Biomedical subjects

A T Morris

Publications and source records attributed to A T Morris.

21 records · Page 2Linked to original sources

PubMedDate not supplied

Relative underestimation of fluid removal during hemodialysis hypotension measured by whole body bioimpedance.

Whole body bioimpedance is considered helpful in monitoring the removal of excess body water by ultrafiltration in hemodialysis patients. In this study, the cumulative, estimated decrease in extracellular volume (V(est)) modeled from whole body bioimpedance data was compared with measured volume (Vmeas) removed by ultrafiltration (UFR = 1.01 +/- 0.31 L/hr) in 12 patients during 36 high efficiency hemodialysis treatments. In the mean, estimated (V(est) = 3.0 +/- 1.4 L) and measured volumes (Vmeas = 3.4 +/- 1.1 L) correlated linearly: V(est) = 1.05 x Vmeas - 0.60, r2 = 0.68. Patients developed hypotension in half the treatments. Except for a larger decrease in systolic blood pressures in hypotensive (34 +/- 24 mmHg) vs. stable (14 +/- 15 mmHg) treatments, patient and treatment characteristics were not different between groups. However, at the end of hemodialysis, the difference V(est) - Vmeas was -0.8 +/- 0.9 L in hypotensive, and only 0.1 +/- 0.4 L in stable patients (p < 0.05). The difference between V(est) and Vmeas can be explained by a predominant removal of excess body water from central body compartments such as the trunk and the central blood volume during hypotension. These compartments are not adequately measured by whole body bioimpedance techniques. However, this information could be helpful in identifying patients with delayed peripheral fluid removal that may occur when either target weight is too low or UFR rates are too high.

Adult↗

PubMedDate not supplied

Transverse keratotomy combined with spherical photorefractive keratectomy for compound myopic astigmatism.

This is a report of a study of 40 eyes in which transverse keratotomy was performed in conjunction with spherical photorefractive keratectomy. The preoperative range of myopia was -1.50 to -13.50 diopters (D). The mean attempted cylindrical correction was -1.73 D (range -0.75 to -4.00). After 6 months 47.8% achieved unaided visual acuity of 6/6, 60% achieved 6/9 or better and 75% achieved 6/12 or better. The mean postoperative spherical equivalent refraction was -0.01 D at 6 months. The mean astigmatism postoperatively was 0.32 D. A group of 179 eyes with six months follow-up after photorefractive keratectomy who had not had transverse keratotomy was compared. Their mean postoperative spherical equivalent refraction was -0.07 D and mean astigmatism was 0.21 D. Uncorrected visual acuity was 6/12 or better in 93.3%. Until there is an improvement in the mechanism of the ablatable mask this combined procedure offers patients with significant astigmatism the opportunity of achieving good visual results.

Astigmatism↗

PubMedDate not supplied

In vivo verification of an automatic noninvasive system for real time Kt evaluation.

It is generally accepted that morbidity and mortality of hemodialysis patients is related to dialysis quantitation. Currently available methods for the quantitation of dialysis require blood sampling or a continuous measurement of changes in urea concentration during treatment. These maneuvers are time consuming and expensive, and are generally performed, at most, once per month. The authors introduce an on-line, automated method for measurement of dialyzer electrolyte clearance comparable to urea clearance by using dialysate conductivity sensors placed pre and post dialyzer, and measuring conductivity at three different pre dialyzer levels. Conditions that reduce clearance, such as recirculation or fiber clotting, are automatically taken into account so that the method measures effective clearance rather than dialyzer clearance. In vitro and in vivo studies validate the method. Results are immediately available and can be used to address problems such as improper needle placement and access recirculation. In addition, repetitive electrolyte clearance data can serve to enhance quality assurance programs with respect to verifying the function of reused or new dialyzers. Appropriate algorithms can be used to calculate delivered Kt/V.

Blood Urea Nitrogen↗