Biomedical subjects

Harriet Hopf

Publications and source records attributed to Harriet Hopf.

4 recordsLinked to original sources

PubMed2006

Fresh blood and aged stored blood are equally efficacious in immediately reversing anemia-induced brain oxygenation deficits in humans.

BACKGROUND: Erythrocytes are transfused to treat or prevent imminent inadequate tissue oxygenation. 2,3-diphosphoglycerate concentration decreases and oxygen affinity of hemoglobin increases (P50 decreases) with blood storage, leading some to propose that erythrocytes stored for 14 or more days do not release sufficient oxygen to make their transfusion efficacious. The authors tested the hypothesis that erythrocytes stored for 3 weeks are as effective in supplying oxygen to human tissues as are erythrocytes stored for less than 5 h. METHODS: Nine healthy volunteers donated 2 units of blood more than 3 weeks before they were tested with a standard, computerized neuropsychological test (digit-symbol substitution test [DSST]) on 2 days, 1 week apart, before and after acute isovolemic reduction of their hemoglobin concentration to 7.4 and 5.5 g/dl. Volunteers randomly received autologous erythrocytes stored for either less than 5 h ("fresh") or 3 weeks ("stored") to return their hemoglobin concentration to 7.5 g/dl (double blinded). Erythrocytes of the alternate storage duration were transfused on the second experimental day. The DSST was repeated after transfusion. RESULTS: Acute anemia slowed DSST performance equivalently in both groups. Transfusion of stored erythrocytes with decreased P50 reversed the altered DSST (P < 0.001) to a time that did not differ from that at 7.4 g/dl hemoglobin during production of acute anemia (P = 0.88). The erythrocyte transfusion-induced DSST improvement did not differ between groups (P = 0.96). CONCLUSION: Erythrocytes stored for 3 weeks are as efficacious as are erythrocytes stored for 3.5 h in reversing the neurocognitive deficit of acute anemia. Requiring fresh rather than stored erythrocytes for augmentation of oxygen delivery does not seem warranted.

2,3-Diphosphoglycerate↗

PubMed2004

Clinical applications of EPR: overview and perspectives.

The development and use of in vivo techniques for strictly experimental applications in animals has been very successful, and these results now have made possible some very attractive potential clinical applications. The area with the most obvious immediate, effective and widespread clinical use is oximetry, where EPR almost uniquely can make repeated and accurate measurements of pO2 in tissues. Such measurements can provide clinicians with information that can impact directly on diagnosis and therapy, especially for oncology, peripheral vascular disease and wound healing. The other area of immediate and timely importance is the unique ability of in vivo EPR to measure clinically significant exposures to ionizing radiation 'after-the-fact', such as may occur due to accidents, terrorism or nuclear war. There are a number of other capabilities of in vivo EPR that also potentially could become extensively used in human subjects. In pharmacology the unique capabilities of in vivo EPR to detect and characterize free radicals could be applied to measure free radical intermediates from drugs and oxidative process. A closely related area of potential widespread applications is the use of EPR to measure nitric oxide. These often unique capabilities, combined with the sensitivity of EPR spectra to the immediate environment (e.g. pH, molecular motion, charge) have already resulted in some very productive applications in animals and these are likely to expand substantially in the near future. They should provide a continually developing base for extending clinical uses of in vivo EPR. The challenges for achieving full implementation include adapting the spectrometer for safe and comfortable measurements in human subjects, achieving sufficient sensitivity for measurements at the sites of the pathophysiological processes that are being measured, and establishing a consensus on the clinical value of the measurements.

Animals↗

PubMed2003

Heart rate increases linearly in response to acute isovolemic anemia.

BACKGROUND: The cardiovascular response to acute isovolemic anemia in humans is thought to differ from that of other species. Studies of anesthetized humans have found either no change or a decreased heart rate. A previous study showed that in 32 healthy unmedicated humans, heart rate increased during acute isovolemic anemia. The hypothesis that heart rate in humans increases in response to acute isovolemic anemia and that the increase is affected by gender was tested. STUDY DESIGN AND METHODS: Acute isovolemic anemia to a Hb concentration of approximately 5 g per dL in 95 unmedicated healthy humans was produced by simultaneous withdrawal of blood and IV replacement with 5-percent HSA and autologous platelet-rich plasma. The relationship between heart rate and Hb concentration was examined using a mixed-effects linear regression model that allowed each person to have a fitted line with its own slope and intercept. Cubic and quadratic terms were added to determine if these improved the goodness of fit. The effect of gender was tested by including it and its interactions with Hb in the mixed model. RESULTS: The relationship between heart rate and Hb concentration was linear (p < 0.001) and consistent among the population studied: heart rate = 116.0-4.0 [Hb] (slope 95% CI: -4.2 to -3.8 beats/min/g Hb). Adding a cubic or quadratic term did not significantly improve the goodness of fit of the mathematical expression to the data, confirming the linear nature of the relationship between heart rate and Hb concentration. For women, the slope of the heart rate response was significantly greater than it was for males (difference +/- SE: 0.70 +/- 0.23, p < 0.005). CONCLUSION: In 95 unmedicated, healthy humans, heart rate was a linear function of Hb during acute isovolemic anemia. Females had a significantly greater slope of increase in heart rate with decreasing Hb concentration than did males. The relationship is consistent among individuals, is similar to that reported for conscious dogs, and differs from that found previously in anesthetized humans.

Acute Disease↗

PubMed2002

Quantification and stratification: wound research in the future.

Advances in wound healing have been slow--from the realization of a concept through to its adoption into clinical practice. There are well-known and understood reasons for this conservative approach. One less well-tried thought is to stratify the patient's physiological status with regard to the wound. This may be the key to quantify changes in wound milieu and therefore to progress.

Journal Article↗