Detecting changes of arterial and venous blood flow in flaps

Island skin flaps based on the latissimus dorsi muscle were raised in domestic pigs. Simultaneous recordings of laser Doppler flowmetric and laser photometric values were made on the skin in the middle of the flap. Occlusion of either the artery or the vein of the pedicle was accompanied by very low laser Doppler flow values. In laser photometry the total intensity of backscattered light remained unchanged or was sightly increased during arterial occlusion. In response to venous occlusion, however, it decreased markedly. As venous outflow pressure was increased step by step, both the laser Doppler flow value and the laser photometry value fell proportionally; thus, the greater the increase in pressure the lower were the steady state levels of both variables. Stepwise reductions of arterial inflow pressure were followed by proportional decreases in both mean blood volume flow, recorded using electromagnetic flowmetry, and in laser Doppler flowmetric values. However, laser photometric values varied only minimally. Laser Doppler flowmetry thus might be a useful clinical aid in detecting decreased blood flow in transferred flaps, and laser photometry may determine whether the decreased flow is due to arterial or venous causes.     

Circulatory and renal effects of triglycyl-lysine-vasopressin and excision in experimental burns

The circulatory and renal effects of a deep dermal burn, covering one third of the total body surface area were studied in 12 thiopentone/N2O anesthetized piglets. Central circulation and renal function was monitored during 24 h and regional blood flows were determined before burn, 5 and 24 h after burn using radioactively labeled microspheres. One group was treated conservatively with fluid infusion only (control group) and the other with fluids, intermittent injections of a long-acting hormonogen, triglycyl-lysine-vasopressin (TGLVP), and excision 5 h after burn. There was earlier circulatory recovery in the TGLVP excision group with significantly higher arterial blood pressure and cardiac output than in the controls. TGLVP induced a major redistribution of blood flows, favoring the liver at the expense of the gastrointestinal tract, carcass and skin, while the blood flows were unchanged to the brain, heart and kidneys. There were also increased excretions of sodium and potassium and a temporarily increased diuresis. The earlier circulatory stabilization and blood flow redistribution might have clinical implications in burn care.     

Reduction of blood loss by triglycyl-lysine-vasopressin during early excision of burns in pigs

In a burn model using anesthetized piglets, the circulatory and renal effects and the blood loss during and after excision were compared in two groups, one treated by triglycyl-lysine-vasopressin (TGLVP) given as intermittent bolus injections and the other serving as control. The third degree burn covered approximately 33% of the body surface area, and a solution containing 100 mmol NaCl/l in 2.5% glucose was infused at a rate of 2.4 ml/kg/% burn. Regional blood flows were determined before burn, 5 and 24 h after burn with the aid of radioactively labeled microspheres. Cardiac output (CO) decreased about 30% after burn and there was a slight further decrease of CO after the first TGLVP dose. After the excision there were similar restitutions of CO in the two groups. TGLVP induced an increase of blood flow to the hepatic artery, did not change flows to the brain, heart and kidneys and decreased flows to the preportal organs, carcass and skin 5 h after burn. After 24 h the perfusion of the skin and pancreas remained low but there were no differences in other organs. There was a significant decrease of blood loss associated with burn excision performed 5 h after burn in the TGLVP treated group, mean blood loss 39 g/25 kg versus 145 g/25 kg in the control group. There was a temporary increase in diuresis following TGLVP and also increased excretions of sodium and potassium. The results obtained in this study and possible clinical applications are discussed.     

Methodologies,Devices, and New Surgical Concepts: A Device for Noninvasive Assessment of Perfusion Pressure in the Skin of Healthy Volunteers

A device allowing pressure to be applied to a local skin site where the skin blood flow is followed using laser Doppler flowmetry is described. The blood flow was studied on the buck of the hand in eight volunteers before and during brachial arterial occlusion and while the external pressure was increased step by step. The flowmetry value during arterial occlusion was 0.3 ± 0.1 AU. and when the external pressure was increased to 120 mm Hg the values was similar (p =. 44). The shin perfusion pressure, defined as the least external pressure needed to achieve flow cessation, was found to be 92 ± 16 mm Hg (range 70–111 mm Hg), and the mean arterial pressure was 90 ± 9 mm Hg (NS). The skin perfusion value is in agreement with that found by others using other techniques for measuring blood flow and a circumferent cuff for applying pressure.     

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.     

A device for noninvasive assessment of perfusion pressure in the skin of healthy volunteers

A device allowing pressure to be applied to a local skin site where the skin blood flow is followed using laser Doppler flowmetry is described. The blood flow was studied on the back of the hand in eight volunteers before and during brachial arterial occlusion and while the external pressure was increased step by step. The flowmetry value during arterial occlusion was 0.3 +/- 0.1 AU, and when the external pressure was increased to 120 mm Hg the values were similar (p = .44). The skin perfusion pressure, defined as the least external pressure needed to achieve flow cessation, was found to be 92 +/- 16 mm Hg (range 70-111 mm Hg), and the mean arterial pressure was 90 +/- 9 mm Hg (NS). The skin perfusion value is in agreement with that found by others using other techniques for measuring blood flow and a circumferent cuff for applying pressure.     

Assessment of myocardial perfusion with laser Doppler flowmetry. An experimental study on porcine heart

Laser Doppler flowmetry was applied to the arrested heart of four pigs and to the fibrillating heart of three pigs during cardiopulmonary bypass. The coronary blood flow was maintained during cardiac arrest by infusion of hyperkalemic blood into the aortic root. A significant correlation (r = 0.88, n = 52, p less than 0.001) between laser Doppler signal and coronary blood flow was found during cardiac arrest. During ventricular fibrillation after release of the aortic cross-clamp there was significant correlation (0.84, n = 38, p less than 0.01) between laser Doppler signal and extracorporeal blood flow. A residual laser Doppler signal of about 60% of the maximal value was recorded even after the bypass flow was discontinued. Laser Doppler flowmetry is concluded to permit measurement of myocardial perfusion in the arrested porcine heart. Muscular activity of the heart contributes to the output signal during ventricular fibrillation.     

Triglycyl-lysine-vasopressin or lysine-vasopressin in early excision of burns. An experimental study comparing the effects on blood loss, hemodynamics and renal function

Twelve piglets were submitted to a third degree burn covering one third of total body surface area under general anesthesia. Fluid treatment was given in amounts corresponding to 2.4 ml/kg/% burn/24 h, and hemodynamics and renal function were monitored for 24 h. Regional blood flows were determined with the aid of the radioactive microsphere technique before burn, 5 and 24 h after burn respectively. One group was treated with triglycyl-lysine-vasopressin (TGLVP) as bolus injections and the other with lysine-vasopressin (LVP) in infusion. Both groups were submitted to excision of the burned tissues after 5 h. Total blood loss was 39 +/- 9 g in the TGLVP group and 51 +/- 7 g in the LVP group (n.s.). TGLVP changed the distribution of cardiac output (CO) more than LVP did, leading to smaller blood flows to the splanchnic organs, skin and carcass while the perfusion of the brain, heart, liver and kidneys was similar after 5 h. The burn caused a 30% decrease of CO in both groups. After the first TGLVP injection there was a small further decrease in CO but after excision there were similar recoveries of CO in both groups. After 24 h the CO redistribution remained during LVP infusion, but those effects had almost vanished in the TGLVP group. Total diuresis and the glomerular filtration rate tended to be larger during LVP treatment but there was no significant difference in serum creatinine after 24 h. Thus both drugs decrease blood loss during early excision and they seem to have similar effects on circulation and renal function.(ABSTRACT TRUNCATED AT 250 WORDS)     

Laser Doppler flowmetry of focal ischaemia and reperfusion in deep brain structures in rats

Summary Monitoring cerebral blood flow during focal ischaemia and reperfusion with established techniques such as hydrogen clearance and autoradiography is difficult. Laser Doppler flowmetry is a new technique, it allows one to continuously measure blood flow in small tissue samples. The objective of this study was to compare laser Doppler flowmetry with hydrogen clearance using a new single fiber probe to obtain measurements in deep brain structures and then to show the temporal profile of cerebral blood flow during focal ischaemia and after reperfusion.First, the single fiber laser Doppler method was compared with the hydrogen clearance method in ten Wistar rats.Second, focal cerebral ischaemia was induced in fifteen Wistar rats using a model of middle cerebral artery occlusion based on the intravascular insertion of a nylon suture; reperfusion occurred after withdrawal of the suture. The laser Doppler probe was placed in the lateral caudatoputamen, and local cerebral blood flow was measured continuously before and during occlusion as well as after reperfusion.The relative blood flow values obtained by the laser Doppler method and the hydrogen clearance method showed a good correlation (r=0.76) and a linear relationship. A rapid decrease in laser Doppler flowmetry to 42±16% of former baseline values was seen with occlusion of the middle cerebral artery; during occlusion cerebral blood flow remained at this level. Reperfusion resulted in a heterogeneous pattern of cerebral blood flow as laser Doppler flowmetry values ranged from 25% to 134% of baseline values.The effects of middle cerebral artery occlusion and reperfusion on cerebral blood flow can be monitored on-line with laser Doppler flowmetry. Our findings suggest that this method, with the high spatial and temporal resolution characteristics of its new single fiber probe, allows one to continuously measure microcirculatory blood flow in deep brain structures.Supported in part by the Deutsche Forschungsgemeinschaft (Ku 294/18-1) and by Schering AG, Berlin, Federal Republic of Germany.     

The Effect of Spinal Analgesia on Skin Blood Flow, Evaluated by Laser Doppler Flowmetry

Changes in skin blood flow provoked by spinal analgesia were evaluated by laser Doppler flowmetry. This method permits a continuous and noninvasive measurement of the microvascular flow in the superficial skin layer. All recordings were made under control environmental conditions on 40 patients submitted to transurethral resection. During spinal analgesia a significant (P less than 0.001) reduction in skin blood flow was obtained in the shoulder and chest, while an increase (P less than 0.001) in skin blood flow was seen in the lower part of the body. In the postoperative period these changes still persisted, although they were less significant, indicating the individual duration of analgesia. The relations between intra-individual relative changes in skin blood flow and skin temperature during spinal analgesia were found to be virtually uncorrelated. Laser Doppler flowmetry seems to be a useful tool in the further evaluation of the influence of spinal analgesia on the extent of the associated sympathetic blockade.     

Assessment of the physiological importance of iliac artery stenosis by laser Doppler flowmetry in pigs.

OBJECTIVE--To test the hypothesis that a curve with two peak values (double hump) recorded by laser Doppler flowmetry over the skin of the lower limb during postocclusive hyperaemia reflects pathological vascular resistance in the aortoiliac segment. DESIGN--Open study. MATERIAL--Six Norwegian Landrace pigs. INTERVENTION--Arterial stenoses were induced in the external iliac arteries. MAIN OUTCOME MEASURES--Presence of double humped laser Doppler curves, relative decrease in laser Doppler flux between the two peaks, and time taken to reach peak hyperaemic flux. RESULTS--Double humped curves were seen only when arterial stenoses were present. The relative decrease in laser Doppler flux between the two peaks, and the time to reach peak hyperaemic flux were related to the blood pressure gradient (mmHg) at the stenosis (r = 0.88 and 0.83, p less than 0.0001). The laser Doppler curve pattern can be explained by similar dynamic changes in arterial blood pressure distal to the tourniquet during hyperaemia. CONCLUSION--These results confirm the hypothesis, and suggest that laser Doppler flowmetry recordings of postocclusive hyperaemia may be a non-invasive way of assessing the condition of the iliac artery.     

Effects of Sodium Nitroprusside and Phenylephrine on Blood Flow in Free Musculocutaneous Flaps during General Anesthesia

Background: Hypoperfusion and necrosis in free flaps used to correct tissue defects remain important clinical problems. The authors studied the effects of two vasoactive drugs, sodium nitroprusside and phenylephrine, which are used frequently in anesthetic practice, on total blood flow and microcirculatory flow in free musculocutaneous flaps during general anesthesia.

Methods: In a porcine model (n = 9) in which clinical conditions for anesthesia and microvascular surgery were simulated, latissimus dorsi free flaps were transferred to the lower extremity. Total blood flow in the flaps was measured using ultrasound flowmetry and microcirculatory flow was measured using laser Doppler flowmetry. The effects of sodium nitroprusside and phenylephrine were studied during local infusion through the feeding artery of the flap and during systemic administration.

Results: Systemic sodium nitroprusside caused a 30% decrease in mean arterial pressure, but cardiac output did not change. The total flow in the flap decreased by 40% (P < 0.01), and microcirculatory flow decreased by 23% in the skin (P < 0.01) and by 30% in the muscle (P < 0.01) of the flap. Sodium nitroprusside infused locally into the flap artery increased the total flap flow by 20% (P < 0.01). Systemic phenylephrine caused a 30% increase in mean arterial pressure, whereas heart rate, cardiac output, and flap blood flow did not change. Local phenylephrine caused a 30% decrease (P < 0.01) in the total flap flow.     

Power spectral analysis of the effects of epinephrine,norepinephrine, dobutamine and dopexamine on microcirculation following free tissue transfer

Background: The use of pressor drugs after microsurgical free tissue transfer remains controversial because of potential vasoconstrictor effects on the free flap. Noninvasive monitoring of free flaps with laser Doppler flowmetry may provide further information regarding the local regulation of blood flow in the flap tissues during pressor infusions. This study evaluated the effects of four commonly used pressor agents. Methods: Twenty four patients (25 data sets) undergoing head and neck cancer resection and free flap reconstruction were recruited. Epinephrine, norepinephrine, dopexamine, and dobutamine were infused in a random order at four infusion rates, after surgery, with free flap and control area (deltoid region) laser Doppler skin blood flow monitoring. Frequency analysis of the Doppler waveform was performed utilizing the time period immediately before the first drug infusion for each patient as baseline. Results: At baseline there was less power at the 0.002–0.6 Hz frequency in the flap compared with control tissue consistent with surgical denervation. At maximum epinephrine infusion rates, the control of blood flow moved toward (i.e., proportion of power increased in) the lower frequencies, as smooth muscle mediated (myogenic) control began to dominate blood flow, an effect most marked with norepinephrine. Dobutamine and dopexamine had little effect on control of blood flow. Conclusions: Denervation of free flap tissue is demonstrable using spectral analysis of laser Doppler blood flow signals. With norepinephrine the control of blood flow shifts toward low frequency vasomotion where blood flow depends mostly on average blood pressure, making it potentially the most suitable agent following free tissue transfer. © 2013 Wiley Periodicals, Inc. Microsurgery, 2013.     

Assessment of blood flow through the lung using laser Doppler flowmetry

The value of laser Doppler flowmetry in measuring blood flow through the lung was assessed comparing it with flow measured by electromagnetic flowmetry. This was an experimental laboratory-based prospective study performed in an approved University animal research facility. Ten beagle dogs were used. Simultaneous measurement of pulmonary blood flow by laser Doppler flowmetry and electromagnetic flowmetry was carried out at varying degrees of pulmonary artery constriction. There was a linear relationship between the two methods of assessing blood flow (regression equation: y = 0.9x + 5.5; p = .00001) using a least-squares, best fit, straight line analysis (160 data points). The results of this study demonstrate that laser Doppler flowmetry provides an accurate indicator of pulmonary blood flow, which in practice is both simple and reproducible.     

Assessment of Blood Flow Through the Lung Using Laser Doppler Flowmetry

The value of laser Doppler flowmetry in measuring blood flow through the lung was assessed comparing it with flow measured by electromagnetic flowmetry. This was an experimental laboratory-based prospective study performed in an approved University animal research facility. Ten beagle dogs were used. Simultaneous measurement of pulmonary blood flow by laser Doppler flowmetry and electromagnetic flowmetry was carried out at varying degrees of pulmonary artery constriction. There was a linear relationship between the two methods of assessing blood flow (regression equation: y= 0.9 x + 5.5; p=. 00001) using a least-squares, best fit, straight line analysis (160 data points). The results of this study demonstrate that laser Doppler flowmetry provides an accurate indicator of pulmonary blood flow, which in practice is both simple and reproducible.     

应用激光多普勒血流仪对大鼠后肢缺血模型血流动力学的观察

目的应用激光多普勒血流探测仪(LDF)和激光多普勒血流成像仪(LDPI)监测Lewis大鼠后肢急性缺血模型血流和血压的动态变化,探讨大鼠后肢急性缺血后血流变化特点。方法切除大鼠左后肢股动脉制备急性后肢缺血模型,于术后2、7、14、28及49 d对手术侧和非手术侧肢体采用LDF进行血流、血压检测,于术后7 d采用LDPI进行血流检测。结果所有大鼠术后均成活,未发现后肢坏死;在术后14 d内手术侧后肢平均分为2分,在49 d平均分为1分。大鼠手术侧和非手术侧肢体血流比值在术后2 d由术前的1上升至1.31±0.439(P=0.021),术后7 d和14 d分别为0.82±0.538和0.93±0.294,两者比较差异无统计学意义(P=0.502),但均明显低于术后2 d的值(P=0.032和P=0.019);术后28 d下降到最低点(0.41±1.970),明显低于术后2、7和14 d值(P=0.004、P=0.007和P=0.006);在术后49 d手术侧后肢血流恢复到接近术前值(0.98±0.093),明显低于术后2 d(P=0.010)而高于术后28 d值(P=0.005),与术后7 d和14 d的差异无统计学意义(P=0.126和P=0.382)。大鼠手术侧和非手术侧肢体血压比值术后2 d由术前的1明显下降至0.47±0.375(P=0.031);术后7 d继续下降至0.44±0.118,与术后2 d比较差异无统计学意义(P=0.203);术后14 d下降到最低点(0.35±0.115),明显低于术后2 d和7 d值(P=0.001和P=0.036);术后28 d开始上升(0.54±0.146),明显高于术后14 d值(P=0.008),但与术后2 d(P=0.493)和7 d(P=0.551)的差异无统计学意义;术后49 d恢复接近术前值(0.97±0.094),明显高于术后2、7、14和28 d值(P=0.013、P=0.021、P=0.002和P=0.031)。结论切除大鼠后肢股动脉及分支的方法制备后肢急性缺血模型,在术后14~28 d患肢缺血处于最严重阶段。LDF和LDPI可以动态监测肢体血流及血压的变化,对监测大鼠后肢术后缺血的动态演变过程有着重要的作用。     

Assessment of gastrointestinal blood flow with laser Doppler flowmetry in patients with chronic radiation injury

Laser Doppler flowmetry was used for pre- and intraoperative assessment of gastrointestinal blood flow and vascular damage in eight patients with late radiation injury of the gastrointestinal tract. The flowmeter recordings were compared with reference values previously obtained in unaffected tissue from corresponding gastrointestinal sites. Marked reduction of blood flow was demonstrated in macroscopic areas of radiation injury in all eight patients. Five also showed varying degrees of disturbed blood flow in adjacent macroscopically normal bowel segments with histologically varying severity of radiation injury. In a ninth patient radiation injury was clinically suspected but could not be demonstrated with laser Doppler flowmetry or histologically. The extent of radiation injury often is underestimated from clinical signs, and laser Doppler flowmetry during surgical treatment of late radiation injury to the gastrointestinal tract provides substantial information concerning the extent of vascular damage.     

Measurement of impotence by laser Doppler flowmetry and conventional methodology

The problem of vasculogenic impotence was evaluated by laser Doppler flowmetry with the LD5000 capillary perfusion monitor to determine cutaneous penile blood flow in 25 men defined previously as impotent by Doppler ultrasound with penile brachial ratios of 0.63 +/- 0.14. Erotic visual stimulation for 1, 2 and 4 minutes did not statistically change the cutaneous flow as measured by laser Doppler flowmetry from its baseline of 20 mv. The dynamics of skin microcirculation in the penis may reflect changes in the deeper vessels and represent an alternate, dependable method to evaluate capillary perfusion.     

Early decrease of skin blood flow in response to locally applied pressure in diabetic subjects

Pressure ulcers are common debilitating complications of diabetes that are caused by tissue ischemia. Skin blood flow in response to locally applied pressure might be impaired in diabetic patients because of the combined effects of a typically low skin temperature and alterations in microcirculatory function, and could be worsened by neuropathy. We measured skin blood flow by laser Doppler flowmetry over the internal anklebone in response to local pressure applied at 5.0 mmHg/min in three groups of diabetic patients (with clinical and subclinical neuropathy and without neuropathy) and in healthy matched control subjects at usual room temperature. Compared with in matched control subjects with comparable skin temperatures (29.3 +/- 0.4 vs. 28.7 +/- 0.4 degrees C), in diabetic patients the skin blood flow response to locally applied pressure was further impeded, even in those without neuropathy. Indeed, skin blood flow decreased significantly from baseline at much lower applied pressure (7.5 mmHg) in diabetic subjects, again even in those without neuropathy, than in control subjects (48.8 mmHg). The large difference between these pressures could partially explain diabetic patients' high risk of developing decubitus and plantar ulcers.     

The diabetic foot and leg: combined He-Ne and infrared low-intensity lasers improve skin blood perfusion and prevent potential complications. A prospective study on 30 Egyptian patients

The objective of this study was to examine skin blood flow in diabetic patients having disease-related skin lesions, and to evaluate possible improvement imposed by low-intensity laser therapy (LILT) as a new treatment modality. Thirty patients (in addition to 15 controls receiving conventional treatment = group II and 15 others receiving no treatment = group III) having diabetes-related skin lesions were tested for skin blood flow by laser Doppler flowmetry. Group I patients received LILT by a specified dosimetry. This was by combined uniform He-Ne and infrared lasers delivered by a scanner over the affected area. This study used a paired t test to determine the significance of blood flow recovery after treatment within each group while Independent t test compared results between the three groups. The level of significance was p < 0.05. The most frequently detected diabetes specific skin lesions were dryness, nail changes, hair loss, infections, itching, and frank eczema-like reactions, mostly in combinations (76%). This pattern appears specific for Egyptians as it is different from data registered in foreign literature. The minimum perfusion flow improved from 16.45 before LILT to 25.94 after, while maximum flow recovered from 32.91 to 48.47 and basal perfusion changed from 24.68 to 34.84 blood perfusion units. The percentage change in perfusion values was 23.17. All these were statistically significant. The study demonstrates that diabetes-linked skin lesions have a special pattern in Egyptians and are apparently caused by deranged skin blood flow .The deficit is measurable by laser flowmetry and can be partially reversed by LILT.