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Biomedical subjects

B M O'Brien

Publications and source records attributed to B M O'Brien.

At least 37 records · Page 2Linked to original sources
PubMed1990

The salvage of rabbit ischaemic epigastric free flaps using the vasodilator calcitonin gene-related peptide.

The rabbit epigastric free flap, subjected to 21 hours of warm (25 degrees C) ischaemia, was used as an experimental model to test the ability of two endothelium-dependent vasodilators, calcitonin gene-related peptide (CGRP) and carbamyl beta-methylcholine chloride (MCh, bethanechol chloride, the stable acetylcholine analogue) to improve flap viability. After the period of ischaemia, flaps were infused intra-arterially with either Hanks balanced salt solution (controls), CGRP or MCh for 30 minutes, and received additional intravenous boluses of these drugs at 2 and 32 minutes after revascularisation. The area of flap surviving improved significantly (p less than 0.025) from 39.9% (n = 18) for controls to 70.2% (n = 14) for CGRP treatment at 2 micrograms/kg, but was unchanged at 47.1% (n = 14) for MCh treatment at 50 micrograms/kg. Both CGRP and MCh significantly increased blood flow (p less than 0.05) resulting in 34% lower peripheral resistances compared with controls. These results suggest that CGRP has considerable clinical potential for the salvage of ischaemic flaps. CGRP must have several, as yet undefined, beneficial effects on the ischaemic tissue, since MCh invoked a vasodilatory response but failed to salvage ischaemic flaps.

Abdominal Muscles↗
PubMed1990

The redistribution of collagen in expanded pig skin.

Silicone tissue expanders were inserted subcutaneously in the buttocks of nine young pigs and gradually inflated to maximum capacity over 5 weeks. On the control side the expanders were left uninflated. Island buttock flaps were then raised, the expanders removed and the flaps spread into the same sites for 10 days. The tissue was harvested. Area measurements and full thickness skin biopsies were taken 10 days after flap inset in order to study the changes in collagen composition and isotypes in the skin layers. Ten days after inset of the flap the expanded skin had a mean 47% increase in surface area, was 9% thinner (from surface to implant), mostly due to thinning of the subcutaneous zone, but was not significantly different in water content, relative to the control skin. The expanded skin had a significant 9.3% increase (p less than 0.01, t test) in collagen content of the dermis. The relative proportions of Types I and III were not significantly changed by skin expansion in either the dermal/epidermal or subcutaneous/capsular zones. It is speculated that tensile factors during expansion stimulate the biosynthetic activity and/or mitotic activity of fibroblasts in the dermis to produce this gain in collagen in the expanded compared with unexpanded tissue.

Animals↗
PubMed1990

Lymph node transfer for the treatment of obstructive lymphoedema in the canine model.

The efficacy of transferring vascularised lymph nodes into lymphoedematous limbs was investigated. Stable below-knee lymphoedema was established in one hind limb of 10 dogs. The superficial inguinal lymph node and perinodal tissue from the normal hind limb was moved to the popliteal region of the lymphoedematous leg as a free vascularised transfer. In five dogs lymphaticolymphatic anastomoses between lymphatics of the node and proximal recipient site lymphatics were also performed. Circumferential measurements of the foot, ankle and midleg were obtained preoperatively and postoperatively at 3 and 6 months. These measurements showed postoperative reduction of the lymphoedematous legs compared to controls, with no added benefit from lymphaticolymphatic anastomoses. Technetium 99 scans and lymphangiography demonstrated re-establishment of lymphatic continuity in all recipient legs at 3 and 6 months post-transfer. Histological examination at 3 and 6 months revealed normal architecture in 9 of 10 nodes, although areas of lymphocyte depletion were common. Vascularised lymph node transfer to a lymphoedematous leg re-established lymphatic continuity and resulted in partial reduction of limb size. The addition of lymphaticolymphatic anastomosis to vascularized node transfer is neither necessary nor beneficial.

Anastomosis, Surgical↗
PubMed1990

Prefabrication of thin transferable axial-pattern skin flaps: an experimental study in rabbits.

The arteriovenous pedicle of all known axial-pattern skin flaps enters from the deep aspect and consequently the flap must contain fat and/or muscle and be of considerable thickness. In an attempt to fabricate a thinner axial-pattern flap the femoral artery and vein of rabbits were implanted, in various vascular configurations, directly into the subdermal layer of the skin. Implantation was found to provoke an extensive outgrowth of new vessels from the implanted artery and vein, and the progress and pattern of this neovascularisation was studied by carbon gelatine perfusion and histology. Neovascularisation begins within a few days of implantation and progresses rapidly. By 8 to 12 weeks it is possible to elevate regularly a viable, large skin flap based on the implanted pedicle.

Animals↗
PubMed1990

The anatomy of the subscapular artery and its effects on flap design in the rabbit.

The course of the subscapular artery was studied in 20 rabbits. Its course was constant, giving two branches to the latissimus dorsi muscle after which the vessel sent a branch (S1) that perforated the panniculus carnosus to supply a large territory of skin. In a separate experiment, the contribution of the S1 branch to the viability of the rabbit latissimus dorsi musculocutaneous flap was evaluated. From this experiment it can be concluded that, first, it is possible in a rabbit to elevate a large skin flap based solely on a muscle perforator (S1), which survives completely. Second, in the rabbit latissimus dorsi musculocutaneous flap, S1 is the major blood supply to the skin component. Damage to it severely diminishes skin flap survival, even if the vascular supply to the underlying muscle is completely intact.

Animals↗
PubMed1990

The role of microsurgery in modern surgery.

Microsurgery has a growing influence in all surgical specialties as well as in the field of reconstructive surgery. Current experimental work and clinical experience of microvascular surgery are reviewed.

Facial Paralysis↗
PubMed1990

Long-term results after microlymphaticovenous anastomoses for the treatment of obstructive lymphedema.

Over the last 14 years, 134 patients with obstructive lymphedema have been treated with microlymphaticovenous anastomoses. Ninety patients were available for long-term follow-up study. Of these, 52 patients were treated by microlymphatic surgery only and 38 of them also had segmental or radical reduction surgery, either at the same time or secondarily. Objective assessment was undertaken by volume and circumferential measurements. Initially, lymphangiography was used, but a study demonstrated increased edema immediately following the investigation in one-third of the patients and it was abandoned, both preoperatively and postoperatively. In the microlymphaticovenous anastomoses only group (N = 52), subjective improvement occurred in 38 patients (73 percent). Objectively, volume changes showed a significant improvement in 22 patients (42 percent), with an average reduction of 44 percent of the excess volume. In the microlymphaticovenous anastomoses and reduction surgery, usually segmental, group (N = 38), subjective improvement occurred in 30 patients (78 percent) and objective improvement occurred in 23 patients (60 percent), with an average reduction of 44 percent of the excess volume. Of those followed up, 67 patients (74 percent) have been able to discontinue the use of conservative measures, with an average follow-up of 4.0 years and average reduction in excess volume of 26 percent. There was a 58 percent reduction in the incidence of cellulitis following surgery. In those patients who were improved, drainage resulted in increased softness of the limbs. Edema of the hand diminished considerably in most patients, although this was difficult to measure. These long-term results indicate that microlymphaticovenous anastomoses have a valuable place in the treatment of obstructive lymphedema and should be the treatment of choice in these patients. Reduction surgery can be used as an adjunct in some of these patients, especially in the posteromedial aspect of the upper arm. Liposuction has been used in failed cases or in patients in whom no lymphatics could be found. Improved results can be expected with earlier operations because patients referred earlier usually have less lymphatic disruption.

Anastomosis, Surgical↗
PubMed1990

Treatment of vaginal agenesis with a new vulvovaginoplasty.

The correction of vaginal agenesis requires the creation of a canal that is in the correct axis and ideally of adequate size, texture, and secretion. A simple surgical technique is described which has a good anatomic and functional result with minimal morbidity. It combines the traditional dissection of the rectovesical space described by McIndoe with a significantly modified vulvovaginoplasty based on the Williams method. The technique has been performed with good results and no complications in three patients. Closely monitored vaginal dilatation is essential in the postoperative period. At this stage, only one patient has engaged in intercourse.

Adolescent↗
PubMed1990

The effect of thromboxane synthetase inhibition on tolerance of skin flaps to secondary ischemia caused by venous obstruction.

The harmful effects of the no-reflow phenomenon on skin flaps were modified by using the thromboxane synthetase inhibitor UK-38,485. Sprague-Dawley rats (N = 134) were subjected to either 3 or 5 hours of secondary venous occlusion occurring 24 hours after a primary ischemic episode of 1 1/2 hours. Within each time period, rats received either saline or UK-38,485 at the primary ischemic episode and/or at the secondary ischemic episode. Flaps treated with UK-38,485 in relation to the period of secondary ischemia had a higher survival rate than control ischemic flaps (p less than 0.01). Those treated only at the end of the primary ischemic episode but prior to the secondary ischemic episode had improved survival rates, but these were not statistically significant. These effects may be explained by the lower thromboxane:prostacyclin ratios at the time of revascularization. The possible interrelationship of the prostanoids with free-radical mechanisms in the no-reflow phenomenon is also discussed.

Animals↗
PubMed1990

Effect of a thromboxane synthetase inhibitor UK-38,485 on the tolerance of skin flaps of primary ischaemia.

The harmful effects of ischaemia or skin flaps were modified using the thromboxane synthetase inhibitor UK-38,485. The epigastric island flaps of Sprague-Dawley rats (n = 288) were subjected to 10, 12 or 14 h of total pedicle occlusion, or 3, 5 or 7 h of venous occlusion of the sole vascular pedicle. Within each time period, rats received intravenous doses of either physiological saline (controls) or UK-38,485 at the beginning or end of the ischaemic episode. Flaps treated with UK-38,485 overall had a higher survival rate than control ischaemic flaps (P less than 0.001). This applied both to total (arterial) ischaemia (P less than 0.001) and partial (venous) ischaemia (P less than 0.01). There was no significant difference between treatment given at the beginning or at the end of the ischaemic episode. These results may be explained by reduced platelet aggregation and thrombosis in the microvasculature due to the lower thromboxane/prostacyclin ratios for treated flaps. The possible inter-relationship of the prostanoids with free radical mechanisms in the no-reflow phenomenon is also discussed.

Animals↗
PubMed1990

Effect of postoperative radiation on the incorporation of tibial bone grafts in the rabbit.

A dose of 48 Gy of X-irradiation given over two to five weeks after grafting caused no significant delay in the rate of healing and only a small and statistically non-significant decrease in the torsional strength of the graft-bone junction of either vascularised or non-vascularised bone grafts of the tibiae of rabbits. Healing was faster and the union between the graft and adjacent bone developed torsional strength significantly more rapidly with vascularised than with non-vascularised grafts. These findings suggest that postoperative radiotherapy is unlikely to have a significantly deleterious effect on the healing of bone grafts used to repair defects produced by excision of malignant bone tumours.

Animals↗
PubMed1990

Microvascular submandibular gland transfer for the management of xerophthalmia; an experimental study.

Free submandibular salivary gland transfer was investigated as a method of treatment for xerophthalmia. Xerophthalmia was created in rabbits by surgical removal of the lacrimal gland and the incidence of corneal ulceration was seen to correlate with the decrease in tear secretion. Microvascular transfer of the submandibular salivary gland to drain saliva into the conjunctival fornix prevented the development of corneal ulceration in 63% of the cases.

Amylases↗
PubMed1990

Secondary ischemia time in rodents: contrasting complete pedicle interruption with venous obstruction.

The current study investigated the effect of secondary ischemic insults on ultimate flap survival. Rodent skin flaps subjected to 8 hours of secondary ischemia with total pedicle obstruction had 56 percent survival (7 of 12) compared with primary ischemic flaps of the same time, which all survived. At 10 hours of ischemia, only 42 percent of secondary ischemic flaps survived compared with 67 percent (8 of 12) of primary ischemic flaps. When the secondary ischemia was caused by venous obstruction, the results were even more striking. Ninety-two percent (11 of 12) of primary venous obstruction flaps survived 3 hours of ischemia and 75 percent (9 of 12) survived 5 hours of ischemia, while only 56 percent (7 of 12) and 8 percent (1 of 12) of flaps subjected to secondary venous obstruction survived at the same times, respectively. The explanation of these observations on the basis of tissue pathophysiologic changes will require further study. The results support the need for close monitoring of clinical flaps to ensure optimal survival.

Animals↗
PubMed1990

Results of management of facial palsy with microvascular free-muscle transfer.

This paper reports our experience in facial reanimation using free innervated muscle transfer in 69 patients with long-term facial palsy. The majority of patients were treated in two stages with cross-facial nerve graft as the first stage and microvascular muscle transfer at the second stage. The gracilis muscle was used in 62 patients. A system of grading results has been utilized in the long-term evaluation. The overall final result was excellent or good in 51 percent of 47 patients who were available for follow-up. Although the results are not completely satisfactory, they justify the use of this approach to a difficult clinical problem. The results are improving as technical modifications to the procedure have evolved. The gracilis muscle is a reliable free transfer with internal anatomy conductive to use for reanimation of the paralyzed face. This type of transfer, in our experience, has proved superior to nonmicrosurgical methods for treatment of complete and severe incomplete facial palsy. The seventh cranial nerve is used in the innervation of the transferred muscle, the ipsilateral being preferable if available. The authors believe that use of the same cranial nerve is superior to methods that involve other cranial nerves, where spontaneity is often not achieved.

Adult↗
PubMed1987

Protein metabolism and fibrosis in experimental canine obstructive lymphedema.

Obstructive lymphedema is a pathologic condition resulting in the accumulation and stagnation of serum proteins in the lymphatics and interstitial spaces. In a canine model of obstructive lymphedema, one limb was rendered lymphedematous, and various biochemical parameters were determined in this and an unaffected control limb. Both lymph and interstitial fluid had significantly decreased acid proteinase activity (comprising mostly cathepsin D-like enzymes) and neutral proteinase activity (comprising metallo, sulfhydryl, and serine proteinases, and collagenase). Possible reasons for these decreases could be: (1) saturation of macrophages and their surrounding environment with whole or partially digested proteins, or (2) elevation in the levels of circulating inhibitors like alpha 2-macroglobulin. The lymphedematous skin was significantly thicker than control skin and had elevated levels of collagen. However, unlike some fibrotic conditions, the relative proportions of types I, III, and V collagen, as determined by pepsin solubilization and neutral salt fractionation of the collagen fibrils, were similar to those found in normal skin. It is speculated that a decrease in the breakdown of collagen by collagenase and a continuing synthesis of collagen by fibroblasts led to an imbalance in favor of collagen deposition in the skin.

Animals↗