Extracorporeal membrane oxygenation.
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Extracorporeal Membrane Oxygenation↗
Biomedical subjects
G Lister
Publications and source records attributed to G Lister.
Persistent pulmonary hypertension of the newborn.
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Animals↗
Functional assessment of pulmonary capillary surface area in the 2-mo-old lamb.
We recently reported that measurements of the maximal velocity of pulmonary endothelial angiotensin-converting enzyme (Vmax) in vivo provide information regarding microvascular surface area in the developing lamb. To obviate any subtle influences of development on Vmax aside from simple increases in surface area, we correlated Vmax with postmortem stereological assessments of alveolar surface area in the relatively mature lung of the 2-mo-old lamb (n = 14). We attempted to increase the range of surface area beyond its normal variability by injecting nine of the lambs with bleomycin, an antineoplastic agent with significant pulmonary toxicity in other species. Vmax, measured shortly after birth and then weekly, increased monotonically in all lambs. Despite their wide dispersion, Vmax and the stereological determinations correlated strongly at 2 mo of age, confirming that Vmax is a robust indicator of the surface area of the air-blood barrier. There was no significant difference in either measurement between the control lambs and those treated with bleomycin, suggesting that the newborn lamb is resistant to the effect of this agent.
Age Factors↗
Results of primary tendon repair with closure of the tendon sheath.
This study reports the results of primary flexor tendon repair combined with closure of the tendon sheath in 31 Zone 2 injuries. In 3 digits, the profundus tendon alone was divided. In a further 7 digits, one tendon was completely divided and the other was incompletely divided. The remaining 21 digits involved complete division of both tendons. Assessment of the results according to the total active motion (TAM) system found 86% of the repairs in the excellent, good and fair categories. Two ruptures occurred (6%). A second assessment employed the criteria of Strickland, excluding the motion of the metacarpophalangeal joint. The results obtained following suture of both tendons were: excellent (39%); good (36%); fair (14%); poor (4%); and rupture (7%). These results lend support to the belief that closure of the tendon sheath decreases external adhesion formation and improves motion without increasing the risks of rupture.
Adult↗
Hypertension and asthma: psychological aspects.
Essential hypertensive and asthmatic patients, plus normal non-clinical controls, were compared on a number of psychological measures in order to identify the relationship between psychological distress, coping strategies and compliance behaviour. The hypothesised relationship between chronic clinical ailments and psychological distress was confirmed. The association between the presence of physical symptoms in the symptomatic condition, asthma, and greater psychological distress was also confirmed. The coping strategies adopted by the patients did not discriminate between the two clinical groups. Compliance with medication was negatively correlated with measures of psychological distress. Compliance with an appropriate healthy lifestyle was not correlated with medication compliance, although it too was negatively correlated with other measures of psychological distress.
Adaptation, Psychological↗
Effect of hemoglobin concentration on critical cardiac output and oxygen transport.
We previously found limited tolerance to acute reduction in cardiac output in lambs at the nadir of their physiological anemia [Am. J. Physiol. 253 (Heart Cir. Physiol. 12): H100-H106, 1987]. To determine the effect of hemoglobin concentration [Hb] on critical cardiac output, critical systemic O2 transport, and peripheral O2 extraction, we performed 31 experiments in 12 one-mo-old lambs at four [Hb] (means +/- SD in g/dl): 7.4 +/- 0.6, 10.5 +/- 0.5, 14.5 +/- 0.5, and 16.5 +/- 0.6. Desired [Hb] was obtained by exchange transfusion with packed red cells or plasma. Cardiac output was reduced by inflation of a balloon-tipped catheter in the right atrium, and critical levels were defined at the point where O2 consumption decreased and/or arterial blood lactate concentration increased in response. With lower [Hb], cardiac output was unchanged, systemic O2 transport was reduced, and fractional O2 extraction was increased, keeping O2 consumption constant at base line. As [Hb] was reduced, critical cardiac output was significantly higher, whereas critical systemic O2 transport was independent of [Hb], as were fractional O2 extraction and mixed venous PO2 at the critical point. Thus peripheral O2 extraction was not affected by changes in [Hb] during progressive decreases in cardiac output. We conclude that 4-wk-old lambs have decreased tolerance to reductions in cardiac output and systemic O2 transport because their relative anemia provides them with a base-line cardiac output and systemic O2 transport close to the critical level.
Animals↗
Response to low cardiac output: developmental differences in metabolism during oxygen deficit and recovery in lambs.
When cardiac output is critically lowered, whole body O2 consumption decreases and an O2 deficit accumulates. With restoration of cardiac output, an excess O2 consumption is expected in order to "repay" some or all of the O2 deficit. We tested the hypothesis that young lambs, with higher resting O2 consumption, cardiac output and growth rates than older lambs, would repay less of their O2 deficit because they have a higher proportion of nonessential metabolism. We reduced cardiac output acutely by inflating a Foley catheter in the right atrium of spontaneously breathing, sedated lambs at ages 2 (n = 5) and 8 (n = 5) wk. Each lamb was studied with low cardiac output periods of 30 and 60 min on different days. Aortic and pulmonary artery blood pressures, gases, and O2 saturations, venous Hb, and arterial lactate concentrations were measured every 10 min during baseline, low output, and 60 min of recovery. Oxygen consumption was monitored continuously. Oxygen deficit and excess O2 of recovery were calculated from the time integral of the difference between O2 consumption at baseline and during the respective study period. The average percent decreases in cardiac output (66.4 and 64.6%) and O2 consumption (38.1 and 35.1%) were similar in the 2- and 8-wk groups, respectively. There was no consistent relation between O2 deficit and O2 repayment in either age group. However, on average the 2-wk group repaid a significantly lower percentage (3 +/- 16%, mean +/- SEM) than 8-wk-olds (76 +/- 29%).(ABSTRACT TRUNCATED AT 250 WORDS)
Aging↗
Interpretation of metabolic function of the lung. Influence of perfusion, kinetics, and injury.
Quantitative assessment of pulmonary metabolic function has been shown to be a novel and important approach to obtaining specific and subtle biochemical information regarding endothelial cell function in the normal and diseased lung. A primary consideration in this measurement of whole organ metabolism, whether it be enzyme, transport, or binding functions, it is to be able to separate convective from kinetic aspects of endothelial cell physiology. Significant progress has been made in both our understanding of the influence of convective factors, as well as of possible solutions relying on mixed order kinetics. Nonetheless, the pervasive influence of surface area on these metabolic measurements and the distinct likelihood that this variable is simultaneously altered with endothelial cell function in acute lung injury makes definitive statements premature at this time. Several approaches to resolve this important issue have been attempted and include simultaneous measurement of nonmetabolic endothelial cell function including DLCO or permeability to urea; simultaneous measure of microvascular space for water or antipyrine; comparison with complex uptake and binding of a lipophilic basic amine such as propranolol; and multiple metabolic markers that may be selectively affected by injury. Other advances that should prove useful include an on-line computer registration of metabolic information, as well as gamma-scintigraphy for the purpose of obtaining regional information.
Animals↗
Perioperative care of the infant with congenital heart disease.
The current approach to the perioperative management of the infant and child with congenital heart disease has been discussed. The major focus has been on potential problems of oxygen transport as they relate to vital organ system function. Management strategies for specific defects or perioperative problems have also been considered as well as the newer on-line monitoring techniques, while stressing the importance of careful clinical evaluation. The ultimate surgical outcome is dependent not only on the adequacy of repair or palliation but on the treatment of potential life-threatening situations that may take place during the critical postoperative period.
Heart Defects, Congenital↗
Unbounded health.
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Health Services Needs and Demand↗
Postnatal growth of the sheep lung: a morphometric study.
Stereologic methods were used to study lung development in sheep from 2 to 171 days of age. Most growth occurs within the first 2 months when there is a threefold increase in lung volume, but allometric relationships show that this increase does not keep pace with body weight. Alveolar and capillary surface areas increase as lung volume to a power only slightly larger than 1, suggesting a modest increase in complexity; this is confirmed by only a two- to threefold increase in total alveolar number. Allometric power functions are essentially unchanged even during the first 30 days so that throughout development, the surface for gas exchange is added at a fairly constant rate. A slight increase in septal volume during the first 30 days is probably due to relative increase in capillary luminal volume through a progressive distension of capillaries. The results suggest that the active newborn lamb requires an alveolar lung, but in the postnatal period functional needs increase only moderately. In contrast, other mammals, such as the rat, are helpless as newborns and have a primitive saccular lung that must undergo considerable morphogenesis to meet the demands of the active adult.
Animals↗
Post-operative management of flexor tendon grafting.
This paper reviews the post-operative management of 145 tendon grafts in 127 patients. 80 grafts were managed post-operatively by a period (three to four weeks) of immobilisation followed by gentle active mobilisation. 65 grafts were managed by immediate controlled mobilisation (Kleinert technique) for three to four weeks. The final motion obtained was independent of the post-operative management. However, the rates of graft rupture (nine against four) and of tenolysis (sixteen against eight) were higher in the immobilised group.
Female↗
Emergency free flaps to the upper extremity.
Thirty-one emergency free flaps were applied to the upper extremities of patients who ranged in age from 16 to 57 years. The size of the skin defects ranged from 13 to 540 square centimeters, with an average of 145 square centimeters. A variety of flaps were used, including 14 lateral arm, seven groin, five latissimus, three first web space of the foot, one scapular and one medial arm. In patients with small defects, the operative time ranged from 3 to 9 hours, with an average of 4 hours and 54 minutes. The hospital stay was never longer than 4 days. In patients with medium size defects, the operating time ranged from 3 to 18 hours, with an average of 7 hours and 45 minutes. The hospital stay averaged 7.4 days. In large defects in which extensive reconstruction was undertaken before flap application, the operative time ranged from 3 to 20 hours, with an average of 11 hours and 54 minutes. The average hospital stay was 11.8 days. Twenty-nine of the 31 flaps survived in their entirety (93.5%). In one of the successful flaps (3.2%), exploration was required after the patient left the operating room. Severe infection occurred in only one case, that being one of the two flap failures. Twenty-seven of the 31 patients returned to work, 18 of them to their original employment.
Adolescent↗
Microsurgical transfer of the second toe for congenital deficiency of the thumb.
Twelve second-toe transfers have been performed to substitute for thumbs congenitally deficient through constriction ring syndrome, symbrachydactyly, and true transverse arrest. The children were on average 3 years of age, and the youngest was undertaken at 10 months. Anatomic variations were the rule in the six cases of transverse absence and the three cases of symbrachydactyly, requiring nerves, tendons, and vessels in the toe be connected to whatever appropriate structure could be located. All transfers survived, and only one required exploration. Sensation appeared good in the 11 seen in later review, but interphalangeal motion was achieved in only 3. However, good use was made of the digit by all except one patient, an early patient in whom there was not an adequate skeleton on which to base the transfer. This small series suggests that in appropriate cases toe transfer can be undertaken early for congenital deficiency with little fear of encountering microsurgical problems unique to the infant.
Child↗
Hypoxanthine and lactate concentrations in lambs during hypoxic and stagnant hypoxia.
To determine the suitability of plasma hypoxanthine as a marker of tissue hypoxia, we studied the relationship of arterial plasma hypoxanthine and blood lactate concentrations to the cumulative O2 deficit during hypoxemia and low cardiac output (hypoxic and stagnant hypoxia, respectively). Eight intact, chronically catheterized lambs were studied using ketamine sedation. Comparable reductions in O2 transport and consumption were produced with each form of hypoxia. Lactate was linearly related to O2 deficit during both forms of hypoxia, although the slope of the regression was greater for low cardiac output (0.049) than hypoxemia (0.032). Hypoxanthine was linearly related to cumulative O2 deficit only during low cardiac output. During hypoxemia, hypoxanthine concentration initially increased but plateaued with further increases in O2 deficit. The discrepancy in response of hypoxanthine was most likely caused by differences in the rate of elimination between stagnant and hypoxic hypoxia. We concluded that plasma hypoxanthine concentration was not a reliable marker for tissue hypoxia because it differed with the cause of O2 deprivation and did not necessarily reflect the severity of O2 deprivation.
Algorithms↗
Measurements of blood flow.
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Cardiac Output↗
Effects of changes in pulmonary perfusion and surface area on endothelial ACE activity.
Measurement of transport or enzymatic processes associated with pulmonary endothelial cells could provide unique information regarding the physiologic function of the microcirculation as well as data describing the biochemical integrity of these cells in acute lung injury. Since an important goal of such measurements is to quantify the kinetics of reactions of substrates (indicators) with the endothelium, it would be highly advantageous to account for (convective) phenomena related to blood flow and its distribution which also influence whole organ metabolism. In the present report, we describe studies that have utilized a nonlinear model of organ metabolism to estimate Vmax, the apparent maximal velocity and Km, concentration at one-half Vmax of angiotensin-converting enzyme (ACE) activity. Our hypotheses have been that (a) there is sufficient data to calculate apparent kinetic constants from indicator-dilution outflow curves after injection into the pulmonary circulation of a radiolabelled synthetic substrate for ACE, and (b) Vmax for ACE is a property related to the amount of enzyme located on the endothelial cells, and as such, should be directly proportional to perfused surface area of an organ. In isolated perfused rabbit lungs, when flow was increased over a two-fold range, but surface area was unchanged, neither Vmax nor Km for ACE activity was significantly altered. When indicator-dilution measurements of pulmonary ACE activity were made in lambs from 1-171 days of age there was a progressive increase in Vmax with no significant change in Km as a function of age. The increase in Vmax was closely correlated with an independent measure of surface area, carbon monoxide diffusing capacity, and a morphometric measure of capillary endothelial cell surface area (stereology at electron microscopic level) made at post-mortem. These experimental observations in whole organs support our hypotheses and predictions regarding the metabolism or removal of substrates from the circulation by means of a saturable process.
Animals↗
Adverse occurrences in the pediatric intensive care unit.
This article is intended to provide a review of the literature describing adverse occurrences affecting children in the intensive care unit. In addition, information related to the care of critically ill children is inferred from studies of adult or neonatal patients. Finally, areas in need of future investigation are suggested.
Accidents↗