Greater Mean Increase Research Articles

Muscle afferent and central command contributions to the cardiovascular response to isometric exercise of postural muscle in patients with mild chronic heart failure

The roles of muscle afferent activity and central drive in controlling the compromised cardiovascular system of patients with mild chronic heart failure (CHF) during isometric exercise were examined. Blood pressure and heart rate responses were recorded in eight stable CHF patients (ejection fraction 20-40%; age 62+/-11 years) and in nine healthy age-matched controls during voluntary and electrically evoked isometric plantar flexion and subsequent post-exercise circulatory occlusion (PECO). During voluntary contraction, control subjects had a greater mean increase in systolic blood pressure than patients (42.4+/-19.2 and 23.0+/-10.9 mmHg respectively; P<0.01), but this was not the case during PECO. During electrically evoked contraction, but not during PECO, the CHF group had smaller (P<0.05) mean increases in both systolic and diastolic blood pressure than controls (13.0+/-5.3 compared with 25.4+/-14.0 mmHg and 7.6+/-3.0 compared with 12.9+/-7.2 mmHg respectively). Intra-group comparison between responses to voluntary and electrically evoked contractions revealed greater (P<0.05) mean increases in systolic and diastolic blood pressure during the voluntary contraction in both the patients and the control subjects. These data suggest that muscle afferent drive to the pressor response from the triceps surae is low in this age group, both in control subjects and in CHF patients. Additionally, the patients may have a relatively desensitized muscle mechanoreceptor reflex.

Simulating the effects of climate change on the carbon balance of North American high-latitude forests.

The large magnitude of predicted warming at high latitudes and the potential feedback of ecosystems to atmospheric CO2 concentrations make it important to quantify both warming and its effects on high-latitude carbon balance. We analysed long-term, daily surface meteorological records for 13 sites in Alaska and north-western Canada and an 82-y record of river ice breakup date for the Tanana River in interior Alaska. We found increases in winter and spring temperature extrema for all sites, with the greatest increases in spring minimum temperature, average 0.47 °C per 10 y, and a 0.7-day per 10 y advance in ice breakup on the Tanana River. We used the climate records to drive an ecosystem process model, BIOME_BGC, to simulate the effects of climate change on the carbon and water balances of boreal forest ecosystems. The growing season has lengthened by an average of 2.6 days per 10 y with an advance in average leaf onset date of 1.10 days per 10 y. This advance in the start of the active growing season correlates positively with progressively earlier ice breakup on the Tanana River in interior Alaska. The advance in the start of the growing season resulted in a 20% increase in net primary production for both aspen (Populus tremuloides) and white spruce (Picea glauca) stands. Aspen had a greater mean increase in maintenance respiration than spruce, whereas spruce had a greater mean increase in evapotranspiration. Average decomposition rates also increased for both species. Both net primary production and decomposition are enhanced in our simulations, suggesting that productive forest types may not experience a significant shift in net carbon flux as a result of climate warming.

The Jarisch-Herxheimer Reaction and Fetal Monitoring Changes in Pregnant Women Treated for Syphilis

In Brief Objective To estimate the incidence of the Jarisch-Herxheimer reaction in pregnant women undergoing treatment of syphilis and the incidence of changes in uterine activity or fetal heart rate (FHR). Methods Pregnant women of at least 24 weeks' gestation diagnosed as needing treatment of syphilis were reviewed retrospectively. Patients were admitted for their first dose of benzathine penicillin, and the FHR was recorded continuously before and for 24 hours after injection. The occurrence of the Jarisch-Herxheimer reaction was noted, and all available FHR records for this admission were reviewed. Evaluations for changes in the FHR pattern and uterine activity were made. Statistical comparisons used Student t, Fischer exact, and χ2 tests, when applicable (significance P < .05). Results We reviewed 50 charts and 31 available FHR records. The average gestational age was 30.8 weeks. We found 20 cases of probable Jarisch-Herxheimer reaction (40%). Thirteen of 31 patients (41.9%) developed regular uterine contractions, median onset, 10 hours. All resolved within 24 hours of treatment. Patients with uterine contractions had a greater mean increase in temperature (1.15F versus 0.68F, P < .008). Twelve of 31 women (38.7%) developed recurrent variable decelerations, median onset, 8 hours. All patients but one had their contractions resolve within 24 hours of treatment. Lower gestational age was associated with the occurrence of recurrent variable decelerations (29.6 weeks versus 32.3 weeks, P < .05). No patients required delivery at the time of treatment. Conclusion The incidence of Jarisch-Herxheimer reaction in treated syphilitic pregnancies is about 40%; similar proportions of patients develop regular uterine contractions and recurrent variable decelerations. The treatment of syphilis with penicillin after 24 weeks' gestation can result in the Jarisch-Herxheimer reaction, uterine contractions, or variable decelerations in a substantial proportion of cases.

The Jarisch-Herxheimer reaction and fetal monitoring changes in pregnant women treated for syphilis

Objective: To estimate the incidence of the Jarisch-Herxheimer reaction in pregnant women undergoing treatment of syphilis and the incidence of changes in uterine activity or fetal heart rate (FHR). Methods: Pregnant women of at least 24 weeks’ gestation diagnosed as needing treatment of syphilis were reviewed retrospectively. Patients were admitted for their first dose of benzathine penicillin, and the FHR was recorded continuously before and for 24 hours after injection. The occurrence of the Jarisch-Herxheimer reaction was noted, and all available FHR records for this admission were reviewed. Evaluations for changes in the FHR pattern and uterine activity were made. Statistical comparisons used Student t, Fischer exact, and χ 2 tests, when applicable (significance P < .05). Results: We reviewed 50 charts and 31 available FHR records. The average gestational age was 30.8 weeks. We found 20 cases of probable Jarisch-Herxheimer reaction (40%). Thirteen of 31 patients (41.9%) developed regular uterine contractions, median onset, 10 hours. All resolved within 24 hours of treatment. Patients with uterine contractions had a greater mean increase in temperature (1.15F versus 0.68F, P < .008). Twelve of 31 women (38.7%) developed recurrent variable decelerations, median onset, 8 hours. All patients but one had their contractions resolve within 24 hours of treatment. Lower gestational age was associated with the occurrence of recurrent variable decelerations (29.6 weeks versus 32.3 weeks, P < .05). No patients required delivery at the time of treatment. Conclusion: The incidence of Jarisch-Herxheimer reaction in treated syphilitic pregnancies is about 40%; similar proportions of patients develop regular uterine contractions and recurrent variable decelerations.

Phacoemulsification with aspirated or retained Viscoat

Endothelial cell counts, morphology, and 24-hour postoperative intraocular pressure (IOP) changes were measured in 55 consecutive patients (60 eyes) who had uncomplicated phacoemulsification and posterior chamber lens implantation with either aspirated (30 eyes) or retained (30 eyes) Viscoat® (sodium chondroitin sulfate-sodium hyaluronate). The surgical technique was standardized in all cases. Endothelial cell loss was almost identical in the aspirated and in the retained groups (8.8% and 8.7%). Postoperative pleomorphism was significantly less in the retained Viscoat group than in the aspirated group, suggesting a possible protective effect of the retained viscoelastic. Corneal thickness increased significantly in the retained Viscoat group, but this was not significant clinically. The retained Viscoat group had more patients with a postoperative IOP greater than 30 mm Hg and a greater mean increase in postoperative IOP, although the difference between the groups was not significant. The IOP changes may have been caused by blockage of the trabecular meshwork by the retained Viscoat. The results suggest that Viscoat can be retained after cataract surgery if the surgeon is prepared for a greater 24-hour postoperative increase in IOP.

Analysis of coronary blood flow velocity dynamics in angiographicaily normal and stenosed arteries before and after endolumen enlargement by angioplasty

Objectives. This study was designed to assess whether the spectral waveform of coronary velocity on Doppler study is characteristically altered in the presence of significant stenosis with normalization of the spectral waveform after relief of endolumen obstruction.Background. Although coronary flow reserve determinations have provided physiologic information complementary to the angiographic percent diameter narrowing, flow velocity measurements have been limited to proximal arteries with inconsistent results after angioplasty. A 12-MHz Doppler guide wire permits flow velocity determination in the proximal and distal coronary artery with fast Fourier spectral analysis.Methods. With the Doppler guide wire, proximal arterial flow velocity and flow reserve measurements in 17 angiographically normal arteries were compared with measurements in 29 significantly stenosed arteries. Proximal and distal flow velocity measurements were also obtained before and after angioplasty of the 29 abnormal arteries. Velocity spectrum was digitized to compute peak diastolic velocity, peak systolic velocity, mean velocity, diastolic/systolic velocity ratio and first third and first half flow fraction.Results. Compared with proximal stenosed arteries, proxtmal normal arteries had significantly higher peak diastolic velocity (64 ± 26 cm/s vs. 41 ± 26 cm/s) and higher coronary vasodilator reserve (2.3 ± 0.8 vs. 1.6 ± 0.7). Normal arteries had higher flows in the first third and first half of the coronary cycle (46 ± 3% vs. 39 ± 7% and 65 ± 2% vs. 56 ± 10%, respectively). Before angioplasty, coronary velocity variables were significantly lower distal than proximal to the stenosis. After angioplasty, there was a greater mean increase in distal velocities (200% vs. 90% for the proximal arteries) that resulted in near equalization of proximal and distal mean velocity and a significant reduction in proximal/ distal mean velocity ratio (2.4 ± 1.7 vs. 1.2 ± 0.4).Conclusions. Before angioplasty, abnormal coronary flow velocity dynamics are more marked distal than proximal to the stenosis. Greater increase in coronary flow velocities in the distal circulation after relief of endolumen obstruction results in a significant reduction in the proximal/distal flow velocity ratio. Thus, normalization of Doppler-derived flow velocity variables with marked reduction of the proximal/distal flow velocity ratios parallels angiographic success and may prove useful as an additional end point measurement in interventional cases with questionable angiographic findings.

Heart rate changes as an autonomic component of the pain response

Autonomic variables have been recommended as measures of the affective-motivational component of the pain response in objective algesimetry. In the present study components of heart rate responses to painful heat stimuli and their relation to stimulus and sensation variables were analyzed. Twelve healthy subjects served. Sixty phasic stimuli of varying temperatures above and below pain threshold were delivered through a Marstock thermode in 1 session. Heart rate, respiration, and subjective stimulus ratings were recorded simultaneously. Phasic heat stimulation above and below pain threshold induced a tonic increase of the heart rate lasting up to more than 20 sec. High intensity stimulation generated steeper rises and greater mean increase than low intensity stimulation. In general, heart rate responses were more closely related to subjective sensation than to stimulus intensity. However, differential temporal analysis demonstrates that, until about 3 sec after stimulation, the autonomic response is determined solely by stimulus temperature, whereas, after approximately 6 sec, it is related only to subjective judgement. Accordingly, the heart rate responses reflect both a brief nocifensive reflex induced by the sensory component and, subsequently, a longer-lasting response which seems to be related to affective and/or cognitive evaluation. This separation of different stages of pain-processing by an autonomic indicator may be useful in clinical algesimetry.

Intravenous pharmacokinetics of 2-hydroxyimipramine in alcoholics and normal controls.

Fifteen subjects (seven recently abstinent, male, chronic alcoholics and eight, age- and weight-matched male controls) were administered 10 mg 2-hydroxyimipramine (2-OHIMI) by intravenous infusion. Pharmacokinetic parameters were determined from multiple blood samples drawn over 60 hours. Total body clearance of unbound drug, as calculated from the plasma concentration versus time data, was significantly increased in the alcoholic group as compared to the control group (3.12 vs 1.51 L/hr/kg). Terminal elimination half-life was decreased in the alcoholics (7.07 vs 10.12 hr). The fraction of the drug unbound to plasma protein was determined by equilibrium dialysis and was found to be decreased in the alcoholic group over that found in the controls (29.8 vs 36.4%). All subjects were monitored by EKG during the first 4 hours of sampling. Although there was a small mean decrease in heart rate following infusion, it did not achieve statistical significance. Alcoholics had a greater mean increase in P-R but not QTc intervals than control subjects, a difference that was significant at 45 minutes and 1 hour postinfusion. There were no significant differences in the percentage of subjects with abnormal P-R or QTc intervals between the alcoholic and control groups.

Urine phthalate determinations as an index of occupational exposure to phthalic anhydride and di(2-ethylhexyl)phthalate.

Although it has been estimated that over 600 000 workers in the United States are exposed to di(2-ethylhexyl)phthalate (DEHP), an animal carcinogen, and that over 100 000 are exposed to phthalic anhydride (PA), few data are available on levels of phthalates in biological fluids of these workers. For a determination of occupational exposure to PA and DEHP at a plant manufacturing DEHP from PA and 2-ethylhexanol, air samples were taken for PA and DEHP, and pre- and postshift urine samples were collected for the determination of total phthalates. Urine samples were obtained from 48 workers in jobs with high exposure to phthalates and from 47 workers in jobs with low exposure. The airborne concentrations of DEHP ranged from 20 to 4 110 micrograms/m3, and the concentrations of PA ranged from 4 to 203 micrograms/m3. The most heavily exposed workers had the highest mean postshift urine phthalate concentration (geometric mean 7.6 nmol/ml) (p = 0.015), and also the greatest mean increase (4.4 nmol/ml) in preshift to postshift urine phthalate levels. Twofold increases over the shift in urine phthalate concentration and postshift phthalate levels of greater than 10 nmol/ml were observed in 8 (25%) of 32 chemical operators, but in none of 52 other workers. These data suggest that measurement of urine phthalate levels may have utility for monitoring the exposure of workers manufacturing or using PA.

Corneal Edema: Iris-Clip Lens Implantation and Simple Intracapsular Extraction Compared

Corneal edema following intracapsular lens extraction and iris-clip lens implantation was compared by assessing corneal thickness and epithelial edema. In a retrospective study the corneal thickness of twenty patients who had intracapsular lens extraction in one eye only was compared with twenty-six patients with iris-clip lens implants in one eye. There was no significant increase in corneal thickness in the operated eye in either group. In a prospective randomized controlled study, a smaller number of patients, had serial measurements of corneal thickness pre- and postoperatively. There was an increase in thickness in the immediate postoperative period for both groups. However, there was no significant difference between eyes which had simple extraction and those which had implants. The implanted eyes however had greater mean increase endothelial trauma in the initial period, compared to eyes with cataract extraction alone.

Arterial blood pressure and the manifestation of atherosclerosis in a rural population of North Bohemia

In a longitudinal epidemiologic study of a North Bohemian rural population, the relationship has been analyzed between arterial blood pressure and the incidence of ischaemic heart disease and other manifestations of arterial and arteriolar disease, as well as the evolution of blood pressure in time in relation to health status. The lowest mean values of systolic and diastolic blood pressure were found both at the initial and follow-up examination in subjects who remained healthy over the 5 years of follow-up. Significantly higher blood pressure values were present even at the first examination in healthy subjects who developed a manifestation of vascular disease, as well as in persons with signs of such a manifestation at entry. The highest blood pressures were seen in those who developed or retained signs of ischaemic heart disease. Similar inter group differences were demonstrated in pulse pressure and in prevalence of hypertension. The mean increase in systolic and diastolic pressure in 5 years was greater in women than in men. In men, subjects who developed or retained other manifestations of vascular disease had a greater mean increase and a greater percentage of “substantial” blood pressure elevations than subjects with ischaemic heart disease. The 5-year follow-up incidence of ischaemic heart disease and other manifestations of arterial and arteriolar disease in both sexes was significantly higher in hypertensives than in normotensives.

Immunologic Reactions Following the Intradermal Inoculation of Influenza A and B Vaccine.

Summary1. Intradermal inoculation into 39 adults of 0.02 ml of concentrated Influenza A and B vaccine gave rise to a mean antibody response (antihemagglutinin) against Influenza B virus which approached that obtained by others following the subcutaneous injection of 1.0 ml of undiluted vaccine. A greater mean increase in antibody against Influenza A was observed in the same group, although this increase could not be attributed conclusively to the effect of the vaccine.2. The intradermal injection of 0.02 ml of concentrated vaccine into 449 adults was followed within 20 minutes by a local erythematous reaction exceeding 10 mm in diameter in 37'3 or 83.1%. In 383 or 85.3% of the same group delayed local erythematous reactions exceeding 10 mm in diameter were present after approximately 48 hours accompanied in many cases by slight induration.3. No correlation could be established between the intensity of the immediate or delayed dermal reaction and the level of antihemagglutinin in the blood.4. Mild systemic...