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M Ravin

Publications and source records attributed to M Ravin.

8 recordsLinked to original sources
PubMed1975

Changes in arterial pressure, viscosity and resistance during cardiopulmonary bypass.

Large changes in arterial pressure and systemic vascular resistance are frequently observed at the onset of and during cardiopulmonary bypass, particularly when hemodilution is employed. In order to assess the extent to which these changes are induced by changes in blood viscosity, we measured viscosity, pressure, and flow in a series of 17 patients. Hemodilution was used in Group A (12 patients) but not in Group B (5 patients). At the beginning of cardiopulmonary bypass, the arteriovenous pressure difference decreased an average of 53.8 per cent in the Group A patients, concomitant with a 41.7 per cent decrease in blood viscosity. The arteriovenous pressure difference in the Group B patients increased an average of 6.4 per cent, while the blood viscosity increased by 8 per cent. A nomogram was theoretically derived for the Group A patients, which allows rapid estimation of the extent of viscosity-induced hypotension for a given volume of priming fluid, initial patient hematocrit, and patient weight. After correction for viscosity changes due to hemodilution, the Group A patients were found to exhibit essentially normal values of systemic vascular resistance at the start of bypass, with a mean of 1,155 dynes-sec./cm.5. On the other hand, the Group B patients had elevated resistance values, with a mean of 1,611 dynes-sec./cm.5. During perfusion, the resistance of both groups tended to increase, sometimes by 100 per cent or more. In some cases, however, the resistance values changed in an erratic fashion. These effects were not due to changes in blood viscosity.

Adolescent↗
PubMedDate not supplied

Effects of hemodilution on hypotention during cardiopulmonary bypass.

Arterial pressure, systemic vascular resistance, and viscosity measurements were made on 20 patients, during cardiopulmonary bypass with hemodilution to an average hematocrit reduction of 48 plus or minus 12 percent. The arterial pressure and blood viscosity decreased an average of 56 plus or minus 16 percent and 40 plus or minus 12 percent, respectively. The total peripheral resistance following the start of bypass was significantly below normal (p smaller than 0.005), but not when corrected for the change in viscosity. There was a strong correlation between the extent of pressure reduction and the viscosity decrease with hemodilution (p smaller than 0.01), although not all the changes in pressure could be accounted for in terms of viscosity. There was no apparent correlation between the extent of hypotension as measured by the area of the pressure-time curve below 50 mm. Hg and the presence or absence of postoperative cerebral or cardiac complications, in contrast to other recent reports.

Adolescent↗
PubMedDate not supplied

Myotonia dystrophica--an anesthetic hazard: two case reports.

The cluster of abnormalities characteristic of myotonia dystrophica makes anesthesia a hazardous procedure. A thorough history and physical examination are essential, anesthetic agents must be selected with care, and ventilation requires meticulous attention.

Adult↗