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Biomedical subjects

D T Pearson

Publications and source records attributed to D T Pearson.

At least 19 recordsLinked to original sources
PubMed1992

Assessment of oxygen transfer in membrane oxygenators during clinical cardiopulmonary bypass.

Although functional replacement of the heart and lungs by a pump and oxygenator is a widespread surgical procedure, no widely accepted technique for describing gas exchange in oxygenators exists. In this study, 8 types of commercially available membrane oxygenator (2 flat sheet membrane, 4 gas in hollow fibre membrane and 2 blood in hollow fibre membrane) have been studied during clinical cardiopulmonary bypass. O2 transfer increased with blood flow rate but the O2 transfer at a given blood flow was lower than that obtained by the manufacturers in laboratory studies. Overall O2 transfer coefficients were calculated from the ratio of O2 transfer rate to an O2 difference expressed either as an O2 partial pressure or an O2 concentration. Specific O2 transfer coefficients (overall coefficient divided by membrane area) were similar for oxygenators with a flat sheet or gas in hollow fibre membrane configuration. The two types of oxygenator with blood in hollow fibre membranes had significantly lower (P less than 0.01) specific O2 transfer coefficients. This study shows that oxygenator gas transfer characteristics can be studied in the clinical environment and that O2 transfer coefficients can be related to oxygenator design features.

Aged↗
PubMed1990

Clinical comparison of two devices for detection of microemboli during cardiopulmonary bypass.

Detection of gaseous microemboli during cardiopulmonary bypass procedures is important for the clinical evaluation of equipment such as oxygenators and cardiotomy reservoirs. Comparison of published data can be difficult if different detectors are used. Two devices reported in the literature, the Technique Laboratories TM-8 and the Hatteland BD-100, are compared during clinical procedures. The relationship between the outputs of these devices was linear over two ranges, the difference in output amounted to a standard deviation of 11% in the lower range and 38% in the upper range.

Cardiopulmonary Bypass↗
PubMed1988

Independent control of blood gas PO2 and PCO2 in a bubble oxygenator.

An in-vitro circuit simulating cardiopulmonary bypass has been used to evaluate the gas transfer characteristics, gaseous microemboli production and blood damage of the Bentley-10 Plus bubble oxygenator. This oxygenator incorporates a unique integral gas controller which proportions the gas flow between the gas sparger and heat exchange area. The results of the study indicate that maintenance of a gas flow which ensures adequate CO2 removal can be prevented from inducing over-oxygenation by the manipulation of the gas controller which variably proportions the flow of gas from the oxygenation-efficient conventional gas sparger to the less efficient heat exchange area. Independent control of PaO2 with maintenance of CO2 transfer was demonstrated. Reduction in gaseous microemboli production and red blood cell damage with the use of the gas controller was demonstrated.

Blood Pressure↗
PubMed1988

Clinical trial of the Continucath intra-arterial oxygen monitor. A comparison with intermittent arterial blood gas analysis.

An intra-arterial continuous display oxygen electrode for radial artery cannulation is now available in the UK. Nine catheters were used in patients during and after hypothermic cardiac surgery. Results obtained were compared with those from conventional intermittent blood gas samples. Slow temperature response times negate its use during hypothermic surgery. A good correlation was found during the postoperative period. Indications for its use are discussed.

Aged↗
PubMed1987

Clinical comparison of one in vitro and three in-line blood gas PO2 sensors during cardiopulmonary bypass.

During 17 cardiopulmonary bypass (CPB) operations, arterial PO2 measurements were taken at 5 min intervals using four different types of PO2 sensor; three in-line (CardioMet-1000, Polytrode, and Gas-Stat) and one blood gas analyser (IL-1302). Comparisons between sensors were made relative to the CardioMet-1000. The three in-line sensors showed close agreement. The mean and standard deviation of the difference between the Gas-Stat and the CardioMet-1000 was 0.7 +/- 4.7 kPa, and between the Polytrode and the CardioMet-1000 was -1.4 +/- 4.0 kPa. Agreement between the IL-1302 blood gas analyser and CardioMet-1000 was not as good, the difference being -7.0 +/- 8.6 kPa.

Blood Chemical Analysis↗
PubMed1987

Anaesthesia for trans-sternal thymectomy in myasthenia gravis.

A retrospective review is presented of the thirty patients who underwent trans-sternal thymectomy for myasthenia gravis in our unit from 1980-85. The clinical status of these patients is contrasted to that of more severely debilitated patients described by other authors. The problems encountered by the anaesthetist in the perioperative care of patients with mild myasthenia gravis are discussed. Management of the perioperative anticholinesterase regime is described and a case presented for the use of suxamethonium for intubation. A less invasive postoperative regime is advocated in which tracheostomy and nasotracheal intubation are avoided, and anticholinesterase therapy is re-introduced orally as soon as possible after surgery.

Adolescent↗
PubMed1986

Monitoring EEG frequency and amplitude during cardiac surgery.

Changes in the electroencephalograms of patients undergoing cardiac surgery with cardiopulmonary bypass were studied. An analysis technique with a simple display of amplitude and frequency within the traditional bands was used. During the course of an operation, there can be dramatic changes in frequency contribution with little or no change in overall EEG amplitude. Evaluation of the results shows that this technique clearly draws attention to periods of EEG change, and examples are given.

Cardiac Surgical Procedures↗
PubMed1985

Postnatal lead exposure and early sensorimotor development.

The relationship between postnatal lead (Pb) exposure and early sensorimotor development was prospectively investigated in a group of infants born to parents residing in lead-hazardous areas of Cincinnati, Ohio. Few significant relationships were found between current or cumulative infant blood Pb levels and indices of sensorimotor development during the first year of life. When important developmental covariates such as birth weight and home environment were included in the analyses, no significant relationship between Pb exposure and development remained. To date, there appears to be no evidence in these data that postnatal low-level Pb exposure increases an infant's risk for delays in early sensorimotor development.

Child Development↗
PubMed1985

Attention, activity level, and lead exposure at 18 months.

A structured problem-solving task was used to evaluate the effects of lead (Pb) exposure on the activity patterns and attention of 18-month-old infants. After statistically controlling for the influence of the caretaker's attempts to support and teach the infant during the task, multivariate techniques were used to examine the residual variances to detect any effects of prenatal or postnatal Pb exposure. Contrary to expectations, no relationship was found between Pb exposure and measures of attention. Activity level was found to be negatively related to blood Pb level. The suggested suppression of behavior was inconsistent with reports of hyperactivity found in school children with elevated Pb level, but is consistent with observations of lethargy in infants with iron deficiency. To examine this alternative, free erythrocyte protoporphyrin (FEP) levels, which are elevated both in the presence of elevated Pb and in iron deficiency, were incorporated into the regression model. FEP was the best predictor of room movement, as indicated by a backward elimination analysis that removed all Pb measures from the model. However, none of the other measures of hematopoietic status were related to behavior. The suppression of activity level, if a reliable effect, is very small, and only weakly though significantly related to FEP level.

Attention↗
PubMed1985

Continuous monitoring of blood glucose concentration during open-heart surgery.

Continuous monitoring of blood glucose concentration was compared with frequent intermittent sampling in 12 non-diabetic adult patients undergoing open-heart surgery with cardiopulmonary by-pass using priming fluids free of glucose. Continuous monitoring revealed several changes which were not detected on intermittent sampling. Blood glucose concentration decreased by 2 mmol litre-1 +/- 0.5 (SEM) (P less than 0.01) immediately on the institution of CPB, and increased during the succeeding minutes. Rewarming from hypothermic by-pass was associated with a 3 (+/- 0.5)-mmol litre-1 increase in blood glucose concentration (P less than 0.01). Commencement of infusions of sympathomimetic agents resulted in a similar increase.

Blood Glucose↗
PubMed1985

The effects of four different crystalloid bypass pump-priming fluids upon the metabolic response to cardiac operation.

The crystalloid solutions used to prime cardiopulmonary bypass pumps frequently contain metabolically active substrates. However, there is a lack of controlled studies to investigate the metabolic response to cardiac operations using different pump primes. We have carried out a prospective, randomized study of 24 patients divided into four groups, each group receiving a different crystalloid prime. The primes contained glucose, lactate, glucose and lactate, or neither glucose nor lactate. Using identical anesthetic, surgical, and perfusion techniques, we estimated the metabolic response to cardiac operation in all patients by frequent blood sampling for measurement of hormone (insulin, glucagon, cortisol, and growth hormone) and metabolite concentrations (glucose, lactate, pyruvate, glycerol, alanine, and 3-hydroxybutyrate) from the day before operation to the seventh postoperative day. The results demonstrated that, after 4 hours postoperatively, the endocrine and metabolic response to cardiac operation was unaffected by the nature of the priming fluid. However, major endocrine and metabolic changes occurred before that time, which were related directly to the glucose and lactate contents of the prime. Very high concentrations of both glucose and lactate were observed at the end of bypass if they were induced in the prime. Given the known dangers of hyperglycemia in cerebral ischemia and the potential gluconeogenic effects of infused lactate, we suggest that glucose-free and lactate-free primes be employed in the extracorporeal circuit.

3-Hydroxybutyric Acid↗
PubMed1985

Contribution of social and developmental factors to lead exposure during the first year of life.

The social and developmental correlates of early lead exposure were explored in an interim analysis of data from an ongoing longitudinal investigation in Cincinnati. Regardless of the apparent net availability of lead in the infant's physical environment, parental behavior was still significantly associated with infant blood lead levels. However, this was only the case after infants in the study reached 6 months of age and beyond when prewalking progression and early walking made parental management all the more critical. Future lead screening and abatement programs should include supports for the caretaker-child relationship.

Child Development↗
PubMed1978

An ultrasonic analysis of the comparative efficiency of various cardiotomy reservoirs and micropore blood filters.

The ability of 12 commercially available cardiotomy reservoirs to remove bubbles from aspirated blood was investigated by means of a simulated cardiopulmonary bypass circuit and an ultrasonic microbubble detector. Performance varied considerably. The number of gaseous microemboli remaining after passage of blood through the reservoir was reduced by (a) holding the blood in the reservoir, (b) reducing the volume of air mixed with the aspirated blood, and (c) using a reservoir that did not induce turbulence and that contained integral micropore filtration material. Further micropore filtration of the blood after passage through the cardiotomy reservoir was beneficial, and significantly more bubbles were extracted when the microfilter was sited below the reservoir than when it was placed in the arterial line.

Cardiopulmonary Bypass↗
PubMed1977

Prevention of venous blood gas embolism with blood microfilters.

The efficacy of blood microfilters in removal of the gaseous emboli produced during the warming of blood for transfusion is demonstrated experimentally. It is suggested that when blood microfilters are used they should be placed distal to any blood warming device.

Blood Transfusion↗