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Biomedical subjects

R F Morgan

Publications and source records attributed to R F Morgan.

At least 19 recordsLinked to original sources
PubMed1992

Further investigation of secondary venous obstruction.

The first ischemic insult a tissue suffers is primary (1 degree). A second ischemic episode, such as thrombosis after free tissue transfer may be regarded as secondary (2 degrees) ischemia. The current study investigated 2 degrees ischemia in rodent epigastric flaps. Flaps were elevated in 50 Sprague-Dawley rats: group 1 had 5 hours 1 degree venous ischemia induced by placement of microvascular clamps; group 2 was like group 1, except venous continuity was re-established by venous anastomosis after resection of the venous segment previously microclamped; group 3 had 15 minutes of 1 degree ischemia, 24 hr later 5 hr of 2 degrees venous ischemia was induced by placement of microvascular clamps; group 4 was like group 3, except the venous segment was excised. Necrosis was evaluated on postoperative day 7. Both secondary ischemic groups had significantly less flap survival than the corresponding primary ischemic groups (P less than 0.001 for both). Resection of a portion of the vein and subsequent microanastomosis did not reduce flap survival (NS). Secondary venous ischemia of 5-hr duration is poorly tolerated by rodent skin flaps. There was no difference in flap survival in those flaps whose veins were clamped for 5 hr compared to those flaps whose clamped venous segments were resected and re-anastomosed.

Anastomosis, Surgical↗
PubMed1992

The beneficial effect of dextran on anastomotic patency and flap survival in a strongly thrombogenic model.

Dextran lowers the probability of thrombus formation, by reducing platelet aggregation and adhesion and by increasing fibrinolysis. All studies to date using dextran for microvascular reconstruction have examined only short-term (1 to 2 hr) patency in isolated vessels. The current study used an established thrombotic model (inverted sleeve interposition graft), to investigate the effect of dextran on the long-term survival of pedicle flaps. A6- x 3-cm epigastric flap was elevated. A 2-mm inverted sleeve interposition graft was placed on the artery side of the pedicle by microvascular techniques. One group received dextran (17 cc/kg) 2 hr preoperatively and every 6 hr postoperatively for the next 72 hr. A control group received saline on the same schedule. Survival was assessed on postoperative day 7, at which time necrosis was obvious. Several parameters (clotting studies and electron microscopy) were studied to characterize the phenomenon more clearly. Only 25 percent of saline-treated flaps survived (2/8), while all dextran-treated flaps survived (7/7) (p less than 0.02, Fisher exact test). Thus, dextran allowed flaps to survive by preventing thrombus formation, despite a strong thrombogenic focus.

Animals↗
PubMed1992

Deleterious effect of urokinase used to treat experimental intra-arterial thiopental injection injuries.

UNLABELLED: Inadvertent arterial drug injections continue to be an important source of morbidity. Although the clinical picture of thiopental injection has been well defined over the past 50 years, there is still much controversy concerning pathophysiology and treatment regimen. Recently, a case report showed the efficacy of urokinase in treating this problem. The current study used the reliable ear model to study more closely this phenomenon. Rabbits were divided into four groups. Ears in Group 1 rabbits (n = 10) received an intra-arterial thiopental (15 mg/kg) injection. Group 2 rabbits (n = 10) received thiopental followed by a 1-ml saline injection 15 minutes later. Group 3 rabbits (n = 10) received thiopental followed by 50,000 U of urokinase. Finally, Group 4 rabbits (n = 4) received an intra-arterial injection of saline alone. Necrosis was evaluated 2 weeks later and expressed as a percentage. Student's t tests were used to evaluate data significance. RESULTS: Group 1 (thiopental alone) and Group 2 (thiopental and saline) rabbits had significantly more necrosis than Group 4 (saline alone) rabbits, 21.2% and 17.5% versus 0% (p less than 0.001 for both). Group 3 (thiopental and urokinase) rabbits had significantly more necrosis (46.5%) than Groups 1 and 2 rabbits (p less than 0.001 for both). CONCLUSION: From this study, we found that treatment of intra-arterial thiopental injection injuries with urokinase was of no benefit, but more importantly, it increased tissue necrosis by approximately 100%. Clinical use of this treatment is to be discouraged until underlying mechanisms are better defined.

Animals↗
PubMed1992

Shave excision and dermabrasion for facial angiofibroma in tuberous sclerosis.

Tuberous sclerosis is an inheritable disease of varied manifestations. Hallmarks of the disease have historically been identified as infantile seizures, severe mental retardation, and facial growths. The facial lesions were formerly termed adenoma sebaceum, but are now known to be angiofibroma. We present a patient who was referred for management of large facial lesions complicated by intermittent hemorrhage. A combination of shave excision and dermabrasion led to a symptomatic and cosmetic improvement.

Adult↗
PubMed1992

Digital sympathectomy for refractory Raynaud's phenomenon in an adolescent.

We describe the case of an adolescent with severe Raynaud's phenomenon refractory to conventional medical management. Her course was complicated by fingertip ulceration and necrosis. The localized surgical technique of digital sympathectomy was successfully used in the management of her disease, and should be considered for intractable Raynaud's phenomenon.

Adolescent↗
PubMed1991

Lidocaine diffusion in five tissue expanders: an in vitro and in vivo study.

Previous work in our laboratory has demonstrated that tissue expanders are permeable to lidocaine. In this two-part study, we assessed the in vitro lidocaine diffusion in the following five common tissue expanders: Dow Corning, McGhan, Cox-Uphoff, Hyer-Schulte (Mentor), and Surgitek. In part 1, we demonstrated that wall thickness appeared to be the major determinant for diffusion. Part 2 reports an in vivo study of lidocaine diffusion from tissue expanders used for breast reconstruction. We initially determined that there is incomplete mixing between the valve and connecting tubing and the contents of the expanders, over the period of 1 week. We subsequently examined the lidocaine diffusion from seven tissue expanders placed in a submuscular position for breast reconstruction. The rate of lidocaine diffusion was highly variable, but on average was about 3% per day.

Diffusion↗
PubMed1991

Steroid and benzyl alcohol diffusion through tissue expanders and double lumen breast implants.

The rate of diffusion of benzyl alcohol (the bacteriostatic agent in the provided diluent) and methylprednisolone 21-hemisuccinate and related rearrangement and hydrolysis products ("steroid") through tissue expanders was examined. The rate of diffusion of steroid through double lumen breast implants was also studied. It was found that benzyl alcohol rapidly diffused through tissue expanders into a saline bath. By 24 hours, one-half of the benzyl alcohol had diffused through the expander. The steroid was much slower to diffuse out of the expander. By 141 days, only 2% of the steroid was found in the bath. This rate was comparable for both the tissue expander and double lumen implants. In addition, a significant amount of the steroid is located in the expander wall, associated with the surface of the expander or precipitated out of solution or both. The clinical significance of these findings is discussed.

Benzyl Alcohol↗
PubMed1991

A new compound-curved needle for microvascular surgery.

A new compound-curved needle has been designed and developed for microvascular surgery from a unique stainless steel alloy, American Society for Testing Materials 45500. This needle has two distinct radii of curvature and a short tapered point, followed by a curved distal section. Despite its geometry, it exhibits similar resistance to bending and breakage as a curved needle with a single radius of curvature manufactured from the same alloy. The design of this new needle enables plastic surgeons to pass it through vessel walls with greater accuracy to a controlled depth and length of bite than a curved needle with a single radius of curvature.

Humans↗
PubMed1991

Biochemical performance of tapercut cardiovascular needles.

Standardized reproducible tests have been developed to determine the biomechanical performance of cardiovascular needles. The parameters used to assess performance were: 1) sharpness, 2) resistance to bending, and 3) ductility. Four comparable groups of tapercut and taper point cardiovascular needles were selected from different manufacturers for these biochemical studies. The results of this testing demonstrated that needle geometry, needle composition, and the manufacturer were important determinants of needle performance. When comparable needles were evaluated, the biochemical performance of cardiovascular needles manufactured by Ethicon, Inc. (Somerville, NJ) were superior to needles produced by other manufacturers. The superior performance characteristics of the cardiovascular needles produced by Ethicon, Inc. were related to their unique stainless steel alloy, American Society for Testing Materials 45500, which has greater yield and tensile strengths than the alloy used by the other manufacturers. This stainless steel alloy was ideal for the production of tapercut needles, which combined some of the features of a reverse cutting edge needle and taper point needle. Its very short cutting edges allowed it to penetrate the membrane at considerably lower penetration forces than were encountered with comparable taper point needles. In addition, the investigation indicated that the trocar point cardiovascular needles produced a large triangular defect whose diameter was much larger than that of the needle body. For this reason, the use of the trochar point needle is not recommended in cardiovascular surgery.

Biomechanical Phenomena↗
PubMed1990

Seroma prevention using fibrin glue in a rat mastectomy model.

Seromas are a frequent complication of mastectomy (17% to 53%) in humans and are correlated to skin flap elevation, lymphovascular interruption, and drainage into surgically created potential spaces. The use of intraoperative topical fibrin glue to reduce morbidity in rats undergoing radical mastectomies has been evaluated. A model consistently producing seromas was developed by radical mastectomy and lymphadenectomy in the Sprague-Dawley rat. A fibrin glue application procedure was tested using this model. The double-blinded protocol called for spray application of saline or fibrin glue to mastectomy wounds followed by sequential inspection and necropsy on postoperative days 5, 8, 11, and 14. Topical fibrin glue was shown to be statistically significant in decreasing the presentation of seromas following a radical mastectomy in the Sprague-Dawley rat.

Animals↗
PubMed1990

Single-donor fibrin glue for hand burns.

Early tangential excision sometimes results in considerable blood loss, prolonged operative time, and partial loss of the graft secondary to hematoma formation. Previous reports document positive hemostatic effects and improved skin fixation with fibrin "glue." The commercial preparation used in Europe, however, has not been approved by the United States Food and Drug Administration because of the high risk of hepatitis and human immunodeficiency virus transmission. Using a method developed at the University of Virginia, we applied single-donor fibrin glue as an adjunct in early excision and grafting in 16 patients (26 hands). The overall graft take was 99%. In all patients, better adherence of the split-thickness graft to the recipient bed, during and immediately after application, was noted. We have observed no negative effects with regard to infection or healing. We recommend the use of single-donor fibrin glue to reduce operative blood loss, improve survival and ease of graft application, and possibly to accelerate healing.

Adult↗
PubMed1990

The dorsal rat flap: a discussion of the model and the salutary effect of cimetidine on flap survival.

Failure of skin flaps remains a significant clinical problem. The dorsal rat flap, a reliable experimental model, was used to test the efficacy of cimetidine in treating a failing flap. Flaps were elevated in 45 rats divided into three equal groups. Group 1 was a saline control group, Group 2 received cimetidine 250 mg/kg three times a day for 7 days postoperatively, and Group 3 received cimetidine for 1 day before surgery, and then as in Group 2. Necrosis was assessed on the seventh postoperative day. Group 2 had 31.1 +/- 1.3 (mean % +/- SEM) necrosis, significantly better than saline control animals (p less than 0.01) and pretreated animals (p less than 0.05). These results suggest the usefulness of cimetidine in ischemic flap surgery.

Animals↗
PubMed1990

Biomechanical performance of cardiovascular needles.

Standardized reproducible tests have been developed to determine the biomechanical performance of cardiovascular needles. The parameters used to assess performance were sharpness, resistance to bending, and ductility. Three comparable groups of taper point cardiovascular needles were selected from different manufacturers for these biomechanical studies. The results of this testing demonstrated that needle geometry, needle composition, and the manufacturer were important determinants of needle performance. When needles of comparable size were evaluated, the biomechanical performance of cardiovascular needles manufactured by Ethicon, Inc., were superior to needles produced by other manufacturers. The superior performance characteristics of the cardiovascular needles produced by Ethicon, Inc., were related to their unique stainless steel alloy, American Society for Testing Materials 45500, which has greater yield and tensile strengths than the alloy used by the other manufacturers. Scanning electron microscopic photographs of the Ethicon, Inc., needle revealed a uniform taper point geometry without irregularities. The deformations of the points of cardiovascular needles produced by the other manufacturers could alter their performance.

Biomechanical Phenomena↗
PubMed1989

Gastrotracheal fistula: a late complication after transhiatal esophagectomy.

A 51-year-old woman underwent a transhiatal esophagectomy for a failed antireflux procedure. She did well for 15 months, when she developed evidence of hemoptysis followed by tracheogastric fistula. She underwent operative repair with the use of a pericardial patch to replace the membranous trachea and interposition of a latissimus dorsi flap to isolate the stomach from the tracheal suture line. She has done well after this operation.

Esophagus↗
PubMed1989

Cold injuries.

Until recently, military personnel have had the greatest risk for cold injuries. During the past two decades, however, destitute persons without adequate clothing or shelter, and sports enthusiasts participating in snowmobiling, mountain climbing, and skiing have been responsible for the increased incidence of cold exposure seen in a large civilian population. Consequently, cold injury remains a crippling problem. Although research is opening new avenues of accurate diagnosis and expeditious treatment, the standard against which these methods must be measured continues to be a rational treatment plan that often prevents the sequelae of cold injuries.

Body Temperature Regulation↗
PubMed1989

Lidocaine permeability in silicone tissue expanders: an in vitro analysis.

Tissue expansion has achieved a prominent role in soft-tissue reconstruction. Expansion-induced pain is often a limiting factor in this process and can affect patients for as long as 24 to 48 hours following each expansion session. Although lidocaine is known to be an effective analgesic, only anecdotal reports of its usefulness when placed within a tissue expander currently exist. This two-part study was designed first to determine if in fact silicone is readily permeable to lidocaine, and second to determine if the potential diffusion dynamics can be defined. In part 1 of the study, the silicone polymer was indeed found to be readily permeable to lidocaine as measured with fluorescence immunoassay technique. In part 2, two groups of Surgitek and Dow Corning expanders were filled with saline and lidocaine and placed in saline baths. At several intervals over a 48-hour period, aliquots of the surrounding saline were sampled and the lidocaine levels subsequently determined. A rather predictable and consistent diffusion curve was demonstrated. The significant difference in diffusion characteristics between the two expander types was apparently due to wall thickness differences inherent in the manufacturing. In this in vitro study, filler-valve leakage did not significantly contribute to lidocaine migration from within these tissue expanders. This basic in vitro work will now set the stage for further in vivo and clinical investigations to more precisely define the role of lidocaine in the tissue-expansion process.

Lidocaine↗
PubMed1989

Nerve compression syndromes of the lower extremity.

Nerve compression syndromes of the lower extremity present a challenge in differential diagnosis. Compression of the common peroneal nerve occurs relatively frequently; compression of the sciatic nerve occurs infrequently. The pattern of weakness helps distinguish lumbar root entrapment from peripheral compression syndromes. Compression syndromes must also be differentiated from diabetic, alcoholic or vasculitic neuropathy. Recovery correlates with the degree and duration of nerve injury. Thus, early diagnosis and treatment are important.

Diagnosis, Differential↗