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Biomedical subjects

L D Homer

Publications and source records attributed to L D Homer.

At least 73 records · Page 4Linked to original sources
PubMed1977

Computations for a best match strategy for kidney transplantation.

In some cases success or failure of a proposed innovation in transplantation may be better judged if we consider the average survival time of the graft rather than the actuarial survival at a point in time. It is suggested that HLA matching may be an example of such a case and that the possible clinical benefits of modest improvements in matching may have been underestimated. Calculations are made that show that transplanting to the best match available in a pool of 100 patients might increase the expected graft survival time by more than 1 year.

Graft Survival↗
PubMed1977

A proposal for the analysis of kidney graft survival.

A survival analysis using a model provides numerous advantages over other approaches. The effectiveness of concomitant variables in describing the data can be evaluated whether the variables are continuous or dichotomized. We can evaluate the effectiveness of such variables in describing either short- or long-term components of the risk. The expected life span of the graft may be computed with the model and complements the insight obtained from the more commonly displayed survival curves.

Age Factors↗
PubMed1977

Physiological parameters of indicator dilution curves.

A model incorporating the effects of recirculation time lag, cardiac output, clearance, volume of distribution, and the variance of the distribution of recirculation times is applied to the analysis of indicator dilution curves. Experiments on dogs with use of radioactively labeled diethylenetriaminepentaacetic acid were done to evaluate the model. This five-parameter model can be fitted to data obtained during the period from less than 1 min to 3 h after a single injection of indicator. Estimates of cardiac output and clearance are in satisfactory agreement with estimates obtained by alternative techniques. Estimates of the time lag and volume of distribution are of physiologically plausible magnitude. The variance of the distribution of recirculation times is a new parameter, of which the possible usefulness to physiologists is discussed.

Animals↗
PubMed1976

Incidence of acute exertional rhabdomyolysis. Serum myoglobin and enzyme levels as indicators of muscle injury.

This study was conducted to determine, on a prospective basis, the incidence of acute exertional rhabdomyolysis (AER) among recruits at the Marine Corps Recruit Depot, San Diego, Calif. Blood samples were taken from each of 337 volunteer recruits on each of their first six days of regularly scheduled training. Serum myoglobin, serum creatine phosphokinase, lactic dehydrogenase, and serum glutamic oxaloacetic transaminase values were used as indicators of muscle injury. Substantial elevations of serum enzyme activity were observed throughout the study population. Of the study population, 39.2% had serum myoglobin levels that ranged from 0.37 mug/ml to 21.9 mug/ml during the study interval. Six subjects had serum myoglobin levels consistent with those reported in clinical cases of AER. It is concluded that, in a recruit population, large numbers of men may have myoglobinemia but not be seen initially as clinical cases.

Acute Disease↗
PubMed1976

Onset of succinylcholine-induced hyperkalemia following denervation.

Denervation injuries in baboons were used to define the time course of the hyperkalemic response to succinylcholine. Half-peak increase in serum potassium (2.78 mEq/l) occurred 8.4 days following injury. Peak increase (5.5 mEq/l) appeared 14 days after injury. However, changes in potassium levels begin as early as four days after injury. Succinylcholine or other depolarizing muscle relaxants should not be used after the fourth day following an injury or denervation that involves two or more limbs.

Animals↗
PubMed1975

Diphenylhydantoin and lidocaine modification of A-V conduction in halothane-anesthetized dogs.

The effect of halothane on A-V conduction was evaluated in gods during atrial pacing using the technique of His-bundle electrocardiography. In addition, the effects of lidocaine and diphenylkydantoin (DPH) on A-V conuction were examined during halothane anesthesia. Effects of these drugs on three subintervals of A-V conduction were compared. These included the -H (stimulus atifact of His-bundle deflection-atrioventricular conduction), H-Q (His-budnle deflection onset of QRS complex-His-Purkinje conduction), and H-S intervals(His-bundle delfection to end of QRS COmplex-total intraventricular conduction). Linear regression best described the relationship between duration of interval (P-H, H-V,and H-S) and heart rate during incremental increases in the atrial paced rate. Data from these experiments were fitted to a multiple lenear regression model that predicted the effect of increasing concentrations of halothan, lidocaine, and DPH on slope and intercept coefficients. In creasing concentrations of halothan ( 30 and 45 mg/100 ml arterial). Both lidocaine and DPH further depressed conduction at all levels of halothan anesthesia. The P-H interval was particularly sensitive todrug effefts. This may represent potentiation of the normal slowing of conduction through the AVnode in response to incremental increases in heart rate (fatigue response.) We conclude thatboth lidocaine and DPH fail to reverse the depressant effect of halothane on A-V conduction. This may explain their ineffectiveness in treating certain types of arrhythmias during halothane anesthesia.

Anesthesia, Inhalation↗
PubMed1975

Estimation of cardiac output by analysis of respiratory gas exchange.

Cardiac output is estimated by least squares fitting of a model of pulmonary gas exchange to measurements of respiratory gas composition obtained with a mass spectrometer during a rebreathing maneuver. This new technique estimates cardiac output on spontaneously breathing subjects at rest and requires neither central venous nor arterial blood samples. Principal features of the technique are the use of multiple gases simultaneously in the analysis, the use of a mathematical model for breath-to-breath evaluation of gas exchange, and simultaneous estimation of gas exchange and alveolar gas tensions with the same instrumentation. The technique is compared with thermal dilution estimates in dogs before and during hemorrhagic shock. Two-thirds of these estimates were within 20% of one another. The standard deviation of replication was 15%. Shortcomings, possibilities for improvement, and possible applications are discussed.

Animals↗
PubMed1974

Proton nuclear magnetic resonance relaxation measurements in frog muscle.

Proton nuclear magnetic resonance (NMR) relaxation measurements are reported for frog muscle as a function of temperature and Larmor frequency. Each T(1rho), T(2), and T(1) measurement covered a time domain sufficient to identify the average relaxation time for most intracellular water. Using regression analysis the data were fit with a model where intracellular water molecules are exchanging between a large compartment in which mobility is similar to ordinary water and a small compartment in which motion is restricted. The regression results suggest that: the restricted compartment exhibits a distribution of motions skewed toward that of free water; the residence time of water molecules in the restricted compartment is approximately 1 ms; and, the activation entropy for some water molecules in the restricted compartment is negative.

Animals↗
PubMed1974

The relationship of circulating endogenous endotoxin to hemorrhagic shock in the baboon.

Experiments were carried out to test the hypothesis that during hemorrhagic shock endotoxin enters the circulation from ischemic bowel by way of the portal venous system and is then associated with irreversibility of the hemorrhagic shock state. After placement of sampling catheters in the portal vein, right atrium, and aorta, 14 awake, restrained baboons were subjected to 1 hour of hemorrhagic shock at a mean arterial pressure (MAP) of 60 torr followed by a second hour at 40 torr MAP. Six animals were resuscitated with Ringers lactate and their shed blood; 8 were maintained hypotensive until death. Serial blood samples were analyzed for the presence of endotoxin. Endotoxemia was found infrequently, with no greater incidence (p > 0.6) in portal venous samples than in systemic blood, so these data were pooled for further analysis. Furthermore, endotoxemia was no more frequent (p > 0.6) late in shock than it was in early shock or during the baseline period. Autopsy showed no evidence of ischemic damage to the splanchnic viscera. It was concluded that spontaneous endogenous entotoxemia is not a common feature of hemorrhagic shock in baboons and is not related to the duration or degree of severity of hemorrhagic shock in this subhuman primate species.

Animals↗