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Biomedical subjects

R D Weisel

Publications and source records attributed to R D Weisel.

226 records · Page 13Linked to original sources
PubMed1973

Indicator dilution measurements of lung volumes and alveolar air exchange during breathing.

A new triple tracer indicator dilution technique has been used to measure alveolar ventilation as well as air and tissue volumes in the lungs of experimental animals and man. The tracers indocyanine green, [(121)I]antipyrine and xenon-133 were rapidly injected into the right atrium, while sampling was carried out from a peripheral artery. Blood flow and tissue volumes were obtained by classical analysis of the indocyanine green and antipyrine concentration-time curves. A double exit-port, constant air flow model was used to analyze the xenon curves, because ventilatory loss led to incomplete recovery of the gas tracer in effluent blood. Uniform ventilation and perfusion were assumed. This analysis permitted calculation of alveolar ventilation (VA(Xe)) and functional residual capacity (FRC(Xe)) during normal breathing. In control studies, VA(Xe) was similar to VA(co2), obtained with the steady-state CO(2) method (r = 0.87), while in critically ill patients the xenon measurement was significantly lower, averaging 54% of VA(co2). In theory, underestimates in VA(Xe) and decrease in the ratio VA(Xe)/VA(co2) relate to nonuniformity in regional ventilation and perfusion. The effect is greatest for the slightly soluble gas, xenon. The significant inverse correlation between VA(Xe)/VA(co2) and the physiologic shunt is consistent with this postulate.FRC(Xe) was similar to the predicted FRC in animals but was 76% of the helium measured FRC in patients. FRC(Xe) was significantly lower than the xenon measured air volumes during breath-holding when nonuniformity of ventilation was not operative. Lung tissue volumes in animals were 83% of gravimetric lung weights, while in patients the volumes were much lower than predicted. Nonhomogeneous lung function, including failure to perfuse the entire capillary bed, with resultant incomplete penetration of tracers into all segments of lung air and tissue, may explain these findings. The resultant errors can be significant in sick patients, and may themselves be used to study nonhomogeneities in the distribution of ventilation and volume.

Adult↗
PubMedDate not supplied

The effect of lactate infusion on myocardial metabolism and ventricular function following ischemia and cardioplegia.

Impaired myocardial fatty acid and glucose metabolism following ischemia and cardioplegia may limit the recovery of myocardial oxidative metabolism and ventricular function. Lactate, a simple three carbon compound, can be readily metabolized to pyruvate and is possibly the preferred substrate for aerobic metabolism. Therefore, increasing arterial lactate concentrations may improve myocardial metabolic recovery after ischemia and cardioplegia. Myocardial lactate metabolism and ventricular function were assessed in a canine model of 45 mins of global normothermic ischemia followed by 60 mins of cold potassium cardioplegic arrest. Thirteen dogs received a perioperative infusion of sodium lactate to elevate arterial concentrations (from 6 to 12 mmol/L) and 12 dogs received an equivalent amount of saline. The high arterial lactate concentrations were associated with an increased myocardial lactate consumption and oxidation (as assessed by 14C-labelled lactate) during reperfusion. Myocardial ATP concentrations fell during reperfusion despite improved myocardial oxidation. The recovery of ventricular function (as assessed by a compliant intraventricular balloon) was incomplete and only marginally better with the high arterial lactate concentrations. An infusion of lactate improved myocardial oxidative metabolism following ischemia and cardioplegia. However, the recovery of ventricular function was incomplete perhaps because of inadequate preservation of myocardial ATP.

Adenosine Triphosphate↗
PubMedDate not supplied

Future directions of vitamin E and its analogues in minimizing myocardial ischemia-reperfusion injury.

Oxidant injury contributes to myocardial stunning, and cardiac ischemic and reperfusion injury. Vitamin E is the major--and perhaps the only--lipid soluble, chain-breaking antioxidant in the heart. Vitamin E and its analogues potentially offer significant advantages for the prevention of ischemic and reperfusion injury. Recent investigations have suggested that modified vitamin E analogues may be more efficacious than vitamin E and may permit myocardial salvage from acute myocardial ischemic injury.

Animals↗
PubMedDate not supplied

Cardiac storage with University of Wisconsin solution, calcium, and magnesium.

BACKGROUND: Previous investigations from this institution and others support the role of University of Wisconsin solution for prolonged hypothermic cardiac storage. Modification of the divalent cation concentrations has been beneficial for cardioplegic investigations and may enhance cardiac recovery after extended preservation. METHODS: To investigate this hypothesis, isolated rodent hearts were obtained from Sprague-Dawley rats and mounted on a Langendorff apparatus. Rat hearts were flushed (15 ml/kg) and stored (30 ml) for 8 hours at 0 degree C in unmodified University of Wisconsin solution (n = 16/group) or University of Wisconsin solution with calcium concentrations of 0.025 to 10 mmol/L or magnesium concentrations of 10 to 20 mmol/L (six to eight hearts/group). Finally, combinations of calcium and magnesium were examined. Rat hearts were studied before storage and after 45 minutes of reperfusion with an intraventricular balloon. RESULTS: Developed pressure (mean +/- standard deviation) was increased with calcium 0.1 mmol/L (University of Wisconsin solution: 69.2% +/- 7.0%; Ca++ 0.1 mmol/L: 78.9% +/- 6.1%, p < 0.05), whereas only the addition of the highest calcium concentration (10 mmol/L) was significantly harmful (developed pressure: 58.3% +/- 8.4%, p < 0.05; creatine kinase release: 408 +/- 200 versus 170 +/- 104 IU/gm, p < 0.05; lactate dehydrogenase release: 103 +/- 43 versus 37 +/- 26 IU/gm, p < 0.05). Coronary flow recovered to control values with magnesium 15 mmol/L, which was significantly greater than that achieved with unmodified University of Wisconsin solution (97.1% +/- 14.6% versus 72.1% +/- 8.4%, p < 0.05). Of the calcium-magnesium combinations tested, developed pressure was increased compared with unmodified University of Wisconsin solution with calcium 0.1 and magnesium 20 mmol/L (76.8% +/- 6.4%, p < 0.05). Diastolic function was reduced in all groups (p < 0.0001) and not significantly different between groups. CONCLUSIONS: The experiments indicated that recovery after storage with University of Wisconsin solution is enhanced with the addition of calcium and magnesium. The addition of high concentrations of calcium (> or = 2.5 mmol/L) appears harmful.

Adenosine↗