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Biomedical subjects

Harriet W Hopf

Publications and source records attributed to Harriet W Hopf.

18 recordsLinked to original sources
PubMed2006

Using physiology to improve surgical wound outcomes.

Despite major advances in surgical management and approaches, including aseptic techniques, prophylactic antibiotics, and laparoscopic surgery, surgical wound infection and wound failure remain common complications of surgery. In a review of the literature, the authors found that a growing body of literature supports the concept that patient factors are a major determinant of wound outcome after surgery. In particular, wounds are exquisitely sensitive to hypoxia, which is both common and preventable. Perioperative management can be adapted to promote postoperative wound healing and resistance to infection. The most important factors are fluid management, temperature management, pain control, increased arterial oxygen tension, and, as has been long recognized, appropriate sterile techniques and administration of prophylactic antibiotics. This article reviews how knowledge of and attention to physiology can improve quality of care in both acute and chronic wounds.

Antibiotic Prophylaxis↗
PubMed2005

Acute isovolemic anemia impairs central processing as determined by P300 latency.

OBJECTIVE: Acute anemia slows the responses to clinical tests of cognitive function. We tested the hypothesis that these slowed responses during acute severe isovolemic anemia in healthy unmedicated humans result from impaired central processing. METHODS: A blinded operator measured the latency of the P300 peak in nine healthy volunteers at each volunteer's baseline hemoglobin concentration (Hb), and again after isovolemic hemodilution to Hb 5 g/dL. At both Hb concentrations, the P300 latency was measured twice: with the blinded subject breathing air or 100% oxygen, administered in random order. RESULTS: Anemia increased P300 latency significantly from baseline values (P < 0.05). Breathing oxygen during induced anemia resulted in a P300 latency not different from that at baseline when breathing air (P = 0.5) or oxygen (P = 0.8). CONCLUSIONS: Impaired central processing is, at least in part, responsible for the slowed responses and deficits of cognitive function that occur during acute isovolemic anemia at Hb 5-6 g/dL. SIGNIFICANCE: The P300 latency appears to be a potential measure of inadequate central oxygenation. In healthy young adults with acute anemia, erythrocytes should be transfused to produce Hb>5-6 g/dL. As a temporizing measure, administration of oxygen can reverse the cognitive deficits and impaired central processing associated with acute anemia.

Adult↗
PubMed2005

Facilitating positive outcomes in older adults with wounds.

Older people with wounds are not the same as younger people with wounds. Older people experience biologic differences in wound healing that result in delayed healing, increased wound infection, and a greater incidence of dehiscence. Clinicians need to assess the risk of dehiscence in the older population, looking for serous drainage from the incision line and the absence of a palpable healing ridge. It is critical to recognize that older persons' presentation of wound infection is atypical. More subtle signs such as alteration in cognitive status and changes in function may indicate the presence of infection. The clinician who cares for older persons must be an exquisite detective when such changes occur to identify the source of the problem. As part of the normal trajectory of aging, older persons experience sensory loss and so may require accommodation when explanations are given to them about their wound and their wound care choices. Health care providers must consider hearing and vision changes that occur in older adults and tailor their explanations and teaching so that the message reaches the older adult and is successfully processed. Older persons have a higher incidence of cognitive changes and functional decline than do their younger counterparts, and these changes need to be assessed before a plan of care is developed to care for the older person with a wound. Limited data are available to help the clinician know the cognitive and functional level that is critical for older persons to understand their wound care choices, perform their own wound care, and to make choices about who will provide the care if they are unable to perform self-care. These seemingly basic issues raise questions for clinicians as we strive to provide evidence-based care to this ever-increasing population of older Americans.

Activities of Daily Living↗
PubMed2005

Development of a new geometric bicycle saddle for the maintenance of genital-perineal vascular perfusion.

OBJECTIVE: To identify a bicycle saddle model for cyclists who cover long distances, to minimally reduce the compression on the structures of the pelvic floor, thereby protecting blood perfusion of the penis and avoiding possible consequences on penile erection. MATERIALS AND METHODS: A comparison between a new geometric development of a bicycle saddle model (SMP) and one of the more frequently used models by professional cyclists was made. The measurement of the partial pressure of penile transcutaneous oxygen (PtcO(2)) in 29 healthy voluntary cyclists was recorded to investigate the differences of compression from two different saddles on the vascular structures of the perineum. The PtcO(2) was recorded at 3 and 10 minutes in conditions of static sitting. Then, the values of PtcO(2) were recorded for 15 minutes while the cyclists were in a 60-degree position and in stable hemodynamic conditions. RESULTS: A t-test was performed to measure the level of confidence. The clear superiority of the SMP saddle in preventing vascular compression of the perineal structures was demonstrated to be statistically significant. CONCLUSION: The experiment validated the effectiveness of the SMP saddle in limiting the compression on the pelvic floor. In addition, the SMP saddle introduces compatible seat dimensions that cyclists prefer to cover long distances.

Adolescent↗
PubMed2003

The link between tissue oxygen and hydration in nursing home residents with pressure ulcers: preliminary data.

Pressure ulcers are prevalent in nursing home residents. They heal slowly and result in pain and impaired quality of life. Strategies to enhance healing of pressure ulcers are critical to the treatment regime in nursing homes. This article explores the possibility that nursing home residents with pressure ulcers may experience low tissue oxygen and impaired hydration. Pilot data are presented suggesting that some proportion of nursing home residents with pressure ulcers experience low subcutaneous oxygen and that fluid administration increases the low tissue oxygen. Further research in this area is warranted.

Aged↗
PubMed2003

Acute isovolemic anemia does not impair peripheral or central nerve conduction.

BACKGROUND: Previous studies have found subtle slowing of responses in tests of addition and digit-symbol substitution during acute severe isovolemic anemia to a hemoglobin concentration of 5 g/dl in healthy unmedicated humans. In this study, the authors tested the hypothesis that such changes relate to the slowing of afferent neural traffic. METHODS: The median nerve was stimulated at the wrist in seven healthy unmedicated volunteers before and after induction of acute isovolemic anemia to a nadir hemoglobin concentration of 5.1 +/- 0.3 g/dl (mean +/- SD). Times for neural impulses to travel from the stimulus site to the brachial plexus, cervical spinal cord, and cerebral cortex were measured using somatosensory evoked potentials. Tests were repeated during acute anemia with the subject breathing oxygen. As a control for time and intrasubject variation, the testing was repeated on a separate day when anemia was not produced at times equivalent to those on the experimental day. RESULTS: Induced acute severe isovolemic anemia decreased nerve conduction latencies from the wrist to the contralateral cerebral cortex (i.e., to the N20 peak) by 2.3 +/- 1.6% compared with values at a mean hemoglobin concentration of 12.7 g/dl (P < 0.01). These decreased latencies were due solely to an increased peripheral conduction velocity, from the wrist to the brachial plexus (P < 0.05), and were not altered when subjects breathed oxygen (P > 0.05). Conduction velocity from the brachial plexus or cervical spinal cord to the cerebral cortex did not change with acute anemia (P > 0.05). Latencies did not differ on the control day among the times of testing (all P > 0.05), nor did they differ at baseline between the control and experimental days (all P > 0.05). CONCLUSION: Somatosensory evoked potential latencies were not increased by acute severe isovolemic anemia, making it unlikely that the afferent portion of the neural system is responsible for slowing of cognitive responses previously observed during acute anemia. Because severe isovolemic anemia did not increase somatosensory evoked potential latencies, etiologies other than anemia should be sought if latencies are increased during intraoperative monitoring.

Acute Disease↗
PubMed2003

Molecular diagnostics of injury and repair responses in critical illness: what is the future of "monitoring" in the intensive care unit?

OBJECTIVE: To identify potential future means of monitoring injury and repair in critical illness. DESIGN: Review of the literature. RESULTS: Critically ill patients are monitored extensively and intensively by such means as hemodynamics, laboratory values, and radiologic studies. In general, however, the goal of monitoring has been to measure the degree of injury and to prevent further injury, rather than to measure repair. Measures of repair have been limited to phenotypic end points such as return of organ function, as measured by blood chemistry. In this article, I examine how it may be possible in the future to monitor the progress of repair using genomic and proteomic biomarkers. These types of monitors would enable clinicians to control the healing environment using real time, rapid biomarkers, and sophisticated techniques to target therapy to the patient's current inflammatory state, taking into account the genetic makeup of the patient and his or her likely response to a given drug. CONCLUSIONS: The rapidly evolving sciences of genomics, proteomics, computational biology, and complex system theory can be used a) to model critical illness; b) to model adaptive and maladaptive responses to critical illness; c) to tailor treatments to create an ideal inflammatory environment for repair and regeneration, taking into account the individual genetic contribution; and d) to monitor the progress of repair. The major obstacles to reaching these goals are technological, and experience suggests that they will be overcome.

Adaptation, Physiological↗
PubMed2003

Paradigm of the injury-repair continuum during critical illness.

OBJECTIVES: To define injury and repair in the context of critical illness. DESIGN: Review of the literature. RESULTS: The medical practice of critical care medicine has long been one of aggressive assistance and support: utilizing state of the art technology to support the functions of the human body until homeostasis is again achieved and the patient is functioning sufficiently to allow the support to discontinue. Injury is defined as the disruption of molecular, cellular, or organ functions resulting from an external or internal stimulus. Repair is defined as an adaptive process that occurs in response to injury and involves both local and systemic responses that serve to restore structure and regulation for the purpose of organ/tissue function. The study of injury in critical illness is now occurring "upstream," at the genetic and cellular levels, to understand how damaging effects of acute inflammation from injury can be prevented or modulated. CONCLUSION: To treat the patient with critical illness more effectively, it is important to understand both the cause of the insults and the repair processes triggered by the insults because both processes affect the eventual course of the critical illness.

Adaptation, Physiological↗
PubMed2002

Oxygen reverses deficits of cognitive function and memory and increased heart rate induced by acute severe isovolemic anemia.

BACKGROUND: Erythrocytes are transfused to improve oxygen delivery and prevent or treat inadequate oxygenation of tissues. Acute isovolemic anemia subtly slows human data processing and degrades memory, increases heart rate, and decreases self-assessed energy level. Erythrocyte transfusion is efficacious in reversing these effects of acute anemia. We tested the hypothesis that increasing arterial oxygen pressure (Pao2) to 350 mmHg or greater would supply sufficient oxygen to be equivalent to augmenting hemoglobin concentration by 2-3 g/dl and thus reverse the effects of acute anemia. METHODS: Thirty-one healthy volunteers, aged 28 +/- 4 yr (mean +/- SD), were tested with verbal memory and standard, computerized neuropsychologic tests before and twice after acute isovolemic reduction of their hemoglobin concentration to 5.7 +/- 0.3 g/dl. Two sets of tests were performed in randomized order at the lower hemoglobin concentration: with the volunteer breathing room air or oxygen. The subject and those administering the tests and recording the results were unaware which gas was administered. As an additional control for duration of the experiment, 10 of these volunteers also completed the same tests on a separate day, without alteration of hemoglobin concentration, at times of the day similar to those on the experimental day. Heart rate, mean arterial blood pressure, and self-assessed sense of energy were recorded at the time of each test. RESULTS: Reaction time for digit-symbol substitution test increased, delayed memory was degraded, mean arterial pressure and energy level decreased, and heart rate increased at a hemoglobin concentration of 5.7 g/dl (all P < 0.05). Increasing Pao2 to 406 +/- 47 mmHg reversed the digit-symbol substitution test result and the delayed memory changes to values not different from those at the baseline hemoglobin concentration of 12.7 +/- 1.0 g/dl, and decreased heart rate (P < 0.05). However, mean arterial pressure and energy level changes were not altered with increased Pao2 during acute anemia. CONCLUSION: The authors confirmed that acute isovolemic anemia subtly slows human reaction time, degrades memory, increases heart rate, and decreases energy level. The findings of this study support the hypothesis that increasing Pao2 to 350 mmHg or greater by breathing oxygen reverses all of these effects of acute anemia except for decreased energy.

Acute Disease↗
PubMedDate not supplied

Development of subcutaneous wound oxygen measurement in humans: contributions of Thomas K Hunt, MD.

When, in the early 1960s, Thomas K. Hunt, MD began investigating the role of oxygen in wound healing, he recognized that translation to humans would require the ability to measure oxygen tension in human wounds. This article will review his contributions to the development of subcutaneous tissue oxygen measurement and to the understanding of wound physiology and oxygen delivery, particularly through use of oxygen measurement. Hunt's major contributions to the field include the observations that all wounds show some degree of hypoxia, while many are severely hypoxic; the degree of hypoxia in wounds is sufficient to impair wound healing, and particularly bacterial killing by neutrophils, collagen deposition, angiogenesis, and epithelization; the sympathetic nervous system plays a central role in decreasing wound oxygen supply; and wound oxygen delivery and wound healing capacity can be increased by controlling the sympathetic nervous system. All these observations required tissue oxygen measurement, and, in particular, translation of basic scientific observations to clinical research required a method of measuring wound oxygen tension in humans.

Cell Hypoxia↗
PubMedDate not supplied

Hyperoxia improves microvascular perfusion in a murine wound model.

There is a need for a noninvasive method that measures wound angiogenesis. Hyperoxia is known to increase the appearance of new blood vessels in wounds, yet no study has confirmed increases in wound bed perfusion with periodic hyperbaric oxygen (HBO) exposure. This study investigates whether laser Doppler imaging is able to detect and quantify the enhancement of wound angiogenesis that is known to occur with intermittent HBO treatments. Full-thickness dorsal dermal wounds were created on mice randomized to hyperoxic (n = 14) and control (n = 15) groups. Hyperbaric oxygen was administered twice daily for 90 minutes each at 2.1 atmospheres for 7 days. Wound bed perfusion was measured by laser Doppler imaging on days 0, 7, and 10 postwounding. Wound blood flow increased significantly over baseline on day 7 and 10 in the hyperoxic group, but only on day 10 in the control group. Comparison between groups showed a 20% statistically significant increase in wound perfusion in HBO-treated animals compared to control on day 10 (p = 0.05). Laser Doppler imaging was able to detect and quantify the increase in wound bed perfusion resulting from intermittent HBO treatments and shows promise as a noninvasive measure of angiogenesis and wound healing.

Animals↗
PubMedDate not supplied

Hyperoxia and angiogenesis.

We hypothesized that tissue hyperoxia would enhance and hypoxia inhibit neovascularization in a wound model. Therefore, we used female Swiss-Webster mice to examine the influence of differential oxygen treatment on angiogenesis. One milliliter plugs of Matrigel, a mixture of matrix proteins that supports but does not itself elicit angiogenesis, were injected subcutaneously into the mice. Matrigel was used without additive or with added vascular endothelial growth factor (VEGF) or anti-VEGF antibody. Animals were maintained in hypoxic, normoxic, or one of four hyperoxic environments: hypoxia -- 13 percent oxygen at 1 atmosphere absolute (ATA); normoxia -- 21 percent oxygen at 1 ATA; hyperoxia -- (groups a-d) 100 percent oxygen for 90 minutes twice daily at the following pressures: Group a, 1 ATA; Group b, 2 ATA; Group c, 2.5 ATA; Group d, 3.0 ATA. Subcutaneous oxygen tension was measured in all groups. The Matrigel was removed 7 days after implantation. Sections were graded microscopically for the extent of neovascularization. Angiogenesis was significantly greater in all hyperoxic groups and significantly less in the hypoxic group compared with room air-exposed controls. Anti-VEGF antibody abrogated the angiogenic effect of both VEGF and increased oxygen tension. We conclude that angiogenesis is proportional to ambient pO(2) over a wide range. This confirms the clinical impression that angiogenesis requires oxygen. Intermittent oxygen exposure can satisfy the need for oxygen in ischemic tissue.

Animals↗