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Biomedical subjects

C R Forrest

Publications and source records attributed to C R Forrest.

51 records · Page 3Linked to original sources
PubMed1992

Current concepts in the use of bone grafts in facial fractures. Basic science considerations.

In choosing the ideal donor site for bone replacement, attention must be given to the recipient site's revascularization potential and mechanical needs. Based on histologic differences in architecture as related to these two factors, the most appropriate graft type may be harvested. Future potential exists for bone replacement by distraction osteogenesis without the need for remote site harvesting. This may provide for the most identical bone replacement.

Biomechanical Phenomena↗
PubMed1991

Efficacy of intravenous infusion of prostacyclin (PGI2) or prostaglandin E1 (PGE1) in augmentation of skin flap blood flow and viability in the pig.

The dose-response effects of 6-h intravenous infusion of PGI2 (0, 5, 10, 25 or 75 ng/kg/min) or PGE1 (0, 25, 50, 100 or 300 ng/kg/min) on skin hemodynamics and viability were studied in 4 x 10 cm random pattern skin flaps (n = 24) raised on both flanks of the pig. Infusion of PGI2 or PGE1 was started immediately after intravenous injection of a loading dose 30 min before skin flap surgery. PGI2 infusion significantly (P less than 0.05) increased the total skin flap capillary blood flow at the dose of 10 ng/kg/min, compared with the control. However, the distance of blood flow along the skin flap from the pedicle to the distal end, i.e. perfusion distance, was not increased. Consequently, the length and area of skin flap viability was also not significantly increased. The effect of PGI2 infusion on skin blood flow was biphasic. Specifically, higher doses (greater than or equal to 25 ng/kg/min) of intravenous PGI2 infusion produced no beneficial effect on the skin flap capillary blood flow. PGI2 infusion at the dose of 10 or 75 ng/kg/min did not significantly increase plasma renin activities or plasma levels of norepinephrine compared with the control, therefore the biphasic effect of PGI2 on skin flap blood flow was not related to circulating levels of norepinephrine or angiotensin. Intravenous infusion of PGE1 did not produce any therapeutic effect on the skin capillary blood flow in the random pattern skin flaps at all doses tested. At the dose of 300 ng/kg/min, the mean arterial blood pressure was 17% lower (P less than 0.05) than the control, but the skin capillary flow still remained similar to the control. It was concluded that intravenous infusion of PGI2 or PGE1 was not effective in augmentation of distal perfusion or length of skin viability in the porcine random pattern skin flaps. Drug treatment modalities for prevention or treatment of skin flap ischemia is discussed.

Alprostadil↗
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↗
PubMed1991

The biomechanical effects of deep tissue support as related to brow and facelift procedures.

The adverse effects of increased tension across a healing wound are well known. However, the effect of closing a wound in layers in order to decrease tension on the epidermis has been a source of controversy. It is hypothesized that deep tissue support decreases skin tension upon wound closure. In order to clarify this issue, a two-part study was designed to address the immediate effects of deep tissue support in vitro using fresh-frozen cadavers and in vivo on patients undergoing scheduled surgery. Closing skin tension was measured at standard reference points in coronal brow lift and rhytidectomy procedures performed with and without galeal closure and superficial musculoaponeurotic system (SMAS) procedures, respectively. Deep tissue support was found to significantly (p less than 0.05) decrease skin tension at the time of skin closure at standard reference points in coronal brow lift and rhytidectomy procedures performed on fresh-frozen cadavers. Similar significant (p less than 0.05) decreases in closing skin tension also were found in vivo in patients undergoing similar surgical procedures. Stress relaxation was not found to play a significant role in contributing to this immediate decrease in closing skin tension. It would appear, therefore, that deep tissue support, in the form of galeal closure and an SMAS procedure in coronal brow lift and rhytidectomy procedures, respectively, provides increased viscoelastic support, producing immediate significant decreases in closing skin tension in these procedures. The beneficial effects on wound healing, scar formation, tension-related trophic skin changes, and possible improved long-term results are discussed.

Adult↗
PubMed1990

Role of noradrenaline in the pathogenesis of skin flap ischemic necrosis in the pig.

Clinically, ischemic necrosis is one of the most common complications in skin flap surgery, but the etiology is still unclear. The objective of the present experiments was to study the important role of the locally released noradrenaline in the pathogenesis of ischemic necrosis in acute and delayed random pattern skin flaps (4 x 10 cm) raised on both flanks of the pig. In Experiment 1, it was observed that 93, 96, and 94% of the skin contents of noradrenaline were depleted in skin flaps delayed for 2, 4, and 14 days, respectively, compared to the acute skin flaps (n = 8) raised in the same pig. Although the maximum depletion of noradrenaline in the delayed flaps occurred within 2 days of delay, significant (P less than 0.001) increase in the length of dye penetration in the delayed skin flaps was seen after 2 days of delay, compared to the acute skin flaps (n = 12). In Experiments 2 and 3, 5 days of intravenous phenoxybenzamine treatment, starting 2 days preoperatively and at the doses of 0.25, 0.5, 1.0, or 1.5 mg/kg/day, did not have any significant effect on the skin blood flow (n = 24) or viability (1 mg/kg/day; n = 32) in the acute skin flaps compared with the saline-treated control. Similarly, 5 days of intravenous phentolamine treatment (5 mg/kg/day) also did not have any significant effect on the skin blood flow (n = 24) or viability (n = 32) of acute skin flaps compared with the control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Pharmacological augmentation of skin flap viability: a hypothesis to mimic the surgical delay phenomenon or a wishful thought.

The importance of the research in skin flap pharmacology is two-fold. First, observations made from the vasoactive drug actions in the vasculature of skin flaps can provide insight into the regulatory mechanism of cutaneous circulation and the pathophysiology of ischemic necrosis in skin flap surgery. Second, there is the possibility that the aforementioned information may eventually contribute to the development of a drug treatment for the augmentation of skin blood flow and viability in acute skin flaps (i.e., to mimic the surgical delay mechanism). To this end, the objectives of this article are: (1) to present a brief review of the recent research progress in the pharmacological treatment of ischemic skin necrosis in experimental flap surgery, and (2) to attempt to identify the future directions and important areas of research to be pursued in the pharmacology of skin flaps.

Humans↗
PubMed1988

Latissimus dorsi musculocutaneous flap model in the rabbit: a hemodynamic and anatomical study.

The rabbit island and peninsular axial pattern latissimus dorsi musculocutaneous (LDM) flaps were assessed for their appropriate use as experimental musculocutaneous flap models. Contralateral island and peninsular LDM flaps (10 X 20 cm) were constructed on rabbits, and their vascular anatomy, hemodynamics, and viability were compared. Anatomical dissections and fluorescein dye studies revealed that the skin overlying the latissimus dorsi muscle received its blood supply mainly from a direct cutaneous branch of the thoracodorsal artery before its entry to the latissimus dorsi muscle. A few small musculocutaneous arteries (perforators) were seen in the proximal portion of the latissimus dorsi muscle, but these perforators provided very little blood supply to the overlying skin. Results from hemodynamic and viability studies with rabbit peninsular and island LDM flaps also indicated that the blood supply from the musculocutaneous arteries to the overlying skin paddle was small and could not reliably support the survival of the cutaneous portion of these musculocutaneous flaps. We conclude that rabbit LDM flaps are different in vascular structure and blood supply compared with the human LDM flaps. Thus, discretion should be advised in applying the rabbit peninsular or island LDM flaps as experimental flap models for the study of the pathophysiology and pharmacology of the musculocutaneous flaps relevant to the clinical situation.

Animals↗
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↗
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↗
PubMed1986

Hemodynamics and vascular sensitivity to circulating norepinephrine in normal skin and delayed and acute random skin flaps in the pig.

Cutaneous circulation in 4 X 10 cm skin samples and delayed and acute random skin flaps constructed on the flanks of castrated Yorkshire pigs (13.3 +/- 0.7 kg; n = 12) were studied during intravenous infusion (0.5 ml per minute) of 5% dextrose solution (vehicle) and 5% dextrose containing norepinephrine (1 microgram/kg per minute). Total and capillary blood flow and A-V shunt flow were measured by the radioactive microsphere technique 6 hours after the raising of 4 X 10 cm single-pedicle acute and delayed random skin flaps using the technique and calculations published previously. Fluorescein dye test was also performed to assess vascular perfusion. It was observed that the capillary blood flow in the single-pedicle delayed skin flaps was similar to that in the normal skin, and the maintenance of this normal skin blood flow was not due to the closing of A-V shunt flow in the delayed skin flaps. Similarly, the significant (p less than 0.01) decrease in capillary blood flow and distal perfusion in the acute skin flaps compared with the delayed skin flaps was not due to the opening of A-V shunts in the acute skin flaps. There was no evidence to indicate that A-V shunt flow per se was the primary factor for the regulation of capillary blood flow in the acute and delayed skin flaps in the pig. Our data seemed to indicate that tissue ischemia in the distal portion of acute skin flaps was likely the result of vasoconstriction of the small random arteries which supplied blood to arterioles and A-V shunts, and locally released neurohumoral substances may play an important role in the pathogenesis of vascular resistance and ischemia in the acute skin flaps.

Animals↗
PubMed1972

Further study of strontium selenite and selenite F broths for the isolation of Salmonella typhi.

The efficiency of strontium selenite and selenite F broths in the isolation of S. typhi from 625 clinical stool specimens were compared. A total of 126 strains of S. typhi were detected. Of these, 96 (76%) were isolated with selenite F broth and 118 (94%) were isolated with strontium selenite broth. At the same time, the number of false positive isolates accruing to strontium selenite broth was less than that accruing to selenite F broth. The superiority of strontium selenite broth over selenite F broth was more obvious when relatively few typhoid bacilli were present in faeces, eg, after antibiotic therapy, or when stools had been left for prolonged periods at room termperature. In the isolation of S. typhi with strontium selenite broth, salmonella-shigella agar was found to be a better plating medium than xylose lysine desoxycholate agar.

Agar↗
PubMedDate not supplied

Revision of neoclassical facial canons in young adult Afro-Americans.

The validity of seven neoclassical facial canons was tested in 100 young, adult, Afro-American (A-A) males and females, and the results were compared with 103 North American Caucasians, producing the first reliable information about the differences of facial proportions in the two populations. Although the canons should not be regarded as strict directives in reconstructive and esthetic surgery, the data obtained from the study offered the first information about the facial proportion qualities of Afro-Americans in relation to the white population. In the absence of a detailed facial proportion study in A-As, the findings in canons can assist in planning the surgery. Comparison of the two populations revealed that the three sections of the facial profile were not equal in either population. In an A-A sample it showed the prevalence of the long lower face height also in relation to the height of the forehead. In horizontal canons of the orbital regions, the similarity between the two populations was demonstrated by the great frequency of intercanthal spaces to be wider than the length of the palpebral fissures [1]. The facial canons, including the nose width, relatively wider [2] in A-A than in white subjects, prompted the difference between A-A and Caucasians in frequency and degree in the dominant canon variations. The greater inclination of the nasal bridge than that of the medial longitudinal axis of the ear was a very frequent canon variation in both populations. Generally, the frequency of valid canons was greatly surpassed by their variations.

Adult↗