An improved model for tissue expansion and flap research in the rabbit

A pocket for tissue expander implantation in the rabbit is described at the level between the skin and the panniculus carnosus. The vascular anatomy of the undermined skin was studied with microangiography which showed a functional (sub)dermal plexus. Expanders were placed in seven rabbits and inflated daily over a period of 10 days. Blood flow in expanded skin, as measured with laser Doppler flowmetry, dropped with increasing inflation pressure. During the course of expansion, the intraluminal pressure returned to a baseline level within 24 hours after each inflation. It is concluded that an expander placed in the described layer in the rabbit causes considerable skin stretch and interferes with cutaneous blood supply and is therefore an improved model for tissue expansion in the human.     

皮肤外扩张延迟作用的实验研究

临床上进行皮肤外扩张治疗过程中，发现外扩张后的皮肤有类似延迟的作用。为探索其变化的机理，选用２０只新西兰大白兔，随机分为２组，实验组为皮肤外扩张组，对照组为不扩张组。各组应用激光多普勒血流计（ＬＤＦ）及血氧饱和度（ＳｐＯ２）检测计进行皮肤微循环血流监测，并对２组皮瓣成活面积及微血管造影的结果进行比较。结果表明：实验组１２天后，ＬＤＦ值比未扩张前增高，ＳｐＯ２值恢复到扩张前水平；皮瓣成活面积明显高于对照组；微血管造影皮下血管吻合支明显增多。认为，外扩张后的皮肤生存质量未较正常皮肤下降，并有近似于延迟的作用。     

皮肤外扩张延迟作用的实验研究

临床上进行皮肤外扩张治疗过程中,发现外扩张后的皮肤有类似延迟的作用。为探索其变化的机理,选用20只新西兰大白兔,随机分为2组,实验组为皮肤外扩张组,对照组为不扩张组。各组应用激光多普勒血流计(LDF)及血氧饱和度(SpO_2)检测计进行皮肤微循环血流监测,并对2组皮瓣成活面积及微血管造影的结果进行比较。结果表明:实验组12天后,LDF 值比未扩张前增高,SpO_2值恢复到扩张前水平;皮瓣成活面积明显高于对照组;微血管造影皮下血管吻合支明显增多。认为,外扩张后的皮肤生存质量未较正常皮肤下降,并有近似于延迟的作用。     

The rabbit ear pedicle flap. A new model for evaluating factors affecting the circulation in flaps

Laser Doppler flowmetry and transcutaneous oximetry were compared regarding their speed and accuracy in detecting occlusion of the artery of an experimental rabbit ear pedicle flap. The laser Doppler flowmeter showed a significant decrease in flow and the transcutaneous oximeter showed a significant decrease in oxygen tension within one minute after occlusion of the artery. A significant increase in flow was observed within one minute, and a significant increase in oxygen tension readings was observed one minute after the artery was opened. A steady state after opening the artery was reached sooner for the laser Doppler flowmeter readings. This study suggests that laser Doppler flowmetry and transcutaneous oximetry are equally fast and accurate in detecting changes in blood flow to a pedicle graft. These methods also have equally good reproducibility. Repeated clampings within a 30 min period did not affect the measured parameters.     

The correlation between three methods of skin perfusion pressure measurement: radionuclide washout, laser Doppler flow, and photoplethysmography.

The most accurate measurement of skin perfusion pressure is made with use of radioisotopic clearance techniques. We compared the skin perfusion pressure using radioisotope to the skin perfusion pressure measured simultaneously by placing laser Doppler and photoplethysmography probes within a transparent polyvinylchloride plastic blood pressure cuff in 13 subjects. A new device, which was created for this experiment, consisted of a plastic bladder into which light-emitting probes can be placed, so that the pressure applied to the skin was transmitted by the surface of the bladder, rather than by the surface of a rigid probe. The cuff was inflated to a supra-systolic pressure over the intradermal injection site of technetium Tc 99m, then deflated in 10 mm Hg decrements at 3-minute intervals. The pressures at which radioisotope clearance began, at which microcirculatory flow was detected by laser Doppler, and at which deflection of the photoplethysmography (DC mode) output occurred, were recorded as the skin perfusion pressure. The range of radioisotopic determined skin perfusion pressure was 0 to 100; skin perfusion pressure-laser Doppler was 0 to 100; and skin perfusion pressure-photoplethysmography was 60 to 100, with 7 of 13 limbs demonstrating no clear deflection point and thus an unobtainable skin perfusion pressure-photoplethysmography reading. Linear regression revealed a coefficient of correlation of 0.991 for skin perfusion pressure when the radioisotopic and laser Doppler methods were compared. Our study is not in agreement with previous reports of the successful determination of skin perfusion pressure with use of photoplethysmography. This may be due to differences in our technique when compared with previous reports of skin perfusion pressure-photoplethysmography determination.(ABSTRACT TRUNCATED AT 250 WORDS)     

Skin blood flow measured by laser Doppler flowmetry under enflurane anesthesia or modified neuroleptanesthesia during abdominal surgery

In 18 patients for abdominal operations, the skin blood flow of the sole was measured with a laser Doppler flowmeter under general anesthesia. The deep body temperature was also measured. During the induction of anesthesia with thiopental, an elevation of the skin blood flow was observed. The elevation was due to administration of thiopental. After the induction, the elevation appeared to be more prolonged under nitrous-oxide and enflurane anesthesia than under diazepam or droperidol, with nitrous-oxide and fentanyl anesthesia. The persistent elevation was observed for 104 +/- 10 minutes under enflurane anesthesia in 10 patients, but the elevation was 71 +/- 7 minutes under modified neuroleptanesthesia in 8 patients. This difference might be associated with the peripheral vasodilatation by enflurane and the short peripheral vasodilatation by droperidol or diazepam. Increases of the skin blood flow correlated well with the changes of the deep temperature of the sole. These results indicate that the peripheral skin blood flow is different during long operation between enflurane anesthesia and modified neuroleptanesthesia and the laser Doppler flowmetry is a useful tool as a monitor of peripheral circulation and body temperature.     

The influence of radiotherapy on skin circulation of the breast after subcutaneous mastectomy and immediate reconstruction.

The skin circulation was measured in 43 breast cancer patients following subcutaneous mastectomy and immediate reconstruction with a prosthesis, at least 1 year after radiotherapy (46 Gy) following surgery (19 patients) or if no radiotherapy was given, at least 1 year postoperatively (24 patients). The skin circulation was measured by laser Doppler fluxmetry (LDF) and fluorescein flowmetry within three areas: 2 cm above the border of the areola, within the nipple-areola complex, and 2 cm below the border of the areola. The results show that there was no reduction in skin circulation. On the contrary LDF and fluorescein flowmetry showed in the operated breast an increased circulation in the nipple-areola complex in the irradiated breast compared with the non-irradiated by 26% and 30%, respectively (P < 0.05). The results indicate that radiotherapy following subcutaneous mastectomy and immediate reconstruction with a prosthesis does not lead to long-term reduction in basal skin circulation in the breast.     

Tissue oxygenation and skin blood flow in the diabetic foot: responses to cutaneous warming

We previously reported an unexpected statistically significant decline in the mean transcutaneous partial pressure of oxygen (TcPO2) with cutaneous warming from 37 degrees C to 44 degrees C on the plantar diabetic foot, as opposed to the expected increase seen at the dorsal sites. To elucidate this relationship we compared changes with cutaneous warming in TcPO2 and skin circulation measured by laser Doppler flowmetry on the right plantar foot surface of 20 consecutive subjects. Neuropathy by monofilament testing was present in 55% of the cases. Right dorsal foot TcPO2 increased with cutaneous warming from 37 degrees C to 44 degrees by a mean change of +43.6+/-20.7 mmHg (+/- standard deviation) in 95% of the cases. In 42% of cases right plantar first metatarsal head TcPO2 fell with warming from 37 degrees C to 44 degrees C by a mean change of -10.7+/-7.6 mmHg. In the remaining 58% of cases right plantar first metatarsal head TcPO2 rose by 6.8+/-6.3 mmHg. In 95% of cases right plantar great toe laser Doppler perfusion units (LDPU) increased with warming from 36 degrees C to 44 degrees C by a mean change of +50.4+/-37.1. Blood flow measured by laser Doppler flowmetry increased in 95% of the subjects with heating. The finding that blood flow was increased with warming contradicts the hypothesis that arterioles in the plantar great toe cannot vasodilate in response to thermal stimuli. This finding supports the hypothesis that the decline in TcPO2 with warming might be due to an increase in epidermal oxygen consumption that exceeds the increase in oxygen delivery due to increased blood flow. The pathological mechanisms behind microvascular dysfunction in skin microcirculation in the diabetic foot need further investigation.     

The effect of antiseptics on the healing wound: a study using the rabbit ear chamber

The effects of several antiseptic agents on granulation tissue were studied using rabbit ear chambers as models of the healing wound. This enabled us to study dynamically the action of these agents on the microcirculation of the wound. All the agents tested caused some adverse effect, but in the cases of hypochlorite antiseptics Eusol and Chloramine T, blood flow in the capillary circulation of the granulation tissue ceased and the process of repair was subsequently delayed. A laser Doppler flowmeter was used to measure these changes in local perfusion which reflected the toxic effects seen on microscopy of the ear chamber.     

On expander pressure and skin blood flow during tissue expansion in the pig

The structural and circulatory dynamics of expanded skin in connection with expander fillings were assessed in pigs following 7, 14, and 21 days of expansion by measuring the pressure of te fluid in the expander (Pexp) and the dermal blood flow. The results differed consistently on thoracic and abdominal sites. It was suggested that the stimulus to expansion be defined as the relative increase in extensible surface area of the expander. When plotting this value against Pexp, as measured at the end of injection, there was a good fit to an exponential curve. The area/Pexp relation was used to assess the connective tissue reaction around the expander; the reaction was most pronounced at 21 days. The decrease in Pexp after injection of fluid to 100 mm Hg showed that the tissue adapted rapidly during the first hour. Blood flow in the skin covering the expander was lower than on adjacent normal skin, and there was no increase during the three weeks of expansion. The decreases in blood flow were moderate even after injection of fluid until Pexp reached 100 mm Hg. It was suggested that the connective tissue capsule might protect the dermis from flow decrease.     

Effect of beta-blockers on peripheral skin microcirculation in hypertension and peripheral vascular disease

OBJECTIVE: This study was undertaken to investigate the possible negative effect of beta-blockers on skin microcirculation in patients with intermittent claudication and hypertension.Methods and materials In this clinical crossover study, 20 patients with mild to moderate hypertension, treated with long-term beta-blockade, and intermittent claudication or ischemic rest pain, underwent assessment of peripheral circulation before and after 2-week withdrawal of beta-blocking therapy and again 2 weeks after restarting therapy. Replacement therapy (calcium antagonist) was given if considered necessary to control hypertension. Skin microcirculation was assessed with three noninvasive techniques: capillary microscopy of the hallux nailfold, transcutaneous oximetry of the forefoot, and laser Doppler fluxmetry of the great toe. RESULTS: Mean initial blood pressure was 163/81 mm Hg. Mean heart rate significantly increased with withdrawal of beta-blocker, from 65 bpm to 85 bpm. No significant differences in skin microcirculation and blood pressure were found between measurements obtained before, during, and after withdrawal of beta-blocking therapy. Patients experienced no change in symptoms during the study. CONCLUSION: beta-Blockers do not appear to have a negative effect on peripheral skin microcirculation and are therefore not contraindicated to treat hypertension when intermittent claudication or ischemic rest pain is also present.     

Serial measurement of blood flow in expanded tissue by laser Doppler velocimetry

This study provides additional information about changes in blood flow in expanded tissue as measured by laser Doppler. Five one-kilogram albino Hartley guinea pigs were implanted with commercially available hemispheric expanders. The expanders were inflated every 3 days on four successive occasions. Blood flow measurements were taken on each animal just before each inflation, immediately after inflation, and then at 1, 2, 3, 4, and 24 hours after expansion. Measurement of flow changes immediately after each inflation of the expander showed that, initially, blood flow in the tissue overlying the expander recovered quickly, but as the expansion process was continued, the flow did not return to baseline values so rapidly. This might be an indication that tissue expansion in patients could be carried out more rapidly during the initial inflations, with increasing recovery periods between inflations as the expansion process continued.     

The value of laser Doppler velocimetry and transcutaneous oxygen tension determination in predicting healing of ischemic forefoot ulcerations and amputations in diabetic and nondiabetic patients

The ability to predict successful healing of ulcerations and amputations of the ischemic forefoot continues to be a major clinical challenge, particularly in diabetic patients whose systolic Doppler ankle pressures are often artifactually elevated. We have used the techniques of laser Doppler velocimetry (LD) and transcutaneous oxygen tension monitoring (tcPO2) to quantitatively measure skin blood flow in the distal foot. Fifty-nine limbs were studied (48 patients), of which 37 (63%) were in diabetic and 22 (37%) in nondiabetic patients. All patients were admitted with ischemic ulcerations or gangrenous changes of the forefoot or digit. Twenty transmetatarsal or digital amputations were performed; the remainder of the lesions were débrided and allowed to heal by secondary intention or were covered by a skin graft. Before operation, the systolic pressure (expressed in millimeters of mercury, mean +/- SEM) was measured by Doppler technique at the ankle, and the ankle/arm index calculated (n = 59 limbs). The tcPO2 (also expressed in millimeters of mercury, mean +/- SEM) was measured from the dorsal foot (n = 56). The baseline skin blood flow velocity (SBFV) and pulse wave amplitude (PWA) were measured with the LD (expressed in millivolts, mean +/- SEM) on the plantar aspect of the foot (n = 53 limbs). Criteria for successful healing included a tcPO2 of more than 10 mm Hg, the combination of an LD-SBFV of more than 40 mV and an LD-PWA of more than 4 mV, and an ankle systolic pressure of more than 30 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)     

一次性软组织扩张的实验研究

为了探索一次性软组织扩张的可能性，应用激光多普勒微循环血流仪（ｌａｓｅｒｄｏｐｐｌｅｒｆｌｏｗｍｅｔｅｒ，ＬＤＦ），在９只健康雄性白色乳猪躯干部作一次性软组织扩张术（ｉｎｔｒａｏｐｅｒａｔｉｖｅｓｕｓｔａｉｎｅｄｌｉｍｉｔｅｄｅｘｐａｎｓｉｏｎ，ＩＳＬＥ），共对５４个ＩＳＬＥ扩张的皮肤进行微循环监测，同时对扩张囊内压力与ＩＳＬＥ皮肤血流的相关性及ＩＳＬＥ皮肤病理学变化进行了探讨。结果表明：一次性扩张的皮肤，其微循环灌注量显著高于对照组，可提供更多的额外皮肤。为临床应用一次性软组织扩张技术提供了实验依据     

Vasodilatory capacity of the skin in venous disease and its relationship to transcutaneous oxygen tension.

Low transcutaneous oxygen tension (Ptc,O2) values in the supramalleolar skin of patients with venous disease are often reported. This measurement involves heating the skin to 43 degrees C to cause maximum vasodilatation and is valid only if liposclerotic and normal skin can vasodilate to the same degree. Forty-four limbs were studied, 15 with lipodermatosclerosis (LDS), 14 with uncomplicated varicose veins, and 15 controls. A Ptc,O2 electrode was modified to incorporate a laser Doppler probe. Laser Doppler flux was measured in the supramalleolar skin before and after local heating to 43 degrees C and the relative increase in flux was measured. The Ptc,O2 was then measured at the same site and on the chest. Vasodilatory capacity was expressed as the ratio of peak:basal laser Doppler flow, and the Ptc,O2 was expressed as a leg:chest ratio. Median laser Doppler flow was higher in limbs with LDS (median 67 mV) than in normal limbs (median 40 mV) (P less than 0.03). Ptc,O2 was higher in control limbs (median ratio 0.94) than in limbs with LDS (median 0.53) (P less than 0.006). The microcirculation in LDS had less capacity to vasodilate after heating (median factor of increase 5.4) than normal skin (median factor of increase 12.3) (P less than 0.001). A simple regression analysis was performed on all pairs of data, and revealed a correlation between Ptc,O2 and vasodilatory capacity (r = 0.524, P less than 0.001). The results indicate that low Ptc,O2 levels in venous disease reflect an inability of the microcirculation to increase its flow in response to local heating; inferences about the oxygen content of liposclerotic skin at normal temperatures cannot be drawn using this technique.     

The acute effect of cigarette smoking on the microcirculation of a replanted digit.

Thirty-one patients who had undergone digital replantation or revascularization volunteered to participate in a study of the acute effect of smoking on the microcirculation of the skin of replanted fingers. Fourteen were smokers and 17 were nonsmokers at the time of the study. Blood flow was assessed by means of the laser Doppler flowmeter under standard conditions. Each smoker inhaled 2 cigarettes. During smoking of the first and second cigarettes a mean decrease in laser Doppler flow of 8% and 19%, respectively, was found, whereas the nonsmokers showed a slight increase of 4% and 4%, respectively. Ten minutes after the last cigarette almost no recovery could be detected. The negative effect of smoking on the microcirculation in replanted digits proved to be more pronounced in the patients operated on more recently. This experiment confirms that smoking after replantation surgery should be prohibited to guarantee optimal circulation.     

超常量扩张促进皮肤软组织扩张器内利多卡因的渗透作用

目的：探讨超常量扩张对皮肤软组织扩张器内利多卡因的渗透作用。方法：实验分为常量扩张组和超常量扩张组，注入2％的盐酸利多卡因后将扩张囊置入生理盐水中，分别于2，8、24h取样，用高效液相色谱仪测定囊外的药物浓度。结果：扩张器对利多卡因有渗透作用，超常量扩张组各个时间点渗透到扩张囊外的利多卡因浓度大于常量组。结论：超常量扩张可增加利多卡因的渗透性，在患者注水过程中可减轻疼痛。     

Detecting arterial and venous obstruction in flaps

Island skin flaps based on the latissimus dorsi muscle were raised in domestic pigs. Flap circulation, maintained only by the vascular pedicle, was monitored by laser Doppler flowmetry, laser photometry, and transcutaneously measured carbon dioxide tension. Both arterial and venous occlusion were accompanied by very low laser Doppler flow values. In laser photometry, the backscattered intensity of light remained unchanged or was slightly increased during arterial occlusion. In response to venous occlusion, however, the light intensity decreased markedly. Transcutaneous carbon dioxide tension increased in both venous and arterial occlusion. When venous outflow pressure was raised incrementally, both the laser Doppler flow value and the total backscattered light intensity fell proportionately. Laser Doppler flowmetry might thus be useful clinically to detect decreased blood flow in transferred flaps, and laser photometry may determine if the decreased flow is related to the arterial or venous side.     

Circulation in the breast after radiotherapy and breast conservation.

OBJECTIVE: To investigate the breast circulation after radiotherapy and breast conservation. DESIGN: Open clinical study. SETTING: University hospital, Sweden. SUBJECTS: 24 patients with breast cancer (mean age 54 years, range 41-64). INTERVENTIONS: The glandular and the subcutaneous circulation in the breast were measured by Xenon (133Xe) clearance and the skin circulation by laser Doppler fluxmetry (LDF) two to five years after radiotherapy (50 Gy) following lumpectomy. The subcutaneous circulation was measured 2 cm above and medial or lateral to the areolar border and the glandular circulation 2 cm below and medial or lateral to the areolar border in the quadrant not previously operated on for carcinoma. The skin circulation was measured at the corresponding sites. MAIN OUTCOME MEASURES: Circulation in the subcutaneous and glandular tissue measured by 133Xe clearance and in the skin by LDF. RESULTS: The subcutaneous circulation, expressed as the ratio of 133Xe clearance in the operated irradiated: non-operated non-irradiated breast, was 0.88 (0.94) (median, interquartile range) and the glandular circulation 0.93 (0.75). The skin circulation ratios over the corresponding areas were 1.00 (0.37) and 1.00 (0.38), respectively. CONCLUSION: Radiotherapy after breast conservation surgery does not lead to long-term changes in basal glandular, subcutaneous, or skin circulation in the breast.     

Estimation of amputation level with a laser Doppler flowmeter

Leg amputation levels were decided in 24 patients suffering from atherosclerosis, using the conventional techniques of segmental blood pressure and radioisotope skin clearance. The skin microcirculation was measured and recorded before operation with a laser doppler flowmeter. A high correlation was found between the successful amputation levels and the maximal blood perfusion of the skin measured in this way.