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Biomedical subjects

G B Russell

Publications and source records attributed to G B Russell.

At least 55 records · Page 3Linked to original sources
PubMed1995

The microcirculatory effects of peripheral sympathectomy.

Microvascular physiology following peripheral artery sympathectomy was evaluated in seven hands with refractory pain (n = 7) and ulceration (n = 7) by serial isolated cold stress testing, which measures digital temperature and cutaneous perfusion (laser Doppler fluxmetry). All patients (n = 6) had vasospasm (secondary Raynaud's phenomenon) and arteriographically proven digital and palmar occlusive disease. Microcirculatory flow responses were correlated with symptoms and signs (including ulcer healing) before and after (2-8 weeks, 12-15 weeks, and 24 weeks) peripheral sympathectomy. Baseline data were compared with those of controls (n = 7 extremities). Following surgery, all seven hands had diminished pain; six had ulcer healing and one had ulcer reduction. Isolated cold stress testing demonstrated abnormalities in temperature and laser Doppler fluxmetry response between patients and controls. Although total flow (reflected by temperature) was not significantly increased after surgery, peripheral sympathectomy increased nutritional flow in these patients with combined vasospastic vessels and occlusive injury. The clinical changes observed following peripheral sympathectomy appear to be related to postsurgical correction of abnormal arteriovenous shunting and to improved nutritional blood flow to ischemic areas. This accounts for the resultant diminution of pain and healing of ulcers observed in these patients after surgery.

Adult↗
PubMed1995

The arterial to end-tidal carbon dioxide difference in neurosurgical patients during craniotomy.

PETCO2 is often used as an estimate of PaCO2, with the understanding that PaCO2 usually exceeds PETCO2. During intraoperative craniotomies, because hyperventilation is used to therapeutically lower intracranial pressure, the difference between PaCO2 and PETCO2 (P(a-ET)CO2) has therapeutic implications. The P(a-ET)CO2 was hypothesized to be stable during craniotomies with relatively short-term monitoring and controlled cardiorespiratory variables. Thirty-five patients undergoing elective craniotomies were studied. Arterial blood gases (with PaCO2) were measured after induction of general anesthesia, after cranium opening prior to dural incision, and at start of closure; PETCO2 was simultaneously determined with infrared capnometry. The PaCO2 was 31.9 +/- 3.9 mm Hg (range, 24.8-46.7) (values are mean +/- SD) and PETCO2, 24.7 +/- 3.8 mm Hg (range, 16-34), with a P(a-ET)CO2 of 7.2 +/- 3.3 mm Hg (of 126 comparisons, range was -1.2-17.3). There was no correlation of P(a-ET)CO2 with blood pressure, heart rate, respiratory volumes, airway pressures, or inspired oxygen concentration. There was a significant positive correlation between PaCO2 and PETCO2 (r = 0.632, slope = 0.609) and P(a-ET)CO2 and PaCO2 (r = 0.46, slope = 0.391, P < 0.017, and r2 = 0.22). Although changes in the study population of PaCO2 and PETCO2 correlated statistically (r = 0.818, slope = 0.76, P < 0.001, r2 = 0.669), comparisons in 17 of 35 individuals were not significant. On comparison of subsequent measurements, 18.4% of changes in PaCO2 and PETCO2 (although sometimes small) were in opposite directions. P(a-ET)CO2 did not change with time. The PETCO2 does not provide a stable reflection of PaCO2 in many patients undergoing craniotomies.

Adult↗
PubMed1995

Attenuation of midazolam-induced EEG activation in rats by both flumazenil and hyperbaric oxygen.

Sedative doses of benzodiazepines, i.e., midazolam, can cause electroencephalography (EEG) activation, which is reversed by the benzodiazepine antagonist flumazenil. Hyperbaric oxygen (HBO) can cause acute cerebral toxicity with sensory and motor abnormalities, including seizures. Benzodiazepines are also administered for anxiolysis, sedation, and seizure prophylaxis to patients receiving HBO treatments. Because of possible interactions on monitored neuroelectric activity, we decided to evaluate the effects of midazolam on the EEG and cortical somatosensory evoked potentials (CEPs) in rats exposed to HBO, as well as to compare this to the effects of flumazenil. Thirty-six Sprague-Dawley rats were studied. Analog 2-channel and computerized EEG analysis (compressed spectral array with spectral edge, power spectrum, and power bands) and CEPs were monitored. Studies were divided into two phases. In phase 1, after baseline recordings, 16 rats were randomly assigned to receive midazolam, 0.1 mg.kg-1 intravenously, then compression to 1,824 mm Hg of O2 (n = 8), or 1,824 mm Hg of O2 followed by the midazolam (n = 8). In phase 2, after baseline recordings, rats were randomly assigned to four (n = 5) groups: midazolam, 0.1 mg.kg-1 intravenously, then compression to 1,824 mm Hg of O2; midazolam, then flumazenil, 0.05 mg.kg-1 intravenously; compression, then midazolam; or flumazenil, then midazolam. Recordings of EEG and CEPs were compared by analysis of variance and the Student's t test. In phase 1, midazolam first showed EEG activation in six (75%) rats, which was reversed by HBO. The HBO first activated the EEG in two rats (25%); midazolam then given had no effect. The CEPs were not altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthetics, Intravenous↗
PubMed1995

Differences in anesthetic potency between Sprague-Dawley and Long-Evans rats for isoflurane but not nitrous oxide.

The mechanisms of action of halogenated (isoflurane) and inorganic (nitrous oxide (N2O)) anesthetic gases are postulated to differ. We tested the null hypothesis that there is no difference in anesthetic potency, as determined by MAC (the minimum alveolar anesthetic concentration preventing purposeful movement to supramaximal noxious stimulation in 50% of animals) between the Long-Evans (LE) and Sprague-Dawley (SD) rat strains for isoflurane and N2O. MAC values were determined using a 45-second standard supramaximal electrical stimulation. MAC of isoflurane for SD rats was 1.28 +/- 0.20 vol% (mean +/- standard deviation), but 0.98 +/- 0.14 vol% for LE rats (p = 0.001). MAC values for N2O were the same: 1.53 +/- 0.1 and 1.58 +/- 0.14 ata for SD and LE rats, respectively. The interstrain MAC difference for isoflurane, but not N2O, suggests different mechanisms of action for the two agents.

Anesthesia, Inhalation↗
PubMed1995

Role of social class in excess black stroke mortality.

BACKGROUND AND PURPOSE: It has been suggested that a substantial proportion of the excess stroke mortality among black Americans may be attributable to relatively lower socioeconomic status (SES) in this group. In this report we provide the first quantitative estimates of the proportion of excess black stroke mortality attributable to SES for a large population-based cohort. METHODS: We used data from the National Longitudinal Mortality Study for persons 45 years and older (73,400 white men, 87,528 white women, 6522 black men, and 8816 black women). Sex-specific proportional hazards model were used to estimate excess black stroke mortality with and without adjustment for education and income (measures of SES). The contribution of SES to the excess black stroke risk was estimated from the difference in regression coefficients for race in these models. RESULTS: In men, low SES was associated with increased stroke mortality (P < or = .0001) and accounted for 14% to 46% of the excess black stroke risk (P < .05). However, we could find no association between SES and stroke mortality in women, and SES did not account for a significant proportion of the excess stroke mortality in black women. CONCLUSIONS: Although SES proved to account for a statistically significant proportion of excess male black stroke mortality, overall SES explained less than one quarter of the observed excess between ages 45 and 65. In women, SES did not significantly reduce the estimated excess black stroke mortality. Although SES may be playing a role in excess black stroke mortality, a substantial proportion of the excess appears attributable to other sources, including cerebrovascular risk factors that are unrelated to SES, unmeasured lifestyle influences, social resources, and genetic factors.

Black or African American↗
PubMed1995

A re-evaluation of the protein and lysine requirement for broiler breeder hens.

An experiment was conducted with 32-wk-old Arbor Acres broiler breeder hens to determine their requirement for Lys and protein. Diets were fed with Lys levels ranging from .545 to .380% and with protein levels ranging from 11.46 to 8.90%, respectively. A daily intake of 845 mg of Lys per hen per d was required for maximum egg production, egg mass, and egg content. A daily intake of 18.07 g protein was required with a corn-soybean meal diet containing no supplemental amino acids. However, when Met and Lys were added to the diet, daily protein intakes of 15.53 and 16.37 g supported performance that was not significantly different from performance of hens receiving higher levels of protein.

Animals↗
PubMed1995

Sodium requirement for broiler breeder hens.

Two experiments were conducted with Arbor Acres hens to determine their Na requirement. Sodium chloride was added to a corn-soybean meal diet to furnish daily intakes of 35, 65, 95, 125, and 150 mg per hen in Experiment 1. The 150 mg level was replaced with 180 mg in Experiment 2. The hens were maintained in floor pens with wood shavings used as litter. Experiment 1 was conducted for 9 wk and Experiment 2 for 12 wk. Egg production was significantly reduced during Week 4, when the hens had an intake of 35 mg Na/d. Egg production was reduced by Week 7 when the diet furnished 65 mg/d. Plasma Na was reduced and plasma K increased when the intake was 35 or 65 mg/d. Performance data from 6 to 9, and 6 to 12 wk were used in Experiments 1 and 2, respectively, to determine the daily Na requirement. The daily requirement for maximum production was 113.8 and 96 mg and the requirement for egg mass was 105 and 100 mg in Experiments 1 and 2, respectively.

Analysis of Variance↗
PubMed1995

Re-evaluation of the methionine and protein requirements of the broiler breeder hen.

Three experiments were conducted to study the Met and protein requirements of Arbor Acres broiler breeder hens. Broken line regression analysis in Experiments 1 and 3 indicated the Met requirement was 335 and 323 mg/d, respectively, with a production of a daily egg content (EC) of 42.3 or 43.0 g. A broken line could not be fitted to the data in Experiment 2. Therefore, this procedure could not be used to calculate a requirement. An average of 7.83 mg Met was required to produce 1 g of EC. Using this value, the requirement for the three experiments would be 344 mg at the level of EC produced in these experiments. The requirement would be higher with either a higher rate of lay or with larger eggs.

Analysis of Variance↗
PubMed1995

Correlation of plasma calcium with experimentally elevated cholesterol and triglycerides in laying hens.

An experiment was conducted to determine the relationship between plasma Ca, cholesterol, and triglycerides in commercial laying hens. A 2 x 2 factorial arrangement of treatments was used with two levels of dietary iodine (0 and 5,000 ppm) from KI and two levels of beta-estradiol (0 and 12 mg in a single subcutaneous injection), in a corn oil carrier. Feeding iodine or injecting beta-estradiol resulted in increased plasma Ca, cholesterol and triglycerides. The increases were additive for the two treatments. Plasma Ca and cholesterol was significantly correlated. Plasma Ca was negatively correlated with triglycerides when the hens were injected with beta-estradiol. Cholesterol and triglycerides were correlated when hens were injected with beta-estradiol. However, feeding KI decreased the correlation between Ca and triglycerides, and cholesterol and triglycerides.

Animals↗
PubMed1995

Accuracy of laminated disposable pulse-oximeter sensors.

BACKGROUND: In our hospital, widespread utilization and clinical importance of arterial oxyhemoglobin saturation monitoring by pulse oximetry (SpO2) generated a growing cost-center in a time of fiscal restraint. We hypothesized that lamination of a pulse-oximeter sensor and insertion into a disposable, protective shield allowing reusability would not alter sensor response time or relative accuracy. MATERIALS AND METHODS: Six healthy adult men volunteered to be studied during hypoxemia (induced by spontaneous ventilation of a 8-10% oxygen concentration in helium by face mask) to an SpO2 less than or equal to 70%. The SpO2 was monitored by 2 Nellcor N-200 pulse oximeters with D25II sensors and an Ohmeda 3700 pulse oximeter with the OxyTip sensors. Single desaturations, repeated twice in 5 subjects, and 2 desaturations, repeated 5 times in 1 subject, were evaluated. After the initial desaturation and recovery, 1 D25II sensor was laminated, inserted into a protective sheath, reattached and followed by repeat desaturation. SpO2 readings from each oximeter, during both desaturations sets were compared. Clinical importance was subjectively determined by comparison to published SpO2 bias data. RESULTS: 907 data sets were collected. In 447 SpO2 comparisons in 5 individuals (range 62-100%), 1 laminated sensor was 0.8 percentage points lower and one sensor was 1.3 percentage points higher (P less than 0.05) than controls compared with prelamination differences. No difference was clinically important. In individual repeated desaturations (range, 52-100%) following lamination, one sensor was 2.9 percentage points and one sensor was 2.6 percentage points higher. During repeat desaturations, differences between the OxyTip and the D25II control sensor were 1.3 percentage points lower and 1.8 percentage points higher than the initial desaturation (all p less than 0.001). Response times were not altered. CONCLUSIONS: Lamination and protective shield applied to disposable sensors did not alter SpO2 measurements or response times to incremental reductions in SpO2 in a clinically important manner.

Adult↗
PubMed1995

Comparison of anesthesia induced by ketamine-fentanyl combination and maintained by propofol or etomidate in New Zealand white rabbits.

Ketamine-fentanyl-propofol and ketamine-fentanyl-etomidate combinations were administered intravenously to four groups of rabbits. Each group received ketamine (30 mg/kg of body weight) and fentanyl (0.025 mg/kg) for anesthesia induction. Either propofol or etomidate was administered by an infusion pump to maintain anesthesia. The rabbit's responses to noxious stimuli were determined before anesthesia was induced and at 10-min intervals thereafter until the rabbit recovered. The effects of the anesthetic combinations on the cardiopulmonary system were measured by monitoring respiratory and heart rates, blood pressure, and arterial blood gas tensions. Etomidate infused at the rate of 0.2 or 0.1 mg/kg/min could maintain surgical anesthesia with fewer effects on the cardiopulmonary system for 40 and 30 min respectively. However, the high mortality and side effects such as hemolysis in these two groups preclude the clinical use of etomidate for anesthesia maintenance. Propofol administered intravenously at rates of 0.8 and 0.4 mg/kg/min could maintain surgical anesthesia for 40 and 30 min respectively. However, relatively severe hypotension, hypercapnia, and respiratory acidosis were associated with this drug. Recovery from the propofol infusion was very rapid. Ketamine-fentanyl-etomidate combination is not recommended for clinical anesthesia in rabbits. Ketamine-fentanyl-propofol combination at a dosage of 30-0.025-0.4 mg/kg/min can be safely used for short-term surgery.

Anesthesia, Intravenous↗
PubMed1994

Relationship of DNA ploidy to histology and prognosis in rhabdomyosarcoma. Comparison of flow cytometry and image analysis.

BACKGROUND: Although DNA ploidy correlates with prognosis in certain childhood cancers, e.g., neuroblastoma, its significance in rhabdomyosarcoma (RMS) is unclear and controversial. METHODS: Ploidy by flow cytometry (FCM) and image analysis (IA) in 26 of 27 children with RMS (17 embryonal, 3 mixed embryonal/alveolar, 5 alveolar, 1 anaplastic, 1 ectomesenchymoma) and 4 adults with pleomorphic RMS were evaluated. Statistical comparisons were analyzed between DNA content and gender, age, localization, Intergroup Rhabdomyosarcoma Study (IRS) group, and histopathologic subtype. Survival analyses were performed by the Kaplan-Meier test using the approximate chi-square statistic for the log rank test. RESULTS: The concordance rate between FCM and IA was 26 of 30 (87%); FCM was not performed in one tumor. Image analysis was more sensitive than FCM in detecting aneuploidy. Furthermore, DNA content was associated significantly with histologic subtype (P = 0.031); embryonal histology commonly was hyperdiploid (mean, 1.44; median, 1.27), whereas alveolar histology usually was near-tetraploid (mean, 1.83; median, 1.95). All four adult patients with pleomorphic RMS were aneuploid, with one showing multiple DNA peaks. No correlation between DNA content and survival was observed in the children with RMS. However, IRS group (P = 0.011) and patient age (P = 0.036) were independent prognostic indicators significantly related to survival. All adult patients died of their disease. CONCLUSIONS: Although ploidy correlates with histologic subtype, DNA content is not significantly predictive of prognosis in patients with RMS. Age at diagnosis and IRS group are independent predictors of clinical outcome in children with RMS.

Adolescent↗
PubMed1994

Preservation of neurogenic motor-evoked potentials during isoflurane electroencephalographic burst suppression in rats.

STUDY DESIGN: A prospective laboratory study was performed in a rat model. OBJECTIVES: To test the hypothesis that neurogenic motor-evoked potentials are more resistant to suppressive changes from the volatile anesthetic isoflurane than cortically recorded somatosensory-evoked potentials and electroencephalography. SUMMARY OF BACKGROUND DATA: Techniques for monitoring spinal cord motor tracts have been developed because sensory tract monitoring with somatosensory-evoked potentials is at times inadequate. Potentials from transcranial magnetic and electrical stimulation are very sensitive to anesthesia. Neurogenic motor-evoked potentials are thought to be more resistant. METHODS: Eight mature Sprague-Dawley rats were studied during isoflurane general anesthesia. Two-channel raw and computer-processed electroencephalograms, somatosensory-evoked potentials, and neurogenic motor-evoked potentials were recorded at six levels of anesthetic depths. RESULTS: Neurogenic motor-evoked potential amplitudes and latencies were unaltered. The electroencephalograms were depressed to isoelectricity with periodic burst activity above 1.27% isoflurane. Processed electroencephalograms showed depression above 0.72%. The somatosensory-evoked potentials were suppressed by increasing isoflurane and were not discernible at 2.2%. CONCLUSIONS: Neurogenic motor-evoked potential signals are well preserved in rats during exposure to isoflurane concentrations that eliminate somatosensory-evoked potential waveforms and depress electroencephalograms to burst suppression.

Animals↗
PubMed1994

A rabbit ear model for cold stress testing.

A rabbit ear model resembling the human digit was studied to determine the vascular response of the rabbit ear to a cold stress. Following moderate cooling (10 minutes at 5 degrees - 8 degrees C), auricular blood flow and cutaneous perfusion were reduced. This decrease was reversed by 30 minutes of warming. The response in the rabbit ear to cold stress is similar to that of normal human digits. The similarities between the control of the circulation in human digits and rabbit ears may result from the similarities in digital and auricular vascular receptors and receptor subtypes. Verification of the rabbit model provides an experimental method for obtaining important data regarding digital pathophysiology and the treatment of cold intolerance. Further study with this model will provide clinically relevant information regarding the pathophysiology of digital thermoregulatory abnormalities.

Animals↗
PubMed1994

Reliability of the arterial to end-tidal carbon dioxide gradient in mechanically ventilated patients with multisystem trauma.

The accuracy and reliability of the relationship between arterial and end-tidal carbon dioxide (PETCO2 and PaCO2), expressed as the gradient, P(a-ET)CO2, was assessed with 171 comparisons in nine mechanically ventilated trauma patients. The P(a-ET)CO2 was 14 +/- 11 mm Hg. (mean +/- standard deviation.) The positive correlation between PaCO2 (44 +/- 10 mm Hg) and PETCO2 (30 +/- 10 mm Hg) for the study population (reflected by r = 0.64, p = 0.001; but r2 = 0.41) indicated statistical significance, but only 40% of the changes reflected a linear relationship. Seventy-eight percent of individual patients had significant correlations of PaCO2 and PETCO2 (p < 0.02 to p < 0.001). Changes in PETCO2 erroneously predicted the PaCO2 changes in 27% of comparisons with 15% false decreases and 12% false increases. Trends in P(a - ET)CO2 magnitude are not reliable, and concordant direction changes in PETCO2 and PaCO2 are not assured.

Adult↗
PubMed1994

The relationship of egg cholesterol to serum cholesterol, serum calcium, feed consumption, and dietary cholecalciferol.

Hy-Line W36 hens, 20 wk of age, were randomly assigned to one of three dietary treatments consisting of cholecalciferol at (0, 550, or 2,750 IU/kg of finished feed). Serum calcium and cholesterol, yolk cholesterol, and egg specific gravity were measured. Feed consumption, egg production, and egg weight measurements were also recorded. Feed consumption, egg production, and egg weights were initially reduced when cholecalciferol was omitted from the diet. These effects disappeared by the beginning of the fourth 28-d period. Egg cholesterol concentrations among treatments followed no consistent pattern. A positive correlation was noted between serum calcium and serum cholesterol.

Animals↗
PubMed1994

Long-term systemic hemodynamic effects of cotinine in rats.

Cigarette smoking has been epidemiologically correlated with lower BP in humans, despite the acute BP effects of nicotine. Cotinine, a primary metabolite of nicotine, has been suggested as a mediator of the BP-lowering effect of smoking. To determine the cardiovascular effects of cotinine itself, arterial BP was monitored continuously in chronically instrumented Sprague-Dawley rats before, during, and after 14 days of intraarterial (i.a.) infusion of cotinine or placebo. Cardiovascular data were collected and analyzed by microcomputer for diurnal changes and for light- and dark-cycle averages. Heart rate (HR) was higher in both precotinine and placebo groups during the dark cycle than during the light cycle. HR was significantly lower (p < 0.025) during cotinine infusion in the cotinine group as compared with placebo. Five days after cotinine infusion, however, HR was not different from that of placebo controls. Arterial BP was not different between cotinine- and placebo-treated rats at any time period. The difference between HR but not arterial BP suggested that baroreceptor activity might differ after cotinine administration. Baroreceptor activity, assessed by analysis of HR changes evoked by phenylephrine, did not differ before and during cotinine administration, however. We conclude that cotinine did not decrease BP in rats under the present experimental conditions, but that cotinine was probably responsible for the observed bradycardia.

Animals↗