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J C Firrell

Publications and source records attributed to J C Firrell.

28 records · Page 2Linked to original sources
PubMed1992

X-ray evaluation of radial shortening for Kienböck's disease.

The effect of inclination of the distal radius to subsequent lunate collapse is controversial. Therefore we evaluated the postoperative x-ray course of 10 patients with stage II, III, or IV Kienböck's disease who were treated only with radial shortening and followed up for an average of 25 months. The three patients who became worse as determined by x-ray evaluation had lunate fossa inclinations of less than 12 degrees after surgery. The four patients who improved had lunate fossa inclinations greater than 12 degrees. Appropriate radial shortening with adjunct wedge osteotomy to increase lunate fossa inclination may prevent further lunate collapse.

Adult↗
PubMed1989

Leukocyte margination and deformation in mesenteric venules of rat.

White blood cell (WBC) margination and rolling were studied in venules (20-60 microns in diameter) in rat mesentery to examine the relationship between WBC rolling velocity (Vwbc), flux (Fwbc, cells/min), and deformation; and red blood cell (RBC) velocity (Vrbc), wall shear rate (gamma), and microvessel hematocrit (Hmicro). For a range of 1.0 less than or equal to Vrbc less than or equal to 5.0 mm/s, Vwbc remained constant (congruent to 50 microns/s). The volume flux of WBCs rolling along the venular wall (normalized to systemic WBC concentration) decreased nonlinearly from 30 to 5% of total luminal flux as gamma ranged from 50 to 800 s-1 and was more strongly correlated with gamma compared with Fwbc vs. gamma. As indicated by the rolling volumetric flux, margination was weakly affected by Hmicro, except for Hmicro greater than 50% where margination increased. Deformation of WBCs was quantitated during their rolling contact with the endothelium (EC) in terms of their length and height. As gamma increased from 50 to 800 s-1, WBCs elongated to 140% of their estimated undeformed diameter, and the contact area between WBC and EC increased 3.6-fold. These data suggest that with increased gamma rolling of WBCs along the EC decreases, since only the most deformable WBCs of the circulating population persist in maintaining contact with the endothelium. It is concluded that Vwbc is invariant with elevations in gamma, since the greater deformations of rolling WBCs at high shear result in greater adhesive forces attendant to increased WBC-EC contact area, which attenuate increases in Vwbc.

Animals↗
PubMed1988

Leukocyte endothelium adhesion and microvascular hemodynamics.

In the present study we have attempted to provide quantitative details of hemodynamic determinants of leukocyte to endothelium adhesion in the microvasculature. To this end, several hypotheses have been advanced to suggest that the preferential adhesion of leukocytes in the larger venules (30-50 microns diameter) rests upon the inherent ability of the microvasculature to compensate for small perturbations in resistance and that WBC deformability may play a significant role in this process. Flow redistribution and attendant arteriolar vasomotor adjustments may forestall LEA in the larger collecting venules of the network, where venous obstruction may be countered by bringing the full weight of the arteriovenous pressure gradient to oppose WBC adhesion. Direct measurements of the force of adhesion suggest that with diminishing vessel diameter, as for example in the immediate post-capillary venules, WBC dispersal forces will be greatest due to dramatic increases in the proportionality between force and wall shear stress. This event would tend to preclude adhesion in the smallest venular microvessels. It has also been shown that there is a strong potential for WBC deformability to affect the adhesion process by modification of the shear stresses acting on the WBC surface, as evidenced by an inverse relationship between force and wall shear stress and direct observations of WBC shape changes with increasing shear.

Animals↗
PubMed1986

Microvascular hemodynamics during systemic hemodilution and hemoconcentration.

Measurements of intravascular pressure, red blood cell (RBC) velocity, and microvessel hematocrit (Hctmicro) were made in arterioles and venules of the cat mesenteric microvasculature during systemic hemodilution (cell-free plasma) and hemoconcentration (packed cells). For a range of systemic hematocrits (Hctsys) from 5 to 67%, changes in volumetric flux of red cells (QRBC) were derived from the product of microvessel bulk flow and Hctmicro. During hemodilution, a heterogeneous response of changes in QRBC was found with larger distributing arterioles (43-54 microns) exhibiting a monotonic fall, whereas increases in QRBC above control were found in smaller arterioles that were indicative of a potential enhancement of oxygen delivery. Although the dilution response of all arterioles and venules averaged for all calibers of vessels demonstrated a decline in QRBC, alterations of Hctmicro suggested a lessening of the disparity between Hctsys and Hctmicro, which was indicative of a more efficient utilization of the remaining circulating RBC volume. In response to hemoconcentration, a decrease in QRBC also occurred, which, in concert with the dilution data, suggested that QRBC was maximized for a range of 28 less than Hctsys less than 46%. From measurements of the arteriovenous pressure drop across mesenteric modules, regional resistance was found to exhibit a relative plateau as Hctsys was increased above its control value. This behavior was attributed to a decrease in vascular hindrance of the principal resistance vessels and an invariance of blood viscosity at the capillary level due to RBC redistribution and the attendant viscous behavior of blood.

Animals↗
PubMed1985

The value of the photoplethysmograph in monitoring skin closure in microsurgery.

Excessive tension during skin closure may impair flow in a free tissue transfer. Objective methods to observe skin perfusion have been developed. One of these, photoplethysmography, is commonly used for postoperative observation of flow in free flaps. This article demonstrates that valuable information can be obtained with photoplethysmography during wound closure also.

Adult↗
PubMed1984

Segmental and total microvascular resistances during hemorrhagic hypotension in rabbit omentum.

Single input-output microvascular modules in the rabbit omentum were studied to quantitate total modular resistance (RT) and the changes in resistance of successive serial segments (Rseg) during hemorrhagic hypotension (55 mmHg for 1 h). RT was calculated from the pressure drop between input and output vessels and the total flow through the module. Changes in Rseg were estimated from alterations in single microvessel hindrance (1/diam4) for selected microvessels within a module together with a correction for flow redistribution within each segment derived from changes in the proportion of total flow. Mean RT increased to 2.1 times control within the first 10 min of systemic hypotension and gradually declined over 1 h. Response of Rseg varied in different generations of microvessels (arterioles and venules subdivided by size). Rseg for arterioles and venules less than 30 microns, but not that for arterioles and venules greater than 30 microns, showed comparable or greater changes than RT. Calculated differences between RT and the summed Rseg of measured segments suggest that the unmeasured Rseg in capillaries and blood rheological parameters may have significantly influenced changes in RT during hemorrhagic hypotension.

Animals↗
PubMedDate not supplied

The effect of deferoxamine on ischemic changes in rat skeletal muscle: a preliminary study.

The purpose of this study was to evaluate the effectiveness of deferoxamine in preventing detrimental microvascular changes in ischemically damaged skeletal muscle during the initial reperfusion stage. Sprague-Dawley rats were given saline or deferoxamine (25 or 50 mg/kg) intravenously just prior to release of an air tourniquet placed around one hindlimb for 4 h. The limb was allowed to reperfuse for 2 h. Vascular leakage of plasma protein was assayed by determining the amount of 131I-labeled serum albumin that was given intravenously 30 min prior to release of the tourniquet. The wet and dry weights of the gastrocnemius and tibialis anterior muscles and the 131I activity were evaluated in both ischemic and nonischemic limbs. Although vascular permeability and edema increased markedly in both muscles in the ischemic limbs, there were no significant differences between the saline or either treatment groups. The lack of effect of deferoxamine in this initial report suggests that skeletal muscle may differ from other tissues in the early reperfusion stage.

Animals↗