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Biomedical subjects

L A Koman

Publications and source records attributed to L A Koman.

At least 37 records · Page 2Linked to original sources
PubMed1998

Endogenous nitric oxide influences arteriovenous anastomosis adrenergic tone in the conscious rabbit ear.

The role of nitric oxide (NO) in the control of arteriovenous anastomoses (AVAs) has not been studied in vivo in a thermoregulatory end organ. In this study, the effect of local inhibition of NO synthesis by NG-nitro-L-arginine methyl ester (L-NAME) on the microvasculature in the rabbit ear (n=12) was observed in vivo through a chronically implanted ear microvascular chamber. Ear cutaneous blood perfusion (CBP), total auricular arterial flow (TAF), and ear temperature were monitored simultaneously with the direct microvascular observations. Results revealed that intrafacial artery infusion of L-NAME produced significant vasoconstriction of arterioles, AVAs, and venules (p < 0.05). A decrease of ear blood perfusion also was demonstrated by changes of CBP, TAF, and surface temperature. The data provide evidence that basal generation of NO influences the vascular resistance in the thermoregulatory end organ. Moreover, endogenous NO production may be more important in regulating the AVA flow than is flow in other parts of the rabbit ear microvasculature. The effects of NO inhibition on ear microvasculature were not abolished by superior cervical ganglionectomy, indicating that NO production in the rabbit ear is not a neurally mediated mechanism. Further study with a short-term rabbit ear preparation showed that inhibition of NO production with L-NAME enhanced microvascular constrictive responses to extraluminal application of norepinephrine. NO thus appears to play a role of basal vasodilator in opposition to the basal adrenergic vasoconstrictor tone in the rabbit ear.

Animals↗
PubMed1998

Significance of cold intolerance in upper extremity disorders.

After upper extremity injury, pain on exposure to cold (cold sensitivity) is a significant problem. This cross-sectional observational study (1) assesses the incidence and prevalence of cold intolerance, (2) evaluates the relationship between functional status and degree of cold intolerance, and (3) correlates health-related quality of life (HRQL) with symptoms of cold intolerance. Patients in a tertiary care center completed questionnaires to document (1) cold sensitivity, (2) upper extremity pain, symptoms, and function, and (3) HRQL. Cold sensitivity was found to be associated with more functional limitations, greater pain, and reduced HRQL. As the severity of cold intolerance increased, functional limitations and pain increased and HRQL decreased. Cold intolerance has a profound effect on HRQL.

Activities of Daily Living↗
PubMed1997

Acute effects of periarterial sympathectomy on the cutaneous microcirculation.

The clinical effects of peripheral sympathectomy on patients with vaso-occlusive disease are often dramatic and include relief of pain, improved quality of life, and healing of ulcers. Peripheral periarterial sympathectomy is known to increase skin temperature and to maximize the nutritional component of peripheral blood flow, but the pathophysiology of vaso-occlusive disease and the physiologic mechanisms of this treatment are unknown. In this study, the acute effects of periarterial sympathectomy were directly observed in a rabbit ear model of digital microcirculation (arterioles, arteriovenous anastomoses, and venules). The effects of periarterial sympathectomy on cutaneous perfusion and total flow were also examined using laser Doppler perfusion imaging and digital temperature measurements. The central auricular artery became dilated (50-100%) immediately after sympathectomy; the arterioles, arteriovenous anastomoses, and venules dilated to 165, 156, and 223%, respectively, at 30 minutes and to 187, 174, and 204%, respectively, at 60 minutes, relative to their baseline diameters prior to sympathectomy. Laser Doppler perfusion imaging values and ear temperatures were noted to increase after sympathectomy (8.9%, 3 degrees C), although the core temperature of the rabbit did not change. Thus, acute periarterial sympathectomy can (a) effectively reduce the vascular tone of the distal microvasculature and (b) increase total microcirculatory perfusion-cutaneous and thermoregulatory-by both venular and arteriolar dilation. Periarterial sympathectomy has the clinical potential to increase nutritional blood flow, thereby ameliorating the signs and symptoms of ischemia associated with thermoregulatory abnormalities. Dilation of the arteriovenous anastomoses, with a subsequent reduction in vascular resistance, may contribute to the increased cutaneous temperature noted after sympathectomy.

Anastomosis, Surgical↗
PubMed1997

The fibula-flexor hallucis longus osteomuscular flap.

Limb salvage after loss of bone and soft tissue may require many operations to obtain soft-tissue cover and bony continuity. We describe a fibula-flexor hallucis longus osteomuscular flap which can provide both soft tissue and bone in a single stage. The flap is based on the peroneal vessels and is covered by a split-thickness skin graft. We report the results in five patients with an average bone defect of 8.3 cm and soft-tissue and skin loss. All regained a normal gait on the donor side; four had clinical and radiological union with excellent soft-tissue cover, but one required later amputation due to diffuse coagulopathy. The flap provides free vascularised bone with muscle cover. It has a dependable, long pedicle with minimal morbidity at the donor site, and allows monitoring of the vascularity of the fibular graft.

Adolescent↗
PubMed1997

Management of vasospastic disorders of the hand.

Vasospastic disorders of the upper extremity are common and often difficult to treat. Using the proposed classification system (Table 2) allows management based upon pathologic condition, physiologic staging, and response to treatment. Identifying patients in this way also helps in determining which treatments are most appropriate. The basic approach to management includes environmental and behavioral modifications including cessation of tobacco use, protection of hands, and avoidance of situations that trigger the vasospastic response. Pharmacologic therapy may provide good results in a majority of patients. Surgical intervention is reserved for patients with vaso-occlusion, ischemia, and refractory symptoms in spite of attempts at medical management. Surgical options include vascular reconstruction, peripheral sympathectomy, or a combination of techniques. The goal of medical and surgical management is to increase total or nutritional blood flow in the digits.

Hand↗
PubMed1997

Congenital pseudarthrosis of the tibia treated with free vascularized fibular graft.

Management of patients with deformities due to congenital pseudarthrosis of the tibia continues to be controversial. The use of free vascularized fibular grafts in the reconstruction of these deformities appears to be successful in this patient population but is not without potential for significant complications. Long-term evaluation, at least to skeletal maturity, is necessary to judge the success of any procedure done for any pediatric patient. This case illustrates the natural history of the vascularized free fibular graft for congenital pseudarthrosis of the tibia in a young child. Complications of this treatment modality did occur, including probable recurrence and fracture at almost 11 years post-index procedure. However, stable reconstruction leading to fracture union was achieved, and the patient has resumed full activities with little residual deformity.

Adolescent↗
PubMed1996

The histological effect of barrier vein wrapping of peripheral nerves.

Twenty-four Sprague-Dawley rats underwent exploration and exposure of the sciatic nerve, followed by sham isolation, irrigation, and subsequent wound closure (Group 1); barrier vein wrapping of the nerve using glutaraldehyde-preserved allograft inferior vena cava (Group 2); or barrier vein wrapping of the nerve with femoral vein autograft from the contralateral extremity (Group 3). Four months later, the rats were sacrificed and the nerves fixed in situ in buffered glutaraldehyde. Sections proximal, mid-portion, and distal to the barrier and vein wrap were fixed with osmium tetroxide, epon embedded, stained with toluidine blue, and studied under x200 and x400 light microscopy. Epineural scar formation increased 10 times in Group 2, compared to Group 3 (p < 0.0001). Epineural thickness and the number of degenerating axons did not differ significantly among all groups. Inflammatory cells in Group 2 increased 100 times, compared to Group 3 (p < 0.0001). Continuing with the underlying epineural layer was apparent grossly and microscopically with all allografts, but with no autografts. Thus, glutaraldehyde-preserved allograft vein wraps appear to incite a marked inflammatory response, with epineural scarring and adherence to the underlying nerve, while autograft vein wraps do not.

Animals↗
PubMed1996

Control of arteriovenous anastomoses in rabbit ear model of digital perfusion.

The arteriovenous anastomoses (AVA) of the cutaneous microcirculation of the hands and feet are fundamental determinants of thermoregulatory blood flow and may be involved in cold intolerance. These direct microvascular studies are an initial characterization of adrenergic receptor subtypes participating in control of AVA in the ears of anesthetized male New Zealand White rabbits. Adrenergic alpha 1-stimulation with phenylephrine produced AVA constriction, whereas terazosin (an alpha 1-antagonist) produced dilation and attenuated the responses to phenylephrine. Adrenergic alpha 2-stimulation with UK-14304 produced constriction of the AVA, whereas atipamezole (an alpha 2-antagonist) produced dilation and attenuated the responses to UK-14304. When equimolar concentrations of antagonists were studied, the AVA dilation produced by alpha 2-blockade was greater than that produced by alpha 1-blockade. Norepinephrine (a mixed alpha 1- and alpha 2-agonist) also produced vasoconstriction, which was attenuated by both prazosin (an alpha 1-antagonist) and atipamezole. In summary, 1) AVA contain a heterogeneous mixture of both alpha 1- and alpha 2-receptors, and 2) alpha 2-receptors may have a greater influence than alpha 1-receptors on overall tone in AVA.

Animals↗
PubMed1996

Neuromuscular blockade in the management of cerebral palsy.

Neuromuscular blocking agents-45% alcohol, 4% to 6% aqueous phenol, local anesthetics, and botulinum A toxin-have been used for many years in the evaluation and management of spasticity and movement disorders in children with cerebral palsy. Recent reports suggest that longer-acting neuromuscular blocking agents may impact positively on the natural history of dynamic deformity and improve health-related quality of life. This review includes the mechanism of action, techniques, indications, complications, and clinical outcomes associated with these agents.

Cerebral Palsy↗
PubMed1996

The pharmacologic approach to the painful hand.

The management of reflex sympathetic dystrophy with oral, topical, and parenteral medications is complex. This article outlines the pharmacologic options available to treat dystrophic pain, provides an overview of mechanisms-of-action, and defines relative indications for administration.

Hand↗
PubMed1996

The painful hand.

RSD can be approached using objective criteria in a logical and systematic fashion. Frustration during treatment is common because (1) the pathophysiology of RSD is incompletely understood, (2) there is significant variation in presentation because of disparate premorbid anatomy and physiology, and (3) the natural history may be affected by incomplete treatment. Therapeutic efforts that theoretically should be effective may fail, and a trial-and-error approach is often mandatory. In spite of vigorous intervention using all known strategies, patients may continue to have pain and disability that progresses to stiffness and arthrofibrosis. Early recognition and prompt intervention, however, provide the best opportunity for clinical improvement.

Hand↗
PubMed1995

The microcirculatory effects of peripheral sympathectomy.

Microvascular physiology following peripheral artery sympathectomy was evaluated in seven hands with refractory pain (n = 7) and ulceration (n = 7) by serial isolated cold stress testing, which measures digital temperature and cutaneous perfusion (laser Doppler fluxmetry). All patients (n = 6) had vasospasm (secondary Raynaud's phenomenon) and arteriographically proven digital and palmar occlusive disease. Microcirculatory flow responses were correlated with symptoms and signs (including ulcer healing) before and after (2-8 weeks, 12-15 weeks, and 24 weeks) peripheral sympathectomy. Baseline data were compared with those of controls (n = 7 extremities). Following surgery, all seven hands had diminished pain; six had ulcer healing and one had ulcer reduction. Isolated cold stress testing demonstrated abnormalities in temperature and laser Doppler fluxmetry response between patients and controls. Although total flow (reflected by temperature) was not significantly increased after surgery, peripheral sympathectomy increased nutritional flow in these patients with combined vasospastic vessels and occlusive injury. The clinical changes observed following peripheral sympathectomy appear to be related to postsurgical correction of abnormal arteriovenous shunting and to improved nutritional blood flow to ischemic areas. This accounts for the resultant diminution of pain and healing of ulcers observed in these patients after surgery.

Adult↗
PubMed1994

Decreased microvascular perfusion in the rabbit ear after six hours of ischemia.

The cellular injury produced by reperfusion of ischemic tissue with oxygen-rich blood has been studied in numerous tissues but has not been investigated extensively in thermoregulatory tissue. This study was designed (a) to compare 4 and 6 hours of ischemia to document the evidence of impaired capillary perfusion after resumption of blood flow (reperfusion injury) in a thermoregulatory end organ (the rabbit ear), and (b) to examine, with use of vital capillaroscopy (VC) and laser Doppler flowmetry (LDF), the altered microvascular blood flow in the rabbit ear after ischemia and reperfusion. One ear from each of five rabbits underwent warm ischemia for 4 hours. VC showed no deficits of capillary perfusion in these ears after reperfusion; LDF measurements in both ears also demonstrated no significant difference between control and reperfusion blood flow. One ear from each of eight additional rabbits underwent 6 hours of warm ischemia. LDF values were significantly reduced in the ischemic ear after reperfusion as compared with baseline measurements for that ear and as compared with the control ear. VC showed arrested perfusion and static plasma gaps within three to five capillaries per high-power field (an area of 300 x 500 microns) in the ischemic ear and good perfusion of all vessels in the contralateral control ear. This evidence of reperfusion injury in a thermoregulatory end organ may help to explain the poor functional result that often occurs after replantation of an amputated digit.

Animals↗
PubMed1994

Microvascular response in the rabbit ear to total body cooling: a model for study of human digits.

Conditions such as Raynaud's disease, cold intolerance following digit replantation, and reflex sympathetic dystrophy are all exacerbated by diminished blood flow in the digits. The rabbit ear, being similar to the human digit, is an excellent model for studying microvascular responses during thermoregulation and was used in this study of microcirculatory changes during total-body cold stress. In eight rabbits a window was placed in one ear each, and the underlying vascular beds were photographed with the unanesthetized animal at room temperature (23 degrees C) and in a cold room (6 degrees C). Luminal arterial diameters constricted more than venular diameters during cold stress (39.6% vs. 16.5%, respectively, of the control diameters; P = 0.014). All responses were linear; the slopes of the regression lines were significantly different between arterioles and venules (P < 0.0001). This study suggests that decreased circulation in response to cold is due to decreases in the diameter and number of vessels available for perfusion, as predicted by the Poiseuille equation.

Animals↗
PubMed1994

A rabbit ear model for cold stress testing.

A rabbit ear model resembling the human digit was studied to determine the vascular response of the rabbit ear to a cold stress. Following moderate cooling (10 minutes at 5 degrees - 8 degrees C), auricular blood flow and cutaneous perfusion were reduced. This decrease was reversed by 30 minutes of warming. The response in the rabbit ear to cold stress is similar to that of normal human digits. The similarities between the control of the circulation in human digits and rabbit ears may result from the similarities in digital and auricular vascular receptors and receptor subtypes. Verification of the rabbit model provides an experimental method for obtaining important data regarding digital pathophysiology and the treatment of cold intolerance. Further study with this model will provide clinically relevant information regarding the pathophysiology of digital thermoregulatory abnormalities.

Animals↗
PubMed1993

New skeletal muscle model for the longitudinal study of alterations in microcirculation following contusion and cryotherapy.

This preliminary report describes the use of a rat model developed to study in vivo the effect of anesthesia, contusion, and cryotherapy on skeletal muscle microcirculation by use of an implanted chamber. The diameters of arterioles and venules within the chamber were determined by photomicroscopy in the contusion study and by compound videomicroscopy in the anesthesia study; microvascular perfusion was determined by laser Doppler fluxmetry (LDF). Combined ketamine and xylazine anesthesia significantly reduced (P < 0.05) arteriolar and venular diameters by 32.4% and 37.8%, respectively, and average LDF measurements by 36.1%. Contusion significantly increased arteriolar diameters over baseline values (P < 0.05); cryotherapy did not alter arteriolar diameters but increased venular diameters (P < 0.05). It is hypothesized that this increase in venular diameter may, by increasing the surface area available for reabsorption, explain one mechanism by which cryotherapy decreases the edema of contusion. Use of this model should help to advance the understanding of microcirculatory dynamics following contusion and cryotherapy.

Anesthesia↗