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Biomedical subjects

Y David

Publications and source records attributed to Y David.

At least 19 recordsLinked to original sources
PubMed1999

Rectal-scalp temperature difference predicts brain death in children.

When brain death in children occurs, commonly the scalp feels cold despite a normal core temperature. This phenomenon might reflect absent cerebral blood flow and metabolic activity. The authors, therefore, measured rectal-scalp temperature differences in critically ill comatose children to test the hypothesis that a particular temperature difference may correlate with clinical brain death. In a prospective cohort study set in a pediatric intensive care unit, rectal-scalp, rectal-abdomen, and rectal-mastoid temperatures in critically ill comatose children older than 18 months of age were measured before and during brain death evaluations. Twelve children were enrolled. Clinical criteria for brain death were met by seven patients, and five patients survived. All of the seven children who died had rectal-scalp temperature differences greater than 4 degrees C (mean = 6.7, range = 6.0-7.4) at the time of clinical brain death. No survivor had a rectal-scalp temperature difference of 4 degrees C at any time (mean = 3.4, range = 2.9-3.9). Rectal-scalp temperature differences of those who died and those who survived were significantly different at the P < 0.005 level. Rectal-abdomen and rectal-mastoid temperature differences did not correlate with clinical brain death or rectal-scalp temperature difference. In this preliminary study a rectal-scalp temperature difference of greater than 4 degrees C correlates with clinical criteria for brain death in children.

Biomarkers↗
PubMed1998

Resting energy expenditure and nitrogen balance in critically ill pediatric patients on mechanical ventilation.

Nutritional support is important in critically ill patients, with variable energy and nitrogen requirements (e.g., sepsis, trauma, postsurgical state) in this population. This study investigates how age, severity of illness, and mechanical ventilation are related to resting energy expenditure (REE) and nitrogen balance. Nineteen critically ill children (mean age, 8 +/- 6 [SD] y and range 0.4-17.0 y) receiving total parenteral nutrition (TPN) were enrolled. We used indirect calorimetry to measure REE. Expected energy requirements (EER) were obtained from Talbot tables. Pediatric Risk of Mortality (PRISM) and Therapeutic Intervention Scoring System (TISS) score were calculated. Total urinary nitrogen was measured using the Kjeldahl method. PRISM and TISS scores were 9 +/- 5 and 31 +/- 6 points, respectively. REE was 62 +/- 25 kcal.kg-1.d-1, EER was 42 +/- 11 kcal.kg-1. d-1, and caloric intake was 49 +/- 22 kcal.kg-1.d-1. Nitrogen intake was 279 +/- 125 mg.kg-1.d-1, total urinary nitrogen was 324 +/- 133 mg.kg-1.d-1, and nitrogen balance was -120 +/- 153 mg.kg-1.d-1. The protein requirement in this population was approximately 2.8 g.kg-1.d-1. These critically ill children were hypermetabolic, with REE 48% higher (20 kcal.kg-1.d-1) than expected. Nitrogen balance significantly correlated with caloric and protein intake, urinary nitrogen, and age, but not with severity of illness scores or ventilatory parameters.

Adolescent↗
PubMed1998

Resting energy expenditure in children in a pediatric intensive care unit: comparison of Harris-Benedict and Talbot predictions with indirect calorimetry values.

The use of prediction equations has been recommended for calculating energy expenditure. We evaluated two equations that predict energy expenditure, each of which were corrected for two different stress factors, and compared the values obtained with those calculated by indirect calorimetry. The subjects were 55 critically ill children on mechanical ventilation. Basal metabolic rates were calculated with the Harris-Benedict and Talbot methods. Measured resting energy expenditure was 4.72 +/- 2.53 MJ/d. The average difference between measured resting energy expenditure and the Harris-Benedict prediction with a stress factor of 1.5 was -0.98 MJ/d, with an SD delta of 1.56 MJ/d and limits of agreement from -4.12 to 2.15; for a stress factor of 1.3 the average difference was -0.22 MJ/d, with an SD delta of 1.57 MJ/d and limits of agreement from -3.37 to 2.93. The average difference between measured resting energy expenditure and the Talbot prediction with a stress factor of 1.5 was -0.23 MJ/d, with an SD delta of 1.36 MJ/d and limits of agreement from -2.95 to 2.48; for a stress factor of 1.3, it was 0.42 MJ/d, with an SD delta of 1.24 MJ/d and limits of agreement from -2.04 to 2.92. These limits of agreement indicate large differences in energy expenditure between the measured value and the prediction estimated for some patients. Therefore, neither the Harris-Benedict nor the Talbot method will predict resting energy expenditure with acceptable precision for clinical use. Indirect calorimetry appears to be the only useful way of determining resting energy expenditure in these patients.

Adult↗
PubMed1998

Correlation of near infrared spectroscopy cerebral blood flow estimations and microsphere quantitations in newborn piglets.

We compared cerebral blood flow (CBF) estimated using transmission mode near infrared spectroscopy (NIRS) and a modification of the Fick principle with CBF quantitations by radioactive microspheres (MSs) in newborn piglets. Thirteen piglets were studied during steady state, ischemia, and during two reflow periods. NIRS and MS flows were not significantly different during any measurement period. NIRS flows were compared to total brain blood flows and to regional brain blood flows quantitated with MSs and correlated best with temporal cortical flows. Linear regression analysis of the NIRS flows plotted against MS-quantitated temporal cortical flows showed r = 0.71. Thus, CBFs obtained with NIRS were not significantly different from, showed the same directional changes, and correlated acceptably with flows quantitated by MSs.

Animals↗
PubMed1997

Nutrition requirements in patients with toxic epidermal necrolysis.

Patients with toxic epidermal necrolysis, a severe, exfoliative skin disorder, have clinical features similar to those of partial-thickness burn patients. The literature suggests that they also have similar nutritional requirements. We report two patients diagnosed with toxic epidermal necrolysis on mechanical ventilation, in whom resting energy expenditure and respiratory quotient were measured by indirect calorimetry. The patients were treated using standard burn protocols. Nitrogen balance was calculated by measuring total urinary nitrogen in urine samples obtained over 24 hours. These measurements were done while the patients were on mechanical ventilation and receiving total parenteral nutrition. As in burn patients, early in their course the two patients had resting energy expenditure values twice that predicted. After 12 days of hospitalization, nitrogen balance was negative in patient 1 and positive in patient 2. Energy and protein requirements appear to have been related to the amount of body surface affected.

Calorimetry, Indirect↗
PubMed1997

EMC(electromagnetic compatibility): how to manage the challenge.

The significant changes in health care and telecommunications has produced an emergence of new and exciting technologies. Clinical engineers must continue to safeguard patient safety by adequately refurbishing their arsenal of technical knowledge of electromagnetic compatibility (EMC). This document examines the methodology and the tools for managing the technical changes in the telecommunications and biomedical equipment areas.

Data Collection↗
PubMed1996

A new organotypic culture method to study the actions of steroid hormones on the nervous system.

A new organotypic culture method for growing slices of nervous system tissue, based on the use of hyaluronic acid as a growth supporting milieu, is described. This method allows cultures derived from either fetuses or newborns to grow and develop with markedly reduced amounts of added serum. Organotypic cultures from fetal rat hypothalamus were exposed to 17 beta estradiol and compared to control cultures exposed to the ethanol vehicle. When exposed to estradiol, cultures showed an outgrowth of thick nerve fibers that was accompanied by an elevation in the number of microtubules present in the neuronal processes, an increment in the number of synapses, and an increased morphological differentiation of synaptic terminals. Freeze-fracture analysis of neuronal membranes from estradiol-treated cultures revealed a significant increase in the number of exoendocytotic images and a decrease in the number of intramembranous particles. Estradiol's effects parallel those found in in vivo studies, indicating that hyaluronic acid-based organotypic cultures represent an appropriate model to study hormonal influences on the developing nervous system.

Animals↗
PubMed1996

Action of steroid hormones on growth and differentiation of CNS and spinal cord organotypic cultures.

During the prenatal period, gonadal steroid environment induces dramatic sexually dimorphic changes in the nervous system. We have used in vitro methods to study the mechanism and timing of hormonal influences on neuronal sprouting and myelination during the prenatal period. Organotypic cultures of hypothalamus and lumbar spinal cord (SC) slices from rat fetuses were grown on plasma clot or in hyaluronic acid and exposed to estrogen (17 beta estradiol) and testosterone (T) during cultivation. Both steroid hormones were active: 17 beta estradiol enhanced sprouting of hypothalamic neuronal fibers and increased the amount of synapses. In SC cultures T induced regeneration of thick nerve processes and an early onset of myelination, mainly of peripheral myelin.

Animals↗
PubMed1995

Prosthetic fitting and ambulation in a paraplegic patient with an above-knee amputation.

The combination of paraplegia with an above-knee amputation is a complex injury that makes the rehabilitation process difficult. This article describes a case of T12 paraplegia and an above-knee amputation. After the rehabilitation course, the patient achieved full ambulatory independence with an ischial containment, contoured adducted trochanteric controlled alignment method (CATCAM) prosthesis and a knee ankle foot orthosis (KAFO). Difficulties in fitting a functional prosthesis to an insensate limb and the rehabilitation stages leading to functional ambulation are reviewed.

Activities of Daily Living↗
PubMed1994

A new method to evaluate cardiovascular response in anesthetized rats. Hypertension after variable intensity, brief electrical stimuli.

To establish and standardize a nociceptive response in anesthetized rats, the hypertensive responses to defined electrical and mechanical stimuli were studied. Rats (n = 7) were given etomidate, 3.8 mg/kg/hr intravenously (i.v.) 2 hr following carotid artery and jugular vein cannulation. At 15 min after beginning the infusion, four types of noxious stimuli were administered sequentially at 1-min intervals (14 stimuli total): Type 1: Square electrical waves, 125 cps, 1.6 msec, 2-sec train duration, varying current from 0.4 to 12 mA (11 stimuli); Type 2: A single 10-mA electrical stimulus, 5-sec train duration; Type 3: Tail clamping; and, Type 4: Skin incision. After each stimulus, maximum change in systolic blood pressure (delta SBP) was measured. delta SBP after the most intense stimuli was as follows: Type 1 (12 mA, 2 sec), 32.1 +/- 2.14 mmHg; Type 2 (10 mA 5 sec), 42.9 +/- 2.4 mmHg; Type 3 (tail-clamping), 34.3 +/- 3.3 mmHg; Type 4 (skin incision), 14.2 +/- 2.8 mmHg. For the multiple Type-2 stimuli, a relationship between current and delta SBP was present. The authors believe that characterized graded electrical stimulation will allow a more quantitative evaluation of the hypertensive response to noxious stimuli in etomidate anesthetized rats, as compared to observing a single response to a single stimulus. The characterization of the electrical stimulation by amplitude, frequency, and wave form makes research work on nociception under anesthesia easily reproducible.

Anesthesia↗
PubMed1994

Electromagnetic interference: causes and concerns in the health care environment.

In the past 15 years there has been a dramatic increase in the number of radio frequency emission sources that have entered medical treatment areas. Personal computers, digital pagers, hand-held radios, cellular phones, and wireless input devices have all become more prevalent in the contemporary clinical environment. Because of the productivity gains these devices promise, it is unlikely that the use of electronic instrumentation and wireless technologies will diminish--in fact greater uses are projected. Along with the benefits these devices provide, they also create a greater opportunity for increased electromagnetic interference among devices. It is important that engineering and professional staff are aware of some of the complex interactions these devices can create. Managing this emerging problem should be a concern for the medical community. Engineering staff should be able to communicate effectively with medical staff, patients, and visitors regarding potential interactions and how to recognize them and mitigate their consequences.

Academies and Institutes↗
PubMed1993

Technology evaluation in a US hospital: the role of clinical engineering.

Appropriate deployment of technological innovation contributes to improvement in the quality of healthcare delivered, containment of cost, and an increased access to the healthcare system. Hospitals have been allocating a significant portion of their resources to procuring and managing capital assets; they are continuously faced with demands for new medical equipment and are asked to manage existing inventory for which they are not well prepared. To objectively manage their investment, hospitals are developing medical technology management programmes that need pertinent information and methods for new equipment planning as well as for reduction in the ownership costs of existing equipment. Clinical engineers can identify new medical equipment, review their institution's technological position, develop equipment-selection criteria, supervise installations and monitor postprocurement performance to meet their hospital's programme's objectives. This programme, together with cost accounting analysis, will objectively guide the capital assets decisionmaking process. The result of systematic planning and execution, the programme will assure the lowest life-cycle costs at the best performance. The clinical engineer's skills and expertise are needed to facilitate the adoption of an objective methodology for implementing the programme, thus improving the match between the hospital's needs and budget projections, equipment performance and cost of ownership.

Biomedical Engineering↗
PubMed1993

Minimal tourniquet pressure to maintain arterial closure in upper limb surgery.

Complications of the pneumatic tourniquet used during limb surgery result from excessive direct pressure. Traditional recommendations suggests parameters for maximum pressure and time limits rather than the minimal effective pressure to achieve a bloodless field. A clinical study was undertaken to evaluate the pneumatic tourniquet setting required for adequate haemostasis in the upper limb. The correlations between several possible influencing parameters (age, sex, arm fat thickness, extremity length, systolic, diastolic, and mean blood pressures) and the minimal pneumatic tourniquet pressure at which the peripheral pulse reappeared were studied in 50 patients undergoing surgery, using a Doppler stethoscope. The average Doppler Opening Pressure was 168.5 +/- 42.7 mmHg and the only significant clinical variable was the mean blood pressure. From these results an equation was derived to predict the minimal effective tourniquet pressure. The mean calculated tourniquet pressure was 202.3 +/- 34.2 mmHg, well below the 250 to 300 mmHg previously recommended. The technique consisted of inflating the tourniquet to a pressure of 300 mmHg, then reducing it to the calculated value. A bloodless field was maintained in all patients.

Adolescent↗