Biomedical subjects

W K Lindsay

Publications and source records attributed to W K Lindsay.

At least 19 recordsLinked to original sources

PubMed1991

Pathogenesis of ischemic necrosis in random-pattern skin flaps induced by long-term low-dose nicotine treatment in the rat.

The objectives of the present experiments were to study the effects of long-term low-dose nicotine treatment on skin hemodynamics, viability, and microvascular morphology in 4 x 10 cm dorsally based acute random-pattern skin flaps in the rat. In addition, the reversibility of the nicotine-induced detrimental effects on skin-flap viability following cessation of nicotine treatment also was investigated. Low-dose nicotine (0.6 mg/kg) administered twice daily and subcutaneously for 24 weeks significantly (p less than 0.05) decreased skin-flap capillary blood flow, distal perfusion, and length and area of skin viability compared with the saline-treated control (n = 15). However, these same parameters in rats (n = 15) whose nicotine treatment had been withheld for 2 weeks prior to skin-flap surgery were not significantly different from the control, thus indicating that the detrimental effects of this long-term, low-dose nicotine treatment were reversible. The mean plasma level of nicotine in the nicotine-treated rats was 8.1 +/- 0.4 micrograms/dl and was within the range of plasma nicotine levels reported for human heavy cigarette smokers. Light and electron microscopic studies did not show evidence of histologic damage to the cutaneous microvasculature in acute random-pattern skin flaps and samples of normal (nonoperated) skin in nicotine-treated rats. It is concluded that long-term plasma levels of nicotine similar to those of heavy cigarette smokers are detrimental to the capillary blood flow and viability of random-pattern skin flaps in the rat. These deleterious effects can be avoided if skin flaps are raised 2 weeks after cessation of nicotine treatment. This low-dose nicotine treatment does not cause histologic damage to the microvasculature. Other pathogenic mechanisms of nicotine-induced skin flap ischemia are discussed.

Animals↗

PubMed1989

History of the University of Toronto plastic surgery training program.

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Education, Medical, Graduate↗

PubMed1987

Dose and time effects of nicotine treatment on the capillary blood flow and viability of random pattern skin flaps in the rat.

The deleterious effects of nicotine treatment on skin haemodynamics and survival of 4 X 10 cm acute random pattern skin flaps constructed on the dorsum of the rat were studied. Rats were injected subcutaneously with 0.2 ml of saline containing varying doses (0, 1, 2, 4 or 8 mg kg-1; bid) of nicotine for 5 weeks, starting 4 weeks before flap surgery. It was observed that nicotine treatment at the dose of 2 mg kg-1 (bid), or higher, significantly (p less than 0.05) decreased the length and area of skin flap survival compared with the control. This dose of nicotine treatment also significantly (p less than 0.05) decreased the capillary blood flow and distal perfusion in the skin flaps compared with the control. However, the detrimental effect of nicotine treatment on the survival of acute random pattern skin flaps was not seen if the treatment was started 2 instead of 4 weeks preoperatively. It is concluded that nicotine may cause hypoperfusion and necrosis in acute random pattern skin flap surgery, and the deleterious effects are time-dependent.

Animals↗

PubMed1987

Abnormal carotid arteries in the velocardiofacial syndrome: a report of three cases.

Internal carotid arteries of unusual size and tortuosity were found before or at the time of pharyngeal flap surgery in three children who had the velocardiofacial syndrome with velopharyngeal insufficiency. In two cases, medial displacement of the arteries prevented surgery, and in the other, hypernasality persisted because only a narrow, asymmetrical flap could be raised. Medial displacement of the internal carotid arteries inhibits surgical treatment of velopharyngeal insufficiency, necessitating treatment with a prosthetic speech device in such children. Since displacement and tortuosity may be associated findings in the velocardiofacial syndrome, the exact location of the internal carotids should be ascertained when pharyngeal flap surgery is planned.

Abnormalities, Multiple↗

PubMed1986

Functional, mechanical, and biochemical assessment of ultrasound therapy on tendon healing in the chicken toe.

We studied the therapeutic effect of ultrasound treatment on the functional recovery of surgically repaired profundus tendon in the right third toe of mature White Leghorn hens. Ultrasound treatment was given daily for 5 minutes for a total of 20 treatment days, starting immediately after 4 weeks immobilization. Ultrasound (frequency 3.0 mHz; intensity 0.75 W/cm2) was delivered to the right leg by a 5-cm2 probe through distilled water in a bath kept at 35 degrees C. The flexion of the toe was measured preoperatively for 4 consecutive days and daily for 6 weeks after the start of ultrasound treatment for the calculation of percent of functional recovery of the flexor tendon. The non-ultrasound-treated group of birds went through the same manipulations except that no ultrasound was given when the right leg was immersed in the water bath. Ultrasound treatment significantly (p less than 0.01) improved the functional recovery of the repaired tendons (less than 5-mm gap) starting on the third week of treatment (94 +/- 2 percent) compared with the non-ultrasound-treated group (79 +/- 4 percent). Ultrasound treatment had no effect on gap formation or breaking (tensile) strength of the repaired tendons. It is concluded that ultrasound enhanced functional return of repaired flexor tendons in the hen, and the clinical implication is discussed.

Animals↗

PubMed1986

Augmentation of blood flow in delayed random skin flaps in the pig: effect of length of delay period and angiogenesis.

Skin capillary blood flow and angiogenesis were studied by radioactive microsphere and morphometry technique, respectively, in delayed random skin flaps in the pig. Skin flaps were delayed for 2, 3, 4, 6, or 14 days. Blood flow was measured 6 hours after complete raising of acute and delayed random skin flaps on the opposite flanks of the same pig. It was observed that the capillary blood flow increased significantly (p less than 0.05) within 2 days of delay compared to the acute skin flaps. This capillary blood flow further increased by about 100 percent between days 2 and 3, started to plateau after day 3, and remained unchanged between days 4 and 14 of delay. This increase in capillary blood flow was mainly in the distal portion of the delayed skin flaps. There was no indication of an increase in the density of arteries in all delay periods studied. Our observations did not support the hypotheses that the delay phenomenon involves angiogenesis or long-term adaptation to ischemia, as have been hypothesized previously. The possible mechanism of delay is discussed.

Animals↗

PubMed1985

Pharmacologic action of isoxsuprine in cutaneous and myocutaneous flaps.

The therapeutic effects of isoxsuprine on skin capillary blood flow and viability were studied in arterial buttock flaps, latissimus dorsi myocutaneous flaps, and random skin flaps in pigs. It was observed that parenteral isoxsuprine increased capillary blood flow to the skin of arterial buttock flaps and the skin and muscle of latissimus dorsi myocutaneous flaps in a dose-response manner, with a maximum vascular effect observed at 1.0 mg/kg. However, this maximum effective dose of isoxsuprine did not have any significant effect on skin viability in the cutaneous and myocutaneous flaps compared with the control. Examination of the distribution of capillary blood flow within the flaps at varying distances from the pedicle revealed that isoxsuprine did not increase capillary blood flow or perfusion distance in the distal portion of the skin of arterial buttock flaps, latissimus dorsi myocutaneous flaps, and random skin flaps. The increased capillary blood flow as a result of isoxsuprine treatment was limited only to the arterial portion of the arterial buttock flaps and latissimus dorsi flaps. Therefore, it is concluded that isoxsuprine alone is not effective in augmentation of skin viability in cutaneous and myocutaneous flaps. The pharmacologic action of isoxsuprine on the vasculature in the skin and muscle of flaps was also discussed.

Animals↗

PubMed1985

Effect of glucocorticoid treatment on skin capillary blood flow and viability in cutaneous and myocutaneous flaps in the pig.

The effect of methylprednisolone treatment on skin-flap viability and capillary blood flow was studied in a series of four experiments. Intramuscular methylprednisolone injections (30 mg/kg per day), given in single or divided doses preoperatively or postoperatively, had no effect in augmenting skin viability in arterialized cutaneous, myocutaneous, or random skin flaps compared with the control. Capillary blood flow was studied in arterial buttock flaps and latissimus dorsi myocutaneous flaps raised on animals treated preoperatively with methylprednisolone or saline (control), and no significant difference in capillary blood flow was noted between the treatment and control flaps. It was concluded that methylprednisolone has no significant therapeutic effect either in increasing flap viability or in increasing capillary blood flow in skin flaps in pigs.

Animals↗

PubMed1980

Upper extremity gangrene: a complication of subclavian artery division.

Gangrene of the upper extremity is a rare complication following subclavian artery ligation. Two case reports from the 23-year experience at the Hospital for Sick Children are presented. If gangrene is to be eliminated in such cases, early recognition of inadequate limb perfusion is mandatory. A suspicion of inadequate perfusion justifies heparin therapy, and prompt revascularization and fasciotomy must be considered.

Aortic Coarctation↗

PubMed1980

Functional return of tendon graft protected entirely by pseudosheath--experimental study.

Sixty-three white Leghorn chickens were used in a two-stage tendon grafting into the deep flexor of the third toe. In the first stage, a 4- or 8-week-old pseudosheath was created around the Silastic rod. In the second stage, the grafting was carried out: in 33 birds the new sheath covered the entire tendon graft and its junctions; in 30 controls, only the main portion of the graft was covered by pseudosheath. Following 6 weeks of immobilization, the toe was left free for 8 weeks and active flexion was registered once a week at perching. The covered junctions were found to be of high anatomical quality; they were, on an average, stronger, and flexion return was significantly greater (in 8-week-old pseudosheath) when compared with noncovered control grafts.

Animals↗

PubMed1980

Silastic rod pseudosheaths and tendon graft healing.

By examining the breaking strength and gap formation of tendon graft junction sites covered with pseudosheath at various times of immobilization, no significant increase was found compared to junction sites not covered by the pseudosheath. The optimum time for immobilization following tendon grafting is between 4 and 5 weeks in the chicken. Total coverage of the junction sites by pseudosheath did not affect gap formation.

Animals↗

PubMed1979