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Biomedical subjects

W A Morrison

Publications and source records attributed to W A Morrison.

At least 91 records · Page 5Linked to original sources
PubMed1994

Drug mixture which improves survival of ischemic rabbit epigastric skin flaps.

The chief aim of this study was to maximize flap survival by counteracting the pathophysiological changes occurring during ischemia-reperfusion. Rabbit epigastric skin flaps given 21 hours of ischemia were infused intra-arterially with selected drugs at the start of reperfusion. Compared with control infused ischemic flaps, which had a 33% survival rate on day 7 post-ischemia, significant improvement was found with vasodilators nitrendipine (61%) and prostacyclin (65%) and the thrombolytic agent urokinase (65%); marginal improvement with the free radical scavenger desferrioxamine (53%); but no change with streptokinase (44%), heparin (21%), and ATP-MgCl2 (35%). A drug mixture comprising all of these agents except streptokinase and urokinase produced 87% survival, suggesting an additive effect. Biochemical assays on skin homogenates and blood implicated oxygen free radicals, neutrophil infiltration, and thromboxane in flap failure. These results imply that multiple factors are responsible for ischemic flap failure and that a mixture of drugs needs to be infused to counteract all of the detrimental changes.

Adenosine Triphosphate↗
PubMed1994

Nitric oxide synthase inhibitors improve skin flap survival in the rat.

The ability of nitric oxide (NO) synthase inhibitors to reduce ischemia-induced skin flap necrosis was assessed using a modified McFarlane flap in the rat. Flap survival was significantly improved in L-NIO treated (86 +/- 2%), L-NAME-treated (84 +/- 2%), and aminoguanidine-treated (76 +/- 2%) animals compared to the saline-treated group (54 +/- 2%), P < 0.005. Inhibition of NO synthase significantly decreased the hyperemia and edema within the flaps at 24 hours post-elevation. These findings suggest that endogenous NO production contributes to ischemic necrosis and that inhibition of NO synthase may prove useful in extending survival of tissues subjected to ischemia.

Amino Acid Oxidoreductases↗
PubMed1994

Cold stored femoral vessels as microvascular allografts: a preliminary study.

Cold stored femoral arteries or veins have been reinserted successfully as autografts into rabbits. The present study examines whether grafting with cold stored vascular allografts is equally successful. Rabbit femoral arteries and veins were stored at 4 degrees C for 4 weeks before insertion as allografts into unrelated animals. Three weeks after insertion into the femoral artery all venous allografts and 80% of arterial allografts were patent, but patency of both graft types declined over the next few weeks. A small number of cold stored venous allografts when inserted into the femoral vein occluded within 3 weeks. No histological evidence of rejection was apparent. The findings suggest that cold stored vascular allografts could be used successfully as an arterial "prosthesis" to support free flaps where relatively short term patency is required until the flap can establish sufficient peripheral inset to survive in its own right. This technique could be applied when autologous veins are not available or not justified.

Animals↗
PubMed1994

Use of free interpositional vein grafts as pedicles for prefabrication of skin flaps.

Pedicles created from a long vein graft increase the scope and applications of prefabricated skin flaps. This study reports the survival and pattern of neovascularization of lower abdominal skin flaps in rabbits based on a pedicle formed by interposition of a long vein graft between the divided ipsilateral femoral artery and vein. Flaps were elevated 2-5 weeks after pedicle implantation and the surviving area quantitated and vascular patterns examined 1 week later. Only 8 out of 35 flaps were greater than 50% alive, the most frequent cause of flap failure being pedicle non-patency. If the pedicle remained patent, complete flap survival was possible as early as 2 weeks after implantation. In non-patent pedicles, recanalization or formation of a new vascular network may, given at least 4 weeks, be sufficient to ensure partial flap survival. The findings indicate that implantation of a long, skeletonized vein graft is an unreliable method of prefabrication of abdominal skin flaps in this model.

Animals↗
PubMed1994

Immediate and short-term effect on arterial flow of clamping or stripping one vessel of a two vessel limb in a dog model.

The effect on distal blood flow in a 2 vessel limb of clamping one of the vessels or resecting it over a length is not known. Commonly this situation occurs clinically, for example, following lacerations to the radial or ulnar artery or as a result of removing a radial or ulnar artery flap. In a dog model established to mimic these clinical circumstances, a 2 vessel limb was created in which one vessel carried two-thirds of the total flow and the other one-third. Electromagnetic flow recordings were taken to measure the changes in flow in one vessel when the other was clamped or resected. Contrary to expectation, when one vessel was occluded the flow in the opposite vessel both immediately and for the following 30 minutes increased but remained well below the combined flow of 2 unclamped vessels. No increased flow was recorded in the dominant vessel when the smaller vessel was clamped, while an approximately 25% increase in flow was recorded in the smaller vessel when the larger one was clamped. This represents a reduction in total distal blood flow of one-half of the preclamping levels. Clamping of the vessel or its resection over a length resulted in the same degree of alteration in flow in the opposite vessel. The sacrifice of a dominant vessel in a 2 vessel limb whether by simple ligation or by radical stripping as for free tissue transfer significantly decreases distal flow in that limb at least in the immediate and short term.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Heterotopic vascularized growth plate transfer in juvenile dogs.

Prior animal studies of vascularized epiphyseal transfers placed growth plates in 2 bone systems where the independent growth of epiphyses and their response to altered stresses has been difficult to assess. This study assessed growth of vascularized ulnar epiphyses transferred to the ipsilateral humerus of 12-week-old puppies. Growth was permitted by a specially designed extensible plate. Control groups showed that humeral dissection, osteotomy and ostectomy alone do not stimulate growth. In 4 puppies initial growth of the transferred epiphysis was seen but late collapse and formation of bridging callus occurred so that overall humeral length at maturity was not significantly different from control humeri. Physical forces inherent in heterotopic transfer may preclude long term growth of transferred epiphyses particularly in sites of higher relative load. The extensible plate used here may be a useful device in the fixation of transferred epiphyses with growth potential.

Animals↗
PubMed1994

Flushing the vessel ends: the effect on ischemic free flap survival.

During vascular anastomosis of experimental ischemic free flaps it is common to observe that stagnant blood in the vessel ends has clotted. A study was performed to investigate if flushing away the stagnant blood on division of the vessels would increase flap survival. Flushing did not influence flap survival. Clinically, clot is rarely seen, except in conditions of prolonged ischemia or damaged vessels. Current surgical practice does not involve flushing the vessel ends upon division of the vessels and this approach is affirmed by our results.

Anastomosis, Surgical↗
PubMed1994

In vivo microscopy of a rat abdominal skin flap: a new model.

This study describes a rat abdominal skin flap model of in vivo microscopy which provides a reliable, easy to perform system in which to examine the microcirculation of flaps. The island flap, which is based on the superficial inferior epigastric vessels caudally, and drained proximally by the lateral thoracic vein, can be mounted directly on a Perspex microscope stage. In vivo microscopy of the subdermal plexus of the flap allows detailed study of blood flow pattern, capillary flow, microvessel diameter, and margination of leucocytes, in a skin flap with versatile blood supply and innervation.

Abdomen↗
PubMed1994

Training model for microvessel anastomosis.

In the early stages of microsurgical training a model is required which is accessible, inexpensive, and approximates human tissue. In this research centre initial training exercises utilize cold stored vessels harvested from sacrificed animals used in other experiments. This model serves as an initial training tool prior to the progression to live animal research which maximizes use of animal specimens and approximates the in vivo qualities of blood vessels. The costs involved are minimal and a large number of vessels can be efficiently harvested and stored using basic equipment. As a training model, cold stored vessels have balanced cost with practicality, given an excellent approximation to living tissue and have markedly reduced our usage of live animals for teaching. This latter effect is significant at a time of increased scrutiny of the ethical use of laboratory animals.

Anastomosis, Surgical↗
PubMed1994

A histological and carbon perfusion study of cephalic and saphenous venous flaps in the dog.

A histological and carbon-infusion study of cephalic and saphenous venous flaps in the dog shows that cephalic flaps survive significantly better than saphenous flaps, their mean viability at 5-14 days being 50-60% compared to 23.8% for saphenous flaps. Venous drainage is essential for flap survival but perfusion of the cephalic vein with arterial blood does not alter flap viability. The findings indicate that cephalic flaps survive better because they are thinner and contain a more extensive venous plexus. A cephalic flap is a suitable model for in vivo study of the circulation within a venous flap.

Animals↗
PubMed1994

Effects of cold storage on the subsequent structure and function of microvenous autografts.

A study was undertaken to evaluate the structure and patency of cold stored rabbit femoral veins following reinsertion as autografts for 3 weeks. The periods of cold ischaemic storage were 1, 2, 3 and 4 weeks (n = 10/gp) and 6 and 10 weeks (n = 6/gp). All rabbits were subject to 3 operations under general anaesthesia. In the first, a 4 cm segment of left femoral vein was harvested and stored at 4 degrees C for the specified ischaemic interval. Following storage the graft was microsurgically reinserted at a second operation into the right femoral artery of the donor rabbit. Three weeks later, graft patency was assessed by surgical exploration and the graft processed for light and electron microscopy. Patency rates remained over 80% after 3 weeks in all groups except the 10 week storage group where only 1 of 6 (17%) grafts was patent at 3 weeks. In all groups normal vein structure was absent, being replaced by thin walled necrotic areas or by neointimal ingrowth. The excellent patency rates achieved indicate it is possible to cold preserve extra lengths of vein grafts harvested at initial operation for reuse should regrafting be necessary.

Animals↗
PubMed1993

The functional and structural effects of hypothermic storage on ischaemic arterial grafts.

The effects of hypothermic ischaemia on blood vessels are unknown. This study aimed to determine the 3 week patency rate and the pathology of 9 experimental groups of hypothermically stored ischaemic arteries and one control group in a rabbit femoral artery model. Ischaemia times were 0 h, 24 h, 1, 2, 4, 6, 8 and 10 weeks (Groups 1-8). Patency was over 80% in all groups after 3 weeks reinsertion. Following reinsertion control grafts maintained normal arterial structure, but cellular degeneration had occurred in all ischaemic grafts and appeared complete after 4 weeks ischaemia. The graft connective tissue framework frequently remained intact. Repair was evident in central graft regions after 2 weeks ischaemia and 3 weeks reinsertion, but occurred only adjacent to the anastomosis in 4-10 week ischaemic arteries. Four week ischaemic arteries (Groups 9 and 10) reinserted for 6 and 12 weeks respectively exhibited near complete repair but patency dropped to 60% in the 12 week group.

Animals↗
PubMed1993

Revascularization of an ischemic replanted thumb using a lateral arm free fascial flap.

Digital ischemia and cold sensitivity after replantation are common. Occasionally they are severe enough to warrant intervention, including amputation of an otherwise functional digit. We present a patient with pregangrenous ischemia in a replanted thumb 10 years after multiple digit replantation. Angiography revealed vascular occlusion in the distal radial artery with no patent vessel in the thumb. The option of transposition of a spare neurovascular bundle from the adjacent radial digits was limited by their single-vessel supply resulting from previous replantation. We describe a method of revascularization by introduction of an arteriovenous pedicle, using a free fascial flap harvested from the lateral arm and based on terminal ramifications of the profunda brachii vessels. The flap was buried between the pulp and flexor tendon sheath and anastomosed to the radial artery and a wrist vein. This resulted in successful revascularization of the digit, clinically and radiologically, and 20 months later, the patient remains symptom free.

Adult↗
PubMed1993

Infusions of a novel calcitonin gene-related peptide (CGRP) derivative at the time of reperfusion to salvage ischaemic rabbit skin flaps.

Rabbit epigastric skin flaps were subjected to 21 h of ischaemia at 25 degrees C. In the first 40 min of reperfusion the flaps were infused intraarterially with either Hanks' balanced salt solution (controls), chicken CGRP or a derivative DADA-CGRP. Skin biopsies and blood specimens were taken immediately before and after 1-h reperfusion. The aim was to observe the effect of CGRP derivatives on compromised skin-flap survival and to help elucidate the critical biochemical mechanisms. It was found that chicken CGRP and DADA-CGRP produced a dose-dependent increase in blood flow, significant at and above 0.1 microgram/kg, but only the 0.1 microgram/kg DADA-CGRP infusion produced a statistically significant increase in flap survival (75.1%) as compared with controls (41.6%). CGRP infusions caused significantly more rapid restoration of tissue ATP levels and resulted in a smaller rise in blood thromboxane as compared with controls. However, CGRP caused no significant change in the tissue levels of myeloperoxidase, a measure of neutrophil infiltration, and lipid peroxidation, an indicator of free-radical activity. It is concluded that intraarterial CGRP infusions to ischaemic flaps at the time of reperfusion are indicated. However, an ideal infusion solution would also need to counteract free radicals and neutrophils which are believed to also play a major role in the inflammatory response leading to flap failure.

Animals↗
PubMed1992

Biochemical analysis of the venous flap in the dog.

There has been great interest stimulated by reports on factors influencing the survival of skin flaps which possess only venous inflow and outflow, i.e., venous flaps. The present study serially (Days 1, 2, and 4 postoperatively) observed several biochemical factors which might affect flap survival. ATP levels were measured to assess endogenous energy stores, malonyldialdehyde (MDA) and xanthine oxidase (XO) to estimate free radical production, superoxide dismutase (SOD) to quantify antioxidant defenses, and edema to measure inflammatory changes. Eighteen thighs on nine dogs were assigned randomly to one of three groups: full-thickness skin grafts, flaps based solely on the saphenous artery and vein (AV flaps), or flaps based solely on the saphenous vein (venous flaps). These were regarded as being mostly ischemic, totally perfused, and partially ischemic, respectively. Control skin biopsies were obtained adjacent to surgical sites. AV flaps and control skin were similar in all respects. Venous flaps compared with skin grafts were significantly less edematous (P less than 0.01) had less MDA and XO (P less than 0.05), but no significant differences in SOD and ATP levels. However venous flaps had significantly less ATP than AV flaps (P less than 0.01). Thus venous flaps survive despite depletion of ATP levels. These results suggest that decreased free radical production and lessened edema may be important factors in promoting ultimate survival of venous flaps.

Adenosine Triphosphate↗