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Biomedical subjects

J W May

Publications and source records attributed to J W May.

At least 19 recordsLinked to original sources
PubMed2000

Epidemiology, prevention, and early detection of breast cancer.

Decreases in the incidence of breast cancer have not been achieved, but there is a downward trend in age-adjusted breast cancer mortality rates in the United States. Recent epidemiologic investigations continue to refine our understanding of the role of established breast cancer risk factors, such as reproductive characteristics and body mass index, and in the process advance understanding of the etiology of breast cancer. Important strides are being made in the chemoprevention of breast cancer, but clarifying the potential contributions of factors such as diet, physical activity, and cigarette smoke to the breast cancer burden is a high priority because these lifestyle behaviors also have important implications for primary prevention. The role of both environmental and endogenous exposures in breast carcinogenesis will be more clearly elucidated by studies that account for genetic polymorphisms, some of which may lead to differential susceptibility to harmful agents.

Breast Neoplasms↗
PubMed1999

Flap perfusion mapping: TRAM flap after abdominal suction-assisted lipectomy.

This technique or its modification (using other dyes) may play a beneficial role in other clinical scenarios where the reconstructive plastic surgeon preoperatively needs to know the integrity of vessels that are too small to image using standard angiographic techniques. In addition, flap perfusion mapping can demonstrate the pattern of skin that is physiologically perfused by the intact vessels. Knowledge of the perfusion characteristics of the tissues to be transferred before surgery may, at the least, alter the design of the tissues to be transferred and, in the extreme case, could affect the nature of the operative choice altogether.

Abdominal Muscles↗
PubMed1999

The tumescent technique: the effect of high tissue pressure and dilute epinephrine on absorption of lidocaine.

Injection of lidocaine into the subcutaneous tissues by the tumescent technique results in a delayed absorption of the local anesthetic and has allowed clinicians to exceed the maximum recommended dose of lidocaine without reported complications. However, little knowledge exists about the mechanisms that permit such high doses of lidocaine to be used safely with this technique. The presence of low concentration epinephrine and the increased tissue pressure resulting from the tumescent injection have both been implicated as important factors, but neither has been studied in patients whose results were not altered by the variability of the suction procedure. The purpose of this work was to determine the effect of tissue pressure during tumescent injection and presence of low concentration epinephrine on the absorption of lidocaine from subcutaneous tissues in human volunteers. Twenty healthy female human volunteers were randomized into four study groups. After body fat measurements, all subjects received an injection of 7 mg/kg of lidocaine into the subcutaneous tissues of both lateral thighs. The injected solution consisted of 0.1% lidocaine and 12.5 meq/liter sodium bicarbonate in normal saline with or without 1:1,000,000 epinephrine. Tissue pressure was recorded during injection using a specially designed double-barreled needle. The time required for injection was also recorded. Subjects in group 1 received lidocaine with epinephrine injected by a high-pressure technique. Group 2 subjects received lidocaine with epinephrine injected by a low-pressure technique. Group 3 subjects received lidocaine without epinephrine injected under high pressure. Group 4 subjects received lidocaine without epinephrine injected under low pressure. Following injection, sequential blood samples were drawn over a 14-hour period, and plasma lidocaine concentrations were determined by gas chromatography. No suction lipectomy was performed. Maximum tissue pressure during injection was 339 +/- 63 mmHg and 27 +/- 9 mmHg using high- and low-pressure techniques, respectively. Addition of 1:1,000,000 epinephrine, regardless of the pressure of injected fluid, significantly delayed the time to peak plasma concentration by over 7 hours. There was no significant difference in the peak plasma concentration of lidocaine among the four groups. Peak plasma concentrations greater than 1 mcg/ml were seen in 11 subjects. Epinephrine (1:1,000,000) significantly delays the absorption of lidocaine administered by the tumescent technique. High pressure generated in the subcutaneous tissues during injection of the solution does not affect lidocaine absorption. The delay in absorption may allow time for some lidocaine to be removed from the tissues by suction lipectomy. In addition, the slow rise to peak lidocaine concentration in the epinephrine groups may allow the development of systemic tolerance to high lidocaine plasma levels.

Absorption↗
PubMed1998

Late digital replantation failure: pathophysiology and risk factors.

It is generally accepted that replanted digits surviving at least 1 week following surgery rarely succumb to ischemic necrosis. Presented here are 2 patients who experienced late digital replantation failure. The first patient is an 8-year-old boy who had his index finger replanted at the proximal phalangeal level. After 16 days of viability, the replanted digit became swollen and subsequently necrosed. The second patient is a 35-year-old man with a history of smoking and intravenous drug use who underwent replantation of his avulsed thumb at the metacarpophalangeal joint. The replanted thumb was viable at the 2-week follow-up, but began to show ischemic changes at 3 weeks and eventually required revision amputation at the interphalangeal level. Both of these patients demonstrate late digital replantation failure--an unusual and poorly understood phenomenon. A discussion of possible risk factors and potential pathophysiology is presented.

Adult↗
PubMed1998

Monoclonal antibody to intercellular adhesion molecule 1 protects skin flaps against ischemia-reperfusion injury: an experimental study in rats.

The purpose of this study was to evaluate the blockage of polymorphonuclear neutrophil endothelial adhesion by using a monoclonal antibody to the intercellular adhesion molecule 1 (ICAM-1) ligand to prevent ischemia-reperfusion injury in rat skin flaps. A skin and subcutaneous tissue flap (3.0 cm x 4.5 cm) supplied by the superficial epigastric artery and vein including the femoral vessels was isolated unilaterally in 45 male Sprague-Dawley rats and clamped for 9 hours (groups II and III) or 12 hours (groups IV and V) of ischemia. Five animals in group I were sham-operated only with 5 minutes of ischemia. Animals in groups II (n = 10) and IV (n = 10) received 0.05 mg of monoclonal antibody to ICAM-1 (0.20 mg/kg) in 0.5 ml of 0.9% normal saline intravenously 15 minutes before reperfusion; those in groups III (n = 10) and V (n = 10) received 0.5 ml of normal saline. The flaps were assessed histologically, by measuring viable and nonviable areas, and by diffuse reflectance spectroscopy to determine the ratio of oxyhemoglobin to deoxyhemoglobin. Flap measurements revealed that the average area of flap survival was 90.6 +/- 12.8 percent in group II and 18.3 +/- 19.6 percent in the control group (III) (p < 0.002). In the animals subjected to 12 hours of ischemia, those treated with monoclonal antibody to ICAM-1 (group IV) were 57.1 +/- 23.1 percent viable, which was significantly greater than the control animals (group V), in which only 0.3 +/- 1.0 percent of the flap was viable. Analysis of the diffuse reflectance spectra showed a hyperemic response during the first 10 minutes after reperfusion in animals treated with monoclonal antibody to ICAM-1. In group III, however, the spectra demonstrated a decreased amount of oxyhemoglobin, indicating decreased reperfusion of the flap after ischemia when compared with group II. Histopathologically, few inflammatory changes could be observed in groups I, II, and the viable areas of group IV. Marked damage was observed in groups III and V. We concluded that treating ischemic skin flaps with monoclonal antibody to ICAM-1 was effective for alleviating reperfusion injury after 9 or 12 hours of warm ischemia. The reactive hyperemic response determined by diffuse reflectance spectroscopy in groups II and IV correlated with areas of flap survival. Antibodies to particular adhesion molecules, such as ICAM-1, have potential clinical utility in that they could be administered, individually or together, to patients immediately before reestablishing perfusion after free-tissue transfer or replantation to block the adverse effects attributed to reperfusion injury.

Animals↗
PubMed1996

Late rupture of a flexor tendon after electrical injury: tendon localization using magnetic resonance imaging. A case report.

Rupture of a flexor tendon in the nonrheumatoid population is rare. Localizing the level of the tendon rupture can be a difficult task. We describe an individual who presented with the sudden inability to flex the index finger of the hand, which had been subjected to a severe electrical injury. Physical exam demonstrated lack of index finger flexion at the distal joint. The patient denied any pain or history of recent trauma. Preoperative magnetic resonance imaging (MRI) successfully located the proximal and distal ends of the ruptured flexor digitorum profundus tendon in the forearm. MRI allows for accurate preoperative assessment of tendon position and degree of retraction, thereby facilitating surgical planning and approach. Accurate localization of tendon pathology preoperatively minimizes unnecessary dissection, shortens the operative procedure, and clarifies operative planning.

Arm Injuries↗
PubMed1996

Bacterial growth in saline implants: in vitro and in vivo studies.

The survival of bacteria was evaluated in custom-made saline breast implants with integral injection ports in vitro and in 10 New Zealand White rabbits for Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Serratia marcescens. Pseudomonas and Serratia survived in vitro in saline-filled implants and multiplied 24-fold and 22-fold, respectively, from the initial inocula of 300 colony-forming units per cubic centimeter in 21 days. Serratia alone survived in saline implants placed on the dorsum of rabbits, proliferated 80-fold in 7 days, and tapered to 10-fold at the end of 3 weeks. Chemical analysis revealed the presence of glucose in fluid from the implants in the animal study (mean, 1.2 mg per deciliter; standard error of mean [SEM], 0.6) after 21 days and from human subjects (mean, 3.8 mg per deciliter; SEM, 1.0) after 8 months to 10 years. Serratia incubated in human breast implant fluid samples proliferated 7-fold to 30-fold greater than in the saline control in a nonaerated environment. We conclude that some bacteria are able to proliferate in saline in breast implants. Furthermore, their survival may be facilitated by a substance (i.e., glucose) that diffuses across the implant outer shell.

Animals↗
PubMed1996

Effects of laser versus scalpel tenolysis in the rabbit flexor tendon.

The use of surgical lasers has been shown to decrease adhesion formation as compared with scalpel control groups in various surgical procedures. The potential benefits of laser technology have not been assessed in the treatment of adherent tendons. The current study was designed to first develop a reliable and reproducible model for consistent adhesion formation following flexor tendon trauma. The second goal was to compare the effects of laser tenolysis procedures on tendon gliding with those of traditional scalpel tenolysis. In phase I, the adhesion-induction model utilized bilateral standardized crush- abrasion injuries to the hind limb digital flexor tendons of New Zealand White rabbits. Following 4 weeks of immobilization, the animals were sacrificed, and peritendoneal adhesions were assessed biomechanically. A significantly higher maximal force was required to extract the adherent tendons from the foot as compared with nontraumatized control tendons. In phase II, six groups of animals underwent the same standardized tendon trauma. Four weeks later the rabbits were randomly assigned to undergo either CO2 laser or holmium:YAG laser tenolysis on one foot. Scalpel lysis was used on the contralateral foot and served as an intraindividual control. Biomechanical assessment was performed at 1, 2, and 4 weeks following tenolysis. Significantly less force was required to extract the treated tendons at 1 and 2 weeks following holmium:YAG laser tenolysis when compared with scalpel or CO2 laser tenolysis. After 4 weeks, differences between holmium:YAG and CO2 laser and scalpel treatment were no longer significant. Extracted tendons were pulled apart to failure, and no difference in breaking strength was noted between groups. We conclude that holmium:YAG laser tenolysis results in easier tendon gliding as compared with scalpel or CO2 laser tenolysis at early time points. Laser tenolysis does not affect intrinsic tendon strength.

Anesthesia, General↗
PubMed1996

Prevention of microvascular thrombosis with short-term infusion of human tissue-type plasminogen activator.

A locally active thrombolytic agent, human tissue-type plasminogen activator (t-PA), given over a finite time period (24 hours) by local infusion, maintains long-term microvascular patency (7 days) in a proven thrombosis model using an arterial inversion graft in the rabbit model. Thirteen rabbits in the control group and 16 rabbits in the experimental group underwent an arterial inversion graft followed by continuous infusion (24 hours) with human tissue-type plasminogen activator (experimental) or normal saline (control). No significant clinical bleeding or alteration of coagulation parameters was noted in hematologic studies in both experimental and control groups. Scanning electron microscopy of the postoperative human tissue-type plasminogen activator-perfused arteries suggests an interaction of the human tissue-type plasminogen activator with specific platelet receptors in reversing microvascular thrombosis by decreasing or preventing further platelet aggregation and adhesion. Human tissue-type plasminogen activator infused locally for a finite period (24 hours) allows adequate time for platelet metamorphosis to occur in converting a thrombogenic to a nonthrombogenic vessel surface. The clinical ramifications in preventing or reversing microvascular thrombosis in free-tissue transfers and replantation surgery are apparent. Further study in this area will enhance our understanding of the pathogenesis and prevention of microvascular thrombosis.

Anastomosis, Surgical↗
PubMed1996

Mechanical analysis of explanted silicone breast implants.

Smooth-walled silicone gel breast implants (n = 25) were removed from 15 women after implantation times that varied from 23 to 216 months (mean = 117 months; SEM = 12.9). Strips of implant shells were tested to failure by computer-controlled tensiometer. Regression analysis revealed significant negative correlation between age of implantation and shell strength (p < 0.05), shell toughness (p < 0.05), and shell elasticity (p < 0.05). These data suggest that exposure to the in vivo environment weakens silicone gel breast implant shells over time.

Breast Implants↗
PubMed1995

Augmented Becker versus modified Kessler tenorrhaphy in monkeys: dynamic mechanical analysis.

The strength and gliding efficiency of an augmented Becker and Kessler tendon repair techniques were compared in fresh cadaver macaque monkey hands. Gliding efficiency was determined by comparing tendon work and load measurements made during tendon excursion to full fist with the same measurements made after tendon repair. Repair strength was then determined by tendon distraction to complete repair rupture. Data were gathered by computer controlled tensiometer and analyzed by factorial and repeated measures ANOVA. The augmented Becker repairs were significantly stronger than Kessler repairs. Repaired tendons required more load and work to bring the fingers into full fist; both repair types resulted in gliding efficiencies of 30% compared to intact controls. The augmented Becker repair is significantly stronger in situ than the modified Kessler and is recommended when early postoperative motion regimens are planned.

Analysis of Variance↗
PubMed1995

Tissue expanders and magnetic resonance imaging: the "hot" breast implant.

Magnetic resonance imaging (MRI) utilizes three electromagnetic fields to create images. Despite these electromagnetic fields and concern for patients with metallic implants, studies and clinical experience have demonstrated the safety of this modality in the presence of nonferromagnetic implants. However, little has been written about the use of MRI scans in patients with tissue expanders. We present a case of a woman who developed a burning sensation at the site of her tissue expander during an MRI scan. The sensation resolved rapidly once the scan was discontinued. The potential for metallic heating or motion within the electromagnetic field is discussed. Patients with tissue expanders who require MRI scans should be carefully questioned about localized symptoms in the region of their expander during the scan. However, the actual implications of the symptoms for this group of patients are unclear.

Breast Implants↗
PubMed1995

The antithrombotic effects of ticlopidine and aspirin in a microvascular thrombogenic model.

In the effort to reduce a persistently significant failure rate in free tissue transfers and digital replantations, the efficacy of two oral platelet inhibitors, aspirin and ticlopidine, was examined using the arterial inversion graft, a known microvascular thrombogenic model. Forty male New Zealand White rabbits were used to create eighty 5-mm inversion grafts. Four groups were blindly given perioperative oral drug therapy: ticlopidine, aspirin, both, or neither (control). Vessel patency was evaluated at 1 hour and 1 week after surgery. The patency rate for the control group was 20 percent at 1 hour and 5 percent at 1 week. The drug-treated patency rates at 1 hour and 1 week, respectively, were 45 percent (p = 0.046) and 15 percent for ticlopidine, 35 percent and 10 percent for aspirin, and 45 percent (p = 0.046) and 20 percent for the combination therapy. This study shows that ticlopidine alone or in combination with aspirin significantly increases the 1-hour patency rates in a reliable thrombosis model, but it fails to show a significant increase in the final patency rates by either drug administered alone or in combination. The benefit in clinical microvascular surgery of either aspirin or ticlopidine is not determined by this study.

Administration, Oral↗