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Biomedical subjects

T K Hunt

Publications and source records attributed to T K Hunt.

At least 109 records · Page 6Linked to original sources
PubMed1987

Local heat increases blood flow and oxygen tension in wounds.

The effect of local hyperthermia on subcutaneous tissue oxygen tension (Psqo2) and perfusion was investigated in eight patients (13 trials) using a subcutaneously implanted oxygen tonometer. Application of heat increased subcutaneous tissue temperature and Psqo2. Mean Psqo2 during oxygen breathing rose by 39.5 mm Hg, an 80% increase over the average baseline Psqo2. The corresponding mean subcutaneous temperature increased 4.0 degrees C. A significant linear correlation was found between the change in Psqo2 and subcutaneous temperature. There was an average threefold increase in local perfusion estimated by using the Fick principle. The data reaffirm the value of local hyperthermia in treating contaminated wounds and suggest a mechanism for its ability to ameliorate infections. The mechanism implies that local heat may have prophylactic value as well.

Blood Circulation↗
PubMed1987

Assessment of perfusion in postoperative patients using tissue oxygen measurements.

Subcutaneous tissue oxygen tension was measured as an index of perfusion in 44 postoperative patients. Hypoperfusion was defined as suboptimal tissue oxygen tension unresponsive to increased inspired oxygen but becoming responsive after increased fluid infusion. Twelve of thirty patients who underwent major abdominal and flank operations were found to be suboptimally perfused by this definition despite adequate fluid maintenance according to standard clinical criteria including urine output. Apparently, a significant number of postoperative abdominal surgery patients are not optimally perfused, and this state is not recognized by the present clinical criteria. Tissue oximetry may be a useful objective method of assessing tissue perfusion.

Blood Gas Analysis↗
PubMed1987

Cardiac cryolesions as an experimental model of myocardial wound healing.

The standard coronary ligation model for experimental myocardial infarction results in variable areas and patterns of necrosis; therefore, the healing of such infarctions is also variable. The authors developed an experimental myocardial injury model using simple cryoinjury, which allows standardization of the size, depth, and location of the wound. Thirty-eight left ventricular cryolesions were created in 19 dogs, which were then killed from 3 to 35 days after injury. A consistent decrease in the depth of scar (p less than 0.005) and accumulation of collagen (p less than 0.0001) over time characterized this healing myocardial wound. Histologic examination revealed that the cellular pattern of healing myocardial cryolesions is similar to that of a healing myocardial infarction but with less variability. The authors advocate the use of cardiac cryolesions as a model of experimental myocardial wound healing.

Animals↗
PubMed1987

Directly measured tissue oxygen tension and arterial oxygen tension assess tissue perfusion.

Mean subcutaneous tissue PO2 (PsqO2) measurements were obtained in dogs with an unheated electrode placed in an implanted Silastic tonometer, while PaO2 was increased in increments from 40 to 600 torr during normal, increased, and reduced blood volume. These changes reflect that the mean PsqO2 is approximately 10 torr below the PO2 of venous blood draining that tissue. Since PaO2 was already known, the oxygen content of arterial and venous blood entering and leaving this tissue could be determined by reference to blood-oxygen dissociation curves. Therefore, relative changes in blood flow could be calculated using the Fick principle. After a 20% blood loss, the PsqO2 measured during breathing of room air fell to 20% of baseline, corresponding to an 80% fall in sc blood flow; it remained low until the shed blood was returned despite compensatory changes in cardiac output. Rapid infusion of electrolyte solutions in normovolemic animals produced a temporary increase in local blood flow. Subcutaneous oximetry seems capable of quantifying peripheral perfusion and may be clinically useful.

Animals↗
PubMed1987

Subcutaneous tissue oxygen tension falls during hemodialysis.

The effect of hemodialysis on subcutaneous tissue oxygen tension was studied in nine patients. During hemodialysis, blood pressure decreased, pulse increased, and all patients lost weight. Arterial blood oxygen tension fell insignificantly, from 79 to 73 mm Hg. Subcutaneous oxygen tension decreased from 52 to 28 mm Hg (p less than 0.001). Because adequate tissue oxygenation is necessary for wound healing and resistance to infection, we postulate that hemodialysis may contribute to the wound morbidity frequently seen in dialyzed patients.

Adult↗
PubMed1986

Oxygen as an antibiotic. A comparison of the effects of inspired oxygen concentration and antibiotic administration on in vivo bacterial clearance.

Since prophylactic antibiotics and changes in tissue partial pressure of oxygen may affect bacterial clearance by different mechanisms, we tested the effects of hypoxia, hyperoxia, and normoxia with and without antibiotic administration on bacterial clearance. We found that improving tissue oxygenation by administration of normobaric oxygen decreased infectious necrosis as effectively as prophylactic antibiotic administration and that improved tissue oxygenation and antibiotic administration had an additive effect. We believe that a fraction of inspired oxygen of 45% should be added to prophylactic antibiotics as standard perioperative and postoperative care.

Ampicillin↗
PubMed1986

Primary aldosteronism: changing concepts in diagnosis and management.

Unilateral adrenalectomy for benign causes of primary aldosteronism is an established procedure. The established surgical cure for aldosterone-producing adenoma justifies a thorough preoperative evaluation. No single test accurately identifies aldosterone-producing adenomas in patients with primary aldosteronism. However, a useful algorithm combines postural studies, computerized axial tomography, and adrenal vein catheterization for selective hormonal assay, if computerized axial tomography is negative or equivocal and the suspicion of aldosterone-producing adenoma is high. If an adrenal mass is present and biochemical studies suggest a diagnosis of aldosterone-producing adenoma, resection of the affected gland from a limited unilateral approach is indicated. Cure can be expected in 80 percent of cases. In the uncommon circumstance that the adrenal tumor was not an aldosterone-producing adenoma but a hyperplastic nodule, these patients may still be cured or more easily controlled with antihypertensive medications. Thirty-eight patients who underwent unilateral adrenalectomy are presented and discussed.

Adenoma↗
PubMed1986

Vitamin A and wound healing.

Retinoids have long been associated with wound healing, but objective data, until recently, have been scarce. Vitamin A deficiency retards repair. Secondly, retinoids restore steroid-retarded repair toward normal. Because vitamin A tends to suppress fibroblasts in cell culture and stimulate steroid-treated macrophages to initiate reparative behavior in tissue, we favor the hypothesis that retinoids are particularly important in macrophagic inflammation, which plays a central role in the control of wound healing. Probably all patients who take anti-inflammatory steroids should control their retinoid intake, but how they should control it is as yet unknown.

Animals↗
PubMed1986

Wound collagen accumulation in obese hyperglycemic mice.

We used C57-BL ob/ob mice as a model to study wound healing in type II (adult-onset) diabetes. Planimetry was used to assess rate of closure in standard open skin wounds. In agreement with previous subcutaneous wound collagen-accumulation studies, closure was slower in the ob/ob mice. Subcutaneous implants were used to evaluate wound collagen accumulation. Weanling mice have collagen accumulation similar to lean littermates (mean 3.43 micrograms/cm vs. 3.46 micrograms/cm), but the same ob/ob animals had decreased wound collagen (mean 2.39 micrograms/cm vs. 3.02 micrograms/cm, P less than 0.04) when mature. Other ob/ob animals fed a restricted diet (and thus not obese) had normal collagen accumulation at the same age. Neither insulin nor diet restriction restored wound collagen accumulation in phenotypically obese mice. Because collagen accumulation is not improved by measures that control hyperglycemia (insulin and diet restriction) and the defect was seen only in phenotypically obese ob/ob mice, the decreased wound collagen accumulation may be due in part to structural changes in adipose tissue.

Adipose Tissue↗
PubMed1986

Effect of lactate, pyruvate, and pH on secretion of angiogenesis and mitogenesis factors by macrophages.

Macrophages secrete substances that stimulate angiogenesis and mitogenesis at wound sites. To test whether metabolic characteristics of the wound such as high lactate concentration and low pH may regulate the expression of these substances, macrophages were cultured in lactalbumin hydrolysate and then in increasing concentrations of lactate, pyruvate, and hydrogen ions, and cell-free supernatants were collected. Cultures incubated in concentrations of lactate approximating those observed in wounds secreted an angiogenesis factor or factors, but cultures incubated in equivalent concentrations of pyruvate or at pH 6.2 did not. These observations seem to be specific to macrophages because capillary endothelial cells and fibroblasts failed to secrete an angiogenesis factor when cultured under hypoxic conditions or in high concentrations of lactate. None of these conditions changed the expression of macrophage mitogens.

Angiogenesis Inducing Agents↗
PubMed1985

Cell interactions in post-traumatic fibrosis.

Models of reparative fibrosis, or wound healing, disclose a basic spatial relationship between inflammatory cells, fibroblasts, dividing fibroblasts and angiogenic endothelial cells. Many components of the extracellular fluid, especially steep gradients of PO2, PCO2, pH, glucose and lactate, have been measured. After components of coagulation play out their role in the first few days after injury, macrophages sense excitatory substances and signs of respiratory distress, and secrete chemoattractants for endothelial cells and fibroblasts. If excitatory substances (such as silica) are eliminated, active fibrosis ends with the restoration of the energy supply. Some of the mitogens and chemoattractants acting as intercellular messengers between these cells have been isolated and identified.

Animals↗
PubMed1985

What do breast symptoms mean?

Breast symptoms of pain, tenderness, and engorgement correlate with objective findings of nodularity on physical examination. Like all other factors for breast disease, they are not a single determinant of diagnosis, as shown by the 3 X 3 contingency table, but they are a useful addition to our understanding. From the available data, symptoms seem as accurate as physical examination for evaluating changes in benign diseases. By extrapolation, we expect they will be useful for management of premalignant breast lesions. We conclude that a complete breast evaluation should include inquiry about breast symptoms and whether these symptoms have changed.

Adult↗