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Biomedical subjects

D Wolfe

Publications and source records attributed to D Wolfe.

At least 55 records · Page 3Linked to original sources
PubMed1994

Pathogenesis of spinal cord injury during simulated aneurysm repair in a chronic animal model.

The pathogenesis of paraplegia after repair of thoracic aortic aneurysms is controversial. Using direct spinal cord evoked potential monitoring, critical intercostal arteries (CICA) were identified to evaluate the impact of backbleeding and ligation versus that of preservation during simulated aneurysm repair. Thirty pigs (40 kg) were randomly assigned to one of five groups. In groups 1 through 4, a thoracic segment containing CICA was cross-clamped for 60 minutes and distal aortic perfusion was provided by a centrifugal pump. In groups 1 and 2, the thoracic segment was vented, maintaining segment pressure at 0 mm Hg; CICA were ligated in group 1 and preserved in group 2. Thoracic segment was perfused at 70 mm Hg in groups 3 and 4; CICA were ligated in group 3 and preserved in group 4. Critical intercostal artery ligations were performed at the end of the cross-clamp period. In group 5 simple cross-clamping at the left subclavian artery was performed as a control. The combination of venting and ligation of CICA correlated with impaired neurologic outcome according to Tarlov's score (median, 1.5 in group 1 versus 3 in group 2; p = 0.015), indicated by a significant difference in median values of direct spinal cord evoked potential amplitude (expressed as a fraction of baseline values) at 120 minutes after cross-clamping (0.76 in group 1 versus 0.98 in group 2; p = 0.0082).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Comparison of retrograde cerebral perfusion to antegrade cerebral perfusion and hypothermic circulatory arrest in a chronic porcine model.

Retrograde cerebral perfusion (RCP) is a new method of cerebral protection that has been touted as an improvement over hypothermic circulatory arrest (HCA). However, RCP has been used clinically for durations and at temperatures that are "safe" for HCA alone. This study was designed to compare RCP to HCA and antegrade cerebral perfusion (ACP) deliberately exceeding "safe" limits, in order to determine unequivocally whether RCP provides better cerebral protection than HCA. Four groups of six Yorkshire pigs (20 to 30 kg) were randomly assigned to undergo 90 minutes of RCP, ACP, HCA, or HCA with heads packed in ice (HCA-HP) at an esophageal temperature of 20 degrees C. Arterial, mixed venous and cerebral venous oxygen, glucose and lactate contents; quantitative EEG; were monitored at baseline (37 degrees C); at the end of cooling cardiopulmonary bypass (20 degrees C); during rewarming (30 degrees C); and at two and four hours post intervention. Animals were recovered and were evaluated daily using a quantitative behavioral score (0 to 9). Mean behavioral score was lower in the HCA group than in the other three groups at seven days (HCA 5.8 +/- 1.1; RCP 8.5 +/- 0.2; ACP 9.0 +/- 0.0; HCA-HP 8.5 +/- 0.2, p < 0.05). Recovery of QEEG was better in the ACP group than in all others, but the RCP group had faster EEG recovery than HCA alone, although not better than HCA-HP (HCA 15 +/- 4; RCP 27 +/- 3; ACP 78 +/- 5; HCA-HP 19 +/- 3, p < 0.001). However, histopathological evidence of ischemic injury was present in 5 of 6 HCA animals and also in 4 of 6 of the HCP-HP group, but only in 1 of 6 RCP animals and in none of the ACP group. This study demonstrates that ACP affords the best cerebral protection by all outcome measures, but RCP provides clear improvement compared to HCA.

Animals↗
PubMed1994

The epidemiology of Lyme disease in Delaware 1989-1992.

OBJECTIVES: The study was conducted to describe the temporal, geographic, demographic and treatment characteristics of Lyme disease in Delaware and to assist health planners in developing and implementing control strategies. METHODS: All physician-submitted Centers for Disease Control and Prevention (CDC) follow-up Lyme disease report forms from 1989 through 1992 were reviewed for completeness. Data were gathered from completed forms only. All cases were classified according to the 1990 CDC surveillance case definition. Cases were further subdivided into two groups. Antibiotic usage patterns were then identified for each group. Data on the percentage of infected ticks by county were obtained from a 1988 study conducted by the University of Delaware; Delaware Health and Social Services, Division of Public Health; and the Department of Natural Resources and Environmental Control. RESULTS: Reported cases of Lyme disease increased 246 percent between 1989 and 1992. The 1992 statewide incidence rate was 12.6 cases per 100,000 population. Whites were four times more likely to contract Lyme disease than were blacks. The majority of cases were reported between June and October. The number of patients being treated with oral antibiotics for localized disease for three weeks or longer increased from 52 percent in 1991 to 94 percent in 1992. Ixodid ticks infected with Borrelia burgdorferi were found in all three counties. CONCLUSION: The Delaware State Board of Health made Lyme disease reportable in September 1989. This requirement increased the quality of Lyme disease surveillance; however, the disease is probably under-reported since Delaware does not actively solicit Lyme disease reports. Delaware's case data reflect national data which indicate an increase in reported cases. A trend toward longer duration of treatment for localized Lyme disease is evident.

Adolescent↗
PubMed1993

Secretion of PGF2alpha and oxytocin during hyperthermia in cyclic and pregnant heifers.

The effects of acute heat stress (HS) and oxytocin (OT) injection on plasma concentrations of PGF2alpha and OT were examined in cyclic (C; n = 15) and pregnant (P; n = 11) dairy heifers. On Day 17 of synchronized estrous cycles, animals were randomly assigned to either thermoneutral (TN; 20 degrees C, 20% RH) or HS (42 degrees C, 60% RH) chambers. The jugular vein of each heifer was cannulated and blood samples collected hourly for 4 h, then every 15 min for an additional 3 h. Oxytocin (100 IU) was injected (IV) 5 h after the start of blood collection. Plasma samples were assayed subsequently for concentrations of 13,14-dihydro-15-keto PGF2alpha (PGFM) and OT. During the 7-h experiment, body temperature of HS heifers reached 41.2 degrees C as compared to 38.5 degrees C in control heifers. Plasma concentrations of PGFM increased (P<0.05) and peaked 30 min after OT injection in C (890 pg/ml) and P (540 pg/ml) heifers. In C heifers, heat stress failed to alter PGFM concentrations either before or after OT injection. In the P group, PGFM concentrations following OT injection tended to be higher in HS heifers were further TN heifers (peak values of 690 vs. 410 pg/ml). Pregnant TN and HS heifers were further classified as responders or non-responders to OT challenge according to a cutoff value for PGFM of 193 pg/ml (overall mean of C heifers minus 1 SD). Five of six HS and one of five TN pregnant heifers were classified as responders (P<0.06). Oxytocin concentrations in plasma prior to injection of exogenous OT were not affected by HS or pregnancy status. It is concluded that in C heifers, acute HS in vivo does not cause any further rise in PGF2alpha secretion. However, in P heifers, HS appears to antagonize suppressive effects of the embryo on uterine secretion of PGF2alpha, as indicated by the larger proportion of P heifers responding to OT challenge.

Journal Article↗
PubMed1992

Head-upright tilt-table testing in evaluation and management of the malignant vasovagal syndrome.

Vasovagally mediated cardiac asystole has been proposed as a potential cause of sudden cardiac death. To assess this possibility and identify characteristics that define patients with vasovagally mediated asystole, head-upright tilt-table testing was performed in 50 consecutive patients (26 women and 24 men, mean age 42 +/- 10 years) with recurrent unexplained syncope. The upright tilt-table test was performed in the fasting state for 30 minutes, with or without the use of intravenous isoproterenol (1 to 3 micrograms/min). The production of ventricular asystole lasting greater than 4 seconds was considered a positive result. All patients with tilt-induced asystole received therapy with either beta blockers, disopyramide, transdermal scopolamine or atrioventricular permanent pacing, the efficacy of which was evaluated with serial tilt-table tests. Reproducible tilt-induced asystole occurred in 10 patients (7 men and 3 women, mean age 23 +/- 12 years) (7 patients during baseline tilt, and 3 during isoproterenol infusion). Analysis of this group revealed that they had significantly more frequent and severe syncopal episodes (3 patients had episodes needing bystander cardiopulmonary resuscitation) than did those patients with tilt-induced syncope without asystole. All patients who had tilt-induced asystole eventually became tilt-table negative with therapy (4 with beta blockers, 2 with disopyramide, and 4 with atrioventricular permanent pacing), and over a mean follow-up of 21 +/- 6 months no further syncopal episodes occurred. It is concluded that patients with recurrent tilt-induced asystole represent a distinct subgroup that has recurrent severe syncope that may mimic or result in sudden cardiac death. Thus, the predischarge electrophysiologic study could predict late outcome with recurrence of preexicitation or supraventricular tachycardia in patients who had undergone surgical ablation of the accessory pathway with an overall predictive accuracy of 95% (107 of 113 patients), negative predictive value of 96% (103 of 107), and positive predictive value of 67% (4 of 6).

Adolescent↗
PubMed1992

Recurrent unexplained syncope in the elderly: the use of head-upright tilt table testing in evaluation and management.

OBJECTIVE: To investigate the usefulness of head-upright tilt table testing for vasovagal episodes in the evaluation and management of elderly patients with recurrent idiopathic syncope. DESIGN: Prospective survey. SETTING: Electrophysiology laboratory of a university hospital. PATIENTS: Twenty-five patients (11 male, 14 female; mean age 73 +/- 6 years) with recurrent unexplained syncope and seven control subjects with other causes of syncope (4 male, 3 female; mean age 70 +/- 4 years). METHODS: Each patient underwent head-upright tilt table testing for 30 minutes with or without an infusion of isoproterenol (1-3 micrograms/min given intravenously) in an attempt to provoke bradycardia, hypotension, or both. MAIN RESULTS: Syncope occurred in nine patients (36%) during the baseline tilt and in seven patients (28%) during isoproterenol infusion (total positives 64%). None of the controls had syncope during the test. All of the patients who had positive test results eventually became tilt table negative with therapy, and over a mean follow-up period of 24 months, no further syncopal episodes have occurred. CONCLUSIONS: Head-upright tilt table testing combined with isoproterenol infusion may be a useful tool in the diagnosis of vasovagal syncope in the elderly and in the evaluation of preventive therapy.

Aged↗
PubMed1992

Reproducibility of head upright tilt table test results in patients with syncope.

Head upright tilt table testing is a promising technique for the evaluation and management of vasovagal (neuroregulatory) syncope. In order to determine the day-to-day reproducibility of results using this technique we performed head upright tilt table testing (with or without graded isoproterenol infusion) in 21 patients (12 males, 9 females, mean age 34 +/- 19.1 years). During the first tilt study a total of 14 patients experienced syncope (six during baseline tilt, mean tilt time 15.8 +/- 7 minutes, eight following tilt with graded isoproterenol infusion, mean tilt time 17.7 +/- 9 minutes) while seven were negative. During the second tilt study (performed 3-7 days following the first study) the results of the first study were duplicated in 19 patients (90%) (six during baseline tilt, mean time 17.5 +/- 8 minutes, eight following graded isoproterenol infusion, mean time 15.9 +/- 7 minutes), however the level of provocation required to provoke syncope differed from that needed in the initial test in five patients (24%). We conclude that the results of head upright tilt table testing with graded isoproterenol infusions can be duplicated in 90% of patients, although some day-to-day variability exists in the degree of provocation necessary to elicit a positive response.

Adult↗
PubMed1992

The use of head-upright tilt table testing in the evaluation and management of syncope in children and adolescents.

Recurrent syncope in an otherwise healthy child or adolescent is a common anxiety provoking disorder. Vasovagally mediated hypotension and bradycardia are believed common, yet difficult to diagnose, causes of syncope in this age group. Upright tilt table testing has been suggested as a potential method to test for vasovagal episodes. This study evaluated the utility of this technique in the evaluation and management of recurrent syncope in children and adolescents. Thirty patients with recurrent unexplained syncope were evaluated by use of an upright tilt table test for 30 minutes, with or without an infusion of isoproterenol (1 to 3 micrograms/min given intravenously), in an attempt to produce hypotension, bradycardia, or both. There were 15 males and 15 females, mean age 14 +/- 6 years. Each of the tilt positive patients received therapy with either fluorohydrocortisone, beta blockers, or transdermal scopolamine. Syncope occurred in six patients (20%) during the base line tilt and in 15 patients (50%) during isoproterenol infusion (total positives 70%). All initially positive patients were rendered tilt negative by therapy. Over a mean follow-up period of 20 months, no further episodes have occurred. We conclude that tilt table testing is a useful and effective test in the evaluation of unexplained syncope in childhood.

Adolescent↗
PubMed1992

Head-upright tilt-table testing: a useful tool in the evaluation and management of recurrent vertigo of unknown origin associated with near-syncope or syncope.

Recurrent idiopathic vertigo associated with near-syncope and syncope is a common perplexing problem, some cases of which are considered autonomically mediated (vasovagal). Upright-tilt-table testing has emerged as a potential method to test for vasovagal episodes. This study evaluated the use of this technique in the evaluation and management of patients with recurrent idiopathic vertigo associated with near-syncope or syncope. Twenty-one patients with recurrent unexplained vertigo and syncope/near-syncope and 11 control subjects were evaluated by use of an upright-tilt-table test for 30 minutes, with or without a graded isoproterenol infusion (1 to 4 micrograms/min given intravenously), in an attempt to provoke hypotension, bradycardia, or both, which reproduced the patient's symptoms. The patients included 10 men and 11 women (mean age, 51 +/- 16 years). Eleven controls with no history of vertigo were also studied. Transcranial Doppler sonography was used to assess cerebral arteriolar blood flow during tilt. All tilt-positive patients were placed on therapy with either beta-blockers, disopyramide, or transdermal scopolamine, the effectiveness of which was determined with another tilt-table study. Symptoms occurred in seven patients (33%) during the baseline tilt and in eight patients (38%) during isoproterenol infusion (total positives, 71%). Transcranial Doppler sonography demonstrated a 225% +/- 192% increase in pulsatility index and a 70% +/- 29% increase in resistance index (indicative of cerebral arteriolar vasoconstriction) at the time of vertigo. No control subject experienced syncope during this test. Each tilt-positive patient eventually became tilt-negative with therapy, and over a mean follow-up period of 26 months, no further episodes have occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Pulmonary hypertension and human immunodeficiency virus infection. Two reports and a review of the literature.

Pulmonary hypertension may be primary (idiopathic) or secondary. While the etiologies for secondary pulmonary hypertension are diverse, infection with the human immunodeficiency virus (HIV) has not been included. To date there have been 16 reported cases of pulmonary hypertension in the HIV-infected population. Plexogenic arteriopathy was the most common pathologic finding. We report two HIV-infected patients who were concomitantly found to have pulmonary hypertension with plexogenic arteriopathy. One patient had lymphocytic interstitial pneumonitis, an entity not previously associated with pulmonary hypertension. We review the 16 previous cases of pulmonary hypertension and HIV infection and discuss this association.

Adult↗