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Biomedical subjects

L Weaver

Publications and source records attributed to L Weaver.

At least 19 recordsLinked to original sources
PubMed1992

Fluctuation in mixed venous oxygen saturation in critically ill medical patients: a pilot study.

OBJECTIVE: To determine fluctuation in mixed venous oxygen saturation in critically ill medical patients during a period of rest. DESIGN: Nonexperimental, descriptive. SETTING: The medical and coronary intensive care units in a large county hospital in south-central Texas. PATIENTS: Twenty critically ill patients, aged 19 to 85, who had placement of a pulmonary artery catheter capable of continuous monitoring of mixed venous oxygen saturation. The majority had a diagnosis of respiratory failure and required mechanical ventilation. METHODS: Mixed venous oxygen saturation was recorded each minute for a 2-hour period in either early morning or late afternoon hours. Minute-by-minute values obtained during a 30-minute period of rest were used to determine fluctuation. The lowest and highest mixed venous oxygen saturation values during the period were used to calculate percent changes from average values (fluctuation). RESULTS: The range of fluctuation was +/- 6% of the average mixed venous oxygen saturation value for 80% of the sample. Four patients had a greater range of fluctuation: however, their actual mixed venous oxygen saturation values were within a clinically acceptable range. No significant differences in percentage of low or high fluctuation were noted for the following variables: time of day, medication administration, oxygen delivery, oxygen consumption and average mixed venous oxygen saturation. The percentage of low fluctuation was significantly lower for four patients who were not mechanically ventilated. CONCLUSIONS: Knowledge of normal fluctuation enables the care giver to evaluate changes in mixed venous oxygen saturation in response to activities and/or treatments. Additional study of fluctuation in homogenous groups of critically ill patients is warranted.

Adult↗
PubMed1991

Ultrasound-guided hepatic cryosurgery in the treatment of metastatic colon carcinoma. Preliminary results.

Cryosurgery, the in situ freezing of cancer, has been proposed in the past as a possible treatment for unresectable hepatic tumors. Its advantage lies in the fact that it is a very focal treatment sacrificing less normal tissue than surgical resection, allowing treatment of multiple lobes. Because cryosurgery does not affect large vessels, tumors in difficult locations, such as adjacent to the inferior vena cava (IVC), can be treated. With the use of intraoperative ultrasound to place the cryoprobes and monitor the freezing process, 18 patients with unresectable metastatic colon carcinoma confined to the liver were treated. Of the 18 patients treated, 4 (22%) are in complete remission as determined by computed tomography (CT) scans and carcinoembryonic antigen (CEA) levels, with a mean follow-up of 28.8 months. Four patients (22%) were not adequately treated at the time of cryosurgery. The number of lesions frozen in each patient ranged from 1 to 12, with a mean of 6 lesions. Fourteen patients had bilobar disease; three patients had previous right lobectomies with recurrences in their remaining left lobes prior to cryosurgery, and one patient had unilobar disease. Mean survival of the 14 cases with recurrence was 21.4 months, with 2 of the 14 still alive. Ultrasound-guided hepatic cryosurgery appears to be an effective treatment for metastatic colon carcinoma to the liver that is unresectable (including patients with bilobar and multiple lesions). These preliminary results indicate that the procedure warrants further study.

Adult↗
PubMed1991

Outcome of low birth weight infants in a West African village.

Low birthweight (LBW) infants are at risk of increased mortality, impaired growth, and increased morbidity. We studied the progress of all LBW infants (less than 2.5 kg) born in a West African village where there is a resident pediatrician and midwife. There were 426 live births during the 8 years studied of which 42 (10 per cent) were of LBW. There were 17 infant deaths (IMR = 40/1000). Mean birthweight and gestation of infants dying in the first year were significantly lower than those of all live birth (2.33 kg v. 2.99 kg, P less than 0.001; 36.9 w v. 38.9 w, P less than 0.05). The mean weights of the 32 surviving LBW infants (15 preterm, 17 full term, small for gestational age) were compared with those of 32 full term, appropriate for gestational age matched controls over the first year. Growth velocities of paired groups were identical. The significant differences in weight at 1 year (P less than 0.005) reflected those at birth (P less than 0.001). There were no significant differences in clinic attendance rate or incidence of diarrhoea and respiratory disease between the four groups. We conclude that LBW is a strong risk factor for infant mortality, but not for diarrhoeal and respiratory morbidity in a community with ready access to obstetric and pediatric care.

Africa, Western↗
PubMed1989

Synovial fluids from infected joints contain active metalloproteinases and no inhibitory activity.

Serial samples of synovial fluid aspirated from two patients with septic arthritis were assayed for proteinases and proteinase inhibitors. Active metalloproteinases but no proteinase inhibitors were present in all samples taken prior to treatment. The levels of active metalloproteinases fell with time although proenzyme forms were still present in the fluids. Both alpha 2-macroglobulin and the tissue inhibitor of metalloproteinases were found in the septic synovial fluids after treatment commenced. It is proposed that the lack of inhibitors and the presence of active proteinases capable of digesting collagen, gelatin and proteoglycan accounts for the rapid loss of cartilage found in septic arthritis.

Aged↗
PubMed1987

The economic benefit of treating subclinical Streptococcus agalactiae mastitis in lactating cows.

The economic benefits of treating lactating cows for Streptococcus agalactiae mastitis were studied at a large (689 milking cows) central California dairy. Postcure milk production of case cows (infected, treated, and cured) was compared with production of paired control cows (uninfected) and was matched for yield, days in milk, days in gestation, and parity. A simulation was used to plot expected lactation curves for mastitic cows (infected, not treated) with characteristics similar to those of each control cow, and these curves were compared with actual case-cow lactation curves. The difference in actual and expected production was used to calculate net economic benefits of treatment. Comparison of expected with actual production indicated a net benefit from treatment of $396/cow for cows treated in early lactation and $237 for cows treated in midlactation, but a net loss of $55 for cows treated in late lactation. Lactation number did not have a significant impact on economic benefits of treatment. In contrast to other studies indicating no economic benefit from treating mastitis during lactation, this study's positive results may have been attributable to the high cure rate (98%) and the subclinical form of mastitis being treated. Streptococcus agalactiae mastitis treatment during early and midlactation would appear to be an economically justifiable option for dairy managers.

Animals↗
PubMed1987

Cardiovascular effects of afferent renal nerve stimulation.

Electrical stimulation of afferent renal nerves elicits an increase in arterial pressure and heart rate. The hypertensive response is presumably due to the widespread activation of the sympathetic nervous system leading to peripheral vasoconstriction. Interestingly, the kidney does not appear involved in this reflex excitatory response to afferent renal nerve stimulation since changes in vascular conductances and excretory functions are equal in both the innervated and denervated kidney, and secondary to changes in renal perfusion pressure. In addition, no changes in renin release from either kidneys are observed during afferent renal nerve stimulation. It is likely that the electrical stimulation of afferent renal nerves activates other reflexes exerting an inhibitory influence on efferent renal nerve activity. Indeed, neural renorenal reflexes which tonically inhibit renal functions have clearly been demonstrated. Furthermore, preferential inhibition of efferent renal nerve activity by cardiopulmonary and sinoaortic receptors has recently been shown during activation of other visceral afferents.

Afferent Pathways↗
PubMed1985

Reliability of a standardized brief-pulse stimulus in ECT.

The reliability of a standardized brief-pulse stimulus in eliciting a satisfactory convulsive response was evaluated under normal clinical conditions. A total of 89 patients were given 961 initial treatments. Of these, 757 were at the standardized level with a success rate of 89%. A total of 204 trials were given at higher-than-standardized levels. Treating these as standardized level failures, the overall success rate was 70%. The probability that a standardized stimulus given to any patient at any point in the treatment series would be successful was about 7 chances in 10. Implications for the selection of ECT stimuli were discussed.

Adolescent↗
PubMed1979

Histogenesis of the so-called "intravascular bronchioloalveolar tumour".

Three cases of Dial and Liebow's intravascular bronchioloalveolar tumour are described, with emphasis on ultrastructure and histogenesis. The tumour cells are quite different from adjacent reactive alveolar cells and electron microscopy does not support the suggested alveolar cell origin. The tumour cells contain abundant microfilaments, moderate amounts of rough endoplasmic reticulum and varying numbers of Weibel-Palade bodies. With features of smooth muscle, myofibroblast and endothelial cell differentiation, a vascular origin from precursor mesenchymal cells such as the vasoformative reserve cells is suggested.

Adult↗
PubMed1978

The threshold number of pulses in bilateral and unilateral ECT.

Using a low-energy brief-pulse stimulus, the threshold number-of-pulses required to produce a bilaterally manifested tonic-clonic seizure with unilateral and bilateral electrode placement was investigated. Unilateral placement required significantly fewer pulses; bilateral placement resulted in greater post-ictal confusion with no apparent advantage in clinical efficacy. A possible explanation in terms of intracerebral current density is proposed.

Adult↗
PubMed1976

Current density in bilateral and unilateral ECT.

This paper describes a method of computer simulation which will enable the researcher to test, on the theoretical level, the effects of a wide variety of electrode placements, currents, tissue resistivities, and volumetric differences on the distribution of current within the brain. It is based on a nonhomogenous, threesphere model of the head and is capable of expansion to account for known inhomogenities within the brain. It should prove a useful research tool for a wide variety of purposes.

Computers↗
PubMed1975

Utilization of medical services by transferred employees. Differential effect of life change on health.

Some of the health consequences of being transferred to a new job and a new community were examined. The medical records of transferred employees for one year following transfer were compared to the records of a matched control group of more permanently located employees. Because of the authors' clinical observation that an employee's job description was related to the medical response to transfer, the professional and nonprofessional (production and clerical) employees were examined as separate groups. The results demonstrated a greater utilization of health services by transferred nonprofessional, but not by transferred professional employees. The results are discussed in the light of current research in life changes and their relationship to illness.

Adaptation, Psychological↗