of cutaneous sensation threshold.

In quantitative sensory testing, certain methods may lead to incorrect estimates of vibratory (VDT), cool (CDT), or warm (WDT) detection thresholds. We have shown that the specific forced-choice algorithm of testing employed in our Computer-Assisted Sensory Examination (CASE IV) system, when compared with other tests of nerve dysfunction, provides accurate and reproducible estimates of these thresholds. Because this forced-choice algorithm is time consuming and performance might be made worse by drowsiness or boredom, we explored other algorithms that might provide estimates of threshold similar to those obtained with the forced-choice algorithm, but more quickly. In a trial of 25 healthy subjects and 25 patients with neuropathy, the 4, 2, and 1 stepping algorithm with null stimuli, based in part on comparative data from computer simulation and insights from patient decision making, provides an accurate estimate of threshold. On average, the time needed for forced-choice testing was 12.8 +/- 2.9 minutes (mean +/- SD). For 4, 2, and 1 stepping testing, it was 2.7 +/- 2.5 minutes--a large saving of time. Since null stimuli were employed in the 4, 2, and 1 stepping algorithm, it was possible to monitor for spurious responses and repeat the test if they occurred at an excessive rate. The algorithm appears to be sufficiently robust to be recommended for clinical use and for some controlled clinical and epidemiologic trials.

Algorithms↗

PubMed1993

Theophylline effect on sleep in normal subjects.

In an effort to isolate the effect of theophylline on sleep from the effect of asthma, we examined the impact of oral theophylline on sleep quality in normal, nonasthmatic subjects. Ten healthy, nonsmoking, male subjects ranging in age from 23 to 35 were studied. The subjects were randomly divided into two groups and studied in a double-blinded, crossover designed protocol. Each group underwent two consecutive nights in the sleep laboratory. Group one received four doses of 300 mg of sustained-release theophylline at 12-h intervals prior to the study night. Group two received a placebo. After 14 days, the patients crossed over to the other group, and the procotcol was repeated. The mean serum theophylline level on the morning following the study night was 7.85 +/- SD 2.12 micrograms/ml, with a range of 5.1 to 12.1 microns/ml. The analysis of variance for a crossover design showed no order effect. The analysis for drug effect showed that theophylline administration resulted in a statistically significant adverse effect on arousals per sleep hour (19.3 vs 15.9 for placebo, p = .006) and total sleep time (370.9 min vs 399.45 min for placebo, p = .015). Comparing the sum of ranks data, theophylline was found to have a significant adverse effect on sleep quality (p = .036). We conclude that low doses of oral theophylline result in a significant disturbance in sleep quality in normal nonasthmatic subjects.

Adult↗

PubMed1993

Reoperative insulinomas, 1927 to 1992: an institutional experience.

BACKGROUND: Between 1927 and 1992, 313 patients have undergone surgery for insulinoma(s) at our institution, 12% of which were reoperations. We retrospectively reviewed all cases (n = 39) of reoperative surgery for persistent hyperinsulinism to identify changing patterns in surgical approach, morbidity, and outcome and to evaluate the influence of preoperative and intraoperative localization studies. METHODS: The diagnosis of endogenous hyperinsulinism has evolved from satisfying Whipple's triad to documenting concomitant hypoglycemia and endogenous hyperinsulinemia. Thirty-nine patients were divided into two groups for comparison: those treated before localization studies were available (1927 to 1967) (n = 17) and those treated since that time (n = 22). Initial operations were also compared with reoperations among these 39 patients. RESULTS: There were 26 women and 13 men (mean age, 42 years). There was at least one positive preoperative localization study in 16 of 22 patients (73%). Intraoperative ultrasonogram and careful palpation successfully identified 10 of 11 tumors in the reoperative setting. Blind or completion pancreatectomies were common before 1967 (10 of 17 patients). Since 1967, 14 of 22 patients have undergone enucleation of their primary tumor. Operative morbidity increased from 21% to 58% with reoperation but decreased from 65% to 29% (p = 0.026) when comparing the preangiography to the postangiography eras. The development of iatrogenic diabetes mellitus occurred in 13 patients (33%) after reoperation. Forty-one percent had diabetes before 1967 and 27% since that time (p = not significant). Thirty-four of 36 patients (94%) without malignant tumors were cured by reoperation. There was one operative death. Survival for patients who underwent completion or total pancreatectomy was significantly reduced (p = 0.003). CONCLUSIONS: Reoperations for persistent hyperinsulinism can be highly successful in experienced hands. These reoperations, however, are associated with increased morbidity and iatrogenic diabetes. With experience and the use of selected localization studies, first-time failures can be avoided in most cases thus reducing the need for reoperations and its inherent sequelae.

Adolescent↗

PubMed1992

Magnetic resonance image-based hippocampal volumetry: correlation with outcome after temporal lobectomy.

We developed a magnetic resonance imaging (MRI)-based technique for measuring the volume of the hippocampal formation. In this study, the relationship between volumes of the hippocampal formation and outcome (i.e., postoperative seizure control) after anterior temporal lobectomy for intractable epilepsy was analyzed in 50 consecutive patients in whom the surgical specimen did not contain an epileptogenic mass lesion. Outcome was classified as either satisfactory or unsatisfactory. A significant relationship was found between outcome and volume of the operated hippocampal formation (p = 0.012), as well as a derived volumetric measure (nonoperated minus operated volume of the hippocampal formation) (p = 0.004). The association between outcome and nonoperated volume was borderline (p = 0.057). Thirty-four (97%) of 35 patients in whom the volumetric study and electroencephalography (EEG) concordantly lateralized the seizure disorder had satisfactory postoperative seizure control. Conversely, only 7 (42%) of 12 patients in whom the volume study was nonlateralizing and 1 (33%) of 3 in whom the EEG and volume study were discordant has a satisfactory outcome. We regard our MRI-based study of hippocampal formation volume as a noninvasive surrogate for the identification of moderate or severe mesial temporal sclerosis. The technique is a useful adjunct in a multidisciplinary, preoperative epilepsy evaluation when T2-weighted MRIs do not reveal an epileptogenic mass lesion. The reasons for the usefulness of this imaging technique are: (1) It is an independent source of information on seizure lateralization, (2) it will provide information as to expected postoperative outcome, and (3) it may aid in appropriately selecting patients for invasive preoperative monitoring studies.

Adult↗

PubMed1992

C-peptide suppression test: effects of gender, age, and body mass index; implications for the diagnosis of insulinoma.

To assess the effects of gender, age, and body mass index (BMI) on suppression of plasma C-peptide during insulin-induced hypoglycemia, 101 lean and obese, healthy men and women ages 20 to 80 yr underwent infusion of human regular insulin, 0.125 U/kg over 60 min after an overnight fast. Plasma glucose, insulin, and C-peptide were measured every 30 min for 120 min. C-peptide concentrations were influenced by gender at 30 min, by BMI at baseline and both BMI and age at all subsequent time points. Because of variations in baseline plasma C-peptide concentrations, percent decrease in C-peptide was evaluated. Significantly less percent decrease of C-peptide with increased age at 30, 60, and 90 min and with increased BMI at 30 and 60 min were noted with no effect of gender. From stepwise regression analysis using multiple, additional variables only the plasma glucose concentration at 30 min made a significant, albeit small (8%), contribution to the variability in percent decrease in C-peptide at 60 min. When C-peptide responses from eight histologically confirmed insulinoma patients were contrasted to values adjusted for age, gender, and BMI of normal subjects, all insulinoma patients had abnormal responses when percent decrease in C-peptide was used, whereas only four insulinoma patients had abnormal response when actual C-peptide concentrations were used.

Adult↗

PubMed1992

MR-based hippocampal volumetry in the diagnosis of Alzheimer's disease.

We evaluated a new magnetic resonance (MR)-based technique for performing volumetric measurements of temporal lobe structures. The technique was designed to assist in making the clinical diagnosis of dementia of the Alzheimer type (DAT). We chose specific anatomic regions of interest because of their known involvement in memory function and in the neuropathology of DAT and used a regression model to assess the effects of age on the volumes of the anterior temporal lobe (ATL) and the hippocampal formation (HF). These measurements were normalized by total intracranial volume (TIV). The volumetric measurements of both the normalized ATL and HF were significantly smaller (p less than 0.001) in DAT patients (N = 20) than in controls (N = 22), but the HF volumes provided much better separation between the two groups. Eighty-five percent of the DAT patients fell below the range of the HF/TIV measurement for the control subjects. This separation held up over the entire age range studied. Normalized volumes of both the HF and ATL decreased with age significantly for both the DAT patients and the controls. These results support the contention that MR-based HF volumetric measurements are accurate in differentiating DAT patients from cognitively normal elderly individuals. This technique may be a useful adjunct in making the clinical diagnosis of DAT.

Aged↗

PubMed1992

The Rochester Diabetic Neuropathy Study: reassessment of tests and criteria for diagnosis and staged severity.

We evaluated the initial assessments of the 380 diabetic patients with and without polyneuropathy in the Rochester Diabetic Neuropathy Study for (1) associations among neuropathy test results, (2) usefulness of different tests for diagnosing and staging polyneuropathy, (3) appropriateness of different minimal criteria for the diagnosis of polyneuropathy, and (4) significant differences in test results with increasing stage of polyneuropathy. Nerve conduction ([NC]; abnormality in two or more nerves) and quantitative autonomic examination ([QAE]; decreased heart-beat response to deep breathing [DB] or the Valsalva maneuver [VAL]) were the most sensitive and objective and were especially suitable for detection of subclinical neuropathy. We propose the following minimal criteria for the diagnosis of diabetic polyneuropathy: greater than or equal to 2 abnormal evaluations (from among neuropathic symptoms, neuropathic deficits, NC, quantitative sensory examination [QSE], and QAE) with one of the two being abnormality of NC or QAE (DB or VAL). Neuropathy Symptom Score, Neuropathy Disability Score, QSE (vibratory or cooling detection threshold), and summated compound muscle action potential of ulnar, peroneal, and tibial nerves were best for judging severity. Inability to walk on heels provided a discrete separation of diabetic patients into those with mild and those with more severe neuropathy--a separation helpful in staging.

Diabetic Neuropathies↗

PubMed1992

Methods for measuring plasma hemoglobin in micromolar concentration compared.

Of eight methods examined for measuring plasma hemoglobin in micromolar concentration, all exhibited acceptable linearity, reproducibility, and concurrence except when specimens were icteric or lipemic or contained methemoglobin or methemalbumin. Measurement of absorbance at 578 nm with an Allen correction permits precise assay of plasma oxyhemoglobin concentration as low as 0.01 g/L (1 mg/dL, 0.16 mumol/L), unaffected by hyperlipidemia or hyperbilirubinemia. Discrepancies between methods occurred in 11.6% of a consecutive series of 50 nonicteric patients' plasma specimens. Examination of absorption spectra is helpful when discrepancies are observed between methods. The presence of methemalbumin or methemoglobin in plasma is not recognized by methods that measure only oxyhemoglobin. Increased ceruloplasmin or beta-carotene does not significantly affect results.

Bilirubin↗

PubMed1991

Antecedent medical diseases in patients with amyotrophic lateral sclerosis. A population-based case-controlled study in Rochester, Minn, 1925 through 1987.

Odds ratios (ORs) were estimated for the prevalence of antecedent endocrine, metabolic, or vascular diseases among 45 patients with amyotrophic lateral sclerosis from the Rochester, Minn, population compared with 90 control subjects matched for sex, year of birth, period of observation, and residence. Hypertension occurred less frequently in male patients with amyotrophic lateral sclerosis (4%) than in control subjects (30%; OR = .10). Because of small population size, no conclusions can be drawn with respect to the following antecedent conditions: thyroid disease (OR = 1.61), coronary artery disease (OR = .58), obesity (OR = .52), diabetes (OR = 1.00), cerebrovascular disease (OR = .21), and peripheral vascular disease (OR = 1.23). The heterogeneity of antecedent thyroid disease makes it highly unlikely that any specific thyroid lesion is causally associated with most cases of amyotrophic lateral sclerosis. Hypertension may be a marker for protective factors against the development of amyotrophic lateral sclerosis in men.

Aged↗

PubMed1991

Magnetic resonance imaging-based volume studies in temporal lobe epilepsy: pathological correlations.

We performed a prospective study correlating magnetic resonance imaging volume measurements of the hippocampal formation with histopathology in 24 patients with intractable partial epilepsy who subsequently underwent an anterior temporal lobectomy for their seizure disorder. Patients with mass lesions verified pathologically were excluded from this study. In 71% of patients, quantitative hippocampal formation atrophy correctly lateralized the temporal lobe of seizure origin; in 29%, the volume study was indeterminant. The severity of the pathological alterations in the hippocampus correlated with the hippocampal formation volume determination. Mesial temporal sclerosis was identified in the surgically excised temporal lobe in 15 patients. The magnetic resonance imaging volume studies indicated hippocampal atrophy in the temporal lobe resected in 14 of the 15 patients. Magnetic resonance imaging-based volume measurements of the hippocampal formation increase the diagnostic yield of magnetic resonance imaging scanning in patients with intractable partial epilepsy related to mesial temporal sclerosis.

Adolescent↗

PubMed1991

The effects of transformations and preliminary tests for non-linearity in regression.

Non-linear relationships between two variables are often detected as a result of a preliminary statistical test for linearity. Common approaches to dealing with non-linearity are to (a) make a linearizing transformation in the independent variable or (b) fit a relationship that is non-linear in the independent variable, such as including a quadratic term. With either approach, the resulting test for association between the two variables can have an inflated type I error. We consider testing the significance of the quadratic term in a quadratic model as a preliminary test for non-linearity. Using simulation experiments and asymptotic arguments, we quantify the type I error inflation and suggest simple modifications of standard practice to protect the size of the type I error. In the case of quadratic regression, the type I error will be increased by roughly 50 per cent. The simple strategy of appropriately correcting the alpha-level is shown to have minimal loss of power if the relationship is truly linear. In the case of a linearizing transformation, the impact on the type I error will depend on the values of the independent variable and on the set of potential linearizing transformations considered. Simulation results suggest that a procedure which adjusts the test statistic according to the results of the preliminary test may offer adequate protection.

Aging↗

PubMed1991

Suture entrapment and secondary ureteral obstruction.

During the 6-year period ending in 1988, suture entrapment and secondary postoperative ureteral obstruction occurred in 18 (0.33%) of the 5379 patients who underwent major pelvic operations for benign conditions. Sixteen cases occurred after vaginal surgery and two after abdominal hysterectomy. Placement of the McCall suture or sutures for elevation of a bladder neck caused ureteral entrapment most frequently. Early diagnosis was facilitated by comparison of preoperative and postoperative serum creatinine levels. The mean change in serum creatinine level in patients with unilateral obstruction was an increase of 0.8 mg/dl. Treatment by either antegrade placement of ureteral stents or abdominal exploration with deligation or ureteroneocystotomy was successful in all cases. Retrograde placement of ureteral stents was unsuccessful.

Female↗

PubMed1991

Invasive vaginal carcinoma: analysis of early-stage disease.

From 1960 through 1987, 89 patients with stage I (44 patients) or II (45 patients) vaginal carcinoma (excluding melanomas) were treated primarily at the Mayo Clinic. Treatment consisted of surgery alone in 52 patients, surgery plus radiation in 14, and radiation alone in 23. The median duration of follow-up was 4.4 years. The 5-year survival (Kaplan-Meier method) was 82% for patients with stage I disease and 53% for those with stage II disease (p = 0.009). Analysis of survival according to treatment did not show statistically significant differences. This report is consistent with previous studies showing that stage is an important prognostic factor and that treatment can be individualized, including surgical treatment for primary early-stage vaginal cancer.

Adolescent↗

PubMed1991

Increased risk of profound weight loss among women exposed to diethylstilbestrol in utero.

We surveyed 1711 women exposed to diethylstilbestrol in utero, and 919 women not exposed, concerning lifetime weight loss histories. The prevalence of a history of unexplained profoundly low body weight (weight less than or equal to 80% of expected weight for age, sex, and height) was 18.7 per 1000 in the exposed group compared to 3.3 per 1000 in the unexposed group; a 5.72 to 1 ratio of increased risk.

Adult↗

PubMed1991

Use of human ultralente as the basal insulin component in treatment of patients with IDDM.

To determine the suitability of a single subcutaneous evening injection of human ultralente (UL) as the basal component of an intensive insulin therapy program, insulin concentrations were measured in five insulin-dependent diabetic volunteers over a 40-h period. Each patient had been maintained on a human UL-based program for at least one month prior to the study. All short-acting insulin was withheld during the study. The onset of action of human UL was 2 to 4 h, and a broad, variable peak was observed between 6 and 12 h after each injection. We concluded that human UL does not provide constant basal insulin concentrations. When human UL is considered as part of an intensive insulin therapy program, this potential disadvantage must be weighed against the potential advantage of low antigenicity.

Adult↗

PubMed1991

Functioning insulinoma--incidence, recurrence, and long-term survival of patients: a 60-year study.

For the 60-year period from 1927 through 1986, we assessed the incidence, recurrence, and long-term survival among all Mayo Clinic patients with histologically confirmed functioning insulinoma. With use of the complete medical record system at Mayo and the comprehensive epidemiologic data base of residents of Olmsted County, Minnesota, we found 224 patients in whom an initial pancreatic exploration at Mayo had confirmed the presence of insulinoma. The median age (and range) of these patients at surgical diagnosis was 47 (8 to 82) years, and 59% were female patients. During the study period, eight cases of insulinoma occurred among residents of Olmsted County; their age and gender distributions were similar to those of the total cohort. The incidence of insulinoma among residents of Olmsted County increased during the study period to a stable level during the last 2 decades of 4 cases per 1 million person-years. For the total cohort, 7.6% had multiple endocrine neoplasia type I (MEN I), and 5.8% had malignant insulinoma. The risk of recurrence was greater among patients with MEN I (21% at 10 and 20 years) than in those without MEN I (5% at 10 years and 7% at 20 years). Although survival of the total cohort was not significantly impaired, it was significantly worse than expected for patients with malignant insulinoma (29% versus 88% expected at 10 years postoperatively). We conclude that insulinoma is less rare than previously suspected. After successful surgical removal, the long-term risk of recurrent insulinoma is relatively high in patients with MEN I; for patients with benign disease, the long-term survival is normal.

Adolescent↗

PubMed1991

Cardiac surgery in the octogenarian: perioperative outcome and clinical follow-up.

The perioperative and follow-up results of cardiac operations employing extracorporeal circulation and cold cardioplegic arrest were examined in 191 consecutive patients greater than or equal to 80 years of age having surgery over a 5 year period (1982 to 1986). Most patients had severe preoperative symptoms with functional class III (39.8%) or IV (57.1%) limitation. The overall 30 day postoperative cardiac mortality rate was 15.7%. The total in-hospital mortality rate was 18.8%; the mean postoperative hospital stay was 16.4 +/- 13.3 days. The perioperative mortality rate for elective operations was as follows: coronary artery bypass (5.6%), aortic valve replacement (9.6%), aortic valve replacement with coronary bypass (17.9%) and mitral valve surgery with or without coronary bypass (21.4%). Urgent operations were performed in 39 patients (20.4%) with a total perioperative mortality rate of 35.9%; urgent coronary artery bypass was performed in 26 patients (67%) with an in-hospital mortality rate of 23.1%. Clinical evidence of left ventricular failure, functional class IV symptoms, left ventricular ejection fraction less than 50%, mitral valve repair or replacement for severe mitral regurgitation and urgent operation were associated with an increased perioperative mortality rate. Follow-up study in all 155 patients surviving postoperative hospitalization at 22.6 +/- 14.8 months showed significant improvement in symptom status in all surgical subgroups. There were 18 follow-up deaths (11.6%); 10 were noncardiac. The actuarial survival rate of the entire study group was significantly better than that in age- and gender-matched control subjects (p = 0.037).(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗

PubMed1991

Simultaneous bilateral hernia repair. A case against conventional wisdom.

The timing of bilateral hernia repair remains controversial. Because of reported high recurrence rates after simultaneous bilateral repair, staged procedures have been suggested. This study determined recurrence and complication rates of unilateral versus simultaneous bilateral repair. Of 659 patients undergoing hernia repair between 1974 and 1980, 333 underwent unilateral repair and 329 had simultaneous bilateral repair. More than 90% of patients were followed until death or a minimum of 60 months (median, 104 months). Perioperative complications were associated with 18% of repairs. More morbidity occurred in the bilateral group. However complication rates for specific events were not significantly different, except for urinary retention, which occurred in 20 patients (6.1%) of the unilateral group and 49 (15%) of the bilateral group (p less than 0.001). Overall 25 recurrences occurred in the unilateral group and 31 in the bilateral group. Recurrence rates at 5 and 9 years were, respectively, 4.8% and 8.8% in the unilateral group and 5.0% and 9.1% in the bilateral group (p = 0.861). These data suggest that simultaneous bilateral inguinal herniorrhaphy does not result in increased rates of most postoperative complications or recurrence when compared with unilateral repair.

Female↗