Effects of nerve growth factor on nerve regeneration through a vein graft across a gap.

The limited availability of donor sites for nerve grafts and their inherent associated morbidity continue to stimulate research toward finding suitable alternatives. In the following study, the effect of direct administration of nerve growth factor (NGF) into a nerve conduit across a gap was tested in a rat sciatic nerve model. A 1-cm segment of the right sciatic nerve in Sprague-Dawley rats was resected, and the gap was then bridged using one of three methods: group I (NGF-treated group, n = 12), a vein graft filled with NGF (100 ng in 0.3-ml phosphate buffered saline); group II (control group, n = 12), a vein graft filled with phosphate buffered saline only; group III (standard nerve graft, n = 11), a resected segment of the sciatic nerve. All animals were evaluated at 3 and 5 weeks by behavioral testing and at 5 weeks by electrophysiologic testing. At 3 weeks, sensory testing showed that the latency to a noxious stimulus in group I animals (8.0 +/- 5.4 sec, mean +/- SD) was significantly lower than that of group II animals (13.2 +/- 6.5 sec), indicating that sensory recovery was superior in the animals receiving NGF. The mean latency of animals in group III was 12.9 +/- 6.5 sec, but the difference between the latencies of group I and group III did not reach statistical significance. At 5 weeks, there was no difference in sensory testing between groups. Motor function in groups I and III as measured by walk pattern analysis was superior to that of group II at 5 weeks (toe spread ratios 0.66 +/- 0.09, 0.48 +/- 0.07, and 0.69 +/- 0.09 for groups I, II, and III, respectively). Mean motor conduction velocities across the 1-cm gap were 8.6 +/- 4.7 m/sec, 2.5 +/- 0.7 m/sec, and 6.9 +/- 2.9 m/sec in groups I, II, and III respectively. The difference between groups I and III was not statistically significant, but the motor conduction velocity of group II was significantly slower than that of either group I or III (p < 0.002). The positive effects of NGF on regeneration of nerves across a gap seen in this study suggest that it may be useful for treating peripheral nerve injuries in combination with autogenous vein grafts.

Persistent or recurrent carpal tunnel syndrome following prior endoscopic carpal tunnel release.

A retrospective review of patients with carpal tunnel syndrome (CTS) identified 20 patients (26 wrists) who had persistent or recurrent CTS after having undergone endoscopic carpal tunnel release (ECTR). Seven wrists never had relief of the original CTS symptoms; for the remaining 19 wrists, the average time to recurrence of CTS following ECTR was 4.8 months. All cases recurred within 12 months from the ECTR. All but 1 patient reported nocturnal pain. All patients experienced morning numbness and stiffness. All wrists had positive Phalen's test results. Once diagnosed with persistent or recurrent CTS, each of the wrists underwent open carpal tunnel release (OCTR). Twenty-two wrists were available for follow-up, with all patients reporting greater satisfaction and relief after the OCTR compared with the ECTR. It is important to recognize that CTS may persist or recur after ECTR. These patients should be treated with OCTR to provide symptomatic relief and prevent the sequelae of ongoing CTS.

Breast reconstruction in previously irradiated patients using tissue expanders and implants: a potentially unfavorable result.

There exists a paucity of definitive information on the suitability of implant reconstructions in previously irradiated breast cancer patients. This controversial topic prompted a review of our prosthetic reconstructions in this select group of patients. A retrospective study of patients treated between 1976 and 1993 with lumpectomy and radiation therapy for early breast cancer revealed 67 patients with local recurrences. Nine of these patients (10 breasts) underwent a two-stage prosthetic reconstruction following a salvage mastectomy. The average age was 47.9 years. The mean dose of irradiation was 6,070 cGy. The average interval from radiation therapy to placement of a tissue expander was 4.6 years. In one patient (10%) the tissue expander extruded. The average follow-up for 8 patients (9 breasts) who underwent exchange to a permanent prosthesis was 5.1 years. In four reconstructions (40%) there was an uneventful postoperative course. Two cases (20%) were difficult to expand and the final result lacked projection. One patient (10%) developed an infection requiring removal of the permanent prosthesis. Two patients (20%) developed Baker class III or IV capsular contractures. Overall, in our group of 10 implant reconstructions, 60% of the patients resulted in either a complication or an unfavorable result.

Free radial artery grafts: surgical technique and results.

In the search for alternative conduits, the use of radial artery (RA) grafts has found renewed interest. This study sought to evaluate prospectively the perioperative morbidity, including the postoperative complications in the donor forearm, and mortality in the routine use of RA grafts in coronary artery bypass surgery. Data were obtained prospectively on 200 consecutive patients who underwent coronary revascularization using at least one RA graft from January 1995 to April 1997. The mean age of the patents was 61.9+/-10.5 years (mean+/-standard deviation [SD]). The RA was obtained from one forearm in 197 patients and both forearms in 3 patients. Two patients (1%) required exploration for donor site hematomas, 4 patients (2%) had temporary perioperative dysesthesias in the region of the lateral cutaneous nerve of the forearm, and none had donor site wound infection. Two patients (1%) had a myocardial infarction with electrocardiographic changes in the areas grafted by the RA in the immediate postoperative period, indicating graft failure. The two deaths in the series were due to comorbid factors. Our data suggest that the RA is a safe and suitable conduit for coronary revascularization, and it provides good clinical results. Long-term follow-up of these patients is necessary to confirm the patency of RA conduits. Free RA grafts have the potential for use in other areas of surgery where a conduit is necessary for revascularization procedures.

Hazard screening of chemical releases and environmental equity analysis of populations proximate to toxic release inventory facilities in Oregon.

A comprehensive approach using hazard screening, demographic analysis, and a geographic information system (GIS) for mapping is employed to address environmental equity issues in Oregon. A media-specific chronic toxicity index [or chronic index (CI)] was used to compare environmental chemical releases reported in the EPA's Toxic Chemical Release Inventory (TRI) database. In 1992, 254 facilities reportedly released more than 40 million pounds of toxic chemicals directly into the environment on-site or transferred them to sewage treatment plants or other off-site facilities for disposal and recycling. For each reported on-site TRI chemical release, a CI based on oral toxicity factors and total mass was calculated. CIs were aggregated on a media-, facility-, and chemical-specific basis. Glycol ethers, nickel, trichloroethylene, chloroform, and manganese were ranked as the top five chemicals released statewide based on total CI. In contrast, based on total mass, methanol, nickel, ammonia, acetone, and toluene were identified as the top five TRI chemicals released in Oregon. TRI facility rankings were related to the demographics and household income of surrounding neighborhoods using bivariate GIS mapping and statistical analysis. TRI facilities were disproportionately located in racial and ethnic minority neighborhoods. They were also located in areas with lower incomes compared to those in the surrounding county. No relationship was observed between the hazard ranking of the TRI facilities overall and socioeconomic characteristics of the community in which they were located.

Current treatment of post-traumatic deformities. Residual orbital, adnexal, and soft-tissue abnormalities.

Evaluation and treatment of residual post-traumatic deformities of the periorbital region are approached best by systematically dividing the area into zones and assessing the deformities and needs of that particular region before addressing restoration of both function and cosmesis. These zones can be extended three dimensionally, and all abnormalities can be addressed appropriately. Bone malpositioning must be addressed first, and once repositioned, many soft tissue abnormalities may not require treatment. All periocular zones contain specialized structures that are interrelated. A fundamental understanding of the anatomy and physiology combined with the basic plastic surgical concept of recreation of the defect can lead to a successful approach to late deformities in this region.

Combination therapy for salvaging a failing, experimental skin flap.

The failing free flap remains a major problem for the reconstructive surgeon. Many and varied pharmacologic agents have been utilized to reverse the effects of ischemia in these flaps. Treatments have been aimed at inhibiting presumed causative factors in the no-reflow phenomenon. Therapy has generally been single in nature and designed to affect only one of these presumed factors. In this study, several pharmacologic agents were utilized individually or in combination therapy as postischemic washouts, in an effort to attack the multiple causative factors in the no-reflow phenomenon and to improve flap survival in a rat abdominal skin flap model. The treatment agents included lactated Ringer's, superoxide dismutase, and urokinase, with each used independently as a postischemic perfusion washout. Combination therapy utilized an initial postischemic perfusion with urokinase, followed by a second perfusion washout with superoxide dismutase. After 18 hr of primary ischemia, there was increased flap survival in the animals undergoing perfusion washout with either superoxide dismutase alone or with combined urokinase and superoxide dismutase washouts, compared to all other treatments (p < 0.001). It was found that flaps undergoing combined urokinase and superoxide dismutase postischemic perfusion washouts demonstrated significantly improved survival after 20 hr of primary ischemia, compared to all other therapies (p < 0.05). By demonstrating improved survival when a thrombolytic agent is used in conjunction with an oxygen free radical scavenger, these findings may have implications in the treatment of clinically failing free flaps.

Evaluation of a continuous systemic infusion of iloprost, a stable PGI-2 analog, on the survival of experimental skin flaps.

Numerous investigators have attempted to enhance the survival of ischemic experimental skin flaps using various pharmacologic manipulations. Recently, the authors' laboratory demonstrated the beneficial effect of iloprost, a stable PGI2 analogue, as a post-ischemic perfusion washout, in improving the survival of ischemic skin flaps. The rat unilateral abdominal skin flap, based on the superficial epigastric vessels, was utilized in this study involving 30 animals. The animals were divided into three different treatment groups, with ischemic periods of 16 and 18 hr. Perfusion washouts were performed at the completion of the various ischemic periods. Alzet osmotic pumps were used to deliver a continuous systemic infusion of iloprost for 7 days postoperatively. The groups consisted of the following: Group 1 (single ILO)--perfusion washout with iloprost only; Group 2 (continuous LD ILO)--low-dose systemic iloprost infusion (0.066 mcg/kg/min) and perfusion washout with iloprost; and Group 3 (continuous HD ILO)--high-dose systemic iloprost infusion (0.1 mcg/kg/min) and perfusion washout with iloprost. The percentage of flap survival was assessed on postoperative day 7. Skin flaps of the animals receiving the continuous systemic infusion of iloprost were noted to have varying percentages of survival, while skin flaps undergoing perfusion washout only were found to have either complete survival using a continuous systemic infusion of iloprost, compared to iloprost perfusion washout alone. In addition, the hypotensive side effects of systemic iloprost infusion limit its use in the rat skin-flap model.

A new approach to induced hypothermia.

A variety of methods have been employed for the induction of hypothermia; however, there are still some inherent problems that remain with current techniques. Liquid ventilation, a process used in several other environmental and clinical research areas, may be a feasible method since it takes advantage of the effectiveness of the pulmonary architecture as a heat exchanger. Hypothermia induced by liquid ventilation was studied in 8 newborn lambs, mean age = 10 +/- 8 SEM days. Each lamb was anesthetized with sodium pentobarbitol (20 mg/kg) and intubated. Cardiopulmonary measurements were taken during a control period prior to induced hypothermia. Liquid temperatures of 20 and 30 degrees C were used in cooling the animal while monitoring rectal and surface temperatures. Temperatures decreased producing rectal cooling rates of 8.4 and 4.8 degrees C/hr, respectively. Blood gas analysis showed adequate physiological gas exchange for all lambs during the liquid ventilation period. Based on the data, the process of liquid ventilation offers a unique potential both in experimental and clinical areas as a new approach to the technique of induced hypothermia.

Physiological effects of ventilation with liquid fluorocarbon at controlled temperatures.

Body cooling, respiratory heat loss, and the physiological effects of liquid ventilation at various temperatures were studied in 10 adult cats with applications to the deep sea diver. The animals were stabilized on mechanical gas ventilation with 100% oxygen during a control period and then mechanically ventilated for 1 h with liquid fluorocarbon. Fluorocarbon (Rimar 101) temperatures of 10 degrees C, 20 degrees C, and 30 degrees C were used to ventilate the animals while rectal and subcutaneous body temperatures were being measured. For the 3 temperature conditions, respective cooling rates of 9.0 degrees C/h, 7.8 degrees C/h, and 3.6 degrees C/h, as well as respiratory heat losses of 65,637 J X kg-1 X h-1, 33,488 J X kg-1, X h-1, 18,036 J X kg-1 X h-1 were observed while maintaining effective physiological gas exchange [mean PaO2 = 353 +/- 28 (SEM) mmHg, mean PaCO2 = 30 +/- 2 (SEM) mmHg]. Changes in cardiovascular variables were noted as mild (35 degrees C-30 degrees C) and moderate (30 degrees C-25 degrees C) levels of hypothermia were reached. Cardiac output, oxygen consumption, heart rate, and mean blood pressure were significantly correlated with rectal temperature. The data presented herein quantitate the effects of liquid ventilation on body cooling and respiratory heat loss. Furthermore, the physiological alterations associated with the observed hypothermic condition could severely limit the effectiveness of a human diver if not carefully controlled.